Fractal Audio Wiki - User contributions [en]

Amp models list

2024-01-12T03:42:34Z

James-F: /* BRIT 800 2204 HIGH (50W Marshall JCM 800 2204) */

This page lists all amp models in Fractal Audio’s current generation of guitar processors, with brief additional information (based on [[Amp_modeling_techniques | Cygnus amp modeling]]). Depending on the firmware, some models may not be available on every device. Fractal Audio owns almost all amps on which models are based. [https://thegearforum.com/threads/fractal-audio-firmware-update-thread.673/page-54#post-46151] Many amp models are featured in [[Factory presets]]. [[Yeks_Guide_to_the_Fractal_Audio_Amp_Models | Yek's Guide to the Fractal Audio Amplifier Models provides in-depth information about many amp models]]

__TOC__

==1959SLP JUMPED (100W Marshall Super Lead Plexi 1959 reissue)==

[[file:SLP.png|300px]]

Models:
* Normal and Treble channels jumpered
* Normal channel
* Treble (High) channel

[[Cabinet models list| Cab:]] Marshall 4x12 (G12M, G12H)

Volume Normal, Volume Treble, Bass, Middle, Treble, Presence

Power tubes: EL34

# (about the Plexi model in the Standard/Ultra): "One of the first mods people make to real 'Plexi' Marshalls is to "clip the bright cap". The bright cap varied over the years, supposedly depending on what was lying around in the shop. The model defaults to the bright cap in the circuit. If you turn off Bright you're effectively clipping the bright cap. The bright cap in Marshalls can be very bright and harsh. However, if you crank the Master you might find the extra brightness helps compensate for the power amp getting darker."
# (about fizz) "It's the way a Plexi is supposed to sound. That's due to the cathode follower. That raspiness helps it cut through in a mix. I own three of them and they are that fizzy." [https://forum.fractalaudio.com/threads/high-end-fizz-is-this-normal.43598/#post-576475]
# "Don't be afraid to turn the bass all the way down or the treble all the way up. Just like with the actual amp. For example, on the normal channel of a Plexi most people turn the bass way down. Otherwise it's too flubby."
# "The old one (Plexi 100w model) has a 2.7K cathode resistor on the first stage, the new one (1959SLP) has an 820 ohm." [https://forum.fractalaudio.com/posts/1111403]
# "I based the SLP on using it with G12H(55) speakers which have a resonance of 55 Hz. When mounted in a typical cab the resonance will be in the low 70s. There is no right or wrong. Whatever sounds best." [https://forum.fractalaudio.com/posts/1159759]
# "My settings for a "typical" Plexi tone are Bass: 2, Mid: 8, Treble 7.5. Adjust Presence to taste." [https://forum.fractalaudio.com/posts/1179420]
# "What you are hearing is output transformer high frequency resonance. Old Plexis didn't do this because they had good transformers. New transformers are crappy and resonate at the cutoff frequency because they are underdamped. This causes a raspy, fizzy texture to the distortion. The transformer resonance is adjustable but the parameter isn't exposed to the user. When you turn it up you get that same squishy rasp that you are hearing. For the Plexis I have the damping set to flat with no resonance because that's how our vintage Plexis measure. Our 50W is a little underdamped but people complain about raspy high frequencies so I erred on the safe side." [http://forum.fractalaudio.com/threads/dimed-real-plexi-vs-dimed-simulation-q8-01.127161/page-2#post-1513888]
# "When modding Marshalls for higher gain sometimes the modder will decrease the input frequency response to reduce noise and fizziness. You can do this by reducing the high-cut frequency in the input EQ. Or you can use a high-shelf filter which is a little more subtle. Another technique is to put a capacitor across the second-to-last triode stage. This is the "Triode 1 Plate Freq" parameter. Reduce this to around 2 kHz to start which is typical of amps like an SLO100, etc." [https://forum.fractalaudio.com/threads/dialling-in-the-marshalls.143682/post-1707222]
# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]
# [[Amp_block#NEGATIVE_FEEDBACK|Negative feedback value]]
# A bug in the model's tonestack was fixed in firmware 23.03.

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-1959slp-marshall-slp1959.111321/ Yek's write-up]

==1959SLP NORMAL==

# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]

==1959SLP TREBLE==

# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]

==1987X JUMPED (50W Marshall 1987X reissue) ==

[[file:1987X.png|300px]]

Models:
* Normal and Treble channels jumpered
* Normal channel
* Treble channel

[[Cabinet models list | Cab:]] Marshall 4x12 (G12M, G12H)

Volume Normal, Volume Treble, Bass, Middle, Treble, Presence

Notes: see 1959SLP

Power tubes: EL34

# "The 1987x doesn't have the 0.68uF cap on the last triode. Gives it a smoother distortion." [https://forum.fractalaudio.com/posts/1000388]
# "Our reference amp has no bright cap. Looks like it was that way from the factory. There are no signs it was removed. The location in the circuit board is empty and the solder joints do not appear to have been disturbed." [https://forum.fractalaudio.com/threads/1987x-bright-switch-off-by-default.145332/post-1718899]
# [[Amp_block#NEGATIVE_FEEDBACK|Negative feedback value]]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-1987x.111362/ Yek's write-up]

==1987X NORMAL==

==1987X TREBLE==

==5153 100W BLUE (EVH 5150-III)==

[[File:5153.png|300px]]

Models:
* 100W amp, Blue channel
* 100W amp, Green channel
* 100W amp, Red channel
* 100W Stealth amp, Blue channel
* 100W Stealth amp, Green channel
* 100W Stealth amp, Red channel
* 50W amp, Blue channel

[[Cabinet models list| Cab:]] 5150 4x12 or 2x12 (G12H, G12EVH)

Gain, Low, Mid, High, Volume, Presence, Resonance (only on 50w model)

Power tubes: 6L6

# "IMO, it's a very good amp. The build-quality is great and the design is very good. It is similar to the previous versions but voiced a bit different. Personally, I think all of the 5150's have more gain stages than necessary which just makes for unnecessary failure points but the "OMG, this amp has sooo many toobz it must sound awesome" marketing makes it understandable. It's incredibly heavy though." [https://forum.fractalaudio.com/posts/679483]
# "A 5150 uses a fixed bias with no adjustment. Depending on the tubes used the bias can run from average to cold. The model uses average. Some people like a colder sound. If you prefer your amps biased cold, then reduce the bias parameter to taste." [https://forum.fractalaudio.com/posts/742231]
# "The 50W version has a different input network than the 100W version for that channel. The 50W version has about twice the gain as a result. Otherwise things are pretty similar. You can simulate this using the Input Trim knob." [https://forum.fractalaudio.com/posts/1042144]
# "The red channels (of 50w and 100w models) are identical." [http://forum.fractalaudio.com/threads/5153-50w-blue-red.106463/#post-1273739]
# "Some amps have a fixed depth circuit, e.g. 5153, Freidman BE/HBE, Dirty Shirley, TripTik, Tucana, et. al. In these cases the Depth knob will default to a value that corresponds to the fixed circuit." [https://forum.fractalaudio.com/threads/lets-talk-about-the-depth-control.88747/#post-1071598]
# "The 5150 models are absolutely identical to our reference amp." [https://forum.fractalaudio.com/threads/legacy-amp-models-consider-revisiting-full-honest-request-and-opinion.160349/post-1919792]
# "The Normal Gain input has a very low input impedance, about 44K in addition to cutting the gain in half. Use the Input Impedance feature of the Input block to simulate. Try 32K." [https://forum.fractalaudio.com/threads/why-fractal-is-good-for-my-sanity-and-my-wallet.167246/post-2008937]
# "Another technique is to use negative feedback to the grid. This is done in 5150-based designs which makes the stage clip even harder. The last stage of a 5150 basically looks like a diode clipper. The harder the clipping the more overtones that are created and the better the tone cuts. Without those overtones your sound is lost in the mix." [http://forum.fractalaudio.com/threads/fizz-is-good.67719/#post-833875] </blockquote>
# "A 5150's presence control has almost no effect from 0 to 7. After 7 the treble increases rapidly. The taper of the presence control in a 5150 is a log30 IIRC (maybe log10, I'd have to check my notes). If anything it should be linear. Ideally it should be reverse log. Our model uses a reverse log taper which gives a nice, smooth response over the full range. In most cases a reverse log taper would be the ideal taper. However reverse log taper pots are uncommon, difficult to source and cost more. Why they chose a log taper in the 5150 is a mystery. Since the power amp has similarities to a Marshall perhaps Eddie wanted the presence control to behave like his old Marshalls. Another possibility is the designer felt the amp was too bright with all knobs at noon (and a linear taper presence pot) and changed the taper to reduce the brightness." [https://www.thegearpage.net/board/index.php?threads/blind-test-mesa-dual-rectifier-vs-mystery-modeler-update-results-revealed.2208367/post-31639265]
# "Amps with low amounts of negative feedback in the bass region are sensitive to the impedance curve. The 5153 is one of these amps due to its NFB circuit." [https://thegearforum.com/threads/evh-amp-vs-axe-fx-qc-and-tmp.3593/post-133163]
# (about bias) "Rev. D of the schematic which was Jan. 15 2013 specs 30mA per tube. This was changed to 27.5 mA per tube somewhere between then and Dec. 11 2015. There apparently haven't been any changes to that spec since. So in the past 10 years every amp shipped has been at least 27.5 mA." [https://forum.fractalaudio.com/threads/5150-presence-knob.199908/page-5#post-2492348]
# (firmware 23.05) "Changed Presence control taper on all 6160 and 5153 amp models to replicate the actual amp. It is advised to audition any presets that use these models and adjust accordingly."

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-5153-evh-5150-iii.111404/ Yek's write-up]

==5153 50W BLUE==

==5153 100W GREEN==

==5153 100W RED==

==5153 100W STEALTH BLUE (EVH 5150III 100S 100W)==

[[File:5153S.jpg|300px]]

# "The Blue channel gain knob affects the Red channel somewhat. I modeled it with the Blue channel gain knob at noon." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-23-04-release.199875/post-2491407]
# "The Red channel has much more gain but the Gain pot taper is very different. The Red channel has a 5A taper, while the Blue channel has a 30A taper so at noon it will appear as though the Blue channel has more gain." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-23-04-release.199875/post-2491406]
# "Every channel in the 100S is different than the OG 5153." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-23-04-release.199875/page-9#post-2492343]
# "The 100S Red channel has about three times the gain as the OG. The Blue channel has about 2.5 times more gain. The Green channel has over five times the gain." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-23-04-release.199875/page-10#post-2492792]

==5153 100W STEALTH GREEN==

==5153 100W STEALTH RED==

==59 BASSGUY BRIGHT (1959 Fender narrow-panel Tweed Bassman, 5F6-A)==

[[file:bassman.jpg|300px]]

Models:
* Bright channel
* Normal channel
* Jumpered channels

[[Cabinet models list | Cab:]] Fender 4x10 with Jensen Alnico 25W P10R or 40W P10Q

Volume Normal, Volume Bright, Bass, Middle, Treble, Presence

Power tubes: 6L6/5881

# [before 19.02 for the Axe-Fx III] "There is no "High" channel on a 59 Bassman. There is a Normal and Bright channel. The Bright channel model is selected by turning on the Bright switch. The models are based on the higher gain input (the "1" input). To simulate the lower gain input simply set Input Trim to 0.5." [https://forum.fractalaudio.com/posts/1109139/]
# [19.02 and later for the Axe-Fx III] "Updated 59 Bassguy and 5F8 Tweed models to include both Drive controls."
# "All the Fender models except the 59 Bassman and 5F8 Tweed don't have cathode followers." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-00-beta-3.148907/page-3#post-1764588]
# ("Cygnus" amp modeling) "The Bassman was reworked using an original 59 Bassman 5F6-A as a reference. This has a 12AY7 input buffer which has less gain than the reissue which uses a 12AX7A (7025 actually, same thing)."
# ("Cygnus" amp modeling) "The Bassman and Deluxe Tweed models are both modeled using a 12AY7 as the input buffer. The Preamp Tube Type parameter only affects the tubes after the input buffer." [https://forum.fractalaudio.com/threads/12ay7-preamp-tube-for-tweed-deluxe-and-bassman-models.175834/post-2135435]
# "The input to the second 12AX7 is a summing node. Both volume controls affect the signal. If you plug into the Bright input the Normal volume control will also control the volume to some degree and change the frequency response." [https://forum.fractalaudio.com/threads/bassman-how-do-the-way-the-2-drive-controls-interact.181986/post-2232557]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-59-bassguy-59-fender-tweed-bassman-5f6-a.111275/ Yek's write-up]

==59 BASSGUY JUMPED==

==59 BASSGUY NORMAL==

==59 BASSGUY RI JUMPED (Fender 59 Bassman LTD Vintage Reissue)==

[[file:FENDER_BASSMAN_RI.jpg|275px]]

Model:
* Jumpered channels

[[Cabinet models list | Cab:]] Fender 4x10 with Jensen Alnico 25W P10R or 40W P10Q

Volume Normal, Volume Bright, Bass, Middle, Treble, Presence

Power tubes: 6L6

# See 59 Bassguy.
# "There are quite a few differences between a 5F6-A and the reissue: [https://forum.fractalaudio.com/threads/bassman-how-do-the-way-the-2-drive-controls-interact.181986/post-2358853]
## 12AX7A vs. 12AY7 input tube.
## Different tone stack (this is a big one).
## Different presence network.
## Different B+ voltage.
## 6L6s vs 5881s (minimal difference).

==5F1 TWEED (Fender narrow-panel Tweed Champ, 5F1)==

[[file:champ.jpg|300px]]

Model:
* Single channel

[[Cabinet models list| Cab:]] Fender 1x8

Volume

Power tubes: 6V6

# "This particular amp exhibits a unique breakup characteristic due to its single-ended design and simple circuit."

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-5f1-tweed-fender-champ.111067 Yek's write-up]

==5F1 TWEED EC (2011 Fender EC Vibro-Champ)==

[[file:EC-Vibro-Champ.jpg|300px]]

Model:
* Single channel

[[Cabinet models list| Cab:]] Fender 1x8

Volume, Tremolo

Power tubes: 6V6

# "The circuit is slightly different than the original 5F1. It has cathode bypass caps giving it more gain." [http://forum.fractalaudio.com/threads/fractal-audio-amp-models-5f1-tweed-fender-champ-5f1.111067/page-2#post-1508977]
# "It's a single-ended power amp with negative feedback and bias tremolo. Subtle is the only possibility with this configuration. Bias tremolo works by modulating the quiescent operating point of the power tubes. With a single-ended power amp with negative feedback the gain doesn't change much as you change the operating point, hence the tremolo effect is subtle. Bias tremolo works best on amps with little to no negative feedback." [https://forum.fractalaudio.com/threads/fw-q8-5f1-tweed-ec-4-scene-preset-vid-demo.126829/post-1509387]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-5f1-tweed-fender-champ.111067 Yek's write-up]

==5F8 TWEED BRIGHT (Keith Urban's 1959 Fender narrow-panel high-power "big box" Tweed Twin, 5F8)==

[[file:5f8-2.jpg|300px]]

Models:
* Bright channel
* Jumpered channel
* Normal channel

[[Cabinet models list| Cab:]] Fender 2x12 (P12N, but Keith Urban's cab has Two-Rock speakers)

Volume Bright, Volume Normal, Presence, Middle, Bass, Treble

Power tubes: 6L6

# [before firmware 19.02 for the Axe-Fx III] Engage the Bright switch for the Bright channel
# "Based on a 1959 Fender Twin Amp. This particular model is based on Keith Urban’s “#1”. Thank you Keith for allowing us the use of your prized amplifier."
# "All the Fender models except the 59 Bassman and 5F8 Tweed don't have cathode followers." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-00-beta-3.148907/page-3#post-1764588]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-5f8-tweed-keith-urbans-high-power-fender-twin-amp.111123 Yek's write-up]

==5F8 TWEED JUMPED==

==5F8 TWEED NORMAL==

==65 BASSGUY BASS (1965 Blackface Fender Bassman head, AB165)==

[[file:ab165.png|300px]]

Models:
* Bass channel
* Normal channel

[[Cabinet models list | Cab:]] Fender 2x12 (Oxford)

Volume, Bass, Treble, fixed Presence circuit (Presence should be at 10), Bright switch (Normal channel only)

Power tubes: 6L6

# "Has a pissed-off Marshall vibe to it." [http://forum.fractalaudio.com/posts/490912]
# "The 65 Bassguy was matched to a 65 Bassman that Dweezil sent me. It's a vicious amp that sounds more like a Plexi than a Fender. It's the infamous AB165 circuit which is very crunchy and bright and does not sound like your typical Fender." [https://forum.fractalaudio.com/threads/am-i-the-only-one-who-noticed-that-some-amps-have-alot-more-gain.51123/page-2#post-658833]
# "It's a crazy sounding amp, sounds nothing like your typical Fender." [https://forum.fractalaudio.com/threads/another-v10-preview.62489]
# "The AB165 uses 7025 preamp tubes (which are relabeled 12AX7). The phase inverter, however, is a 12AT7. The secret to the AB165 is the summing stage. It uses a inverting summing amp to sum the Normal and Bass inputs. This stage clips, because of all the local negative feedback, quite hard." [http://forum.fractalaudio.com/posts/

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-65-bassguy-65-blackface-fender-bassman-ab165.111298/ Yek's write-up]

==65 BASSGUY NORMAL==

==6G12 CONCERT (1960 Brownface Fender Concert, 6G12)==

[[file:6G12.jpg|300px]]

Model:
* Vibrato channel

[[Cabinet models list | Cab:]] Fender 4x10 with Jensen Alnico 25W P10R or 40W P10Q, or ceramic 25W C10R, or Oxford

Volume, Bass, Treble, Presence, Vibrato (not modeled)

Power tubes: 6L6

# "Super 6G4 is a Brownface Fender Super. Concert 6G12 is a Brownface Fender Concert. They are very similar amps and both sound "old". They definitely have that early 60's vibe to them." [https://forum.fractalaudio.com/threads/axe-fx-ii-firmware-17-02-released.93734/#post-1124507]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-6g12-concert-60-fender-brownface-concert.111224/ Yek's write-up]

==6G4 SUPER (1960 Brownface Fender Super, 6G4)==

[[file:6G4.jpg|300px]]

Model:
* Vibrato channel

[[Cabinet models list | Cab:]] Fender 2x10 with Jensen Alnico 25W P10R, 40W P10Q or Oxford 10K5, or a Fender 2x12

Volume, Bass, Treble, Presence, Vibrato (not modeled)

Power tubes: 6L6

# "Super 6G4 is a Brownface Fender Super. Concert 6G12 is a Brownface Fender Concert. They are very similar amps and both sound "old". They definitely have that early 60's vibe to them." [https://forum.fractalaudio.com/threads/axe-fx-ii-firmware-17-02-released.93734/#post-1124507]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-6g4-super-60-fender-brownface-super.111173 Yek's write-up]

==AC-20 12AX7 BASS (Morgan AC20 Deluxe)==

[[file:morgan.jpg‎|300px]]

Models:
* 12AX7 Bass
* 12AX7 Treble
* EF86 Bass
* EF86 Treble

[[Cabinet models list | Cab:]] Morgan 1x12 (G12 Alnico Blue), DynaCab available

Volume, Cut, Sun/Moon switch (= Bright switch), Brilliance switch (= Bass Cut), power scaling (not modeled), EF86/12AX7 switch

Power tubes: EL84

# "The AC-20 model is based on the amp with the power scaling at maximum power which effectively disables it (and sounds best IMO)." [https://forum.fractalaudio.com/posts/1079502]
# "The AC-20 has power scaling. The Axe-Fx II does not model the power scaling circuit as there is no point in that." [https://forum.fractalaudio.com/threads/power-level-ac-20.89488/#post-1079494]
# "As with the real amp I dial in quite a bit of Hi-Cut." [http://forum.fractalaudio.com/threads/recommend-an-amp-for-p-w.106093/#post-1268874]
# "I think an AC-20 does the Vox thing better than Vox." [https://forum.fractalaudio.com/threads/recognition-and-respect-to-cliff-and-his-morgan-ac20.155040/post-1844685]
# "AC-30's have a poorly designed cathode follower. The bias point is totally wrong and crushes one side of the signal considerably. IMO either the cathode resistor should be 100K or the plate resistor of the preceding stage should be higher, 200K. The clipping is extremely asymmetric. Too much IMO. A little asymmetry is good because it warms things up. Too much causes excessive even-order harmonics which makes things fuzzy and indistinct. The clipping is so asymmetric on an AC-30 that it's almost a half-wave rectifier. You can tweak this by adjusting the Preamp Bias point and/or lowering the Cathode Follower Compression. Or you can lower the Harmonics value which reduces the asymmetric distortion. The downside of that is that it then overdrives the phase inverter causing blocking distortion from excessive bias excursion. Another thing to try is to increase the Grid Clipping value which will add a little headroom. Start with the Bias point. AC-30's are very sensitive to the tube type and part tolerances. A tiny change in the bias point can make a big difference. The default bias point is based on Mullard ECC83 tubes. I prefer the AC-20 because it doesn't have a cathode follower so doesn't suffer from these problems. The cathode follower in an AC-30 doesn't even do all that much. Normally you use a cathode follower to preset a low-impedance source to the tone stack but the tone stack in an AC-30 doesn't present that great of a load anyways." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-02.148983/page-11#post-1767187]
# "One reason I like the AC-20 is that it runs the tubes hotter and exhibits less crossover distortion." [https://forum.fractalaudio.com/threads/papery-buzz-under-some-models.149193/page-2#post-1772639]
# "The Sun/Moon equals the Bright Switch. The Bass/Treble switch would be different amp models. So AC20 EF86 Bass model would be the Bass/Treble switch in the Bass position, the switch on the back in EF86 position and then the Bright switch on the model is the Sun/Moon switch on the amp." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-10-00.154850/post-1842330]
# "So I was testing the next beta and selected the AC-20. Was hearing a lot of ghost notes compared to the old algorithm (in the debug build I can select between algorithms with a hidden parameter) and figured that couldn't be right. Hooked up the real AC-20 and, sure enough, ghost notes galore at the same settings." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-0-public-beta.154714/post-1840850]
# "Our reference amp is a head with matching 1x12 cab." [https://forum.fractalaudio.com/threads/recognition-and-respect-to-cliff-and-his-morgan-ac20.155040/post-1844744]
# "The normal channel on a Vox would be closest to the Morgan. The Brilliant channel is a "Top Boost" which means it has a tone stack and a significant midrange cut. The normal channel has no tone stack. You can't compare a a Morgan AC20 to the Brilliant channel of an AC30 and declare that one sounds better than the other. Totally different preamps and, therefore, different sound. Personally I think the AC20 is a better amp. Better made, better quality components, much better transformers. If you want that chimey AC30 sound you put an EQ before it and suck out some mids." [https://forum.fractalaudio.com/threads/how-accurate-is-fractals-amp-modeling.168786/post-2064189]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-ac-20-morgan-ac20-deluxe.111453/ Yek's write-up]

==AC-20 12AX7 TREBLE==

==AC-20 EF86 BASS==

==AC-20 EF86 TREBLE==

==ANGLE SEVERE 1 (Engl Savage 120)==

[[File:savage.png|300px]]

Models:
* Lead channel, Contour switch OFF (boosts lower midrange around 500 Hz)
* Lead channel, Contour switch ON (boosts from 1200 Hz and cuts lower midrange)

[[Cabinet models list | Cab:]] Engl 4x12 (V30, V60)

Gain (input sensitivity), Lead (degree of distortion), Lead Boost switch, Contour switch, Bass, Middle, Treble, Rough/Smooth switch (not modeled), Master, Presence, Depth Boost switch

Power tubes: 6550

# "From noon and up it's a presence boost, from noon down it's a presence cut." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-1-03-firmware-release.106931/page-12#post-1280997]
# "(...) Engl Savage presence network which reduces negative feedback as the control is turned down causing an increase in volume." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-5-cygnus-firmware-public-beta-2.170901/post-2059273]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-angel-severe-engl-savage-120.111501/ Yek's write-up]

==ANGLE SEVERE 2==

==ARCHEAN (100W PRS Archon)==

[[File:Archon.jpg|300px]]

Models:
* Archean: Lead channel with Bright switch OFF
* Archean Bright: Lead channel with Bright switch ON
* Archean Clean: Clean channel

Master, Bass, Middle, Treble, Bright switch, Volume, Depth, Presence, Output Power (not modeled)

Power tubes: 6L6

# "You have to crank the MV on the real amp. The preamp is very "dry" so to get the juices flowing the power amp needs to be working hard. This also smooths out that funky midrange." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-14-01.165716/page-10#post-1990153]
# "I think part of the reason the real Archon needs to be cranked is because the power supply is too stiff. It's got six (!!!) big caps filtering the B+. That's too much filtering IMO unless you're playing at arena volumes. If I were to make a modification to the amp it would be a switch to disconnect four of those caps so the supply is more bouncy at moderate volumes. Maybe also a tube rectifier to add some more sponge." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-14-01.165716/page-10#post-1990169]
# Based on 100W amp [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-14-01.165716/post-1990412]

[https://forum.fractalaudio.com/threads/fractal-audio-amp-models-archean-based-on-prs-archon.165751/ Yek's write-up]

==ARCHEAN BRIGHT==

==ARCHEAN CLEAN==

==ATOMICA HIGH (Cameron Atomica)==

[[file:atomica.jpg|300px]]

Models:
* Low gain input
* High gain input

[[Cabinet models list | Cab:]] cabinet with G12H speakers

Thump, Presence, Bass, Middle, Treble, Master, Gain, Edge (not modeled), 3-way Gain Voice switch

Power tubes: EL34

# "The Atomica can tolerate high MV because it is a "Jose-style MV". The Jose-style MV imparts a very high source resistance to the tone stack which causes much more insertion loss and therefore lower drive level into the power amp." [https://forum.fractalaudio.com/posts/748843]
# "Cameron amps are basically modified Marshalls. The Atomica is essentially a slightly modified JCM800 with a Jose-style zener clipper." [https://forum.fractalaudio.com/threads/dialling-in-the-marshalls.143682/page-5#post-1706652]
# (fuzzy tone with Bright on) "That's the way those amps sound with the bright switch on. It's due to the location of the drive control. Turn down the Preamp Bias Excursion to reduce it. The problem with those "Mid Stage Drive" designs using a Plexi drive network is that if you bypass the drive pot with a cap (bright cap) you also bypass any grid stoppage and the next stage goes into blocking distortion very easily. There's essentially a straight shot into the grid for all the high frequencies. Friedman probably realized this and that's why there's no bright cap on the BE as the BE is very similar to the Atomica." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2052829]
# "The Cameron is a genuine Cameron. I don't know the lineage of the Atomica." [https://forum.fractalaudio.com/threads/are-any-of-the-cameron-models-of-mark-cameron-built-amps.199792/#post-2489827]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-atomica-cameron-atomica.111547 Yek's write-up]

==ATOMICA LOW==

==BAND-COMMANDER (1968 Silverface/Blackface Fender Bandmaster head, AB763)==

[[file:bandmaster.jpg|300px]]

Model:
* Vibrato channel

[[Cabinet models list| Cab:]] Fender 2x12

Vibrato channel: Volume, Bright switch, Treble, Bass, Tremolo

Power tubes: 6L6

# "The vibrato channel is loaded down by the vibrato circuit. The normal channel isn't. You can probably get close using the vibrato channel model by increasing the MV trim." [http://forum.fractalaudio.com/threads/maroon-5-axe-fx-iii-awesomeness.146287/page-2#post-1730430]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-band-commander-68-fender-bandmaster-ab763.111596 Yek's write-up]

==BIG HAIR (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "It was a total guess. I just tuned it by ear. It's just my idea of what 80's hair metal might sound like." [http://forum.fractalaudio.com/posts/700269/]
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-big-hair.111635/ Yek's write-up]

==BLANKENSHIP LEEDS (Dweezil Zappa's Blankenship Leeds 21)==

[[file:blankenship.jpg|300px]]

Model:
* Single channel

[[Cabinet models list|Cab:]] 2x10, 1x12, 2x12 (G12M)

Volume, Tone, Tremolo

Power tubes: EL84

# "Based on a Blankenship Leeds which is a boutique version of an 18W Marshall. This particular amp is known for sounding “big” despite being relatively low power."
# "The model was matched to Dweezil's amp. He loaned it to me because it was one of his favorite amps and I can see why. It's a really cool amp."
# "The amp has no hi-cut circuit therefore the control won't do anything. Neither will the Depth."
# "18W Marshalls are kind of a bad design. The phase inverter drives the power tubes too hard which results in excessive bias excursion.” [http://forum.fractalaudio.com/threads/marshall-1974x.121516/#post-1446363]
# "The phase inverter design causes significant bias excursion. That bias excursion, however, causes the amp to sound more open when driven hard (at the expense of crossover distortion)." [https://www.thegearpage.net/board/index.php?threads/is-digital-getting-too-real.2275913/post-32977457]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-blanknshp-leeds-blankenship-leeds-21.111681/ Yek's write-up]

==BLUDOJAI CLEAN (Bludotone Ojai)==

[[File:ojai.png|300px]]

Models:
* Clean channel with PAB (Pre-Amp Bypass) OFF
* Overdrive channel with PAB OFF
* Overdrive channel with PAB ON

[[Cabinet models list|Cab:]] Bludotone 1x12, 2x12 (G12-65, EVM)

Volume, Overdrive Level (Overdrive channel only), Treble, Middle, Bass, Master, Presence. Switches: Bright, Mid (not modeled), Rock/Jazz (not modeled). Footswitchable Pre-Amp Bypass (PAB) which bypasses the tonestack (Bass / Middle / Treble)

Power tubes: 6L6

Forum member AustinBuddy, owner of the original amp:
# "The model is of a 100w 6L6 BludoDrive Ojai by Bludotone amps, using Fractal's MIMIC process. The Ojai has the same schematic as the famous "Tan" boutique amp played by Robben Ford. It pairs well with the factory Rumble 4X12 cabinet. On the Ojai there is a bright cap on the Master Volume. As you turn the MV down, it will get thinner. This makes the MV even more sensitive than usual since there’s another interaction going on. To get the most range out of this amp, experiment with Master Volume and listen how it interacts with low or high Drive settings, similar to the real amp. The breakup range/tones between is wide and dynamic and can respond to your playing dynamics, getting crunchier as you dig in and cleaner as you play lighter. The amp's Bass response should increase noticeably as you turn up the Master Volume from the default MV position. Pair it with a G12-65H speaker. Cab Pack 17 has many choices (full disclosure, I produced 5 of the 6 Cabs in that Cab Pack). The BludoMix Cab in factory firmware is a 1x12 Alnico dual port cab, and will sound good but perhaps a tad darker (great for Jazz) on clean sounds than the G12-65H will. Now, if you like, put a Zen drive in front on the BludoClean amp....or a boost...and listen to how that clean channel wakes up fast for grittier leads and touch-responsiveness. For BludoLead, take the Lead default amp values. Put the Master Volume on 5. Put drive at 4-5 and Overdrive at 4-5, and experiment with the tone stack swaps above. If you want the amp to feedback effortlessly on a note, raise the overdrive setting higher combined with the gain, provided you have sufficient volume coming out your speakers to hit your guitar pickups in a reinforcing loop, it will do it! Throw a boost or Zen drive on that, if you like..." [http://forum.fractalaudio.com/threads/dumble-ford-2-again.105028/page-2#post-1267280]

# "The tone stack in the PAB models is a neutral tone stack which is the same as lifting the ground. Put all knobs at noon if you want authentic." [http://forum.fractalaudio.com/threads/love-3-0-but.147215/page-3#post-1739726]
# "The tone stack in the PAB models is a neutral tone stack which is the same as lifting the ground. Put all knobs at noon if you want authentic. Unlike the amp, however, you can actually adjust the tone controls and something will happen. In the virtual realm we can have lifted tone stacks that actually still work." [http://forum.fractalaudio.com/threads/love-3-0-but.147215/page-3#post-1739726]
# "Pre, mid and post aren't absolute locations. They're relative to the particular model. In the Lead model there is a buffer and then three gain stages IIRC. Pre means the tone stack is before the three gain stage in this case. Changing it to Mid would put it after the first gain stage. In the Clean model there is only a buffer and one gain stage. In this case mid means the stack is between the buffer and gain stage. Changing it to pre would put it before the buffer. Since there are only two tubes pre would indicate before the buffer which is not what we want. In the PAB model there is no tone stack so I put a neutral tone stack after the gain stages (with a fixed attenuation after the buffer). This allows the most flexibility. The HRM case the neutral tone stack is replaced by a Marshall tone stack." [http://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-3-01.147229/page-2#post-1739969]
# "The real amp has Overdrive Volume (sometimes labeled Ratio) and a Master Volume. The models assume the Overdrive Volume is at maximum." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-16-01-cygnus.172911/post-2091820]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-bludojai-bludotone-ojai.111724/ Yek's write-up]

==BLUDOJAI LEAD==

Formerly: BLUDOJAI LEAD 1

==BLUDOJAI LEAD PAB==

Formerly: BLUDOJAI LEAD 2

==BOGFISH BROWN (Bogner Fish preamp)==

[[File:fish.png‎|300px]]

Models:
* Strato channel
* Brown channel

Master, Gain, Bass, Mid, Treble

Power tubes: EL34

# "I used the power amp models from the XTC." [https://forum.fractalaudio.com/threads/bogner-strato-and-brown-poweramp-modeling.76238/#post-931081]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-bogfish-bogner-fish.111780/ Yek's write-up]

==BOGFISH STRATO==

==BRIT 800 2204 HIGH (50W Marshall JCM 800 2204)==

[[file:2203.png|300px]]

Models:
* Low input
* High input

[[Cabinet models list |Cab:]] Marshall 4x12 (G12M, G12H, G12-75, V30)

Pre-Amp, Bass, Middle, Treble, Presence, Master

Power tubes: EL34

# "It is a very bright model. However, it sounds exactly like the amp it was based on. If it is too bright, you can adjust the various tone controls and parameters to reduce the brightness to your tastes. They are designed to be run loud and the brightness decreases as the MV is increased. The sound of 80's hair metal for sure." [https://forum.fractalaudio.com/threads/afxii-jcm800-model.38498/#post-525964]
# "The saturation switch switches in a zener diode clipping stage right before the tone stack. This is the Arrendondo Mod." [http://forum.fractalaudio.com/threads/axe-fx-ii-technical-questions-thread.35997/page-38#post-494304]
# "Rips my head off here. I have to turn the presence way down. Check the MV. Too high and will get muddy." [http://forum.fractalaudio.com/threads/jcm-800-sounds-a-bit-muddy-with-fw-6-0-tips.51063/#post-657800]
# "That "interference" is due to all the treble peaking used in the design. JCM800s have quite a bit of treble boost. When you first attack the string the note is unpitched. It's basically a brief explosion of noise. The treble boosting amplifies the upper frequencies of this noise burst which is what you hear. However, when you playing in a loud mix that treble boosting helps the sound cut. Modern designs use more carefully crafted treble boosting to retain the cut but tame some of the harshness of the attack. This is accomplished typically by putting a capacitor in parallel with the plate resistor(s) which rolls off around a few kHz. This preserves the treble boost in the upper midrange but softens the attack. I believe the SLO100 was one of the first amps to do this. You can see this in the Axe-Fx II as your Triode Freq parameters. You can soften the JCM800 attack by lowering the Triode Freq values. Most modern hi-gain designs use some form of HF rolloff like this. Another reason is that JCM800s use relatively low amounts of negative feedback (which is why they're so loud). This causes a treble boost in the power amp. Increase the Damping parameter to increase the negative feedback." [http://forum.fractalaudio.com/threads/cliff-how-can-i-ever-have-doubted-you.63107/#post-781950]
# "Those amps are all designed to get their character from power amp distortion. If you don't push the power amp all you are hearing is the preamp which is voiced to be trebly. The power amp then compresses the highs and the sound gets fatter." [https://forum.fractalaudio.com/posts/1235311]
# "It's a vertical input Canada export version. I went through several before settling on this one as it was the best sounding by far." [https://forum.fractalaudio.com/threads/jcm-800-question.103215/#post-1235691]
# (about moving Master volume to the post phase inverter) "It's called PPI MV or the "Lar-Mar Mod"." [http://forum.fractalaudio.com/threads/dial-in-popular-mods.119757/#post-1424257]
# "At low MV the source resistance into the PI is low which raises the highpass frequency due to the coupling cap and raises the lowpass frequency due to the Miller capacitance and snubber. As you increase the MV the source resistance increases which decreases both of these things. As you keep raising the MV the source resistance then starts to decrease as you get above 50% of the pot value." [http://forum.fractalaudio.com/threads/setting-the-master-volume.119903/page-2#post-1428935]
# "Some of them are really dull. We have two 50 watters. One is a Canadian export with bat-handle switches and sounds glorious. All nasty and spitty and full of "artifacts". The other is a "regular" one with the rocker switches. It sounds like it has a blanket over it in comparison. Our model is based on the Canadian one. Oh, and I should add that someone removed the bright cap from the Canadian one. Probably because it's so nasty with it in. I installed a new one to bring it back to it's original glory. The key to JCM800's is to crank the MV to overcome the brightness of the preamp." [http://forum.fractalaudio.com/threads/help-requested-new-afx-xl-and-digital-distortion-in-the-sound.123815/page-2#post-1478884]
# "Our reference amp had the bright cap removed by a previous owner. I put it back in. I like it on, even with a bright guitar." [http://forum.fractalaudio.com/threads/jcm800-with-our-without-bright-switch.131049/#post-1552301]
# "When modding Marshalls for higher gain sometimes the modder will decrease the input frequency response to reduce noise and fizziness. You can do this by reducing the high-cut frequency in the input EQ. Or you can use a high-shelf filter which is a little more subtle. Another technique is to put a capacitor across the second-to-last triode stage. This is the "Triode 1 Plate Freq" parameter. Reduce this to around 2 kHz to start which is typical of amps like an SLO100, etc." [https://forum.fractalaudio.com/threads/dialling-in-the-marshalls.143682/post-1707222]
# "The reference amp used for our model is a Canadian Export version (with the "bat handle" power switches). We have two JCM800s and this particular amp sounds way better than the regular one with the rocker type power switches. It's not as harsh with a warmer high end." [https://forum.fractalaudio.com/threads/nux-mg300-vs-fm3-comparison.165102/post-1980841]
# "We have two of them. One sounds amazing, the other not so much. The model is based, naturally, on the amazing sounding one." [https://forum.fractalaudio.com/threads/buttons-functioning-as-on-amps.170531/post-2052806]
# "JCM800s sound better with a hot bias IMO. The problem is the plate voltage is too high so when you set the bias higher the dissipation goes up and tube life is shortened. IMO they should've made the plate voltage around 420V. That would allow a hotter bias with longer tube life at the expense of slightly less volume but JCM800s are ungodly loud anyways so..." [https://forum.fractalaudio.com/threads/why-your-amp-doesnt-sound-like-our-amp.172907/post-2091305]
# "The 2204 models have a 10K dropping resistor between the B+ and PI. The 2203 models have 20K. The 2203 has about 17% more preamp gain than the 2204 as a result." [https://forum.fractalaudio.com/threads/brit-800-2204-vs-2203-thoughts.200705/post-2508569]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-800-and-brit-800-mod-jcm-800.111876 Yek's write-up]

==BRIT 800 2204 LOW==

==BRIT 800 2203 HIGH (100W Marshall JCM 800 2203 JMP)==

[[file:JCM8002203.jpg|300px]]

Model:
* Low input
* High input

[[Cabinet models list | Cab:]] Marshall 4x12 (G12M)

Presence, Bass, Middle, Treble, Master Volume, Pre-Amp Volume

Cliff's 2203 is an unmodified unit with metal toggle switches and faded brown grille cloth. It has vertical inputs and drake transformers.

Power tubes: EL34

# "It's a vertical input model." [https://forum.fractalaudio.com/threads/marshall-jmp-100w.198803/post-2481704]
# [https://forum.fractalaudio.com/threads/marshall-jmp-100w.198803 Forum discussion]
# [https://wiki.fractalaudio.com/wiki/images/0/05/JCM8002203.jpg Picture of the modeled amp]
# "The reference amp I just received had no bright cap. It wasn't snipped out. It may have been removed by unsoldering it but if they did they cleaned up as there is no residual flux on the terminals. This is the second JCM800 I've encountered with no bright cap. I installed a bright cap in it because every schematic shows a bright cap and the model is based on the amp w/ the bright cap installed. Other tidbits about it: B+ is a bit on the low side, around 450V. Feedback is 100K from 4-ohm tap. Transformers are same as US/UK versions. OT has 4/8/16 taps but 16-ohm tap is not connected. Preamp measures virtually identical to my 2204." [https://thegearforum.com/threads/leons-new-video-comparing-2203-in-different-modelers.3866/#post-146022]

==BRIT 800 2203 LOW==

==BRIT 800 #34 (50W Marshall JCM 800 with virtual Santiago #34 modifications)==

[[File:Logo small.png]]

Custom Fractal Audio model

Notes: see Brit 800

Power tubes: EL34

# "Based on the “Santiago #34” modifications."
# "The Brit 800 #34 does a better Slash than the AFS100 IMO. The AFS100 models are based on the actual amp but I think my version of #34 sounds more like AFD. I based the model on information I've collected over the years about the mods that were done." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-00-firmware-release.124944/page-5#post-1486357]
# "The Brit 800 #34 has a ton of treble boost and will squeal with certain guitars and/or certain IRs and/or certain types of amplification. Nature of the beast. No other amp has anywhere near the amount of treble boost. The AFD100 amp that Marshall produced years later (that was supposed to be a #34 copy) has nowhere near the amount of treble boost and has a huge snubber cap on the PI (which rolls off the treble). My gut tells me that they did this because they feared there would be too many reports of pickup squeal (or the amps would be too unstable at high gain)." [http://forum.fractalaudio.com/threads/squealing-like-mad.132058/#post-1563723]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-800-and-brit-800-mod-jcm-800.111876 Yek's write-up]

==BRIT 800 MOD (50W Marshall JCM 800 with virtual modifications)==

[[File:Logo small.png]]

Custom Fractal Audio model

Notes: see Brit 800

Power tubes: EL34

# "Based on popular modified Marshall JCM800. These mods make the amp “heavier” and less strident."

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-800-and-brit-800-mod-jcm-800.111876/#post-1338002 Yek's write-up]

==BRIT AFS100 1 (Marshall AFD100SCE)==

[[file:AFD.jpg|300px]]

Models:
* Amp in mode "#34"
* Amp in mode "AFD"

[[Cabinet models list |Cab:]] Marshall 4x12 (V30)

Gain, Bass, Middle, Treble, Presence, Master, #34/AFD switch, Depth (Brit Super model only)

Power tubes: 6550

# "I have an actual Slash signature model and spent a lot of time measuring, listening and comparing." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-2-01-firmware-release.111657/page-8#post-1337247]
# "The Brit 800 #34 does a better Slash than the AFS100 IMO. The AFS100 models are based on the actual amp but I think my version of #34 sounds more like AFD. I based the model on information I've collected over the years about the mods that were done." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-00-firmware-release.124944/page-5#post-1486357]
# "The Brit 800 #34 has a ton of treble boost and will squeal with certain guitars and/or certain IRs and/or certain types of amplification. Nature of the beast. No other amp has anywhere near the amount of treble boost. The AFD100 amp that Marshall produced years later (that was supposed to be a #34 copy) has nowhere near the amount of treble boost and has a huge snubber cap on the PI (which rolls off the treble). My gut tells me that they did this because they feared there would be too many reports of pickup squeal (or the amps would be too unstable at high gain)." [http://forum.fractalaudio.com/threads/squealing-like-mad.132058/#post-1563723]
# "The amount of treble peaking needed for an amp at a given drive is highly dependent on the guitar. For example my guess is that the AFD100 was designed around a Les Paul. With my Suhr it's much too bright because that's a very bright guitar. So one of the first things I do with the AFS100 model is turn down the bright cap a bit." [https://forum.fractalaudio.com/threads/firmware-1-11.140004/page-2#post-1660177]
# "Reference amp is a Slash AFD100 Signature Special Collector's Edition #76. Hand-signed by Slash with COA." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-19-00-beta-3.180388/post-2207142]
# "Default MV is quite high in that model which will mask the effect of the Presence control since the power amp is distorting heavily (I find that amp sounds best with the power amp driven hard). Turn the MV down and you'll notice the Presence control will have much more effect." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-00.189017/post-2343032]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-afs100-and-brit-super-marshall-afd100.111919/ Yek's write-up]

==BRIT AFS100 2==

==BRIT BROWN (custom model, producing the Plexi "Brown Sound")==

[[File:Logo small.png]]

Custom Fractal Audio model

[[Cabinet models list | Cab:]] Marshall 4x12 (G12M, G12H, G12-EVH, V30, JBL D120)

Power tubes: EL34

# "The Brit Brown was built by ear." [https://forum.fractalaudio.com/threads/evhs-original-plexi-and-the-fas-brit-brown-amp.81986/#post-995265]
# "Brit Brown is my personal take on what the ultimate "Brown" plexi should sound like. It's based on a 100W SLP with Arredondo mods and a few little voicing tweaks." [https://forum.fractalaudio.com/posts/1152917]
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]
# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-brown-and-fas-brown.111974/ Yek's write-up]

==BRIT JM45 (Marshall JTM 45)==

[[file:JTM.png|300px]]

Models:
* Treble (High) channel
* Normal and Bright channels jumpered

[[Cabinet models list |Cab:]] Marshall 4x12 (G12M, G12H)

Volume Normal, Volume High Treble, Bass, Middle, Treble, Presence

Power tubes: EL34

# "They had no Master Volumes so people rarely got the Drive past 3.00 since it would melt your face. Without the specter of having your skin flayed off as is afforded by a model of the amp, the temptation is to turn the Drive way up. When you do this the low notes get very muddy. Single notes can form an almost perfect square wave which will sound like a synthesizer." [http://forum.fractalaudio.com/threads/jm45-and-jm45-jump-sound-horrible-for-low-e-and-a-strings-not-a-bug.76286/#post-931633]
# "Our reference amp has a 100 pF bright cap. Many JTM45s did not but I think they sound better with one. A JTM45 with a bright cap is similar to a Superlead. If you want the Channel 1 sound with an Axe-Fx use the Brit JM45 Jump model and turn the Treble Drive knob all the way down." [http://www.thegearpage.net/board/index.php?threads/fractal-vs-helix-the-comparison-series-made-by-yours-truly.1757067/page-2#post-22868763]
# "When modding Marshalls for higher gain sometimes the modder will decrease the input frequency response to reduce noise and fizziness. You can do this by reducing the high-cut frequency in the input EQ. Or you can use a high-shelf filter which is a little more subtle. Another technique is to put a capacitor across the second-to-last triode stage. This is the "Triode 1 Plate Freq" parameter. Reduce this to around 2 kHz to start which is typical of amps like an SLO100, etc." [https://forum.fractalaudio.com/threads/dialling-in-the-marshalls.143682/post-1707222]
# "The very first models used a 5881, after that KT66 then EL34." [https://forum.fractalaudio.com/threads/jtm45-bug.164255/post-1969445]
# (negative feedback) "I've seen JTM45s with 27K off the 16-ohm tap. That's a lot of feedback. In this case you would then double the feedback on top of the 3.3 so 9.9 or so." [https://forum.fractalaudio.com/threads/negative-feedback.188769/post-2340464]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-jm45-marshall-jtm-45.112030/#post-1339718 Yek's write-up]

==BRIT JM45 JUMPED==

==BRIT JVM OD1 GREEN (Marshall JVM410H)==

[[file:jvm.png|300px]]

Models:
* OD1 Green
* OD1 Orange
* OD1 Red
* OD2 Green
* OD2 Orange
* OD2 Red

[[Cabinet models list |Cab:]] Marshall 4x12 (V30 and G12H)

Master, Bass, Middle, Treble, Gain, Presence, Resonance, Reverb (not modeled)

Power tubes: EL34

# "IMO, the reason the JVM sounds good is the plate cap on the second-to-last triode. That smooths out the tone considerably. The second-to-last triode is associated with "Triode 1 Freq" in the advanced parameters. You can adjust this to simulate adding a cap to the plate. The other thing that helps the tone is the 220K plate resistor on the last triode. This shifts the bias point down vs. a "classic" Marshall. Unfortunately the bias points aren't exposed to the user." [https://forum.fractalaudio.com/threads/holy-crap-the-new-jvm-sounds-great.44628/#post-588030]
# "The JVM has a huge plate resistor on the cathode follower, the JS does not." [https://forum.fractalaudio.com/threads/jvm-sounding-weird.150157/page-2#post-1785256]
# (about OD 1 Orange and Red compression):
#* "Real amp does this. Poor cathode follower design."
#* (why doesn't this happen with the Green channel) "Because the Green channel only has one tone stack hanging off the cathode follower."
#* (why doesn't this happen with the OD2 channels) "OD1 has a different tone stack. The gains are the same. The models are very accurate." [https://forum.fractalaudio.com/threads/jvm-410-model-issue.156087]
# "With an amp like the JVM it's very easy to saturate the virtual power amp. The real amp has two masters, a channel master and a global master. So the level in to the power amp is the product of those two masters. The model only has one so if you set the MV the same as the channel master and the global master isn't at 10 then you'll be overdriving the model's power amp much more than the amp. Just lowering the MV a touch will make the amp brighter for a given Presence value." [https://forum.fractalaudio.com/threads/5150-presence-knob.199908/page-6#post-2492390]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-jvm410-marshall-jvm410.112092/ Yek's write-up]

==BRIT JVM OD1 ORANGE==

==BRIT JVM OD1 RED==

==BRIT JVM OD2 GREEN==

==BRIT JVM OD2 ORANGE==

==BRIT JVM OD2 RED==

==BRIT PRE (Marshall JMP-1 preamp)==

[[image:Cliff JMP-1.jpg|300px]]

Model:
* OD channel

Volume, Gain, Bass, Mid, Treble, Presence, Bass Shift (not modeled)

Power tubes: EL34

# "The two channels have preset tone stacks. Then there is a digitally controlled 4-band graphic EQ which is the B/M/T and Presence. This technique gets around the problem of trying to digitally control a tone stack. The Triaxis uses LDRs in place of potentiometers. The Soldano X-99 uses motorized pots. Both techniques being expensive. So the JMP-1 uses a fixed tone stack and then a digitally controlled graphic EQ. The Axe-Fx model of the JMP-1 is "better" in the sense that the tone controls control the tone stack rather than a graphic EQ. You then have the separate graphic EQ to further tailor the sound. What I didn't do, and why people probably feel the model differs, is "normalize" the tone controls so that with B/M/T at noon the tone stacks match. On the Axe-Fx you might need to set the Bass to 3, Mid to 7, etc. to get the tone to match. I just used a standard Marshall tone stack whereas the JMP-1 uses a standard Marshall tone stack but the pots are replaced with fixed resistors but those values don't necessarily correspond to the pots at noon." [https://forum.fractalaudio.com/posts/1228348]
# "The JMP-1 tone controls have more range than the actual preamp. The preamp has about +/- 8 dB for each tone control while the model has the standard +/- 12 dB."
# "Brit Pre is a legacy model from the original Axe-Fx. It's not as accurate but some people really liked it so we kept it and created new models for the Ares/Cygnus platform." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-19-02-public-beta.181521/post-2224791]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-pre-and-brit-jmpre-1-marshall-jmp-1.112139/ Yek's write-up]

==BRIT SILVER (Marshall Silver Jubilee, previously: Lerxst Omega)==

Jubilee image to be added [[file:Lerxst.jpg|300px]]

Model:
* Lead channel with Gain pushed in

[[Cabinet models list |Cab:]] Marshall 4x12 (V30)

Presence, Bass, Middle, Treble, Gain, Master

Power tubes: EL34

Before firmware 24.03:
# "Our reference amp for the Silver Jubilee is actually not a Silver Jubilee. It's a Lerxst Omega that Alex Lifeson gave me." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-5-cygnus-firmware-public-beta-2.170901/post-2058221]

Firmware 24.03:
# "The model is now based on a Silver Jubilee. The Lerxst is actually almost identical except for the taper of the mid control. In a Silver Jubilee the mid pot is log, in the Lerxst it's linear. Guess Alex likes mids... So if you want the sound of the old model turn up the mids." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-24-03-release.200627/post-2504840]
# "It's the lead channel w/ the gain knob pushed in. The pull rhythm clip thing is this amp is an enigma. If implies that it's only active in the rhythm channel but it affects the lead channel too." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-24-03-release.200627/post-2504798]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-silver-marshall-silver-jubilee.112184 Yek's write-up]

==BRIT STUDIO 20 (Marshall SV20H)==

Model:
* Marshall Studio Vintage 20 (20W version of 1959 Super Lead Plexi)

Notes: see 1959SLP

Power tubes: EL34

# "The schematic doesn't show it but there's a cathode bypass cap on one of the triode stages." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2320134]
# "It's a cool little amp. It's very loud though. It's not really a "bedroom amp" IMO. Good for smaller gigs, rehearsals, etc." [https://forum.fractalaudio.com/threads/comparing-brit-20-to-real-sv20h-anyone-done-it.188338/post-2336176]

==BRIT SUPER (Marshall AFD100 schematics)==

[[file:AFD.jpg|300px]]

Model:
* Marshall AFD100 in AFD mode

Notes: see Brit AFS100

Power tubes: EL34

# "Brit Super model is based on the Marshall AFD100." [https://forum.fractalaudio.com/threads/great-sound-with-my-splawn-nitro-4cm-im-blown-away.55549/#post-700713]

==BUDDAH DUOMASTER (Budda Twinmaster)==

[[File:Logo small.png]]

Model:

* Single channel

[[Cabinet_models_list|Cab]]: 1x15 Budda Phat 15 or 1x12 Budda Phat 12

Bass, Treble, Volume

Power tubes: EL84

# "I bought a Budda Twinmaster, pulled it apart and traced the circuit since I couldn't find a schematic for it anywhere. Funky amp. Paraphase phase inverter. Weird Bridge-T sorta tone stack. I'm convinced the feedback is connected to the wrong node but I quadruple-checked and my schematic is definitely correct. I think it was probably a mistake but then they said "Hmmm, but it sounds good so don't fix it"." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-12-cygnus-firmware-public-release-candidate.172027/post-2075782]
# "The Buttery model was REPLACED by a Budda Twinmaster model. Totally different model." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-12-cygnus-firmware-public-release-candidate.172027/post-2076481]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-buttery-budda-twinmaster.112228/ Yek's write-up]

==CA3+ CLEAN (Custom Audio Amplifiers 3+ SE preamp)==

[[file:CAE.png|300px]]

Models:
* Clean channel
* Rhythm channel
* Lead channel

Gain, Bass, Middle, Treble, Master, Bright switch. Active tube EQ: Treble and Bass

Power tubes: EL34

# "The CA3+SE model is basically an OD100." [https://forum.fractalaudio.com/threads/is-the-suhr-od-100-in-the-axe.75090/#post-918169]
# "An OD100 is the head version of a CAE 3+."
# "That's a "James" tone-stack. You can find simulations on-line but typically you would get close using shelving filters with frequencies of 100 and 1000 Hz." [http://forum.fractalaudio.com/threads/cae-3-se-global-eq-anybody-know-the-freqs.33103/#post-461976]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-ca3-cae-3-se.112399/ Yek's write-up]

==CA3+ LEAD==

==CA3+ RHYTHM==

==CAMERON CCV 1A (Cameron CCV-100)==

[[file:ccv.jpg|300px]]

Models:
* (1A) Channel 1, less gain
* (1B) Channel 1, more gain
* (2A) Channel 2, Bright1 switch left, Bright2 switch left, Gain Style switch left
* (2B) Channel 2, Bright1 switch left, Bright2 switch right, Gain Style switch left
* (2C) Channel 2, Bright1 switch left, Bright2 switch left, Gain Style switch right
* (2D) Channel 2, Bright1 switch left, Bright2 switch right, Gain Style switch right [https://forum.fractalaudio.com/threads/just-a-heads-up.97371/#post-1168902]

Channel 1: Punch (= Resonance / Depth), Presence, Master, Bass, Middle, Treble and Gain, 3-way Voicing switch (resonance), 3-way Dark switch (presence), 3-way Gain Style switch (“Jose Master” gain/clipping), 3-way Bright switch (less noticeable at higher gain settings)

Channel 2: Punch (= Resonance / Depth), Presence, Solo Master, Master, Bass, Middle, Treble, two Gain controls, 3-way Gain Style switch, two Bright switches, Drive switch

The 2C and 2D models have lower output because of the Sat switch position.

Power tubes: EL34

# "The amp was modeled with the Voicing switch in the middle position. The "Dark" switch is the Negative feedback control. Set Negative Feedback to 3.6 to reproduce the switch in the middle position. Set it to 9.8 to reproduce the switch in the right position. 5.0 for left position (default). The amp has a dozen switches and, frankly, there isn't a lot of difference between some of the settings. The Drive switch sounds virtually identical whether left or right. I don't like it in the middle." [https://forum.fractalaudio.com/threads/just-a-heads-up.97371/#post-1168912]
# (about the Drive knob) "Our reference amp has a linear taper pot so the behavior is very abrupt. The model matches the amp extremely accurately (as do all G3 models)." [https://forum.fractalaudio.com/threads/fw-18-01-camron-ccv-not-a-bug.97385/#post-1168811]
# "It's a bit of a quirky amp and kind of a one-trick pony but, man, what a trick." [https://forum.fractalaudio.com/threads/fw-18-01-camron-ccv-not-a-bug.97385/#post-1168922]
# "Yes, it's actually not a very high gain amp. The topology is very similar to a JCM800." [https://forum.fractalaudio.com/threads/fw-18-01-camron-ccv-not-a-bug.97385/#post-1169347]
# "The key to the CCV sound is the Sat Switch." [https://forum.fractalaudio.com/posts/1169015]
# "Camerons have linear taper MV and you need it with them because the signal level into the power amp is very low due to the Jose topology." [https://forum.fractalaudio.com/threads/mv-poll.170996/post-2059425]
# "Humans perceive high frequency thermal noise as hiss. The more gain the more hiss. Diezel's have a lot of filtering. Large grid stoppers, plate capacitors, etc. This reduces the bandwidth which lowers the hiss. Camerons are pretty much wide open. Small grid stoppers or bypass caps on the grid stoppers, no plate caps, etc." [https://forum.fractalaudio.com/threads/why-lower-gain-cameron-ccv-amp-model-feels-more-noisy-than-much-higher-gain-herbie-3.188658/post-2339783]
# "The Cameron is a genuine Cameron. I don't know the lineage of the Atomica." [https://forum.fractalaudio.com/threads/are-any-of-the-cameron-models-of-mark-cameron-built-amps.199792/#post-2489827]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-cameron-ccv.112486/ Yek's write-up]

==CAMERON CCV 1B==

==CAMERON CCV 2A==

==CAMERON CCV 2B==

==CAMERON CCV 2C==

==CAMERON CCV 2D==

==CAPT HOOK 1A (Hook Captain 34)==

[[file:capt34.jpg|300px]]

Models:
* (1A) Channel 1, EQ Bypass switch OFF, Boost switch OFF
* (1B) Channel 1, EQ Bypass switch engaged (no Bass / Middle / Treble), Boost switch ON
* (2A) Channel 2, Edge switch OFF
* (2B) Channel 2, Edge switch ON
* (3A) Channel 3, Edge switch OFF
* (3B) Channel 3, Edge switch ON

[[Cabinet models list |Cab:]] Hook 2x12 or 4x12 (V30, G12H, G12-65, WGS)

Channel 1: Gain (with Pull function), Level, Bass, Mid, Treble, Boost switch (not modeled), EQ bypass switch, Bright switch. Shared: Presence and Balls

Channels 2 and 3: Gain, Level, Bass, Mid, Treble, Boost switch, Edge switch (changes tone stack). Shared: Presence and Balls

Power tubes: EL34

# "This amp uses a mu follower which yields a complex distortion with smooth decay. To simulate the Boost switch use the Boost switch in the amp block as it has the same amount of gain." [https://forum.fractalaudio.com/posts/1426113]
# "A mu follower is similar to a cascode configuration except the output is off the cathode instead of the plate. So the output impedance is lower." [http://forum.fractalaudio.com/threads/the-hook.120307/#post-1432379]
# (mimic Pull Gain on clean channel) "Just set the Tonestack Type to Hook Clean 2." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-5-00-firmware-released.120358/page-10#post-1433059]
# "The Capt. Hook's "thing" is that it's basically a JCM800 with the cathode follower replaced by a mu-follower. A mu-follower doesn't compress and distort like a cathode follower does. This results in the amp sounding more open and smoother." [http://forum.fractalaudio.com/threads/recommended-adjustment.133602/page-2#post-1579933]
# "The Hook Clean 1 is a Fender style tonestack which has a lot more insertion loss than the others." [https://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-5-00-firmware-released.120358/page-10#post-1433058]
# "The Hook uses a "mu follower" instead of a cathode follower. Cathode followers have low output impedance but distort quite easily. Mu followers address some of the problems of cathode followers." [https://forum.fractalaudio.com/threads/dialling-in-the-marshalls.143682/page-7#post-1708218]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-capt-34-hook-captain-34.119935 Yek's write-up]

==CAPT HOOK 1B==

==CAPT HOOK 2A==

==CAPT HOOK 2B==

==CAPT HOOK 3A==

==CAPT HOOK 3B==

==CAR ROAMER (Carr Rambler)==

[[file:rambler.jpg|300px]]

Model:
* Single channel

[[Cabinet models list |Cab:]] Carr 1x12 (Eminence Elsinore)

Volume, Treble, Middle, Bass, Pentode/Triode (not modeled), Reverb (not modeled), Tremolo

Power tubes: 6L6

# "It's basically a Deluxe Reverb preamp with a cathode bias 6L6 power amp and no negative feedback. Sort of a Fender-meets-Vox thing." [https://forum.fractalaudio.com/threads/carr.78974/#post-960532]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-car-roamer-carr-rambler.112529/ Yek's write-up]

==CAROL-ANN OD-2 (Carol-Ann OD-2)==

[[file:od2.jpg|300px]]

Model:
* Overdrive channel

Master, Pre Gain, Drive, Bass, Middle, Treble, Presence, Sparkle (not modeled), Shift switch (not modeled)

Power tubes: 6L6

# "CAs are definitely dark amps. Sound great though." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-10-cygnus-firmware-public-beta-7.171198/post-2066490]
# "If you like the base Dumble sound but want a little more gain without the fuzziness of a Fuchs try the Carol-Ann models." [https://forum.fractalaudio.com/threads/fuchs-ods-in-cygnus.172291/post-2081523]

Alan Phillips:
# "In the real world the OD2 is very very fussy on speaker choice too. The real world speakers of choice are EVM12L in a 1x12 rear ported and 2x12 with Celestion Classic Lead 80's. I found the 12L emulation did a pretty good job. Some of the others sounded so artificial with that model. Like a Rockman. Coupled with the right cab the emulated model does a good job of representing the basic tonal signature of the amp".
# "It's not a competitive model, it's a live demo of an OD2 as tweaked by me. Damn sight better than sound clips for auditioning to guys that haven't got the ability to get to a Dealer. Clearly it doesn't give you the full experience of the full amp, but is a good tonal taster. I repaired a Soldano SLO for him one day and when he came over my house to pick it up we just decided it would be a good idea to put a CA model in there. Having the actual builder involved kind of closes the loop fully. I'm happy to endorse that model because I put a lot of hours testing it and putting together a ton of technical information, fourier analysis graphs, frequency response graphs, schematics etc that would make validation of a mathematical model much easier. In reality even though the power amp and the preamp are modeled the pre-amp got the most effort. As I said in another thread, I tuned that by putting the axe in to the actual power amp of an OD2 and running that side by side with a full OD2. The final tweaks were made like that using parametric eq blocks that were hard coded in to the model. You could call that the icing on the cake and basically put the same level of tuning into the model as I do with a actual OD2. The only difference was I was using a GUI, not resistors and capacitors."
# "The OD2 and to some degree the OD3 uses HRM style gain staging with a Plexi PI and power amp. Thats common knowledge, I've talked about it in depth many times. I really liked the idea of driving the tonestack from a common cathode stage as opposed to a cathode follower like a Marshall because it got rid of some of the artifacts I don't like with say a JCM-800. Yes that's something that Dumble came up with that I have to give him major props for. I wanted an amp that would have a little more gain than a JCM-800 but with the character of a Plexi without any fizz or harsh upper mid/lower treble frequencies. Remember this was BEFORE anyone had even degooped or documented a Bluesmaster style circuit and the only thing Shad was building was his post count at AmpGarage asking about Dumble circuits. I do find it amazing it took other guys years to catch on with moving the pots to the front. It does require a bit more thought than just moving the pots as the ranges of those trimmers Dumble used is impractical when used as front panel controls (which they were not really intended to be). I do also agree with you that from a pure tone standpoint having nothing on the front panel is always going to be better. The JB100 model is basically an OD2 with the entire OD circuit on the board with predefined filters made up of quality components without adjustment through fragile trimmers. The OD2 was never designed to be put side by side in a Dumble clone fest in some guys living room with everyone playing their best Ford licks, it was designed to be used on stage for guys who played in cover/blues/wedding/classic rock bands. The seperate eq and the tube driven effects loop were added for that situation. I have always tried to avoid that association as much as possible because the average Dumble lover is typically looking for a particular set of tones that may or may not be found in this amp. Early customer interaction with guys like yourself made me want to make sure people knew it was not a tonal clone of a Dumble to avoid returns/misunderstandings. The OD-2 is not the best amp for those tones, I totally agree with you, but a Dumble or clone doesn't really do fast dampened power chords like the OD-2 will do either. On the other hand, it is much more suited for blues and classic rock, not the Ford/Carlton thing. Bear in mind that its function and tone that the average player is looking for, not a particular design architecture. The fact I did use an HRM style circuit obviously (and unfortunately) placed me in the Dumble category. However, 2500 amps later its not really seen that way any more as the CA's have always had their own thing going on tonally that is very much more in a modified Marshall vein. The newer models like the Triptik 2 have absolutely nothing in common with any Dumble, not even a common cathode driven tonestack. For anyone that has played a number of real Dumbles, there is a certain thing (I hear it more in the clean channel) that is uniquely his signature. There's a certain swirl to the clean tone that is always present in his amps. However the amp doesn't overdrive anywhere close to like what I like when pushed hard. For me I would rather focus on that tone in a Plexi Marshall, but who knows what the original guy he modified this for wanted. All of this hopefully explains why I have always shied away from the Dumble comparison thing, I was truly and honestly never trying to clone a Dumble." [https://www.thegearpage.net/board/index.php?threads/fuchs-ods-classic-whats-the-word.1845787/page-4#post-24506473]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-ca-od-2-carol-ann-od2.112259 Yek's write-up]

==CAROL-ANN TRIPTIK CLASSIC (Carol-Ann Triptik)==

[[file:triptik.jpg|300px]]

Models:
* Clean channel
* Classic channel
* Modern channel

[[Cabinet models list|Cab:]] Carol-Ann 1x12 (Scholz Classic)

Input Level, Drive on channels 2 and 3, Bass, Middle, Treble, Presence, Master, Classic/Modern voicing switching

Power tubes: EL34

# "This TripTik is badass. Dumble meets Marshall with a sprinkle of 5150 power amp." [https://forum.fractalaudio.com/threads/since-10-06-came-out.70996/#post-870346]
# "I think what people like about this amp is the same reason people like the BE/HBE. These amps share the same aggressive low-cut on the input and then add bass back in the power amp. This gives clear bass response without getting flubby."
# (speaker) "It's a Scholz Classic." [https://forum.fractalaudio.com/threads/axe-fx-ii-firmware-15-00-released.87350/page-7#post-1057172]
# "Some amps have a fixed depth circuit, e.g. 5153, Freidman BE/HBE, Dirty Shirley, TripTik, Tucana, et. al. In these cases the Depth knob will default to a value that corresponds to the fixed circuit." [https://forum.fractalaudio.com/threads/lets-talk-about-the-depth-control.88747/#post-1071598]
# "CAs are definitely dark amps. Sound great though." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-10-cygnus-firmware-public-beta-7.171198/post-2066490]
# "If you like the base Dumble sound but want a little more gain without the fuzziness of a Fuchs try the Carol-Ann models." [https://forum.fractalaudio.com/threads/fuchs-ods-in-cygnus.172291/post-2081523]

Alan Phillips from Carol-Ann:
# (Classic mode): "On the real amp, you would set the Input level at 2 O'clock and the Gain at 1 to 2 O'clock to get a great classic rock rhythm tone. It's not overly different in character to the modern setting, less gain and less low end essentially."
# "It does classic rock extremely well and has one of the best clean channels I've ever designed." [https://www.thegearpage.net/board/index.php?threads/carol-ann-od2r-the-best.1908068/#post-25776544]

[https://forum.fractalaudio.com/threads/fractal-audio-amp-models-ca-triptik-carol-ann-triptik.112303/ Yek's write-up]

==CAROL-ANN TRIPTIK CLEAN==

==CAROL-ANN TRIPTIK MODERN==

==CAROL-ANN TUCANA CLEAN (Carol-Ann Tucana 3)==

[[file:tucana.jpg|300px]]

Models:
* Clean channel
* Lead channel

Input Level, Bass, Mid, Treble, Gain (Overdrive channels), Master (all channels), Presence

Power tubes: KT88

# "One of the best amps in the world IMO. I have a Dumble and a Trainwreck and various other boutique amps and the Tucana is better than all of them." [https://forum.fractalaudio.com/posts/1153214]
# "Some amps have a fixed depth circuit, e.g. 5153, Freidman BE/HBE, Dirty Shirley, TripTik, Tucana, et. al. In these cases the Depth knob will default to a value that corresponds to the fixed circuit." [https://forum.fractalaudio.com/threads/lets-talk-about-the-depth-control.88747/#post-1071598]
# "CAs are definitely dark amps. Sound great though." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-10-cygnus-firmware-public-beta-7.171198/post-2066490]
# "If you like the base Dumble sound but want a little more gain without the fuzziness of a Fuchs try the Carol-Ann models." [https://forum.fractalaudio.com/threads/fuchs-ods-in-cygnus.172291/post-2081523]

Carol-Ann:
# "Now I can only speak for the actual amp, but my preference of speaker is a Celestion Creamback 65, though I gig these regularly with a 2x12 with Celestion T75's. Its pretty forgiving on speakers compared with some models. The foot controller and bias monitor are two of the wonderful features of the actual amp, but are both moot in the model......unless Cliff wants to model the effects of real world mains power fluctuations from place to place, but the 'green zone' of the bias monitor is 62-65% plate idle dissipation power and it measures and compensates for plate voltage and screen power , which means the real amp runs best at a slightly cooler bias. The bias monitor just allows you to set that consistently from venue to venue regardless of the main power." [https://forum.fractalaudio.com/posts/1035178]
# "It's very very difficult for anyone to get a bad tone out of the real amp. It's designed that way, the range and limits on the controls, even the biasmon system makes it difficult for even a very inexperienced player to FU. The real amp has a more British overtone to it due to the fact I am British and I designed it. The gain staging, overdrive voicing and output stage are night and day to ANYTHING Mesa, any owner of the real amp would attest to that." [https://forum.fractalaudio.com/posts/1049358]
# "The Tuc 3 is very very tolerant of most cabs and speakers, unlike say the OD2. I feel people need to approach this model very simply. Don't mess with extended parameters, basically don't try and redesign it. Use a reliable Celestion based cabinet model. I have a fantastic 4x12 with 2 old greenbacks and two old v30s that is the best cab I've played the real amp through. In actual levels of gain with the two adjustable gain controls, the amp has a maximum gain level very similar to the Triptik, the setting of these two controls with respect to each other is critical." [https://forum.fractalaudio.com/posts/1049367]
# "Real world, it has the same amount of actual gain as the Triptik. Way more than most people would need for recording or live playing. Input gain on 10 o clock, gain on 2 o clock is a 70s /80s lead tone, put the input level up to 2 o click and it's a very sustained lead tone or a very modern heavy rhythm tone." [https://forum.fractalaudio.com/posts/1049530]
# "You don't need to crank the real amp to get a ton of overdrive. I actually designed the original for myself and I play in a rock cover band. There's nowhere I would ever be able to get the amp to the point of pushing the power tubes in to overdrive. You gain stage a design based on its application. For a design that needs a lot of overdrive at a low volume, you do most of that and the harmonic makeup in the preamp. The Tucana falls in to this category. The master volumes in a 500 seat club rarely get above 10 O Clock on the real amp and at that point there's still tons of clean headroom left. Of course the power amp adds to the harmonic content, but it adds very little overdrive. Another interesting point to note is that the Tucana has a high pass filter in the power amp feedback loop, which gives you a nice tight low end because the bass is subjected to more gain. For an amp designed to be pushed hard in to power tube overdrive, this should be omitted as all bets are off in the feedback loop when you hit the rails. In other words that filter requires headroom to function properly, as does the presence control of any amp where it's a component of the feedback loop." [https://forum.fractalaudio.com/posts/1050147]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-ca-tucana-carol-ann-tucana-3.112349/ Yek's write-up]

==CAROL-ANN TUCANA LEAD==

==CITRUS A30 CLEAN (Orange AD30HTC)==

[[File:ad30.jpg|300px]]

Models:
* Clean channel
* Dirty channel

[[Cabinet models list |Cab:]] Orange 2x12 (V30)

Gain, Master, Bass, Middle, Treble

Power tubes: EL84

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-citrus-a30-orange-ad30htc.112584 Yek's write-up]

==CITRUS A30 DIRTY==

==CITRUS BASS 200 (Orange AD200B bass amp)==

[[file:orangebass.jpg|300px]]

Model:
* Single channel

[[Cabinet models list |Cab:]] Orange bass cab

Volume, Gain, Bass, Middle, Treble

Power tubes: 6550

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-citrus-bass-200-orange-ad200b.112631/ Yek's write-up]

==CITRUS RV50 (Orange Rockerverb 50 MK II)==

[[File:rockerverb50.jpg|300px]]

Model:
* Dirty channel

[[Cabinet models list | Cab:]] Orange 4x12 (V30)

Dirty channel: Volume, Gain, Treble, Middle, Bass, Reverb (not modeled)

Power tubes: EL34

# "The model is based on a MKII." [https://forum.fractalaudio.com/posts/1109941]
# "The power amp in a Rockerverb has very little negative feedback so it will boost the highs more than most power amps." [https://forum.fractalaudio.com/threads/sorting-out-the-high-end.117233/#post-1398890]
# "It's not a super high gain amp. It's called a Rockerverb not a Metalverb. It's only got four gain stages and there's significant padding between stages." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-12-cygnus-firmware-public-release-candidate.172027/post-2077006]
# (Gain) "It's a ganged pot so it behaves strangely." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-16-01-beta-1-public-beta.172736/post-2088693]
# "That amp doesn't have a high cut." [https://forum.fractalaudio.com/threads/hi-cut-control-on-citrus-rv50-not-working.178740/post-2178756]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-citrus-rv50-orange-rockerverb-50-mk-ii.112668/ Yek's write-up]

==CITRUS TERRIER (Orange Tiny Terror)==

[[File:tinyterror.jpg|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Orange 1x12 or 2x12 (G12H)

Volume, Gain, Tone (High Cut), 7w/15w switch (not modeled)

Power tubes: EL84

# "The actual amp has no tone stack and a single tone control. The tone control is actually a high cut control in the power amp and is therefore replicated by the Hi Cut parameter."
# "It's inaudible when clean." [https://forum.fractalaudio.com/posts/1063208]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-citrus-terrier-orange-tiny-terror.112702/ Yek's write-up]

==CLASS-A 15W TB (Vox AC15 Top Boost)==

[[file:ac15.jpg|300px]]

Model:
* Top Boost channel

[[Cabinet models list | Cab:]] Vox 1x12 (G12M, Alnico)

Volume, Cut, Bass, Treble

Power tubes: EL84

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-class-a-15w-tb-vox-ac-15.112743/ Yek's write-up]

==CLASS-A 30W (Vox AC30 Hand-Wired)==

[[file:ac30.jpg|300px]]

Models:
* AC-30: Normal channel of AC30HW
* AC-30 Bright: Normal channel, Brilliance input
* AC-30 Hot: Top Boost channel of AC30HW, in "Hot" mode (no Bass / Treble)
* AC-30 TB: Top Boost channel of AC30HW, in "Cool" mode

[[Cabinet models list | Cab:]] Vox 2x12 (Alnico, G12M)

Volume, Bright switch (Normal channel), Treble/Bass (Top Boost channel), Hot/Cool switch (Top Boost channel), Tone Cut, Master

Power tubes: EL84

# "Note that the particular AC-30 used for the model has this scratchy high end. (...) It's a hand-wired version and that can lead to this type of sound as the parasitics cause boosting of the very high frequencies when the amp is driven hard." [https://forum.fractalaudio.com/posts/970333]
# "I intentionally limited the midrange notch since, IMO, it's a design flaw in that tone stack. But you can recover that behavior by setting the Mid control fully CCW. Modern AC30's don't have this flaw. They use a Fender-style tone stack with a fixed mid resistor."
# "The bright cap value is normalized to a Drive pot of 1M. An AC30 has a 500K pot so the value will read out as half the actual value. IOW, it's displaying 60 pF which is equivalent to 120 pF." [https://forum.fractalaudio.com/posts/1064264]
# "The Hot model models the AC-30HW model set to Hot. This bypasses the EQ for more gain. For authenticity, leave all tone controls at noon."
# "AC30's have no negative feedback on the power amp. This means the output voltage follows the speaker impedance. Therefore you get a boost at the low frequency resonance of the speaker which causes the low end to get loose when you crank it." [http://forum.fractalaudio.com/threads/crunchy-ac-30-tb-need-some-help-tightening-up-the-low-end.117675/#post-1404022]
# "AC-30's have a poorly designed cathode follower. The bias point is totally wrong and crushes one side of the signal considerably. IMO either the cathode resistor should be 100K or the plate resistor of the preceding stage should be higher, 200K. The clipping is extremely asymmetric. Too much IMO. A little asymmetry is good because it warms things up. Too much causes excessive even-order harmonics which makes things fuzzy and indistinct. The clipping is so asymmetric on an AC-30 that it's almost a half-wave rectifier. You can tweak this by adjusting the Preamp Bias point and/or lowering the Cathode Follower Compression. Or you can lower the Harmonics value which reduces the asymmetric distortion. The downside of that is that it then overdrives the phase inverter causing blocking distortion from excessive bias excursion. Another thing to try is to increase the Grid Clipping value which will add a little headroom. Start with the Bias point. AC-30's are very sensitive to the tube type and part tolerances. A tiny change in the bias point can make a big difference. The default bias point is based on Mullard ECC83 tubes. I prefer the AC-20 because it doesn't have a cathode follower so doesn't suffer from these problems. The cathode follower in an AC-30 doesn't even do all that much. Normally you use a cathode follower to preset a low-impedance source to the tone stack but the tone stack in an AC-30 doesn't present that great of a load anyways." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-02.148983/page-11#post-1767187]
# "The reference AC30 is an AC30HWHD." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-07.150305/page-6#post-1788283]
# "Our Vox models are based on a fairly new AC30HWHD head. The model matches that particular amp very well. Will it match an AC30 from a different era exactly? Probably not." [https://forum.fractalaudio.com/threads/how-accurate-is-fractals-amp-modeling.168786/post-2027668]
# "The normal channel on a Vox would be closest to the Morgan. The Brilliant channel is a "Top Boost" which means it has a tone stack and a significant midrange cut. The normal channel has no tone stack. You can't compare a a Morgan AC20 to the Brilliant channel of an AC30 and declare that one sounds better than the other. Totally different preamps and, therefore, different sound. Personally I think the AC20 is a better amp. Better made, better quality components, much better transformers. If you want that chimey AC30 sound you put an EQ before it and suck out some mids." [https://forum.fractalaudio.com/threads/how-accurate-is-fractals-amp-modeling.168786/post-2064189]
# "So-called Class-A amps (like the AC30) don't actually exhibit much power supply sag because, well, they're Class-A (or nearly). The tubes are biased hot so when one tube is conducting more the other is conducting less and the net supply current doesn't change much. Contrast this with Class-AB where when one tube conducts the other goes into cutoff causing a net increase in supply current and concomitant supply sag. What Class-A amps do exhibit is "cathode squish". The capacitor on the cathodes charges up and shifts the bias point. This reduces the gain and acts as a sort of compressor. It's a unique compression and the amp "opens up" at the same time and crossover distortion increases." [https://www.thegearpage.net/board/index.php?threads/does-this-sound-like-an-ac30-to-you.2325505/post-34009664]
# "An AC-30 has no negative feedback which is why it sounds the way it does." [https://forum.fractalaudio.com/threads/help-me-dial-in-the-ac30.192021/post-2387421]
# "In a tube power amp the lows and highs distort first because they are boosted by the speaker impedance. This causes the sound to become more midrangey and focused. Then as the signal decays the sound becomes fuller and less midrangey. It's literally one of the most important things in the way a tube amp operates and is responsible for its unique and pleasing overdrive behavior and why they became the gold-standard. This is also what makes an AC30 so unique. AC30s have no negative feedback so the lows and highs are fully boosted by the speaker impedance. When you drive them hard they get focused. When you back off the volume the become full and chimey." [https://thegearforum.com/threads/fender-tone-master-pro.3286/page-184#post-145948]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-class-a-30w-vox-ac-30.112787/ Yek's write-up]

==CLASS-A 30W BRIGHT==

==CLASS-A 30W HOT==

==CLASS-A 30W TB==

==COMET 60 (Komet 60)==

[[file:komet60.jpg‎‎|300px]]

Model:
* Single channel

Volume, Treble, Middle, Bass, Presence, Hi Cut, Touch Response switch: Fast/Gradual (not modeled)

Power tubes: EL34

# "The Komet is definitely a unique amp. Sort of like a Fender preamp into a Marshall power amp. Unique tone stack." [https://forum.fractalaudio.com/threads/new-amps-in-10-06.70362/#post-863547]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-comet-60-komet-60.112823/ Yek's write-up]

==COMET CONCOURSE (Komet Concorde)==

[[file:kometconcorde.jpg‎‎|300px]]

Model:
* Single channel

Volume, Treble, Middle, Bass, Presence, Hi Cut, Touch Response switch: Fast/Gradual (not modeled)

Power tubes: EL34

# "The Komet is definitely a unique amp. Sort of like a Fender preamp into a Marshall power amp. Unique tone stack." [https://forum.fractalaudio.com/threads/new-amps-in-10-06.70362/#post-863547]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-comet-concourse-komet-concorde.112872/ Yek's write-up]

==CORNFED M50 (Cornford MK50 II)==

[[file:cornford.png|300px]]

Formerly: CORNCOB

Model:
* Overdrive channel

[[Cabinet models list |Cab:]] Cornford 4x12 (V30)

Gain, Overdrive, Bass, Middle (500Hz), Treble, Master, Presence, Resonance

Power tubes: EL34

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-corncob-m50-cornford-mk50-ii.112922/ Yek's write-up]

==DAS METALL (Diezel VH4 schematics)==

[[File:vh4.jpg|300px]]

Notes: see Dizzy V4

Power tubes: 6L6

==DELUXE TWEED (1957 Fender narrow-panel Tweed Deluxe, 5E3)==

[[file:deluxe.jpg|300px]]

Models:
* Bright input
* Bright and Normal inputs jumpered

[[Cabinet models list |Cab:]] Fender 1x12 (P12R, C12N, Alnico)

Volume Normal, Volume Bright, Tone

Power tubes: 6V6

# "Deluxe Tweed” amp model based on a Fender 5E3 Deluxe. Note that this amp only has a single tone control. This is modeled by the Treble control in the Axe-Fx II. The Bass and Mid controls are functional and recreate the amp when set to noon. Also note that this amp suffers from extreme blocking distortion at or near maximum gain. This is common in very old designs. As it is virtually unplayable like this, the model uses a somewhat reduced level of grid conduction to lower the amount of blocking distortion and make the amp more playable at high Drive settings."
# "The G3 version of the 5E3 Deluxe Tweed model is a hoot. Totally unpredictable, nasty, gnarly and raunchy. I couldn't stop playing it yesterday. Just like the real amp you have to be careful with your volume control and how you approach the amp so that you keep it right on the edge of playability. So cool." [https://forum.fractalaudio.com/posts/1144722]
# "The Deluxe Tweed amp model is a 5E3. The 1x12 Deluxe Tweed Mix cab is the IR." [http://forum.fractalaudio.com/threads/59-deluxe.106336/page-2#post-1272464]
# "Yup, that's the key. Crank the treble almost all the way up." [http://forum.fractalaudio.com/threads/59-deluxe.106336/page-3#post-1273603]
# "The actual amp has no grid stopper resistor on the second stage and therefore has LOTS of blocking distortion." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-00-beta-3.148907/page-3#post-1764588]
# "IMO the designs are poor because... wait for it... they exhibit a papery buzz. The problem with most cathode biased Class A amps is, 1: they aren't really Class A (more like hot Class AB) and 2: They go into Class B operation when they are overdriven. The cathode capacitor charges up and the bias point shifts dramatically. This causes lots of crossover distortion (papery buzz). It's worse on lower notes because lower notes have more energy and charge the cap more. The is probably the reason Leo Fender switched to fixed bias amps with negative feedback. Fixed bias is just that, the bias point is fixed so the amp doesn't shift into Class B operation when overdriven (not as much anyways, depends on the bias circuit, grid stoppers, etc.). Negative feedback linearizes the amp and reduces the crossover distortion (at the expense of gain). That's why the buzzing went away when you increased negative feedback. Crossover distortion is a unique sound. For cleaner sounds it tends to be objectionable. For overdriven sounds some find it desirable. EVH ostensibly liked his amps biased cold to get some crossover distortion. There are even some amps that have circuits to intentionally generate crossover distortion. Some distortion pedals also do this. Lowering the Cathode Resistance reduces the crossover distortion as it keeps the amp in Class A operation longer but the tubes run hotter and don't last as long. This is not a problem with our virtual amps though. I forget the actual values but I'm pretty certain if you look at the Cathode Resistance value for those amps it's pretty high. This means the amps are biased somewhat cold to begin with and shift to very cold as soon as overdriven." [https://forum.fractalaudio.com/threads/papery-buzz-under-some-models.149193/page-2#post-1772639]
# (about fuzzy lows) "That's what those amps do. Always been that way. Just to be sure I just compared the Deluxe Verb model with the reference amp and it's correct. Those are old designs. Simple circuits with minimal frequency shaping. As such there's a lot of bass going into the power amp. That coupled with the resonance magnification of the speaker impedance causes frequencies around the resonance (in the 50-100 Hz region) to distort early. The low E string is 82 Hz so it's right in that zone." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1842156]
# "When you dime the controls and whack a big chord the sound "goes away" a bit just like the real amp and then comes back a bit later." [https://forum.fractalaudio.com/threads/you-guys-gals-are-in-for-another-treat.169535/post-2042185]
# ("Cygnus" amp modeling) "The 5E3 model is now "jumped" so it has both Normal and Bright drives. You can get all sorts of different distortion textures by playing with the two drives in conjunction with the tone control. As with the real amp everything now interacts. One of the beta testers was remarking that his 5E3 clone sounded more "choked" in comparison to the model. I said "I bet your clone has the wrong type of tube in V1. It's supposed to be a 12AY7 but many clones have a 12AX7A in V1." He checked and, sure enough, 12AX7A in V1." [https://forum.fractalaudio.com/threads/cygnus-beta-first-impressions.169942/post-2045461]
# ("Cygnus" amp modeling) "I've added a non-jumped version of the 5E3 with both volume knobs. Now we can wait for the inevitable "When I turn the Bright Drive all the way down the Normal Drive doesn't do anything" comments." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2051108]
# "Amp doesn't have a bright cap." [https://forum.fractalaudio.com/threads/deluxe-tweed-bright-switch.173082/post-2094005]
# "Some of the undesirable characteristics are what makes a particular amp unique. For example a Deluxe 5E3 is characterized by significant blocking distortion. Without that it doesn't sound like a Deluxe and you can't do the Neil Young thing." [https://www.thegearpage.net/board/index.php?threads/is-digital-getting-too-real.2275913/post-32977457]
# " If you plug into a real Deluxe the "unused" control effects the sound." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-17-00.177099/post-2159734]
# "I finished the 57 Tweed Deluxe today and it's glorious. Clean to "Cinammon Girl" with the volume knob. I never appreciated that amp until I spent some serious time with it." [https://forum.fractalaudio.com/threads/you-guys-gals-are-in-for-another-treat.169535/post-2042068]
# ("Cygnus" amp modeling) "The Bassman and Deluxe Tweed models are both modeled using a 12AY7 as the input buffer. The Preamp Tube Type parameter only affects the tubes after the input buffer." [https://forum.fractalaudio.com/threads/12ay7-preamp-tube-for-tweed-deluxe-and-bassman-models.175834/post-2135435]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-deluxe-tweed-fender-deluxe-5e3.113007/ Yek's write-up]

==DELUXE TWEED JUMPED==

==DELUXE VERB NORMAL (1965 Blackface Fender Deluxe Reverb, AB763)==

[[file:deluxereverb.jpg|300px]]

Models:
* Normal channel
* Vibrato channel

[[Cabinet models list |Cab:]] Fender 1x12 or 2x10 with a Jensen ceramic C12Q, or EVM 12L, or JBL D120, or a Fender 2x10 with a ceramic C10N or C10Q or a 25W Alnico P10R

Volume, Bass, Treble, Reverb, Vibrato (not modeled)

Power tubes: 6V6

# "A DR is numbered 1-10 so 3 on a DR is around 2.2 on the Axe-Fx. The model is based on the Vibrato input #1 which has more gain than the normal input. To simulate plugging into the #2 jack (which has half the gain) set Input Trim to 0.5." [https://forum.fractalaudio.com/posts/1260148]
# "We got our reference Deluxe Reverb out of storage today, hooked it up and measured and compared. Gain measures spot-on and A/B testing sounds identical. With a Suhr Modern guitar with stock pickups both the amp and the model were starting to break up around 3 (which equals 2.2 on the Axe-Fx since the knobs start at zero not one). A Deluxe Reverb breaks up easily since it has 6V6 power tubes. The preamp is virtually identical to a Twin Reverb but 6V6s break up earlier than 6L6s. For a given voltage into the power amp a 6V6 has about 70% of the headroom compared to a 6L6." [https://forum.fractalaudio.com/posts/1262483]
# "The values for the Deluxe Reverb model are based on measurements of an actual 65 Deluxe Reverb, not some hypothetical values on some spec sheet." [http://forum.fractalaudio.com/threads/speaker-page-does-any-of-this-make-sense.110373/#post-1322466]
# (fuzzy lows) "That's what those amps do. Always been that way. Just to be sure I just compared the Deluxe Verb model with the reference amp and it's correct. Those are old designs. Simple circuits with minimal frequency shaping. As such there's a lot of bass going into the power amp. That coupled with the resonance magnification of the speaker impedance causes frequencies around the resonance (in the 50-100 Hz region) to distort early. The low E string is 82 Hz so it's right in that zone." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1842156]
# "We have two Deluxe Reverbs, a vintage 1965 Deluxe Reverb that the model is based on and a Reissue. The vintage one sounds great, the reissue doesn't quite sound as good. It's biased too cold. The comparison was between the model and the Reissue because the vintage amp is worth a small fortune and I only use that when actually working on models. It stays in climate controlled storage otherwise." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1842188]
# "Reissue: the preamp tubes that ship in those are junk (Groove Tubes). The way I model an amp is to start out theoretically based on the schematic. It's usually pretty accurate. On our Deluxe Reverb model the real amp had much less gain than predicted. I was racking my brain trying to figure it out. Finally I decided to replace all those Groove Tubes with a different brand and, voila'. the amp now had the same gain as predicted." [https://thegearforum.com/threads/leons-new-video-comparing-2203-in-different-modelers.3866/page-5#post-148603]
# "The DR is my go-to clean-to-edge-of-breakup amp and I just verified the model against it a few days ago. It's extremely accurate." [https://thegearforum.com/threads/fractal-audio-firmware-update-thread.673/page-117#post-152618]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-deluxe-verb-65-fender-deluxe-reverb-ab763.113046/ Yek's write-up]

==DELUXE VERB VIBRATO==

==DIAMANTE FIRE (22W Diamond Del Fuego)==

[[File:Diamante.jpg|300px]]

22W Class-A amplifier with two channels, designed by Roy Blankenship, based on a '60s Class-A 18W Marshall.

Model:
* channel xx with or without tremolo

Fractal Audio:
# "Nasty little thing." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-20-01-public-beta-2-beta-5.184958/post-2280269]
# "Yeah, it's a cool little amp. It's got some different component values than the Leeds which gives a different vibe." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-20-01-public-beta-2-beta-5.184958/post-2280439]

[[Cabinet models list |Cab:]] single GH12H, V30

Tremolo controls, Volume, Tone

Power tubes: EL84

[https://kitarablogi.com/2011/12/10/review-diamond-del-fuego-english-summary/ Review and sound clips]

[https://www.youtube.com/watch?v=Sn_evdKRhgQ Amp factory tour]

[http://www.diamondamplification.com Diamond Amplification]

==DIRTY SHIRLEY (40W Friedman Dirty Shirley)==

[[File:dirtyshirley.jpg|300px]]

Models:
* Current version of the amp
* Earlier version of the amp with different component values, a little more aggressive than the regular model

[[Cabinet models list |Cab:]] Friedman 4x12 (V30, G12M, G12-65, G12H)

Gain, Master, Bass, Middle, Treble, Presence

Power tubes: 5881

# "If you want more clarity in the low mids (...) reduce Negative Feedback. Friedman's designs are a bit odd in that he takes the feedback off the speaker jack rather than off a transformer tap. (...) The amp will sound tighter and clearer in the low mids." [http://forum.fractalaudio.com/threads/underrated-amp-models.109894/page-2#post-1316362]
# "The design is weird as the negative feedback is taken off the speaker jack. So if you use a 16-ohm speaker you get more feedback (and much more bass) than if you use an 8-ohm speaker. (...) It's too much bass for me so I turn down the Depth and reduce Negative Feedback a bit." [http://forum.fractalaudio.com/threads/question-about-the-friedman-amp-presets.110511/#post-1322655]
# "At first I didn't like it but for some genres it works. The old version (new model) has a 2.2 nF cap on the cathode follower while the newer version has 4.7 nF. The larger cap smooths out the distortion. The cathode bypass cap values are different as well which changes the midrange response." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-00-public-beta-2.124097/page-18#post-1477587 ]
# "Some amps have a fixed depth circuit, e.g. 5153, Freidman BE/HBE, Dirty Shirley, TripTik, Tucana, et. al. In these cases the Depth knob will default to a value that corresponds to the fixed circuit." [https://forum.fractalaudio.com/threads/lets-talk-about-the-depth-control.88747/#post-1071598]
# "I always lower the negative feedback. Friedman amps are a bit strange because the negative feedback is taken off the speaker jack instead of one of the transformer taps. The matching cabs are 16 ohms but if you use an 8-ohm cab you'll get 30% less feedback." [http://forum.fractalaudio.com/threads/couple-of-observations-about-the-friedmans-in-7-02.126030/page-2#post-1504343]
# ("Cygnus" amp modeling) "Dirty Shirley 1 is actually the latest version of the amp." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2048948]
# "They are very dark amp when used with the matching 16-ohm cabinet. The feedback is off the speaker jack (don't ask me why, doesn't make sense). This results in a lot of negative feedback at high frequencies which makes the sound dark. The amp is modeled assuming a 16-ohm load. If you use them into an 8-ohm cabinet they're brighter. To simulate this lower the negative feedback by 1/sqrt(2). This results in a negative feedback value of 3." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2052720]
# "Dirty Shirley 2 is the brighter of the two (has a 2.2nF cathode cap instead of 4.7nF)." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2052814]
# "They are dark amps." [https://forum.fractalaudio.com/threads/cygnus-dirty-shirley-dark.173450/post-2100020]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-dirty-shirley-friedman-dirty-shirley.113088/ Yek's write-up]

==DIRTY SHIRLEY 2==

[[File:dirtyshirley.jpg|300px]]

==DIV/13 CJ (Divided By 13 CJ 11)==

[[File:cj11.jpg‎|300px]]

Models:
* Mid Gain Boost OFF
* Mid Gain Boost ON

[[Cabinet models list |Cab:]] Divided by 13 (G12M)

Volume (pull: midgain boost), Treble, Bass, Master

Power tubes: 6V6

# "It is a bassy amp. Works best with single coils." [http://forum.fractalaudio.com/threads/13-goodness-st-michael-blues.56060/#post-706664]
# "You increase the LOW CUT FREQ to reduce the fuzziness on bass notes but then it won't sound like the real thing." [https://forum.fractalaudio.com/posts/724268]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-div-13-cj11-divided-by-13-cj-11.113126/ Yek's write-up]

==DIV/13 CJ BOOST==

==DIV/13 FT37 HIGH (Divided By 13 FTR 37)==

[[File:ftr37.jpg‎|300px]]

Models:
* Low: channel 1, Mid Gain Boost OFF
* High: channel 1, Mid Gain Boost ON

[[Cabinet models list |Cab:]] Divided by 13 (G12H and Alnico)

Volume (pull: Boost), Treble, Bass

Power tubes: 6V6

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-div-13-ft37-divided-by-13-ftr-37.113127/ Yek's write-up]

==DIV/13 FT37 LOW==

==DIZZY V4 BLUE 2 (Diezel VH4)==

[[File:vh4blue.jpg|300px]]

Models:
* Blue faceplate, channel 2 Crunch
* Blue faceplate, channel 3 Mega
* Blue faceplate, channel 4 Lead
* Silver faceplate, channel 2 Crunch
* Silver faceplate, channel 3 Mega
* Silver faceplate, channel 4 Lead

[[Cabinet models list |Cab:]] Diezel 4x12 (V30, G12-100)

Power tubes: KT77

Gain, Volume, Bass, Mid, Treble, Presence (4kHz), Deep (80Hz), Bright switch (not on channels 3 and 4)

# "The reason Diezels compress so much is due to the cathode follower design. You can reduce the compression in the models by lowering the Compression parameter in the Cathode Follower section." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-14-00.165157/post-1981183]
# "The bright switch on channel 2 in the Silver version is not a conventional bright switch. It switches in a treble peaker later in the circuit. The model models the amp with the bright switch on." [https://forum.fractalaudio.com/threads/cygnus-dizzy-amps-bug.173361/post-2102309]
# "Humans perceive high frequency thermal noise as hiss. The more gain the more hiss. Diezel's have a lot of filtering. Large grid stoppers, plate capacitors, etc. This reduces the bandwidth which lowers the hiss. Camerons are pretty much wide open. Small grid stoppers or bypass caps on the grid stoppers, no plate caps, etc." [https://forum.fractalaudio.com/threads/why-lower-gain-cameron-ccv-amp-model-feels-more-noisy-than-much-higher-gain-herbie-3.188658/post-2339783]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-das-metall-and-dizzy-v4-diezel-vh4.112971/ Yek's write-up]

==DIZZY V4 BLUE 3==

==DIZZY V4 BLUE 4==

==DIZZY V4 SILVER 2==

[[File:vh4.jpg|300px]]

==DIZZY V4 SILVER 3==

==DIZZY V4 SILVER 4==

==DOUBLE VERB NORMAL (1966 blackface Fender Twin Reverb)==

[[file:twin.jpg|300px]]

Models:
* Normal: based on 1966 blackface Fender Twin Reverb, tuned by Andy Fuchs, AB763 circuit, Normal channel
* Vibrato: based on the Vibrato channel of the same amp
* Silverface: based on the Vibrato channel of a 1971 100 watts “Silverface”

[[Cabinet models list |Cab:]] Fender 2x12 with original speakers, DynaCab available

Volume, Bass, Middle, Treble, Bright switch, Reverb (not modeled), Vibrato (not modeled)

Power tubes: 6L6

# (make the Twin cleaner) "Reduce MV (or MV Trim). The biggest reason Silverface Twins were cleaner is because the PI had less gain. Reducing the MV or MV Trim will simulate the lower gain." [https://forum.fractalaudio.com/posts/910015]
# (original Double Verb model) "The Twin Reverb that the model is based on breaks up like that. The model is MIMIC'd and is extremely accurate. It's a Blackface Twin which breaks up easy compared to later Twins. Furthermore, as with all models, it is modeled on the "Hi" input. If you don't want it to break up as easy turn Input Trim to 0.5 to simulate using the "Low" input, reduce Input Drive and MV as necessary. You may want to turn the Bright Switch off as well. People who want squeaky clean usually turn the Bright Switch off on these amps. However, you'd be surprised that a Twin isn't nearly as clean as you think. It's just so damn loud that you get the sensation that it's clean because a light touch on the strings creates a lot of volume." [https://forum.fractalaudio.com/posts/968763]
# "The model is extremely accurate and is based on a 1966 Blackface Twin Reverb. Part of the reason the Blackface era are so sought after is because they distort. They are NOT clean amps by any stretch." [http://forum.fractalaudio.com/threads/twin-issue.119594/#post-1422765]
# "A Dual Showman with the AB763 circuit has one less gain stage than a Twin Reverb so it will have less gain. There are two gain stages. The Vibrato channel of an AB763 Twin Reverb has three gain stages. An AA769 Dual Showman Reverb on the Vibrato channel will have similar gain as it has three gain stages. The circuit number, i.e. AB763, does not mean that the circuits are identical. It refers to the circa of the design. An AB763 Dual Showman is not the same circuit as an AB763 Twin Reverb." [http://forum.fractalaudio.com/threads/twin-issue.119594/page-2#post-1423069]
# "The Super Reverb is really just a 50W version of a Twin Reverb with different speakers." [https://forum.fractalaudio.com/threads/wanted-amps-to-model.56753/page-4#post-713267]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-double-verb-fender-twin-reverb.113177 Yek's write-up]

==DOUBLE VERB SILVERFACE (1971 silverface Fender Twin Reverb)==

==DOUBLE VERB VIBRATO (1966 blackface Fender Twin Reverb)==

==DWEEZIL'S BASSGUY (Dweezil Zappa's 1965 blackface Fender Bassman, AB165)==

[[file:ab165.png|300px]]

Model:
* 1965 Bassman Bass channel modded by Blankenship

[[Cabinet models list |Cab:]] Fender 2x12 (Oxford)

Volume, Negative Feedback, fixed Presence circuit (Presence should be at 10)

Notes: see 65 Bassguy

Power tubes: 6L6

# "It's Dweezil's Blankenship modified Bassman. Dweezil's Bassman has two channels like a regular Bassman. The Normal channel is "normal" and corresponds to the 65 Bassguy Nrml model. The Bass Instrument channel is modified and that's the basis for the new model (Dweezil's B-man). It has a boatload of gain and sounds more like a Plexi than a Fender." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-3-00-public-beta.113410/page-5#post-1356686]
# "Just finished matching this modded 65 Bassman that Dweezil sent me. It's a crazy sounding amp, sounds nothing like your typical Fender. It was modded by Roy Blankenship." [https://forum.fractalaudio.com/threads/another-v10-preview.62489]
# "The 65 Bassguy was matched to a 65 Bassman that Dweezil sent me. It's a vicious amp that sounds more like a Plexi than a Fender. It's the infamous AB165 circuit which is very crunchy and bright and does not sound like your typical Fender." [https://forum.fractalaudio.com/threads/am-i-the-only-one-who-noticed-that-some-amps-have-alot-more-gain.51123/page-2#post-658833]
# "The actual amp has no tone stack so for maximum authenticity all tone controls would be at noon (but don't be afraid to tweak them). In the actual amp the Treble control is re-purposed as a Negative Feedback control. Experiment with different values of Negative Feedback. Lower values are looser." [http://forum.fractalaudio.com/threads/help-with-trying-out-a-new-amp-block-dweezils-b-man.114154/#post-1365573]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-65-bassguy-65-blackface-fender-bassman-ab165.111298/ Yek's write-up]

==ENERGYBALL (Engl Powerball)==

[[File:powerball.jpg|300px]]

Model:
* Lead channel

[[Cabinet models list |Cab:]] Engl 4x12 (V30, V60)

Lead channel: Gain, Lo/Hi Lead switch, Bass, Mid-Open, Mid-Focused, Treble, Open / Focused switch (boosts 300-500 Hz) mode

Power tubes: 6L6

# (Cygnus) "The model was completely redone." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-12-cygnus-firmware-public-release-candidate.172027/post-2079284]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-energyball-engl-powerball.113247/ Yek's write-up]

==EURO BLUE (Bogner Ecstasy 20th Anniversary)==

[[File:ecstasy.png|300px]]

Models:
* Blue channel, structure switch: Vintage
* Blue channel, structure switch: Modern
* Red channel, structure switch: Vintage
* Red channel, structure switch: Modern

[[Cabinet models list |Cab:]] Bogner 2x12 or 4x12 (V30)

Gain, Master, Bass, Middle, Treble, Presence, Bright switch, Structure switch (gain reduction), Old/New Style switch (not modeled), Excursion switch, Gain switch, Plexi Mode (not modeled)

Power tubes: EL34 (earlier models were based on the 6L6 version)

# "People think Bogners are dark but they really aren't. The reason they seem that way is the pot tapers. Most people assume knobs should be set somewhere around noon. If you do this on a Bogner it's like turning the treble way down on a Marshall. Close your eyes and adjust the tone controls with your ears. Don't be afraid to turn them way up or way down." [https://forum.fractalaudio.com/posts/1031334]
# "Human nature is to put the knobs near noon. We are reticent to deviate much from noon. Amp designers exploit this and use different tapers to change the sound of their amps WITH THE KNOBS AT NOON. A prime example are Bogner amps. Everyone says "Bogner amps are dark". No they aren't. But he uses a Log10A taper for the treble pot. It's a standard Marshall tone stack. Usually a linear taper pot is used for the treble. The treble knob at 5.0 (noon) on a Bogner is equivalent to the treble knob at 1.0 on a Marshall. People put the knob at 5.0 and go "wow, this amp is dark". No it isn't. If you turned the treble up to 8 or 9 it would sound a lot like a Plexi but humans are reticent to turn the knobs to extremes. Amp designers know this and exploit it to give their amps a "signature sound"." [https://forum.fractalaudio.com/posts/1047275]
# "Our reference amp is a 20th anniversary and N is Bright Off, B1 is 150 pF and B2 is 1000 pF for both channels. The models default to B1. Change the Bright Cap value to 1 nF to emulate B2. Or better yet use your ears to select a value that sounds best." [http://forum.fractalaudio.com/threads/bogner-ecstasy-pre-amp-eq-b1-n-b2.109077/#post-1305047]
# (Class A) "Turn up Power Tube Grid Bias. In real life that is tough on tubes as it makes them run very hot." [https://forum.fractalaudio.com/threads/replicating-the-bogner-ecstasy-class-a-mode.145294/#post-1718463]
# "Bogner's are notoriously "slow" due to the low B+ voltage. Main reason I can't get along with them. You can try increasing the Variac." [https://forum.fractalaudio.com/threads/fast-pick-attack-amp.170370/post-2049711]
# "Most amps use a linear taper for the treble pot. Bogners use a log taper. So when the knob is at noon on a Bogner it's similar to 8 o'clock on most amps." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486/post-2067364]
# "The tonestack tapers in the Ecstasy model match the amp." [https://forum.fractalaudio.com/threads/5150-presence-knob.199908/page-9#post-2492617]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-euro-bogner-ecstasy.113278/ Yek's write-up]

==EURO BLUE MODERN==

==EURO RED==

==EURO RED MODERN==

==EURO UBER (Bogner Uberschall)==

[[file:uber.png|300px]]

Model:
* High gain channel

[[Cabinet models list | Cab:]] Bogner 4x12 Uberkab (G12-T75 and V30)

Gain, Master, Bass, Middle, Treble, Presence, Depth (only on Twin-Jet Uberschall)

Power tubes: EL34

# "People think Bogners are dark but they really aren't. The reason they seem that way is the pot tapers. Most people assume knobs should be set somewhere around noon. If you do this on a Bogner it's like turning the treble way down on a Marshall. Close your eyes and adjust the tone controls with your ears. Don't be afraid to turn them way up or way down." [https://forum.fractalaudio.com/posts/1031334]
# "Human nature is to put the knobs near noon. We are reticent to deviate much from noon. Amp designers exploit this and use different tapers to change the sound of their amps WITH THE KNOBS AT NOON. A prime example are Bogner amps. Everyone says "Bogner amps are dark". No they aren't. But he uses a Log10A taper for the treble pot. It's a standard Marshall tone stack. Usually a linear taper pot is used for the treble. The treble knob at 5.0 (noon) on a Bogner is equivalent to the treble knob at 1.0 on a Marshall. People put the knob at 5.0 and go "wow, this amp is dark". No it isn't. If you turned the treble up to 8 or 9 it would sound a lot like a Plexi but humans are reticent to turn the knobs to extremes. Amp designers know this and exploit it to give their amps a "signature sound"." [https://forum.fractalaudio.com/posts/1047275]
# "The feedback circuit is responsible for the behavior of the Presence and Depth controls. Certain Bogners and Diezels have a unique type of feedback circuit. There are no new parameters and nothing to do except twist the Presence and Depth knobs to your desired tone. Note that an Uberschall doesn't have a Depth knob. The default Depth value when you select the Euro Uber model is equivalent to the amp's fixed depth circuit." [https://forum.fractalaudio.com/posts/1159760]
# "Bogner's are notoriously "slow" due to the low B+ voltage. Main reason I can't get along with them. You can try increasing the Variac." [https://forum.fractalaudio.com/threads/fast-pick-attack-amp.170370/post-2049711]
# "Most amps use a linear taper for the treble pot. Bogners use a log taper. So when the knob is at noon on a Bogner it's similar to 8 o'clock on most amps." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486/post-2067364]
# "My Uber is a very early one and probably different than later models. It has the feedback of the 4-ohm tap whereas I've heard later versions have the feedback off the 8-ohm tap. To simulate this increase the Negative Feedback." [https://forum.fractalaudio.com/threads/bogner-uberschall-help.185084/post-2282705]
# "That model does the chugga-chugga better than Thomas the Tank Engine." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-00-release-candidate-beta-7.188382/post-2336626]

[https://forum.fractalaudio.com/threads/fractal-audio-amp-models-euro-uber-bogner-uberschall.113311/ Yek's write-up]

==FAS 6160 (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "Based on the PVH 6160 model but more open and less fizzy than the original amp. Also, a virtual choke has replaced the resistor found on the original’s power supply filter. This results in a bouncier feel."
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS BASS (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6550

# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS BROOTALZ (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6550

# "This amp was an accident. I was working on the Savage model and accidentally used the input stage from an SLO100. So it's the front end of an SLO100 with the back end of a Savage. It's probably an SLO100 power amp too but I'd have to check." [https://forum.fractalaudio.com/posts/1020502]
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]
# "Brootalz uses the Engl Savage presence network which reduces negative feedback as the control is turned down causing an increase in volume." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-5-cygnus-firmware-public-beta-2.170901/post-2059273]

[https://forum.fractalaudio.com/posts/1020502/ Yek's write-up]

==FAS BROWN (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: EL34

# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-brown-and-fas-brown.111974/ Yek's write-up]

==FAS BUTTERY (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model. In the original Cygnus release, it was replaced by an authentic Budda Twinmaster model. It returned in firmware 17 for the Axe-Fx III and later, and firmware for the FM3 and FM9.

Power tubes: EL84

# "I did the Buttery model by ear. I listened to some clips of Buddas (Matchbox 20... excellent!) and tweaked the model until I thought it sounded like one. Screwed around a little with the tube bias points until it had the right balance of harmonics and called it a day."
# "It's still the "ear tuned" version. I bought the amp but because it was so popular as-is I didn't dare change it." [https://forum.fractalaudio.com/threads/question-for-cliff-regarding-the-buttery-model.90943/#post-1095174]
# "Buttery is a virtual amp model that was created by ear. There is no physical, real amp that exists upon which it was based. It's like the FAS models. They exist solely in the virtual world. They all still benefit from the Quantum stuff though as they use the same underlying algorithms for the tube modeling. The amp model, regardless of how accurate it is (and it's probably grossly inaccurate as I never compared it to any actual amp) is very popular and that's why it was never matched to any real amp." [http://forum.fractalaudio.com/threads/question-for-cliff-regarding-the-buttery-model.90943/page-2#post-1283301]
# "Yeah, Buttery was a legacy model from the first Axe-Fx." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-12-cygnus-firmware-public-release-candidate.172027/post-2075782]
# "The previous model wasn't based on any real amp. It was a "FAS Original". [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-12-cygnus-firmware-public-release-candidate.172027/post-2076487]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-buttery-budda-twinmaster.112228/ Yek's write-up]

==FAS CLASS-A (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: EL84

# "A “Blackface” preamp into a cathode-biased 6L6 power amp with no negative feedback. This was a happy accident when originally modeling the Carr Rambler in the beta version of this release. Several mistakes were made in the model prior to MIMIC’ing the amp but the model was so well liked that we decided to make it into its own custom amp model."
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[https://forum.fractalaudio.com/posts/1355719/ Yek's write-up]

==FAS CRUNCH (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: EL34

# "Our take on the ultimate British-sounding amp. More dynamic and open than a Plexi, but with more gain."
# "My take on the ultimate Plexi." [https://forum.fractalaudio.com/threads/axe-fx-ii-firmware-9-public-beta.59414/page-22#post-744829]
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS EXPRESS (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Notes: see Wrecker Express

Power tubes: EL34

# "Based on hypothetical modifications to a Trainwreck Express."
# "It has a master volume. That's one of the "mods"." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-11-02-public-beta-5-beta_4.157025/post-1875792]
# (about the Trainwreck Express) "That amp exhibits a lot of blocking distortion (in the phase inverter) due to its design. You can reduce this via either the PI Bias Excursion or Master Bias Excursion parameters. Another option is to use the FAS Express model which puts some resistors between the last triode stage and the PI to reduce the bias excursion." [https://forum.fractalaudio.com/threads/blocking-distortion-found-in-trainwreck-express.182895/post-2247268]

==FAS HOT ROD (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: EL34

# "FAS Hot Rod is my version of what a modded Marshall should be. I find the BE/HBE a little too boomy and scooped. Bogners are too dark. Splawns don't have enough compression. Etc. So it's my take on a hot-rodded Marshall tone." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-1-02-firmware-release.106477/page-4#post-1274103]
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS LEAD 1 (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS LEAD 2 (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: EL34

# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS MODERN (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "This model is my interpretation of the ideal modern metal tone. In the digital realm we are not constrained by the limitations that face tube amp designers so we are free to implement designs that would be nearly impossible with a tube amp. The Axe-Fx II modeling includes a variety of general purpose filters that I can place anywhere in the signal path. So I put some second-order filters in there to tighten up the tone. Implementing second-order filters in a real tube amp is difficult and costly so is rarely seen." [https://forum.fractalaudio.com/posts/715029]
# "It's loosely based on a Recto but with tighter bass." [https://forum.fractalaudio.com/threads/fw-6-0-rectifier-obsevation.51197/#post-658849]
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]
# (about the MESA Rectifier) "Personally I hate the 39K resistor. It biases the stage much too cold for my tastes. It prevents blocking distortion but there are better ways to do it IMO. The FAS Modern model is similar but biases the stage more towards the center." [https://forum.fractalaudio.com/threads/new-amp-models.159097/post-1901438]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS MODERN II (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "This is a tighter version of the popular FAS Modern model with a 5150-style bass boost in the tone stack."
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS MODERN III (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS RHYTHM (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "Combines the best features of the British (Marshall) and USA (Mesa) crunch models."
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS SKULL CRUSHER (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "The nastiest, most brutal amp model to ever escape from the seventh circle."
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

==FAS WRECK (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Notes: see Wrecker Express

Power tubes: EL34

# "Based on the original WRECKER 1 model from the Axe-Fx Ultra."
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]
# "FAS Wreck model is better than any Trainwreck or Wreck-style amp IMO. All the good bits without the bad stuff." [https://forum.fractalaudio.com/threads/brad-paisley-z-wreck-with-blue-and-gold-2x12-cabinet.163617/post-1961880]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FOX ODS (Fuchs Overdrive Supreme 50)==

[[file:fuchs.jpg|300px]]

Models:
* ODS: Deep switch OFF, Pre Amp Bypass ON (no tone controls)
* ODS Deep: Deep switch ON, Pre Amp Bypass ON (no tone controls)

[[Cabinet models list | Cab:]] Fuchs 2x12 (Eminence)

Gain, High (pull: mid boost), Mid (pull: gain boost), Low, Input, Brite switch, Deep switch, Rock/Jazz switch (not modeled), Master, Accent (= Presence)

Power tubes: 6L6

# "Supposedly a Dumble ODS clone but our reference amp has way more gain than our Dumble." [https://forum.fractalaudio.com/posts/1174814]
# "The topology of the Fuchs is pure Dumble. The difference is that there is less padding between stages 2 and 3 (IIRC). So it's a high-gain Dumble. Personally I don't think the Dumble topology lends itself to that much gain but I didn't design the amp. If you like the base Dumble sound but want a little more gain without the fuzziness of a Fuchs try the Carol-Ann models." [https://forum.fractalaudio.com/threads/fuchs-ods-in-cygnus.172291/post-2081523]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fox-ods-fuchs-overdrive-supreme.113514/ Yek's write-up]

==FOX ODS DEEP==

==FRIEDMAN BE 2010 (Friedman BE)==

[[File:BE.jpg|300px]]

Old models (before "Cygnus" amp modeling):

* BE: based on old Marsha model, BE mode
* BE C45: based on Mark Day's BE-100, C45 switch engaged
* BE V1: based on Mark Day's BE-100, voice: right position (less mids)
* BE V2: based on Mark Day's BE-100, voice: left position (more mids)
* HBE: based on old Marsha model, HBE mode
* HBE 2018: based on 2018 BE-100, HBE mode
* HBE 2018 C45: based on 2018 BE-100, HBE mode, C45 switch engaged
* HBE V1: based on Mark Day's BE-100, HBE mode, voice: right position (less mids)
* HBE V2: based on Mark Day's BE-100, HBE mode, voice: left position (more mids)

Current models ("Cygnus" amp modeling):

* BE 2010: based on Friedman BE-100 from 2010 (probably the "Marsha" edition)
* BE C45: based on later BE-100, C45 switch engaged
* BE V1: based on later BE-100, voice in left position
* BE V1 Fat: based on later BE-100, voice in left position, FAT switch engaged
* BE V2: based on later BE-100, voice in middle position (brightest)
* BE V3: based on later BE-100, voice in right position
* HBE 2010: based on Friedman BE-100 from 2010 (probably the "Marsha" edition), HBE mode
* HBE C45: based on later BE-100, C45 switch engaged
* HBE V1: based on later BE-100, voice in left position
* HBE V1 Fat: based on later BE-100, voice in left position, FAT switch engaged
* HBE V2: based on later BE-100, voice in middle position (brightest)
* HBE V3: based on later BE-100, voice in right position

[[Cabinet models list | Cab:]] Friedman 4x12 (V30 and/or G12M)

Gain, Master, Bass, Middle, Treble, Presence, Bright (clean channel only). BE-100 Deluxe: Thump control. Switches: FAT, C45 (treble boost), SAT (model: SAT), 3-position Voice switch (changes the top-end response of the dirty channels)

Power tubes: EL34

# (before Cygnus) "The old model is an original, hand-built "Marsha". It's MUCH darker than Mark's newer BE/HBE. In fact it's so dark and boomy I emailed Dave to make sure the amp was built correctly. Turns out the snubber cap is the wrong value. But even with the snubber cap corrected it's still very dark and boomy which made me question as to whether there are other components that are incorrect. So we decided to redo the model based on Mark's amp which is the amp that was the demo model at Tone Merchants." [http://forum.fractalaudio.com/threads/the-new-hbe.112717/#post-1348497]
# (before Cygnus) "The models are based on two different amps. The V1 and V2 are based on Mark Day's BE100. The other models are based on our original "Marsha". Like most boutique amp makers Friedman's designs have evolved over time with changes to the circuit. The original Marsha we have is dark and bassy with lots of lowpass filtering. The newer amp is brighter and tighter. For now note that V1/V2 refer to the newer amp and represent the position of the Voicing switch." [http://forum.fractalaudio.com/threads/which-are-the-new-be-hbe-models.114510/#post-1369754]
# "The BE/HBE has a fixed depth circuit that gives a lot of bass boost. The model defaults the Depth to match this." [https://forum.fractalaudio.com/posts/833169]
# "If you want more clarity in the low mids from the BE/HBE reduce Negative Feedback. Friedman's designs are a bit odd in that he takes the feedback off the speaker jack rather than off a transformer tap. The mating cab for a BE/HBE is 16 ohms which means lots of feedback. But if you connect the amp to an 8 ohm load there is about 30% less feedback. The amp will sound tighter and clearer in the low mids." [http://forum.fractalaudio.com/threads/underrated-amp-models.109894/page-2#post-1316362]
# "The design is weird as the negative feedback is taken off the speaker jack. So if you use a 16-ohm speaker you get more feedback (and much more bass) than if you use an 8-ohm speaker. The model is based on using the matching cab. It's too much bass for me so I turn down the Depth and reduce Negative Feedback a bit." [http://forum.fractalaudio.com/threads/question-about-the-friedman-amp-presets.110511/#post-1322655]
# "I always lower the negative feedback. Friedman amps are a bit strange because the negative feedback is taken off the speaker jack instead of one of the transformer taps. The matching cabs are 16 ohms but if you use an 8-ohm cab you'll get 30% less feedback." [http://forum.fractalaudio.com/threads/couple-of-observations-about-the-friedmans-in-7-02.126030/page-2#post-1504343]
# "C45 is a treble boost on the input. Put a filter block before the amp as follows: Type: Tilt EQ - Freq: 700 Hz - Gain: 4.5 dB" [http://forum.fractalaudio.com/threads/friedman-hbe-with-c45-switch.110686/#post-1324975]
# [http://forum.fractalaudio.com/threads/friedman-be-100-hbe-channel-vs-the-axe-fx-3-hbe-model.144911 Discussion about the Bass control]
# "Some amps have a fixed depth circuit, e.g. 5153, Freidman BE/HBE, Dirty Shirley, TripTik, Tucana, et. al. In these cases the Depth knob will default to a value that corresponds to the fixed circuit." [https://forum.fractalaudio.com/threads/lets-talk-about-the-depth-control.88747/#post-1071598]
# "When you watch a video Dave himself turns the bass way up. Steve Stevens and Jerry Cantrell turn the bass way up too. If I did that with my guitar it would be a muddy mess. Puzzling to me because the BE has a fixed depth circuit and a significant amount of negative feedback so there is quite a bit of bass boost in the power amp as well." [https://forum.fractalaudio.com/threads/friedman-be-100-hbe-channel-vs-the-axe-fx-3-hbe-model.144911/#post-1714308]
# "The BE has very light power supply filtering like old Plexis." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-14-01.165716/post-1990715]
# (Cygnus) "All the Friedman models are now based on the latest amp. Our reference amp was made in 2018 and has the feedback off the 4-ohm tap." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2047861]
# (Cygnus) "That's the way the HBE channel sounds. The problem with the design is that the drive control is located between the 3rd and 4th gain stages. Too far back IMO. This causes a lot of distortion and also a lot of bias excursion before the drive control with no way to control it. In most amps the drive control is located after the first stage (input buffer). Some amps have a second drive control, typically called an Overdrive, located further downstream which allows you to balance the pre- and post distortion. One way to deal with it is to decrease the Input Trim and increase the Input Drive. You can also try reducing the Master Bias Excursion but that won't get rid of the pre-drive control distortion. A lot of people like this sound though. It has a certain stringy quality that many people find desirable." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-10-cygnus-firmware-public-beta-7.171198/post-2062927]
# (Cygnus) "There are now three "Voicings": V1, V2 and V3 corresponding to the three positions of the Voice switch." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486]
# Based on latest version of amp. There are now three "Voicings": V1, V2 and V3 corresponding to the three positions of the Voice switch." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486/post-2067182]
# "The BE100 design has changed over the years. Dave is constantly fiddling with things. The original "Marsha" (which became the BE100 after the cease-and-desist) had the Gain control after the second stage. Later versions have the gain control after the third stage so even if you turn the gain down you may still get some distortion. There were also numerous changes to component values, feedback tap, etc., etc. Our models are authentic recreations of the two particular versions we have. Whether those versions match your particular version is unknown." [https://forum.fractalaudio.com/threads/friedman-amps-in-axefx3-vs-helix.197851/post-2458958]
# "Here's the story with the Friedman models: The BE/HBE have the gain pot before the last gain stage. This is a poor design choice IMO because you're always getting distortion even if you turn the gain down. Bad gain-staging IOW. Before the Cygnus firmware I was more about "make it sound good" rather than accuracy. Hence, non-authentic pot tapers, etc. So I moved the gain pot forward a stage because it sounded better to me that way. I left the treble peaker before the last stage and just moved the gain pot forward. More like a classic Marshall. But as our products became more and more popular the cries of "it doesn't sound exactly like my amp" became more frequent. So Cygnus became all about authenticity. There are still some remnants of Ares left over (i.e., pot tapers) that we have been correcting over time as we discover them but now the models behave like the amps and my tweaks to make things "sound better" have been removed, for better or worse." [https://thegearforum.com/threads/fractal-talk.2745/post-151874]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-friedman-be-and-hbe-friedman-be-100.113559 Yek's write-up]

==FRIEDMAN BE C45==

==FRIEDMAN BE V1==

==FRIEDMAN BE V1 FAT==

==FRIEDMAN BE V2==

==FRIEDMAN BE V3==

==FRIEDMAN HBE 2010==

==FRIEDMAN HBE C45==

==FRIEDMAN HBE V1==

==FRIEDMAN HBE V1 FAT==

==FRIEDMAN HBE V2==

==FRIEDMAN HBE V3 ==

==FRIEDMAN SMALL BOX (Friedman Smallbox)==

[[File:smallbox.jpg|300px]]

Model:
* Channel 2

[[Cabinet models list |Cab:]] Friedman 2x12 (G12M)

Gain, Master, Bass, Middle, Treble, Presence, Bright switch (channel 1 only, not modeled)

Power tubes: EL34

# "The schematic shows a 2.2 nF coupling cap off the first stage but the actual amp has a 4.7 nF. 2.2 nF would mean less bass. I can only assume the amp was built to the latest specs. If an amp model is "G3'd" it is deadly accurate. I go through the amps and check the values of each component, measure the voltages, compare the frequency response to the model, etc., etc., etc. If the model is too bassy for you then you would find the real amp too bassy, or at least our particular reference model." [http://forum.fractalaudio.com/threads/friedman-sm-box-smallbox.99488/#post-1193341]
# "If you want more clarity in the low mids (...) reduce Negative Feedback. Friedman's designs are a bit odd in that he takes the feedback off the speaker jack rather than off a transformer tap. (...) The amp will sound tighter and clearer in the low mids." [http://forum.fractalaudio.com/threads/underrated-amp-models.109894/page-2#post-1316362]
# "The design is weird as the negative feedback is taken off the speaker jack. So if you use a 16-ohm speaker you get more feedback (and much more bass) than if you use an 8-ohm speaker. (...) It's too much bass for me so I turn down the Depth and reduce Negative Feedback a bit." [http://forum.fractalaudio.com/threads/question-about-the-friedman-amp-presets.110511/#post-1322655]
# "I always lower the negative feedback. Friedman amps are a bit strange because the negative feedback is taken off the speaker jack instead of one of the transformer taps. The matching cabs are 16 ohms but if you use an 8-ohm cab you'll get 30% less feedback." [http://forum.fractalaudio.com/threads/couple-of-observations-about-the-friedmans-in-7-02.126030/page-2#post-1504343]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-friedman-sm-box-friedman-small-box.113604/ Yek's write-up]

==FRYETTE D60 LESS (Fryette Deliverance 60)==

[[file:fryette.jpg|300px]]

Models:
* "Less" mode
* "More" mode

[[Cabinet models list | Cab:]] Fryette 4x12 P50E (Fane F70G)

Gain 1, Gain 2, Master, Bass, Middle, Treble, Presence, Depth, More/Less switch

Power tubes: KT88

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fryette-d60-fryette-deliverance-60.113657/ Yek's write-up]

==FRYETTE D60 MORE==

==GIBTONE SCOUT (Gibson GA17RVT Scout)==

[[file:gibson.jpg‎|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Gibson 1x10

Volume, Tremolo, Reverb (not modeled)

Power tubes: 6AQ5

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-gibtone-scout.113698 Yek's write-up]

==HERBIE CH2+ (Diezel Herbert)==

[[File:herbert.jpg|300px]]

Models:
* Channel 2+ of original Herbert (based on Marshall JC800)
* Channel 2- of original Herbert (based on Marshall Plexi)
* Channel 3 of original Herbert (based on Diezel VH4)
* Channel 2+ of black-panel Herbert MK III

[[Cabinet models list |Cab:]] Diezel 4x12 (V30, G12-K100)

Gain (not on channel 1), Bass, Middle (1 kHz), Treble, Master, Presence (> 3kHz), Deep (120Hz), Mid-Cut (not modeled), Gain Boost switch (not modeled)

Power tubes: KT66

# "The reason Diezels compress so much is due to the cathode follower design. You can reduce the compression in the models by lowering the Compression parameter in the Cathode Follower section." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-14-00.165157/post-1981183]
# (reproducing the Mid Cut function) "Use a Peak EQ filter at 400 Hz with a Q of 1.4. Decrease its Gain until the desired scoop is achieved. Play with the Q to set the width of the scoop." [https://forum.fractalaudio.com/posts/1144887]
# "Humans perceive high frequency thermal noise as hiss. The more gain the more hiss. Diezel's have a lot of filtering. Large grid stoppers, plate capacitors, etc. This reduces the bandwidth which lowers the hiss. Camerons are pretty much wide open. Small grid stoppers or bypass caps on the grid stoppers, no plate caps, etc." [https://forum.fractalaudio.com/threads/why-lower-gain-cameron-ccv-amp-model-feels-more-noisy-than-much-higher-gain-herbie-3.188658/post-2339783]
# (the new Herbert model in firmware 21 for the Axe-Fx III) "I like it a lot more than the old version of the amp. The original Herbert is too dark, fuzzy, compressed and muddy IMO. Sounds great playing alone but when I play along with a recording it just gets lost. The new Herbert is tighter and sits in the mix better." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-00-release-candidate-2-beta-8.188778/post-2340412]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-herbie-diezel-herbert.113745 Yek's write-up]

==HERBIE CH2-==

==HERBIE CH3==

==HERBIE MK3 (Diezel Herbert MKIII)==

==HIPOWER BRILLIANT (Hiwatt DR103)==

[[file:hiwatt.jpg|300px]]

Models:
* Normal channel
* Brilliant channel
* Normal and Brilliant channels jumpered

[[Cabinet models list |Cab:]] Hiwatt 4x12 (Fane)

Volume, Master, Bass, Middle, Treble, Presence

Power tubes: EL34

# "I have a 1974 Hiwatt DR-103. The model is based on that. It is one of the Harry Joyce, Hylight era models. Still has the original tubes. Closet find and sounds glorious." [https://forum.fractalaudio.com/posts/497513]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-hipower-hiwatt-dr103.113789/ Yek's write-up]

==HIPOWER JUMPED==

==HIPOWER NORMAL==

==HOT KITTY (Bad Cat Hot Cat 30)==

[[file:hotcat.jpg|300px]]

Model:
* High gain channel

[[Cabinet models list | Cab:]] BadCat 1x12 (proprietary Celestion)

Gain, Edge (not modeled), Level, Bass, Mid-range switch (not modeled), Treble, Brilliance, Master

Power tubes: EL34

# "Brilliance is their name for Hi-Cut. I set the Edge control to where I thought it sounded best. It essentially does the same thing as the Bright knob though less precise."
# "The amp has a Hi Cut but it's labeled Brilliance. It's wired backwards so turning it CW gets brighter." [http://forum.fractalaudio.com/threads/hotkitty-1-05-is-nasty-as-hell.107651/page-2#post-1289111]
# "Those amps make a lot of IMD. The real amp does the same thing but you wouldn't normally use a subwoofer with one." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-00-public-beta-2.124097/page-14#post-1477200]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-hot-kitty-bad-cat-hot-cat-30.113829/ Yek's write-up]

==JMPRE-1 CLEAN 1 (Marshall JMP-1 preamp)==

[[image:Cliff JMP-1.jpg|300px]]

Models:
* Clean 1
* Clean 1 with Bass Shift engaged
* Clean 2
* Clean 2 with Bass Shift engaged
* OD1 mode
* OD1 mode with Bass Shift engaged
* OD2 mode
* OD2 with Bass Shift engaged

Volume, Gain, Bass, Mid, Treble, Presence (preamp), Bass shift, Depth

Power tubes: EL34

# "The power amp is based on a typical Marshall 100 watts power amp of the same era."
# [before firmware 19.02 for the Axe-Fx III] "The JMP-1 tone controls have more range than the actual preamp. The preamp has about +/- 8 dB for each tone control while the model has the standard +/- 12 dB."
# "Actually a JMP-1 is unique in that the tone controls do not interact. Most guitar amps use a passive "tone stack" where the controls interact. The JMP-1 has a fixed passive tone stack followed by an active 4-band EQ." [https://forum.fractalaudio.com/threads/is-the-brit-pre-good-enough.132950/#post-1573028]
# (Def Leppard) "The amp model you are looking for is "JMPre-1 OD1". Some cabs you might like to try with that amp model: Factory 2 #97 2x12 RECTO V60 57 OH, Factory 2 #995 4x12 UBER V30 57 OFF-AXIS, Factory 2 #530 4x12 BRIT 70s GB 121 I." [https://forum.fractalaudio.com/threads/are-phil-and-viv-using-brit-pre-or-jmpre-1-on-the-iii.139394]
# Firmware 19.02 and later for the Axe-Fx III:
#* Added JMPRE-1 Output EQ type to Amp block. This type replicates the active EQ used in the JMP-1 preamp.
#* Added Clean models.
#* The real amp has a fixed, passive tone stack with an active 4-band EQ. Therefore, the Bass/Mid/Treble controls when using Authentic Tone Controls are mapped to the Graphic EQ. Clean channels only: the passive tone stack itself, however, is adjustable. With all controls at noon the tone stack is equivalent to the real amp’s fixed tone stack. You can access these controls using the Ideal Tone Controls or via Axe-Edit.

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-pre-and-brit-jmpre-1-marshall-jmp-1.112139/ Yek's write-up]

==JMPRE-1 CLEAN 1 BASS SHIFT==

==JMPRE-1 CLEAN 2==

==JMPRE-1 CLEAN 2 BASS SHIFT==

==JMPRE-1 OD1==

==JMPRE-1 OD1 BASS SHIFT==

==JMPRE-1 OD2==

==JMPRE-1 OD2 BASS SHIFT==

==JR BLUES (Fender Blues Junior)==

[[file:bluesjr.jpg|300px]]

Models:
* Fat switch OFF
* Fat switch ON

[[Cabinet models list | Cab:]] Fender 1x12 (Eminence, Jensen C12N, P12R)

Bass, Middle, Treble, Gain, Volume, FAT button (boosts gain and midrange frequencies), Reverb (not modeled)

Power tubes: EL84

# "The Blues Jr. amp has a fixed presence circuit." [https://forum.fractalaudio.com/threads/question-of-proper-axe-eq-values-for-amps-that-dont-have-them.67260/#post-828733]
# "They're actually pretty decent little amps and sound great when cranked." [https://forum.fractalaudio.com/threads/forgot-how-loud-tube-amps-are.170551/post-2052934]
# "The Master Volume in a Blues Jr. is linear taper. This is ridiculous as it makes it very difficult to find the sweet spot. The model uses an audio taper instead which makes finding the sweet spot easier." [https://forum.fractalaudio.com/threads/cygnus-is-absolutely-magnificent.173225/post-2096570]
# "Blues Jr. is a very colored preamp. The best you can do is turn Bass and Treble to zero and Mid all the way up. That will make it somewhat flat but you still have the bright cap on the drive and the bandpass between the preamp and power amp." [https://forum.fractalaudio.com/threads/negative-results-playing-my-fm9-through-a-blues-jr.189057/post-2343390]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-jr-blues-fender-blues-junior.113925/ Yek's write-up]

==JR BLUES FAT==

==JS410 CRUNCH ORANGE (Marshall JVM410HJS)==

[[file:js.jpg|300px]]

Models:
* Crunch Orange: based on a JCM 2203
* Crunch Red: based on a modded JCM 2203
* Lead Green: like the OD1 channel on the original JVM410H
* Lead Orange: more gain
* Lead Red: even more gain

[[Cabinet models list | Cab:]] Marshall 4x12 (V30 and G12H)

Volume, Gain, Bass, Middle, Treble, Master, Presence, Resonance, Gate (not modeled), Mid-Shift (around 650hz off and around 500hz on, not modeled)

Power tubes: EL34

# "Joe said he puts all the tone controls at around 10:00." [http://forum.fractalaudio.com/threads/jvm-js-in-the-tonestack.109946/#post-1316690]
# "The JVM has a huge plate resistor on the cathode follower, the JS does not." [https://forum.fractalaudio.com/threads/jvm-sounding-weird.150157/page-2#post-1785256]
# "The model is based on Joe's personal amp. He sent it to me. When I entered the values from the schematic it didn't match. The tapers of the controls were different and there were some other differences. I can only assume that his personal amp is different than production models. This is often the case as production models are designed to be inexpensive to build (i.e., using control tapers that are used in other models to reduce inventory, etc.). Another possibility is there were changes made during production. It is not uncommon for amps to have changes made to the circuitry over the production run. For example, the Blues Jr. has had numerous revisions. The first ones sound nothing like the later models. This is sometimes done due to perceived customer reaction ("The amp is too dark" or "The amp is too harsh"). Simply adjusting BMT should get you what you want. Control tapers make a big difference. For example, a Bass pot that is a linear taper would need to be set to 1.0 to match a Log10A taper at 5.0." [https://forum.fractalaudio.com/threads/marshall-jvm410hjs-real-amp-versus-axe3.197259/post-2450481]
# Firmware 23: "Updated all JS410 Lead models based on a current production JVM410HJS. The Crunch models were tested and did not require updating."
# (Was there much different between the production Satriani amp and his own one?) "Yes, they measure quite differently." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-23-00-public-beta-1.198479/post-2467475]
# (firmware 24.00) "Added Global MV control to JS410 amp models. Master Volume has been renamed Channel MV. These two master volume controls can be used to balance the tone into the power amp (as in the real amp). The Channel MV decreases the high frequencies as it is turned down whereas the Global MV is transparent."

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-js410-marshall-jvm410hjs.114030/ Yek's write-up]

==JS410 CRUNCH RED==

==JS410 LEAD GREEN==

==JS410 LEAD ORANGE==

==JS410 LEAD RED==

==JAZZ 120 (Roland Jazz Chorus 120)==

[[File:jc120.jpg|300px]]

Model:
* Single model

[[Cabinet models list| Cab:]] Roland 2x12 ("silver" AlNiCo)

Volume, Bass, Mid, Treble, Bright switch. Not modeled: Distortion, Chorus, Reverb

Power tubes: none (solid-state)

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-jazz-120-roland-jazz-chorus-120.113865/ Yek's write-up]

==LEGEND 100 (Carvin Legacy VL100)==

[[file:legacy.jpg|300px]]

Formerley: CALI LEGGY (VL100) and LEGATO 100 (VL300)

Legacy models:
* Legend 100: lead channel of Carvin VL100 Legacy
* Legend 100 II: channel 3 of Carvin VL300 Legacy 3

[[Cabinet models list | Cab:]] Carvin 2x12 or 4x12 (V30)

VL100: Presence, Treble (11kHz), Mid (650Hz), Bass (80Hz), Drive, Volume

VL300: Bass, Middle, Treble, Presence, Drive, Volume, Master, Boost (not modeled), Reverb (not modeled), Gain switch (not modeled)

Power tubes: EL34

# "The thing that makes a Legacy unique is the tone stack. It uses a "James" tone stack which is more like hi-fi tone controls." [https://forum.fractalaudio.com/threads/thank-you-fractal-for-the-leggy-legacy-model-its-great.47586/#post-620139]
# "Adds the "Legato 100" model based on Steve Vai's Legacy 100. This model is unique in that it uses a Baxandall (sometimes called a "James") tone stack. More often used on tube hi-fi gear the controls are less interactive than a typical guitar amp tone stack and impart a different tonal quality." [https://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-4-01-beta.119527/]
# "The Legato 100 is based on a one-of-a-kind version owned by a certain Californian guitar player. It is a very dark amp. Part of this is due to the tapers on the tone pots. With everything at noon the tone stack looks like a highshelf with a good amount of high frequency cut. The tone stack is a Baxandall which is more common in hi-fi gear than guitar amps. It lends a unique character to the tone." [https://forum.fractalaudio.com/posts/1426142]
# "SV's personal settings are: Drive: 7.5, Bass: 6, Mid: 4, Treble: 8, Presence: 8. I had to increase the Mid control on the model to about 5 to match the amp which indicates the mid pot on the amp was greater than spec. This is not unusual. Typical consumer-grade pots have pretty poor tolerance in both end-to-end resistance and resistance at the midpoint." [https://forum.fractalaudio.com/posts/1429558]
# (Cygnus) "Carvin Legacy 100. Legend II is channel 3 from the Legacy 3." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-12-cygnus-firmware-public-release-candidate.172027/post-2075753]
# "What is happening is the power amp is oscillating at that very low frequency cabinet resonance. This occurs because the Legacy has so much negative feedback (12 dB, which is the highest of any amp I've ever modeled). Combined with the smallish output transformer there is a loss of phase margin at low frequencies which causes the power amp to become unstable. The Rumble cab is unique in that it is ported and has two different types of speakers in it. This causes a double resonance and one of the resonances is at a very low frequency. For typical power amps with reasonable amounts of feedback this isn't an issue." [https://forum.fractalaudio.com/threads/bizzare-yet-interesting-legend-amp-model-possible-issue.173492/post-2101586]
# "The tonestack in a Legacy is a James. A Baxandall is active." [https://forum.fractalaudio.com/threads/have-we-reached-the-end-of-new-amp-models-in-the-axe-3.184271/post-2483056]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-cali-leggy-and-legato-100-carvin-legacy-vl100.112449 Yek's write-up]

==LEGEND 100 II (Carvin Legacy VL300)==

==MATCHBOX CHIEFTAIN 1 (Matchless Chieftain)==

[[File:chieftain.jpg|300px]]

Formerly: BOUTIQUE 1 and BOUTIQUE 2

Models:
* Single channel
* Boosted for more gain and high-frequency emphasis

[[Cabinet models list |Cab:]] Matchless 2x12 (G12H)

Volume, Master, Bass, Mid, Treble, Brilliance

Power tubes: EL34

# "The secret of the Chieftain is the split cathode bias. Most "Class-A" amps use a shared cathode bias but the Chieftain uses separate cathode bias networks which results in less bias shift so there's less fizz." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-03.158240/post-1895726]
# "The "Treble" knob on the Chietain model is actually Preamp Presence. It's not part of the tone stack. It's a separate presence network at the output of the last stage. They just call it treble." [https://forum.fractalaudio.com/threads/matchbox-chiefman-factory-preset-treble-knob-modifier-weirdness.173485/post-2100361]
# "The Treble control in a Chieftain is actually a "Preamp Presence" control, similar to the Presence control in a Dual Rectifier in Modern mode. It is separate from the tone stack and located later in the gain stages. The tone stack has no treble control." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-00.189017/post-2344358]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-boutique-matchless-chieftain.111832/ Yek's write-up]

==MATCHBOX CHIEFTAIN 2==

==MATCHBOX D-30 (Matchless DC-30)==

[[File:dc30.jpg|300px]]

Models:
* Channel 1 (12AX7 preamp tubes), Master Volume bypassed
* Channel 2 (EF86 preamp tubes), Master Volume bypassed

[[Cabinet models list | Cab:]] Matchless 2x12 (25w G12M and 30w G12H)

Channel 1: Volume, Bass, Treble, Cut, bypassable Master

Channel 2: Volume, Tone, Cut, bypassable Master

Power tubes: EL84

# "The DC-30 is basically an AC-30 copy. The voltages are a bit different but the topology is nearly identical. However, IMO, it does sound better. Not sure why. Perhaps the better quality components. AC-30's have kind of crappy OTs." [https://forum.fractalaudio.com/posts/968982]
# (channel 2) "The switch selects the coupling capacitor between the EF86 and the volume pot." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-9-00-beta.130981/page-11#post-1552400]
# "Added “Matchbox D-30 EF86” amp model. While the real amp has a six-position Tone switch, the model has a continuously variable tone control. Note that the Tone control is mapped to the Bass control in Ideal mode as the Tone switch is essentially a bass cut control."
# “The new DC-30 model may have dethroned the mighty AC-20 as my favorite "Class A" model.” [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-11-01.156108/post-1858859]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-matchbox-d-30-matchless-dc-30.114129/ Yek's write-up]

==MATCHBOX D-30 EF86==

==MR Z HWY 66 (Dr. Z Route 66)==

[[file:route66.jpg|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Dr. Z 2x12 (V30 and G12H)

Volume, Bass, Treble

Power tubes: KT66

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-mr-z-hwy-66-dr-z-route-66.114166/ Yek's write-up]

==MR Z MZ-38 (Dr. Z Maz 38 SR)==

[[File:maz38.jpg|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Dr. Z 1x12 (G12H)

Volume, Master, Bass, Mid, Treble, Cut, Reverb on some models (not modeled)

Power tubes: EL84

# "Dr. Z is the quintessential country amp." [https://forum.fractalaudio.com/posts/828934]"
# "IMO the designs are poor because... wait for it... they exhibit a papery buzz. The problem with most cathode biased Class A amps is, 1: they aren't really Class A (more like hot Class AB) and 2: They go into Class B operation when they are overdriven. The cathode capacitor charges up and the bias point shifts dramatically. This causes lots of crossover distortion (papery buzz). It's worse on lower notes because lower notes have more energy and charge the cap more. The is probably the reason Leo Fender switched to fixed bias amps with negative feedback. Fixed bias is just that, the bias point is fixed so the amp doesn't shift into Class B operation when overdriven (not as much anyways, depends on the bias circuit, grid stoppers, etc.). Negative feedback linearizes the amp and reduces the crossover distortion (at the expense of gain). That's why the buzzing went away when you increased negative feedback. Crossover distortion is a unique sound. For cleaner sounds it tends to be objectionable. For overdriven sounds some find it desirable. EVH ostensibly liked his amps biased cold to get some crossover distortion. There are even some amps that have circuits to intentionally generate crossover distortion. Some distortion pedals also do this. Lowering the Cathode Resistance reduces the crossover distortion as it keeps the amp in Class A operation longer but the tubes run hotter and don't last as long. This is not a problem with our virtual amps though. I forget the actual values but I'm pretty certain if you look at the Cathode Resistance value for those amps it's pretty high. This means the amps are biased somewhat cold to begin with and shift to very cold as soon as overdriven. Then there's shared vs. split cathode. If you look at the schematics on the web the Maz-38 is shared cathode. I could never get the model to sound exactly like our reference amp. Finally I traced the entire circuit and our particular amp is a split cathode. As soon as I changed the model to split cathode it was spot on. This is not exposed to the user though (there's a hidden shared/split switch). Our particular amp says "Humbucker" inside the chassis. Not sure if the difference in the cathode circuit is because Dr. Z likes split cathode for humbucking guitars or what." [https://forum.fractalaudio.com/threads/papery-buzz-under-some-models.149193/page-2#post-1772639]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-mr-z-mz-8-and-mz-38-dr-z-maz-8-and-maz-38-sr.114213/ Yek's write-up]

==MR Z MZ-8 (Dr. Z Maz 8)==

[[File:maz8.jpg|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Dr.Z 1x12 (G12H)

Volume, Master, Bass, Mid, Treble, Cut, Reverb (not modeled), Pentode/Triode switch (not modeled)

Power tubes: EL84

# "Dr. Z is the quintessential country amp." [https://forum.fractalaudio.com/posts/828934]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-mr-z-mz-8-and-mz-38-dr-z-maz-8-and-maz-38-sr.114213/ Yek's write-up]

==NUCLEAR-TONE (Swart Atomic Space Tone)==

[[file:swart.jpg|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Swart 1x12 (Mojotone BV-25m)

Volume, Tone, Tremolo, Reverb (not modeled)

Power tubes: 6V6

# "It's unique character comes from the PI. It's a cathodyne phase inverter so it doesn't drive the grids as hard." [https://forum.fractalaudio.com/posts/828241]
# "The real amp is known for it's tremolo so that's why we used the bias trem on the preset. Bias trem works by modulating the power tube grid bias. One of the side-effects is that the effect becomes less pronounced as you play harder which makes it basically "auto ducking". Also since it's modulating the bias it gives an almost Univibe like effect since the phase changes a bit too." [http://forum.fractalaudio.com/threads/patch-62-nuclear-tone-weird-tremolo-effect.122258/#post-1454602]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-nuclear-tone-swart-atomic-space-tone.113700/ Yek's write-up]

==ODS-100 CLEAN (Dumble Overdrive Special)==

[[File:dumble.jpg|300px]]

Models:
* Clean: based on HRM circuit, Clean channel
* Ford: based on schematics of Robben Ford's #102 Dumble, Overdrive channel, Pre Amp Boost (PAB) OFF
* Ford PAB: same as Ford model, PAB ON (bypasses the tone controls), Mid switch OFF
* Ford PAB Mid: same as Ford model, PAB ON, Mid switch ON
* HRM: based on HRM circuit, Overdrive channel, Mid switch OFF
* HRM Mid: based on HRM circuit, Overdrive channel, Mid switch ON

[[Cabinet models list | Cab:]] Dumble 2x12 or 4x12 (G12-65, EVM)

Volume (Clean), Bass, Middle, Treble, Overdrive Level, Ratio, Volume (Overdrive), Master, Presence, Bright switch, Mid boost switch, Jazz/Rock switch (not modeled), Pre Amp Boost (PAB)

Power tubes: EL34

# "The ODS100 has two drive controls, one is right at the input, the other is in the lead boost section."
# "I hate to admit it but there is something special about a real Dumble. I don't know what it is but there is something in the voicing. The various clones I have are cool and have their own thing going but they don't sound like the Dumble. Hard amp to play though. Very unforgiving but tremendous clarity." [https://forum.fractalaudio.com/posts/824398]
# "They call HRM "Hot Rubber Monkey" but what it really means is "Hot Rod Marshall"." The HRM Dumbles have a fixed Marshall tone stack at the output of the lead channel. This gives a little scoop to the mids." [https://forum.fractalaudio.com/posts/828279]
# "My Dumble is S/N 0213 IIRC. It's an EL-34 ODS HRM." [https://forum.fractalaudio.com/posts/1170559]
# "The ODS-100 Ford 2 model is not based on the HRM model with the HRM tonestack removed. Whether or not the model matches any particular Dumble is unknown as we have not been able to procure a non-HRM Dumble yet. The model is based on schematics that were given to us that supposedly accurately represent Robben Ford's Dumble. Whether or not the schematics are accurate I do not know. The voltage divider at the output of V1B is set to 0.078 which is based on the values that are indicated on the schematic for the set-point of the trimmer. As no two Dumbles are identical it stands to reason that one person's interpretation of the ideal Dumble voicing may not agree with another's. Since V1 is running clean you can get more gain by simply increasing Input Trim. It will have basically the same effect as increasing the trimmer."
# "A signal divider, which is more correctly called a voltage divider, is calculated by taking the resistance to ground divided by the sum of the resistances. In this case the voltage divider would be 26.7/317 = 0.084. This is very close to the values that we were given (which yield 0.078). Our model also uses local feedback on V1B (which is about 2-3 dB less gain) and accounts for the voltage divider's affect on the AC load line. In fact all stages in a Dumble typically have an AC load-line that's different than the DC load-line due to the load resistance being significant in relation to the plate resistor. Since V1A and V1B run clean (linear) Input Trim will accomplish the same thing as increasing the trimmer into the drive stages. This is because a linear system is commutative (see any introductory Signals and Systems text for properties of linear systems). The commutative property is where A x B = B x A. Therefore it does not matter if the gain is before or after the linear stages."
# "The Mid switch, sometimes labeled "Deep", shorts out the 390 pF cap in the tone stack (which is in series with a 2 nF cap). All that is left then is the 2 nF cap. With PAB active this lowers the lowcut frequency." [http://forum.fractalaudio.com/threads/dumbles-in-q2.110382/#post-1321445]
# "Maybe the best clean model IMO. You have to really crank the MV though (just like the real amp)." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-8-00-public-beta.126728/page-7#post-1507967]
# "The only amps with a bright cap on the MV are Dumbles and their various clones/derivatives. This was/is done to compensate for the lack of a buffer for the fx loop. The loop send is taken right off the MV which means the output impedance is very high. Any significant length of cable will then attenuate the highs due to the cable capacitance. The bright cap boosts the highs to compensate. It's the same idea as a bright cap on your guitar's volume knob. Crude. FWIW, this is a terrible loop design but "it's a Dumble" so it's all part of the mystique. Dumble then released the "Dumbleator" which is nothing more than a buffer and recovery in an external box. Dumble fanatics, of course, claim that to have the true Dumble experience you MUST use the Dumbleator which is just another load of BS." [https://forum.fractalaudio.com/threads/pick-attack.137945/#post-1720592]
# "We actually own a real Dumble. I bought it off a lawyer (surprise, surprise) some years ago who was in trouble with the IRS. Also a matching 4x12 cab. Both in mint condition. At the time I paid $50K for both. Probably worth twice that now." [https://www.thegearpage.net/board/index.php?threads/modelers-with-accurate-dumble-models.2120479/page-7#post-30771582]
# "PAB disconnects some components in the tone stack. The treble cap is still in the circuit path." [https://forum.fractalaudio.com/threads/ods-pab.180951/#post-2215259]
# Firmware 21: "Added “Overdrive Volume” parameter to Dumble-type amp models (ODS-100, Two Stone, etc.). This is sometimes labeled “Ratio” or “Lead Master”. As the Master Volume on these amps often has a bright capacitor the Overdrive Volume control allows setting the Master Volume higher to counteract the bright cap and then lowering the power amp drive with the Volume."</blockquote>
# "Most, if not all, Dumble-style amps have a Ratio/Volume/Lead Master/etc. control so this makes the models complete in that regard. My Fuchs ODS 50 does NOT have a bright cap on the MV but it has an "Output" control for the overdrive channel that is in series with MV." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-00-public-beta-2-beta-2.187991/post-2331157]</blockquote>

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-ods-100-dumble-overdrive-special.114390/ Yek's write-up]

==ODS-100 FORD==

==ODS-100 FORD PAB==

==ODS-100 FORD PAB MID==

==ODS-100 HRM==

==ODS-100 HRM MID==

==PVH 6160 BLOCK (Peavey "Block Letter" EVH 5150)==

[[File:5150.jpg|300px]]

Models:
* Rhythm channel with Crunch switch engaged
* Lead channel

[[Cabinet models list | Cab:]] Peavey 4x12 (Sheffield 1200)

Pre Gain, Post Gain (Master), Low, Mid, High, Resonance, Presence, Bright and Crunch switches (Rhythm channel only, not modeled)

Power tubes: 6L6

# "I have a "holy grail" Block Letter 5150 (supposedly). It sounds way better than most 5150s for some reason which is a good thing for you guys. I think it's partly due to the fact that it has a bias mod so it's biased a bit warmer than a stock version." [https://forum.fractalaudio.com/posts/1152978]
# "Another technique is to use negative feedback to the grid. This is done in 5150-based designs which makes the stage clip even harder. The last stage of a 5150 basically looks like a diode clipper. The harder the clipping the more overtones that are created and the better the tone cuts. Without those overtones your sound is lost in the mix." [http://forum.fractalaudio.com/threads/fizz-is-good.67719/#post-833875] </blockquote>
# (differences between Peavey 5150 and 6505) "There are differences. The input gain network is different and the coupling cap after the second triode stage is a different value." [https://forum.fractalaudio.com/threads/peavey-invective-killer-amp.172625/post-2088479]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-pvh-6160-block-evh-5150-“block-letter”.114607/ Yek's write-up]

==PVH 6160 BLOCK CRUNCH==

==PVH 6160+ CLEAN (Peavey 6505+ / EVH 5150-II)==

[[file:6505.jpg|300px]]

Models:
* Clean channel, Bright switch OFF
* Clean channel, Bright switch ON
* Crunch channel, Bright switch OFF
* Crunch channel, Bright switch ON
* Lead channel

[[Cabinet models list | Cab:]] Peavey 4x12 (V30)

Rhythm channel: Pre (gain), Bright switch (6dB at 2kHz), Crunch switch, Low, Mid, High, Post (Master), Resonance, Presence

Lead channel: Pre (gain), Low, Mid, High, Post (Master), Resonance, Presence

Power tubes: 6L6

# "Chris Quigley's 6505 was the reference amp. It's my amp now. It's a very good sounding one." [https://forum.fractalaudio.com/posts/824411]
# (channel 1) "Someone was looking for that amp model recently so I dug our 6505+ out and was surprised at how nice that channel sounds." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-1-03-firmware-release.106931/#post-1278700]
# "A 6505+ is identical to a 5150 except it has no bright cap. Use the 5150 model and turn off the bright switch." [https://forum.fractalaudio.com/threads/request-acoustic-peavy-6505.56527/#post-711922]
# "The Bright switch on clean and crunch channels does not engage a capacitor on the drive potentiometer as is typical but instead disengages a treble cut circuit"

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-pvh-6106-peavey-6160-evh-5150-ii.114608/ Yek's write-up]

==PVH 6160+ CLEAN BRIGHT==

==PVH 6160+ CRUNCH==

==PVH 6160+ CRUNCH BRIGHT==

==PVH 6160+ LEAD==

==PLEXI 100W 1970 (1970 100W Marshall Plexi)==

[[file:SLP.png|300px]]

Plexi models:
* 1970 100 watts, EL34
* 1969 100 watts, High Treble channel
* 1969 100 watts, Normal and High Treble channels jumpered
* 1969 100 watts, Normal channel
* 1972 50 watts, 6550 power tubes
* 6AC7 50 watts, 6AC7 power tubes
* 1981 50 watts JMP with master volume, EL34
* 1967 50 watts, EL34, High Treble channel ("High 1")
* 1967 50 watts, EL34, High Treble channel ("High 2") (2nd triode stage has a 0.68uF cathode bypass capacitor, which was added in the early 70’s and gives a slightly brighter tone)
* 1967 50 watts, EL34, Normal and High Treble channels jumpered
* 1967 50 watts, EL34, Normal channel

[[Cabinet models list | Cab:]] Marshall 4x12 (G12M, G12H)

Volume Normal / Volume Treble, Bass, Middle, Treble, Presence, Master (Plexi 2204 only)

# "1970 Marshall 1959SLP 100 has a darker, smoother sound than earlier Plexis."
# "One of the first mods people make to real 'Plexi' Marshalls is to "clip the bright cap". The bright cap varied over the years, supposedly depending on what was lying around in the shop. The model defaults to the bright cap in the circuit. If you turn off Bright you're effectively clipping the bright cap. The bright cap in Marshalls can be very bright and harsh. However, if you crank the Master you might find the extra brightness helps compensate for the power amp getting darker."
# "It's the way a Plexi is supposed to sound. That's due to the cathode follower. That raspiness helps it cut through in a mix. I own three of them and they are that fizzy." [https://forum.fractalaudio.com/posts/576475]
# "Don't be afraid to turn the bass all the way down or the treble all the way up. Just like with the actual amp. For example, on the Normal channel of a Plexi most people turn the bass way down. Otherwise it's too flubby." [https://forum.fractalaudio.com/posts/577248]
# "My settings for a "typical" Plexi tone are Bass: 2, Mid: 8, Treble 7.5. Adjust Presence to taste." [https://forum.fractalaudio.com/posts/1179420]
# "Try the Plexi 100W 1970 with Factory Cab 54. Be sure to dial it in like you would in 1970, i.e. turn the Mid, Treble and Presence way up; turn Norm Drive and Bass down a bit." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-2-00-public-beta-deux.109702/#post-1312811]
# (Boston/Rockman sound) "Plexi Jump. Everything on 7. Put a Filter block in front: Type: Peaking, Freq: ~800 Hz, Q: 0.707, Gain 12 dB."
# (Plexi 100W 1970) "I've never cared for that model nor the actual amp. IMO it doesn't have enough feedback (100K off the 4-ohm tap). Some amps of that era had 47K off the 4-ohm tap. Some had 47K off the 8-ohm tap. Some had 100K off the 8-ohm tap and some even had 47K off the 16-ohm tap! IOW all over the map. Bottom line: try adjusting Negative Feedback. I always raise it up a bit with that model. Around 4 or so." [http://forum.fractalaudio.com/threads/plexi-100watt-1970-is-something-wrong-with-it-now.125522/#post-1493932]
# "What you are hearing is output transformer high frequency resonance. Old Plexis didn't do this because they had good transformers. New transformers are crappy and resonate at the cutoff frequency because they are underdamped. This causes a raspy, fizzy texture to the distortion. The transformer resonance is adjustable but the parameter isn't exposed to the user. When you turn it up you get that same squishy rasp that you are hearing. For the Plexis I have the damping set to flat with no resonance because that's how our vintage Plexis measure. Our 50W is a little underdamped but people complain about raspy high frequencies so I erred on the safe side." [http://forum.fractalaudio.com/threads/dimed-real-plexi-vs-dimed-simulation-q8-01.127161/page-2#post-1513888]
# "When modding Marshalls for higher gain sometimes the modder will decrease the input frequency response to reduce noise and fizziness. You can do this by reducing the high-cut frequency in the input EQ. Or you can use a high-shelf filter which is a little more subtle. Another technique is to put a capacitor across the second-to-last triode stage. This is the "Triode 1 Plate Freq" parameter. Reduce this to around 2 kHz to start which is typical of amps like an SLO100, etc." [https://forum.fractalaudio.com/threads/dialling-in-the-marshalls.143682/post-1707222]
# "The Plexi 100W 1970 model is a non-MV "Plexi". Circuit is slightly different than the late 60's model (Plexi 100W)." [https://forum.fractalaudio.com/threads/marshall-amp-question.155223/post-1847908]
# "All the distortion comes from the power amp so the tone controls don't do much." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2052743]
# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]
# [[Amp_block#NEGATIVE_FEEDBACK|Negative feedback values]]
# "(100W model) Our reference amp has a 560p treble cap and a 10A treble pot taper. Both components appear to be original. The tech who checked it out after I bought it said it was one of the best sounding 100W Plexis he'd ever heard. That tech just happens to be Alan Phillips of Carol-Ann Amps. So I modeled it to agree with the reference amp." [https://forum.fractalaudio.com/threads/modeling-questions.199009/post-2491136]
# (100W model) It's a '69. The 50W might be a '67. Hard to keep track of it all. I must have at least a dozen Marshalls now." [https://forum.fractalaudio.com/threads/modeling-questions.199009/post-2491192] and [https://forum.fractalaudio.com/threads/nothing-like-a-real-plexi.64593/post-801933]
# (100W model) "All the pots are log pots in our reference amp" and "I was puzzled by the pot tapers but they all look original. I then thought about it a bit and wondered if that's why Bogner uses log pots for his amps. His stuff is definitely Plexi-inspired. Or maybe all Marshall could find at the surplus electronics store that week was log pots. Who knows." [https://forum.fractalaudio.com/threads/modeling-questions.199009/post-2491180]
# (50W model) "Our reference 50W Plexi has a 68nF presence cap and the presence network is JCM800-style." [https://forum.fractalaudio.com/threads/modeling-questions.199009/post-2491179]
# A bug in the model's tonestack was fixed in firmware 23.03.

[http://forum.fractalaudio.com/threads/late-70s-marshall-jmp-master-model-50w-mk2-lead.135541 Forum discussion about the Plexi 2204 model]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-plexi-marshall-plexi.114529/ Yek's write-up]

==PLEXI 100W HIGH (1969 100W Marshall Plexi)==

# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]
# "The power supply sags more in a 100W. On our reference 100W Plexi the supply sag is almost double that of our 50W." [https://forum.fractalaudio.com/threads/marshall-jmp-100w.198803/post-2478167]
# "The topology of that model does not support a bright cap and the actual amp has no bright cap." [http://forum.fractalaudio.com/threads/q2-01-plexi-50w-nrml-bright-cap-doesnt-work.111836/#post-1337410]
# "All the pots are Logarithmic pots in our reference amp." [https://forum.fractalaudio.com/threads/modeling-questions.199009/post-2491161], Authors Note: Standard Plexi tonestack has Linear pots for Mid and Treble, only Bass is Log.
# "Our reference 100W is a late 60s." [https://forum.fractalaudio.com/threads/modeling-questions.199009/page-3#post-2491180]
# "It's a '69." [https://forum.fractalaudio.com/threads/modeling-questions.199009/page-3#post-2491192]

==PLEXI 100W JUMPED==

==PLEXI 100W NORMAL==

==PLEXI 2204 (1981 50W Marshall JMP 2204)==

# "Based on a 1981 JMP 50W Master Volume head."
# (recommended settings) "Everything on 10."
# "There were several versions of the "2204" Plexi. Our model is based on a 1981 2204 Master Volume JMP. It has a different circuit than a JCM800." [https://forum.fractalaudio.com/threads/marshall-sound-clips.169296/post-2034903]
# "The model is based on the Hi input of a 1981 50W Master Volume "2204" Plexi. There were two versions of the 2204. One was essentially a Plexi with a Master Volume. Similar to a 1987x but with some different values and voltages in addition to the MV. The other was virtually identical to a JCM800. The model is the Plexi version. Mine is an '81 and doesn't have cascaded gain stages." [https://forum.fractalaudio.com/threads/plexi-2204-question.178464/]
# "It's a 1981 "CSA" 2204."[https://forum.fractalaudio.com/threads/plexi-2204-question.178464/post-2175316]
# [https://forum.fractalaudio.com/proxy.php?image=https%3A%2F%2Fimages.reverb.com%2Fimage%2Fupload%2Fs--0dABDsRq--%2Fa_exif%2Cc_limit%2Ce_unsharp_mask%3A80%2Cf_auto%2Cfl_progressive%2Cg_south%2Ch_620%2Cq_90%2Cw_620%2Fv1518443139%2Fvgiq3h9wiuaj0jw2wxhb.jpg&hash=5b419d07341f4bdad48af0657dcd11de Picture of the modeled amp]

==PLEXI 50W 6550 (1972 50W Marshall Plexi)==

* High Treble Channel

==PLEXI 50W 6CA7 (50W Marshall Plexi)==

Models:
* Single channel
* Jumped channels

# "That's based on my favorite Plexi. I have several but this particular one has 6CA7s and 82K grid resistors(!). Usually the grid resistors are 220K." [https://forum.fractalaudio.com/threads/plexi-50w-6ca7-sooooo-good.169084/post-2031777]

==PLEXI 50W 6CA7 JUMPED==

==PLEXI 50W HIGH 1 (1967 50W Marshall Plexi)==

==PLEXI 50W HIGH 2==

# "Similar to Plexi 50W High 1 except the second triode stage has a 0.68uF cathode bypass capacitor. The second bypass capacitor was added in the early 70’s and gives a slightly brighter tone."
# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]
# "Our reference 50W Plexi has a 68nF presence cap and the presence network is JCM800-style." [https://forum.fractalaudio.com/threads/modeling-questions.199009/page-3#post-2491179]
# "Plexi High 2 has a 0.68uF cap on V2A and the mixing resistor for the normal channel removed." [https://forum.fractalaudio.com/threads/modeling-questions.199009/post-2504055]
# "I removed the virtual resistor because it sounds better to me that way. This was a common mod for people who only used the High input." [https://forum.fractalaudio.com/threads/modeling-questions.199009/post-2504173]

==PLEXI 50W JUMPED==

==PLEXI 50W NORMAL==

# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]

==PORTA-BASS (Ampeg Portaflex bass amp)==

Model:
* Single channel

[[Cabinet models list | Cab:]] SVT cab with one or more 10”, 12” or 15” Eminence speakers

Gain, Volume, Bass, Mid, Treble, Mid Frequency (not modeled), input pad (not modeled), compression (not modeled), limiter (not modeled), Ultra Hi switch, Ultra Lo switch (not modeled)

It's not been disclosed on which Portaflex amplifier the model is based

Power tubes: 6L6

Notes: see SV Bass

==PRINCE TONE 5F2 (Fender Tweed Princeton, 5F2-A)==

[[file:princeton.jpg|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Fender 1x10 (C10n)

Volume, Tone

Power tubes: 6V6

[http://forum.fractalaudio.com/posts/1370144/ Yek's write-up]

==PRINCE TONE AA964 (silverface Fender Princeton without reverb, AA964)==

Model:
* Single channel

Volume, Bass, Treble

Power tubes: 6V6

# "Based on a Fender AA964 Princeton. This particular amp is an early CBS “Silverface” but still using pre-CBS design and components."

==PRINCE TONE REVERB (1966 blackface Fender Princeton with reverb, AA964)==

[[file:princetonreverb.jpg|300px]]

Model:
* Single channel

Volume, Bass, Treble, Reverb (not modeled)

Power tubes: 6V6

# "A Princeton Reverb has an extra gain stage due to the reverb recovery. Hence it has more gain." [https://forum.fractalaudio.com/threads/what-causes-this-volume-difference.97845/#post-1174202]

==RECTO1 ORANGE MODERN (MESA Dual Rectifier, 2 channels)==

[[file:recto.png|300px]]

Rectifier models:
* Recto1: original 2-channel Rectifier, Orange channel, Modern mode
* Recto1: original 2-channel Rectifier, Orange channel, Vintage mode
* Recto1: original 2-channel Rectifier, Red channel, Modern mode
* Recto2: later 3-channel Rectifier, Orange channel, Modern mode
* Recto2: later 3-channel Rectifier, Orange channel, Vintage mode
* Recto2: later 3-channel Rectifier, Red channel, Modern mode
* Recto2: later 3-channel Rectifier, Red channel, Vintage mode

[[Cabinet models list | Cab:]] Mesa 4x12 (V30)

Gain, Master, Bass, Middle, Treble, Presence

Power tubes: 6L6

# "The reason you're hearing the highs rolled off is because the Master is too high. As you increase the Master the highs get muffled. 7.02 for the Recto Master is ridiculous and will sound like crap." [https://forum.fractalaudio.com/threads/axe-fx-vs-tube-amps-my-first-experience.27192/page-3#post-412068]
# "Note that the Orange Modern and Red Modern models have no negative feedback and therefore the Presence control is a Hi Cut control." [https://forum.fractalaudio.com/threads/version-10-00-stuff.63202/#post-783037]
# "A typical Recto cabinet has a resonant frequency a little over 100 Hz." [https://forum.fractalaudio.com/threads/dual-recto-with-the-lb-2-vs-the-axe-fx-iii-and-more.143501/page-2#post-1699892]
# "The unique thing about a Dual Recto tone stack is that the Presence control is part of the tone stack. So the Recto tone controls also interact with the presence control." [https://forum.fractalaudio.com/threads/dual-recto-with-the-lb-2-vs-the-axe-fx-iii-and-more.143501/#post-1699011]
# "Rectos don't have a Depth control and even if they did it wouldn't do anything in Modern Red mode since that mode has no negative feedback. When you put a Recto into Modern Red mode it opens a relay which removes the NFB." [https://forum.fractalaudio.com/threads/recto-depth.92482/#post-1111780]
# "Real Rectos are bassy/fizzy beasts but that tone works great for certain genres." [https://forum.fractalaudio.com/posts/658849]
# "If you are using the Modern modes be very careful with the MV. If you turn it up too high it will flub out really quick. If in doubt reduce the MV. Compensate with the Level control." [https://forum.fractalaudio.com/posts/829334]
# "The Modern mode in Rectos has no negative feedback so there's a huge bass boost from the speaker impedance. Fortunately you can reduce this by reducing the LF Resonance on the Spkr tab which is something you can't do with the real amp without trying different speakers or cabinet." [https://forum.fractalaudio.com/posts/829906]
# "Depth works by varying the negative feedback at low frequencies. There is no NFB in the Modern Red mode so the Depth knob won't do anything." [https://forum.fractalaudio.com/posts/1111770]
# (Thordendal models) "The old Recto models weren't terribly accurate. When G3 came out the models were accurate but Fredrik contacted me and said something like "ahhhhh, I loved the old Recto model". So I took the old Recto models and made them "Thordendal" models." [http://forum.fractalaudio.com/threads/thordendal-modern-vs-recto-1-modern-red.91645/#post-1269530]
# "All passive tone controls interact and all the Axe-Fx tone stacks replicate this behavior. The unique thing about a Dual Recto tone stack is that the Presence control is part of the tone stack. So the Recto tone controls also interact with the presence control." [https://forum.fractalaudio.com/threads/dual-recto-eq-potentially-silly-question.93890/#post-1126242]
# "If you are using the Modern mode then it's all about the Spkr page. Since that mode has no negative feedback the speaker resonance has a tremendous effect on the sound. Adjust LF Res, Freq and Q to get desired response." [http://forum.fractalaudio.com/threads/anyone-have-any-luck-with-the-rectifier-models.109907/#post-1315682]
# "Another thing with the Modern modes is that the power amp distorts early (again since there is no negative feedback and, therefore, the power amp has a lot more gain). At 9:00 on the Master the power amp is distorting (it's probably a linear taper pot for the ol' "Wow, this amp is loud bro!"). (...) Another thing is that if you put ANYTHING in the loop of a Recto it changes the tone significantly. Even just a short cable. All the models were made with the loop off. And another thing is that Rectos changed a lot. I have three of them and they all sound completely different. One of them has a different value Gain pot than the others. One of them has a different value bright cap than the one with the same Gain pot. Since the gain pot and bright cap interact this makes a HUGE difference. Experiment with the Bright Cap value. The Recto1 models are based on our Rev. F (IIRC, whatever the desirable ones are). The Recto2 models are based on the latest version." [http://forum.fractalaudio.com/threads/anyone-have-any-luck-with-the-rectifier-models.109907/#post-1315714]
# "We have three of them, a single and two duals." [http://forum.fractalaudio.com/threads/when-were-the-rectos-improved.122719/#post-1459883]
# "If you want that Recto crunch but not so flubby and fizzy try the SOLO models." [http://forum.fractalaudio.com/threads/ax8-v7-00-public-beta.125015/page-3#post-1487394]
# "A Recto is not a Mark series amp. Totally different preamp topology. A Recto preamp is very similar to a SLO100." [https://forum.fractalaudio.com/threads/the-greatest-digital-guitar-recording-of-all-time.154788/post-1841448]
# (amp model closest to the MESA Roadster) "Recto 2." [https://forum.fractalaudio.com/threads/what-amp-model-is-closest-to-the-mesa-roadster.127060/post-1512755]
# "The Rectifier preamp is almost identical to an SLO100." ... "There's a treble cut on the tone stack and a some minor changes to the power amp and power supply but it's basically a ripoff. The schematics are readily available for both so anyone interested can see for themselves. Personally I hate the 39K resistor. It biases the stage much too cold for my tastes. It prevents blocking distortion but there are better ways to do it IMO. The FAS Modern model is similar but biases the stage more towards the center." [https://forum.fractalaudio.com/threads/new-amp-models.159097/post-1901310]
# "Using the loop on a modern 3-channel rectifier changes the tone pretty dramatically (we model the amp with the loop bypassed). There are several reasons for this:
## The source impedance to the power amp is changed.
## There is a treble peaker on the Output pot. Presumably this was done to counteract treble loss in the loop.
## An extra highpass filter is present due to the loop send stage. The corner frequency is around 30 Hz. That's low but it does affect subharmonics due to intermodulation. I would've made the capacitor around 1uF." [https://www.thegearpage.net/board/index.php?threads/blind-test-mesa-dual-rectifier-vs-mystery-modeler-update-results-revealed.2208367/post-31646126]
# "Recto2 is based on a new 3-channel Dual Rectifier. Recto1 is based on the original 2-channel." [https://www.thegearpage.net/board/index.php?threads/blind-test-mesa-dual-rectifier-vs-mystery-modeler-update-results-revealed.2208367/post-31647001]
# "I have three Rectos: an old Single Rectifier, an old (Rev. G maybe) Dual Rectifier and a new Dual Rectifier. They all sound completely different. The old Dual is the best sounding of the bunch." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-9-cygnus-firmware-public-beta-6.171176/post-2062420]
# "The MV taper of the model is authentic so just like the real amp the power amp starts to clip very early. With the real amp there's audible feedback (as in it gets insanely loud) but with the model you don't get that and humans have this weird thing where they don't like knobs to deviate from noon. I've debated changing the taper or adding a pad between the preamp and power amp but, in the end, I decided to keep things authentic." [https://forum.fractalaudio.com/threads/simple-tip-for-recto-tones.174349/post-2114224]
# "You have to be very careful with the Master Volume. A Recto will start saturating the power amp in Modern mode at VERY low MV settings. Once the power amp starts clipping the tone will change. With digital products I often see people set the MV higher than they would on the real amp because there are no sonic repercussions (i.e., pissing off the wife/neighbors, knocking Grandma's urn off the mantel, etc.). If an emulation sounds darker or more midrangey than the real amp try turning down the MV. If it's a good emulation you should find a point (around 1-2) where you can hear the power amp start to saturate. Go up/down from there to get the desired power amp overdrive." [https://www.thegearpage.net/board/index.php?threads/why-are-rectifier-emulations-so-off.2341907/post-34347979]
# (Recto1) "Our OG Dual Rectifier has a 10A MV taper. The model uses 20A which is the same taper as the Recto2. (...) Other than that the model is in very good agreement with the amp." [https://thegearforum.com/threads/adventures-in-fractals-dual-rectifiers.3949/post-151166]
# "The Red channel has no negative feedback so the response is highly dependent upon the impedance curve. Vintage has quite a bit." [https://thegearforum.com/threads/adventures-in-fractals-dual-rectifiers.3949]
# "On the amp the MV is around 9 o'clock (as loud as I dared to go and not get divorced). I had to set the model to 1.2 to get the same response. Above that and the power amp starts clipping and the highs get reduced. This is to be expected given the different taper between the amp and the model." [https://thegearforum.com/threads/adventures-in-fractals-dual-rectifiers.3949/post-151193]
# (firmware 24.00) "Changed Master Volume taper for Recto1 models to agree with actual amp. This will slightly reduce the volume into the virtual power amp."
# (about the non-working Presence control on the two-channel Dual Rectifier's Orange channel) "These situations always present a dilemma:
## Option 1: Remove the presence control and deal with "Why u no hav presence control on the Recto1 Orange Modern model. The real map has one."
## Option 2: Put a presence control on there that doesn't do anything and deal with "Hey idiots, the presence control on the Recto1 Orange Model is broken."
## Option 3: Put a presence control on the model that actually does something but defaults to a value (in this case 5.0) that matches the amp's native behavior. We chose Option 3." [https://thegearforum.com/threads/adventures-in-fractals-dual-rectifiers.3949/page-17#post-159707]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-recto1-and-recto2-mesa-dual-rectifier-2-ch-and-3-ch.114701/ Yek's write-up]

==RECTO1 ORANGE NORMAL==

==RECTO1 RED==

==RECTO2 ORANGE MODERN (MESA Dual Rectifier, 3 channels)==

==RECTO2 ORANGE VINTAGE==

==RECTO2 RED MODERN==

==RECTO2 RED VINTAGE==

==REVV GEN GREEN 1 (REVV GENERATOR 120)==

Models:
* Green channel, least aggression (green)
* Green channel, tight saturation (blue)
* Green channel, fat saturation (red)
* Purple Gain channel, least aggression (green)
* Purple Gain channel, tight saturation (blue)
* Purple Gain channel, fat saturation (red)
* Red Gain channel, least saturation (green)
* Red Gain channel, tight saturation (blue)
* Red Gain channel, fat aggression (red)

[[Cabinet models list | Cab:]] Revv 4x12 (V30)

Gain, Bass, Mid, Treble, Level, Master, Presence, Depth. Options on Clean and Crunch channels: Wide / Drive / Bright. Options on Purple and Red channels: Aggression / Bright / Cut / Fat.

Power tubes: 6L6

# "Revv is a great amp. Sort of a Marshall/SLO vibe but more open. Really well designed and built." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-22-00-release.195047/post-2429051]
# "The Revv actually has an MV that makes sense. Instead of driving the power amp into oblivion at around 3, power amp overdrive doesn't start happening until you turn the knob up quite a bit." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-22-00-release.195047/post-2429139]

==REVV GEN GREEN 2==

==REVV GEN GREEN 3==

==REVV GEN PURPLE 1==

==REVV GEN PURPLE 2==

==REVV GEN PURPLE 3==

==REVV GEN RED 1==

==REVV GEN RED 2==

==REVV GEN RED 3==

==RUBY ROCKET (Paul Ruby Rocket)==

[[File:rocket.jpg|300px]]

Models:
* Bright switch ON
* Bright switch OFF

[[Cabinet models list | Cab:]] 1x12 (Alnico, G12M)

Volume, Bass, Treble, Cut, Bright switch

Power tubes: EL84

# "The Ruby Rocket is not the same as an actual Trainwreck Rocket. There are topology differences and the amps don't sound the same." [https://forum.fractalaudio.com/posts/1154295]
# "Ruby Rocket is based on a Paul Ruby Rocket which is based on a TW Rocket but with some notable differences." [https://forum.fractalaudio.com/threads/axe-fx-ii-firmware-18-00-public-beta.96198/page-30#post-1154336]
# "The Bright switch changes a coupling cap and the treble cap in the tone stack. This cuts the bass, shifts the midrange and lowers the gain slightly. That's why there are two separate models. Otherwise you would just engage the Bright switch under the Treble knob."
# "The Ruby Rocket has a bright switch but it's actually a channel select (selects the bright channel)."

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-ruby-rocket-paul-ruby-rocket.114725/ Yek's write-up]

==RUBY ROCKET BRIGHT==

==SV BASS 1 (Ampeg SVT bass amp)==

[[File:ampeg.jpg|300px]]

SVT models:
* SV Bass 1: Fractal Audio's model prior to the change in firmware Ares 2.05 and later
* SV Bass 2: channel one of a 1970 Ampeg SVT with 6550 power tubes and the midrange switch in position 3

Note: on the Axe-Fx II (firmware Ares) these models are reversed [https://forum.fractalaudio.com/threads/sv-bass-1-and-sv-bass-2-in-ares-1-03.149364]

[[Cabinet models list | Cab:]] SVT 8x10

Volume, Treble, Midrange, Bass, Master, Midrange switch, Ultra-Hi switch (= Bright), Ultra-Lo switch (not modeled)

Power tubes: 6550

Uses a James tonestack [https://forum.fractalaudio.com/threads/have-we-reached-the-end-of-new-amp-models-in-the-axe-3.184271/post-2482710]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-sv-bass-ampeg-svt.115282/ Yek's write-up]

==SV BASS 2==

==SHIVER CLEAN (Bogner Shiva 20th Anniversary)==

[[File:shiva.png|300px]]

Models:
* Clean channel
* Lead channel

[[Cabinet models list | Cab:]] Bogner 1x12 or 2x12 (Classic 80, V30)

Clean channel: Volume, Bass, Treble, Bright switch. Shared: Master, Presence, Excursion, Boost switch (not modeled)

Lead channel: Gain, Volume, Bass, Middle, Treble, Shift EQ (not modeled), Bright switch, Mode switch (not modeled). Shared: Master, Presence, Excursion, Boost switch (not modeled)

Power tubes: KT88

# "People think Bogners are dark but they really aren't. The reason they seem that way is the pot tapers. Most people assume knobs should be set somewhere around noon. If you do this on a Bogner it's like turning the treble way down on a Marshall. Close your eyes and adjust the tone controls with your ears. Don't be afraid to turn them way up or way down." [https://forum.fractalaudio.com/posts/1031334]
# "Human nature is to put the knobs near noon. We are reticent to deviate much from noon. Amp designers exploit this and use different tapers to change the sound of their amps WITH THE KNOBS AT NOON. A prime example are Bogner amps. Everyone says "Bogner amps are dark". No they aren't. But he uses a Log10A taper for the treble pot. It's a standard Marshall tone stack. Usually a linear taper pot is used for the treble. The treble knob at 5.0 (noon) on a Bogner is equivalent to the treble knob at 1.0 on a Marshall. People put the knob at 5.0 and go "wow, this amp is dark". No it isn't. If you turned the treble up to 8 or 9 it would sound a lot like a Plexi but humans are reticent to turn the knobs to extremes. Amp designers know this and exploit it to give their amps a "signature sound"." [https://forum.fractalaudio.com/posts/1047275]
# "The original Shiva models were based on a borrowed amp. We now have a 20th Anniversary Shiva (with KT88s) and the new models are based on that amp. We did notice that this amp has less gain than the one used originally but the model is faithful to the amp." [https://forum.fractalaudio.com/posts/1152978]
# "Bogner's are notoriously "slow" due to the low B+ voltage. Main reason I can't get along with them. You can try increasing the Variac." [https://forum.fractalaudio.com/threads/fast-pick-attack-amp.170370/post-2049711]
# "Most amps use a linear taper for the treble pot. Bogners use a log taper. So when the knob is at noon on a Bogner it's similar to 8 o'clock on most amps." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486/post-2067364]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-shiver-bogner-shiva-20th-ann.114764/ Yek's write-up]

==SHIVER LEAD==

==SOLO 100 CLEAN (Soldano SLO-100)==

[[File:slo.jpg|300px]]

Models:
* Normal channel in Clean mode
* Normal channel in Rhythm mode
* Overdrive channel

[[Cabinet models list| Cab:]] Soldano 4x12 (Eminence)

Gain, Bass, Middle, Treble, Master, Presence, Bright switch (Normal channel only), Depth (with Depth mod)

Power tubes: 6L6

# "The SLO-100 is the loudest amp I've ever used. It feels like there's a small nuclear explosion going off inside when ever you hit a power chord. It's a wicked amp but not something I would recommend for anything but large gigs. If you like the SLO-100 model you might want to try the Recto models too. It's not widely known but the Rectifier preamp is a derivative of the SLO-100. Some minor changes but the basic topology is identical."
# "I have a really good SLO-100. An original black faceplate version. Pristine condition. That amp was one of the primary amps used in the G2 modeling development. It was by studying that and a really nice JCM-800 that I finally figured out the secret to cathode follower." [https://forum.fractalaudio.com/posts/562187]
# "Mine doesn't have the depth mod but I used the values from the schematic I have and I believe the schematic is correct." [https://forum.fractalaudio.com/posts/830925]
# "SLOs are brittle at low volumes. When you crank them up it smooths out. The problems is at cranked volumes they can kill small animals."
# "The key to an SLO100 is to run the MV high so that the mids thicken up. Otherwise it's a shrill mess. In certain contexts with the right IR it can be a cool sound." [https://forum.fractalaudio.com/posts/1146118]
# "Note that the knobs on '5' on the Axe-Fx correspond to '6' on an SLO because they go to 11. 'Noon' on an SLO isn't actually the knobs at half-way. The range of the knobs is like 8:00 to 6:00 as opposed to 7:00 to 5:00. They're biased clockwise." [https://forum.fractalaudio.com/posts/1057829]
# "Another caveat when comparing amps: many times the knobs aren't "centered". IOW if you put the Treble knob at noon it isn't actually at 50%. You can see this by turning the knob all the way down and all the way up. It may not be symmetrical. This happens when the pots don't have a flat spot and/or the pot is rotated within the mounting hole. Or in the case of an SLO100 it is intentional. On an SLO100 all the way down is around 8:00 and all the way up is 6:00 so 50% is around 1:00 not noon." [https://forum.fractalaudio.com/posts/1158815]
# "Many people find SLOs too bright. The "Warren Haynes" mod is a popular mod to reduce the brightness."
# "Those amps are all designed to get their character from power amp distortion. If you don't push the power amp all you are hearing is the preamp which is voiced to be trebly. The power amp then compresses the highs and the sound gets fatter."
# "If you want that Recto crunch but not so flubby and fizzy try the SOLO models. They're much brighter so I turn the treble down quite a bit." [http://forum.fractalaudio.com/threads/ax8-v7-00-public-beta.125015/page-3#post-1487394]
# "SLO 100s are NOT smooth amps. They are nasty, aggressive things that you have to crank the MV." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-00-beta-3.148907/page-4#post-1764615]
# "A Recto is not a Mark series amp. Totally different preamp topology. A Recto preamp is very similar to a SLO100." [https://forum.fractalaudio.com/threads/the-greatest-digital-guitar-recording-of-all-time.154788/post-1841448]
# "The Rectifier preamp is almost identical to an SLO100." [https://forum.fractalaudio.com/threads/new-amp-models.159097/post-1901310]
# "They're pretty awesome amps but to sound great you have to crank 'em and they're ear-splitting loud." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-09.162488/post-1947441]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-solo-100-soldano-slo-100.114877/ Yek's write-up]

==SOLO 100 LEAD==

==SOLO 100 RHYTHM==

==SOLO 88 CLEAN (Soldano X88R preamp)==

[[image:x88r.jpg|300px]]

Models:
* Clean channel
* Rhythm channel
* Lead channel

Gain, Bass, Middle, Treble, Volume, Bright switch (Clean and Rhythm channels only)

Power tubes: same as SLO-100 model (6L6)

# "Solo 88 RHY is based on an X88R since the rhythm channel of an X99 is identical to an SLO-100. FWIW, I have two X88Rs and the model agrees with both."

[https://forum.fractalaudio.com/posts/718846/ Yek's write-up]

==SOLO 88 LEAD==

==SOLO 88 RHYTHM==

==SOLO 99 CLEAN (Soldano/Caswell X99 preamp)==

[[File:Cliff X88.jpg|300px]]

Models:
* Clean channel
* Lead channel, Bright OFF
* Lead channel, Bright ON

Gain, Bass, Middle, Treble, Volume, Bright switch

Power tubes: same as SLO-100 model (6L6)

# "The rhythm channel of an X99 is identical to a SLO 100." [https://forum.fractalaudio.com/posts/718846]
# "Power amp: same as SLO100." [https://forum.fractalaudio.com/posts/1250203]
# "The bright cap on the X99 Clean is not across the Drive pot. The exposed "Bright Cap" is across the Drive pot, the X99 clean channel does not have one." [https://forum.fractalaudio.com/threads/found-a-bug-soldano-x99-clean-bright-cap.28046/post-418468]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-solo-88-and-solo-x99-soldano-x88r-and-x99.114878/ Yek's write-up]

==SOLO 99 LEAD==

==SOLO 99 LEAD BRIGHT==

==SPAWN NITROUS 1 (Splawn Nitro)==

[[file:nitro.gif|300px]]

Models:
* Overdrive channel in OD-1 (Rhythm) mode
* Overdrive channel in OD-2 (Lead) mode

[[Cabinet models list| Cab:]] Splawn 4x12 (G12M, G12-65, V30)

Resonance, Presence, Bass, Middle, Treble, Master, Gain

Power tubes: KT88

# "Based on a Splawn Nitro with KT-88 power tubes."

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-spawn-nitrous-splawn-nitro.114911/ Yek's write-up]

==SPAWN NITROUS 2==

==SPAWN Q-ROD OD1-1 (Splawn Quickrod)==

[[File:quickrod.jpg|300px]]

Models:
* Overdrive channel, Rhythm mode, 1st gear ("Plexi")
* Overdrive channel, Rhythm mode, 2nd gear ("hot-rodded JCM 800")
* Overdrive channel, Rhythm mode, 3rd gear ("super hot-rodded 800")
* Overdrive channel, Lead mode, 1st gear
* Overdrive channel, Lead mode, 2nd gear
* Overdrive channel, Lead mode, 3rd gear

[[Cabinet models list | Cab:]] Splawn (G12M, G12-65, V30)

Presence, Bass, Middle, Treble, Volume, Gain, Mode

Power tubes: EL34

# "The reason Splawns sound weird is because the tone stack is plate driven. You lose the cathode follower compression and the high source resistance of the plate alters the tone stack frequency response. The plate driven tone stack in the Splawn reduces the highs considerably. You can see this is you run Tone Stack Calculator for the Marshall tone stack and increase the source resistance." [https://forum.fractalaudio.com/posts/1070559]
# "OD2 switches in a cathode bypass cap which increases the gain of that stage." [https://forum.fractalaudio.com/posts/1158818]
# "The Quick Rod is a bit odd in that the Drive pot is linear taper. Most amps use an audio taper pot. This means that at noon the amp is nearly at full gain. Not sure why they did it that way but it is what it is." [https://forum.fractalaudio.com/posts/1159425]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-spawn-rod-splawn-quickrod.114968/ Yek's write-up]

==SPAWN Q-ROD OD1-2==

==SPAWN Q-ROD OD1-3==

==SPAWN Q-ROD OD2-1==

==SPAWN Q-ROD OD2-2==

==SPAWN Q-ROD OD2-3==

==SUHR BADGER 18 (Suhr Badger 18)==

[[File:badger18.jpg‎|300px]] [[File:badger30.jpg‎|300px]]

Badger models:
* Badger 18
* Badger 30

[[Cabinet models list | Cab:]] Suhr 1x12 or 2x12 (V30, G12M)

Bass, Middle, Treble, Gain, Power (controls Power Scaling, not modeled), Drive (acts as Master with Power at 10)

Power tubes: EL84 (Badger 18), EL34 (Badger 30)

# "The Badgers were MIMIC'd with power scaling at full. The knobs are a bit confusing on a Badger. The knob closest to the input jack is labeled "Gain". It is equivalent to the Drive knob in the Axe. The knob labeled Drive is the Master Volume." [https://forum.fractalaudio.com/posts/830810]
# "The controls on the Badger are a bit confusing. Master Volume is labeled Drive. You have the Drive at 10 which means your power amp is at full blast. This can make the bass muddy. Turn the Drive down." [https://www.thegearpage.net/board/index.php?threads/i-have-to-say-im-a-little-upset.2205478/post-31553496]
# "IMO the designs are poor because... wait for it... they exhibit a papery buzz. The problem with most cathode biased Class A amps is, 1: they aren't really Class A (more like hot Class AB) and 2: They go into Class B operation when they are overdriven. The cathode capacitor charges up and the bias point shifts dramatically. This causes lots of crossover distortion (papery buzz). It's worse on lower notes because lower notes have more energy and charge the cap more. The is probably the reason Leo Fender switched to fixed bias amps with negative feedback. Fixed bias is just that, the bias point is fixed so the amp doesn't shift into Class B operation when overdriven (not as much anyways, depends on the bias circuit, grid stoppers, etc.). Negative feedback linearizes the amp and reduces the crossover distortion (at the expense of gain). That's why the buzzing went away when you increased negative feedback. Crossover distortion is a unique sound. For cleaner sounds it tends to be objectionable. For overdriven sounds some find it desirable. EVH ostensibly liked his amps biased cold to get some crossover distortion. There are even some amps that have circuits to intentionally generate crossover distortion. Some distortion pedals also do this. Lowering the Cathode Resistance reduces the crossover distortion as it keeps the amp in Class A operation longer but the tubes run hotter and don't last as long. This is not a problem with our virtual amps though. I forget the actual values but I'm pretty certain if you look at the Cathode Resistance value for those amps it's pretty high. This means the amps are biased somewhat cold to begin with and shift to very cold as soon as overdriven. One reason I like the AC-20 is that it runs the tubes hotter and exhibits less crossover distortion. The worst amp in this regard is the Badger 18. The cathode resistors are very large and the amp shifts into Class B operation early causing a spitty, buzzy distortion quality. This amp, however, is liked by many so that just goes to show that some people like that. It's like fuzz pedals. Some people like that spitty sound. I personally don't like it. Then there's shared vs. split cathode. If you look at the schematics on the web the Maz-38 is shared cathode. I could never get the model to sound exactly like our reference amp. Finally I traced the entire circuit and our particular amp is a split cathode. As soon as I changed the model to split cathode it was spot on. This is not exposed to the user though (there's a hidden shared/split switch)." [https://forum.fractalaudio.com/threads/papery-buzz-under-some-models.149193/page-2#post-1772639]
# "The Badger doesn't have a Bright switch." [https://forum.fractalaudio.com/threads/fixed-next-rel-wild-rumbling-chirping-artifacts-switching-between-presets.154544/post-1837842]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-suhr-badger-18-and-30.115086 Yek's write-up]

==SUHR BADGER 30 (Suhr Badger 30)==

==SUPER VERB NORMAL (1964 Fender Super Reverb, AB763)==

[[file:superreverb.jpg‎|300px]]

Models:
* Normal channel
* Vibrato channel

[[Cabinet models list | Cab:]] Fender 4x10 (C10R, C10Q, P10R)

Volume, Bass, Middle (Vibrato channel only), Treble, Bright switch, Reverb (not modeled), Vibrato (not modeled)

Power tubes: 6L6

# "I modeled the Super with V1 pulled as most people pull V1 so the amp has more grunt. Turn down the MV to make it cleaner."
# "The Super Reverb model is based on the amp with V1 removed (which is a common mod). This increases the level into the power amp by about a factor of two." [https://forum.fractalaudio.com/threads/xl-units-quantum-6-fw-austin-buddy-raw-amp-bank-part-i-feedback.123065/#post-1464566]
# "The Super Reverb model is "Diaz Modded". IOW, I pulled V1. This gives the amp a lot more gain so it's not surprising you're getting breakup at around 1.5. You can un-mod the model by turning down the MV Trim to around 0.5." [https://forum.fractalaudio.com/posts/851580]
# "A Pro Reverb is basically identical to a Super Reverb except for the speakers (and faceplate)." [https://forum.fractalaudio.com/posts/933261] And: "The Blackface Pro Reverb, model AA165, was virtually identical to the AB763 Super Reverb except for the speakers and tone stacks. If you use the Super Verb model and set the Tone Stack type to Blackface you'll basically have a Pro Reverb. Set the Mid control fairly high to emulate the fixed 6.8K mid resistor. I'd say around 7 or 8." [https://forum.fractalaudio.com/posts/1079578]
# (blackface) "Not a huge change with the Silverfaced versions. They're a little cleaner and brighter but the topology is the same. Some minor circuit changes here and there. Same transformers. The biggest change, IMO, was changing the PI resistors to 47K which gives you a little less gain in the PI." [https://forum.fractalaudio.com/posts/1252495]
# "The Super Reverb is really just a 50W version of a Twin Reverb with different speakers." [https://forum.fractalaudio.com/threads/wanted-amps-to-model.56753/page-4#post-713267]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-super-verb-64-blackface-fender-super-reverb-ab763.115124 Yek's write-up]

==SUPER VERB VIBRATO==

==SUPERTWEED (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "Original." [https://forum.fractalaudio.com/threads/supertweed.172803/post-2088909]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-supertweed-custom-model.115143/ Yek's write-up]

==SUPREMO TREM (Supro 1964T)==

[[File:supro.png|300px]]

Model:
* single model

[[Cabinet models list | Cab:]] Supro 2x12

Volume, Tone

Power tubes: 6973

# "They're simple amps with minimal tone shaping." [https://forum.fractalaudio.com/threads/time-for-another-supro.154552/post-1838288]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-supremo-trem-supro-1964t.115232/ Yek's write-up]

==TEXAS STAR CLEAN (MESA Lone Star Classic)==

[[file:lonestar.png|300px]]

Models:
* Clean channel
* Lead channel

[[Cabinet models list | Cab:]] Mesa 2x12 (C90)

Drive, Gain, Treble, Mid, Bass, Presence, Master, Voicing (not modeled)

Power tubes: 6L6

# (firmware 24.00) "Global MV controls have been added as the Channel MV in these amps affect the tone (and interacts with the Presence control)."

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-tx-star-mesa-lone-star.115405/ Yek's write-up]

==TEXAS STAR LEAD==

==THORDENDAL MODERN (custom model of MESA Dual Rectifier)==

[[file:meshuggah.jpg|300px]]

Models:
* Modern mode
* Vintage mode

Power tubes: 6L6

Notes: see Recto

# "The old Recto models weren't terribly accurate. When G3 came out the models were accurate but Fredrik contacted me and said something like "ahhhhh, I loved the old Recto model". So I took the old Recto models and made them "Thordendal" models." [http://forum.fractalaudio.com/threads/thordendal-modern-vs-recto-1-modern-red.91645/#post-1269530]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-thordendal-pre-g3-recto-models.115326/ Yek's write-up]

==THORDENDAL VINTAGE==

==TREMOLO LUX (blackface Fender Tremolux, AA763)==

[[File:tremolux.jpg|300px]]

Models:
* Normal channel
* Vibrato channel

[[Cabinet models list | Cab:]] Fender 2x10

Vibrato channel: Volume, Bright switch, Treble, Bass, Tremolo controls

Power tubes: 6L6

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-tremolo-lux-fender-blackface-tremolux-aa763.115354/ Yek's write-up]

==TRIPLE CREST 2 (MESA Triple Crown TC-100)==

[[file:triplecrown.jpg|300px]]

Models:
* Low gain channel
* High gain channel

Gain, Treble, Mid, Bass, Normal / Tight switch, Presence, Reverb (not modeled), Master, attenuator (not modeled)

Power tubes: EL34

# “The actual amp’s “Tight” switch engages a built-in Tube Screamer circuit which can be replicated using a Drive block or the Amp block’s internal Boost feature.” [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-04.159140/post-1901363]
# "The clean channel is like every other Mesa clean channel: a Blackface Fender copy." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-05.159156/post-1901965]
# "The clean channel uses the same built-in tube screamer as the other channels. There's a single fixed tube screamer circuit at the input of the amp. It can be switched in via relays which are controlled by the channel switches." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-05.159156/post-1904010]
# "A Mesa Triple Crown has a built-in Tube Screamer set clean on the input." [https://www.thegearpage.net/board/index.php?threads/looks-like-fractal-devices-are-getting-a-new-modeling-update-cygnus.2224849/post-32213988]
# "The Triple Crest models are based off a Mesa Triple Crown which is "derived from" a Fender Tonemaster." [https://forum.fractalaudio.com/threads/triple-crown-info.174892/post-2121012]

==TRIPLE CREST 3==

==TUBE PRE (generic tube preamp model)==

[[file:Logo small.png]]

Custom Fractal Audio model of a generic tube preamp

Power tubes: 5881 (power amp disabled)

# "The Vintage tone stack is a passive EQ model but it has a flat response when the controls are at noon. If you want "active" EQ you need to set the type to Active." [https://forum.fractalaudio.com/threads/is-it-possible-to-bypass-the-preamp.70487/page-2#post-865226]
# "If you only need power amp modeling, for example when using an external pre-amp through the Axe-Fx, use the Tube Pre model. It uses the Vintage tonestack which is flat when the tone controls are at noon."
# "The "Vintage" tone stack is flat. The Tube Pre model uses the Vintage tone stack." [https://forum.fractalaudio.com/threads/is-it-possible-to-bypass-the-preamp.70487/#post-865192]
# (firmware Ares 14.00) "The Tube Pre model has been changed so that the power amp is off by default."

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-tube-pre.115357/ Yek's write-up]

==TWO STONE J35 (Two-Rock Jet 35)==

[[file:jet35.jpg‎|300px]]

Models:
* Lead mode, Preamp Bypass (PAB) OFF
* Lead mode, Preamp Bypass ON (tone controls bypassed)

[[Cabinet models list | Cab:]] Two Stone 2x12 (G12-65)

Treble, Mid, Bass, Gain, Master, Lead Gain, Pull Bright. No Presence on the original amp, but the model has a Presence control

Power tubes: 6L6

# "It's very smooth but there's this unique chirp or something that I've never heard in an amp before. When you hit the note there's this blast of high end that rapidly decays so it has an almost vocal quality. The frequency shaping is very different than most other amps." [https://forum.fractalaudio.com/posts/745084]
# "The Two Rock is the most unique amp I've ever modeled. Almost like a violin but with this really cool chirp on the pick attack." [https://forum.fractalaudio.com/posts/747921]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-two-stone-j35-two-rock-jet-35.115377/ Yek's write-up]

==TWO STONE J35 PAB==

==USA BASS 400 1 (MESA Bass 400 bass amp)==

[[file:mesabass400.jpg|300px]]

Models:
* Bass Shift OFF
* Bass Shift ON

[[Cabinet models list | Cab:]] Mesa bass speaker cabinet

Bass, Middle, Treble, Pull Bright, Bass Shift, Treble Shift (not modeled), 7-band GEQ, Master, Volume

Power tubes: 6550

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-usa-bass-400-mesa-bass-400.115439/ Yek's write-up]

==USA BASS 400 2==

==USA MK IIC+ (MESA/Boogie Mark IIC+)==

[[file:iic+.jpg|300px]]

IIC+ models:
* Lead Master with Pull Bright engaged
* Lead Master with Pull Bright off
* Lead Master with Pull Deep engaged
* Lead Master with Pull Deep off

[[Cabinet models list | Cab:]] Mesa 1x12 (C90, EVM)

Volume (pull: Bright), Treble (pull: Shift = Fat), Bass (pull: Shift, not modeled), Middle, Presence, Master rhythm (pull: Deep), Lead Drive and Master Lead (pull: Bright)

Power tubes: 6L6

# "The mode in the Mark V is based on the later SimulClass version." [https://forum.fractalaudio.com/posts/910018]
# "If you want the sound of the non-SimulClass version set Triode 1 Plate Freq to 1350 Hz." [https://forum.fractalaudio.com/posts/910386]
# "The Pull Bright on the Volume knob is the classic "Bright Cap" which engages a capacitor across the potentiometer. This is already modeled in the Axe-Fx via the Bright Switch. The Pull Bright on the Lead Master knob engages a 0.22uF cap on the cathode of the last triode in the overdrive circuit. As there is no switch for this in the Axe-Fx it requires a separate model. Cathode caps are very common in tube amps. If the value is large the stage has more gain and the response is relatively flat. If the value is small the stage has more gain at higher frequencies. Amp designers use cathode caps to shape the frequency response. Caps in the range of 0.1 to 1.0 uF are commonly used to reduce bass response. A cathode cap works by decreasing the amount of negative feedback through shunting higher frequencies to ground. This reduced negative feedback increases the gain (and reduces linearity). FWIW the Axe-Fx is the only modeler of which I'm aware that actually models triodes using a feedback technique. Other modelers use static waveshapers. The Axe-Fx triode models incorporate feedback so if there is a virtual cathode cap the stage is less linear in addition to having more gain." [https://forum.fractalaudio.com/posts/1186462]
# "The IIC+ does not have a gain boost and doesn't need one. There is plenty of gain. The Pull Deep switch engages a large cathode cap on the final triode stage. With Pull Deep off there is actually a shelving response into the power amp (bass is reduced)."
# (to emulate Pull Shift on the Bass) "Put a Tilt EQ before the amp block with a frequency of 320 Hz and a gain of -3 dB. Set the Level to +3 dB." [https://forum.fractalaudio.com/posts/1202633]
# "I have a Mark IIC+, a Mark IV, a Mark V and a Triaxis. They're all completely different. Mesa always says things like "sounds the same as a IIC+" but the circuits are different and, probably most important, the knob tapers are completely different." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-2-00-public-beta-numero-tres.109852/page-6#post-1315609]
# "The key to a good Boogie sound, IMO, is the Fat Switch. This is the treble Pull Shift on the IIC+ and the Pull Fat on the Mark IV. Mesa knew this and the Lead 2 modes on the Triaxis all had the treble shift engaged by default."
# "I always used the Fat switch with the real amp." (IIC+) [http://forum.fractalaudio.com/threads/mark-iic-amp-model-issues.121463/page-2#post-1446683]
# "On a Mark IV (at least on our reference amp) all three controls have a Log10A taper. On a Mark V the tapers are different so you get more midrange and treble for the same settings. Channel 3 on a Mark V is virtually identical to the Mark IV Lead channel except for the pot tapers." [https://forum.fractalaudio.com/threads/question-about-the-mark-series-graphic-eq-modeling.149223/post-1771767]
# "The IIC++ amp model is the same as the IIC+ with different tapers." [https://forum.fractalaudio.com/threads/question-about-the-mark-series-graphic-eq-modeling.149223/post-1770773]
# "The tone stack on a Boogie is pre-distortion. As you increase gain you want less bass into the distortion stages so the idea is you turn the bass down. In later versions of the Boogies (TriAxis for example) they changed the taper so that noon was equivalent to 1 on earlier models because people are reticent to move controls very far from noon for some weird reason." [https://forum.fractalaudio.com/threads/highly-compressed-sound-on-high-gain-amps.169132/post-2032825]
# "I begrudgingly dragged the amp out of storage today (as it weighs a metric ton) and repeated the measurements and did some A/B tests. As expected the models are extremely accurate. That being said it is a bear to dial in. Here are some tips:
#* The old version of the model incorrectly referenced the Mark IV tone stack. These tone stacks are identical except for the taper of the mid pot. The IIC+ has a linear pot and the Mark IV has a Log10 pot. I had it backwards in my earlier comments. My guess is that Mesa found that turning the midrange down sounds best (and it does) so they changed the pot taper to do this automatically since noon on a Log10 pot is equal to a 1.0 on a linear pot.
#* Commensurate with (1) I found myself turning the midrange down as well as the bass and turning the treble up.
#* I think the default Master Volume value is a bit high so you may want to turn that down. I've reduced the default for Quantum 2.03.
#* Turn the bright switch on. Every bit of information I've found says that people typically used the Pull Bright on the Volume knob. This is equivalent to the Bright switch under the Treble control on the model. I always turn it on and I've set it on by default for Q2.03.
#* USE THE EQ. The tone stack is pre-distortion which is atypical for a high-gain amp. Tone stacks are almost always post-distortion. Since the tone stack is pre-distortion you need to do your post distortion tone shaping using the EQ. The tone controls set the feel and the distortion texture, the EQ shapes the final tone. I like to do a gentle V-curve.
#* These were my settings for a killer high-gain tone: Model: USA IIC+ / Input Drive: 8.1 / Overdrive: 9-10 / Bass: 1.0 / Midrange: 1.8 / Treble: 8.9 / Presence: 4.5 / MV: 4.0 / Level: -20 dB / Bright Switch ON / 80 Hz: 4.8 / 240 Hz: 2.6 / 750 Hz: -4.5 / 2200: -0.2 / 6600: 0." [http://forum.fractalaudio.com/threads/mark-iic-tips.112378]
# "Treble Shift on the Tone page of USA IIC+ models is an alias of the “Fat” control found on the Preamp page and performs the same function." (firmware 22)
# "The Mark series graphic EQ sucks. I know some people want authenticity but it's simply a bad design." [https://thegearforum.com/threads/fractal-audio-firmware-update-thread.673/post-154508]
# "The "Gain" control on a Mark V is equivalent to the Overdrive control on a Mark II/IV. The actual gain control on a Mark V is fixed (same as the JPIIC+). In the Axe-Fx you can actually change the Gain control using the Ideal tone controls. You'll see that when choosing the model it will be initialized to a value (4.4 for the Mark V)." [https://thegearforum.com/threads/fractal-audio-firmware-update-thread.673/page-119#post-154512]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-usa-iic-mesa-boogie-mark-iic.115442/ Yek's write-up]

==USA MK IIC+ BRIGHT==

==USA MK IIC+ DEEP==

==USA MK IIC+ DEEP BRIGHT==

==USA MK IIC++ (custom model of MESA/Boogie IIC+)==

[[File:Logo small.png]]

Formerly: METALLICA USA IIC++

This is not a model of Hetfield's own "crunchberries" amp, nor a model of a IIC+ with the IIC++ mod. It's the IIC+ model with different tapers. This was requested by Metallica's engineers after the main IIC+ models were updated, and it's part of Metallica's live sound.

Notes: see USA IIC+

# (from Metallica engineers) "This model is part of our live sound. This amp was removed when the new MKII models were added and firmware updated. I asked if it could be ported for Q3 as I was having a difficult time migrating to the updated firmware and retaining our earlier work." [https://forum.fractalaudio.com/threads/metallica-amp.115857/page-2#post-1384750]
# "The IIC++ amp model is the same as the IIC+ with different tapers." [https://forum.fractalaudio.com/threads/question-about-the-mark-series-graphic-eq-modeling.149223/post-1770773]

==USA JP IIC+ Green (MESA/Boogie JP-2C)==

[[File:Jp2c.jpg|300px]]

JP-2C models:
* Green: channel 1
* Red: channel 3
* Red: channel 3, Shred mode
* Yellow: channel 2
* Yellow: channel 2, Shred mode

Channel 1 (Mark IIC+ Clean): Gain, Master, Presence, Treble, Mid, Bass, Mid/Boost switch, graphic EQ, reverb (not modeled)

Channel 2 (Mark IIC+ Gain/Shred): (Pull) Gain, Master, (Pull) Presence, Treble, Mid, Bass, graphic EQ (not modeled), Shred mode switch

Channel 3 (Mark IIC+ Gain/Shred): (Pull) Gain, Master, (Pull) Presence, Treble, Mid, Bass, graphic EQ (not modeled), Shred mode switch

Power tubes: 6L6

# "The JP amp has a fixed input gain control. The "Gain" control on the amp is actually an Overdrive control. If you use Authentic controls there is no Input Gain on "Gain"." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-03.149363/page-3#post-1772020]
# "Presence Shift is Presence pull. Tone stack effectively has fat switch on." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-05.149428/page-10#post-1775746]
# (difference between the "JP Green" and "USA Clean") "JP has less gain and a much larger midrange potentiometer." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-06.149775/page-2#post-1777979]
# "JP himself gave the models his stamp of approval." [http://forum.fractalaudio.com/threads/i-am-confused-about-the-jp2c.153540/post-1826396]
# "JP (Green) has less gain (than USA Clean) and a much larger midrange potentiometer." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-06.149775/post-1777979]
# "Those are great amps. The particular amp used for the models was John Petrucci's personal recording amp. I didn't want to give it back and offered to buy it from him but he wouldn't sell it." [https://www.thegearpage.net/board/index.php?threads/fractal-fm3-reviews-tones-questions.2124913/post-31011638]
# "It's not that the Graphic EQ isn't the same, the TAPERS are not the same. On the real amp the controls do virtually nothing until you get near the ends of the range. If you move a slider to, say, 3/4 of its range it does almost nothing. If you were to set the model's slider to the same position you would get significantly more boost. I didn't model the nonlinear slider behavior because IMO it's a design flaw. Graphic EQs should have a nice, linear-in-dB response. Otherwise the graphic EQ is very accurate. The frequency and Q behavior is spot-on. If you have pulled the presence knob on the amp you have to activate the Presence Shift on the model. Otherwise they will sound VERY different. Presence shift gives a much more focused sound. I always use the Presence Shift. You can't compare the amp with a switch engaged to the model without the equivalent switch engaged. Of course it will sound different. The tapers of the other controls should be very close including the Presence and Master Volume. (...) JP himself was very impressed with the model and the model was matched to his PERSONAL head that he sent me." [https://forum.fractalaudio.com/threads/real-jp2c-vs-axe-fx-3-sim-comparison.168942/post-2029916]</blockquote>
# "I thought that Shred mode is the same as the Red mode on the Triaxis which is just a treble boost on the output when, in fact, it's a clean boost on the input similar to a Tube Screamer but without the treble rolloff." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486/post-2067465]
# (about the fixed internal gain) "Yellow is 2.9. Red is 5.7." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486/post-2067603]
# "JP2C doesn't have a depth knob. If a knob isn't present in the Authentic menu then it may not do anything in the Ideal menu." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-16-01-beta-1-public-beta.172736/post-2088439]
# "USA JP models have a fixed Input Drive so when switching to the models the Input Drive is reset to the default value. The Input Drive knob is not visible in the Authentic menu." [https://forum.fractalaudio.com/threads/bug-presence-not-working-at-the-usa-lead-models-triaxis-16-1-b.172777/post-2088655]
# "A JP IIC+ is not a Mark IV. They sound different. The biggest difference is in the behavior of the Presence Shift. With the Presence Shift on the JP IIC+ will be very similar to the Mark IV with its Presence Shift on. With the Presence Shifts off they are very different sounding." [https://forum.fractalaudio.com/threads/jp-ii-c-red-sounds-muffled-compared-to-mk-iv-mid-gain-in-fw-21-00-with-audio-and-preset.191858/post-2385695]
# "All these amps have the same basic circuit with minor differences. The only unique thing I've encountered in all my tests is the function of the Presence Shift pull on the JP2C. It's different than the pull shift on the other Mark amps." [https://forum.fractalaudio.com/threads/mesa-mark-iic-mark-iic-mark-vii-the-jp2c-mark-iic.192824/post-2398526]
# "The Mark series graphic EQ sucks. I know some people want authenticity but it's simply a bad design." [https://thegearforum.com/threads/fractal-audio-firmware-update-thread.673/post-154508]
# "The "Gain" control on a Mark V is equivalent to the Overdrive control on a Mark II/IV. The actual gain control on a Mark V is fixed (same as the JPIIC+). In the Axe-Fx you can actually change the Gain control using the Ideal tone controls. You'll see that when choosing the model it will be initialized to a value (4.4 for the Mark V)." [https://thegearforum.com/threads/fractal-audio-firmware-update-thread.673/page-119#post-154512]

==USA JP IIC+ Red==

==USA JP IIC+ Red Shred==

==USA JP IIC+ Yellow==

==USA JP IIC+ Yellow Shred==

==USA MK IV LEAD / RHYTHM (MESA/Boogie Mark IV)==

[[file:markiv.jpg|300px]]

Mark IV models:
* Rhythm 1 channel (previously: USA Clean model)
* Rhythm 2 channel
* Lead channel, Voicing: Harmonics, Pull Bright: engaged
* Lead channel, Voicing: Mid Gain, Pull Bright: engaged
* Lead channel, Voicing: Harmonics, Pull Bright: off
* Lead channel, Voicing: Mid Gain, Pull Bright: off

[[Cabinet models list | Cab:]] Mesa 1x12 (C90, V30)

Gain, Lead Drive, Treble, Bass, Mid, Presence, Master, graphic EQ, Pentode/Triode switch, Class-A/Simul-Class switch, Voicing switch (Mid Gain / Harmonics), Variac

Rhythm 1 channel: Pull Bright

Rhythm 2 channel: Pull Fat, Presence Shift

Lead channel: Pull Bright, Pull Fat, Presence Shift

Power tubes: 6L6

# "The MK V is basically a compendium of previous Mesa amps. There may be minor differences in tone due to circuit layout but nothing a few tweaks to the EQ can't fix." [https://forum.fractalaudio.com/posts/573437]
# “A Mark V is a greatest hits of the Mark IV and IIC+. You already have all those models.” [https://forum.fractalaudio.com/threads/wish-list-new-amps.137944/post-1991426]
# "Having owned multiple Mark IV's, multiple Triaxis's and a variety of other Boogie products, I can tell that the Mark series in general are a bitch to dial in. Once you figure them out though they are great amps. IMO, the key to a MKIV is to use the TMB to get the feel and the EQ to get the tone."
# "If it isn't Mid Gain then it's Harmonics." [https://forum.fractalaudio.com/posts/1165578]
# "The Depth knob is inactive on that amp model. The real amp doesn't have one either." [https://forum.fractalaudio.com/posts/1205835]
# "Fat and Presence shift work as the real amp." [https://forum.fractalaudio.com/posts/1246666]
# "USA Clean is based on the MKIV." [http://forum.fractalaudio.com/threads/mesa-iic-clean-channel.106851/#post-1280186]
# "With the presence control at noon it's roughly neutral. Turn it down and you are actually boosting bass and reducing treble." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-1-03-firmware-release.106931/page-12#post-1282192]
# "I have a Mark IIC+, a Mark IV, a Mark V and a Triaxis. They're all completely different. Mesa always says things like "sounds the same as a IIC+" but the circuits are different and, probably most important, the knob tapers are completely different." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-2-00-public-beta-numero-tres.109852/page-6#post-1315609]
# "The key to a good Boogie sound, IMO, is the Fat Switch. This is the treble Pull Shift on the IIC+ and the Pull Fat on the Mark IV. Mesa knew this and the Lead 2 modes on the Triaxis all had the treble shift engaged by default."
# "There isn't any way to run the virtual power tubes in triode mode... but you can change the Power Tube Type to "300B" which is a triode. When you run a pentode (or beam tetrode) in triode mode you connect the screen to the anode which effectively defeats the screen. This lowers the output impedance of the plate significantly which, in turn, lowers the output impedance of the amp itself making the voltage output less dependent on the speaker impedance. Using the 300B tube type should get you pretty close." [http://forum.fractalaudio.com/threads/mesa-mark-iv-pentode-triode-switch.122527/#post-1458293]
# (about the GEQ) "The range of the sliders is the same as the amp. The taper is not. The amp is much more abrupt since it uses linear taper (should use 'S'-taper)." [https://forum.fractalaudio.com/threads/question-about-the-mark-series-graphic-eq-modeling.149223/post-1769764]
# (about the difference between the "JP Green" and "USA Clean") "JP has less gain and a much larger midrange potentiometer." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-06.149775/page-2#post-1777979]
# (simulate Class-A mode) "Turn Power Tube Grid Bias all the way up." [https://forum.fractalaudio.com/threads/mesa-mk-4-class-a-possible.154438/post-1836241]
# "The tone stack on a Boogie is pre-distortion. As you increase gain you want less bass into the distortion stages so the idea is you turn the bass down. In later versions of the Boogies (TriAxis for example) they changed the taper so that noon was equivalent to 1 on earlier models because people are reticent to move controls very far from noon for some weird reason." [https://forum.fractalaudio.com/threads/highly-compressed-sound-on-high-gain-amps.169132/post-2032825]
# "A JP IIC+ is not a Mark IV. They sound different. The biggest difference is in the behavior of the Presence Shift. With the Presence Shift on the JP IIC+ will be very similar to the Mark IV with its Presence Shift on. With the Presence Shifts off they are very different sounding." [https://forum.fractalaudio.com/threads/jp-ii-c-red-sounds-muffled-compared-to-mk-iv-mid-gain-in-fw-21-00-with-audio-and-preset.191858/post-2385695]
# "Mark V is the same thing as a Mark IV w/ a few extra features. They sound virtually identical." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-02.191637/post-2382608]
# "The amp uses linear taper sliders. The ideal taper for this type of circuit is S-taper. S-taper will give you approximately linear-in-dB. The Axe-Fx III is precisely linear-in-dB." [https://forum.fractalaudio.com/threads/mark-series-eq.191595/post-2389621]
# "The Mark series graphic EQ sucks. I know some people want authenticity but it's simply a bad design." [https://thegearforum.com/threads/fractal-audio-firmware-update-thread.673/post-154508]
# "The "Gain" control on a Mark V is equivalent to the Overdrive control on a Mark II/IV. The actual gain control on a Mark V is fixed (same as the JPIIC+). In the Axe-Fx you can actually change the Gain control using the Ideal tone controls. You'll see that when choosing the model it will be initialized to a value (4.4 for the Mark V)." [https://thegearforum.com/threads/fractal-audio-firmware-update-thread.673/page-119#post-154512]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-usa-clean-lead-rhythm-mesa-boogie-mark-iv.115440/ Yek's write-up]

==USA MK IV LEAD BRIGHT==

==USA MK IV LEAD MID GAIN==

==USA MK IV LEAD MID GAIN BRIGHT==

==USA MK V GREEN (MESA/Boogie Mark V)==

==USA MK V RED IIC+==

==USA MK V RED IIC+ Bright==

==USA MK V RED MKIV==

==USA MK V RED MKIV Bright==

==USA MK V RED XT==

==USA MK V RED XT Bright==

==USA PRE CLEAN (MESA TriAxis preamp)==

[[file:triaxis.png|300px]]

Triaxis models:
* Rhythm Green
* Lead 1 Red (TX-4 board)
* Lead 2 Green
* Lead 2 Red
* Lead 2 Yellow

Drive, Lead Drive, Treble, Middle, Bass, Presence (preamp, on Lead 2 models), Dynamic Voice EQ (not modeled)

Power tubes: same as USA Lead model (6L6)

# "I used a Triaxis for, shoot, I dunno, over a decade before designing the Axe-Fx. I have two of them. So I'd say I'm pretty familiar with the tones. To my ears (and my measurement equipment), the Axe-Fx models are spot-on."
# "I can nail the sound of my Triaxis now by setting it (Bright) around 9:00 - 10:00." [https://forum.fractalaudio.com/posts/1001906] And: "10 on the Triaxis would be 0 dB on the Bright parameter. Anything below 10 is equivalent to less than noon on the Bright parameter. The "Presence" control on a Triaxis is always a hi cut, it never boosts. The Bright parameter is not an exact match to the Triaxis Presence control though. It is a fixed shelving filter. The Triaxis Presence control is passive so the center frequency changes with the amount of cut. It also changes the load on the plate which distorts the frequency response a bit too. The Presence parameter should be set to 5.00, which is neutral (see the manual for details)."
# "I have a Mark IIC+, a Mark IV, a Mark V and a Triaxis. They're all completely different. Mesa always says things like "sounds the same as a IIC+" but the circuits are different and, probably most important, the knob tapers are completely different." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-2-00-public-beta-numero-tres.109852/page-6#post-1315609]
# "The key to a good Boogie sound, IMO, is the Fat Switch. This is the treble Pull Shift on the IIC+ and the Pull Fat on the Mark IV. Mesa knew this and the Lead 2 modes on the Triaxis all had the treble shift engaged by default."
# "Mesa claims it's based on the IIC+ but it's different. The bright cap is different, the mid resistor is much greater, the source impedance of the drive "pot" is different, etc., etc, etc." [http://forum.fractalaudio.com/threads/three-hours-with-the-usa-pre-ld2-yellow.111624/#post-1335224]
# (firmware Quantum 7) "The USA Pre models now all use a MarkIV power amp model. The 2:90 power amp is basically the same as a MarkIV and does have a presence shift but it's accessed through a jack on the back (Voicing)." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-00-firmware-release.124944/page-15#post-1487194]
# "I gigged with a Triaxis for years. I never put Dynamic Voice above 1.0. Despite it's name, DV is just an EQ. It's the 5-band graphic EQ from the mark series with the potentiometers replaced by LDRs. It's really just a bunch of EQ presets and it interpolates between them as you increase the value." [http://forum.fractalaudio.com/threads/triaxis-model-live-use.147163/#post-1740122]
# "I have two of them. Both with the Lead 1 Red board." [https://forum.fractalaudio.com/threads/the-triaxis-is-spot-on.151673/post-1804830]
# "On our reference Triaxis (both of them) the Presence control doesn't do anything for the Clean and LD1 modes. The model's Presence knob is therefore the Power Amp Presence." [https://forum.fractalaudio.com/threads/triaxis-usa-pre-models-inconsistencies-in-controls.156431/post-1862912]
# "That's how our reference amps work. They are the later models with the TX4 board (different LD2 Red). When using the LD1 modes the Presence control doesn't do anything and is as if the control were at 10." [https://forum.fractalaudio.com/threads/triaxis-usa-pre-models-inconsistencies-in-controls.156431/post-1865080]
# "The tone stack on a Boogie is pre-distortion. As you increase gain you want less bass into the distortion stages so the idea is you turn the bass down. In later versions of the Boogies (TriAxis for example) they changed the taper so that noon was equivalent to 1 on earlier models because people are reticent to move controls very far from noon for some weird reason." [https://forum.fractalaudio.com/threads/highly-compressed-sound-on-high-gain-amps.169132/post-2032825]
# "Based on the Lead 1 Red mode of a Mesa Triaxis preamp with the TX-4 board."
# In "Cygnus" amp modeling firmware the Lead models have an authentic Preamp Presence control (not in the Lead 1 model).
# "I gigged a Triaxis for years and I would have the knobs pretty much at noon (5.0). The Triaxis is a Mark IV preamp under the hood but with very different tapers on the "pots". I.e., with BMT at 5.0 on the Triaxis the MKIV would be something like 1.0, 6.0, 6.0. I'm just going by memory here but the point being that the bass control on the Triaxis doesn't need to be turned way down like you would on a Mark series." [https://forum.fractalaudio.com/threads/bad-experience-with-choptones-i-need-a-2nd-opinion-watch-screenshots-plz.191948/post-2386734]
# "The Triaxis used LDRs as variable resistance elements. There were resistor strings that were used to set the LDRs but those resistors weren't in the signal path." [https://forum.fractalaudio.com/threads/5150-presence-knob.199908/page-17#post-2494019]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-usa-pre3-mesa-boogie-triaxis.115478/ Yek's write-up]

==USA PRE LD1 RED==

==USA PRE LD2 GREEN==

==USA PRE LD2 RED==

==USA PRE LD2 YELLOW==

==USA MK IV RHYTHM 1==

==USA MK IV RHYTHM 2==

==USA SUB BLUES (MESA Subway Blues)==

[[file:subwayblues.png|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Mesa 1x10 (Eminence Black Shadow), DynaCab available

Volume, Bass, Mid, Treble, FAT switch, Reverb (not modeled)

Power tubes: EL84

# "The Subway Blues model was completely redone. It will likely sound different than before." [https://forum.fractalaudio.com/threads/bug-mesa-subway-blues-very-different-in-ares-15-01-vs-cygnus-16-00.172363/post-2082472]
# "The reference amp is the later, single input version. The Fat switch replicates the amp's Fat switch." [https://forum.fractalaudio.com/threads/bug-mesa-subway-blues-very-different-in-ares-15-01-vs-cygnus-16-00.172363/post-2088907]

[http://forum.fractalaudio.com/threads/usa-sub-blues-mesa-boogie-subway-blues.115479/ Yek's write-up]

==VIBRA-KING (custom Fender Vibro-King)==

[[file:vibro-king.jpg|300px]]

Models:
* Fat switch ON
* Fat switch OFF

Volume, Treble, Bass, Middle, Fat switch, Tremolo, Reverb (not modeled)

[[Cabinet models list | Cab:]] Fender 3x10

Power tubes: 6L6

# "The model is based on the custom version which has higher plate voltages which causes more overdrive on the power tubes."

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-vibra-king-custom-fender-vibro-king.115485/ Yek's write-up]

==VIBRA-KING FAT==

==VIBRATO LUX (1962/1963 brownface Fender Vibrolux, 6G11)==

[[file:vibrolux.jpg|300px]]

Model:
* Bright channel (Normal channel: Bright OFF)

[[Cabinet models list | Cab:]] Fender 2x10 or 1x12

Vibrato channel: Volume, Bass, Treble, Vibrato (not modeled)

Power tubes: 6L6

# "Early Dire Straits tone is a Vibrolux (Vibrato Lux model). The Vibrato Lux model is based on the same model and year amp used on the eponymous album. There's a cab in there too." [https://forum.fractalaudio.com/posts/1111550]
# "It's a Vibrolux. That IR is from my personal 1962 Vibrolux. This is the amp used on Dire Straits eponymous album." [https://forum.fractalaudio.com/threads/vibrolux-g3-with-the-new-ir-is-just-ridiculous.97866/#post-1174387]
# "It's a Brownface." [https://forum.fractalaudio.com/threads/brownface-deluxe-or-closest-thing-to-it.80014/#post-973252]
# "Our reference amp is the same model Mark Knopfler used on the Dire Straits eponymous album. Match made in heaven with a Strat." [https://forum.fractalaudio.com/threads/definitely-a-problem.173700/post-2103923]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-vibrato-lux-fender-vibrolux-6g11.115713/ Yek's write-up]

==VIBRATO VERB (Fender Vibroverb)==

[[image:vibroverb.jpg|300px]]

Vibroverb models:
* Vibrato Verb: old model ported from the Axe-Fx Ultra
* Vibrato Verb AA: based on Cliff’s own 1964 blackface Vibroverb with AA763 circuit
* Vibrato Verb AB: based on AB763 circuit
* Vibrato Verb Custom: based on Custom Reissue

[[Cabinet models list | Cab:]] Fender 1x15 (Jensen C15N, JBL D130, Eminence)

Volume, Bass, Treble, Bright switch, Reverb (not modeled), Tremolo

Power tubes: 6L6

# "The Transformer Matching value for the CS model is based on the output transformer in the actual amp. Legend has it that SRV used a Bassman transformer which would lead to significant overmatching. To replicate this increase Xfrmr Match to around 1.8."
# "Some different component values in the AA vs. AB." [https://forum.fractalaudio.com/threads/vibrato-verb-models-explained.192318/post-2391593]
# "The 1x15 Vibroverb is a D130." [https://forum.fractalaudio.com/threads/what-dyna-cab-models-would-you-like-to-see-added.193380/post-2404043]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-vibrato-verb-fender-vibroverb.115734/ Yek's write-up]

==VIBRATO VERB AA (1964 blackface Fender Vibroverb, AA763)==

==VIBRATO VERB AB (Fender Vibroverb, AB763)==

==VIBRATO VERB CUSTOM (Fender Vibroverb Custom Reissue)==

==WRECKER EXPRESS (Trainwreck Express)==

[[file:trainwreck.jpg|300px]]

Models:
* Wrecker Express: Bright switch on original amp in center or top position
* Wrecker Express Bright: Bright switch on original amp in bottom (brightest) position

[[Cabinet models list | Cab:]] Marshall 4x12 (G12-M25)

Power tubes: EL34

Volume, Bass, Mid, Treble, Presence, three-position Bright switch (center: off, top: clarity and sparkle, bottom: jangly highs)

# "The secret to a Trainwreck is the output transformer. The impedance ratio is about twice that of other amps. I.e. typical 50W Marshall has a primary impedance of about 3200 ohms. A Trainwreck is about 6500 ohms. The causes the power tubes to clip much sooner." [https://forum.fractalaudio.com/posts/1116254]
# "Real Trainwrecks are very spitty amps. This is because the last stage heavily overdrives the phase inverter. 7.02 is faithful to the actual amps whereas previous firmwares were more idealized. As was indicated in the release notes you can dial out this behavior by decreasing the PI Bias Shift. If you set it to zero it will be like 6.xx." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-02-firmware-release.125625/page-17#post-1498318]
# [https://forum.fractalaudio.com/threads/trainwreck-express-tweaks.154796/post-1841547 Cliff's Tech Note]: "A real Trainwreck Express is a fizzy, spitty amp. Some people like this. The same people who like fuzz pedals and that quasi-half-wave rectified sound. Personally I like more clarity. The reason the Express is like this is primarily due to the last triode stage before the phase inverter (PI). This stage is biased very cold and drives the PI very hard due to the lack of any limiting resistor (grid stopper) between the triode and PI. The lack of a grid stopper resistor and large coupling capacitor create significant bias excursion (blocking distortion). It appears the designer attempted to minimize the bias excursion by biasing the triode cold which limits its positive excursion and therefore limits the PI grid conduction. Despite the cold bias point the PI grid is still heavily overdriven resulting in massive blocking distortion. The Axe-Fx allows you to reduce the amount of block distortion via the PI Bias Excursion parameter. Simply turn this down and the spittiness will go away. You can then also rebias the triode via the Preamp Bias parameter. Values closer to zero result in a more symmetric waveform." (...) "Turn PI Bias Excursion to 0. Set Preamp Bias to -0.15 or so. [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841487]"
# "The reason they clean up when you back off the volume is because the OT is so overmatched. It's about twice the optimum value." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841485]
# "The real amp is a nasty thing. Very spitty as one would expect given the lack of a grid stopper resistor between the last triode stage and the PI." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841549]
# "Got out the reference amp and it sounds the same. For all the hoopla surrounding Trainwrecks they're actually pretty bad designs. Tons of blocking distortion in the PI. If you don't want all that blocking distortion turn down PI Bias Excursion." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/page-4#post-1841474]
# "Turning down PI Bias Excursion yields the ultimate Trainwreck. Sounds much better than the real amp. I also adjusted the Preamp Bias so it wasn't so off-center." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/page-4#post-1841480]
# "The only difference (between the two Express models) is the Bright Cap. An Express (at least mine) has a three-position switch: Off, 100 pF, 500 pF. The amp block only supports Off and On and I figured people wouldn't know the fine details so a separate model seemed the easiest solution. Of course you can vary the Bright Cap but you'd have to know that the real amp has two caps, etc." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-10-01.154923/post-1843572]
# "That amp exhibits a lot of blocking distortion (in the phase inverter) due to its design. You can reduce this via either the PI Bias Excursion or Master Bias Excursion parameters. Another option is to use the FAS Express model which puts some resistors between the last triode stage and the PI to reduce the bias excursion." [https://forum.fractalaudio.com/threads/blocking-distortion-found-in-trainwreck-express.182895/post-2247268]
# "I got out my Trainwreck Express and compared it to the model last night and it's spot-on. Nasty, spitty, Neil Young-esque blocking distortion and all." [https://forum.fractalaudio.com/threads/blocking-distortion-found-in-trainwreck-express.182895/post-2247538]
# "That's what amps do. You don't hear it through a guitar cab typically but using close-mic'd IRs it's more noticeable. You can reduce it by turning on the Plate Suppressor diodes. Trainwrecks have plate suppressor diodes for just this reason." [https://forum.fractalaudio.com/threads/note-decay-crackle-sizzle-noise.193575/post-2407689]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-wrecker-express-trainwreck-express.115740/ Yek's write-up]

==WRECKER EXPRESS BRIGHT==

==WRECKER LIVERPOOL (Trainwreck Liverpool)==

[[file:trainwreck.jpg|300px]]

Models:
* Liverpool: Bright switch on original amp in center or top position
* Liverpool Bright: Bright switch on original amp in bottom (brightest) position

[[Cabinet models list | Cab:]] Marshall 4x12 (G12-M25)

Volume, Bass, Mid, Treble, Presence, three-position Bright switch (center: off, top: clarity and sparkle, bottom: jangly highs)

Power tubes: EL84

# "The secret to a Trainwreck is the output transformer. The impedance ratio is about twice that of other amps. I.e. typical 50W Marshall has a primary impedance of about 3200 ohms. A Trainwreck is about 6500 ohms. The causes the power tubes to clip much sooner." [https://forum.fractalaudio.com/posts/1116254]
# "Just because a power amp is "Class A" doesn't mean it can't have negative feedback. True that the majority do not but this particular amp has quite a bit of NF." [http://forum.fractalaudio.com/threads/wrecker-liverpool-neg-feedback-bug.116224/#post-1389082]
# "Uses a Vox-style phase inverter." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-00-public-beta.123082/page-7#post-1464730]
# "Real Trainwrecks are very spitty amps. This is because the last stage heavily overdrives the phase inverter. 7.02 is faithful to the actual amps whereas previous firmwares were more idealized. As was indicated in the release notes you can dial out this behavior by decreasing the PI Bias Shift. If you set it to zero it will be like 6.xx." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-02-firmware-release.125625/page-17#post-1498318]
# [https://forum.fractalaudio.com/threads/trainwreck-express-tweaks.154796/post-1841547 Cliff's Tech Note]: "A real Trainwreck Express is a fizzy, spitty amp. Some people like this. The same people who like fuzz pedals and that quasi-half-wave rectified sound. Personally I like more clarity. The reason the Express is like this is primarily due to the last triode stage before the phase inverter (PI). This stage is biased very cold and drives the PI very hard due to the lack of any limiting resistor (grid stopper) between the triode and PI. The lack of a grid stopper resistor and large coupling capacitor create significant bias excursion (blocking distortion). It appears the designer attempted to minimize the bias excursion by biasing the triode cold which limits its positive excursion and therefore limits the PI grid conduction. Despite the cold bias point the PI grid is still heavily overdriven resulting in massive blocking distortion. The Axe-Fx allows you to reduce the amount of block distortion via the PI Bias Excursion parameter. Simply turn this down and the spittiness will go away. You can then also rebias the triode via the Preamp Bias parameter. Values closer to zero result in a more symmetric waveform." (...) "Turn PI Bias Excursion to 0. Set Preamp Bias to -0.15 or so. [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841487]"
# (about the Tech Note) "Applies to the Liverpool because the preamp is almost identical to the Express." [https://forum.fractalaudio.com/threads/trainwreck-express-tweaks.154796/post-1842967]
# "The reason they clean up when you back off the volume is because the OT is so overmatched. It's about twice the optimum value." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841485]
# "Turning down PI Bias Excursion yields the ultimate Trainwreck. Sounds much better than the real amp. I also adjusted the Preamp Bias so it wasn't so off-center." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/page-4#post-1841480]
# "That's what amps do. You don't hear it through a guitar cab typically but using close-mic'd IRs it's more noticeable. You can reduce it by turning on the Plate Suppressor diodes. Trainwrecks have plate suppressor diodes for just this reason." [https://forum.fractalaudio.com/threads/note-decay-crackle-sizzle-noise.193575/post-2407689]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-wrecker-liverpool-trainwreck-liverpool.115741/ Yek's write-up]

==WRECKER LIVERPOOL BRIGHT==

==WRECKER ROCKET (Trainwreck Rocket)==

[[file:trainwreck.jpg|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Marshall 4x12 (G12-M25)

Volume, Treble, Bass, Cut

Power tubes: EL84

# "The secret to a Trainwreck is the output transformer. The impedance ratio is about twice that of other amps. I.e. typical 50W Marshall has a primary impedance of about 3200 ohms. A Trainwreck is about 6500 ohms. The causes the power tubes to clip much sooner." [https://forum.fractalaudio.com/posts/1116254]
# "The Rocket has a different preamp (than the Express) with the tone stack before the PI. This reduces the signal level substantially and lessens the amount of blocking distortion." [https://forum.fractalaudio.com/threads/trainwreck-express-tweaks.154796/post-1842967]
# "The reason they clean up when you back off the volume is because the OT is so overmatched. It's about twice the optimum value." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841485]
# "Real Trainwrecks are very spitty amps. This is because the last stage heavily overdrives the phase inverter. 7.02 is faithful to the actual amps whereas previous firmwares were more idealized. As was indicated in the release notes you can dial out this behavior by decreasing the PI Bias Shift. If you set it to zero it will be like 6.xx." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-02-firmware-release.125625/page-17#post-1498318]
# "Turning down PI Bias Excursion yields the ultimate Trainwreck. Sounds much better than the real amp. I also adjusted the Preamp Bias so it wasn't so off-center." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/page-4#post-1841480]
# "That's what amps do. You don't hear it through a guitar cab typically but using close-mic'd IRs it's more noticeable. You can reduce it by turning on the Plate Suppressor diodes. Trainwrecks have plate suppressor diodes for just this reason." [https://forum.fractalaudio.com/threads/note-decay-crackle-sizzle-noise.193575/post-2407689]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-wrecker-rocket-trainwreck-rocket.114726/ Yek's write-up]

[[category:Axe-Fx2]]
[[category:Axe-Fx3]]
[[category:FM3]]
[[category:FM9]]
[[category:AX8]]
[[category:Sounds]]
[[category:All]]

Amp block

2023-12-09T06:59:06Z

James-F: /* SPEAKER COMPLIANCE */

__TOC__
[[image:H_amps.png|link=]]
=The Amp block=

==Available on which products==

* '''Axe-Fx III''': 2 blocks
* '''FM3''': 1 block
* '''FM9''': 2 blocks
* '''Axe-Fx II''': 2 blocks
* '''AX8''': 1 block
* '''FX8''': n/a

==Channels or X/Y switching==

* '''Axe-Fx III''' and '''FM3''' and '''FM9''': 4 channels
* '''Axe-Fx II''': X/Y
* '''AX8''': X/Y

=About amp modeling=

[[image:Amp block.PNG|500px]]

==Fractal Audio's amp modelers==

* The Axe-Fx III is the flagship product, offering the most complete feature set.
* The FM9 offers the same amp modeling as the Axe-Fx III.
* The FM3 also provides the same amp modeling, but due to its lesser processing power, some features are not available.

<blockquote>
(FM3 versus Axe-Fx III) "They are the same quality. Certain features were removed to allow the algorithms to run including the bias tremolo, input dynamics processing (...)." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-62#post-28446966]
</blockquote>

<blockquote>
(FM3) "We removed all the superfluous stuff (bias tremolo, dynamic presence/depth, etc.) in order to get the core amp modeling to run on the slower processor." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-68#post-28450968]
</blockquote>

<blockquote>
(FM3) "The Axe-Fx III contains various algorithms that allow you to enhance the amp modeling that don't exist on a real amp. I.e. dynamic presence/depth, input dynamic processing, etc. These were removed to allow the core amp modeling to run on the lower-powered processor." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-70#post-28454394]
</blockquote>

<blockquote>
"We model things that other products simply cannot as it requires more CPU power than available. The Axe-Fx III dedicates an entire 1GHz DSP to just amp modeling. And this DSP is 2-4x more powerful clock for clock than typical DSPs. We even model esoteric things like the bias excursion in the phase inverter. And that's just one thing. There's dozens of other little things like that. Many that I can't talk about because they are secrets." [https://www.thegearpage.net/board/index.php?threads/axe-fx-iii-impression-from-a-long-term-helix-user.2144811/page-9#post-30492007]
</blockquote>

<blockquote>"Some of the amp models in the Axe-Fx III use 85% of the dedicated 1GHz DSP." [https://thegearforum.com/threads/new-headrush-pedalboard-headrush-prime.1817/post-62024]</blockquote>

The same applied to the earlier hardware generations (AX8 vs Axe-Fx II).

==Amplifier and cabinet modeling for beginners==

[[Amp and Cab modeling for beginners]]

==Amp modeling developments==

The [[Firmware_release_notes_-_Axe-Fx_III|Firmware Release Notes]] describe the ongoing development of amp modeling techniques. The amp-specific bits can be found on this page: [[Amp modeling progress]].

While Fractal Audio's processors also provide state-of-the art digital effects, the amp modeling is the flagship feature. Amp modeling is part of the firmware where each generation of Fractal Audio's has a name: G3, Ares, Quantum, Cygnus, Cygnus X-2.

==The Amp models==

All current amp models are listed on the [[Amplifier models list]] page in the wiki.

[[Yeks Guide to the Fractal Audio Amp Models|Yek's Guide to the Fractal Audio Amp Models]] (PDF) provides additional in-depth information.

Most amp models are showcased in the [[Factory presets]].

Fractal Audio owns all the amps on which the models are based, except the Bludotone. [https://thegearforum.com/threads/fractal-audio-firmware-update-thread.673/page-54#post-46151]

<blockquote>"I have close to 100 amps."[https://thegearforum.com/threads/fractal-talk.2745/post-132104]</blockquote>

<blockquote>"I own almost every amp that we've modeled. I have a Dumble, Trainwreck, Ruby Rocket, multiple Carol-Anns, a Mark IIC+, a Mark IV, a Mark V, a JP2C, (2) Triaxis, about a dozen Marshalls, at least a dozen Fenders, etc., etc. I have two BE 100s: an original Purple one made when Dave was just a little shop and a newer one with all the latest changes. We have a room with a pool table. You can't use it because there are amps stacked all around it and then more in the hallway and probably another 20 or so in my office. It's kind of ridiculous." [https://thegearforum.com/threads/fractal-talk.2745/post-132395]</blockquote>

[[image:Book.jpg|link=http://wiki.fractalaudio.com/axefx2/index.php?title=Yeks_Guide_to_the_Fractal_Audio_Amp_Models |150px]]

==Number of Amp blocks==

A preset on Fractal Audio's amp modelers can have one or two Amp blocks, depending on the product.

One of the DSPs on the circuit board of Fractal Audio's amp modelers is devoted to amp modeling. Therefore, adding a second Amp block (if the firmware supports it) increases total CPU usage just a little.

'''Axe-Fx II''' and '''III''' — two Amp blocks

'''FM3''' — one Amp block. The Amp block shares a core DSP with the Delay blocks.

'''FM9''' — two Amp blocks.

'''AX8''' — one Amp block.

Some of the [[Factory presets]] on the Axe-Fx III and FM9 demonstrate the use of two Amp blocks.

<blockquote>(Axe-Fx II) "There is actually a small amount of processing for the amp blocks done on the master DSP. That, along with inter-DSP communications, uses about 2% of the master DSP." [http://forum.fractalaudio.com/threads/ver-5-more-cpu-hungry.46744/page-3#post-610285] </blockquote>

When using a single Amp block in the Axe-Fx II, the Amp block runs at double the internal sampling frequency. This happens automatically; theirs is no parameter. Main benefit of this is less aliasing in high gain models.

Fractal Audio has not officially disclosed whether the sampling frequency still depends on the number of Amp blocks in an Axe-Fx III preset. Research by a forum member indicates that this is still the case.

<blockquote>(Axe-Fx III) "The reason I haven't added a third amp block is that I would have to reduce the oversample rate for all the amp blocks when three are in use and this would be detrimental to sound quality." [http://forum.fractalaudio.com/threads/three-amp-blocks.141345/page-20#post-1757734]</blockquote>

<blockquote>(FM3) "We could potentially do two amp blocks but at reduced quality and I don't want to do that. Part of the problem with other modelers is that they don't oversample enough (and use single-precision in places where you need double-precision). Then you get complaints of artifacts and ear fatigue and all the other things associated with inadequate sample rate and word length. The vast majority of users only use one amp block so we wanted to make something with one very high quality "Ares" amp block." [https://forum.fractalaudio.com/threads/announcing-the-fm3-amp-modeler-fx-processor.149900/page-5#post-1779298]</blockquote>

<blockquote>(Axe-Fx II, firmware 3.04) "In high-res mode the internal sampling rate is doubled so as to provide greater fidelity and resistance to aliasing. This mode is automatic and is selected whenever there is only one amp block in the layout grid. Adding a second amp block will revert to normal resolution. Note that switching between presets with differing number of amp blocks may introduce an additional delay as a “soft reset” of the amp blocks must be done whenever changing the resolution."</blockquote>

<blockquote>(Axe-Fx II) "The oversampling rate is cut in half when running two amps. It's probably not noticeable. Even when running at half, it's as fast or faster than every other product available." [http://forum.fractalaudio.com/threads/use-two-amps-less-quality.57125/#post-716531] </blockquote>

<blockquote>(Axe-Fx II) "I don't hear a difference but some claim they can. A single amp block runs the amp simulation at 16x oversampling. Two amp blocks run each simulation at 8x." [http://forum.fractalaudio.com/threads/v10-test-1-amp-block-hi-res-vs-2-amp-blocks-low-res.67096/#post-826852] </blockquote>

Switching between two Amp blocks in parallel rows, is the fastest way to switch between amp sounds without a gap.

Tips:
* When using a single Amp block in a preset on a processor that supports two Amp blocks, always use the first instance (AMP 1), or you might experience a "pop" when switching to that preset.
* When switching between two Amp blocks in parallel rows, make sure to set their Bypass Mode to Mute, to prevent bleed-through of dry signal from the bypassed Amp block.
* Adding a Drive block in front of only one of two Amp blocks in parallel rows, with both Amp blocks engaged, may cause phase cancellation because of latency. Solution: add a bypassed Drive block to the other row.

When using two Amp blocks, run them in two parallel grid rows. Do not place them in series on the same row.

<blockquote>"Don't put amp blocks in series. Especially when one is clean and the other is high-gain. Always put them in parallel and set the bypass mode to Mute." [http://forum.fractalaudio.com/threads/fw10-pop-when-switching-between-two-scenes-with-a-different-amp.67340/#post-831962] </blockquote>

<blockquote>"NEVER put amps in series. Put them in parallel and set the Bypass Mode to Mute." [https://forum.fractalaudio.com/threads/loud-crash-sound-when-changing-scenes.144050/#post-1704420] </blockquote>

Note that since the introduction of firmware 20 for the Axe-Fx III, this has changed. You can now put two Amp blocks in series.

==Preamp and power amp modeling==

[[image:Amp block.PNG|450px]]

In a real amp, the preamp constitutes the amp's unique tone. The power amp amplifies the weak output signal from the preamp, powers the speaker(s) and further sculpts the amp tone when turning it up.

The virtual preamp and power amp operate the same as their hardware equivalents, but the power amp can't drive physical speakers without the help of a hardware power amp.

The Amp block consists of the virtual preamp and the virtual power amp. Parameters for both are provided.

Power Amp modeling can be disabled (globally or per-preset), but there's no way for the user to separate both sections into separate blocks. This means that you can’t switch between (virtual) power amps for a given amp model.

<blockquote>"It's not impossible but it has implementation difficulties. The main problem is that the amp block is nonlinear and therefore oversamples the data. Any effect inserted between the virtual preamp and power amp would need to also run at the oversampled rate which means many times the CPU usage. For example, if the amp block is running 8x oversampled then the CPU usage for any effect inserted would by 8x as much (I'm not going to disclose our actual oversample rate). The other way is to downsample back to native sample rate, run the effect(s), and the upsample again. No problem right? Except the no-free-lunch theory gets in the way. Downsampling and upsampling add latency." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-2-00-firmware-release.110178/page-15#post-1321907] </blockquote>

If a simulated power amp without preamp is desired, for example when using an external preamp, use the Tube Pre amp model, with its tone controls set at default, and make sure that its power amp is enabled.

<blockquote>"Yes, the Tube Pre model is neutral." [http://forum.fractalaudio.com/threads/is-it-possible-to-bypass-the-preamp.70487/#post-864821] </blockquote>

To create a preamp-only Amp model, turn off Supply Sag in the Amp block (pre-Cygnus firmware) or turn off Power Amp Modeling in the Amp block (Cygnus firmware).

The Tube Pre amp model is a preamp-only model (firmware Ares 14.00 and later).

Depending on the firmware version, the Tube Pre's power amp is on or off at default.

==Authentic or idealized modeling==

When modeling an existing amp, the choice has to be made to create an authentic model, or an idealized model:

<blockquote>"Accuracy, warts and all. Otherwise people compare against the real amp and say "it doesn't sound the same". The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]</blockquote>

<blockquote>"The frequency response is identical to the actual amps modeled. That is part of the modeling process. The models are EQ-matched to the amps and the data stored in the firmware." [http://forum.fractalaudio.com/threads/another-trick-high-pass-low-pass.116016/#post-1386469] </blockquote>

<blockquote>(Axe-Fx II) "Even without matching the modeling is so accurate now that any deviations are less than 1 dB." [http://forum.fractalaudio.com/threads/another-trick-high-pass-low-pass.116016/#post-1386514] </blockquote>

<blockquote>"Depending upon the amp the low frequency response can be highly dependent upon the load. So selecting the right Speaker Impedance Curve becomes important. Dynamic Depth is a non-physical tweak. It uses what I call "Inverse Homomorphic Processing". Anything other than zero is deviating from authentic. It's not wrong to use it but it will be less accurate. The power amp modeling IS current modeling. Power tubes are essentially current sources (with some finite resistance in parallel). Dynamic Depth has nothing to do with this. The other big thing is Master Volume. As you raise the MV the power tubes will saturate on the lows and highs first which causes the tone to have more midrange and vice-versa. Most of the controls in the Axe-Fx match their physical counterparts. The exceptions are Presence and Master Volume. Most amps simply have the wrong taper for their Presence controls. For example a 5150 Presence control does absolutely nothing from 0 to 7. All the action happens in the upper 1/4 of the control's range which is just dumb. The Axe-Fx uses a proper taper which gives a nice, even response over the full range of the control. Likewise the Master Volume on many amps is too abrupt. By 2-3 on the knob the power amp is saturating. Again we use a more rational taper so that you have finer control over power amp distortion. The downside of this approach is that if you put the Presence and Master Volume controls in the same position as the amp it won't sound the same. People do this then post videos and proclaim "See? Modeling isn't accurate!!! Toobz rule brah."" [https://forum.fractalaudio.com/threads/legacy-amp-models-consider-revisiting-full-honest-request-and-opinion.160349/post-1920107]</blockquote>

<blockquote>"All our amp models are authentic." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-14-01.165716/post-1989383]</blockquote>

<blockquote>"What I do is try to replicate a real tube amp as accurately as possible as that is the gold standard. Cygnus is demonstrably more accurate. I have the math and measurements that prove it. IMO it makes playing the amps more enjoyable. It may make recording require some more work, just like you would with a real tube amp. I don't know as I haven't tried that. For now if you don't like the changes go back to 15.01 or try some of the advanced tweaks. One of the things that Cygnus models more accurately is bias excursion and, in general, there is more bias excursion than before. You may not like the sound of bias excursion but it is part of what makes a real tube amp sound and feel the way it does. So one tweak to try is to reduce Master Bias Excursion or any of the individual bias excursion parameters. The other thing with Cyngus is the power tube bias. The previous firmware biased the virtual power tubes a bit hot in comparison to real amps. This was necessary because of the algorithm to prevent unwanted crossover distortion. The new algorithms are more accurate and, as a result, the power tube bias matches the real amps. If you want that old sound increase the Power Tube Grid Bias. Try around 0.6 to start." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2051686]</blockquote>

==Authentic or idealized controls==

[[image:amp.jpg|300px|link=]]

'''Axe-Fx III''' and '''FM3''' and '''FM9''' — if "Tone Control Display" in the [[Global Settings menu]] is set to AUTHENTIC (default), only the controls which are present on the actual amp are displayed on the main Tone page. When set to IDEAL, all tone controls are displayed.

Important: if AUTHENTIC is selected, the Bass, Mid and Treble controls are reset to their default values when changing models. This ensures accuracy for models that may not have these controls.

<blockquote>"It needs to reset all controls because not all are displayed. I.e. a Deluxe Reverb has no Mid control. For the authentic controls to work properly the Mid control needs to be set to its default position at noon." [https://forum.fractalaudio.com/threads/fm3-firmware-version-4-00-beta-5.173859/post-2107135]</blockquote>

The Amp block has one or two gain controls (Gain, Overdrive) and tone (B/M/T) controls, similar to the equivalent real amps. The range and behavior of those controls is the same as on the real amp.

"Cygnus" amp modeling:

<blockquote>"If an amp has an MV taper of greater than 15A the model's taper will be 15A otherwise it will match the amp. I.e., a Blues Jr. has an MV taper that is linear (which is ridiculous). The model's taper will therefore be 15A. There are a handful of exceptions, i.e. Camerons have linear taper MV and you need it with them because the signal level into the power amp is very low due to the Jose topology." [https://forum.fractalaudio.com/threads/mv-poll.170996/post-2059425]</blockquote>

<blockquote>"In the vast majority of models the knobs behave the same as the amp. There are a handful of models where I've taken artistic license and changed the tapers to give a more useable response. For example the Master Volume in a Blues Jr. is linear taper. This is ridiculous as it makes it very difficult to find the sweet spot. The model uses an audio taper instead which makes finding the sweet spot easier. (..) and now Cygnus firmwares have authentic behavior for most models except in a handful of cases where the manufacturer's choice of taper is dumb." [https://forum.fractalaudio.com/threads/cygnus-is-absolutely-magnificent.173225/post-2096570]</blockquote>

Before "Cygnus", the virtual Master Volume control didn't behave like the original one.

If the real amp has two gain controls, the one closest to the 1/4" input is modeled as (Input) Drive in the model. The other one is Overdrive.

If the real amp has two inputs (f.e. Low and High), the model is based on the high input. Set Input Trim to 0.500 to get the equivalent of using the low input.

If the original amp doesn't have a Bright switch but the model has, the switch corresponds to either a hardwired bright switch on the inside of the amp or it selects the amp's Bright channel (if there's not a separate model of the Bright channel).

<blockquote>(firmware Ares 6) "In general most knobs now behave exactly like the actual amp when possible. In a few instances there may be minor discrepancies between the knob position of the model and actual amp due to programming constraints and/or peculiarities of the actual amp (such as poor potentiometer tolerance). Due to variations in presence circuit topologies the taper of the Presence parameter, in particular, may vary between the model and the actual amp. In other words, a different setting on the model may be required to achieve the same response as the actual amp. In most cases however, the Drive, Treble, Mid, and Bass knobs will be accurate to within 10% of the actual amp."</blockquote>

<blockquote>"The tapers of the controls isn't really MIMIC per se. It's just me doing the dog-work and measuring the tapers. So, in that regard, the tapers match my amps. However manufacturers are notorious for changing tapers, sometimes right in the middle of a production run due to part availability. Furthermore the tapers in the Axe-Fx assume "true" logarithmic pots. Consumer-grade log pots are not true logarithmic, they're a crude approximation. At noon on a pot you'll get a nearly perfect match assuming the pot has 0% tolerance. As you deviate from noon there may be some error due to the approximation in the actual amp. As you get to the ends of the travel the error will decrease to zero. At any point there shouldn't be more than 10% or so deviation between the Axe-Fx knob position and the real amp. Master Volume tapers are NOT matched. If they were the amp volumes would jump all over the place when you switched amp types. IIRC I use a Log10A for the MV." [http://forum.fractalaudio.com/threads/axe-fx-ii-firmware-version-12-04-public-beta.80497/page-17#post-978667] </blockquote>

<blockquote>"In most cases the knobs do translate. Usually within 10%." [http://forum.fractalaudio.com/threads/axe-sounding-terrible-through-guitar-cab.58613/#post-732551] </blockquote>

<blockquote>(older firmware) "If an amp has just "Tone" then that's mapped to Treble. Leave bass and mid at noon." [http://forum.fractalaudio.com/threads/question-of-proper-axe-eq-values-for-amps-that-dont-have-them.67260/#post-828717] </blockquote>

<blockquote>(older firmware) "If the amp has no Master Volume, set the MV to 10 (the model will default to 10 when you select it). If the amp has no midrange control, set the MID to 5.00. If the amp only has a "Tone" control, set Bass and Mid to noon and the Treble control is your tone control." [http://forum.fractalaudio.com/threads/axe-tone-controls-vs-real-amps-tone-controls-question.69693/#post-855688] </blockquote>

<blockquote>(before Cygnus) "Master Volume tapers are NOT matched. If they were. the amp volumes would jump all over the place when you switched amp types. IIRC I use a Log10A for the MV." [http://forum.fractalaudio.com/threads/axe-fx-ii-firmware-version-12-04-public-beta.80497/page-17#post-978667] </blockquote>

<blockquote>(before Cygnus) "The only controls that do not necessarily match are the Presence and Master Volume. The Master Volume taper is the same for every amp. This was done to provide some consistency in finding the "sweet spot" of power amp break up and to prevent wildly fluctuating volume levels. The Presence control has a reverse log taper which gives the control a more reasonable behavior than that of most tube amps. A typical tube amp's Presence control does nothing over the first 80% of it's rotation which is stupid." [http://forum.fractalaudio.com/threads/real-vs-model-collection-thread.93693/#post-1124915] </blockquote>

<blockquote>(before Cygnus) "Presence and Depth controls may not match the taper of the actual amp. On most amps the Presence control does nothing until you turn it almost all the way up. This seems a bit silly so we make the Presence behave more logically. Same goes for the Depth control. Drive, Bass, Mid and Treble will match the actual amp within the tolerance of the pots. Another caveat when comparing amps: many times the knobs aren't "centered". IOW if you put the Treble knob at noon it isn't actually at 50%. You can see this by turning the knob all the way down and all the way up. It may not be symmetrical. This happens when the pots don't have a flat spot and/or the pot is rotated within the mounting hole." [http://forum.fractalaudio.com/threads/new-18-00-public-beta.96570/page-7#post-1158815] </blockquote>

<blockquote>(before Cygnus) "IMO accuracy is paramount and that's why we've devoted so much in resources to that end. The purpose of a modeler is to model amps as accurately as possible. Now it's impossible to account for component tolerances and tone controls can vary as much as 20% or more between two same amps. We therefore model all amps assuming the tone controls are "perfect" ((IOW if the amp was designed with a 500K pot we use 500K even if our reference amp is off by some percentage). We also don't match the Presence and MV tapers for previously discussed reasons. In some cases the Depth taper does also not match although this is infrequent. However you can be assured that even if the tapers don't match the models will match at the extremes of the control range and therefore the model is accurate but there may not be a 1-to-1 correspondence between the amp's knob and Axe-Fx's knob, i.e. Presence on 7 on the amp may be 5 on the Axe-Fx but 0 on the amp will be 0 on the Axe-Fx." [http://forum.fractalaudio.com/threads/axe-fx-vs-real-amp.107447/page-3#post-1286881] </blockquote>

<blockquote>"Internet wisdom states that no two amps of the same type sound the same. That is true, but the reasons are far more simple than many would have you believe. Tales abound of esoteric effects such as wire dress, transformer orientation, phase of the moon, etc. And while these do have some effect, it is arguably inconsequential relative to the single biggest source of deviation: tone control tolerance. I've spent the last ten years modeling tube amps and the number one thing I see is that tone controls are very inconsistent devices. First of all the tolerance of the control is typically 20%. That's plus or minus 20% so 40% total. A 100K pot can be as low as 80K or as high as 120K. This is contrast to the tolerance of a typical passive component which is 5% or less (usually much less IME). Secondly the resistance at the midpoint can vary widely. A Log10A pot should be 10% of the resistance at midpoint. But, again, this can be off 20%. Let's take the case of a bass control which is typically wired as a rheostat. On one amp the pot might be 10% high and the midpoint 10% high. Therefore with the control at noon (assuming, say, a 1M pot) the resistance will be 121K. Another amp off the assembly line might be 10% low. Therefore the pot will be 81K. That's a 40K difference between the two amps and that's not even worst-case. Now you can make the amps sound the same by simply turning down the control on one and/or turning it up on the other." [http://forum.fractalaudio.com/threads/no-two-amps-sound-the-same-fact-or-fallacy.109537/] </blockquote>

<blockquote>"You'll never get the knobs to correspond exactly. Commercial quality potentiometers are terrible. They vary widely in both end-to-end resistance and resistance at midpoint. Variations of +/- 20% are common (that's 40% total!!!). The Axe-Fx always assumes an ideal potentiometer, i.e. a pot where the end-to-end and midpoint resistances are exactly the specified value. Furthermore commercial "audio taper" pots are not truly logarithmic. They use a crude piecewise approximation. The virtual pots in the Axe-Fx are true log. This is the #1 reason for the whole "no two amps sound the same". In fact they probably do sound the same but you need to adjust the pots on one (and possibly quite a bit) to make it sound like the other. For example if a tone control is at noon (5.00) on one amp you may need to set the other amp to anywhere from 3.00 to 7.00. This applies to any product that uses potentiometers, including drive pedals. This also means when matching any virtual amp/drive/etc. in the Axe-Fx to a real-world counterpart that you may need to deviate significantly to get the same sound. For example, to get our reference Dual Rectifier's orange channel to match the model I need to set the model's treble control to around 4.0 (with the amp's treble at noon). This is because the pot in the amp has a significant deviation from the intended resistance at the midpoint. It's a 250K linear taper pot but it reads around 100K/150K when set to the midpoint. This is quite typical of commercial quality pots." [http://forum.fractalaudio.com/threads/so-about-that-new-si-diode-clipping-in-q5-xx-drive-block.120955/page-2#post-1439816] </blockquote>

<blockquote>"A typical pot used in a guitar amp has a tolerance of ±20%. On top of that there is the matching of the taper. The taper can also be off as much as 20% at the midpoint. So if we take, say, a 100K linear taper pot that's perfect it will have a resistance of 50K at the midpoint. We assume perfect pots in the models. However an actual amp may have a pot that's low by 20% so that would be 80K. If the taper is perfect then it's only 40K at the midpoint (20% error). If the taper is off then it might only be 32K at the midpoint for a total error of 36% (!!!). To get the same response on the model you would need to set that control to 3.6 instead of 5.0. That's an absolute worst case and I've never seen that but I routinely see pots that are 20% off at the midpoint." [http://forum.fractalaudio.com/threads/dual-recto-with-the-lb-2-vs-the-axe-fx-iii-and-more.143501/#post-1699121]</blockquote>

<blockquote>"I routinely see more than 20%. Full-scale resistance is often off by up to 20%. Mid-scale resistance is then off by another 10-20%. For example a 1M linear pot might be 800K and then off another 40K at mid-scale for a total error of 28%." [https://forum.fractalaudio.com/threads/legacy-amp-models-consider-revisiting-full-honest-request-and-opinion.160349/post-1919890]</blockquote>

<blockquote>(before Cygnus) "Most of the controls in the Axe-Fx match their physical counterparts. The exceptions are Presence and Master Volume. Most amps simply have the wrong taper for their Presence controls. For example a 5150 Presence control does absolutely nothing from 0 to 7. All the action happens in the upper 1/4 of the control's range which is just dumb. The Axe-Fx uses a proper taper which gives a nice, even response over the full range of the control. Likewise the Master Volume on many amps is too abrupt. By 2-3 on the knob the power amp is saturating. Again we use a more rational taper so that you have finer control over power amp distortion. The downside of this approach is that if you put the Presence and Master Volume controls in the same position as the amp it won't sound the same. People do this then post videos and proclaim "See? Modeling isn't accurate!!! Toobz rule brah."" [https://forum.fractalaudio.com/threads/legacy-amp-models-consider-revisiting-full-honest-request-and-opinion.160349/post-1920107]</blockquote>

<blockquote>"If a knob isn't present in the Authentic menu then it may not do anything in the Ideal menu."</blockquote>

<blockquote>"If a parameter doesn't exist in the Authentic controls there is no guarantee that the parameter in the Ideal controls will be functional." [https://forum.fractalaudio.com/threads/hi-cut-control-on-citrus-rv50-not-working.178740/post-2178756] </blockquote>

<blockquote>"The sensitivity to pot value is very high. Consumer potentiometers have a 20% tolerance on end-to-end resistance and another 20% on midscale resistance. If the taper of the pot is Log10A and the pot is a nominal 1M then the midscale resistance should be 100K. If the pot is 20% low on end-to-end resistance (800K) and then another 20% low on midscale resistance then it's value at midscale would be only 64K. That's nearly half the nominal value. The potentiometer values used in the models use "nominal" values. If the amp was designed with 1M pots then we use 1M for the pot value. When comparing the models to the amps I routinely have to change the B/M/T controls +/-20% to get the model to match the amp. And this is expected. For example on my 5150 I have to set the model's bass control to 4 to match the amp at 5 (-20%). This is unsurprising since when we measured the pot in the amp it was about 20% low at mid-scale." [https://forum.fractalaudio.com/threads/buttons-functioning-as-on-amps.170531/post-2052812]</blockquote>

<blockquote>"Most of the tweaks in an Axe-Fx / FM3 are circuit tweaks so it would be equivalent to modding your amp. In the case of a Vibrolux the amp has a fixed midrange resistor in the tone stack. In the Authentic menu the midrange control is not there and the resistor value is fixed. When using the ideal page the midrange resistor is adjustable. This would be equivalent to modding your amp by adding a midrange pot." [https://www.thegearpage.net/board/index.php?threads/fractal-question.2267220/post-32792621]</blockquote>

Also read this: [https://forum.fractalaudio.com/threads/why-your-amp-doesnt-sound-like-our-amp.172907/#post-2090367 Why Your Amp Doesn't Sound Like Our Amp]

<blockquote>"A potentiometer has tolerances, two of them. The first is the end-to-end resistance. If a pot is rated at 1Mohm, 20% then it's end-to-end resistance can be anywhere from 800K to 1.2M. The second is midpoint resistance. That same pot might be a linear pot which implies the midpoint resistance is 50% of the end-to-end resistance. Again, there is a tolerance on this value, typically about 10%. Now, an ideal 1M, linear potentiometer will have a midpoint resistance of 500K. But a given amp may end up with a pot that is 20% low in end-to-end resistance and ALSO 10% low on midpoint resistance. So that pot is now 1/2 of 800K (400K) minus 10% which yields 360K. That particular amp will sound different than one that has a pot with tighter tolerances. It's is therefore impossible for one amp to sound exactly the same as another copy of the same amp and, by extension, a model of the amp to sound exactly like a particular copy of the amp. [https://www.thegearpage.net/board/index.php?threads/what-dont-you-like-about-fractals-modeling.2326185/post-34061838]</blockquote>

<blockquote>"If you take two copies of a particular amp and put all the knobs at 7, they won't sound the same. Likewise the model with all knobs at 7 won't sound the same either. However, the amps and the model will sound similar, very similar in most cases. We always assume the potentiometers in our models are ideal and have 0% tolerance both end-to-end and midpoint. Another way of saying this is if you put a knob on the real amp at 7, our model with the knob on 7 will be as close as another random copy of that amp with its knob on 7 will be." [https://www.thegearpage.net/board/index.php?threads/what-dont-you-like-about-fractals-modeling.2326185/post-34061891]</blockquote>

<blockquote>"The tolerance of potentiometers is terrible. You cannot set the knobs exactly the same as a given amp and expect things to match perfectly. For example, with BMT at noon on our reference 5150 I have to set the model's bass control to around 4.5 and the treble to nearly 6 to match. This is because the bass and treble pots are not perfect in the real amp. Do a search on potentiometer tolerance. End-to-end and center. You'll be amazed at just how poor consumer grade "quasi-log" pots are. Our models assume the pots are "perfect" and exhibit the exact resistance as specified. I.e. if it's a 1M 10A pot then it will be exactly 100K with the wiper at mid rotation. In a real amp the end-to-end resistance is +/- 20% and the midpoint can be off another 20%. Do the math and you'll see why no two amps sound the same at the same knob settings and why the model will not necessarily match a particular amp at the same knob settings. I assure you that our model is accurate. You may have to adjust the controls up or down as much as 20% to match a given amp. That's the nature of tolerance. Listening to the clip I would say turn the bass up to 7 or more, turn the treble and mid down a bit." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-00-release-candidate-2-beta-8.188778/post-2342264]</blockquote>

<blockquote>"There are many different types of "Log pots". Logarithmic potentiometers (more correctly known as audio taper pots) have "tapers". There are 5A, 10A, 20A, 25A, and 30A as well as reverse versions. The most commonly used tapers in guitar amps are 10A and 30A. The taper indicates the percentage of maximum resistance when the pot is halfway. I.e., a 1M 10A pot will be 100K at noon. A pot labeled as 1MA doesn't indicate the taper and Mesa, in particular, doesn't like to divulge the tapers they're using. When I compared our reference Mark IV to our reference Mark V the tapers of the controls were different." [https://forum.fractalaudio.com/threads/question-about-the-mark-series-graphic-eq-modeling.149223/post-2476619]</blockquote>

<blockquote>"In most cases the tapers are the same as the real amp. In a handful of cases they are not. This cannot change at this point since it would change existing presets." [https://forum.fractalaudio.com/threads/presence-taper-that-matches-the-real-amp.187775/post-2483234]</blockquote>

<blockquote>(firmware 23.05) "The only remaining non-authentic controls are the Mesa Mark EQ sliders I believe." [https://forum.fractalaudio.com/threads/5150-presence-knob.199908/page-14#post-2493552]</blockquote>

[[image:tapers.png|300px]]

The range of the Drive taper in the Axe-Fx is 0-10. Volume knobs on Fender amps go from 1 to 10. This translates to:

:Fender 1 = Axe 0.00 
:Fender 2 = Axe 1.11 
:Fender 3 = Axe 2.22 
:Fender 4 = Axe 3.33 
:Fender 5 = Axe 4.44 
:Fender 6 = Axe 5.55 
:Fender 7 = Axe 6.66 
:Fender 8 = Axe 7.78 
:Fender 9 = Axe 8.89 
:Fender 10 = Axe 10.00

<blockquote>"For a Fender the controls go 1-10. On the model they go 0 - 10. To replicate the amp's controls multiply by 1.1 and subtract 1.1. I had the amp set to 6, 6, 6 and set the model to 6, 6, 6 and there was too much bass and gain. But the correct value is 5.5, 5.5, 5.5." [http://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-00-beta.148607/page-15#post-1760226]</blockquote>

[http://forum.fractalaudio.com/threads/conversion-chart-for-real-amp-settings-vs-fas.106182 Conversion chart for amp controls which go to 10 or 11]

==Why your amp doesn't sound like Fractal Audio's==

Fractal Audio explains:

<blockquote>"The models in our products are based on our in-house reference amps. If a model doesn't sound like your version of that amp it won't sound like our reference amp either.

Why?

Component accuracy and drift. 
The components used in tube amps are low-cost, consumer-grade parts. They typically have tolerances of 10% or more. Over time the value of these components drifts. If your amp is old chances are it doesn't sound like it did when it was new. All our old reference amps are given a thorough checkup prior to modeling with any out-of-tolerance parts replaced.

Potentiometer tolerance. 
A typical consumer potentiometer has a tolerance of up to +/- 20%. That's huge and that's end-to-end accuracy. On top of that the midpoint accuracy can be another +/- 20%. So if you have a 1M pot it could be as low as 800K. If it's linear it's midpoint should be 400K but could be as low as 360K. Now your 1M pot that should be 500K at halfway is only 360K. That's an error of 28%!

Potentiometer taper. 
A big one. Potentiometers come in a variety of tapers: linear, 30A, 20A, 10A, etc. The taper on an audio taper pot (i.e. 30A) denotes the value of the pot at mid rotation. For example a 1M, 10A pot would be 10% of its value at "noon", or 100K. Manufacturers are constantly changing the taper of the pots in their amps. Sometimes the designer changes the taper as customers are reticent to turn knobs much away from noon. It's a weird psychological thing. Sometimes the manufacturer changes the taper due to availability concerns. Sometimes they change the taper when moving manufacturing locations. Sometimes they change the taper for no apparent reason at all. Another factor is that almost all amps don't use true log taper pots. They use "commercial log" taper which is a crude approximation to a log taper. This is because true log taper pots are expensive. Fractal Audio products use true log taper. This means that '7' on your amp is not exactly '7' on the model even if the pot in your amp is exactly 1M and its taper is exactly 10A. Why do we do it this way? Because the response is smoother and if true log pots were the same price as consumer log pots everyone would use true log taper. We model all amps assuming the pots are ideal. We assume the end-to-end resistance is exactly, say, 1M and the midpoint is, say, exactly 100K. We DO NOT use the values measured in our reference amp because no two amps are the same so we use the DESIGNERS INTENDED VALUE. What all this means is '3' on your amp is not necessarily the same as '3' on the Axe-Fx. Example: the Master Volume pot in a 5150 is a 1M, 15A audio taper pot. Theoretically it should be 150K at noon. On our reference amp it's about 15% low. If the reference amp's MV is set to '3' we have to set the model to around '2.5' to match. This is unsurprising due to the tolerance of the reference amp's pot.

Indicator accuracy. 
On many amps if you set a knob to noon it's not actually halfway in the pot's rotation. Why? Several reasons. Some amps are just weird. For example the Bogner Shiva's minimum rotation is around 6:00 and the maximum is around 4:00. So noon is actually past midpoint. Same with Soldanos. In other cases the knobs aren't oriented perfectly on the shaft. If it's a knurled shaft the knob may be off one tooth. If it's a smooth shaft then you're at the mercy of the human who put the knob on the shaft and tightened the set screw. This is why I prefer D-shafts. Finally the pot itself may be rotated relative to the panel. You can try this yourself. Turn the knob on your amp fully CCW. Note the position of the indicator. Now rotate fully CW. Note the marker position. If it's an old amp it's probably not symmetrical. Then there's the whole marking thing. Fender's are numbered 1-10. Soldanos go to 11. We use 0-10 so be wary of the amp's numbering.

Power Tube Bias. 
Another big one. The transconductance (gain) of a power tube can vary greatly. This is why power tubes are color coded, sold in matched sets, etc. Amps come in two flavors: fixed bias and cathode bias. Fixed bias amps apply a "fixed" voltage to the grid of the power tubes. Cathode bias amps use a resistor between the cathode and ground to self bias the tube. Most, but not all, fixed bias amps allow the user to adjust the bias point of the amp. This allows the bias point to be set to an optimum value for the particular set of tubes installed (since the transconductance can vary greatly). Some fixed bias amps do not allow adjustment. Examples are Mesa/Boogies, 5150s, and several other brands/types. The drawback of this is that the bias can vary greatly depending upon the gain of the tubes installed. Due to this the manufacturers err on the safe side and the bias is usually much colder than the ideal value. Most cathode biased amps are not adjustable. Again you are at the mercy of the tube's gain but these amps tend to be biased hot to begin with and have higher transformer matching which prevents excursion outside of the S.O.A. (safe operating area). If the bias is adjustable where the manufacturer decides to bias their tubes is a matter of preference. Most manufacturers bias their tubes on the cold side to prevent premature failure and reduce warranty claims. Especially the larger manufacturers. This leads to the question of "what is the ideal bias point?" The pervasive school of thought is you adjust the bias so the idle dissipation is 60-70% of the tube's peak power rating. This is a safe approach and ensures that the tubes don't "red plate" and live fairly long and prosperous lives. My opinion is that the ideal bias point is NOT a function of the tube's power rating. It's the point at which the power amp's transfer function is most linear. Unfortunately operating the tubes at that point can result in exceeding the tube's S.O.A. So the optimum bias point depends on the tube's power rating, the transformer primary impedance (matching) and the user's tolerance to tube replacement frequency. For example, if we bias an EL34 based power amp at 60% peak dissipation it's actually running fairly cold. If we know that the transformer is slightly overmatched we can bias the tubes hotter, 70% or even more. This will result in a warmer tone but the tubes will wear faster. What does all this mean? Well, I bias the virtual tubes on the warm side. EL34s are biased at around 70% because we don't have to worry about them wearing out. 6L6s are biased a little colder, around 60% but this is actually as "warm" as the EL34s because of the higher plate dissipation of a 6L6. In practice this means that the models in the Axe-Fx will biased warmer than a new amp straight out of the box as most amps are biased cold (too cold IMO). After you wear the tubes out and bring it to a tech the tech will replace those tubes and bias them hotter than factory. So if you're comparing your new, out-of-the box 5150 with the Axe-Fx model the amp will probably sound "colder". Some people like this, many do not. If you like a colder sounding power amp it's just a knob twist away." [https://forum.fractalaudio.com/threads/why-your-amp-doesnt-sound-like-our-amp.172907/post-2090367]</blockquote>

and:

<blockquote>"A potentiometer has tolerances, two of them. The first is the end-to-end resistance. If a pot is rated at 1Mohm, 20% then it's end-to-end resistance can be anywhere from 800K to 1.2M. The second is midpoint resistance. That same pot might be a linear pot which implies the midpoint resistance is 50% of the end-to-end resistance. Again, there is a tolerance on this value, typically about 10%. Now, an ideal 1M, linear potentiometer will have a midpoint resistance of 500K. But a given amp may end up with a pot that is 20% low in end-to-end resistance and ALSO 10% low on midpoint resistance. So that pot is now 1/2 of 800K (400K) minus 10% which yields 360K. That particular amp will sound different than one that has a pot with tighter tolerances. It's is therefore impossible for one amp to sound exactly the same as another copy of the same amp and, by extension, a model of the amp to sound exactly like a particular copy of the amp. [https://www.thegearpage.net/board/index.php?threads/what-dont-you-like-about-fractals-modeling.2326185/post-34061838]</blockquote>

and:

<blockquote>"If you take two copies of a particular amp and put all the knobs at 7, they won't sound the same. Likewise the model with all knobs at 7 won't sound the same either. However, the amps and the model will sound similar, very similar in most cases. We always assume the potentiometers in our models are ideal and have 0% tolerance both end-to-end and midpoint. Another way of saying this is if you put a knob on the real amp at 7, our model with the knob on 7 will be as close as another random copy of that amp with its knob on 7 will be." [https://www.thegearpage.net/board/index.php?threads/what-dont-you-like-about-fractals-modeling.2326185/post-34061891]</blockquote>

and:

<blockquote>
"The tolerance of potentiometers is terrible. You cannot set the knobs exactly the same as a given amp and expect things to match perfectly. For example, with BMT at noon on our reference 5150 I have to set the model's bass control to around 4.5 and the treble to nearly 6 to match. This is because the bass and treble pots are not perfect in the real amp. Do a search on potentiometer tolerance. End-to-end and center. You'll be amazed at just how poor consumer grade "quasi-log" pots are. Our models assume the pots are "perfect" and exhibit the exact resistance as specified. I.e. if it's a 1M 10A pot then it will be exactly 100K with the wiper at mid rotation. In a real amp the end-to-end resistance is +/- 20% and the midpoint can be off another 20%. Do the math and you'll see why no two amps sound the same at the same knob settings and why the model will not necessarily match a particular amp at the same knob settings. I assure you that our model is accurate. You may have to adjust the controls up or down as much as 20% to match a given amp. That's the nature of tolerance. Listening to the clip I would say turn the bass up to 7 or more, turn the treble and mid down a bit." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-00-release-candidate-2-beta-8.188778/post-2342264]</blockquote>

==Polarity==

<blockquote>
"All amp models have the same polarity so that you can mix them without weirdness." [http://forum.fractalaudio.com/threads/axr-fx-ii-xl-noise-over-palm-mute.119930/page-2#post-1444307]
</blockquote>

==Input impedance==

<blockquote>
"Tube amp models are always 1M (no capacitor)." [https://www.thegearpage.net/board/index.php?threads/fractal-fm3-fuzz-w-fixed-impedance.2214483/post-31728537]
</blockquote>

==Settings for FRFR or guitar speaker==

[https://forum.fractalaudio.com/threads/table-amp-settings-depending-on-power-amp-and-speaker.185259 Click here for the recommended Amp and Cab settings for each type of amplification]

==When using a tube power amp (and traditional cab)==

===Power amp modeling===

When using a [[Connections and levels|tube power amp for amplification]], it makes sense to disable Power Amp modeling. Of course, YMMV.

However, some tube amps, such as Fryette's Power Station and LX-II, are designed to have a neutral impact on the sound and allow Power Amp modeling to be enabled.

To turn off Power Amp modeling:

* Pre-Cygnus amp modeling: '''Turn off Supply Sag in the Amp block (display shows: "p.a. off")'''

* Cygnus amp modeling: '''Turn off Power Amp Modeling in the Amp block'''

and/or

* '''Disable Power Amp Modeling in the Global Settings menu'''

The result of switching it off in the amp model versus adjusting the global parameter is not exactly the same:

<blockquote>"If you shut the power amp modeling off from the Global menu, it is not exactly the same as turning it off (in the Amp block). This is because the virtual power amp always runs. So if you shut the power amp modeling off from the Global menu, the supply will still sag resulting in a more compressed response. If the Master is set high the sag can be quite pronounced." [http://forum.fractalaudio.com/threads/power-amp-sim-on-off-vs-sag-on-off-with-real-power-amp-behaviour-of-presence-control.121178/#post-1442553] </blockquote>

Turning off Power Amp modeling is not the same as bypassing the Amp block. If Power Amp modeling is disabled, preamp modeling will still run.

If Power Amp modeling is disabled, Depth and Presence are disabled (Quantum 9.03 and later), and Master Volume changes into a simple volume control. (Before Quantum 9.03, Presence turned into a shelving filter when power amp modeling was disabled.)

===Speaker-related parameters===

[[image:h_cabs.png|link=]]

When using an [[Connections_and_levels#Power_amp_and_guitar_speaker|external power amp and a traditional guitar speaker cabinet]] to amplify the modeler, make sure that [[Amp_block#SPEAKER_DRIVE|Speaker Drive]] is disabled in the Amp block. This parameter should be used only with virtual cabinet models.

Cabinet modeling should be disabled altogether when using a traditional guitar speaker cabinet, either by bypassing the Cab block in the preset, or by turning off Cabinet Modeling in the [[Global Settings menu]]. When using a speaker that's been designed for FRFR, do NOT turn off Cab Modeling.

When using a non-neutral tube power amp, turn off Power Amp Modeling (see above), [[Amp_block#SPEAKER_COMPRESSION|Speaker Compression]], [[Amp_block#SPEAKER_COMPLIANCE|Speaker Compliance]] and [[Amp_block#CABINET_RESONANCE|Cabinet Resonance]]. When using a solid-state power amp, you don't have to turn off these controls.

<blockquote>"If using a solid-state amp into a traditional cab I would recommend Speaker Compression and Compliance not be zero. If using a tube power amp into a traditional cab all should be zero." [http://forum.fractalaudio.com/threads/axe-fx-iii-firmware-2-00-public-beta-2.144615/page-2#post-1710669]</blockquote>

Low Freq and High Freq Resonance are pre-set frequencies at which the virtual amp resonates with the cab model. The values depend on the selected [[Amp_block#SPEAKER_IMPEDANCE_CURVE|Speaker Impedance Curve]] on the Speaker page of the Amp block (firmware Ares 11 and later). When using a real cabinet, you'll want to replace this with the "real" resonant frequency of the cabinet, if you know it.

Firmware 22 and later for the Axe-Fx III enables automatic adjustment of the Speaker Impedance Curve in the Amp block to the selection of a "DynaCab" in the Cab block:

<blockquote>"The Amp block now features “Auto Dyna-Cab Impedance”. When set to ON the speaker impedance curve of the Amp block will follow the Cabinet Type in the first mixer slot of the associated Cabinet block. I.e., if the Cab Type in the first mixer slot of Cabinet 1 is, say, 4x12 5153 and the Mode is Dyna- Cab then Amp 1’s speaker impedance will automatically be set to 4x12 5153." </blockquote>

Also take a look at the [[Amp_block#OUTPUT_MODE|Output Mode]] setting in the Amp block.

==Tweaking an amp==

First, load the correct default parameters for the selected amp type, by resetting the Amp block.

The Band-Commander (clean tone) and Friedman BE (dirty tone) amp types at default settings provide useful baseline tones and may be useful as reference when tweaking.

Be aware that the choice of a cab (IR) in the Cab block often has much more impact on the tone than tweaking controls in the Amp block.

<blockquote>"One of the things I've found really useful about these (far-field IRs) is they are a good starting point for dialing the amp block in. Near-field IRs can have excessive bass and/or treble. To compensate we might end up doing strange things in the amp block which throws off the distortion character and feel. When using a far-field IR it's very similar to how the amp sounds through a conventional cab. So what I'm doing is using one of the far-field IRs to start, dial in the amp block and then choose a near-field IR. I then adjust the low/high cuts in the cab block rather than adjusting the amp block." [https://forum.fractalaudio.com/threads/free-far-field-session-2-cab-pack-for-axe-fx-users.151232/post-1801544]</blockquote>

==Switching between amps==

Here are the most common methods to switch between amp models:

* Use different Presets.
* Switch between two Amp blocks in a preset via MIDI.
* Switch between two Amp blocks in a preset via Scenes.
* Switch between two Amp blocks with the Multiplexer block.
* Crossfade between two Amp blocks with the Mixer block.
* Use X/Y switching in a single Amp block.
* Use Channels with a single Amp block.
* Use Scenes and a Scene Controller with a single Amp block.

The time to switch scenes and presets depends on the device, available CPU and effect settings (bypassed or not, X/Y states and channels).

X/Y switching and switching Channels causes a short gap in the sound. The gap is caused by the necessity to briefly mute and unmute the sound. The gap doesn't occur in firmware 23 and later for the Axe-Fx III.

<blockquote>(AX8) "Our modeling is very detailed and whenever the amp model changes the "virtual circuit" needs to be reconfigured. We can switch quickly but often this causes clicks and pops due to the reconfiguration. So the amp block needs to run silently for a bit so things will settle. Then we unmute the block. This mute period is what you are hearing. Most other products just use a fixed algorithm and change the input/output EQ and gain. With this type of algorithm you can switch quickly without clicks and pops but, of course, you don't get the realism and detail." [http://forum.fractalaudio.com/threads/does-the-ax8-have-an-audio-gap.118736/page-2#post-1413280] </blockquote>

To avoid this, switch between two Amp blocks if the hardware allows it, or use Scene controllers to change amp settings instead of X/Y switching or Channels, or use [http://forum.fractalaudio.com/threads/various-presets-tricks.135770/#post-1625421 Bakerman's compression trick].

[https://www.youtube.com/watch?v=q-4bpljNxvA&t=50s Cooper Carter: Gapless Amp Switching on the Axe-Fx III]

[https://www.youtube.com/watch?v=9ncGcU0QS2A&t=61s Cooper Carter: Live Two Amp Blending]

Switching channels on the Axe-Fx III is very fast (and has disappeared in firmware 23 and later).

<blockquote>(Axe-Fx III) "The "gap" is arbitrary and is simply the time to fade down the old amp and fade up the new amp. You HAVE to do some ramp-down and ramp-up or you'll get artifacts as the gain can be completely different. If you just instantly switch from a clean amp to a distorted amp or vice-versa you'll get a pop. That's just basic signal processing." [http://forum.fractalaudio.com/threads/presenting-the-axe-fx-iii.134717/page-26#post-1593840] </blockquote>

<blockquote>(Axe-Fx III) "Feels seamless to me (and faster than any of my channel switching amps) but everyone has different definitions." [http://forum.fractalaudio.com/threads/presenting-the-axe-fx-iii.134717/page-27#post-1593846] </blockquote>

<blockquote>(Axe-Fx III) "Any faster than that and you risk pops or clicks if the levels and/or gains are markedly different. You can't change the laws of nature." [http://forum.fractalaudio.com/threads/presenting-the-axe-fx-iii.134717/page-31#post-1594370] </blockquote>

<blockquote>"On the III it mutes just the block so the reverb and delay are unaffected." [http://forum.fractalaudio.com/threads/axefx-iii-whats-missing.134747/page-5#post-1594439] </blockquote>

<blockquote>"The Axe-Fx switches amp channels very fast, 19 ms. This is comparable to a typical tube amp." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-22-00-public-beta-5-beta-11.194550/post-2423513]</blockquote>

Firmware 23 for the Axe-Fx:
<blockquote>"Preset, Scene and Channel changes are now gapless."</blockquote>

[https://forum.fractalaudio.com/threads/get-rid-of-switching-audio-gaps-p1-6-technical-measurements-and-info.195653/ More about audio gaps]

==Quick access to controls==

'''Axe-Fx III''' and '''FM9''' — Assign controls to the Performance Pages (when assigned). Or, from the Home screen, push Page Right and the AMP 1 or AMP 2 button.

'''FM3''' — Assign controls to the Performance Pages (when assigned). Or, from the Home screen, push Page Right and the AMP button.

'''Axe-Fx II''' — Assign a Quick-Jump button (X/Y) to the Amp block in the I/O menu.

==Cut, Bright, Fat and Boost switches==

All amp models have these switches, even if the original "real" amplifier doesn't have them. They can be set per scene or by pushing a button by assigning a controller. This can be an external controller or a Control Switch. [https://www.youtube.com/watch?v=kXvVf-vV8bI Here's a demo].

==Midrange smoothness==

Fractal Audio:

<blockquote>"The "midrange smoothness" is actually adjustable in our modeling but it's hidden from the user. A real tube power amp clips hardest in the low midrange frequencies because this is where the trough in the speaker impedance is located.

At those frequencies (if the transformer is slightly undermatched, as is often the case) the grids clip before the plates. Grid clipping is very hard, almost a hard limiter. Plate clipping is much softer. We model all this but the grid clipping "shape" is hidden from the user and varies by model.

Many modeling algorithms, however, treat everything with a single nonlinearity and ignore grid clipping. This makes the midrange clipping softer and leads to a "sameness" across the spectrum.

The clipping in a tube power amp can be divided into three categories:
Grid clipping. This occurs in the low midrange and is a harder distortion.
Plate clipping. The plates clip at the speaker low frequency resonance and in the upper midrange frequencies and beyond. Plate clipping is softer.
Transformer distortion. Transformer distortion is a complex distortion that increases with the inverse of frequency. It is sort of soft and farty.

Then there is crossover distortion which is not clipping but another form of nonlinearity.

The more nonlinearities you model, the more complicated the algorithm and the more CPU power required.

Then you get preamp distortion which is a whole 'nother can of worms." [https://www.thegearpage.net/board/index.php?threads/shootout-with-clips.2300109/post-33478318]</blockquote>

==Reset the amp==

===About the Amp block===

Amplifier models (aka “amp types”) are available through the AMP block. Here you select the type that you want. An amp model presents itself in the AMP block through its typical name, and its specific settings.

Some of these specific settings are displayed in the AMP block. Some of them are hidden from the user. They are (probably) part of a table which gets interpreted by the firmware upon loading an amp model, together with the appropriate amp modeling algorithm. All parameters are discussed in the owner’s manual and here in the wiki.

Disclaimer: the description above is a very simplified version of what's happening in the AMP block.

===Why would you want to reset an amp===

Resetting an amp means that settings in the AMP block are returned to their correct default values for the currently selected amp model.

====Because YOU changed things====

You can adjust settings in the AMP block. Not only basic stuff like volume, gain and tone, but also many parameters that go much deeper. You can extensively tweak the sound and feel of the amp model to your liking. This is a unique feature of Fractal Audio’s amp modelers.

If you tweak the more advanced settings, you deviate from the default parameter values specific to that amp model. By resetting an amp you make sure that the correct default settings for that amp model (hidden and visible) are put back in place.

====Because FRACTAL AUDIO changed things====

Fractal Audio continually improves its technology through firmware updates. These firmware updates include improvements to the underlying algorithms and to specific amp model settings, based on those algorithms. This poses a challenge for handling existing presets.

Changes to the core amp modeling algorithms are always applied, so the sound may change. There’s no way around this, meaning that there’s no support for older versions of core algorithms. If you want to stick to older algorithms, do not update the firmware.

Specific AMP block settings, whether visible or hidden, are sometimes updated to new default values automatically when updating firmware that includes amp modeling improvements. And sometimes they are not (not automatically), because some users want to keep existing values. The firmware comes with release notes that inform you about this. In general, there’s NO NEED to reset an amp after updating firmware, unless the release notes say so.

Resetting an amp makes sure that the correct default settings for that amp model (hidden and visible) are put back in place. For example, to get a clean start, or to compare settings and sound.

'''''Disclaimer:''''' ''The description above is a very simplified version of what's happening in the AMP block.''

===What happens when you reset an amp===

To accommodate users, Fractal Audio provides several methods to reset the amp, each with a different outcome.

The reset methods for the AMP block are:
# soft reset
# hard reset
# reset in the editor’s Manage Presets tool

These methods are explained below.

===SOFT reset (re-select)===

A “soft reset” means that you select another amp type in the AMP block and then re-select the previous amp type again. Or just select the current amp type again in the editor. This is referred to as a "soft reset".

When doing this, the amp model will be loaded again with most of its parameters returned to their default specific settings. It applies to the current amp channel only. The preset needs to be saved afterwards.

Whether the basic tone controls are left untouched OR also return to default when performing a soft reset, depends on the value of TONE CONTROL DISPLAY in the [[Global Settings menu]]:
* when set to AUTHENTIC: a soft reset will also return Bass / Middle/ Treble to their default values
* when set to IDEAL: a soft reset will not change the existing Bass / Middle / Treble settings.

The list below describes what happens when performing a soft reset, page by page (last checked in February 2021):

* Authentic / Ideal page — everything default, except: Bass/Mid/Treble (unless TONE CONTROL DISPLAY is set to AUTHENTIC), Gain, Overdrive, Input Select, Mute, Level, Balance.
* Preamp — everything default, except: Boost Type and Boost Level.
* Power Amp — everything default.
* Power Supply — everything default, except: Tremolo Frequency.
* Speaker — everything default.
* Speaker Drive — everything default, except: Speaker Compression, Speaker Time Const, Output Mode.
* Input EQ — everything default, except: Input Type and Q.
* Output EQ — everything default, except: EQ On/Off.
* Dynamics — everything default, except: Master Bias Excursion, Out Comp Type.

A soft reset guarantees that your AMP block settings are in line with the latest modeling defaults, while preserving your basic gain and tone settings (depending on the TONE CONTROL DISPLAY setting).

===HARD reset===

If you want each and every parameter of the amp model to be returned to its default value, without exceptions, you need to fully reset the model, on the hardware or in the editor. This is referred to as a "hard reset" or "full reset". It applies to the current amp channel only. The preset needs to be saved afterwards. A hard reset lets you start 100% fresh, a good way building a new preset.

On the hardware, select the AMP block, press EDIT, press RESET (soft knob A). This resets the current channel only.

In the software editor:
* select the AMP block, select the Block menu at the top of the editor and select Reset Channel, or
* right-click the AMP block (the context menu appears), click Edit and select Reset Channel, or
* select the AMP block, and press CTRL-I (Windows) or Command-I (Mac).

Note: removing and adding an AMP block on the grid is NOT the same as a hard reset.

===Reset in the editor’s Manage Preset tool===

This method has been made available in the latest version of the editors.

In Manage Presets, select one (or more!) presets, and use the context menu (right-click) to select "Reset AMP block".

This will reset ALL channels of the AMP block in the selected preset(s), while maintaining the settings on the Authentic page of the AMP block, and automatically saves the preset(s) too.

So why this option if a soft reset kinda accomplishes the same thing? Well, this method makes batch processing possible: resetting all channels of all AMP blocks in a bunch of presets through a single command.

However, be aware that this method will reset the following AMP block settings:
* graphic EQ
* speaker impedance curve

===Is “Refresh After New FW” the same as a reset===

The software editors provide a menu option "Refresh After New FW". This is NOT a reset command! It syncs the software with the hardware.

The Refresh command is executed by the editor by itself after updating updating the device with officially released firmware.
When testing BETA versions of firmware, the Refresh command may need to be executed manually to force the editor to sync with the hardware.

===Can you reset a single parameter to its intended default value===

No. A reset always resets the entire channel of the block.

You may think that double-clicking a control in the software editor resets it to its default value but that’s not the case: that value is just a generic default value, not necessarily the correct value for the specific parameter and amp type.

Ideally double-clicking should reset it to the correct value, but this is a limitation of the architecture at this time. [https://forum.fractalaudio.com/threads/fm3-firmware-version-3-01.168482/post-2024066]

==Preserve your amp tones==

So you have dialed in a perfect-sounding amp by tweaking some advanced parameters. And here comes a firmware update you absolutely don't want to skip. But you don't want to lose your carefully dialed-in sound.

Your current presets and amp settings are always connected to the currently loaded firmware version. If you upgrade the firmware and the firmware includes changes to the amp modeling, your sound may change.

Reapplying "old" amp block settings often is not the best choice. New defaults have been implemented for a reason, and may also be linked to changes in algorithms in the firmware. Using the same tweaked values may not result in the same sound.

Here are the methods you can use to backup your stuff, or re-use it:

* '''Fractal-Bot''' — save and load entire banks of presets, and firmware
* '''Software editor''' — export (save on disk) a single preset, and load a single preset (including ones from a bank), or make a "snapshot"
* '''Recall Effect''' (if available on your device) — load the values of an AMP block from one preset into another (not on Axe-Fx III)
* '''Global blocks''' (if available on your device) — save Amp block settings to different instances of a global block

==Amp gain==

There are many ways to increase or decrease amp gain.

IMPORTANT: adjusting Input Level or Input Pad in the I/O menu does not affect amp gain!

*'''Your guitar's output'''
* '''Global amp gain''' — adjust the global Amp Gain parameter in the system settings (Axe-Fx II and AX8 only). This parameter lets you adjust the range of gain of the amps in all presets. This is also possible per preset via the Input Trim parameter in the Amp block.

<blockquote>(Axe-Fx II) "The global Amp Gain is for people who use different guitars and want the input gain to be the same even though the guitars have different outputs. The unity gain feature in the II doesn't allow for this. It makes sure the signal your guitar puts out is what the input to the grid sees while still making sure the A/D converters get a good signal." [http://forum.fractalaudio.com/threads/incoming-incoming-incoming.39841/page-5#post-540320]</blockquote>

<blockquote>(Axe-Fx II) "They (Amp Gain and Input Trim) are basically the same thing. The global Amp Gain has a smaller range as it's designed for fine-tuning between guitars whereas the local trim allows you to radically alter the response of the model." [http://forum.fractalaudio.com/threads/input-trim-global-amp-gain.40418/#post-545862]</blockquote>

* '''Input 1 Gain ''' — This control in firmware Ares 12.12 and later for the Axe-Fx III (FM3 and FM9: n/a) allows trimming the Input 1 gain to adjust for variations in guitar output level without having to adjust each preset.
* '''Input block level''' — increase Level in the Input block to increase the signal strength entering the grid. The Level parameter in each block before the Amp block also has an impact on the signal entering the Amp block.
* '''Drive block''' — insert a Drive block before the Amp block. Select a type such as FET Boost or Tape Dist for a clean boost and attach a pedal to its Drive parameter. Or set a Drive block to TS808 or something similar with Drive all the way down and Level turned up to tighten low end.
* '''Input trim''' — Input Trim in the Amp block lets you decrease or increase the level of the signal going into the Amp block. The difference between the High and Low inputs on a Fender amp is around -6 dB, which equals to Input Trim at 0.500.
* '''Drive parameters''' — each Amp block has one or two Drive parameters controlling the amount of gain. You can assign an external controller to vary the gain.
* '''Master volume''' — increase Master Volume for more power amp distortion. Increase Mstr Vol Trim on the Advanced parameters page to increase the range of the master volume.
* '''Boost''' — engage Boost in the Amp block to crank the input level into the Amp block. Alternatively use a Filter or Volume block before the Amp block.
* '''Bright switch''' — engaging the Bright switch may increase gain with some models.
* '''Saturation''' — engage the Sat(uration) switch in the model.
* '''Pitch Follower''' — attach the Pitch internal controller to the Overdrive control. [https://forum.fractalaudio.com/threads/5-minute-tones-pitch-follower.152930/ Demonstration by Leon Todd]
* '''Gain Enhancer''' — this control simulates the acoustic reinforcement of a loud amp coupling into the guitar which also adds gain. [[Amp_block#OUTPUT_COMPRESSION_.2B_TYPE_.2B_THRESHOLD_.2B_CLARITY|More information]]
* '''Morph''': morph between gain settings using two amp blocks (Axe-Fx only) and Volume blocks. [https://www.youtube.com/watch?v=9ncGcU0QS2A Demonstration]
* Other possibilities:

<blockquote>(Jay Mitchell) "Cascade one amp block into another. Turn off "Sag" in the first one. Now you've got an extra preamp feeding your amp, which opens up an incredible spectrum of gain staging. For example, think Twin Reverb preamp, with Plexi tonestack set to "post," feeding a Plexi 2 with default settings. The possibilities exceed anything one person could hope to explore in a lifetime. You can get it awfully close. You want to minimize the effect of the preamp in Amp 2. To do this, set the 2nd Amp's Bright to off, MV to a high value and find a neutral setting for the tone controls in the 2nd Amp. Then use Drive in the 2nd Amp for your MV. The amp types you choose for this arrangement will make a huge difference, as will quite a few parameter settings."</blockquote>

<blockquote>(Jay Mitchell) "Start with Tape drive, set the clipping mode to "HV tube", Drive moderate, Level as appropriate for the amp block it's driving, and you'll have another tube gain stage, complete with EQ."</blockquote>

Adjusting gain on low notes only:

<blockquote>"If you want less distortion on low notes, there are several ways to achieve this:
# Use the Low Cut
# Increase Definition
# Increase Xfrmr LF.

The first two reduce low frequency content going into the preamp, the last one reduces it going into the power amp (there's a hidden low-cut between the preamp and power amp but the user doesn't have access to this). So it depends on where you are getting the distortion from. If it's mostly preamp distortion, use #1 or #2. Otherwise use #3. You can add bass back with the Depth knob or in the EQ page. The default settings are accurate for the amp being modeled. As amps become more modern, it seems people's taste agree with yours and many modern amps feature aggressive low-cut and then add bass back in the power amp. So what you are doing is "modernizing" your amp. For example, the HBE has a very high low-cut and then adds bass back with a fixed Depth circuit." [http://forum.fractalaudio.com/threads/warmth-from-6-0-to-9-0.59934/#post-747576]</blockquote>

Also:
* [https://forum.fractalaudio.com/threads/understanding-all-the-different-gain-controls.95018 Cliff's Tech Note about the different gain controls]
* [https://forum.fractalaudio.com/threads/wicked-wiki-4-adjusting-amp-gain.49193/ Wicked Wiki article]

==Clean up gain with the guitar==

<blockquote>"The amps clean up exactly like their analog counterparts. This is a common complaint with modelers because people use more gain because they listen at lower volumes. With a real amp the volume is loud which provides acoustic reinforcement to the guitar which enhances sustain. At lower volumes this is missing so people increase the gain." [http://forum.fractalaudio.com/threads/the-axe-and-guitar-volume-controls.145331/#post-1718891]</blockquote>

<blockquote>"It's actually one of the things we test when creating models. We even go beyond that. We compare the harmonic spectrum at various input levels as well to make sure the distortion characteristics change in the same way. And you can't do this with just a sine wave, you need to test both harmonic and intermodulation products." [http://forum.fractalaudio.com/threads/the-axe-and-guitar-volume-controls.145331/#post-1718918] </blockquote>

<blockquote>"Here's a little trick to enhance the "clean up with guitar volume knob" thing. In the Amp block go to the Dynamics page. Set the Compressor Type to Feedback. Turn up the Output Compression to taste. Notice that when you play harder the amp will distort more. Now you can use the Input Drive and/or Trim to reduce the input gain so that when you play softer or roll off the volume the amp will clean up. Real amps get this from power supply sag but this requires the power amp be driven hard which can get muddy. This trick allows you to get that same response without cranking the Master Volume." [http://forum.fractalaudio.com/threads/clean-to-mean-w-the-volume-knob.144394/]</blockquote>

<blockquote>"To increase the "clean up with volume knob" lower the gain, set the Compressor Type to Feedback and dial in a bit of Output Compression. You can also use the Gain Enhancer mode which results in a more dynamic sound." [https://www.thegearpage.net/board/index.php?threads/axe-fx-iii-effects.2260258/post-32648602] </blockquote>

[https://forum.fractalaudio.com/threads/the-modelers-dont-clean-up-with-the-volume-knob-myth.154557 Cliff's Tech note:]
<blockquote> "One often hears pundits proclaim "Modelers don't clean up when rolling off the volume knob". While this may be true of some products we actually test and compare this to our reference amps. We measure the THD and output volume at different stimulus levels to ensure that the response is the same. The reason for this myth stems from acoustic feedback. Real amps are LOUD. Modelers are usually played at much lower volumes.

Consider the following [https://forum.fractalaudio.com/attachments/volume_myth-png.58779 diagram]:

This is a block diagram of a model of what happens when playing a guitar with a speaker. Vg is the signal generator (your guitar). Sound waves from the speaker are fed back to your guitar and add to that signal. This signal is then attenuated by the the volume pot, k. The signal is amplified by the amp gain, A. Some portion of that signal is fed back, B.

The formula for a closed loop system like this is Acl = kA / (1 - kAB), where Acl denotes the closed loop gain. The open loop gain is given by Aol = kA.

Let's consider some examples.

In the first example let's assume the amp gain, A = 10, the volume knob is wide open, k = 1 and a mere 2% of the signal is fed back, B = 0.02. Using our formula we get:
Acl = 10 / (1 - 10 * 0.02) = 12.5.

The open loop gain is Aol = 10.

That tiny 2% of feedback has INCREASED the effective gain by 25% (!!!). If the amp is approaching distortion then it will get more distorted.

Now consider what happens if we roll of the volume knob a bit. Let's assume everything else is the same but we set our Log10A volume pot to halfway which means k = 0.1. Now we get:
Acl = 0.1 * 10 / (1 - 0.1 * 10 * 0.02) = 1.02
and Aol = 1

Rolling our volume knob to halfway now only gives a paltry 2% of gain increase for the same amount of acoustic feedback. So when the volume knob is wide open the amp has effectively almost 25% more gain than when rolled off halfway!

Now let's look at what happens when we lower the amount of feedback which would occur if we turned down the volume of our speaker. Let's leave everything the same but reduce our feedback to 1%.

Our first example with the volume pot wide open now becomes:
Acl = 10 / (1 - 10 * 0.01) = 11.1
Aol = 10

And our second example becomes:
Acl = 1.01
Aol = 1

So we see that the closed-loop gain is highly dependent upon the speaker volume. Simply reducing the speaker volume by 6dB lowers the effective gain increase considerably.

When playing with a loud amp the positive feedback from the speaker into the guitar effectively increases the gain of the amp when the volume control is wide open. As you roll the volume control off the amount of gain increase is lower. This gives the ILLUSION that the amp cleans up more when you roll of the volume but it's not the amp that is cleaning up, the signal into the amp is lowered more than if there were no feedback.

When using a modeler people almost always have the volume lower because amps are too loud. Lowering the volume reduces the feedback which in turn lowers the gain enhancement. To compensate people raise the gain of the model but now when you roll off the volume it doesn't clean up as much because the gain is higher. IOW, to compensate for the reduced feedback the user increases the gain, say, 25% to get the same effective gain as the loud amp but when rolling off the volume the amp gain is still 25% higher so it doesn't clean up as much.

P.S.
An interesting result occurs if we let B = 0.1:
Acl = 10 / (1 - 10 * 0.1) = 10 / 0 = infinity.
This is what happens for controlled feedback. The closed loop gain approaches infinity and the loop becomes unstable and oscillates. That's why controlled feedback is easier to obtain at higher volumes, the feedback coefficient is greater. Another way is to move closer to the speaker. Since sound pressure is inversely proportional to the square of the distance moving 50% closer results in four times the feedback!

You can simulate this by using the Output Compression control and setting the Compressor type to "Feedback". It won't simulate controlled feedback. It does a good job of simulating gain enhancement."</blockquote>

Cygnus SpectrumTrack:<blockquote>"SpectrumTrack(TM) ensures that the frequency response of the model matches the real amp at all levels of input excitation. If you've played other products you may notice that the response deviates if you roll down the volume on your guitar. For example, the ****** gets noticeably more midrangey when you roll off your guitar volume. The ***** gets thinner. Etc, etc. This error in response also manifests when varying your picking intensity, especially for low- to mid-gain tones. SpectrumTrack(TM) compares the model to the reference amp at a wide range of excitation levels and ensures that the model's response matches that of the reference amps." [https://forum.fractalaudio.com/threads/spectrumtrack™.173391/post-2099492] </blockquote>

==Bi-amping==

The Enhancer block and the Micro Delay / Mic Distance parameter in the Cab block let you create a stereo image out of a single mono guitar. Another approach is the Pitch trick in the Petrucci factory preset on the Axe-Fx III, FM3 and FM9. Or try this [https://forum.fractalaudio.com/threads/michael-dolces-ping-pong-trick.151065/#post-1797076 delay trick].

==Replicating the sound of Kemper amp profiles==

<blockquote>"The Axe-Fx III models are extremely accurate. The Kemper has its own vibe which a lot of people like. It's characterized by lots of midrange compression. You can replicate this on the Axe-Fx by setting the Output Compression type in the Amp block to Feedback and dialing in ~6 dB of compression. Adjust to taste. The distortion of the Kemper is smoother than a real amp as well. You can replicate this by decreasing the Power Amp Hardness." [https://forum.fractalaudio.com/threads/axe-fx-iii-clean-amp-sounds-compared-to-kemper-cleans.151497/post-1804532]</blockquote>

<blockquote>"Turn off all effects in the KP. Isolate the Cab in the KP. Then do an IR capture of it.
Turn on the Amp in the KP. Dial in an amp that's close. Be sure to listen with the guitar volume turned up and down as you (though the KP won't behave like the amp did in this test, it will help you hear the amount of gain and also the pre-EQ.) Then follow the cab with a Tone Match block if needed, using the instructions in the Tone Match Mini Manual. Method 2 is to use NO cab block in the Axe-Fx. Skip the IR capture and use a Tone Match block to achieve the match all at once." [https://forum.fractalaudio.com/threads/tonematching-kemper-and-capturing-irs.179681/post-2193681]</blockquote>

About profiling:
<blockquote>"Using neural networks is possible but training a NN takes hours and requires hardware that a consumer modeler would not have (i.e. inference accelerators). That said, my tests have shown that white-box modeling outperforms profiling and NN in terms of accuracy and aliasing. Whether that sounds "better" is subjective." [https://forum.fractalaudio.com/threads/iv-anywhere-on-the-horizon.184287/post-2273416]</blockquote>

==Noise, fizz, crackle, sizzle, intermodulation, crossover distortion==

Fizz and crackle are terms to describe certain things people hear when playing an amp model.

'''Fizz''' — high-frequency noise or hiss, which almost seems detached from the basic sound, floating above it. It's only there briefly after striking a chord or tone, like some kind of interference. Best heard when playing a model with power amp distortion.

'''Crackle''' — side-effect of the initial attack, which halts but not gradually, it kind of stutters before it stops. Best heard when playing a clean amp model at high master volume.

People play through their Fractal Audio amp modelers, hear fizz or crackle, and think there must be something wrong with the modeling or their settings. In fact, they are listening to the realistic equivalent of a real amp, because real amps also generate fizz and crackle. You need to listen very closely to the guitar speaker to hear it. That's why you'll hear it better through a modeler, because these emulate a close-miked guitar sound when using cabinet modeling.

Fizz and crackle attribute to the authenticity of amp modeling. They also help to make the guitar stand out in the mix.

<blockquote>"Fizz is desirable. Almost all high gain amps use a lot of feedback on the last triode stage to make it as "hard" as possible. This is typically done by using no cathode cap or a small cathode cap. You never see big cathode caps on the last stage of a high-gain amp. This gives lots of negative feedback and makes it clip harder. Another technique is to use negative feedback to the grid. This is done in 5150-based designs which makes the stage clip even harder. The last stage of a 5150 basically looks like a diode clipper. The harder the clipping the more overtones that are created and the better the tone cuts. Without those overtones your sound is lost in the mix. Amp designers know what they are doing. Trust them." [http://forum.fractalaudio.com/threads/fizz-is-good.67719/#post-833875] </blockquote>

<blockquote>"If you start trying to dial out what you call "fizz" and "artifacts" you're going to end up with a tone that doesn't cut. It might sound good to you but it won't fit in the mix. That fizz and sizzle is what makes those classic rock tones work. Listen to some isolated tracks of VH and AC/DC and you'll hear a ton of high-end sizzle. In the mix, however, it's not noticeable. If you remove it then the guitar sounds dead." [http://forum.fractalaudio.com/threads/tone-envy-a-case-of-the-fizzies.61661/#post-767039] </blockquote>

<blockquote>"Fizz on the decay is natural and it's what tube amps do. If you don't like it you can reduce the Triode Hardness but then it won't cut in the mix as well." [http://forum.fractalaudio.com/threads/tweaking-the-axe-fx-scratchyness.76600/#post-936024] </blockquote>

<blockquote>"The "fizziness" of clipping is determined by how "hard" the clipping is. There are three primary places that clipping occurs in a tube amp: the preamp tubes, the phase inverter and the power tube plates. Preamp tube clipping can range from soft to hard depending upon the design. Phase inverter (PI) clipping, which is actually the power tubes grids clipping, is very hard. Power tube clipping ranges from soft to hard depending upon the amount of negative feedback in the power amp. Preamp tube clipping is comprised of cutoff, which is soft, plus saturation, which tends to be hard. Actual saturation rarely occurs because most preamp stages are designed such that the grid clips before the tube enters saturation. Grid clipping is hard. Local negative feedback is used in the form of cathode caps to shape the response of a preamp stage. If there is no cathode cap then there is negative feedback at all frequencies which increases the hardness of the clipping. The last stage usually dominates the clipping. Some amps have no cathode cap on this stage, e.g. JCM800, and therefore have hard preamp clipping. The Axe-Fx II does not expose the negative feedback settings for the preamp stages to the user, these are hard-coded. Reducing the Triode Hardness parameter will soften the clipping more-or-less depending upon the particular amp model. In a typical tube amp the power tubes start to clip right about the same time the PI/grid clipping occurs. This is intentional so as to get the most power from the tubes. However some amps are intentionally mismatched as the designer's intent was to get more power tube clipping than PI clipping (i.e. Trainwrecks). The Transformer Match parameter adjusts the relative onset of power tube vs. PI/grid clipping. Lower values will cause the PI/grid clipping to occur before power tube clipping. Higher values will cause the power tubes to clip before the PI. Note that the power tube plates follow the impedance curve of the speaker so while the PI/grid may be designed to start clipping first, this only occurs in the midrange. At frequencies above 1 kHz or so the power tubes clip first since the voltage on the plates increases as a function of the speaker impedance. The first thing to clip tends to dominate as once you enter clipping the effect of clipping elsewhere is diminished. Negative feedback around the power amp attempts to linearize the transfer function. The more negative feedback the more the power amp is linearized. However this also causes the clipping to become harder. A power amp with no negative feedback will go into clipping softly. As you increase the negative feedback the "knee" gets sharper. The Damping parameter is the negative feedback control. Higher values give more feedback and harder clipping. Presence and Depth work by modifying the negative feedback. As you increase them the feedback gets less so by turning up the Presence you get softer clipping in the power amp. Therefore to decrease the hardness of the power amp clipping: reduce Damping, increase Presence, increase Transformer Match. To reduce preamp clipping hardness reduce Triode Hardness. There is no parameter exposed to adjust the PI hardness. HOWEVER, the relative hardness of clipping is not all that audible. You have to listen closely. The IR is far more important in the final result. Some IRs let through a lot more high frequencies and therefore sound more fizzy. Furthermore overanalyzing this is inadvisable. Many amps are specifically designed to clip hard as this gives a more aggressive tone that fits better in the mix. Some amps actually attempt to increase the hardness of the clipping as much as possible by using diode clipping or using very high values of negative feedback (i.e. Modded Marshalls, Camerons, 5150 III). Listening at low levels fools your ear. Our ears are more sensitive to midrange at low listening levels. This means we hear the clipping differently than when listening at the actual level the real amp would be generating." [http://forum.fractalaudio.com/threads/ghost-fizz.77539/page-7#post-947075] </blockquote>

<blockquote>"When listening to things at a low volume fizz will be more noticeable. Power amp distortion can be particularly fizzy but we don't notice it because the amp is usually really loud when the power amp is distorting." And: "I was sitting in my chair about 3 feet from a 4x12 A/B'ing a JCM800 to the prototype Axe-Fx II some years ago. I was astonished at all the grit and fizz coming from the amp. The model was way too smooth. I sat there just playing a major 3rd interval listening to the crackle from the amp whereas the model did not have this. The big thing was the crackle on the note decay. The amp sounded like frying bacon as the note died out. It would go "gcchhhh crackkklleee bzzzzzz". I grabbed other amps and noticed the same thing from all of them. It was then that I realized I had a lot of work to do and spent a couple years researching how to make a digital amp modeler replicate all that stuff. All that stuff, though, gives you note separation and helps you cut in the mix. It turns out that tube amps do strange things when overdriven and those old concepts of soft clipping circuits are wrong. Tube amps get nasty and clip very hard and very asymmetrically." [http://forum.fractalaudio.com/threads/getting-a-lot-of-fizz-when-turning-the-cab-sim-off-and-going-to-real-cab.79862/#post-971125]</blockquote>

<blockquote>"I prefer the "fizz" on probably because I grew up with it. I just like the extra grit. When you're playing in a group context that grit seems to make the guitar cut better and fills out the sound. Without it things sound sterile. I spent months trying to capture that. One day one of my employees came by the lab while I was working on the new algorithms. I was trying to explain the grit to him that I heard in my JCM800. "Hear that sizzle on top of the notes? Hear that raspy, bacon frying sound? That's what modelers are missing." So I spent months figuring out where that came from and how to replicate it. All IMHO." [http://forum.fractalaudio.com/threads/so-thats-what-you-were-calling-fizz.45253/#post-592172] </blockquote>

<blockquote>"The simplest way to remove fizz is turn down Master Bias Excursion." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317936]</blockquote>

<blockquote>"The "buzziness" of IM is a function of the "hardness" of the clipping circuit. The first thing you need to do is determine what is distorting: preamp or power amp. Power amp distortion is typically harder than preamp distortion due to global negative feedback. If you are using a modern amp model, i.e. something with a Master Volume, then there is a very good chance you might be overdriving the virtual power amp. In this case simply lowering the Master Volume will reduce IM. If it's preamp distortion then you can reduce Preamp Hardness or experiment with the Preamp Bias to change the distortion character. The Axe-Fx II is extremely accurate. Understanding how real amps work will allow you to adjust things to achieve your ultimate tone. To put this to rest (again, for the umpteenth time): http://www.fractalaudio.com/tmp/blues_jr.mp3. One clip is the amp, the other is the model. All controls set the same. The reason that it's more "noticeable" with modelers is that there is a lot more high frequency content in a typical IR. When you listen to your tube amp through its speaker you are in the far field and usually somewhat off-axis. There is less high frequency content reaching your ears compared to what a microphone records. Go put your amp in an isolation room and listen to it through the control room monitors. You'll be astonished at what you hear." [https://forum.fractalaudio.com/posts/1374762] </blockquote>

<blockquote>"The "buziness" of IM is a function of the clipping hardness. As I stated before you need to determine whether you are getting power amp or preamp distortion. In general preamp distortion is softer but not always. It depends on the circuitry. You can reduce the clipping hardness with the Preamp Hardness and Power Amp Hardness parameters. This ONLY changes the shape of the virtual tube though. The final clipping behavior is also dependent on the surrounding circuitry which the user has no control over. For example a JCM800 preamp actually clips pretty hard because there is no bypass cap on the last triode's cathode. Therefore there is a lot of local negative feedback on that stage which makes the resulting transfer function "harder". In contrast a 1959SL Plexi has a bypass cap which softens the transfer function. Power amp clipping behavior is dependent upon the amount of global negative feedback. The less feedback the softer the distortion. That's why "Class A" amps have softer clipping as they have no negative feedback. Fenders, otoh, typically have 3-6 dB of gain reduction which makes the power amp clip harder. Therefore you can reduce negative feedback to soften the clipping behavior if your distortion is coming from power amp overdrive." [http://forum.fractalaudio.com/threads/behind-note-buzz-help.114938/page-2#post-1374519] </blockquote>

<blockquote>"Crossover distortion occurs when you play very lightly. To really hear the effect of crossover distortion turn the Power Tube Bias parameter all the way down and play lightly. You'll hear a scratchy sound. This occurs because the waveform gets a kink in it at the point where one tube stops conducting and the other starts. Some people actually like the sound and I've heard rumors that EVH liked his amps biased cold to get some crossover distortion. Output transformers can create a type of crossover distortion as well due to the BH curve being nonlinear at the origin." [http://forum.fractalaudio.com/threads/does-anyone-else-get-a-crackling-sound-out-of-their-frfr.120078/page-4#post-1429273] </blockquote>

<blockquote>"It's called intermodulation. No only do actual amps do this, ANY device that distorts the signal will do this." [http://forum.fractalaudio.com/threads/unwanted-ring-mod-sounds-when-playing-double-stops.140598/#post-1666025] </blockquote>

<blockquote>A "Tweed" amp has a cathode biased power amp. Most Fenders are fixed bias but some of the earlier ones, like the 5E3, are cathode biased. Most cathode biased amps (often erroneously referred to as Class A) will go into Class-B operation when driven. Class-B operation creates crossover distortion. The reason a cathode biased amp goes into Class-B operation is because the capacitor in the cathode bias network charges up when the tubes conduct. For example with no input signal the voltage on the cap might be, say, 10V. When each tube conducts more current flows from the supply which charges the cap up and increases its voltage to, say, 20V. The bias voltage has effectively doubled which means the tubes are now biased very cold and the amp runs Class-B. When you stop playing the bias voltage settles back to 10V. Start playing again and the cathode cap charges up again. The time constant to charge the cap is on the order of milliseconds so it takes some time, it's not instantaneous. Some amps use separate cathode networks to reduce the amount of bias shift, i.e. Matchless, Bad Cat, etc. but this increases cost. The sound of Class-B operation is a raspy, fizzy, crackly sort of sound as crossover distortion creates a very different spectrum than clipping. Some people like the sound and there are actually pedals that intentionally create crossover distortion. Rumor has it that EVH liked his amps biased cold so he would get more crossover distortion. Crossover distortion is mostly in the high frequencies. When listening to the proverbial "amp in the room" the high frequency rolloff of the speaker will mask it to a great extent. Close micing an amp yields a lot more high frequencies which will make crossover distortion more noticeable. If you have an Axe-Fx you can experiment with the bias shift in these types of amps via the P.A. Cathode Resistance parameter. Turn it up and the bias will shift more resulting in more crossover distortion as the power amp is driven. Turn it down and the bias will not shift as much and the amp will remain in Class-AB operation longer. You can tell if an amp is cathode biased by the default value. If it is 0.0% then it's a fixed bias amp, otherwise it's cathode biased. Some amps exhibit this more than others. The Suhr Badger has a lot of bias shift but it's still a great sounding amp, probably because the conjunctive filter rolls off the high end which helps mask the crossover distortion." [https://www.thegearpage.net/board/index.php?threads/squirrel-comes-back-in-spades-in-helix-2-81-tweed-nrm-lol.2077647/page-16#post-29183540]</blockquote>

<blockquote>"The AC power supply is modeled and any hum and ghost notes in the power amp will be reproduced. What is not reproduced is hum due to AC heaters, thermal noise, and other sources of interference. These are considered objectionable." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-15-00-public-beta-1.168197/post-2020785]</blockquote>

<blockquote>"That's what amps do. You don't hear it through a guitar cab typically but using close-mic'd IRs it's more noticeable. You can reduce it by turning on the Plate Suppressor diodes. Trainwrecks have plate suppressor diodes for just this reason." [https://forum.fractalaudio.com/threads/note-decay-crackle-sizzle-noise.193575/post-2407689]</blockquote>

[http://en.wikipedia.org/wiki/Intermodulation Wikipedia: Intermodulation]

<blockquote>(crackling sound through FRFR) "That's what amps sound like. Go put an amp in an isolation room with an SM57 on it. Listen in the control room. You'll hear the same thing. You don't hear it as much using a real guitar cab because the high frequencies are rolled off which softens the sound." And: "You're probably just hearing "tube crackle". This is most noticeable when letting chords ring out as the sound decays. It's more noticeable with FRFR because of the extended high frequency response of near-field IRs. Tube crackle occurs when playing more than one note typically. When you play multiple notes (as in a chord or even a diad) the amplitude "bounces" around as the multiple notes reinforce each other or cancel each other. The result is an envelope that is not uniform. The peaks of the waveform clip but the troughs do not. This causes a crackling sound when you get on the edge of distortion because the points at which distortion occurs are far enough apart in time to be audile. You can reduce it by softening the distortion. Reducing Preamp and/or Power Amp Hardness will reduce the crackling but this will deviate from authenticity." [http://forum.fractalaudio.com/threads/does-anyone-else-get-a-crackling-sound-out-of-their-frfr.120078/page-4#post-1429200] </blockquote>

<blockquote>"Tube crackle is most noticeable when letting chords ring out as the sound decays. It's more noticeable with FRFR because of the extended high frequency response of near-field IRs. Tube crackle occurs when playing more than one note typically. When you play multiple notes (as in a chord or even a diad) the amplitude "bounces" around as the multiple notes reinforce each other or cancel each other. The result is an envelope that is not uniform. The peaks of the waveform clip but the troughs do not. This causes a crackling sound when you get on the edge of distortion because the points at which distortion occurs are far enough apart in time to be audile. You can reduce it by softening the distortion. Reducing Preamp and/or Power Amp Hardness will reduce the crackling but this will deviate from authenticity." [http://forum.fractalaudio.com/threads/does-anyone-else-get-a-crackling-sound-out-of-their-frfr.120078/page-2#post-1428924] </blockquote>

Fractal Audio's processors do not create or generate noise by themselves. Noise with high gain amp models is noise which enters the processor at the input and is then amplified by the processor.

<blockquote>(Axe-Fx II) "On the Ultra I would use the gate on high gain patches but I find I don't need it now. I did some measurements and the II is at least 10 dB better SNR." [http://forum.fractalaudio.com/threads/funny-thing-at-rehersal.41117/#post-552329] </blockquote>

<blockquote>"There are noise "reduction" techniques but all alter the desired signal in some way. Noise gates are among the most useful for our particular needs. Digital cameras use various techniques based on the statistics of the image (i.e. if an area of the image is monochromatic heavier filtering is applied). The Intelligent gate in the Axe-Fx uses some crude statistical processing where the statistics are based on the typical stats of a typical guitar. IOW, noise reduction is destructive. You can't beat the laws of physics. So you can't remove noise without somehow altering the original signal." [http://forum.fractalaudio.com/threads/eliminating-noise.109312/#post-1308096] </blockquote>

<blockquote>"The amp model doesn't add noise, it just amplifies it." [http://forum.fractalaudio.com/threads/eliminating-noise.109312/#post-1308121] </blockquote>

<blockquote>"To get the best noise performance it is important that the Instr In trim is set correctly in the I/O > Input menu. Set this as high as possible without clipping the input." [http://forum.fractalaudio.com/posts/956435] </blockquote>

<blockquote>"Guitars make noise. Amplifiers amplify that noise. A noise gate will remove that noise WHEN YOU ARE NOT PLAYING. Expecting a power conditioner to remove noise at the guitar is illogical. There are two types of noise guitars make: thermal noise (hiss) and interference (which isn't technically noise). You can't do anything to reduce the hiss aside from reducing the temperature considerably which isn't practical. You can reduce the bandwidth which will reduce the apparent noise but it may make the guitar sound dull. You can reduce interference (hum and buzz and other periodic noises) in two ways: at the source and at the receiver (the guitar is the receiver). To reduce it at the source you have to find the source(s) and shield them, reduce the loop area, etc. At the receiver you reduce interference by shielding or using humbucking pickups or ideally both. Computers are significant sources of interference. Computers with windows are especially bad. The inverse square law tells us that one way to reduce interference is to simply move further away from the source." [https://forum.fractalaudio.com/threads/weird-high-frequency-hiss.161463/post-1934363]</blockquote>

<blockquote>"Firmware cannot add or remove noise. Anyone having noise problems needs to look elsewhere in their system." [https://forum.fractalaudio.com/threads/fw-8-00-noise-issue.154243/post-1835202]</blockquote>

<blockquote>"They can hum do to tube imbalance but they don't add any thermal noise. [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-00.157866/post-1884224]</blockquote>

<blockquote>"Noise isn't modeled. All preamp tubes have separate heating elements. This is called "indirect heating". Directly heated cathodes are no longer used except for rectifier tubes. Regardless direct or indirect heating has no effect on the noise floor. Noise is due to the random motion of electrons in a conductor. You can't "reject" it. You can lower the noise floor by keeping resistor values low (since noise is proportional to resistance) and by paralleling the input triode. No modeler models noise. The dominant source of noise in any amp, whether real or virtual, is usually your guitar (or rather its pickups). A 10K ohm pickup will have -114 dBv of noise at room temperature. Modern A/D converters, when properly designed, can exceed this so the dominant source of noise is your guitar. This noise is then amplified by the amp (that's why they call them amplifiers). If the amp has, say, 60 dB of gain then that noise is now -114 + 60 = -54 dBv. Gain it up another 20 dB with the power amp and now you're at -34 which can be quite audible. The situation gets worse as you roll off the volume in your guitar as you then introduce more resistance. A typical guitar pot is 500K ohms with an audio taper. If you roll the volume pot down to 8 or so you can easily introduce another 100K of resistance into the signal path. This will increase the noise to -94 dBv which becomes -14 after amplification. Really noticeable then. Bottom line: if you have too much noise you have too much gain. Learning to play with less gain will improve your technique and the quality of your tone. Gain just masks poor technique and reduces clarity, string separation and dynamics." [http://forum.fractalaudio.com/threads/which-models-have-the-lowest-noise.124597/#post-1481877] </blockquote>

<blockquote>"There's not a modeler in existence that adds noise to match the noise of the amp being simulated. Noise is undesirable regardless of "realism". Hum and ghost notes are sometimes modeled but thermal noise never is primarily because the amount of thermal noise is partially dependent upon the resistance of the source (guitar pickup) which is a variable. Furthermore any modeler exhibiting that much thermal noise would be roundly criticized for being excessively noisy." [http://forum.fractalaudio.com/threads/ooooh-charts-and-graphs.135900/page-5#post-1609949] </blockquote>

<blockquote>"Gain doesn't add noise, it amplifies noise. SNR is determined by the hardware. There is equivalent noise at the input (engineering term is Noise Referred to Input). This is due to Brownian motion (thermal noise, also known as Johnson noise). That noise gets amplified. The amp block is digital and adds no noise. It only amplifies (that's why it's called an amplifier). To prove this to yourself, go into a noisy preset and disconnect the input to the amp block. The noise will go away because the amp block doesn't add noise. If it added noise you would still have noise at the output." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-19-00-beta-3.180388/post-2207022]</blockquote>

<blockquote>"Crackliness of the note decay is dependent upon how hard the clipping is. If it's the power amp clipping this is dependent on the hardness of the power tubes (Power Amp Hardness) and the amount of negative feedback (less = softer). If it's the preamp clipping it's dependent on the hardness of the preamp tube (Preamp Hardness) and the negative feedback around the last stage (not user adjustable). A JCM 800, for example, crackles like crazy because there is a lot of feedback on the last preamp stage (since there is no cathode bypass cap). A Friedman BE-100 preamp is similar to a JCM 800 but it has a cathode bypass cap on the last stage and the resulting distortion is much smoother." [http://forum.fractalaudio.com/threads/crackling-sound-in-the-tail-off.136170/#post-1612621] </blockquote>

<blockquote>"Blocking distortion occurs in older designs due to grid conduction. The grid gets forward biased which causes a net offset to develop on the coupling capacitor which, in turn, shifts the bias point. Modern designs incorporate various means of mitigating this (grid stoppers, for example). Some bias excursion is desirable though as without it the distortion can be "sterile". [http://forum.fractalaudio.com/threads/is-there-something-wrong-does-this-sound-normal-odd-distortion.138302/#post-1640780] </blockquote>

<blockquote>"Intermodulation is inevitable. To reduce it, reduce the gain, set bias points to 0 and reduce bias excursion". [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-15-01.168349/post-2023524]</blockquote>

<blockquote>"To reduce/eliminate crossover distortion increase Power Tube Grid Bias. A value of 1.0 will have no crossover distortion." [https://www.thegearpage.net/board/index.php?threads/axe-fx-iii-effects.2260258/post-32648602] </blockquote>

[http://forum.fractalaudio.com/threads/papery-buzz-under-some-models.149193/page-2#post-1772639 Forum discussion]

Aiken White Papers:
* [http://www.aikenamps.com/index.php/what-is-crossover-distortion Crossover distortion]
* [http://www.aikenamps.com/index.php/what-is-blocking-distortion Blocking distortion]

==Aliasing==

The Axe-Fx III lets you set the oversampling mode for Amp and Drive blocks through the Oversampling Mode parameter in the [[Setup menu#Global Settings menu|Setup menu]].

<blockquote>"Aliasing in important in every situation. Aliasing is the creation of harmonically unrelated and undesirable tones in the audible spectrum. Aliasing is most easily heard when playing single notes. It is masked when playing chords but raises the effective noise floor causing a loss of clarity. IME it also causes rapid ear fatigue. A real amp doesn't alias and good modelers have minimal aliasing. The most common way to reduce aliasing is to increase the sample rate either natively or by oversampling. You can also reduce aliasing using antiderivatives but this only works in very specialized cases when using waveshapers." [https://thegearforum.com/threads/modelers-and-aliasing.1815/post-59724]</blockquote>

<blockquote>"The only way to avoid aliasing is to increase the sample rate. Double the sample rate and you double the computational cost. At a minimum. Often times this will quadruple the computational cost because it becomes O^2 operations. Anything that does convolution-like processing (like a NN) will end up with O^2. I.e., if you double the sample rate the number of coefficients in an FIR doubles so you have to do twice as many operations for the FIR at twice the rate. Anything that generates significant distortion should be oversampled (assuming 44-48kHz native sample rate) by at least 4x. That's an absolute minimum IMO. This would cause an increase of 16x computations." [https://thegearforum.com/threads/modelers-and-aliasing.1815/post-59819]</blockquote>

<blockquote>"Any time you have a nonlinear transfer function you create distortion. In guitar gear the transfer function is usually some sort of clipping behavior. At the limit this turns a sine wave into a square wave. A square wave has harmonics that extend well into the ultrasonic range. If you don't oversample enough those harmonics alias into the audible spectrum. No amount of hand-waving changes that. The correct thing to do is to increase the sample rate and then downsample after all the processing is done." [https://thegearforum.com/threads/modelers-and-aliasing.1815/post-59845]</blockquote>

See also: [[Amp_block#Number_of_Amp_blocks|Number of Amp blocks]].

==Glossary of amplifier terms==

Aiken Amplification maintains a collection of very informative technical documents:
* [http://www.aikenamps.com/index.php/white-papers Aiken Amplification: White Papers]

Among these is a glossary of common amplifier terms, which is also included in [https://books.google.com/books/about/The_Guitar_Amp_Handbook.html?id=N9hAviH6gqEC Dave Hunter’s "The Guitar Amp Handbook"]. Make this your first stop when looking for a short explanation of something amp-related.
* [http://www.aikenamps.com/index.php/a-glossary-of-common-amplifier-terms Aiken Amplification: Glossay of common amplifier terms]

==Tube amplifiers explained==
Recommendations:
* [https://books.google.com/books/about/The_Tube_Amp_Book.html?id=JT1I7Ld76YsC The Tube Amp Book (Aspen Pittman)]
* [https://books.google.com/books/about/The_Guitar_Amp_Handbook.html?id=N9hAviH6gqEC The Guitar Amp Handbook (Dave Hunter)]
* [https://books.google.com/books/about/Amps.html?id=NgG8bmBayLwC AMPS! The Other Half Of Rock ‘n’ Roll (Ritchie Fliegler)]

==Tricks==

[[Amp_block#INPUT_TRIM | Simulate Low and High inputs of an amp]]

[[Amp_block#POWER_TUBE_GRID_BIAS | Run an amp in Class-A mode]]

[[Amp_block#POWER_TUBE_MISMATCH | Mismatch power tubes on purpose]]

[[Amp_block#POWER_TYPE | Get rid of ghost notes]]

[[Amp_block#SUPPLY_SAG | Change the rectifier type between tube and solid-state]]

[[Amp_block#LOW FREQUENCY + LOW FREQUENCY RESONANCE | Make a guitar cabinet resonate with a solid-state amp]]

[[Amp_block#OUTPUT_COMPRESSION_.2B_TYPE_.2B_THRESHOLD_.2B_CLARITY | Enhance the acoustic coupling at low volume levels]]

=Parameters=

[[image:Amp block.PNG|450px]]

The list of parameters below follows the editor's page structure.

=General=

==INPUT SELECT==

From the Owners Manual:
<blockquote>
"The Amp block processes audio in mono. This control determines how incoming stereo signals will be processed. You can input only “LEFT” or “RIGHT” channels, or “SUM L+R” (the default setting)."
</blockquote>

Adjust this to make two Amp blocks handle each side of a stereo signal separately. Or when using a single preset with two guitars, each with its own Amp block (FM3: n/a). Or to keep the stereo spread of a stereo delay placed before the Amp blocks.

==(OUTPUT) LEVEL==

The Output Level parameter in the Amp block controls the outgoing level of the Amp block. It has no effect on tone or gain.

It's also the recommended control to set the overall level of the preset, to match it to other presets and to prevent digital clipping.

This parameter can be directly controlled through a switch, assignable in the editor.

Fractal Audio explains:
<blockquote>
"The amp block is always the place to set your volume. The Level control is repeated at several places in the amp block menus for convenience so you don't have to keep switching pages. The Level control has no affect on the tone." [http://forum.fractalaudio.com/threads/so-many-volumes-options.55340/#post-698522]
</blockquote>

About leveling the output of the amp models:

<blockquote>"You can never make the amp models the same volume for the same settings. It's a mathematical impossibility. It also depends on the guitar. If you make two amp the same volume at, say, all knobs at noon, then they may be drastically different if you simply change the Drive from 5 to 7. For example, take a Twin Reverb and a Dual Rectifier and match the volume with all knobs at default. Now increase the Drive to 7.0. The Dual Rec won't get much louder, just more distorted. The Twin Reverb will get much louder. Secondly, the signal strength from the guitar will affect the volume. If you were to make the volume the same between two different amp models and then use a guitar with weaker/hotter pickups the volume may be quite different."</blockquote>

Watch "[https://www.youtube.com/watch?v=BWQ65u39nM8 AxeFxTutorials: Preset Leveling: Master Volume vs Level in the Amp Block]" to learn more.

=Authentic / Ideal=

Read "[[Amp_block#Authentic_or_idealized_amp_controls| Authentic or idealized controls]]" for more information.

==INPUT TRIM==

From the Owners Manual:

<blockquote>
“Amps without an Overdrive control (below) will display Input Trim instead. This allows you to adjust for more or less preamp gain than the actual circuit being modeled. This is different from the Input Drive in that it does NOT interact with the surrounding circuitry to change frequency response as it is varied. In short, use Input Trim to adjust gain without also changing tone.”
</blockquote>

This lets you adjust the range of gain of the amp by increasing or decreasing the signal level at the input of the Amp block. It's the same as Amp Gain in the system settings of the Axe-Fx II and AX8, and Input 1 Gain in the I/O menu on the Axe-Fx III and FM9, but Input Trim operates per preset instead of global. It's also the same as the "neutral" Input Boost type, but Input Boost can't lower the signal.

Values above 1 increase the level. Values below 1 lower the level. 1 is unity gain, 2 is twice.

Input Trim is different from Gain in that it does not interact with the surrounding circuitry to change frequency response as it is adjusted. Use Input Trim to adjust gain without also changing tone.

Fractal Audio explains:

<blockquote>
(Axe-Fx II) "They (Amp Gain and Input Trim) are basically the same thing. The global amp gain has a smaller range as it's designed to be for fine-tuning between guitars whereas the local trim allows you to radically alter the response of the model. The local trim is equivalent to -20 to +20 dB." [http://forum.fractalaudio.com/threads/input-trim-global-amp-gain.40418/#post-545862]
</blockquote>

If the real amp has two inputs (f.e. Low and High), the model is based on the High input. Set Input Trim to 0.500 to get the equivalent of the Low input.

To translate Input Trim values to dB, use this formula: "20 * LOG10(trim value)". In other words: calculate the LOG10 result of the input trim value, and multiply this with 20. Use the LOG10 function on a scientific calculator. Examples:
* Input Trim at 0.500 = -6dB, because: 20*LOG10(0.5)
* Input Trim at 4 = 12dB, because: 20*LOG10(4)

In the Input Trim's modifier menu, a controller can be attached to create a variable boost. This includes [[Scene controllers]]. See "[http://forum.fractalaudio.com/threads/scene-controller-accuracy-for-input-trim.127292/#post-1514686 Translate scene controller settings to Input Trim values]" for more information.

Fractal Audio explains:

<blockquote>
"You might want to convert the Input Trim parameter to dB if you're used to thinking of it that way. As a rule of thumb, every 2x multiplier = +6dB boost. In other words, Input Trim = 4.0 produces a +12dB boost." [http://www.sengpielaudio.com/calculator-db.htm Handy calculator]
</blockquote>

<blockquote>
"Input Trim is something you shouldn't play with normally unless you want to deviate from the actual amp. Input Trim allows you to reduce or increase the gain of the virtual amps input buffer. This is analogous to changing the type of tube for V1 in an actual amp. Some people like less gain for V1 so will replace a 12AX7 with a 12AT7. Some people want a little more gain." [http://forum.fractalaudio.com/threads/new-10-10-firmware-thoughts.71497/page-3#post-877347]
</blockquote>

<blockquote>
"The Axe-Fx II contains a parameter known as "Input Trim". This is just a straight gain control at the very front of the amp block. It has a range of 0.1 to 10.0 (-20 to +20 dB). So what use is a straight gain control at the front? Doesn't the w do the same thing? The short answer is "no". The long answer is "probably not". On many amps the Drive knob, which may also be called Gain or Volume, has what is known as a "bright cap" across the physical potentiometer. This capacitor shunts high frequencies around the pot so that the Drive control is not a straight gain. It has an associated frequency response. As the Drive is turned down more high frequencies are shunted around the pot which results in a net treble boost. If the Drive is turned all the way down the treble boost is maximum, if it is turned all the way up the treble boost is zero. The roots of the bright cap are due to manufacturers trying to compensate for different types of guitars. Guitars with single coil pickups tend to brighter but with less output. The user would then turn the Drive knob high on the amps. Conversely a guitar with humbuckers has more output but sounds darker. To compensate the user would typically turn the Drive down. This will result in a treble boost compensating for the darker response. The Input Trim control allows one to fine-tune the amount of treble boost first and then adjust the amount of distortion. So it is probably more correct to think of the Drive control as a combination Drive/Treble control. With this in mind experiment with the Drive control combined with the Input Trim. Indeed some manufacturers have actually implemented separate Drive and Trim controls on their amplifiers. For example the Fryette (VHT) Deliverance has two controls: a Gain knob and a Cut knob. The Gain knob has a bright cap across it while the Cut knob is just a straight volume adjustment. The purpose of these two knobs is exactly as described above." [https://forum.fractalaudio.com/threads/input-trim.81116]
</blockquote>

<blockquote>
"The Input Trim control allows you to adjust the input attenuation without changing the frequency response. If you turn down the Input Drive and the model has a bright cap the amp will get brighter. Now you may like the brighter tone but wish there were more gain. Input Trim allows you to increase the gain without changing the tone. Conversely you may like the darker tone with Input Drive set high but wish there were less gain. In this case you can lower Input Trim. Most real amps do not possess an Input Trim control. Instead they usually have a switch or two input jacks that select between a high-gain and low-gain input. Almost invariably the difference between these two jacks is 6 dB. All the Axe-Fx amps are modeled using the high-gain input or switch position (if any). To simulate the low-gain input set the Input Trim to 0.5 which is 6 dB less". [https://forum.fractalaudio.com/threads/understanding-all-the-different-gain-controls.95018/post-1138073]
</blockquote>

<blockquote>
"It controls the voltage divider into V1. Many amps, for example, have two 68K resistors feeding V1. If you plug into the High input the resistors are in parallel and the gain is 1.0. If you plug into the Low input the resistors are in series and the gain is 1/2. Input Trim is a more flexible way of accomplishing the same thing but without being constrained to only two gain values."
</blockquote>

<blockquote>
"All the models assume the "Hi" input on the amp was used if there are multiple inputs. If the amp has a Lo input this is typically half the sensitivity so you would set Input Trim to 0.5 to replicate. The beauty of Input Trim is you can set it to any value you like rather than being stuck with a switch with only two values." [http://forum.fractalaudio.com/threads/ax8-clean-tones-input-trim-is-the-key.120261/#post-1431111]
</blockquote>

<blockquote>
"Be sure to set your Input Trim properly. If you are using single-coil pickups then you want to increase the Input Trim. This will optimize the S/N Ratio. With a properly optimized SNR the Axe-Fx has less self-noise than your guitar." [http://forum.fractalaudio.com/threads/best-low-watt-amp-model-to-build-do-it-all-preset-by-altering-guitar-volume-knob.122796/#post-1460865]
</blockquote>

<blockquote>
"0.5 is equivalent to using the Low input jack on amps. If you are using high-output pickups it's often better to use the Low input to get into the sweet spot of the bright cap. [https://forum.fractalaudio.com/threads/the-modeler-equivalent-to-alternate-guitar-tunings.155649/post-1853194]
</blockquote>

==GAIN + OVERDRIVE + MASTER VOLUME==

'''About Gain and Master Volume'''

NOTE: "GAIN" is the same as "Input Drive".

Vintage amps don't have separate gain (drive) and master volume controls. Therefore, Master Volume defaults to "10" in models which are based on these amps. Use Gain to control the amount of preamp gain/distortion as well as volume on non-Master Volume amp models.

Treble peaker circuits found on the gain or volume control on many amps are also modeled. This can be heard as the low frequencies are attenuated more than the highs when the gain is turned down (and vice versa).

Fractal Audio explains:

<blockquote>
"For clean tones the Drive control should be set fairly low and the Master set very high. On a real "Blackface", for instance, the Master is essentially maxed since that amp has no master volume. A Blackface typically achieves full power at around 10-11 o'clock on the volume (Drive). It's also insanely loud. Beyond that everything starts to saturate and clip. If you set the Master low and the Drive high, for clean tones, the low end will tend to get muddy. Good cleans are obtained with little, if any, preamp distortion and a nice amount of power amp distortion. Power amp distortion has a much different character and tends to be glassy and bouncy. Preamp distortion is rougher and more compressed." [https://forum.fractalaudio.com/threads/power-amp-settings-depth-damp-sag.56116/post-706835]
</blockquote>

<blockquote>
"The real key is to adjust the relative amounts of each. You want to balance preamp and power amp distortion for the best tone. What I do is start with the MV low and turn up the drive until I get the desired amount of gain and sustain. Then turn up the MV until I get the desired compression. Then fine-tune each." [http://forum.fractalaudio.com/threads/pre-amp-vs-power-amp-distortion-in-axefxii.46055/#post-601681]
</blockquote>

'''Master Volume'''

From the Owners Manual:

<blockquote>
“The almighty Master Volume is a very important control. It determines the distortion and dynamics characteristics of the power amp simulator, and its setting at any moment can dramatically change the amp’s sound. As it is turned up, the tone controls will have less influence, and the sound will have more “bloom” and touch sensitivity. Settings for Master don’t necessarily correspond to knob positions on the amp being modeled. With a little experimentation, you will learn to dial in different great sounding Input Drive and Master combinations.

When you select an amp type, the Master will change to an appropriate/typical setting for that amp. If a real amp doesn’t have a Master, the “correct” setting will be applied i.e. “10”, or “wide open.”

* At high settings, less gain is usually required, especially for high-gain types.

* Amps designed for preamp distortion will typically sound great with the Master set low to prevent the tone becoming muddy or noisy. This includes the “USA Lead” types and others.

* Amps with negative feedback tend to have “crunchier” power amp distortion, which can get “raspy” when driven too hard. Experiment with the interactivity of Negative Feedback and Master on distortion tone.

* With Power Amp Modeling disabled, either globally or in one specific block, Master Volume becomes a simple level control with 40 dB of range.

* If more power amp gain is desired, Master Volume Trim in the Advanced menu can be used.”
</blockquote>

<blockquote>
(Axe-Fx II) "Amp models now default to a starting Master Volume setting when selected. Also, the proper setting for non-MV amps is now a Master Volume setting of 10.0. Non-MV amps, therefore, will default to a value of 10.0 when selected. If more MV drive is desired for non-MV amps, the new MSTR VOL TRIM parameter in the Advanced GUI page can be used to increase (or decrease) the Master Volume. The starting MV value for non-MV amps is roughly the “sweet spot” for the amp. This is the point where the power amp starts to contribute to the tone and feel of the amp. Decreasing the MV will typically cause the amp to get brighter and less compressed and increasing the MV will cause the amp to get more midrange focus and more compressed. As always, your ears should be your guide."
</blockquote>

<blockquote>
(Axe-Fx II) "The amp modeling improvements have resulted in a significantly increased “sweet spot” for the Master Volume control. Previous advice to keep the Master Volume low for high-gain amp types no longer applies and, in fact, increasing the Master Volume can result in better tone (more bloom and swirl) and much better feel (due to power supply sag). Therefore most non-MV amps now default to a higher value than previously. This may result in louder preset volume which will necessitate reducing the Output Level to compensate."
</blockquote>

The MSTR VOL TRIM parameter in the Advanced GUI page can be used to increase (or decrease) the Master Volume.

Fractal Audio explains:

<blockquote>
"Just multiplies the MV by the amount. You only need to use it if you want more power amp drive and your MV is already at 10. IOW, if MV is 10 and you set MV Trim to 2.0 then the MV will be 20." [http://forum.fractalaudio.com/threads/master-volume-trim.67870/#post-834697]
</blockquote>

<blockquote>
(before "Cygnus" amp modeling) "Master Volume tapers are NOT matched. If they were the amp volumes would jump all over the place when you switched amp types. IIRC I use a Log10A for the MV." [http://forum.fractalaudio.com/threads/axe-fx-ii-firmware-version-12-04-public-beta.80497/page-17#post-978667]
</blockquote>

<blockquote>
"The Master Volume (MV) DOES affect the tone. It sets the level into the power amp modeling. The Level control has no affect on the tone. For MV amps, i.e a 5150, adjust the MV until the desired amount of power amp distortion is obtained. Most MV amps rely on preamp distortion and don't produce much power amp distortion. If you turn the MV up too high on them the tone will get muddy and flubby. Non-MV amps rely primarily on power amp distortion so you need the level into the power amp to be hot enough to push the power amp into distortion." [http://forum.fractalaudio.com/threads/so-many-volumes-options.55340/#post-698522]
</blockquote>

<blockquote>
"I just start low and bring it up until I get the desired compression. Then I chug the E string and if it's too buzzy or flubby I drop it down a bit. For tight, high-gain stuff you want to keep it low. For liquid, spongy tones you want to set it higher."
</blockquote>

<blockquote>
"MV is the most important Amp block control for tone. You have to find the sweet spot. Start at 3 and increase until desired compression is reached. Stock presets are set to sweet spots, subjectively (based on the guitar used and personal opinion). Do not use MV for volume and don't turn it up too much (unless it's a non-MV amp). If an amp has Input Drive and Overdrive controls, use Input Drive for tone shaping and Overdrive as a flat gain control."
</blockquote>

<blockquote>
"As you increase the MV you drive the virtual power amp harder. As you drive the virtual power amp harder the frequency response becomes more dynamic, just like the real amp. And, just like a real amp, there is a sweet spot where the compression, dynamic frequency response, distortion, etc. just feel "right". The particular settings for the sweet spot depend on the Input Drive, tone controls, etc. so there are no hard-and-fast rules. So, as always, use your ears. And don't be afraid to use your ears. You'll be a better player when you learn how the controls interact and how to find the sweet spot. The great players in guitar history new how to work their amps. They didn't rely on someone else to tell them where to set the knobs, they learned themselves." [http://forum.fractalaudio.com/threads/axe-fx-ii-firmware-version-12-04-public-beta.80497/page-28#post-979668]
</blockquote>

<blockquote>
"With Version 13.xx firmware the constraints on MV are lessened. Due to the improved power tube modeling you can increase the MV more without the tone getting flubby or harsh."
</blockquote>

<blockquote>
"The way I dial in the MV is to turn up the MV until the amp stops getting louder. This is the point at which the power amp is saturating heavily. Then I back it off until I get the right amount of preamp and power amp distortion. That's the sweet spot where you get the tone and the dynamics. Too little MV and it's all preamp distortion and there's not much dynamics. Too much MV and the power amp is clipping too much and it can get flubby and/or harsh. Just as with a real tube amp you have to get the power amp cooking to get the best tone and feel. Get that power amp working hard and the supply bouncing around and things get nice." [http://forum.fractalaudio.com/threads/18beta-kick-in-the-balls.96781/page-2#post-1161823]
</blockquote>

<blockquote>
(before "Cygnus" amp modeling) "The taper of the MV on the Axe-Fx does not necessarily match the taper of the actual amp. We use the same taper on every model. IIRC it is a Log10 taper. Many amps use a taper that is more abrupt than that for marketing reasons. For example, a Blues Jr has a linear taper MV. This means the amp is near full volume when the MV is at 3. This gives the impression that an amp is "loud". When the unsuspecting customer is testing the amp and it gets really loud with the MV on 2 the customer instinctively goes "wow, this amp is loud, it must be good". Anyways we use a consistent Log10A taper on every model. In general this means you need to set the MV higher than you would on the real amp. For example if the real amp has a linear taper halfway on the model would be equivalent to 1 on the amp (assuming the amp is calibrated from 0 - 10). The taper of a logarithmic pot has the nomenclature LogXA where 'A' indicates audio and X is the percentage of the element resistance from wiper to CCW terminal with the pot at 50% rotation. So a 1 Megohm Log10A pot would have 100K between the wiper and the CCW terminal when the pot is at "noon"." [http://forum.fractalaudio.com/threads/18beta-kick-in-the-balls.96781/page-3#post-1162192]
</blockquote>

<blockquote>
"All Axe-Fx models have been "modded" to include a Master Volume. Setting the MV to 10 effectively removes it from the circuit." [http://forum.fractalaudio.com/threads/non-master-volume-amps-10-vs-9.98368/#post-1180180]
</blockquote>

<blockquote>
"Those amps (JCM, SLO) are all designed to get their character from power amp distortion. If you don't push the power amp all you are hearing is the preamp which is voiced to be trebly. The power amp then compresses the highs and the sound gets fatter." [http://forum.fractalaudio.com/threads/1-biggest-user-error.103152/page-3#post-1235311]
</blockquote>

<blockquote>
"I was helping a customer out yesterday. He was complaining about lack of feel and thinness. I asked him what his Master Volume was set at. He said 1.5. I asked "why so low?". He said "because that's where I set it on the real amp". I explained that the MV on the Axe-Fx has a much gentler taper than real amp and that 1.5 on the real amp is probably around 5 or more on the Axe-Fx. So he cranked the MV up and exclaimed "wow, that's what I'm looking for!". The MV taper on the Axe-Fx is a Log15A taper. This means the output is 15% of the input when the "pot" is at noon. Most amps use a higher taper than this, say 30A or even a linear taper. This is done as a marketing ploy. The unsuspecting customer sets the MV to 2.0 and goes "wow, this amp is loud". Thing is the amp doesn't get much louder. This also makes adjustment difficult because most of your volume range is constrained to a small fraction of the dial rotation. The Axe-Fx uses a gentler taper so that you can fine-tune the MV easier. So don't be afraid to crank that MV up. When the MV is turned up the virtual power amp works harder which causes the virtual power supply to sag which adds compression which adds feel. It also thickens up the tone when you play harder because the power amp is distorting. You'll get much better results if you learn to find the sweet spot. While playing, turn up the MV until the volume stops getting louder. At this point you are driving the power amp into heavy distortion. Now back off the MV until you get the desired tone and feel. With practice you'll learn to identify how much the power amp is being pushed and where the sweet spot is." [https://forum.fractalaudio.com/threads/1-biggest-user-error.103152/]
</blockquote>

<blockquote>
"If you want the best tones out of the Axe-Fx you should stop copying photos of knob settings and learn how the knobs work. MV is one of the most important knobs as it controls how hard the virtual power amp is driven. Learning to find the sweet spot is an exercise that will pay handsome dividends. Take the JCM800 model. Set the MV very low, say 1.0. Play for a while. The sound will be harsh and scooped with a stiff feel. Turn the MV up to 5.0. Notice how there is more midrange and a softer high-end response, more compression and a better feel. Turn it up all the way and it will get fuzzy and indistinct. A real amp does the same thing. Learning to dial in the MV is among the most important abilities to harness the most from your Axe-Fx." [http://forum.fractalaudio.com/threads/setting-the-master-volume-of-the-usa-iic-deep.107231/#post-1283394]
</blockquote>

<blockquote>
"The Master Volume (MV) controls how much signal level is sent to the power amp. Many vintage amps have no MV control and the power amp runs "wide open". Modern amps often get their distortion from the preamp and the Master Volume then allows the user to control the volume of the amp. The Master Volume in the Axe-Fx II, as well as on real amps, is probably the singular most powerful control in the amp block. As the Master Volume is increased the virtual power amp begins to distort. The virtual power amp also begins to sag and all sorts of beautiful magic occurs. The tone becomes more focused, the dynamic response changes, the note attack is accentuated, etc.”
</blockquote>

<blockquote>
“MV is the one knob that everyone should master (pun not intended). It sets the amount of power amp drive which, in turn, controls how much current is drawn from the power supply which causes the supply to sag. The trick is to find the sweet spot. Too much MV and it can get too compressed. To little and the amp will be stiff and too scooped. The MV works just like a real amp's MV except it won't get deafeningly loud if you turn it way up.” [http://forum.fractalaudio.com/threads/axe-fx-ii-firmware-17-04-released.94957/page-8#post-1138962]
</blockquote>

<blockquote>
"With high-gain amps I start with the MV very low, say 2.0. Dial in the tone and gain and then bring the MV up until you hit the sweet spot. Back off the gain a bit if it's too gainy at that point.” [http://forum.fractalaudio.com/threads/axe-fx-ii-firmware-17-04-released.94957/page-8#post-1139089]
</blockquote>

<blockquote>
"One common theme with new users is the "blanket over the sound" complaint. Often this is due to excessive Master Volume values. The Master Volume behaves just like the actual amps. However, unlike an actual amp, if you put it on 5.0 it won't cause your cat to hide for several days. This can cause the user to set the value too high as the physical feedback of painfully loud sound is not present. As you turn up the Master Volume many amps get darker and the bass gets mushy. The key is to find the sweet spot. Do this exercise: Take an amp like the HBE. Set the MV to around 2.5 and turn the Level to a comfortable volume. Turn the Presence up to around 8.0. Copy the settings to "Y" by double-clicking the "Y" button. Now you have the same amp model and values in X and Y. Turn up the MV in Y to, say, 6.0 and lower the Level until the volume is the same. Go back and forth between X and Y and notice how much darker Y is. This occurs because the virtual power amp is distorting, and quite heavily. Due to the impedance curve of the virtual speaker load this causes the bass and high treble frequencies to clip but not the midrange. The result is, naturally, compressed bass and high treble which can sound muddy and indistinct. Modern MV amps are not designed to overdrive the power amp considerably. They are designed to get most of their distortion from the preamp and then adjust the MV until the power amp just starts to clip which is the "sweet spot". Some amps, like the Recto Modern, will distort the power amp at very low MV values, around 2.0. In real life these amps are painfully loud at these settings but in our virtual world we are unaware of this because the Level control allows us to adjust the volume to any arbitrary level. Some modeling products intentionally limit how hard their virtual power amps can be overdriven. Even with the MV on 10 the virtual power amp is not being overdriven that much. Of course this is unrealistic. Our modeling is accurate and with the MV on 10 you will get the same amount of power amp distortion as the real amp when set to 10. With this great power comes great responsibility and that responsibility is understanding how the control works and how to set it properly." [http://forum.fractalaudio.com/threads/setting-the-master-volume.119903]
</blockquote>

<blockquote>
"A little trick you can do to get the "bounce" of high MV without the muddy bass is to reduce the LF Res value on the Spkr tab. This will reduce the amount of bass clipping in the virtual power amp allowing you to turn the MV up. You can also reduce the HF Res to reduce the amount of treble clipping." [http://forum.fractalaudio.com/threads/setting-the-master-volume.119903/page-2#post-1427734]
</blockquote>

<blockquote>
"At low MV the source resistance into the PI is low which raises the highpass frequency due to the coupling cap and raises the lowpass frequency due to the Miller capacitance and snubber. As you increase the MV the source resistance increases which decreases both of these things. As you keep raising the MV the source resistance then starts to decrease as you get above 50% of the pot value." [http://forum.fractalaudio.com/threads/setting-the-master-volume.119903/page-2#post-1428935]
</blockquote>

<blockquote>
"The Master Volume behaves just like the actual amps. However, unlike an actual amp, if you put it on 5.0 it won't cause your cat to hide for several days. This can cause the user to set the value too high as the physical feedback of painfully loud sound is not present. As you turn up the Master Volume many amps get darker and the bass gets mushy. The key is to find the sweet spot. Do this exercise: Take an amp like the HBE. Set the MV to around 2.5 and turn the Level to a comfortable volume. Turn the Presence up to around 8.0. Copy the settings to "Y" by double-clicking the "Y" button. Now you have the same amp model and values in X and Y. Turn up the MV in Y to, say, 6.0 and lower the Level until the volume is the same. Go back and forth between X and Y and notice how much darker Y is. This occurs because the virtual power amp is distorting, and quite heavily. Due to the impedance curve of the virtual speaker load this causes the bass and high treble frequencies to clip but not the midrange. The result is, naturally, compressed bass and high treble which can sound muddy and indistinct. Modern MV amps are not designed to overdrive the power amp considerably. They are designed to get most of their distortion from the preamp and then adjust the MV until the power amp just starts to clip which is the "sweet spot". Some amps, like the Recto Modern, will distort the power amp at very low MV values, around 2.0. In real life these amps are painfully loud at these settings but in our virtual world we are unaware of this because the Level control allows us to adjust the volume to any arbitrary level. Some modeling products intentionally limit how hard their virtual power amps can be overdriven. Even with the MV on 10 the virtual power amp is not being overdriven that much. Of course this is unrealistic. Our modeling is accurate and with the MV on 10 you will get the same amount of power amp distortion as the real amp when set to 10. With this great power comes great responsibility and that responsibility is understanding how the control works and how to set it properly." [http://forum.fractalaudio.com/threads/setting-the-master-volume.119903]
</blockquote>

<blockquote>
"MV increases the power amp drive. If the power amp is distorting then the apparent volume will decrease as the MV is increased. It's impossible to predict how much the volume will decrease because it's dependent on dozens of other things like the Input Drive, BMT, pickup output, presence of Drive block, etc." [http://forum.fractalaudio.com/threads/wont-happen-independency-of-master-volume-and-level-in-the-amp-block.137392/#post-1631262]
</blockquote>

<blockquote>
(before "Cygnus" amp modeling) "The Master Volume is the only knob in the amp models that may not have the same taper as the real amp. All the models use the same taper (10A IIRC) for consistency. Many amps use a more abrupt taper for marketing reasons. A more abrupt taper gives the impression that the amp is louder." [http://forum.fractalaudio.com/threads/axe-fx-iii-vs-real-fuchs-ods.142679/#post-1689129]
</blockquote>

<blockquote>
"As you raise the MV the power tubes will saturate on the lows and highs first which causes the tone to have more midrange and vice-versa. Most of the controls in the Axe-Fx match their physical counterparts. The exceptions are Presence and Master Volume. Most amps simply have the wrong taper for their Presence controls. For example a 5150 Presence control does absolutely nothing from 0 to 7. All the action happens in the upper 1/4 of the control's range which is just dumb. The Axe-Fx uses a proper taper which gives a nice, even response over the full range of the control. Likewise the Master Volume on many amps is too abrupt. By 2-3 on the knob the power amp is saturating. Again we use a more rational taper so that you have finer control over power amp distortion. The downside of this approach is that if you put the Presence and Master Volume controls in the same position as the amp it won't sound the same. People do this then post videos and proclaim "See? Modeling isn't accurate!!! Toobz rule brah."" [https://forum.fractalaudio.com/threads/legacy-amp-models-consider-revisiting-full-honest-request-and-opinion.160349/post-1920107]
</blockquote>

Firmware Ares 13:

<blockquote>
“Added “Headroom” monitoring meter to Amp block. The most common reason for “muddy” tones with high-gain amps is incorrect setting of the Master Volume control. The Headroom meter displays the voltage at the virtual power tubes in dB. If the Master Volume is too high the meter will be near 0 dB most of the time. Note that this only applies to amps where the power amp is intended to run “clean” like the 6160, Recto, etc. Non-Master Volume amps get their distortion from the power amp distorting so this recommendation does not apply.”
</blockquote>

<blockquote>
(headroom meter) "It can't go above 0 dB. The headroom meter is how close the plate voltage is to ground. It can't ever be below ground so 0 dB is the maximum." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-19-00.180535/post-2207889]
</blockquote>

"Cygnus" amp modeling:

<blockquote>
"If an amp has an MV taper of greater than 15A the model's taper will be 15A otherwise it will match the amp. I.e., a Blues Jr. has an MV taper that is linear (which is ridiculous). The model's taper will therefore be 15A. There are a handful of exceptions, i.e. Camerons have linear taper MV and you need it with them because the signal level into the power amp is very low due to the Jose topology." [https://forum.fractalaudio.com/threads/mv-poll.170996/post-2059425]
</blockquote>

<blockquote>
"In the vast majority of models the knobs behave the same as the amp. There are a handful of models where I've taken artistic license and changed the tapers to give a more useable response. For example the Master Volume in a Blues Jr. is linear taper. This is ridiculous as it makes it very difficult to find the sweet spot. The model uses an audio taper instead which makes finding the sweet spot easier. (..) and now Cygnus firmwares have authentic behavior for most models except in a handful of cases where the manufacturer's choice of taper is dumb." [https://forum.fractalaudio.com/threads/cygnus-is-absolutely-magnificent.173225/post-2096570]
</blockquote>

<blockquote>
"You have to be very careful with the Master Volume. A Recto will start saturating the power amp in Modern mode at VERY low MV settings. Once the power amp starts clipping the tone will change. With digital products I often see people set the MV higher than they would on the real amp because there are no sonic repercussions (i.e., pissing off the wife/neighbors, knocking Grandma's urn off the mantel, etc.). If an emulation sounds darker or more midrangey than the real amp try turning down the MV. If it's a good emulation you should find a point (around 1-2) where you can hear the power amp start to saturate. Go up/down from there to get the desired power amp overdrive." [https://www.thegearpage.net/board/index.php?threads/why-are-rectifier-emulations-so-off.2341907/post-34347979]
</blockquote>

<blockquote>"Sag is also dependent on Master Volume. The higher the MV, the more sag." [https://forum.fractalaudio.com/threads/can’t-nail-the-robben-ford-sound-and-i-know-exactly-why-help.199726/#post-2488659]</blockquote>

See AxeFxTutorials' "[https://www.youtube.com/watch?v=BWQ65u39nM8 Preset Leveling: Master Volume vs Level in the Amp Block]" for more information.

'''Gain, Overdrive:'''

From the Owners Manual:

<blockquote>
“Input Drive sets the amount of preamp gain/distortion. Used in conjunction with the Master Volume, Input Drive determines whether the sound will be clean, broken up, overdriven, or fully distorted. A treble peaker circuit found on the drive or volume control on many amps is also modeled. This can be heard as the low frequencies are attenuated more than the highs when the drive is turned down (and vice versa). For amps that have no Master Volume, Input Drive functions as the amp’s volume control.”

“Amps with Overdrive will not display Input Trim (above). Adjusts overdrive. Note that Input Drive and Overdrive are applied to the appropriate points in the circuit for the amp being modeled, i.e. prior to the last triode stage or prior to the third triode.”
</blockquote>

Some models have Gain and Overdrive controls.

If the real amp has two gain controls, the one closest to the 1/4" input is modeled as Input Drive in the model. The other one is Overdrive.

<blockquote>
(Axe-Fx II) "The Amp block now differentiates amps that have both Input Drive and Overdrive controls, i.e. Mesa Mark series, Dumble, etc. When a model is selected for amps of this type, the menu shows both controls. For other types the menu shows only the Input Drive control (which was formerly called simply “Drive”). The Overdrive control defaults to noon when amps with this control are selected. As such, any presets based on these amps may need to be updated as this control was not present previously and the amount of drive may differ now. Note that these two controls are applied to the appropriate point in the circuit for the amp being modeled, i.e. for Dumble-style amps the Overdrive is prior to the last triode stage. In Mesa Mark amps the Overdrive is applied prior to the third triode."
</blockquote>

Fractal Audio explains:

<blockquote>
"Input Drive increases the gain amount as you rotate the knob clockwise. As the gain increases the tone is shifted from a treble and upper mid emphasis, which produces an up front sparkling tone, to a lower mid and bass emphasis, which produces a thick meaty tone. Overdrive increases the gain amount as you rotate the knob clockwise but with no alteration of the tonal balance. Different combinations of Input Drive and Overdrive settings will have a dramatic effect on the response of the amplifier and the personality of your instrument. It is easy to get familiar with the action of these controls and you’ll be amazed with your ability to make any guitar sound mellow, fat, soulful or aggressive." [https://forum.fractalaudio.com/threads/understanding-input-drive-and-overdrive.71449/post-875745]
</blockquote>

<blockquote>
"Input Drive is the modeled amp's gain, drive, volume, etc. control. It adjusts the attenuation at the input to the amplifier gain stages after the input buffer. On a Marshall Plexi, for example it is the "Loudness" control. On a typical Fender amp it is the "Volume" control. On many high-gain amps it is called either "Gain" or "Drive". On a real amp this is implemented using a variable resistor called a potentiometer. Many amps include a "bright cap" on the drive control which is a small value capacitor placed across the terminals of the pot that bleeds treble frequencies through as the gain is reduced. Sometimes this bright cap is switchable via a switch on the amp. Sometimes it is fixed." [https://forum.fractalaudio.com/threads/understanding-all-the-different-gain-controls.95018/post-1138073]
</blockquote>

<blockquote>
"In a typical amp Input Drive is called various names (Drive, Volume, Gain, etc). It is the knob closest to the input jack. In many cases this potentiometer has a bright cap on it so the frequency response will be dependent on the knob position. In some amps there is also a second drive control. This is your Overdrive knob. It does not have a bright cap so it only affects the gain." [http://forum.fractalaudio.com/threads/new-10-10-firmware-thoughts.71497/page-3#post-877347]
</blockquote>

<blockquote>
"Sometimes they're labeled Gain, sometimes Drive, sometimes Volume. On an Soldano X88 they're labeled "Preamp"." [http://forum.fractalaudio.com/threads/authentic-amp-controls-amazing.148305/page-2#post-1754976]
</blockquote>

<blockquote>
"Some amps possess an attenuation control between the later gain stages. Examples of the are the Mesa/Boogie Mark series, Dumble ODS and others. This control allows the user to vary the gain staging. The Input Drive can be turned up and the Overdrive turned down so that the earlier stages distort more and the later stages distort less and vice-versa." [https://forum.fractalaudio.com/threads/understanding-all-the-different-gain-controls.95018/post-1138073]
</blockquote>

The range of the Gain taper in the amp modeler is 0-10. Volume controls on Fender amps go from 1 to 10, or 11 or 12. [[Amp_block#Authentic_or_idealized_controls| Go here]] for the translation of the real controls to the model.

You can attach a Scene Controller to Gain, and then use scenes to vary the amount of amp gain. Or use an internal or external controller instead. Note that with some amps models this bumps CPU usage.

Fractal Audio explains:

<blockquote>
"Depending upon the amp model it can take a lot of CPU to calculate the Input Drive network. Some amps have simple networks that are rapidly solved. Others, like the Hook Lead and Rhythm models have complex networks that require more math. If you attach a modifier to the Input Drive it is constantly recalculating the network which increases CPU usage."
</blockquote>

<blockquote>
"Some amps have complicated input drive circuitry that requires a lot of calculations. Adjusting the Input Drive control can result in crackling as the time required to recalculate the network is long. Don't attach a controller to the Input Drive on these amps." [https://forum.fractalaudio.com/threads/not-a-bug-possible-bug-in-carol-ann-od-2.153162/post-1821948]
</blockquote>

<blockquote>
"Takes a lot of math to calculate the Drive. Not a bug." [http://forum.fractalaudio.com/threads/not-a-bug-error-sound-with-solo100-rhy-if-it´s-drive-is-controlled-with-scene-controllers.132355/#post-1566823]
</blockquote>

About jumpered channels:

<blockquote>
"Even a small bit of capacitance difference at the inputs of these amps makes a difference. Our models assume a fairly short jumper cable (3-4 inches). In my tests just increasing the length of the jumper cable to 1 ft. changed the frequency response significantly. So if your Y-cable is more than a few inches long it will change things." [https://forum.fractalaudio.com/threads/plexi-input-modeling-question.188339/post-2336388]
</blockquote>

==OVERDRIVE VOLUME==

Added in firmware 21 for the Axe-Fx III. Release notes:

<blockquote>"Added “Overdrive Volume” parameter to Dumble-type amp models (ODS-100, Two Stone, etc.). This is sometimes labeled “Ratio” or “Lead Master”. As the Master Volume on these amps often has a bright capacitor the Overdrive Volume control allows setting the Master Volume higher to counteract the bright cap and then lowering the power amp drive with the Volume."</blockquote>

Fractal Audio:

<blockquote>"Most, if not all, Dumble-style amps have a Ratio/Volume/Lead Master/etc. control so this makes the models complete in that regard. My Fuchs ODS 50 does NOT have a bright cap on the MV but it has an "Output" control for the overdrive channel that is in series with MV." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-00-public-beta-2-beta-2.187991/post-2331157]</blockquote>

==BASS + MID + TREBLE==

From the Owners Manual:

<blockquote>
“While other modelers use simple filters to approximate amp tone controls, our products recreate the exact frequency and phase response characteristics of a classic passive tonestack. In most cases, knob positions can even be matched to settings on the original amps. (Though recognize that many types of amps were built inconsistently with different types of potentiometers from one run to another.)
</blockquote>

Many models provide tone controls NOT offered on the original amp. For example, many amps have no Mid control. To faithfully simulate such amps, set controls they are missing to “noon” (or “0” if you are using the “ACTIVE” Tonestack Type). Of course, you may still adjust these “bonus” controls to achieve innovative tones.” </blockquote>

The exact frequency and phase response characteristics of the tone stacks on the original amps are modeled.

If the real amp doesn't have one or more of these controls, like a Mid knob, leave it at the default (Mid: noon).

See [[Amp_block#Authentic or idealized models| Authentic or Idealized models]] for more information about these controls.

Fractal Audio Explains:

<blockquote>
"Setting bass and treble to zero on a passive tone stack tells you nothing about the response of the midrange control. On a Fender setting bass and treble to zero turns the midrange into a volume control. On a Marshall it turns it into some weird highshelf/lowpass thingy. A passive tonestack is a very different animal than active tone controls with well-behaved frequencies. Download and play with Duncan's TSC to see the effects." [https://www.thegearpage.net/board/index.php?threads/ir-properties.2047238/page-43#post-28717398]
</blockquote>

==HIGH TREBLE==

This parameter is named HIGH TREBLE in firmware Ares and later.

This was previously called the "Bright" knob.

From the Owners Manual:

<blockquote>
“Think of this as an extra tone control, useful to add “zing” or tame harsh highs.”
</blockquote>

It's a shelving filter between the preamp and power amp and can be used to darken or brighten the output of the preamp. It replicates the “Presence” control in the Mesa Triaxis preamp when set to negative values (the Presence control in the Triaxis is a high frequency cut shelving filter).

Do not confuse this with the [[#BRIGHT|Bright]] switch (see above).

Fractal Audio Explains:

<blockquote>
"The Bright Knob is an active fourth tone control at high frequencies. Think of it as "High Treble". You can use it to add a little zing to a preset or remove harsh high frequencies. You can also use it to simulate the behavior of the Presence control on a Triaxis (which is really just a high cut). Turn it down to simulate "Presence" settings less than 10." [http://forum.fractalaudio.com/threads/always-look-on-the-bright-side-of-life.110008/#post-1317029]
</blockquote>

==PRESENCE + HIGH CUT==

From the Owners Manual:

<blockquote>
“Boosts (or cuts) the upper frequencies from the virtual power amp by varying the negative feedback frequency response. Increased presence can help a sound cut through. Note that settings for Presence don’t necessarily correspond to knob positions on the amp being modeled."
</blockquote>

Presence is a high-frequency tone control for the power amp section. It boosts (or cuts) the upper frequencies from the virtual power amp by varying the negative feedback frequency response.

Amps with no negative feedback circuits in their design cannot utilize a realistic presence control. Therefore, if Negative Feedback is set (manually or automatically) to “0”, Presence won't do anything anymore (in "Cygnus" amp modeling firmware).

If Power Amp Modeling is turned off, Presence is disabled (Quantum 9.03 and later). Before Quantum 9.03, Presence turned into a shelving filter when power amp modeling was disabled.

The range (min/max) of the Presence knob in the model is the same as the range of the real Presence knob on the modeled amp.

In some USA amps (Mesa Boogie), the Presence knob can be engaged to enable the "Presence Shift" function. And in the USA Pre model, there are separate Presence controls for the preamp and the power amp.

Cygnus amp modeling: the Presence control in the Amp block now behaves like the actual amp rather than an idealized version. The Presence Frequency parameter is now a frequency multiplier rather than an absolute frequency as the frequency of the presence circuit depends on the Presence control position. The Presence Frequency parameter works by scaling the value of the virtual presence circuit’s capacitor value. Setting the Pres/Depth Type parameter to Active or Active Pres will override the authentic modeling and implement an ideal presence circuit with fixed center frequency.

Presence control is set to a default value when an amp model is selected. This is done because many amps, i.e. Double Verb, Deluxe Verb, et. al., have no presence control and the value should be set to zero for best accuracy. On the other hand some amps, i.e. Jr. Blues, 65 Bassman, et. al, have fixed presence networks. The Presence control will default to the appropriate value for these amps. For amps that do have a presence control, the Presence parameter will default to a value that is deemed typical for the model.

Fractal Audio Explains:

<blockquote>
"The Axe-Fx II presence operates just like a real amp and modifies the virtual power amp feedback. This actually does create a sort of "magic" since it changes the shape of the distortion vs. frequency. That's the advantage to the nonlinear feedback network that the Axe-Fx uses. Negative feedback makes the distortion transfer function "harder". The presence control reduces negative feedback at high frequencies. This increases the treble but also softens the transfer function so you get more highs but the softer distortion reduces the amount of harsh overtones." [http://forum.fractalaudio.com/threads/slo-100-models-on-axefx-and-amplitube.85267/#post-1033870]
</blockquote>

<blockquote>
"The effect of Presence and Depth is consistent with the behavior of the real amp and depends on the amount of negative feedback. As you decrease negative feedback the presence and depth controls have less effect (as in a real amp). Also, as you increase Master Volume the presence and depth may appear to be less effective (key word is "appear") as the power amp distorts more and this masks the effect of the controls." [http://forum.fractalaudio.com/threads/may-be-stupid-questions-on-fw15.87420/#post-1058088]
</blockquote>

<blockquote>
"A tube amp's presence control is basically a type of treble control. It affects a higher range of frequencies and operates on a different principle but the net effect is an increase in high frequencies. There is also a slight increase in distortion in the higher frequencies since the power amp becomes less linear for those frequencies".
</blockquote>

<blockquote>
"HiCut is dependent upon Damping, just like a real amp. Hi Cut is modeling the Miller capacitance at the input to the Phase Inverter. The more negative feedback, the less the Miller capacitance." [http://forum.fractalaudio.com/threads/adv-hi-cut.47260/#post-615856]
</blockquote>

<blockquote>
(before Cygnus amp modeling) "Presence and Depth controls may not match the taper of the actual amp. On most amps the Presence control does nothing until you turn it almost all the way up. This seems a bit silly so we make the Presence behave more logically. Same goes for the Depth control." [http://forum.fractalaudio.com/threads/new-18-00-public-beta.96570/page-7#post-1158815]
</blockquote>

<blockquote>
(before Cygnus amp modeling) [http://www.fractalaudio.com/downloads/manuals/axe-fx-2/Fractal-Audio-Systems-MIMIC-(tm)-Technology.pdf MIMIC whitepaper]: "Note however that the taper of the presence (and depth) control can deviate from the actual amp. In our tests we found that the presence control on many amps did nothing for the first 80% of its rotation and all the action occurred in the last 20%. We feel that this design anomaly is undesirable and therefore did not model that aspect."
</blockquote>

<blockquote>
(Axe-Fx II) "Improved Amp block feedback network accuracy especially for those amps that have depth networks. This causes the Presence and Depth controls to interact (as they would on a real amp) but yields greater realism."
</blockquote>

<blockquote>
(before Cygnus amp modeling) "The Presence control on the Axe-Fx is more linear. The Presence control on most amps does nothing for the first half of its rotation or more. I made it so the Presence control actually does something when you turn it. Therefore you typically need to set the Presence control lower than you would on the amp."
</blockquote>

<blockquote>
(before Cygnus amp modeling) "Most of the controls in the Axe-Fx match their physical counterparts. The exceptions are Presence and Master Volume. Most amps simply have the wrong taper for their Presence controls. For example a 5150 Presence control does absolutely nothing from 0 to 7. All the action happens in the upper 1/4 of the control's range which is just dumb. The Axe-Fx uses a proper taper which gives a nice, even response over the full range of the control. Likewise the Master Volume on many amps is too abrupt. By 2-3 on the knob the power amp is saturating. Again we use a more rational taper so that you have finer control over power amp distortion. The downside of this approach is that if you put the Presence and Master Volume controls in the same position as the amp it won't sound the same. People do this then post videos and proclaim "See? Modeling isn't accurate!!! Toobz rule brah."" [https://forum.fractalaudio.com/threads/legacy-amp-models-consider-revisiting-full-honest-request-and-opinion.160349/post-1920107]
</blockquote>

<blockquote>
"A 5150's presence control has almost no effect from 0 to 7. After 7 the treble increases rapidly. The taper of the presence control in a 5150 is a log30 IIRC (maybe log10, I'd have to check my notes). If anything it should be linear. Ideally it should be reverse log. Our model uses a reverse log taper which gives a nice, smooth response over the full range. In most cases a reverse log taper would be the ideal taper. However reverse log taper pots are uncommon, difficult to source and cost more. Why they chose a log taper in the 5150 is a mystery. Since the power amp has similarities to a Marshall perhaps Eddie wanted the presence control to behave like his old Marshalls. Another possibility is the designer felt the amp was too bright with all knobs at noon (and a linear taper presence pot) and changed the taper to reduce the brightness." [https://www.thegearpage.net/board/index.php?threads/blind-test-mesa-dual-rectifier-vs-mystery-modeler-update-results-revealed.2208367/post-31639265]
</blockquote>

<blockquote>
(firmware 23.05) "Changed Presence control taper on all 6160 and 5153 amp models to replicate the actual amp. It is advised to audition any presets that use these models and adjust accordingly."</blockquote>

==DEPTH==

From the Owners Manual:

<blockquote>
“Boosts low frequencies from the virtual power amp by varying the negative feedback frequency response. It is set by default to an appropriate value when the amp type is selected, but this setting may be overridden.”
</blockquote>

Operates the same as Presence (see above) but it handles the low frequencies.

Like Presence, Depth is disabled if Power Amp modeling is disabled.

Fractal Audio explains:

<blockquote>
"Excursion = Depth. Manufacturers like to give this control fancy names (Excursion, Whomp, Resonance, etc., etc.) but it's just a Depth control." [https://forum.fractalaudio.com/threads/who-sold-a-bogner-ecstasy-amp-for-axe-fx-ii.101766/#post-1220413]
</blockquote>

<blockquote>
"Depth = Resonance = "Whomp" = whatever colloquialism the manufacturer can think of. Depth differs from Bass in that it is applied in the power amp as opposed to the preamp. It is done by modifying the feedback network. Less lows are fed back thereby increasing bass response in the power amp. It is analogous to Presence except it affect bass instead of treble. If you look at the Axe-Fx II's menu you'll see the tab says "PWR AMP" thereby indicating it is a power amp control." [http://forum.fractalaudio.com/threads/amp-5150-depth-control-what-is-it.79186/#post-963090]
</blockquote>

<blockquote>
"Many amps have no depth circuit, e.g. Fenders, most Marshalls, and generally most older designs. In these cases the Depth knob will default to zero indicating the amp has no depth circuit. Some amps have a fixed depth circuit, e.g. 5153, Freidman BE/HBE, Dirty Shirley, TripTik, Tucana, et. al. In these cases the Depth knob will default to a value that corresponds to the fixed circuit. Finally some amps have a variable depth circuit, e.g. 5150, Diezel, et. al. In these cases the Depth knob defaults to a non-zero value that I think sounds good but that's just my taste. The choice of IR and the monitoring system can greatly influence the amount of perceived bass. The desired amount of bass is a preference. If you are into "classic" tones then a Depth of zero would be a logical choice." [http://forum.fractalaudio.com/threads/lets-talk-about-the-depth-control.88747/#post-1071598]
</blockquote>

<blockquote>
"Depth does not work at a Damping of 0 since Depth modifies the feedback and there is no feedback." [http://forum.fractalaudio.com/threads/damping.59333/#post-740665]
</blockquote>

<blockquote>
"The effect of the Presence and Depth is consistent with the behavior of the real amp and depends on the amount of negative feedback. As you decrease negative feedback the presence and depth controls have less effect (as in a real amp). Also, as you increase Master Volume the presence and depth may appear to be less effective (key word is "appear") as the power amp distorts more and this masks the effect of the controls." [http://forum.fractalaudio.com/threads/may-be-stupid-questions-on-fw15.87420/#post-1058088]
</blockquote>

<blockquote>
"I look at the Depth knob as a starting point. Just because the 5153 has a fixed depth circuit doesn't mean you can't adjust the knob. The only reason that it is fixed on that amp is there wasn't enough room to put in separate knobs for each channel. The 50W version has an adjustable Depth (it's called resonance and the knob is on the back). The original 5150 had adjustable Depth. The designers choice isn't necessarily best. It depends on the cabinet (or IR) and your personal preferences. Short answer: use your ears. I think too many people are scared to use their ears. But if you constantly rely on the ears of others you'll never learn how to create your own signature sound." [http://forum.fractalaudio.com/threads/lets-talk-about-the-depth-control.88747/#post-1071786]
</blockquote>

<blockquote>
(before Cygnus amp modeling) "Presence and Depth controls may not match the taper of the actual amp. On most amps the Presence control does nothing until you turn it almost all the way up. This seems a bit silly so we make the Presence behave more logically. Same goes for the Depth control." [http://forum.fractalaudio.com/threads/new-18-00-public-beta.96570/page-7#post-1158815]
</blockquote>

<blockquote>
(before Cygnus amp modeling) [http://www.fractalaudio.com/downloads/manuals/axe-fx-2/Fractal-Audio-Systems-MIMIC-(tm)-Technology.pdf MIMIC whitepaper]: "Note however that the taper of the presence (and depth) control can deviate from the actual amp. In our tests we found that the presence control on many amps did nothing for the first 80% of its rotation and all the action occurred in the last 20%. We feel that this design anomaly is undesirable and therefore did not model that aspect."
</blockquote>

<blockquote>
(Axe-Fx II) "Improved Amp block feedback network accuracy especially for those amps that have depth networks. This causes the Presence and Depth controls to interact (as they would on a real amp) but yields greater realism."
</blockquote>

<blockquote>
"Depth is dependent upon the speaker load. If your load doesn't match the internal speaker impedance curve exactly the response will be different. When I'm testing amps I have a special speaker impedance curve I use that is derived from the particular LB-2 that I use. The curve included in the firmware is a typical LB-2 response. Due to component tolerances the resonant frequency and magnitude can vary as much as 20%. Furthermore with the depth all the way up it is easy to start overdriving the power amp in the bass range. Again, due to pot tolerances the amp may be overdriving more or less than the model for a given MV setting. I should add that Depth is also dependent upon the open-loop gain of the power amp which, in turn, is dependent upon the transconductance and bias point of the power tubes. Therefore different power tubes and bias point will also affect the amount of low-frequency boost." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-00-release-candidate-2-beta-8.188778/post-2342487]
</blockquote>

==CUT==

From the Owners Manual:

<blockquote>
“Reduces the amount of low frequencies coming into the amp simulation. This can be used to achieve a “tighter” tone or to reduce low-end “flub”.”
</blockquote>

It is a first-order shelving filter (high-pass) at the input of the Amp block. This can be used to achieve a “tighter” tone and to reduce low-end “flub”. It defaults to 120 Hz. The frequency can be adjusted through the Low Cut Frequency parameter.

Note: Cut is the same as increasing Low Cut on the Input EQ page (see below).

Fractal Audio explains:
<blockquote>
"You can use a Filter block before the Amp set to Shelving if you want to add more flexibility to what the Cut switch is doing in the Amp block." [http://forum.fractalaudio.com/threads/new-cut-parameter.72470/#post-887770]
</blockquote>

<blockquote>
"120 Hz is where most amp designers put it. A typical cathode bypass has the pole at approx. 85 Hz. Assuming 6 dB gain reduction that puts the center frequency at 120 Hz." [http://forum.fractalaudio.com/threads/new-cut-parameter.72470/#post-887765]
</blockquote>

<blockquote>
"The bass cut switch is before the distortion so it will change the feel and breakup characteristics. The bass cut is basically intended to give you that Tube Screamer with Drive on 0 sound without having to use a dedicated Drive block." [http://forum.fractalaudio.com/threads/hi-cut-cab-bass-cut-amp-overkill.74445/#post-910785]
</blockquote>

<blockquote>
"Cut engages a lowshelf filter at the input. This would be analogous to partially bypassing the input buffer cathode on a tube amp." [http://forum.fractalaudio.com/threads/controlling-the-lows.96327/#post-1154831]
</blockquote>

==FAT==
From the Owners Manual:

<blockquote>
“Emphasizes midrange and adds “body” by shifting the tonestack center frequency.”
</blockquote>

This is similar to the FAT switch on a Mesa Boogie, which is a popular control for lead tones because it adds body to the tone.

Fractal Audio explains:
<blockquote>
"The Fat switch simply alters the tone stack treble capacitor. So the effect depends on the location of the tone stack." [http://forum.fractalaudio.com/threads/national-enquirer-fractal-fatswitch-fiasco.51361/#post-660652]
</blockquote>

<blockquote>
"The Fat Switch multiplies the tone stack treble cap by four. Depending upon the type of tone stack, tone control settings, position, etc., etc. the effect can be more or less noticeable." [http://forum.fractalaudio.com/threads/fat-switch.76310/#post-932073]
</blockquote>

<blockquote>
"The Fat switch changes a value in the tone stack which changes the response of the stack, shifting the mid dip down and making it less pronounced. The Tonestack Freq. parameter frequency scales all the reactive components in the tone stack which is something quite different." [http://forum.fractalaudio.com/threads/fat-switch-is-totally-different-than-axe-fx-ll.145247/page-2#post-1718101]
</blockquote>

==BRIGHT==
From the Owners Manual:

<blockquote>
“Many amplifiers contain a “treble peaker,” included as a pull or toggle switch, or even hard- wired. Each amp type includes this control (even if the original mode does not). The effect may be subtle or quite pronounced depending on the amp type. This is also affected by the Bright Cap setting. If the original amp had no bright circuit, Bright is OFF by default but can still be turned on to apply circuit values suited to an amp of that general type. If the amp has a hard-wired treble peaker, the default state is ON.”
</blockquote>

The Bright ''switch'' is not to be confused with the BRIGHT ''knob'' (Axe-Fx III, FM9 and FM3: High Treble) which is a shelving filter between the preamp and power amp (see below).

The Bright switch is either:
* the virtual equivalent of a bright switch (pull or toggle) on the real amp.
* the virtual equivalent of a bright cap on the volume or gain control of a real amp.
* the virtual equivalent of a hard-wired bright switch inside the amp.
* a method to change to the Bright channel of the original amp (if the original amp has a Normal and a Bright channel/input, and only the Normal channel/input has been modeled).

Bright caps are used to compensate for guitars with weak pickup loads, increasing treble as gain is decreased. It also changes the mids, which affects gain too.

If the modeled amp has a hard-wired treble peaker, the default state of the virtual Bright switch is ON.

Turning up the amp's Drive or Master may decrease the impact of the Bright switch, depending on the amp type.

The effect of the Bright switch on the tone can be controlled through the Bright Cap value parameter.

Some amp types, such as a Plexi, have a very high Bright Cap value, which has a large impact on the amount of gain.

Fractal Audio explains:
<blockquote>
"If an amp doesn't have a bright switch, the operation of of the models' bright switch is undefined. I chose what I considered a reasonable value for the bright cap but if that doesn't satisfy the user then they are free to change it to a different value." [http://forum.fractalaudio.com/threads/vh4-amps-bright-switch.70382/page-2#post-865222]
</blockquote>

<blockquote>
"The Bright switch always controls the bright cap on the input volume." [http://forum.fractalaudio.com/threads/any-way-to-disable-bright-cap-on-dumble.74295/#post-909499]
</blockquote>

<blockquote>
"The Bright switch switches in/out one or more capacitors on the Input Drive network." [http://forum.fractalaudio.com/threads/always-look-on-the-bright-side-of-life.110008/#post-1317029]
</blockquote>

<blockquote>
"The Bright Switch models the "bright cap" across the drive/gain/volume/comodjulator pot. Some amps have no bright cap, some amps have a hardwired bright cap and some amps give you a switch to turn it on/off. A bright cap increases treble as the pot is turned down. The original impetus for this was that guitars with weak pickups tend to be brighter and guitars with hot pickups tend to be darker. So you're likely to turn the gain up for the guitar with weak pickups which reduces treble response. On the guitar with hot pickups you're likely to turn the gain down which increases treble response to counteract the darker tone. If the amp has no bright cap the Bright Switch defaults to off. If the amp has a hardwired cap the switch defaults to on. If the amp has a switch it defaults to whatever we felt sounds the best. Our particular JCM800 reference amp has no bright cap because someone removed it. However the model has the switch on because that's the way the amp would've come from the factory. There are actually 11 different (IIRC) bright cap models in the Axe-Fx/AX-8. The earliest bright cap circuits were just a cap from the input terminal to the wiper. Over time designers have developed more complex circuits with resistors in series with the cap, another cap from the wiper to ground, treble peakers before/after the pot, etc. The user doesn't have the ability to select the model though, it is hard-coded into each model." [http://forum.fractalaudio.com/threads/fractal-vs-helix-let-the-comparisons-begin-video-series.119390/page-2#post-1423491]
</blockquote>

<blockquote>
"Those amps have a "bright switch" that is permanently on but there is no physical switch on the actual amp. The capacitor is hard-wired." [http://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-4-00-beta.148349/page-15#post-1756141]
</blockquote>

==BRIGHT CAP==

From the Owners Manual:
<blockquote>
“Sets the value of a virtual capacitor to determine the sonic effect of the Bright switch. Increasing this will make the preamp brighter and vice versa.“
</blockquote>

Fractal Audio explains:
<blockquote>
"That's one of my go-to tweaks. The amount of treble peaking needed for an amp at a given drive is highly dependent on the guitar. For example my guess is that the AFD100 was designed around a Les Paul. With my Suhr it's much too bright because that's a very bright guitar. So one of the first things I do with the AFS100 model is turn down the bright cap a bit." [http://forum.fractalaudio.com/threads/firmware-1-11.140004/page-2#post-1660177]
</blockquote>

<blockquote>
"Input Trim at 0.5 is equivalent to using the Low input jack on amps. If you are using high-output pickups it's often better to use the Low input to get into the sweet spot of the bright cap." [https://forum.fractalaudio.com/threads/the-modeler-equivalent-to-alternate-guitar-tunings.155649/post-1853194]
</blockquote>

==MASTER VOLUME TRIM==
From the Owners Manual:

<blockquote>
"Allows you to adjust the range of Master Volume. Increasing the value above 1.0 will cause more gain in the virtual power amp and vice versa."
</blockquote>

=Preamp=

==INPUT BOOST + TYPE + LEVEL==

From the Owners Manual:
<blockquote>"Acts as a “clean boost,” replicating the common technique of driving an amp harder by using a drive pedal with the “Drive” knob at 0 and the “Level” turned up. To use the boost, turn the switch on, choose the boost type (types are based on real pedals, each with its own EQ/color) and set the Boost Level as desired.

The Boost switch can be operated with a Modifier. These controls provide a way to give an amp model more gain without the CPU overhead of adding a drive block."</blockquote>

Increases the signal level at the input section of the Amp block.

'''AX8''' and '''Axe-Fx II''' — Boost is fixed at 12 dB.

'''Axe-Fx III''' and '''FM3''' and '''FM9''' — You can choose between many different [[#Input boost types|input boost types]]. These all act as clean boosts, replicating the oft-used “Drive on 0, adjust Level as desired” boost technique. This allows boosting the Amp block without requiring a separate Drive block. The difference between the various types is the EQ (frequency response) of each model. The Boost Level parameter sets the amount of boost. Using an input boost instead of a separate Drive bock saves CPU.

The gain range of the Input Boost has been increased in firmware Cygnus 16 and later.

Input 1 Gain (global parameter on the Axe-Fx III and FM9) and Input Trim in the Amp block have a similar function.

The Input Boost types are:

* '''AC Boost'''
* '''CC Boost''': "CC boost is based on ... nothing. I took a PEQ one day and was using at a boost. At one point I got something that sounded really good to me so I made it into a boost." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-6-04.152296/post-1812168]
* '''FAS Boost'''
* '''Full OD'''
* '''Grinder''': based on Fortin's Grind pedal. It incorporates Fortin's favorite 6IRTH and 6RIND settings. This type is not available as a type in the Drive block.
* '''JP IIC+ Shred''': replicates the “Shred” switch on the Mesa/Boogie JP2C.
* '''Mid Boost'''
* '''Neutral''': This is the default boost type. (Same as AX8 and Axe-Fx II).
* '''RCB Boost'''
* '''Shimmer'''
* '''Shred Boost''': A clean boost on the input similar to a Tube Screamer but without the treble roll-off (copied from the USA JP IIC+ Shred models).
* '''Super OD'''
* '''T808'''
* '''T808 Mod'''
* '''Treble Booster'''

See [[Drive block]] for more information about these types.

Fractal Audio explains:

<blockquote>
"The changes to the modeling of drives in firmware Ares 3.02 and later do not apply to these input boost types." [http://forum.fractalaudio.com/threads/faith-restored-in-my-axe.147281/page-3#post-1741111]
</blockquote>

<blockquote>
"The amp boosts are just the frequency shaping part of the drive. The clipping stuff is removed. It's analogous to turning the Drive knob all the way down and using the pedal as a clean boost." [http://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-3-02-public-beta.147926/page-11#post-1751115]
</blockquote>

==SATURATION + SATURATION DRIVE==

From the Owner's Manual:
<blockquote>“This engages a popular mod between the preamp and the tonestack for a thicker, more aggressive distortion character. “IDEAL” gives you the hotter output you wish a real amp had with saturation engaged.” “Saturation Drive controls the amount of saturation (see above). The default value differs for each mode.”</blockquote>

This is the virtual equivalent of Jose Arredondo’s famous Marshall amplifier modifications.

Enabling it decreases power amp smoothing, resulting in meaner distortion. This switch is enabled at default in certain models. Also try it with amp types such as JCM800, Friedman and Mesa Mark. With amp models that have no preamp gain, such as Plexis, saturation has no effect.

There are two types: AUTH and IDEAL. IDEAL pushes the virtual power amp harder which changes the tone.

<blockquote>(Axe-Fx II) "Amp block Sat Switch now has three settings: Off, On (Auth) and On (Ideal). On (Auth) replicates authentic saturation circuit behavior and will lower the volume out of the virtual preamp. On (Ideal) replicates the idealized behavior present in Version 14.xx and earlier firmware."</blockquote>

Fractal Audio explains:

<blockquote>"It switches in a zener diode clipping stage right before the tone stack. This is the so-called Jose Arrendondo Mod." [http://forum.fractalaudio.com/threads/axe-fx-ii-technical-questions-thread.35997/page-38#post-494304]</blockquote>

<blockquote>"The Sat (saturation) circuit is located between the preamp and power amp. If the model doesn't have much preamp gain, e.g. 59 Bassguy, then the sat switch will have little effect. A real amp would exhibit the same behavior. Amps like this get all their distortion from the power amp." [http://forum.fractalaudio.com/threads/may-be-stupid-questions-on-fw15.87420/#post-1058088]</blockquote>

<blockquote>"Sat switch works on all amps. However if an amp is getting its distortion from the power amp, i.e. Plexis, etc., then the affect may not be noticeable since the power amp distortion will mask any distortion occurring prior. Sat switches are typically employed on amps with master volumes for just this reason." [http://forum.fractalaudio.com/threads/saturation-switch-does-nothing-on-authentic-for-most-amps-not-g3-yet-maybe.104357/#post-1248576]</blockquote>

<blockquote>"It always works. If you turn down the MV its affects may be more noticeable. Be aware that a Plexi has low preamp gain and you may need to set Sat Drive quite high to get any saturation. The classic "Arredondo mod" involves adding a "saturation circuit" and a master volume as the sat circuit's affects are masked if the power amp is heavily distorted." [http://forum.fractalaudio.com/threads/saturation-switch-does-nothing-on-authentic-for-most-amps-not-g3-yet-maybe.104357/#post-1248582]</blockquote>

<blockquote>"The sat switch is located at the output of the preamp. If the distortion is coming from the power amp, i.e. a Plexi, then the effect is not very audible in Authentic mode (just as it would in a real amp)." [http://forum.fractalaudio.com/threads/0-3-sat-switch-on-has-no-audible-effect.132963/#post-1574314] </blockquote>

<blockquote>"The ideal setting will push the power amp harder which WILL change the tone." [https://forum.fractalaudio.com/threads/saturation-switch-changes-tone.161328/post-1931505]</blockquote>

==PREAMP TUBE TYPE==

From the Owner's Manual:

<Blockquote>
"Changes the characteristics of the virtual preamp tubes, based on real world examples."
</blockquote>

<blockquote>
"New RTS triode models. There are three new triode models based on our new algorithms: 12AX7A (default), ECC83 and 7025. The previous models are still available and may be selected with the Pre Tube Type parameter."
</blockquote>

<blockquote>
"Further improvement of preamp tube models based on measurements. The existing theoretical models, i.e. “Modern”, “Vintage”, etc., have been removed. There are now six extremely accurate preamp tube types: 12AX7A, ECC83, 7025, 12AX7B, ECC803 and EF86. Note that the EF86 type has been normalized to have roughly the same gain as the triode types."
</blockquote>

<blockquote>
"Updated all models to use an appropriate Preamp Tube Type when selected. I.e. British models will now use the ECC83 when selected."
</blockquote>

From the Axe-Fx II manual:

<blockquote>
"“Modern” (default) selects a triode characteristic representative of modern production tubes. “Vintage” selects a characteristic typical of tubes produced in the 50’s and 60’s. “Long Plate” replicates the softer saturation characteristic of so-called “Long Plate” triodes."
</blockquote>

<blockquote>
"There are now only two Preamp Tube Type options in the Amp block: Short Plate and Long Plate. The Vintage type has been removed. Short Plate is similar to the previous Modern model but has the improved saturation characteristics that were developed for the Long Plate model."
</blockquote>

<blockquote>
"There are now four Preamp Tube Types:
* Short Plate: an accurate model of a modern “short plate” production 12AX7.
* Long Plate: an accurate model of a classic “long plate” 12AX7.
* Modern: An idealized 12AX7 model. This is the same model from version 18.04 firmware. This model is useful for high gain tones that can benefit from the increased clarity and string separation.
* Vintage: Another idealized 12AX7 model also from version 18.04 firmware. Has a softer breakup than the Modern model. Useful for “vintage” tones where more base nonlinearity is present."
</blockquote>

<blockquote>
"The preamp modeling in 6.00 is the same as 5.xx except the parameters for the default tube type (12AX7A SYL) are different. The Sylvania 12AX7A is more nonlinear than other 12AX7As which results in more dynamics but will also result in more "background" distortion because the waveform is being distorted even when it isn't being clipped. The JJ version is more linear which will result in a tighter tone and less background distortion but less dynamics. For 6.01 I've also added back the old 12AX7B type which is the most linear of the types and clips hard. People who play with lots of gain tend to like this as it results in tighter tone and more aggressive harmonic content. There are two primary parameters associated with our preamp tube models. "Preamp Hardness" determines how abrupt the tube clips when it enters the saturation region. There is another parameter that determines how nonlinear the tube is between cutoff and saturation. This is currently not exposed to the user but I've been contemplating adding it. I've also changed the default type for British amps to the ECC83 model as these amps typically were equipped with ECC83s (duh). The ECC83 was the European equivalent of the 12AX7A and tended to be a bit more linear and clip a little harder." [http://forum.fractalaudio.com/threads/anyone-not-a-fan-of-quantum-6.121353/page-3#post-1446007]
</blockquote>

Fractal Audio explains:
<blockquote>
"The primary controls to adjust the saturation behavior are Preamp Tube Type, Preamp Hardness and Preamp Bias." [http://forum.fractalaudio.com/threads/suggestions-on-what-youve-done-to-enjoy-18-03.97925/page-9#post-1178319]
</blockquote>

<blockquote>
"The parameters for the 12AX7 were extracted from an RCA 12AX7A. The ECC83 was a Mullard." [http://forum.fractalaudio.com/threads/if-12ax7-and-ecc83-are-the-same.110515/#post-1323322]
</blockquote>

<blockquote>
"The 7025 was a Sylvania." [http://forum.fractalaudio.com/threads/if-12ax7-and-ecc83-are-the-same.110515/#post-1323463]
</blockquote>

<blockquote>
"People claim that preamp tubes sound different. They have no sound. They might have different characteristics though which cause the CIRCUIT to sound different. They might have more or less gain, or more or less capacitance, etc. It's such a crap-shoot though. Switching around tubes until you believe it sounds better. I prefer a more scientific approach. What are you trying to achieve? Okay, then lets reduce this coupling capacitor a bit." [https://forum.fractalaudio.com/threads/why-power-tubes-sound-different.79962/page-2#post-972959]
</blockquote>

==LOW CUT FREQUENCY==

This parameter sets the frequency of the [[#CUT|Cut]] switch (see above).

<blockquote>"In some models the low cut is exposed to the user. For example, take the ODS-100 HRM model. In that amp there is a 390pF cap between the input buffer and the gain control. The highpass frequency is constant at 355 Hz. In this model that value is exposed to the user so they can adjust it as desired. It is common in D-style amps to tweak this value. Therefore the low-cut frequency has been exposed to the user. In some amps, however, there is no coupling capacitor. For example, in a Deluxe Reverb the input buffer connects directly to the tone stack. In this model, therefore, the low-cut is defeated. In other models the coupling capacitor interacts with the tone stack or the gain control and is therefore not a static value and, as such, is handled separately and not exposed to the user. For example, if a Deluxe Reverb had a coupling capacitor between the input buffer and the tone stack the low-cut frequency would be dependent upon the position of the tone controls. In this case the coupling capacitor would be handled separately and not exposed as a static frequency. Actually in this case that capacitor would be considered part of the tone stack and the network solved accordingly." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-23-03-beta-1.199704/page-20#post-2490702]</blockquote>

==HIGH CUT FREQUENCY==
From the Owners Manual:
<blockquote>
"This filters the highs at the very end of the preamp simulation. Experiment with this to fine-tune your tone. For example, some of the higher gain amp types are characterized by fairly heavy filtering after the preamp stage. Increase for a brighter tone or decrease for a darker tone."
</blockquote>

High Cut Frequency adjusts the cutoff frequency of a low-pass filter. This filter is placed between the virtual preamp and power amp, so it has a more dramatic effect than an EQ that might be placed before preamp distortion. It will cut off all frequencies above the specified value. It ranges from 2000-40000Hz.

This parameter is different from High Cut on the Input EQ page.

Fractal Audio explains:
<blockquote>(Quantum 3.00) "It's probably inaudible but there were a few amp models where the matching was indicating a loss of high-frequency response. This was traced to the high-cut filter. When the high-cut frequency is 20 kHz that means the response is 3 dB down at 20 kHz so you've still got some slight attenuation at, say, 15 kHz. So for the sake or accuracy it now goes to 40 kHz which pushes that pole well outside the audible range." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-3-00-public-beta-2.113734/page-3#post-1360576] </blockquote>

<blockquote>"The high cut frequency is due to the snubber cap in the PI. Friedman's use 100 pF (or more) for the snubber cap. A DSL only uses 47 pF so, yes, you would need to double the high cut frequency to match." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-05.149428/page-6#post-1773457]</blockquote>

<blockquote>"A snubber is a network used to reduce high frequencies. The term is a bit misused in tube amps. Typically a snubber is used to absorb transients in power circuits (like when a switch opens/closes). In a tube amp the "snubber cap" is a capacitor across the plates of the phase inverter (PI). This reduces the gain of the power amp at high frequencies. It was originally used to prevent the power amp from oscillating. Some modern amps employ large values for tone shaping." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-05.149428/page-6#post-1773475]</blockquote>

==PREAMP SAG==

From the Owners Manual:
<blockquote>
"Turning this ON causes the amp block to behave like an integrated tube head or combo amp. Turning this OFF simulates a separate preamp and power amp."
</blockquote>

==PREAMP TUBE HARDNESS==

Previously called: TRIODE HARDNESS (before firmware Cygnus 16 for the Axe-Fx II). [http://forum.fractalaudio.com/axe-fx-ii-discussion/91241-triode-hardness.html#post1098468]

From the Owners Manual:
<blockquote>
"This parameter controls how sharply the triodes enter saturation and can be used to simulate softer or harder tubes. The lower the value the softer the distortion. Higher values will cause the overtone series to have a less steep decay and will increase perceived “sparkle”. Use this control with Preamp Bias to control how chimey and “round” the tone is."
</blockquote>

The default value is 5.0 and is set to this value whenever the type is changed. The effect of this is subtle and most apparent at edge of breakup. Lower values give softer saturation, higher values give a more aggressive breakup.

Fractal Audio explains:

<blockquote>"What the parameter does now is control the asymmetry of the triode model. The higher the value, the more asymmetrical the clipping." [http://forum.fractalaudio.com/threads/v-10-triode-hardness.67091/#post-826849]</blockquote>

<blockquote>"Lower values will have less even and more odd harmonics. The smoothness/harshness of distortion is a function of the ratio of even to odd harmonics. The more symmetrical the clipping, the more odd and less even harmonics." [http://forum.fractalaudio.com/threads/v-10-triode-hardness.67091/#post-826877]</blockquote>

<blockquote>"The default hardness value is based on the tubes that were in the amp being modeled. Most tubes fall in the range of 8 to 9. Perhaps old Mullards or Gold Lions or whatever are softer and would be equivalent to 5 or less. I don't know, I've never tested any. In general lower values will sound softer (naturally) but have less note separation. Higher values will give a more aggressive distortion and better note separation. There are no rules. Adjust the value to your personal preference. I doubt a real tube would ever be able to get to a value of zero but that doesn't mean it isn't a useable sound." [http://forum.fractalaudio.com/threads/axe-fx-ii-firmware-v11-02-and-new-preset-banks.74402/page-4#post-910797]</blockquote>

<blockquote>"If you are right on the edge of breakup the triode hardness is very powerful as it controls the harmonic series. Higher values will cause the overtone series to have a less steep decay and will increase perceived "sparkle". Together with the preamp bias you can control how chimey and "round" the tone is (preamp bias effectively controls the ratio of even/odd harmonics)." [http://forum.fractalaudio.com/threads/more-gain-in-11-01.74457/#post-911002]</blockquote>

<blockquote>"Triode Hardness at zero gives a smoother distortion with reduced upper harmonics. However if you carefully compare a real tube preamp with the Axe-Fx models you'll clearly hear the difference as you reduce Triode Hardness. It's even more apparent when you compare the distortion spectrum. It's yet even more apparent when you use measurement techniques that learn the proper value." [http://forum.fractalaudio.com/threads/downgrading-to-fw9.76826/page-5#post-938344]</blockquote>

<blockquote>"The primary controls to adjust the saturation behavior are Preamp Tube Type, Preamp Hardness and Preamp Bias. (...) Preamp Hardness allows you to adjust how soft the saturation is." [http://forum.fractalaudio.com/threads/suggestions-on-what-youve-done-to-enjoy-18-03.97925/page-9#post-1178319]</blockquote>

<blockquote>"You can control the "shape" of the preamp and power amp distortion. The Preamp Hardness parameter controls the shape of the triode emulations. The lower the value the softer the distortion. The Power Amp Hardness controls the power amp clipping but that often is not noticeable because negative feedback around the power amp makes the distortion harder. Therefore you can make the power amp distortion softer by reducing Negative Feedback. A good example of this is a JCM800. A JCM800 has very hard preamp distortion (since there is no cathode bypass cap on the last stage) but has low negative feedback which softens the power amp distortion. The trick with that amp is to get the amp into the sweet spot by increasing the MV until you are getting some power amp distortion which softens the preamp distortion." [http://forum.fractalaudio.com/threads/scratchy-sound-on-this-patch-same-for-you.100622/page-2#post-1207496]</blockquote>

<blockquote>"There are two primary parameters associated with our preamp tube models. "Preamp Hardness" determines how abrupt the tube clips when it enters the saturation region. There is another parameter that determines how nonlinear the tube is between cutoff and saturation. This is currently not exposed to the user." [http://forum.fractalaudio.com/threads/anyone-not-a-fan-of-quantum-6.121353/page-3#post-1446007]</blockquote>

<blockquote>"0.00 is not symmetrical. In fact there is no value that is symmetrical." [http://forum.fractalaudio.com/threads/preamp-tube-type.122604/#post-1459051]</blockquote>

==TRIODE 1+2 PLATE FREQUENCY==

From the Owners Manual:
<blockquote>
"These parameters set the cutoff frequency of the last two triodes in the chain. Many amps have a capacitor across this triode’s plate resistor. This capacitor is used to smooth the response and reduce noise. You can adjust the amount of capacitance, and the resulting frequency, using these parameters."
</blockquote>

Fractal Audio explains:
<blockquote>
"It sets the cutoff frequency of the resistor/cap combination on the plate of the last triode stage (the previous stages are not user adjustable). Most amps have no cap on the last stage but a few do. You can vary this parameter to simulate increasing/decreasing the capacitor value. The frequency is only approximate since the actual frequency varies with the bias point/cathode impedance/drive/etc." [http://forum.fractalaudio.com/threads/amp-block-triode-plate-frequency.38144/#post-521777]
</blockquote>

<blockquote>
"This parameter sets the cutoff frequency of the plate impedance for the next-to-last triode in the chain. Many amps have a capacitor across this triode’s plate resistor. This capacitor is used to smooth the response and reduce noise. You can adjust the amount of capacitance, and the resulting frequency, using this parameter. The last triode plate capacitor is also exposed: Triode2 Plate Freq."
</blockquote>

==PREAMP BIAS==

From the Owners Manual:
<blockquote>“This adjusts the bias point of the last triode stage. This is the most important stage in the feel and texture of distortion, as it controls the ratio of even/odd harmonics. Values around zero will produce mostly odd harmonics. As you deviate from zero you’ll produce less odd and more even. Odd harmonics give clarity and a more aggressive, open tone but this can be cold and harsh. Adding even harmonics gives a warmer sound but too much and things can get muddy. Getting the right balance of even and odd harmonics is one of the keys to achieving “edge of breakup” tones.”
</blockquote>

Fractal Audio explains:
<blockquote>
"The further you move away from (roughly) zero the more even harmonics are introduced. It's an asymmetric transfer function, so you have to experiment." [http://forum.fractalaudio.com/threads/more-gain-in-11-01.74457/#post-911042]
</blockquote>

<blockquote>
"The primary controls to adjust the saturation behavior are Preamp Tube Type, Preamp Hardness and Preamp Bias. (...) Preamp Bias adjusts the bias point of the last triode stage which will control the ratio of even/odd harmonics. Values around zero will produce mostly odd harmonics. As you deviate from zero you'll produce less odd and more even." [http://forum.fractalaudio.com/threads/suggestions-on-what-youve-done-to-enjoy-18-03.97925/page-9#post-1178319]
</blockquote>

<blockquote>
"Bias points in an amp are important. The bias point of the last preamp stage is the most important. Therefore Quantum firmware exposes this bias point on the Pre Dyn tab as the Preamp Bias parameter. Most amps are biased slightly towards cutoff (negative). The closer you get to 0.0 the more odd harmonics and the fewer even harmonics. Experiment with this to craft your "Ultimate Tone" (TM, all rights reserved, use only as directed, these statements have not been evaluated by the FDA)." [https://forum.fractalaudio.com/threads/one-of-quantums-powerful-tools.104687]
</blockquote>

<blockquote>
"The Preamp Bias control in the Amp block controls the operating point of the last virtual triode stage in the preamp. This is the most important stage wrt to the feel and texture of distortion. The earlier stages are important but generally not nearly as much and the bias points are not exposed to the user. The operating point of a tube determines the symmetry of the clipping. If the tube is biased exactly halfway between the supply voltage and ground then it will clip symmetrically (greatly simplified). If the quiescent current is reduced the tube will biased more towards cutoff. If it is increased it will be biased more towards saturation. In general cutoff is smoother than saturation but it depends on the external circuitry. Negative values of Preamp Bias bias the virtual tube towards cutoff and positive values toward saturation. Symmetrical distortion has lots of odd harmonics and very little even harmonics. The more asymmetrical the distortion the more even harmonics are introduced. Odd harmonics give clarity and a more aggressive, open tone but this can be cold and harsh. Adding even harmonics gives a warmer sound but too much and things can get muddy. Getting the right balance of even and odd harmonics is one of the keys to achieving "edge of breakup" tones. Experiment with the bias point to find your optimum tone. Things get especially interesting when a cathode follower is involved. You can tell if an amp has a cathode follower if the Preamp Comp parameter is not zero. The cathode follower interacts with the last stage and slight adjustments to the bias point can cause major changes in the distortion characteristics. For example, the Dizzy Blue models are biased near zero (0.08 IIRC). If you play lightly you'll hear the bass is kind of stuffy and tubby. Reduce the Preamp Bias a bit and you'll hear the bass clean up. Too negative, however, and the sound can get indistinct. The good amp designers understand the interaction between the last stage and the cathode follower and tune the bias point for the desired distortion characteristics. The cathode follower is a bit of an imperfect design though. It's great for vintage Plexi and other high gain sounds but its clipping behavior is not ideally suited to certain tones. Therefore the Comp Type parameter allows you to choose an idealized cathode follower with different distortion characteristics (Comp Type == Ideal). Note that the behavior of this type is similar to the algorithms used in profiling modelers and other products. Try using the Ideal mode. You will likely need to reduce the amount of Preamp Comp as this mode has much more compression. Even amps that rely mostly on power amp distortion can benefit from fine tweaks to the Preamp Bias point. Shifting the bias point changes the harmonics into the power amp which changes the distortion character of the power amp (albeit less significantly)." [http://forum.fractalaudio.com/threads/preamp-bias.110726]
</blockquote>

<blockquote>
(firmware Ares 5.0) "The “Ideal” cathode follower type is no longer supported as it is incompatible and has been removed from the GUI."
</blockquote>

<blockquote>
"It's one of the main tools that amp designers use in voicing Marshall-style amps. For these amps you'll notice the amp gets tighter as you set Preamp Bias negative and chunkier for positive values. Too negative and things get thin and sputtery. Too positive and the lows get farty." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-5-02-firmware-released.120535/page-5#post-1434706]
</blockquote>

==PREAMP BIAS EXCURSION==

<blockquote>(Owners Manual) "Not to be confused with Bias Excursion on the Power Amp page, this is a separate parameter for the preamp. The higher the value, the more the bias shifts when the virtual tubes are overdriven."</blockquote>

Fractal Audio explains:
<blockquote>
"Bias Excursion is unrelated to the power supply stuff (sag, Variac, etc.).

Bias Excursion is grid bias shift caused by grid conduction. When a grid goes into forward conduction, charge "leaks" off the coupling capacitor. When the grid comes out of forward conduction the capacitor now has a net negative charge. This causes the bias point to shift negative.

Excessive bias excursion causes "blocking distortion".

Old amp designs, i.e. Fender 5E3 Tweed, exhibit copious bias excursion in the preamp and, hence, lots of blocking distortion. Part of its charm I suppose.

Power tubes also exhibit bias excursion. Some bias excursion in the power amp can be desirable. If you design the power amp in such a fashion so as the tubes go into forward conduction as the plates are clipping this will effectively reduce the bias and lower the gain causing the amp to "open up". To much bias excursion can cause excessive blocking distortion AND crossover distortion.

Designers can tailor the amount of bias excursion by adjusting the grid stopper resistor value."
[https://forum.fractalaudio.com/threads/rectifier-bias-excursion-time.179754/post-2194681]
</blockquote>

==TONESTACK TYPE + FREQUENCY + LOCATION==

The tonestack is the set of tone controls on an amplifier.

There are four main tone stacks used in most common guitar amplifiers: Marshall style, Fender style, Vox style, and the lesser used Baxandall or James style. These tone stacks vary in their construction, consisting of either a bass and treble control, or bass, mid, and treble controls. Some amplifiers have a tone stack consisting only of one control, usually a treble cut control, but sometimes it will be a single control that cuts treble at one end of the rotation, and cuts bass at the other end. These types of control are usually labeled "tone", or "cut". [http://www.aikenamps.com/index.php/a-glossary-of-common-amplifier-terms Source: Aiken]

'''Tonestack Type''' - it allows you to choose between various tonestacks.

<blockquote>(Owners Manual) “By default, the Bass, Mid and Treble controls operate as a “passive” tonestack: they simulate exactly the frequency and phase response of the classic passive tonestacks found in the original amplifiers many amp types are based on. This lets you change this behavior from “PASSIVE” to “ACTIVE”, or to substitute the passive tonestack of another amp.

Selecting a substitute tonestack allows you to mix and match amps and tone stacks to create your own hybrids. This allows you to use, for example, a Plexi-type tonestack on a Blackface amp model.

Selecting the “ACTIVE” type gives each tone control +/– 12 dB boost/cut operation for up to twice the range of a typical amplifier. Since the active tone controls are more sensitive, small adjustments have bigger effects. For example, full PASSIVE treble for a high-gain British amp would be equivalent to only +5.0 dB ACTIVE, leaving 7 dB of additional headroom! Active tone controls do not interact like those of a typical amplifier, so when you adjust the treble, the mid and bass are not affected. This can make dialing in a certain tone easier and quicker than it might be with a PASSIVE tonestack."

Selecting “Neutral” sets a well-behaved “hi-fi” kind of tone stack, where putting all the controls at noon will give you a flat response.

Selecting "Default" sets the default tone stack that comes with the flesh-and-blood amp.</blockquote>

'''Tonestack Freq''' - sets the center frequency of the tone controls to determine their effect on the sound. This control works whether you are using Active, Passive, or substitute tone stacks. This parameter defaults to an appropriate value whenever you change the amp TYPE, but it can then be changed as desired. But if you subsequently change the Tonestack Type, the Tonestack Frequency will not necessarily be correct anymore.

'''Tonestack Location''' - lets you change the location of the tone stack. “PRE” places the tone stack at the input to the virtual preamp, “POST” places the stack between the preamp and power amp. “MID” places it between the last two triode stages, and “END” places it after the power amp (which is physically impossible with a real amp).

<blockquote>(firmware 6) "Reworked most tone stacks based on amp matching results. In general most knobs now behave exactly like the actual amp when possible. In a few instances there may be minor discrepancies between the knob position of the model and actual amp due to programming constraints and/or peculiarities of the actual amp (such as poor potentiometer tolerance). Due to variations in presence circuit topologies the taper of the Presence parameter, in particular, may vary between the model and the actual amp. In other words, a different setting on the model may be required to achieve the same response as the actual amp. In most cases however, the Drive, Treble, Mid, and Bass knobs will be accurate to within 10% of the actual amp."</blockquote>

With some amp sims, such as the Lonestar, moving the tonestack location results in loss of volume.

<blockquote>"Whenever you set the bass and treble to zero the tone stack becomes basically "flat" and the mid becomes a volume control. Most tone stacks behave this way." [http://forum.fractalaudio.com/threads/interesting-find-eqs-at-zero-on-brit-pre-sounds-pretty-good.71226/#post-873182]</blockquote>

<blockquote>"Every amp model uses one of these tone stacks. Obviously as there are more models than tone stacks some models share tone stacks. If you set the Tone Stack Type to Default, the amp block will use the tone stack appropriate for that model. For example, the Plexi 50W models use the "Plexi" tone stack (not surprisingly). If you set the Type to Default then the selected tone stack will be the Plexi tone stack. If you set the Type to Plexi it will be the same tone stack. The reason I did it this way is so you don't have to remember what the default tone stack is for the model. Simply set the Type back to Default. BTW, the tone stack is one of the main things that gives an amp its particular voice. People wax on about NOS tubes and "vintage iron" and cloth insulation and other nonsense but at the end of the day it's 99% frequency response. The tone stack shapes the frequency response pretty drastically. Many so-called boutique amps are nothing more than a classic design with a tweaked tone stack. The Axe-Fx II is unique in that it is the only modeling device that accurately replicates a tone stack along with the interaction of the controls and influence of surrounding circuitry. I had to solve the mesh equations for each of the major tone stack types which wasn't easy. A tone stack is a 3rd-order network and coding that was a real challenge." [http://forum.fractalaudio.com/threads/when-to-change-the-tonestack-type.79267/#post-965179]</blockquote>

<blockquote>"A Deluxe Reverb, for example, has no Mid pot but a fixed resistor. The value of that resistor is 6.8K. If you use a "Fixed Mid" tone stack the value of the virtual resistor will be 6.8K when the Mid control is at noon." And: "If you use a "Fixed Mid" tone stack the value of the virtual resistor will be 6.8K when the Mid control is at noon." [http://forum.fractalaudio.com/threads/what-is-bf-fixed-mid-tone-stack.98757/#post-1185050]</blockquote>

<blockquote>"The Fat switch changes a value in the tone stack which changes the response of the stack, shifting the mid dip down and making it less pronounced. The Tonestack Freq. parameter frequency scales all the reactive components in the tone stack which is something quite different." [http://forum.fractalaudio.com/threads/fat-switch-is-totally-different-than-axe-fx-ll.145247/page-2#post-1718101]</blockquote>

<blockquote>"If you change the tone stack and don't change the frequency the tone stack will use the standard values. If you put a Dumble tone stack in a 5F8 you'll get a Dumble tone stack exactly as it is in a Dumble. If you change the frequency away from 470 Hz the tone stack values will scale." and "Tonestack Frequency is just a set number for each model. I was trying to make things less confusing than 0.1 - 10. When you select a tonestack it loads a tonestack model which is a bunch of resistor and capacitor values. When the tonestack loads it frequency scales the values based on the entered Tonestack Frequency divided by the default value. The default value matches that of the default tonestack. If you never touch the Tonestack Frequency then the tonestacks load unchanged (i.e. 700/700 = 1). When you select a different tonestack it's center frequency may be different than the default so the displayed frequency doesn't reflect that." [https://forum.fractalaudio.com/threads/match-tone-stack-to-frequency.147334]</blockquote>

<blockquote>"Tonestack Frequency is just a set number for each model. I was trying to make things less confusing than 0.1 - 10. When you select a tonestack it loads a tonestack model which is a bunch of resistor and capacitor values. When the tonestack loads it frequency scales the values based on the entered Tonestack Frequency divided by the default value. The default value matches that of the default tonestack. If you never touch the Tonestack Frequency then the tonestacks load unchanged (i.e. 700/700 = 1). When you select a different tonestack it's center frequency may be different than the default so the displayed frequency doesn't reflect that." [https://forum.fractalaudio.com/threads/match-tone-stack-to-frequency.147334/post-1804831] </blockquote>

<blockquote>"The following are the Fender tonestacks: [https://forum.fractalaudio.com/threads/differences-between-the-fender-tonestack-types-at-the-amp-block.165464/post-1985914]
Brownface: Brownface Vibroverb 
Blackface: Blackface Twin Reverb 
Bassguy: 59 Bassman 
Jr. Blues: Blues Junior 
Super Verb: Super Reverb 
BF Fixed Mid: Blackface with fixed mid resistor (6.8K) 
Vibrato-King: Vibro-king 
Vibrato-Lux: VibroLux 
Vibroverb AA: AA763 Vibroverb 
Super 6G4: Super Amp 6G4 
65 Bassman Bass: Bass channel of 65 Bassman 
Band-Commander: Blackface Bandmaster"
</blockquote>

<blockquote>"You can sweep the midrange frequency using the Tonestack Freq. control." [https://forum.fractalaudio.com/threads/no-option-for-active-tonestack.173832/post-2106254]</blockquote>

<blockquote>"Tonestack Freq frequency scales all the capacitors in the virtual tone stack. Even better than changing the slope resistor." [https://forum.fractalaudio.com/threads/blocks-between-preamp-and-power-amp.173335/post-2101589]</blockquote>

=Power Amp=

==POWER AMP MODELING==

Turns on/off power amp modeling in the Amp block.

Before this parameter was introduced in Cygnus firmware, power amp modeling could be turned off by turning down Supply Sag all the way.

When Power Amp Modeling is turned off, Master works as a simple volume, and Depth and Presence are deactivated.

<blockquote>(Cygnus) "With power amp modeling off the Presence control does nothing." [https://forum.fractalaudio.com/threads/modeling-questions.199009/post-2481687]</blockquote>

==NEGATIVE FEEDBACK==

From the Owners Manual:
<blockquote>
“This controls the amount of negative feedback, or damping, in the power amp simulation. Higher values give a tighter and brighter sound but can sound harsh at very high master volume levels. Lower values give a loose and gritty sound and feel. Like many other power amp parameters, Negative Feedback is set to an appropriate value whenever you change the amp type, but it can be changed as desired. For example, you might dial in some negative feedback on a “Top Boost” amp type to give the power amp a more “American” sound while still retaining the preamp voicing.”
</blockquote>

Changing Negative Feedback (Damping) between 0 and other values used to change the display on the hardware, and switch the Presence control between "Presence" and "HiCut". "Cygnus" amp modeling has changed this: Negative Feedback control no longer interacts with the Presence control. If you turn negative feedback to zero the Presence control won’t do anything as would happen on a real amp.

Adjusting negative feedback on a real amp impacts its volume. Fractal Audio manages this through automatic output level compensation, which works well when the power amp is not clipping (in firmware 23 and later this can be turned off). If the power amp is saturated, both Damping and Level must be increased to maintain the same level.

<blockquote>"The MV control behaves like the modeled amp. The compensation is only for NFB. If you turn NFB down the LEVEL out of the amp block is reduced and vice-versa. This way the volume stays relatively constant. Otherwise the volume changes drastically as you change the NFB." [https://thegearforum.com/threads/nmd-axe-fx-iii-mk-ii-turbo-j-f.3823/post-143580]</blockquote>

Firmware 23 release notes:
<blockquote>"Added NFB Compensation switch in Amp block. This defaults to On. Turning it off disables the negative feedback volume compensation at the output of the Amp block."</blockquote>

Fractal Audio explains:
<blockquote>
"The Axe-Fx attempts to normalize the volume as you change the damping. (...) However, if you are driving the "power amp" hard the equation falls apart because it assumes linear operation. Therefore there may be some volume change. This is done since otherwise you would constantly have to adjust your output volume as you change the damping. Unfortunately it is impossible to predict how saturated the power amp is since that depends on input level. The compensation isn't perfect, the idea is to minimize the volume fluctuations since without compensation the volume would fluctuate wildly." [http://forum.fractalaudio.com/threads/the-damp-control-is-strange.29243/#post-428774]
</blockquote>

<blockquote>
"Another factor which controls power amp hardness is Transformer Match. There are two primary distortion mechanisms in a power amp: grid clipping and plate clipping (PI clipping notwithstanding as this is only audible with a post-PI MV). Grid Clipping is extremely hard, almost a hard clipper (i.e. if(x>a) then x=a). Plate clipping is much softer. However most power amps are slightly undermatched which means the grids clip before the plates clip, but only at those frequencies where the speaker impedance is "nominal". At high frequencies (above 1kHz or so) the rising impedance of the speaker causes the plates to clip before the grids. At the low frequency resonance the plates also clip first. If you increase the transformer matching the plates will clip earlier and, since plate clipping is softer, the distortion will be softer. So turn up the Transformer Match and turn down Negative Feedback for softer power amp distortion." [http://forum.fractalaudio.com/threads/scratchy-sound-on-this-patch-same-for-you.100622/page-2#post-1207496]
</blockquote>

<blockquote>
"There are a two things that determine the smoothness of the power amp distortion:
# Power Amp Hardness. As you've discovered turning it down makes it smoother (obviously). The value controls the "kvb" of the tube model. It's the "knee voltage" for the plate. The formula for plate current is Ip = f(Vg1, Vg2) atan(Vp/kvb). The lower kvb the more abrupt the transition into clipping. Power Amp Hardness is the inverse of this normalized to the plate voltage.
# Negative Feedback. Negative feedback linearizes the power amp. At some point, though, the power amp then runs out of headroom and goes into clipping. The more negative feedback the more linear the response and the more abrupt the clipping. Less negative feedback, smoother clipping. 
I often turn P.A. Hardness down, usually between 3-4, because I like the smoother sound." [https://forum.fractalaudio.com/threads/power-amp-hardness.152582/post-1815292]
</blockquote>

<blockquote>
"Increasing negative feedback flattens the frequency response and increases linearity. You can achieve similar results by flattening the impedance curve in the Speaker page and increasing Power Tube Hardness." [https://forum.fractalaudio.com/threads/more-negative-feedback.153934/post-1829614]
</blockquote>

<blockquote>
"The more feedback the harder the distortion. Most people like less feedback. You also have to be careful as the greater the feedback the greater the chance of instability." [https://forum.fractalaudio.com/threads/evh-tone-deep-dive-feat-dave-friedman-and-pete-thorn.167641/post-2016591]
</blockquote>

From [https://forum.fractalaudio.com/threads/about-negative-feedback.79697/ Cliff's Tech Note]:

<blockquote>
"The Axe-Fx II allows the user to fine-tune the amount of negative feedback in the power via the Damping parameter. The term damping refers to the fact that increasing negative feedback lowers the output impedance and therefore "dampens" the response of the speaker. Power amps often specify their output impedance in terms of "Damping Factor" which is the ratio of the load impedance to the output impedance. The higher the damping factor the less the speaker impedance influences the frequency response. Let's examine what happens as you adjust the Damping parameter. As we increase the Damping we increase the negative feedback. This does several things:
* LOWERS THE GAIN of the power amp. This causes the power amp to not distort as easily since the signal is amplified less and therefore it won't clip as easily.
* Increases the linearity of the power amp. This reduces harmonic distortion but makes clipping "harder" as the transition to clipping is more abrupt.
* Flattens the frequency response. This makes the frequency response more linear and widens the bandwidth. The peaks in the frequency response due to the speaker impedance are flattened and broadened.
As we decrease Damping we decrease the negative feedback which does:
* Increases the gain of the power amp. The causes the power amp to clip more readily.
* Decreases the linearity of the power amp. This increases harmonic distortion and softens the transition into clipping.
* Increases frequency response distortion. The response becomes more scooped and the bandwidth is reduced.
Many guitar players like the sound of amps with no negative feedback. The Vox AC-30 is the classic example of an amp with no negative feedback. The power amp distortion is soft and the scooped response along with lots of harmonic distortion give a bell-like tone for high frequencies and warm low frequency response. The drawback to this is that the low end can get muddy as the low frequencies clip readily due to the frequency response distortion. These types of amps typically do not work well for high-gain tones although there are notable exceptions, i.e. the Dual Rectifier which uses a high-power power amp and bass reduction in the preamp to compensate for the increased bass response.
Fender and Marshall amps (and their derivatives) use varying amounts of negative feedback. The amount of feedback in Marshall amps was all over the map in the early years and seems as though the builders didn't really adhere to rigorous documentation and revision control. As such there can be quite a bit of variation in the sound of these early Marshalls.
So what is the correct amount? There is no definitive answer however there are some guidelines. For more vintage tones less Damping is typically desirable. This gives softer power amp breakup and more "baseline" distortion. For modern, high-gain tones more Damping may be desirable as these tones typically rely on preamp distortion and the power amp is desired to be neutral (which many players describe as "tight"). As stated before the Dual Rectifier in modern modes is a bit of an enigma. The power amp in this mode uses no negative feedback. You can hear this as an increase in volume when you flip the switch to Modern (remember that negative feedback reduces the gain so turning it off will increase the gain).
I have read some users recommending increasing the Damping to reduce the amount of power amp distortion in, for example, Fender models. I do not endorse this viewpoint. The distortion is primarily reduced because the gain is reduced but the power amp will sound more "sterile" due to the increased linearity and flatter frequency response. A better solution is to simply lower the Master Volume. This drives the power amp less while retaining the baseline harmonic distortion, softer transition into clipping and more scooped frequency response.
Modification of the error signal is commonly employed in guitar amps. This was first employed as the ubiquitous Presence control. The presence circuit reduces the amount of feedback at higher frequencies. Since the gain of the power amp is inversely proportional to the amount of feedback, reducing the amount of feedback over only a certain range of frequencies will therefore increase the gain of the amp at those frequencies. The presence control therefore boosts high frequencies. This concept was extended to low frequencies via the Depth or Resonance control. Basically these controls are bass and treble controls for the power amp but operate by reducing the feedback for those bands. On most amps setting these controls fully CCW will basically remove them from the circuit. Turning them CW will reduce the feedback in the prescribed bands thereby increasing the gain of these bands. An exception are Boogie (Mark series) power amps. The presence control in these amps is more complex and the flattest frequency response is achieved with the knob set to noon. Turning the knob CCW will reduce the treble response. Turning it CW will increase it.
Note that these all interact with the Damping control. To hear this reduce the Damping to a value just greater than zero. Note that the Presence and Depth controls will have almost no effect. This is logical since B (beta) is nearly zero and we can't reduce it further."
</blockquote>

Also see Aiken's White Papers
"[http://www.aikenamps.com/index.php/designing-for-global-negative-feedback Designing for Global Negative Feedback]" and "[http://www.aikenamps.com/index.php/what-is-negative-feedback What is Negative Feedback?]".

Fractal Audio:

<blockquote>"These are my notes for the various Plexis:

* Plexi 50W: 100K from 4-ohm tap
* 1987x: 100K from 8-ohm tap
* Plexi 100W: 47K from 8-ohm tap (off speaker jack with two 16-ohm cabs)
* Plexi 100W 1970: 100K from 4-ohm tap
* 1959SLP: 47K from 8-ohm tap
* Plexi 6550: 100K off 4-ohm tap
* 50W Normal - Normal channel. 100K feedback from 4-ohm tap. Cathode cap on second triode.
* 50W High 1 - Treble channel. 100K feedback from 4-ohm tap. No cathode cap on second triode.
* 50W High 2 - Treble channel. 100K feedback from 4-ohm tap. Cathode cap on second triode.
* 1987x Normal - Normal channel. 100K feedback from 8-ohm tap. No cathode cap on second triode.
* 1987x Treble - Treble channel. 100K feedback from 8-ohm tap. No cathode cap on second triode.

You need to know what tap the feedback is from. Going down a tap decreases the feedback by 0.707. Conversely going up a tap increases the feedback by1.414. Up two taps doubles the feedback (4-ohm to 16-ohm).

FWIW, our reference Plexis are 1967 and 1968. I've never seen one with a 27K feedback resistor. That's pretty low so I have to assume it's from the 4-ohm tap. If that is the case you would want to multiply the feedback by about 3.3. So if it's 1.5 you would set it to 4.95.

I've seen JTM45s with 27K off the 16-ohm tap. That's a lot of feedback. In this case you would then double the feedback on top of the 3.3 so 9.9 or so." [https://forum.fractalaudio.com/threads/negative-feedback.188769/post-2340401]</blockquote>

==PRESENCE FREQUENCY==

From the Owners Manual:
<blockquote>
"This multiplier alters the center frequency of the Presence control."
</blockquote>

==DEPTH FREQUENCY==

From the Owners Manual:
<blockquote>
"This multiplier alters the center frequency of the Depth control."
</blockquote>

==MASTER VOLUME CAP==

<blockquote>(Owners Manual) "Sets the value of the bright cap across the Master Volume control."</blockquote>

<blockquote>"Setting it to 1 pF defeats it." [http://forum.fractalaudio.com/threads/axe-fx-ii-firmware-v11-02-and-new-preset-banks.74402/page-2#post-910428]</blockquote>

==MASTER VOLUME LOCATION==

From the Owners Manual:
<blockquote>
"Sets the location of the Master Volume control. Most amps have the Master Volume before the phase inverter (“Pre PI”). On some amps (like the “Class-A” types) the Master Volume comes after the phase inverter (“PI”). A third option, “pre-triode,” is the default for “Hipower” amp types."
</blockquote>

Fractal Audio explains:
<blockquote>
"Most amps are Pre-PI, including Dumbles. Post-PI is rare and often does as a mod. This causes the PI to distort rather than the power tubes. It is a harsher sound."
</blockquote>

<blockquote>
"Moving the Master Volume after the Phase Inverter. This causes the phase inverter to distort. It is a popular mod on amps. In the Advanced menu change MV Location to "Post-PI"." [http://forum.fractalaudio.com/threads/post-pi-mv-try-it.84166/#post-1020827]
</blockquote>

<blockquote>
"Post-PI MV, Try It! Turns a lot of mid-gain amps into ripping monsters. I just tried it on the JCM800 and, dayum... The only caveat is that, like a real amp, the more you turn the MV down the less effective Presence and Depth become (since the loop gain is reduced)." [http://forum.fractalaudio.com/threads/post-pi-mv-try-it.84166]
</blockquote>

<blockquote>
"The swing of a properly designed PI is greater than the range of the power tube grids. For example a 6L6 will typically be biased around -50V. This gives a range of around 100V of swing at the power tube grids. A well-designed PI for an amp like this will typically swing at least 150V and usually closer to 200V or more. This means the grids clip before the PI clips. Then there are the power tube plates. Most designers choose the output transformer so that the plates just start to clip when the grids clip. This gives maximum power since current is maximum when the grids are driven to clipping so you want the plate voltage to be at its maximum excursion at this point. This is a matter of taste. Some designers slightly undermatch since the impedance of the speakers increases at low and high frequencies and this gives a more open tone. Others overmatch as this give a more touch-sensitive overdrive (i.e. Trainwrecks). When you put the MV after the PI you attenuate the signal from the PI going to the grids. This allows the PI to clip before the grids clip. The PI has a fair amount of negative feedback so it's a somewhat hard clipper which gives a fairly aggressive distortion." [http://forum.fractalaudio.com/threads/post-pi-mv-try-it.84166/#post-1021130]
</blockquote>

<blockquote>
"Post-PI is after the phase inverter. It won't do anything until you turn it down. At 10 the location is irrelevant because the control is wide open. Put it at, say, 5 and switch between the locations. The effect should be pretty dramatic. Post-PI is also known as the Lar/Mar master volume mod." [https://forum.fractalaudio.com/threads/fas-crunch-plexi-mv-location.180552/post-2207841]
</blockquote>

==XFORMER DRIVE (TRANSFORMER DRIVE)==

From the Owners Manual:
<blockquote>
"This models core saturation in the virtual output transformer. Higher values simulate a smaller, more easily saturated transformer. The distortion produced by an overdriven output transformer isn’t particularly pretty but it does play a role in the tone and without it the distortion would not be authentic."
</blockquote>

Transformer is often abbreviated to: XFRMR or XFORMER.

Fractal Audio explains:
<blockquote>
"Transformer Drive models the core saturation in the output transformer. The Drive increases the amount of core saturation." [http://forum.fractalaudio.com/threads/does-the-transformer-drive-parameter.39352/#post-535233]
</blockquote>

<blockquote>
"Don't overlook this when striving for "vintage" tones. I was playing around with this last night and it's very powerful in making edge-of-breakup tones sound like an old, well-played amp (if that's your thing). The higher you set the drive the more it saturates the virtual transformer's core. It doesn't affect the B+, that's done with the Sag parameter." [https://forum.fractalaudio.com/threads/tranformer-drive.41252]
</blockquote>

<blockquote>
"The size of the transformer is dictated by the necessary power handling. You can simulate smaller/larger transformers by adjusting the Transformer Drive parameter." [http://forum.fractalaudio.com/threads/x-former-match.63263/page-2#post-784589]
</blockquote>

<blockquote>
"Part of the sound of certain tube amps, particularly those who derive their distortion from power amp overdrive, is attributable to the output transformer. The distortion produced by an overdriven output transformer isn't particularly pretty but it does play a role in the tone and without it the distortion would not be authentic. When a transformer is overdriven the iron core saturates. This happens because all the magnetic domains are aligned with the field and no more can be "rotated". In engineering terms the flux density (B) no longer increases linearly with the flux intensity (H). Since a transformer presents an inductance to the power tubes the flux intensity is inversely proportional to the frequency applied. Therefore the distortion increases at lower frequencies. Manufacturers frequently specify the frequency response of the transformer at its rated power. For example Hammond specifies most of its output transformers of having a bandwidth of 70 Hz to 15 kHz (re. 1 kHz +/- 1 dB) at rated power. The bandwidth of the transformer, however, will be much greater when operated below it's rated power. The Axe-Fx II allows the user to adjust the amount of output transformer saturation via a parameter called XFRMR DRV (Transformer Drive). Lower values decreases the amount of distortion, higher values increase it. The parameter is normalized to a rated-power lower-frequency cutoff of 40 Hz, i.e. a value of 1.0 means that the virtual output transformer will have a lower cutoff frequency (-3 dB point) of 40 Hz when the virtual power amp is operating at the rated power of the transformer. So, if the transformer has a rated power of 50W and the lower cutoff frequency is 40 Hz at that power, setting XFRMR DRV to 1.0 will duplicate that behavior. The formula for rated power cutoff frequency is simply D = f_c / 40, where D is the drive level and f_c is the desired cutoff frequency. For example if we wanted to duplicate the aforementioned Hammond transformer we would first need to find the equivalent -3 dB frequency which is roughly 3/4 assuming it's -2 dB at 70 Hz (since they strangely specify +/- 1 dB) which would be about 50 Hz. Plugging into the formula we get D = 50 / 40 = 1.2. As always use your ears. I personally prefer a setting of around 1.5 - 2.0 for clean-to-lightly distorted tones. I find it adds a bit of richness to the bass frequencies. For higher gain tones I prefer less as it can sound muddy. Note that the effect of output transformer distortion is highly dependent upon the how hard the virtual power amp is driven which is a function of Master Volume and overall gain. There are lots of strange things that happen with an OT saturates but those are trade secrets and I can't elaborate further." [https://forum.fractalaudio.com/threads/transformer-drive.85592]
</blockquote>

<blockquote>
"Lowering the default value of Transformer Drive is similar to upgrading the hardware transformer."
</blockquote>

<blockquote>
"The transformer stuff is very subtle until you turn up Transformer Drive. Turn it up to 3-4 and it gives a cool compression and growl to the low end." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-15-01.168349/post-2022294]
</blockquote>

==XFORMER MATCHING (TRANSFORMER MATCHING)==

From the Owners Manual:
<blockquote>
“Transformer Matching is an extremely powerful parameter. Lower values cause power tubes to clip later and therefore the phase inverter and grid clipping becomes more predominant. At higher settings, power tubes clip sooner and the Resonance settings on the Speaker page become more pronounced. For optimum results bring up the Master until the desired amount of power amp distortion is achieved, then adjust Matching until the character of the distortion is as desired. The various LF and HF Resonance parameters interact strongly with this parameter, so be sure to experiment with those as well when crafting a tone.”
</blockquote>

Fractal Audio explains:
<blockquote>
If you want to simulate a speaker impedance mismatch you use Speaker Impedance. If you want to adjust the transformer impedance ratio you use Transformer Match." [https://forum.fractalaudio.com/threads/updated-speaker-impedance-control.171289/post-2105261]
</blockquote>

Firmware 19.06 release notes:

<blockquote>
"Speaker Impedance in firmware 19.06 and later models the interaction of the virtual transformer and speaker. The Transformer Matching parameter sets the impedance ratio (square of the turns ratio) of the output transformer. And the Speaker Impedance parameter sets the relative nominal impedance of the speaker. Example: to simulate connecting, e.g., a 4-ohm speaker to an 8-ohm output, set Speaker Impedance to 0.5. Conversely to simulate connecting a 16-ohm speaker, set it to 2.0."
</blockquote>

Decrease the value to make the amps sound more “broad”.

Fractal Audio explains:
<blockquote>
"What to use Transformer Match for: The turns ratio of transformers varies by manufacturer, era, etc. For example the original Drake transformers used in old 50W Marshalls had a primary impedance of 3.5K. Some newer transformers have an impedance of 3.2K, about 10% less. To replicate this set Transformer Match to 0.9. This will give a more "open" sound but also a harsher distortion. Increase matching to simulate a higher primary impedance. This will give a more compressed and smoother distortion. Some amps intentionally overmatch their transformers (Trainwrecks) which gives them their characteristic sound." [https://forum.fractalaudio.com/threads/transformer-match-vs-speaker-impedance.154391/post-1835564]
</blockquote>

<blockquote>
"This is an extremely powerful parameter that sets the relative output transformer primary impedance which in turn controls how easily the power tubes are driven into clipping. The higher the Master Volume setting the more pronounced the effect of this parameter. Decreasing the matching causes the power tubes to clip later and therefore the phase inverter and grid clipping becomes more predominant. Increasing the matching causes the power tubes to clip sooner. At lower settings the speaker resonance will be more pronounced, at higher settings the speaker resonance will be less pronounced. For optimum results bring up the Master until the desired amount of power amp distortion is achieved, then adjust the matching until the character of the distortion is as desired. The various LF and HF resonance parameters interact strongly with this parameter so be sure to experiment with those as well when crafting your ideal tone. The value of this parameter is relative to the actual transformer matching which is set internally and not directly exposed. The value is reset to 1.0 whenever they amp type is selected."
</blockquote>

<blockquote>
"Very powerful control. Use in moderation. It changes the turns ratio of the virtual output transformer. Primary impedance is a function of turns ratio. As you increase the turns ratio you increase the impedance by the square of the turns ratio: Zp = N^2 * Zs. An easier description: Increasing Transformer Match -> Thick. Decreasing Transformer Match -> Scooped." [https://forum.fractalaudio.com/threads/5-04-adv-parameters-xformer-match.48005/post-625102]
</blockquote>

<blockquote>
"One of the most powerful controls in the Amp Block Is Transformer Match. If you want a more "open" sound and feel, turn it down. If you want more compressed sound and feel, turn it up. A little goes a long way. Note that this control has more or less effect depending upon the setting of the Master Volume. Transformer Match has more influence at higher MV values and vice-versa. If you turn TM down, you may want to turn MV up to compensate and vice-versa. Turning it way up (around 2.0), for example, simulates the sound of running an 8-ohm speaker on the 4-ohm tap." [http://forum.fractalaudio.com/threads/one-of-the-most-powerful-controls-in-the-amp-block.52338]
</blockquote>

<blockquote>
"Don't overlook this parameter when your MV is set high. It is extremely powerful. A little in either direction can make a big difference. If you want a more open tone, turn it down slightly. If you want more compression and sustain, turn it up a bit. This parameter is essentially a "turns ratio" for the OT." [https://forum.fractalaudio.com/threads/transformer-match.56382]
</blockquote>

<blockquote>
"Higher values are "warmer" but more compressed. Lower values are more open but harsher. Only small adjustments are needed. Transformer Match is the single most powerful advanced parameter when dealing with non-MV amps (i.e. when you have the MV cranked)." [http://forum.fractalaudio.com/threads/warmth-from-6-0-to-9-0.59934/#post-747355]
</blockquote>

<blockquote>
"The most powerful advanced parameter is Transformer Match. When people try different tube brands or rebias their amp to use a different type of tube they make all kinds of hyperbolic claims about those tubes but it isn't really the tube that made the difference. Well it is but it's not because the tube is doing something special. It's simply because the tube has a different transconductance (gain). Amp designers choose an OT turns ratio such that the amp is "matched" to the load. However "matched" is a nebulous term since tube gains vary, speaker impedance is variable and bias point is adjustable. Therefore there is no absolute turns ratio that ensures perfect matching. Matching implies that the swing at the power tube grids just pushes the plates to the rails. If the output transformer is undermatched, the grids will clip before the plates hit the rails and vice-versa. Designers also select the turns ratio based on personal preference. Some designers prefer undermatched OT since this gives a more "open" sound, while others prefer overmatched since this gives more touch response. For example, a Trainwreck is highly overmatched. For a given OT, if the tubes have higher gain than originally then this effectively overmatches the OT and vice-versa. Now this matters most for non-MV amps that get their distortion from the power amp, i.e. old Marshall, Fender, etc. So... if you are going to experiment with any advanced parameter, start with Transformer Match. A little bit in either direction can make a big difference. Note that the Transformer Match parameter is relative to the internal value." [https://forum.fractalaudio.com/threads/the-most-powerful-advanced-amp-parameter.61820]
</blockquote>

<blockquote>
"Transformer match has nothing to do with the physical size of the transformer. It is the turns ratio. The higher the turns ratio (higher Transformer Match) the higher the reflected impedance from the speaker and vice-versa. The higher the value the sooner the power tubes distort. The optimum turns ratio is such that the maximum power can be obtained. Tube amps tend to be slightly undermatched though since the speaker impedance is not constant. This varies with the make/model of amp and is encoded in the model data. The size of the transformer is dictated by the necessary power handling. You can simulate smaller/larger transformers by adjusting the Transformer Drive parameter." [http://forum.fractalaudio.com/threads/x-former-match.63263/page-2#post-784589]
</blockquote>

<blockquote>
"The internal default value is based on the amp that was modeled and an assumed speaker voice coil resistance of 0.8 times the nominal impedance. I.e., if the speaker is rated at 8 ohms the assumed voice coil resistance is 6.4 ohms. Some speakers are slightly below this, others are above. 16-ohm Celestion Greenbacks, for example, are about 12 ohms so that would 0.75 times the nominal impedance. To simulate this you would reduce the matching to 0.75/0.8 = 0.9375. If you find yourself lowering this value consistently then your Master Volume is too high (assuming it's a MV amp). If it's a non-MV amp and you still find yourself lowering this value then you'll probably find the tone harsh or too scooped at loud volumes. In general I find people set the MV too high on MV amps. I think they don't realize that most MV amps achieve full volume around 2-4 on the MV knob and then it's just compression after that. Amp makers are partly to blame here as they do this on purpose to make their amps seem louder than they really are. Of course the sweet spot is that point at which the power amp starts to compress so you want to set the MV high enough to get into the sweet spot. It's a psychological thing. People always like a more "open" sound even though they don't really understand what makes a tone "open". When you lower the Transformer Match you reduce the power tube compression of the lows and highs. The problem is humans naturally gravitate to this to the point that they will make the tone excessively "open" and then it doesn't fit in the mix. I do not recommend deviating much from 0.9 - 1.1. Of course there are no rules. With real amps some people like that more open sound and achieve it by plugging their cab into the higher impedance output, i.e. plugging an 8-ohm cab into the 16-ohm jack. This would be equivalent to setting the match to 0.5. SRV liked it the other way round IIRC which would equate to a match value of 2.0." [http://forum.fractalaudio.com/threads/fw-11-03-xformer-match-settings.75161/#post-919805]
</blockquote>

<blockquote>
"Guitar folklore has it that SRV and Joe Walsh intentionally mismatched their speaker impedance. I imagine others have done this. The general idea is you plug an 8-ohm speaker into the 4-ohm jack or vice-versa. The Axe-Fx allows you to replicate this behavior using the Transformer Match control. To simulate plugging an 8-ohm speaker into the 4-ohm jack set Transformer Match to twice it's current setting (i.e. 2.0). For the other way around set it to half (i.e. 0.5). And you don't have to worry about frying your OT." [https://forum.fractalaudio.com/threads/simulating-speaker-impedance-mismatch.77944]
</blockquote>

<blockquote>
[https://forum.fractalaudio.com/threads/the-secret-weapon-transformer-match.98527/ Cliff's Tech Note]: "One of the most important "advanced tweaks" in the amp block is the Transformer Match parameter (XFRMR MATCH). This control sets the relative turns ratio of the virtual output transformer. Each amp model has a default turns ratio embedded in the model data. The Transformer Match parameter adjusts that ratio relative to this default value. Turning it down reduces the ratio and makes the transformer "undermatched". Turning it up increases the ratio and makes the transformer "overmatched". Why is this important? In a "classic" designed power amp the transformer turns ratio is selected to provide the full power the output tubes are capable of to the load. IOW, when the tubes are delivering their maximum current the voltage at the plates is near zero (the voltage swing is maximum) for the NOMINAL speaker impedance. If the transformer is undermatched the tubes won't fully saturate. If the transformer is overmatched the tubes will saturate early. Most guitar amps are slightly undermatched. This wouldn't really matter than much if the load were a simple resistance but a speaker is a reactive load. As mentioned in my other posts the impedance has a low-frequency resonance and a high-frequency boost. If the transformer were perfectly matched then the plate voltages would reach maximum excursion when the current was at a maximum only at those frequencies where the speaker impedance equals the nominal impedance. When the speaker impedance is greater than the nominal impedance the tubes saturate early. This has the effect of distorting the highs and lows before the mids. If you decrease the matching the highs and lows don't distort as quickly and the amp will sound more "open". However the distortion can be harsher since power tube current limiting is harder than voltage limiting. If you increase the transformer matching the highs and lows will distort sooner and the amp will sound more "compressed. The resulting distortion will be smoother due to the softer nature of the voltage limiting. As explained above a classic design selects the turns ratio to give the maximum power for the nominal speaker impedance. However the "nominal" speaker impedance is just that and the actual speaker impedance varies considerably from model to model. The impedance of a typical 8-ohm speaker can vary 20% or so. If the actual impedance is lower then this effectively undermatches the transformer and vice-versa. Furthermore the transconductance and maximum current capability of the power tubes varies. For example, the amp models in the Axe-Fx that use EL34s were modeled with Mullard tubes (as these are considered the best sounding). A set of JJ EL34s will actually produce slightly more current and saturate earlier. This effectively overmatches the output transformer. Some amps deliberately overmatch the output transformer, i.e. Trainwrecks. This results in a smoother power amp distortion with more compression of the highs and lows. The amount of overmatching is considerable, typically about 50% Now, the effect of the transformer matching is only evident when the power amp is distorting. Non-MV amps get most of the distortion from the power amp so the effects of altering this parameter should be readily apparent. Master Volume amps get most of their distortion from the preamp so the effects of altering this control may not be as noticeable if the MV is turned down. Small adjustments can make a big difference. I typically never adjust more than 20% (0.8 to 1.2) and usually less than 10%. If you find your tones are slightly too open and harsh turn up the Transformer Match slightly. Conversely if you find your tones too compressed turn it down a bit. Be warned that turning it down may seem to sound "better" because the volume will increase (our old friends Fletcher and Munson again) but then when you play loud it will be boomy and harsh. You want some of those high and lows to be distorted early so that things aren't too scooped."
</blockquote>

<blockquote>
"Another factor which controls power amp hardness is Transformer Match. There are two primary distortion mechanisms in a power amp: grid clipping and plate clipping (PI clipping notwithstanding as this is only audible with a post-PI MV). Grid Clipping is extremely hard, almost a hard clipper (i.e. if(x>a) then x=a). Plate clipping is much softer. However most power amps are slightly undermatched which means the grids clip before the plates clip, but only at those frequencies where the speaker impedance is "nominal". At high frequencies (above 1kHz or so) the rising impedance of the speaker causes the plates to clip before the grids. At the low frequency resonance the plates also clip first. If you increase the transformer matching the plates will clip earlier and, since plate clipping is softer, the distortion will be softer. So turn up the Transformer Match and turn down Negative Feedback for softer power amp distortion. However... designers know all this and they design an amp to sound best in a mix (at least the good ones do). Soft clipping sounds great when you are playing by yourself but as soon as you are in a band context the sound gets lost since hard clipping helps cut through the mix. Amps designed for rock typically have harder clipping than an amp designed for blues or jazz. A 5150, for example, has an extreme amount of negative feedback which makes the power amp very linear and clips very hard. A Deluxe Reverb, otoh, has low negative feedback and large cathode bypass caps on the last preamp stage. This makes the clipping softer and the sound less "clear"." [http://forum.fractalaudio.com/threads/scratchy-sound-on-this-patch-same-for-you.100622/page-2#post-1207496]
</blockquote>

<blockquote>
(firmware Ares 9) "New power amp modeling algorithm. This new algorithm now also separates the transformer matching from the speaker impedance. A new parameter, Speaker Impedance, allows adjusting the relative impedance of the virtual speaker. For example, to simulate connecting a 16-ohm speaker to an 8-ohm output set Speaker Impedance to 2.0. Transformer Matching, on the other hand, changes the impedance ratio of the virtual output transformer."
</blockquote>

<blockquote>
(firmware Ares 9) "Prior to 9.xx the "matching" was controlled by a single Transformer Match parameter. 9.xx introduces a new Speaker Impedance parameter. The distortion of a tube power amp is dependent upon the load presented to the power tubes. The overall sound, however, is also often dependent upon the voltage at the speaker since that voltage is fed back to the input." [https://forum.fractalaudio.com/threads/transformer-match-vs-speaker-impedance.154391/post-1835564]
</blockquote>

<blockquote>
(firmware Ares 10) "The range of the Transformer Match control has been reduced to 0.5 to 2.0. Existing presets will have this value reset to 1.0."
</blockquote>

Aiken has more information:
* [http://www.aikenamps.com/index.php/output-transformers-explained White Paper: Output Transformer]
* [http://www.aikenamps.com/index.php/a-glossary-of-common-amplifier-terms Glossary]

==SPEAKER IMPEDANCE (VOICE COIL RESISTANCE)==

"Speaker Impedance" was temporarily renamed "Voice Coil Resistance", and got its original name again in firmware 19.06 for the Axe-Fx III.

Speaker Impedance in firmware 19.06 and later models the interaction of the virtual transformer and speaker. The Transformer Matching parameter sets the impedance ratio (square of the turns ratio) of the output transformer. And the Speaker Impedance parameter sets the relative nominal impedance of the speaker. Example: to simulate connecting, e.g., a 4-ohm speaker to an 8-ohm output, set Speaker Impedance to 0.5. Conversely to simulate connecting a 16-ohm speaker, set it to 2.0.

Earlier:

<blockquote>(firmware 19.02) "Renamed Speaker Impedance to Voice Coil Resistance to more accurately describe the function of the control. Note that this includes all other “parasitic” resistances, i.e., speaker cable resistance, output transformer winding resistance, etc."</blockquote>

<blockquote>(firmware Ares 9) "New power amp modeling algorithm. This new algorithm now also separates the transformer matching from the speaker impedance. A new parameter, Speaker Impedance, allows adjusting the relative impedance of the virtual speaker. For example, to simulate connecting a 16-ohm speaker to an 8-ohm output set Speaker Impedance to 2.0. Transformer Matching, on the other hand, changes the impedance ratio of the virtual output transformer."</blockquote>

<blockquote>"Leave it at 1.0 for accuracy. When you select an impedance curve the actual speaker impedance is part of that data (but hidden from the user). The exposed Speaker Impedance control scales that loaded impedance." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-19-01.180998/post-2220824]</blockquote>

If you are using an MV amp (i.e. 5150) then you really don't need to adjust Speaker Impedance. If you want a more scooped sound lower the MV and vice-versa. Speaker Impedance is a useful control for non-MV amps (i.e. Plexis).

<blockquote>(firmware Ares 9) "Prior to 9.xx the "matching" was controlled by a single Transformer Match parameter. 9.xx introduces a new Speaker Impedance parameter. The distortion of a tube power amp is dependent upon the load presented to the power tubes. The overall sound, however, is also often dependent upon the voltage at the speaker since that voltage is fed back to the input.

What to use Speaker Impedance for: The actual impedance of a speaker can vary quite a bit. For example a Celestion Greenback is available in 8 and 16 ohm versions. The 8-ohm version has a DC resistance (DCR) of 6.57 ohms. The 16-ohm version has a DCR of 12.13 ohms. The Plexi models in the Axe-Fx assume 16-ohm speakers were used as the Marshall cabs used 16-ohm speakers.

The DCR normalized to the speaker impedance is therefore different for the two versions. For the 8-ohm version the DCR normalized to the impedance is 6.57/8 = 0.82. The 16-ohm version is 12.13/16 = 0.76. The relative impedance is therefore 0.82/0.76 = 1.08. Therefore the 8-ohm version of the speaker will increase the voltage at the primary by 8% which means the power amp breaks up a bit earlier (more gain). To simulate this increase Speaker Impedance to 1.08.

All the models use a DCR commensurate with the original speakers when available. For amp heads with no matching cabinet the DCR is assumed to be 6.7 ohms. I contemplated naming the control "Speaker DCR" but figured that was too vague but it's actually a better description of what the control does (and the internal parameter name is speaker_dcr).

Another use for Speaker Impedance is to simulate intentional mismatching. SRV, Joe Walsh, etc. would intentionally mismatch their amps by connecting the speaker to the "wrong" output jack. For example, to simulate connecting a 16-ohm speaker to the 8-ohm output jack set Speaker Impedance to 2.0 (or 1.9 in the case of a Greenback)." [https://forum.fractalaudio.com/threads/transformer-match-vs-speaker-impedance.154391/post-1835564]</blockquote>

<blockquote>"The Speaker Impedance Curves include the D.C.R. If you select, for example, the 4x12 Basketweave, its D.C.R. is 14.0 ohms. So if you have a cab with an actual D.C.R. of 14.5 the Speaker Impedance value would be 14.5 / 14.0 = 1.036." [https://forum.fractalaudio.com/threads/updated-speaker-impedance-control.171289/post-2105192]</blockquote>

==PHASE INVERTER BIAS EXCURSION==

From the Owners Manual:
<blockquote>
"Controls how much the virtual phase inverter bias shifts when overdriven."
</blockquote>

Fractal Audio explains:
<blockquote>
”PI Bias Excursion controls the virtual Phase Inverter bias excursion. It's a subtle effect on most amps but some amps display significant bias excursion, i.e. Trainwreck Express. It's a form of blocking distortion.” [https://forum.fractalaudio.com/threads/pi-bias-excursion.157062/post-1871331]
</blockquote>

Firmware 19.01 for the Axe-Fx III:

<blockquote>
"Improved Phase Inverter Bias Excursion accuracy for some amp models (mostly non-MV types). Note: The improved PI Bias Excursion accuracy results in an increase in bias excursion in most cases. Bias excursion primarily manifests as intermodulation distortion, particularly subharmonic distortion. This produces a chunkier tone with more growl and also yields a thicker tone when rolling off the volume or playing lightly. The amount of bias excursion can be adjusted using the PI Bias Excursion control in the Advanced menu."
</blockquote>

==CATHODE RESISTANCE==

From the Owners Manual:
<blockquote>
"There are two types of power tube bias: fixed bias and cathode bias. In a cathode biased amp a resistor is placed between the power tube cathode and ground thereby self-biasing the tube. This parameter sets the value of the virtual cathode resistor. Higher values result in a more negative bias and push operation towards Class-B, resulting in more crossover distortion."
</blockquote>

Fractal Audio explains:
<blockquote>
"Sets the cathode resistance of the power tubes. Should only be used with "Class A" amps, i.e. AC-20 DLX, etc. Lower values increase the bias current. Note that some amps have separate bias resistors while others have a shared bias resistor. The choice of split/shared is not exposed to the user." [http://forum.fractalaudio.com/threads/cathode-resistance.122674/#post-1459417]
</blockquote>

<blockquote>
"P.A. Cathode Resistance is the normalized value of the resistance seen by the cathodes of the virtual power tubes. Higher values bias the tubes colder (from Class-AB towards Class-B) and result in more crossover distortion (fizz). Lower values bias the tubes hotter and result in a smoother character." [https://forum.fractalaudio.com/threads/believe-it-or-not-cant-get-the-tweed-amps-to-sounds-fizzy-enough.168701/post-2026831]
</blockquote>

==CATHODE TIME CONSTANT==

From the Owners Manual:
<blockquote>
"This sets the time constant of the virtual RC cathode network for amp types that are cathode biased."
</blockquote>

==PLATE SUPPRESSOR DIODES==

Added in firmware 21 for the Axe-Fx III. Release notes:

<blockquote>"Added “Plate Suppressor Diodes” parameter. This value is set automatically when the amp model is chosen but the user can override the default setting. Most amps do not have suppressor diodes but some do (e.g., Trainwreck Express). These diodes (also called “snubber” or “flyback” diodes) prevent undershoot on the power tube plates due to inductive kick and reduce upper harmonics thereby reducing “fizz”."</blockquote>

Tech Note: [https://forum.fractalaudio.com/threads/about-the-plate-suppressor-diodes-parameter.188142/post-2333785]

<blockquote>"The new "Cygnus X-2" amp modeling introduced a new parameter called "Plate Suppressor Diodes". Plate suppressor diodes, also known as "snubber" or "flyback" diodes are diodes connected between the power tube plates and ground.

The purpose of these diodes is to clamp the inductive "kick" caused by the reactive load seen by the plates. A speaker is a reactive load and has a positive reactive component at high frequencies. This means it looks inductive. Inductors resist change in current. When the plate voltage drops rapidly to zero the inductance of the load causes the voltage to undershoot.

A suppressor diode clamps the voltage and prevents undershoot. This does two things:
1. It prevents excessive voltage at the plates and transformer primary. This protects the transformer from damage due to dielectric breakdown.
2. It also reduces "fizz". The undershoot manifests as increased high frequency content in the range where the load is inductive, typically from 1kHz and up.

Most amps don't have flyback diodes but there are a handful of notable exceptions: Trainwreck Express, Fender Blues Jr., Peavey 5150, and several others.

Flyback diodes were originally added to amps to protect the output transformer but most, if not all, techs don't realize that they also change the clipping behavior.

[[image:Snubber_diodes.PNG|link=]]

The blue trace is a plot of a tube power amp output with no flyback diodes. The green trace is the same power amp with flyback diodes. Those spikes in the voltage are what can damage a transformer and also what cause "fizz".

In a real tube amp these diodes are under intense stress and may fail. In our virtual world these diodes are indestructible.

So if you like your tones as fizz-free as possible experiment with the Plate Suppressor Diodes parameter. Note that turning them on will reduce the "chime" at edge-of-breakup and may not be suitable for vintage tones."
</blockquote>

<blockquote>"That's what amps do. You don't hear it through a guitar cab typically but using close-mic'd IRs it's more noticeable. You can reduce it by turning on the Plate Suppressor diodes. Trainwrecks have plate suppressor diodes for just this reason." [https://forum.fractalaudio.com/threads/note-decay-crackle-sizzle-noise.193575/post-2407689]</blockquote>

=Power Tubes + Cathode Follower (CF)=

==POWER TUBE TYPE==

From the Owners Manual:
<blockquote>
“Changes the characteristics of the virtual amp power tubes. The virtual power amp includes modeling of the plate impedance of the power tubes. Plate characteristics are adjustable via Dynamic Damping, an advanced parameter. The Tube Type parameter allows you to select from common power tube types: 6AQ5, 6L6/5881, 6V6, 300B (triode), 6550, 6973, EL34/6CA7, EL84/6BQ5, KT66, KT77, KT88, 5881 and 6L6GB.”
</blockquote>

<blockquote>
"Selecting a Power Tube Type loads the “knee voltage” for the power tubes and this voltage can be adjusted up or down using Power Tube Hardness. Higher values yield a lower knee voltage and more abrupt clipping and vice-versa. Existing presets will have Power Tube Hardness reset to 5.0 upon recall."
</blockquote>

<blockquote>
(Axe-Fx II) "Added Tube Type parameter to amp block. This allows selecting Tetrode (i.e. 6L6, KT66, etc.) or Pentode (i.e. EL34, 6BQ5, etc.) power tube types. The type defaults to the appropriate value when a model is chosen but may be overridden by the user."
</blockquote>

<blockquote>
(Axe-Fx II) "Added selectable power tube types for Amp block. Available types are: EL34, EL84, 6L6, 6V6, KT66, KT88, 6550, 6973, 6AQ5 and 300B (triode). Also available are an ideal tetrode and ideal pentode. The power tube type defaults to the appropriate type when the amp type is selected but may be overridden by the user. The power tube type presets the Dynamic Damping parameter as well as several internal parameters."
</blockquote>

Fractal Audio explains:
<blockquote>
"The tubes are "normalized" so that you don't have to do anything to the transformer. The internal values for the power tubes are based on typical transformer values. For example, the values derived for the EL34 are based on a primary impedance of 3200 ohms (assuming one pair of tubes). The impedance ratio of the transformer affects the values slightly as the plate impedance is reflected to the secondary (or the load is reflected to the primary) and the ratio therefore affects the interaction." [http://forum.fractalaudio.com/threads/axe-fx-ii-firmware-version-12-04-public-beta.80497/page-5#post-977955]
</blockquote>

<blockquote>
[https://forum.fractalaudio.com/threads/why-power-tubes-sound-different.79962/ Cliff's Tech Note]: "You'll often read that 6L6's sound "full" whereas EL34's have more midrange and other colloquial descriptions of the tone of a power tube. These myths are perpetuated by forum dwellers, uninformed tube "experts" and even amp manufacturers as marketing tools. Well, the fact is that power tubes do NOT sound different. They do not have any intrinsic tone. "But I can hear the difference when I change to a different type of power tube. How can that be?" A power tube has a very flat frequency response and they all clip roughly the same. If you put a resistive dummy load on a tube power amp (assuming it doesn't have any intentional frequency shaping) it will measure very flat. However a speaker is not a resistive load. A speaker is a highly reactive load. As I've mentioned in the other threads in this forum section a speaker has an impedance that is sort of scooped at the midrange frequencies. It is the impedance of the speaker that affects the tone of the amp and different types of power tubes react differently with that impedance. As I've mentioned before a power tube is nearly a current source. The operative word here is "nearly". No power tube has an infinite plate impedance and that's why power tubes sound different. A current source has infinite output impedance, an actual power tube has a finite output impedance. The output impedance of a power tube (or any active device for that matter) is defined as delta V / delta I which is the change in voltage vs. the change in current. Let's take a 6L6 for example. Let's assume that the tube has a quiescent operating point of 300V and let's assume we swing +/- 100V around that point. If we look at the plate graphs for a 6L6 at a bias of -10V we see that the plate current at 200V is 95 mA and at 400V it's 105 mA (roughly). Using our formula for impedance we get 200/0.01 = 20 Kohms. Now let's take an EL34. At 200V the current is 130 mA and at 400V the current is 150 mA. The plate impedance is therefore 10 Kohms which is half that of the 6L6. This lower output impedance "de-Q's", or flattens, the speaker impedance. Essentially the EL34 has a higher damping factor than a 6L6. This higher damping factor reduces the mid-scoop due to the speaker impedance. This makes the tone have more midrange. There's a little more to it as the output transformer plays a role as well and 6L6 power amps typically have a slightly higher impedance ratio. There's also different operating voltages and bias points but I'm trying to keep this simple. You can simulate changing power tubes in the Axe-Fx by simply increasing or decreasing the LF and HF resonance values."
</blockquote>

<blockquote>
"Changing the power tube between pentode and tetrode doesn't change the sound in the same way actually changing tubes would because it only changes the distortion curves. It does not change the transconductance so the transformer matching is constant. When you put different power tubes in an amp the difference in tone isn't due to some inherent difference in the "sound" of the tubes. It's mainly due to the different transconductances. The transconductance of an EL34 is about 30-40% more than the transconductance of a 6L6 ([http://forum.fractalaudio.com/threads/preamp-tube-types.94404/#post-1131521 edited]). This means that the plate current will be twice as great for a given grid voltage. This makes EL34s sound "more midrangey" and 6L6s sound "tighter" or "fuller". The truth is that if you bias them correctly and compensate for the difference in transconductance you will hear very little difference. Unfortunately you can't compensate for the transconductance easily in a real amp without changing the gain of the phase inverter and/or putting in a different output transformer." [http://forum.fractalaudio.com/threads/mark-v-tone-match.75082/#post-924520]
</blockquote>

<blockquote>
"There won't be the same variation you would get by substituting in a real amp because the transformer matching stays consistent. IOW, if you put an EL84 in a Plexi the transformer matching is going to be way too low because the transconductance is very different. The power tube models normalize the transconductance so switching power tubes also effectively installs the correct output transformer For example, a pair of EL-84s want around 8K primary impedance. A pair of EL-34s want around 3.2K. If you put EL-84s in a Plexi the transformer will then be very undermatched (and probably burn the tubes up). In the Axe-Fx if you change the tube type to EL-84 you get all the parameters of an EL-84 but the virtual transformer will be changed so that the matching stays the same. You will get the crunchier tone of the EL-84 though since its knee voltage (kvb) is roughly half that of an EL-34." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841268]
</blockquote>

<blockquote>
"There are a variety of parameters loaded when a tube type is selected. Hardness, which is inversely proportional to the knee voltage, is exposed to the user as it is the most audible." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841317]
</blockquote>

<blockquote>
(about Mesa's Mark IV Pentode/Triode switch) "There isn't any way to run the virtual power tubes in triode mode... but you can change the Power Tube Type to "300B" which is a triode. When you run a pentode (or beam tetrode) in triode mode you connect the screen to the anode which effectively defeats the screen. This lowers the output impedance of the plate significantly which, in turn, lowers the output impedance of the amp itself making the voltage output less dependent on the speaker impedance. Using the 300B tube type should get you pretty close." [https://forum.fractalaudio.com/threads/mesa-mark-iv-pentode-triode-switch.122527/post-1458293]
</blockquote>

<blockquote>
"The Axe-Fx automatically adjusts the output transformer to match the power tubes so the difference isn't nearly as apparent as it would be if you were to change the tubes in a real amp. In other words a pair of EL-34s wants to see about 3200 ohms whereas a pair of 6L6s want to see about 4000 ohms. The Axe-Fx III automatically increases the transformer matching if you change the tubes from EL-34 to 6L6. I've been debating removing this "mu normalization" but it would break existing presets where people had changed the tubes from the default type."
</blockquote>

And:

<blockquote>
“All the tube models are "normalized". IOW if you change tube types the bias current stays the same, the transconductance (mu) is the same, etc. All that changes are the tube parameters that determine the shape of the I/V curves. The reason for this is you would never put EL-84s in an amp designed for 6L6s. First of all they wouldn't fit, but more importantly the bias circuit would be all wrong and the transformer impedance ratio would be way off. It would sound completely wrong. What you mostly hear when you swap tubes in a real amp is the change in the transconductance and concomitant transformer mismatch. The curves aren't really all that much different. In fact the parameters for 6L6s and EL34s aren't all that different aside from the mu. A JJ 6L6GC has roughly the same parameters as a Mullard EL34. kvb for both is around 30V, the big difference is mu which means a pair 6L6s want a primary impedance of 4K whereas a pair of EL34s want around 3.2K. If you put 6L6s in an amp designed for EL34s the OT will be undermatched which will make the amp sound more "open" and the power amp won't distort as much. You also run the risk of redplating the tubes because you might go outside the SOA.So, all this being said, the biggest tools in your arsenal are the Transformer Match and Speaker Impedance parameters which can be used to simulate different matching." [https://forum.fractalaudio.com/threads/power-amp-power-tube-type-selection.155021]
</blockquote>

<blockquote>
(firmware Ares 12.09) "Added 6CA7 power tube type. While the 6CA7 is generally regarded as a substitute for the EL34 it is actually a different tube with the 6CA7 being a beam tetrode. This particular tube type is modeled after the original Sylvania “Fat Bottle” 6CA7."
</blockquote>

<blockquote>
"You can only use the transconductance values when changing between tubes with roughly the same maximum power dissipation. It doesn't work if you want to change a 6L6 to an EL84.

I know everyone wants this to work like a real amp but it's simply not going to happen. Some amps let you swap between EL34s and 6L6s and change bias accordingly. The problem is the Axe-Fx III lets you change between all the possible tube types. If you were to put an EL84 into an amp designed for EL34s it would sound terrible (and also destroy the EL84). A pair of EL84s wants to see upwards of 8K plate-to-plate. A pair of EL34s wants to see around 3.2K. If you put the EL84s in the amp the transformer would be extremely undermatched. It would also exceed the SOA of the tube and destroy it. In the Axe-Fx III the virtual tube wouldn't be destroyed but it would sound terrible and people would complain it doesn't sound right.

Those amps where you can use different power tubes don't swap the transformer. They just rebias the tubes. If the transformer turns ratio is optimized for 6L6s installing EL34s will cause the transformer to be slightly undermatched which is the primary reason the tone changes. Conversely if the transformer is optimized for EL34s installing 6L6s will cause it to be overmatched.

You have far more control over the power tube response with the Axe-Fx. Rather than complaining that swapping power tubes doesn't work exactly the same learn to use the fantastic power available to you. Learn to hear the difference changing the Transformer Matching and/or Speaker Impedance makes. These are controls you'll never find on a real amp. Changing the matching on a real amp involves removing the transformer and installing a new one. If you want fine gradation in matching you'd need something with many taps." [https://forum.fractalaudio.com/threads/no-differences-when-changing-tubes.163545/post-1962569]
</blockquote>

<blockquote>
"As it stands I don't change the transconductance when changing tubes. The problem is if I did change the transconductance things would change dramatically if, for example, going from a 6L6 to an EL84. An EL84 has around twice the transconductance. In a real amp you can't put EL84s in an amp designed for 6L6s. What I change are the parameters that control the frequency response and distortion." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-19-00.180535/post-2209626]
</blockquote>

Seymour Duncan talks about this further in "[https://www.seymourduncan.com/blog/latest-updates/know-your-amp-different-kinds-of-tubes Know Your Amp: Different Kinds of Tubes]".

==POWER TUBE GRID BIAS==

From the Owners Manual:
<blockquote>
“Sets the bias point of the virtual power amp. Lower values approach pure Class-B operation. Higher values approach pure Class-A operation.”
</blockquote>

Fractal Audio explains:
<blockquote>
"For as long as I can remember I've always biased my amps around 60% of maximum dissipation. But I just ran across a site that claims 70% is optimal for a Class-AB amp. So I tried it on my go-to Plexi patch and I do believe it sounds better. Set Power Tube Grid Bias to 0.7 to do this." [https://forum.fractalaudio.com/threads/hmmmm-bias-point.154630/post-1838912]
</blockquote>

<blockquote>
"The early Cygnus betas were colder than the later betas. Originally I had set the bias equal to the reference amps but many of the reference amps are biased cold because most manufacturers bias amps cold from the factory for warranty reasons. In the later betas I put the bias points at where a technician would typically bias an amp after replacing the tubes, i.e. 60-70% of max. plate dissipation." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-12-cygnus-firmware-public-release-candidate.172027/post-2076897]
</blockquote>

<blockquote>
To simulate an amplifier running in Class A, turn up Power Tube Grid Bias.
</blockquote>

<blockquote>
"Turn up Power Tube Grid Bias. In real life that is tough on tubes as it makes them run very hot." [http://forum.fractalaudio.com/threads/replicating-the-bogner-ecstasy-class-a-mode.145294/#post-1718463]
</blockquote>

<blockquote>
"Yes, turn Power Tube Grid Bias all the way up." [https://forum.fractalaudio.com/threads/mesa-mk-4-class-a-possible.154438/post-1836241]
</blockquote>

<blockquote>
[https://forum.fractalaudio.com/threads/why-your-amp-doesnt-sound-like-our-amp.172907/post-2090367 Why Your Amp Doesn't Sound Like Our Amp]: 
"The transconductance (gain) of a power tube can vary greatly. This is why power tubes are color coded, sold in matched sets, etc. Amps come in two flavors: fixed bias and cathode bias. Fixed bias amps apply a "fixed" voltage to the grid of the power tubes. Cathode bias amps use a resistor between the cathode and ground to self bias the tube. Most, but not all, fixed bias amps allow the user to adjust the bias point of the amp. This allows the bias point to be set to an optimum value for the particular set of tubes installed (since the transconductance can vary greatly). Some fixed bias amps do not allow adjustment. Examples are Mesa/Boogies, 5150s, and several other brands/types. The drawback of this is that the bias can vary greatly depending upon the gain of the tubes installed. Due to this the manufacturers err on the safe side and the bias is usually much colder than the ideal value. Most cathode biased amps are not adjustable. Again you are at the mercy of the tube's gain but these amps tend to be biased hot to begin with and have higher transformer matching which prevents excursion outside of the S.O.A. (safe operating area). If the bias is adjustable where the manufacturer decides to bias their tubes is a matter of preference. Most manufacturers bias their tubes on the cold side to prevent premature failure and reduce warranty claims. Especially the larger manufacturers. This leads to the question of "what is the ideal bias point?" The pervasive school of thought is you adjust the bias so the idle dissipation is 60-70% of the tube's peak power rating. This is a safe approach and ensures that the tubes don't "red plate" and live fairly long and prosperous lives. My opinion is that the ideal bias point is NOT a function of the tube's power rating. It's the point at which the power amp's transfer function is most linear. Unfortunately operating the tubes at that point can result in exceeding the tube's S.O.A. So the optimum bias point depends on the tube's power rating, the transformer primary impedance (matching) and the user's tolerance to tube replacement frequency. For example, if we bias an EL34 based power amp at 60% peak dissipation it's actually running fairly cold. If we know that the transformer is slightly overmatched we can bias the tubes hotter, 70% or even more. This will result in a warmer tone but the tubes will wear faster. What does all this mean? Well, I bias the virtual tubes on the warm side. EL34s are biased at around 70% because we don't have to worry about them wearing out. 6L6s are biased a little colder, around 60% but this is actually as "warm" as the EL34s because of the higher plate dissipation of a 6L6. In practice this means that the models in the Axe-Fx will biased warmer than a new amp straight out of the box as most amps are biased cold (too cold IMO). After you wear the tubes out and bring it to a tech the tech will replace those tubes and bias them hotter than factory. So if you're comparing your new, out-of-the box 5150 with the Axe-Fx model the amp will probably sound "colder". Some people like this, many do not. If you like a colder sounding power amp it's just a knob twist away."
</blockquote>

<blockquote>
"To reduce/eliminate crossover distortion increase Power Tube Grid Bias. A value of 1.0 will have no crossover distortion." [https://www.thegearpage.net/board/index.php?threads/axe-fx-iii-effects.2260258/post-32648602]
</blockquote>

<blockquote>
"There is not a linear relationship between the grid bias value and quiescent dissipation as a percentage of maximum. 0.5 is roughly 66% IIRC but I'd have to run the numbers again to be sure.

With a real tube amp there is no hard-and-fast rule. Some say 60%, some say 70%. But that's a simplistic view of the problem. The optimum value is dependent on many things: B+ voltage, transformer turns ratio, etc. For example, if the transformer is overmatched you can run the bias hotter and this is indeed how some amps are designed (i.e. Trainwrecks).

The reason for the "rule" in tube amps is to reduce crossover distortion while also preventing premature wear to the power tubes. The hotter the bias the more linear the response. However too much bias and there's the danger of the tubes momentarily operating outside the SOA which shortens tube life. Even if you stay within the SOA if you operate near the limits you'll shorten tube life. If you overmatch the transformer you move the load line and increase the SOA margin so you can increase the bias.

The Axe-Fx is immune to tube wear so there is no danger in running the bias hot if you like that sound. However the hotter the bias the less dynamic the response becomes. Also some people like a bit of crossover distortion. Legend has it that EVH liked his amps biased cold. Whether that was because of the added dynamics or the extra grit due to crossover distortion is unknown.

As always the correct answer is what sounds best." [https://forum.fractalaudio.com/threads/grid-bias-value.178012/post-2168640]
</blockquote>

<blockquote>
"The question is which amp? A 1968 100W Plexi with over 500V on the plates or a 50 watter with around 360V on the plates? The response of those two amps will be completely different at the same quiescent dissipation due to the different plate voltages. The 100W amp will require around 35 mA for 70% dissipation. The 50W amp will require 48 mA. Since the transconductance of a tube is fairly independent of the plate voltage the 50W amp will be operating in a much more linear region. However, it will clip the grids sooner. If you load up, say, a 1959SLP model in the Axe-Fx you'll notice the bias is lower than the 50W versions. This is why. This is also why a lot of people prefer the 50W Plexis.

Then we need to ask what type and brand of power tubes? NOS? The response of the tubes is dependent upon the exponent in the tube equation. The original Childs-Langmuir law says that the exponent is 1.5 but real tubes exhibit an exponent somewhere between 1.2 and 1.5. The greater the exponent the less linear the response.

Finally we need to ask what is the output transformer primary impedance. Is it 4K per pair? Is it 3.6K? Is it 3.2K? Primary impedance was all over the map in those days.

All these things interact. The hotter the bias the more linear the response, the higher the gain, the sooner the grids clip, etc. A good amp designer will balance all these things along with the transformer matching to get the desired response.

The correct answer is turn it up/down until it sounds how you want." [https://forum.fractalaudio.com/threads/grid-bias-value.178012/post-2168744]
</blockquote>

<blockquote>
"So-called Class-A amps (like the AC30) don't actually exhibit much power supply sag because, well, they're Class-A (or nearly). The tubes are biased hot so when one tube is conducting more the other is conducting less and the net supply current doesn't change much. Contrast this with Class-AB where when one tube conducts the other goes into cutoff causing a net increase in supply current and concomitant supply sag. What Class-A amps do exhibit is "cathode squish". The capacitor on the cathodes charges up and shifts the bias point. This reduces the gain and acts as a sort of compressor. It's a unique compression and the amp "opens up" at the same time and crossover distortion increases."[https://www.thegearpage.net/board/index.php?threads/does-this-sound-like-an-ac30-to-you.2325505/post-34009664]
</blockquote>

==POWER TUBE HARDNESS==

From the Owners Manual:
<blockquote>
(Owners Manual) “Selecting a Power Tube Type (above) loads the appropriate “knee voltage” for the selected power tubes. This voltage can be adjusted up or down using Power Tube Hardness. Higher values yield a lower knee voltage and more abrupt clipping and vice-versa.”
</blockquote>

<blockquote>
(firmware Ares 10.00) "Due to the changes in the power amp modeling algorithm the Power Tube Hardness parameter now behaves differently. Selecting a Power Tube Type loads the “knee voltage” for the power tubes and this voltage can be adjusted up or down using Power Tube Hardness. Higher values yield a lower knee voltage and more abrupt clipping and vice-versa. Existing presets will have Power Tube Hardness reset to 5.0 upon recall."
</blockquote>

Before firmware Ares 10.00, this controlled the hardness (shape) of the virtual power tube grid clipping. Higher values have a more abrupt transition into saturation. This parameter changes automatically when switching virtual power tubes.

Fractal Audio explains:
<blockquote>
"The hardness is tied to the tube type. I.e., if a model uses EL84s the default hardness will be 2. Different tube types will default to different hardness." [http://forum.fractalaudio.com/threads/fw-18-06-amps-automatically-set-to-power-amp-hardness-of-4-instead-of-3-medium.98572/#post-1182388]
</blockquote>

<blockquote>
"You can control the "shape" of the preamp and power amp distortion. The Preamp Hardness parameter controls the shape of the triode emulations. The lower the value the softer the distortion. The Power Amp Hardness controls the power amp clipping but that often is not noticeable because negative feedback around the power amp makes the distortion harder. Therefore you can make the power amp distortion softer by reducing Negative Feedback. A good example of this is a JCM800. A JCM800 has very hard preamp distortion (since there is no cathode bypass cap on the last stage) but has low negative feedback which softens the power amp distortion. The trick with that amp is to get the amp into the sweet spot by increasing the MV until you are getting some power amp distortion which softens the preamp distortion. Another factor which controls power amp hardness is Transformer Match. There are two primary distortion mechanisms in a power amp: grid clipping and plate clipping (PI clipping notwithstanding as this is only audible with a post-PI MV). Grid Clipping is extremely hard, almost a hard clipper (i.e. if(x>a) then x=a). Plate clipping is much softer. However most power amps are slightly undermatched which means the grids clip before the plates clip, but only at those frequencies where the speaker impedance is "nominal". At high frequencies (above 1kHz or so) the rising impedance of the speaker causes the plates to clip before the grids. At the low frequency resonance the plates also clip first. If you increase the transformer matching the plates will clip earlier and, since plate clipping is softer, the distortion will be softer. So turn up the Transformer Match and turn down Negative Feedback for softer power amp distortion." [http://forum.fractalaudio.com/threads/scratchy-sound-on-this-patch-same-for-you.100622/page-2#post-1207496]
</blockquote>

<blockquote>
(firmware Ares 6.01) "As you decrease Power Amp Hardness now the volume won't decrease, it'll just get smoother. I like reducing it on "Class A" amp types sometimes." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-6-01.151534/post-1803390]
</blockquote>

<blockquote>
"There are a two things that determine the smoothness of the power amp distortion:
# Power Amp Hardness. As you've discovered turning it down makes it smoother (obviously). The value controls the "kvb" of the tube model. It's the "knee voltage" for the plate. The formula for plate current is Ip = f(Vg1, Vg2) atan(Vp/kvb). The lower kvb the more abrupt the transition into clipping. Power Amp Hardness is the inverse of this normalized to the plate voltage.
# Negative Feedback. Negative feedback linearizes the power amp. At some point, though, the power amp then runs out of headroom and goes into clipping. The more negative feedback the more linear the response and the more abrupt the clipping. Less negative feedback, smoother clipping. 

I often turn P.A. Hardness down, usually between 3-4, because I like the smoother sound." [https://forum.fractalaudio.com/threads/power-amp-hardness.152582/post-1815292]
</blockquote>

<blockquote>
"There are parameters not exposed to the user that are changed. Hardness is a relative parameter. Specifically it's a multiplier on the tube's kvb. I.e., if the tube has a kvb of, say, 20, and you turn hardness to 10 the actual kvb becomes 5 (lower kvb equals "harder" response)." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-19-00.180535/post-2207828]
</blockquote>

<blockquote>
"Also depends on how hard the power amp is being driven. If the power amp isn't being driven into clipping then the type of tube doesn't make much difference. The key to a high-gain amp is getting the right blend of preamp and power amp distortion. Start with the MV low and dial in your tone. Then raise the MV until the headroom meter just starts to hit 0 dB. This is beginning of the "sweet spot". Experiment with higher/lower MV until you get the right blend of distortion and compression. Back off the preamp gain as necessary. Vintage amps got almost all their distortion from the power amp. Over the years designers added gain to the preamp. Modern amps get most of their distortion from the preamp but without a little power amp distortion things can sound flat and compressed. Preamp distortion isn't lively like power amp distortion." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-19-00.180535/post-2207848]
</blockquote>

<blockquote>
"The distortion of the Kemper is smoother than a real amp. You can replicate this by decreasing the Power Amp Hardness." [https://forum.fractalaudio.com/threads/axe-fx-iii-clean-amp-sounds-compared-to-kemper-cleans.151497/post-1804532]
</blockquote>

==POWER TUBE MISMATCH==

From the Owners Manual:
<blockquote>
“Use this to simulate a gain mismatch between the virtual push and pull power tubes. A value of zero represents perfectly matched tubes.”
</blockquote>

==POWER TUBE BIAS EXCURSION==

From the Owners Manual:
<Blockquote>
“Controls how much the grid bias shifts when the virtual power tube grids are overdriven."
</Blockquote>

<blockquote>
“The higher the value, the more the bias shifts when the virtual power tubes are overdriven. Bias excursion pushes a power amp from Class-AB operation towards Class-B operation, which can result in crossover distortion. A little goes a long way, but too much can lead to what is referred to as “blocking distortion” which can make an amp sound unpleasant.“
</blockquote>

Fractal Audio explains:
<blockquote>
"Bias excursion (in the power amp) occurs because the power tube grids forward conduct when the grid voltage is slightly greater than the cathode voltage. Now this isn't a problem by itself. However almost all tube amp designs use a capacitor coupled grid circuit. The phase inverter is coupled to the power tube grids via a capacitor. When the grid voltage exceeds the cathode voltage, which is typically zero volts in a fixed-bias topology, the grid will become forward-biased and look like a low resistance. This clamps the grid side of the coupling capacitor. This occurs when the phase inverter signal is large and swings toward the B+ supply. When the phase inverter signal swings the opposite direction the grid stops conducting and the capacitor is no longer clamped. However there is now excess charge on the capacitor. During the time the capacitor was clamped charge was building up on the phase inverter side. When the grid comes out of conduction that charge effectively reduces the power tube bias. For example, a typical 6L6 is biased around -50V. The clamping action would then push the bias voltage even more negative, say -75V. In some designs the the bias voltage can be reduced by nearly 100%! Since the bias voltage is shifted the phenomenon is referred to as "bias excursion". Like cathode squish, bias excursion pushes the power amp from Class-AB operation towards Class-B operation. As we know Class-B operation has lots of crossover distortion. Now this may seem bad but, in fact, there are positive attributes associated with bias excursion. When designed correctly bias excursion can actually help an amp sound more "open". This happens because as the bias shifts the gain of the power tubes decreases. This in turn prevents the power tube plates from saturating as easily. However too much bias excursion leads to what is referred to as "blocking distortion" which can make an amp sound farty and generally unpleasant. Blocking distortion occurs when the bias shifts so much that the tubes are basically shut off for a period of time. If the capacitor charges up rapidly but bleeds off slowly, combined with lots of excursion, this leads to blocking distortion. There are three associated parameters in the Axe-Fx II that allow you to alter the bias excursion behavior: Bias Excursion, Excursion Time and Recovery Time. Bias Excursion controls the amount of bias excursion. The higher the value the more the bias shifts when the virtual power tubes are overdriven. Excursion Time controls how rapidly the coupling capacitor charges when the virtual power tube grids are conducting. Recovery Time adjusts how quickly the excess charge bleeds off when the virtual grids are not conducting. Preamp tubes also exhibit bias excursion and too much of it can cause blocking distortion. Like power tube bias excursion, though, a little bit can help. The trick is getting the right amount." [https://forum.fractalaudio.com/threads/bias-excursion.99698/post-1195688]
</blockquote>

<blockquote>
(about blocking distortion) "Old Fenders are particularly prone to this. Reduce Bias Excursion to reduce at the expense of accuracy." [http://forum.fractalaudio.com/threads/is-there-something-wrong-does-this-sound-normal-odd-distortion.138302/#post-1640723]
</blockquote>

<blockquote>
"Blocking distortion occurs in older designs due to grid conduction. The grid gets forward biased which causes a net offset to develop on the coupling capacitor which, in turn, shifts the bias point. Modern designs incorporate various means of mitigating this (grid stoppers, for example). Some bias excursion is desirable though as without it the distortion can be "sterile". [http://forum.fractalaudio.com/threads/is-there-something-wrong-does-this-sound-normal-odd-distortion.138302/#post-1640780]
</blockquote>

<blockquote>
"Blocking distortion can be reduced by decreasing the Bias Excursion in the preamp." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-00-beta-3.148907/page-4#post-1764615]
</blockquote>

From the "Cygnus" amp modeling release notes:

<blockquote>
"The power amp bias algorithm is changed and the bias control works differently now. As with a real amp as you turn the bias down the gain also goes down. Typical values for bias are between 0.45 and 0.5 for fixed bias amps and 1.0 for cathode biased."
</blockquote>

Fractal Audio explains:

<blockquote>
"…Power tubes also exhibit bias excursion. Some bias excursion in the power amp can be desirable. If you design the power amp in such a fashion so as the tubes go into forward conduction as the plates are clipping this will effectively reduce the bias and lower the gain causing the amp to "open up". To much bias excursion can cause excessive blocking distortion AND crossover distortion…." [https://forum.fractalaudio.com/threads/rectifier-bias-excursion-time.179754/post-2194681]
</blockquote>

==POWER TUBE EXCURSION TIME + RECOVERY TIME==

From the Owners Manual:
<blockquote>
"These parameters are related to Pwr Tube Bias Excursion. They control how rapidly the coupling capacitor charges or bleeds off as the virtual power tube grids are conducting or not."
</blockquote>

==BIAS TREM FREQUENCY + DEPTH==

These are not supported on the AX8 and FM3.

From the Owners Manual:
<blockquote>
“These create true bias tremolo by varying the bias of the virtual power tubes. Bias Tremolo varies based on a multitude of variables including power amp settings, damping, bias parameters, and more. It is also “self-ducking” and decreases as you play harder. On some amp types, extreme bias depth can result in excessive crossover distortion. On other amps the amount of tremolo can vary greatly between loud and soft playing. All this, however, is part of the allure of bias tremolo as it results in a particularly organic sound. The sound of Bias Trem is available on the FM3 via the Tremolo/Pan block.”
</blockquote>

Bias Tremolo is a tremolo that’s built in the Amp block and is based on varying the bias of the virtual power tubes. The tremolo action is different from other types of tremolo and the amount of tremolo varies with a multitude of variables. Most importantly the tremolo is “self-ducking” and decreases at higher signal amplitudes. Bias tremolo is a somewhat crude tremolo circuit and its interaction with the power amp depends on many things including damping, bias, etc. On some amps high values of bias trem depth can result in excessive crossover distortion. On other amps the amount of tremolo can vary greatly between loud and soft playing. All this, however, is part of the allure of bias tremolo as it results in a particularly “organic” sound. Control of the bias tremolo is afforded by the Trem Freq and Trem Depth parameters. A modifier can be attached to Trem Depth to facilitate engaging and disengaging the tremolo via footswitch or for other applications.

If power amp modeling is disabled, Bias Tremolo won't work.

Bias Tremolo is also available as a type in the [[Tremolo/Panner block]] (firmware Ares).

Fractal Audio explains:
<blockquote>
"If the power tubes are being overdriven the bias tremolo can add lots of crossover distortion." [http://forum.fractalaudio.com/threads/info-on-the-new-bias-tremolo-feature-in-the-amp-block.67767/#post-833753]
</blockquote>

<blockquote>
"Bias trem doesn't work well with all amp models. It depends on the model and this is precisely why bias trem wasn't offered on every amp ever made. It works best on amps that are biased hotter and that don't have much gain. Even a Deluxe Reverb doesn't work that well with bias trem because the power amp overdrives too easily. That is why an actual Deluxe Reverb uses an optical trem instead." [http://forum.fractalaudio.com/threads/65-bassguy-sv-bass-citrus-bass-fas-bass-usa-bas-1-2-bias-trmolo-not-a-bug.87474/#post-1058577]
</blockquote>

<blockquote>
"Bias trem works by modulating the power tube grid bias. One of the side-effects is that the effect becomes less pronounced as you play harder which makes it basically "auto ducking". Also since it's modulating the bias it gives an almost Univibe like effect since the phase changes a bit too." [http://forum.fractalaudio.com/threads/patch-62-nuclear-tone-weird-tremolo-effect.122258/#post-1454602]
</blockquote>

<blockquote>
"Bias tremolo works by modulating the quiescent operating point of the power tubes. With a single-ended power amp with negative feedback the gain doesn't change much as you change the operating point, hence the tremolo effect is subtle. Bias tremolo works best on amps with little to no negative feedback." [http://forum.fractalaudio.com/threads/fw-q8-5f1-tweed-ec-4-scene-preset-vid-demo.126829/#post-1509387]
</blockquote>

<blockquote>
"Play harder and the effect is reduced. Just like a real bias trem because that's what it does, it modulates the power tube bias." [https://forum.fractalaudio.com/threads/can-the-origin-effects-revivaltrem-be-replicated.170499/post-2052388]
</blockquote>

About missing support for Bias Tremolo on the FM3:

<blockquote>
"Certain features were removed to allow the algorithms to run including the bias tremolo, input dynamics processing, and several other inauthentic enhancements." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-62#post-28446966]
</blockquote>

<blockquote>
"We removed all the superfluous stuff (bias tremolo, dynamic presence/depth, etc.) in order to get the core amp modeling to run on the slower processor." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-68#post-28450968]
</blockquote>

<blockquote>
"The Axe-Fx III contains various algorithms that allow you to enhance the amp modeling that don't exist on a real amp. I.e. dynamic presence/depth, input dynamic processing, etc. These were removed to allow the core amp modeling to run on the lower-powered processor." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-70#post-28454394]
</blockquote>

==CATHODE FOLLOWER COMPRESSION==

Also referred to as "Preamp Comp" or "CF Comp".

From the Owners Manual:
<blockquote>
"Sets the amount of compression in the virtual cathode follower. This interacts with other parameters listed in the Cathode Follower section of the Advanced page (Time, Ratio, etc.).”
</blockquote>

This sets the amount of cathode follower compression, and defaults to zero when the amp (model) doesn't have a cathode follower.

Fractal Audio explains:
<blockquote>
"Turning it up engages the cathode follower emulation. If the amp has no cathode follower the compression value will default to 0. This allows you to add a cathode follower to the amp, if desired." [https://forum.fractalaudio.com/threads/cathode-follower-compression.156241/post-1860500]
</blockquote>

<blockquote>
"The Compression knob in the Cathode Follower section controls the behavior of the preamp's cathode follower. Without getting too technical cathode followers are nonlinear compressors. They distort the signal and the distortion increases as more energy is input." [http://forum.fractalaudio.com/threads/tips-on-getting-rid-of-that-hifi-sound-1st-look-at-3.140533/#post-1665472]
</blockquote>

<blockquote>
"All the Fender models except the 59 Bassman and 5F8 Tweed don't have cathode followers." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-00-beta-3.148907/page-3#post-1764588 souce]
</blockquote>

==CATHODE FOLLOWER HARMONICS==

From the Owners Manual:
<blockquote>
"Simulates harmonics that occur naturally inside an amp as tubes interact. Higher values increase the interaction between virtual tubes, yielding “softer” distortion."
</blockquote>

==CATHODE FOLLOWER GRID CLIPPING==

From the Owners Manual:
<blockquote>
"Adjusts grid clipping in the cathode follower. Lower values reflect the softer response of classic British and American tubes like Mullard, Sylvania and RCA. Higher values simulate the response of modern Chinese and Russian tubes with more abrupt clipping."
</blockquote>

<blockquote>
(firmware Ares 5) “Grid Clipping” parameter has been added which allows the user to adjust the grid clipping in the cathode follower. The default value reflects the “softer” response of classic British and American tubes like Mullard, Sylvania and RCA. Higher values simulate the response of modern Chinese and Russian tubes with more abrupt clipping."
</blockquote>

Fractal Audio explains:
<blockquote>
"I personally like the Grid Clipping set low because it has the NOS tube vibe. High values remind me of JJ's and Chinese tubes which I'm not a particularly big fan." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-00-beta-3.148907/page-9#post-1764941]
</blockquote>

=Power Supply=

==SUPPLY SAG==

From the Owners Manual:
<blockquote>
"This controls virtual power amp dynamics. Higher settings simulate higher power supply impedance, and thus greater tube plate voltage “droop,” for a more compressed feel. This control interacts with the Master and will have little effect if the power amp is not being “pushed hard”. As Master is increased, the power amp draws more current from its power supply and the Supply Sag control will have more effect."
</blockquote>

<blockquote>"Sag is also dependent on Master Volume. The higher the MV, the more sag." [https://forum.fractalaudio.com/threads/can’t-nail-the-robben-ford-sound-and-i-know-exactly-why-help.199726/#post-2488659]</blockquote>

<blockquote>
(Quantum 2.0) "The power supply sag is now incredibly realistic and far superior to the "expander/compressor" techniques used in other products. Learning to adjust the pertinent parameters can make a good tone great. Supply Sag is the most fundamental of the power supply controls. It controls the virtual resistance of the AC input. In a real tube amp the supply sags due to a combination of power transformer resistance and rectifier resistance. Increasing Supply Sag increases this resistance and vice-versa. The higher the resistance the more the supply sags and the more bouncy and spongey the amp will feel. I like to increase Supply Sag a bit and reduce gain. You can monitor the virtual supply on the hardware by selecting the Supply Sag parameter. The gain reduction meter will display the supply voltage in dB relative to idle." [http://forum.fractalaudio.com/threads/quantum-2-00-tips-part-1.110275]
</blockquote>

<blockquote>
(Quantum 2.0) "For convenience the virtual power supply voltage (B+) can now be monitored on the PWR DYN tab of the amp block. When the Supply Sag control is selected the gain reduction meter will display the supply voltage in dB relative to the idle voltage."
</blockquote>

Sagging softens (squishes) the pick attack, coupled with a swelling rise in volume after the initial drop of the note.

High values of Sag along with low B+ Time Constant values can cause “ghost notes” when the supply type is AC (as in a real amp). Lower B+ Time Constant values will make the amp feel “faster” but too low can cause ghost notes.

Fractal Audio explains:
<blockquote>
"Ghost notes are intermodulation distortion between the power supply ripple and the audio. There are several ways to reduce it:
# Change the supply to DC. This will completely eliminate it as there will be no supply ripple.
# Reduce the supply sag. This will reduce the amount of ripple but also reduce the power amp compression due to supply sag.
# Increase the B+ time constant. This will also reduce the amount of ripple but slow the response of the supply." [https://forum.fractalaudio.com/threads/how-to-eliminate-ghost-notes.152478/post-1814089]
</blockquote>

<blockquote>
"Ghost notes are intermodulation products between the power supply and the note being played. Plexis often demonstrate this due to their fast power supplies (which yields more ripple). They're not harmonically related to the note being played. Some people find them undesirable, others find they add "complexity". Usually most audible on the G string in the middle of the fretboard. Many products do not accurately reproduce them or reproduce them at all." [https://www.thegearpage.net/board/index.php?threads/apartment-situation-kemper-or-fm3.2207095/post-31576395]
</blockquote>

<blockquote>
"Supply Sag models the power supply resistance. This includes the power transformer, rectifier and any other resistances before the filter caps. The higher the resistance, the more the supply droops when current is pulled from it by the power tubes. The more the supply droops, the spongier the feel." [http://forum.fractalaudio.com/threads/im-addicted-to-supply-sag.56648/#post-711961]
</blockquote>

In pre-Cygnus firmware, turning Supply Sag to zero disabled the power amp modeling in the Amp block in the preset. Cygnus firmware has a dedicated switch for this.

If the Power Amp Modeling switch is turned off, Master works as a simple volume, and Depth and Presence are deactivated.

Fractal Audio explains:
<blockquote>
"If you shut the power amp modeling off from the Global menu it is not exactly the same as turning it off in the Amp block. This is because the virtual power amp always runs. So if you shut the power amp modeling off from the Global menu the supply will still sag resulting in a more compressed response. If the Master is set high the sag can be quite pronounced." [http://forum.fractalaudio.com/threads/power-amp-sim-on-off-vs-sag-on-off-with-real-power-amp-behaviour-of-presence-control.121178/#post-1442553]
</blockquote>

<blockquote>(Cygnus) "With power amp modeling off the Presence control does nothing." [https://forum.fractalaudio.com/threads/modeling-questions.199009/post-2481687]</blockquote>

You use Supply Sag to simulate different rectifier types.

Fractal Audio explains:
<blockquote>
"Reduce to simulate solid-state, increase to simulate tube." [http://forum.fractalaudio.com/threads/rectifier-solidstate-vs-tube.102553/#post-1228660]
</blockquote>

Also read Aiken's White Paper '[http://www.aikenamps.com/index.php/what-is-sag What is "Sag"?]' for more information.

==B+ TIME CONSTANT==

From the Owners Manual:
<blockquote>
"This interacts with the Supply Sag control because it makes the virtual power supply response slower or faster. When the supply is fast the amp will sag rapidly accentuating the pick attack and compressing after. Most guitar players like this, but setting it too fast will cause excessive AC ripple and ghost notes. For convenience the virtual power supply voltage (B+) is shown as a meter on this page when the Supply Sag control is selected. (The meter shows dB, relative to the idle voltage.)"
</blockquote>

Fractal Audio explains:
<blockquote>
"B+ Time Constant is the time constant associated with the Supply Sag parameter. The power tubes draw current from the supply. The supply has a finite resistance. As the power tubes draw more current the supply voltage droops. The rate of change of the droop and recovery is dictated by the supply capacitance. The product of the resistance and capacitance is the time constant. It's typically around 10 ms. You can vary this using the B+ Time Constant parameter. It is not a simply compression though. As the supply sags, the headroom is reduced but many other things happen. One thing that happens is that the screen voltage droops. The screen voltage is derived from the B+. However the screen has it's own dynamic response, which is often 2nd-order since there is often a filter choke. If you listen carefully to the models with a filter choke you can hear the screen voltage "bounce" when you hit a power chord. The damping of the screen filter is not exposed to the user. When the screen voltage droops, the power tube gain decreases. It effectively shifts the bias point. There is quiescent draw from the supply as well. As you increase the bias (Power Tube Bias) the quiescent draw increases which decreases available headroom. The Axe-Fx II does not model all this stuff with compressors, like other products do. It actually uses a differential equation for the supply and the current from the power tubes. It then solves the equation at each sample instant to find the supply voltage and screen voltage." [http://forum.fractalaudio.com/threads/b-time-constant.46615/#post-608766]
</blockquote>

<blockquote>
"The effect of lower B+ is equivalent to increasing Transformer Match. A lower B+ means the plates clip sooner which is the same as increasing the turns ratio on the transformer. This is assuming that you rebias since typically lower the B+ affects the bias." [http://forum.fractalaudio.com/threads/is-there-a-parameter-to-manipulate-b-voltage-video-inside.60172/#post-751161]
</blockquote>

<blockquote>
"The attack comes first as things compress. Then the supply bounces due to a much slower time constant. Compression time constants are in the neighborhood of a few ms, B+ time constants are typically 10-20 ms. You can adjust these on the Advanced page. Many amp designers like a "fast" power supply but if you lower the B+ time constant too much you get ghost notes." [https://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-1-00-public-beta.103735/post-1245408]
</blockquote>

<blockquote>
"The higher the value the stiffer the power supply. This will result in less compression from the power amp. "Most" guitar players prefer a value around 10ms as it it accentuates the attack without excessive ghosting. It seems as though you prefer less attack so raising the value will accomplish that. Another option is to change the supply type to DC. This will eliminate any ghosting and give you a more "ideal" response. Most modelers use a DC power supply model but I've found that an AC supply model is key to achieving that last few percent of realism. The supply ripple is a big part of why old amps sound the way they do. Most guitar players actually like a percussive attack so that's why about 10ms has become a de-facto standard." [http://forum.fractalaudio.com/threads/i-had-a-b-time-constant-epiphany.106309/#post-1271768]
</blockquote>

<blockquote>
"High values of Sag along with low B+ Time Constant values can cause “ghost notes” when the supply type is AC (as in a real amp). Lower B+ Time Constant values will make the amp feel “faster” but too low can cause ghost notes."
</blockquote>

<blockquote>
"For convenience the virtual power supply voltage (B+) can now be monitored on the PWR DYN tab of the amp block. When the Supply Sag control is selected the gain reduction meter will display the supply voltage in dB relative to the idle voltage."
</blockquote>

<blockquote>
"B+ Time Constant controls the capacitance of the virtual power supply. The more capacitance the "slower" the supply and vice-versa. Most guitar players like a fast supply but too fast will cause excessive AC ripple and create ghost notes (although I think a little ghost note is cool). When the supply is fast it will sag rapidly accentuating the pick attack and compressing after. This parameter works in conjunction with Supply Sag parameter. The time constant remains constant so if you increase Supply Sag the virtual capacitance decreases." [http://forum.fractalaudio.com/threads/quantum-2-00-tips-part-1.110275]
</blockquote>

<blockquote>
[http://forum.fractalaudio.com/threads/ghost-notes.126903 Cliff's Tech Note about ghost notes]:

"A phenomenon present in some vintage amps is an artifact known as "ghost notes". Ghost notes are the result of intermodulation distortion between the note being played and ripple on the power supply. The ripple is at 120 Hz because the AC voltage is full-wave rectified. So there are frequency components of 120 Hz and its harmonics in the power supply. These frequency components mix with the note being played and create new tones that are not harmonically related to the note being played. Since it is intermodulation distortion, tones are created at the sum and difference frequencies. For example, if you play a D at the seventh fret on the G string this is 294 Hz. The intermodulation will create new tones at 294 - 120 = 174 Hz and 294 + 120 = 414 Hz. The harmonics of the note being played also factor in. The aforementioned D will also produce tones at multiples of 294 Hz and these mix with the 120 Hz and its harmonics. The G string above the 5th fret is most prone to this because of the harmonic spectrum of those notes. The amount of ripple on the supply is a function of the supply impedance. More capacitance and less resistance will reduce the ripple. Conversely less capacitance and/or more resistance will increase the ripple. You can adjust these values in the Axe-Fx using the Supply Sag and B+ Time Constant parameters. Supply Sag adjusts the virtual resistance of the power supply. B+ Time Constant adjusts the resulting time constant of the supply resistance and capacitance, i.e. as you increase the sag the time constant stays constant (capacitance decreases). To counter this increase B+ Time Constant. Old 100W Plexis exhibit this the most of any amp I've seen due to the high resistance of the power supply transformer. Our reference 100W Plexi has so much power supply resistance that the power supply sags up to 120V! This along with only 50 uF of power supply capacitance leads to prominent ghost notes."
</blockquote>

<blockquote>
"Ghost notes are intermodulation distortion between the power supply ripple and the audio. There are several ways to reduce it:
# Change the supply to DC. This will completely eliminate it as there will be no supply ripple.
# Reduce the supply sag. This will reduce the amount of ripple but also reduce the power amp compression due to supply sag.
# Increase the B+ time constant. This will also reduce the amount of ripple but slow the response of the supply." [https://forum.fractalaudio.com/threads/how-to-eliminate-ghost-notes.152478/post-1814089]
</blockquote>

<blockquote>
"Ghost notes are intermodulation products between the power supply and the note being played. Plexis often demonstrate this due to their fast power supplies (which yields more ripple). They're not harmonically related to the note being played. Some people find them undesirable, others find they add "complexity". Usually most audible on the G string in the middle of the fretboard. Many products do not accurately reproduce them or reproduce them at all." [https://www.thegearpage.net/board/index.php?threads/apartment-situation-kemper-or-fm3.2207095/post-31576395]
</blockquote>

==POWER TYPE==

From the Owners Manual:
<blockquote>
"These select between AC and DC virtual power supply types. AC rectification and resulting supply ripple are modeled, and the line frequency is also selectable. Note that as with a real tube amp, the AC Supply can cause “ghost notes” when Supply Sag is low and B+ Time Constant is high. Lower B+ Time Constant values will make the amp feel “faster,” but too low can also cause ghost notes."
</blockquote>

<blockquote>
(Axe-Fx II) "Amp block power supply modeling now models AC rectification and resulting supply ripple (if Pwr Supply Type is set to ‘AC’). The power supply type can be selected between AC and DC with the Pwr Supply Type parameter. The line frequency can be selected with the AC Line Freq parameter. Note that high values of Sag along with low B+ Time Constant values can cause “ghost notes” when the supply type is AC (as in a real amp). Lower B+ Time Constant values will make the amp feel “faster” but too low can cause ghost notes."
</blockquote>

This switches between virtual AC (Alternating Current) and DC (Direct Current).

AC LINE FREQUENCY is not the same parameter as AC LINE FREQUENCY in the unit's [[Setup menu|Global Settings menu]].

Fractal Audio explains:
<blockquote>
[http://forum.fractalaudio.com/threads/ghost-notes.126903 Cliff's Tech Note about ghost notes]:

"A phenomenon present in some vintage amps is an artifact known as "ghost notes". Ghost notes are the result of intermodulation distortion between the note being played and ripple on the power supply. The ripple is at 120 Hz because the AC voltage is full-wave rectified. So there are frequency components of 120 Hz and its harmonics in the power supply. These frequency components mix with the note being played and create new tones that are not harmonically related to the note being played. Since it is intermodulation distortion, tones are created at the sum and difference frequencies. For example, if you play a D at the seventh fret on the G string this is 294 Hz. The intermodulation will create new tones at 294 - 120 = 174 Hz and 294 + 120 = 414 Hz. The harmonics of the note being played also factor in. The aforementioned D will also produce tones at multiples of 294 Hz and these mix with the 120 Hz and its harmonics. The G string above the 5th fret is most prone to this because of the harmonic spectrum of those notes. The amount of ripple on the supply is a function of the supply impedance. More capacitance and less resistance will reduce the ripple. Conversely less capacitance and/or more resistance will increase the ripple. You can adjust these values in the Axe-Fx using the Supply Sag and B+ Time Constant parameters. Supply Sag adjusts the virtual resistance of the power supply. B+ Time Constant adjusts the resulting time constant of the supply resistance and capacitance, i.e. as you increase the sag the time constant stays constant (capacitance decreases). To counter this increase B+ Time Constant. Old 100W Plexis exhibit this the most of any amp I've seen due to the high resistance of the power supply transformer. Our reference 100W Plexi has so much power supply resistance that the power supply sags up to 120V! This along with only 50 uF of power supply capacitance leads to prominent ghost notes."
</blockquote>

<blockquote>
"The most notable thing would be the ghost notes. There is also a slight difference in feel." [http://forum.fractalaudio.com/threads/ac-power-frequency.67073/#post-826893]
</blockquote>

<blockquote>
"Those old amps make ghost notes. My 100W Plexi has some ghost notes that are louder than the fundamental. The easiest way to eliminate them (if you don't like/want them) is to simply set the Supply Type to DC. However, IMO, the ghost notes are a large part of the character of these designs and removing them isn't desirable. Don't over-analyze it. Recognize that certain designs produce ghost notes and embrace it." [http://forum.fractalaudio.com/threads/can-someone-check-this-out-jtm-45.70962/#post-870070]
</blockquote>

<blockquote>
"100 watters are usually worse because they have lighter filtering (50 uF vs. 100 uF) and draw more dynamic current." [http://forum.fractalaudio.com/threads/ac-vs-dc-power-supply-parameter-try-it.104471/#post-1250025]
</blockquote>

<blockquote>
(about the frequency) "One of the reason amps in Europe sound different than US." [http://forum.fractalaudio.com/threads/whats-the-advantage-of-ac-power-supply-type-and-ghost-notes.130281/#post-1545025]
</blockquote>

<blockquote>
"(...) Another option is to change the supply type to DC. This will eliminate any ghosting and give you a more "ideal" response. Most modelers use a DC power supply model but I've found that an AC supply model is key to achieving that last few percent of realism. The supply ripple is a big part of why old amps sound the way they do. Most guitar players actually like a percussive attack so that's why about 10ms has become a de-facto standard." [http://forum.fractalaudio.com/threads/i-had-a-b-time-constant-epiphany.106309/#post-1271768]
</blockquote>

<blockquote>
"So I was testing the next beta and selected the AC-20. Was hearing a lot of ghost notes compared to the old algorithm (in the debug build I can select between algorithms with a hidden parameter) and figured that couldn't be right. Hooked up the real AC-20 and, sure enough, ghost notes galore at the same settings." (...) "If you don't want authentic ghost notes set the Supply Type to DC." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-0-public-beta.154714/post-1840850]
</blockquote>

<blockquote>
"Ghost notes are intermodulation distortion between the power supply ripple and the audio. There are several ways to reduce it:
# Change the supply to DC. This will completely eliminate it as there will be no supply ripple.
# Reduce the supply sag. This will reduce the amount of ripple but also reduce the power amp compression due to supply sag.
# Increase the B+ time constant. This will also reduce the amount of ripple but slow the response of the supply." [https://forum.fractalaudio.com/threads/how-to-eliminate-ghost-notes.152478/post-1814089]
</blockquote>

<blockquote>
"Ghost notes are intermodulation products between the power supply and the note being played. Plexis often demonstrate this due to their fast power supplies (which yields more ripple). They're not harmonically related to the note being played. Some people find them undesirable, others find they add "complexity". Usually most audible on the G string in the middle of the fretboard. Many products do not accurately reproduce them or reproduce them at all." [https://www.thegearpage.net/board/index.php?threads/apartment-situation-kemper-or-fm3.2207095/post-31576395]
</blockquote>

==AC LINE FREQUENCY==

See [[#POWER_TYPE| Power Type]] for more information.

==VARIAC==

From the Owners Manual:
<blockquote>
"This sets the relative AC line voltage into the amp simulation. Volume varies greatly when a Variac is used with a real amp, but the virtual variac compensates for this."
</blockquote>

A Variac is said to be required to achieve VH's "Brown" sound. Try it at 75% with a Plexi.

Fractal Audio explains:
<blockquote>
"The whole amp voltage is reduced." [http://forum.fractalaudio.com/threads/preamp-bias.110726/page-2#post-1712822]
</blockquote>

<blockquote>
"The Spongy/Bold switch (on a Mesa) is basically a Variac." [http://forum.fractalaudio.com/threads/rectifier-solidstate-vs-tube.102553/#post-1228691]
</blockquote>

<blockquote>
"It's impossible to compensate exactly. Some manual adjustment of the volume may still be required." [http://forum.fractalaudio.com/threads/volume-changes-with-variac-setting.109951/#post-1316615]
</blockquote>

==SCREEN FREQUENCY + SCREEN Q==

From the Owners Manual:
<blockquote>
"These set the resonant frequency of the virtual power tubes’ screen filter, and the Q of that filter."
</blockquote>

=Speaker=

The parameters on this page shape the virtual speaker impedance curve and the resulting resonances in the virtual power amp. Amp and speaker interaction affects tone by causing an increase in power amp response at certain frequencies. Note that setting Negative Feedback greater than “0” flattens the effect of the response curve.

==LOW FREQUENCY + LOW FREQUENCY RESONANCE==

From the Owners Manual:
<blockquote>
"Guitar loudspeakers have strong low-frequency resonance. This shifts up slightly when the speaker is mounted in an enclosure. This resonance causes an increase in the power amplifier response due to the finite output impedance of the power amp."
</blockquote>

The default LF and HF Resonance settings in an amp model are based on the selected Speaker Impedance Curve in the Amp block (firmware Ares 11 and later). Before that firmware version, they were based on a typical guitar cabinet for the amp type.

Setting the Speaker Impedance Curve to "Resistive Load" is identical to turning off LF Resonance and HF Resonance. [https://www.thegearpage.net/board/index.php?threads/axe-fx-iii-and-power-station-2.2136319/post-30299688]

Fractal Audio explains:
<blockquote>
"The speaker tab is not an EQ. It allows you to adjust the impedance that the virtual speaker presents to the virtual power tubes. In most cases the resulting EQ is quite different than the impedance curve since negative feedback flattens the response. If you turn the damping all the way down then the EQ will be close to the impedance curve (but still influenced by the transformer)." [http://forum.fractalaudio.com/threads/amp-speaker-tab-versus-amp-graphic-eq.47917/#post-623896]
</blockquote>

<blockquote>
(before firmware Ares 11) "The default LF Resonance is based on the cab most likely to be used with that amp. For example, if you select a Twin Reverb model it will use the resonance data from the Twin Reverb amp that we used as the reference (we measured all the cabs as well as shooting IRs). Your 1960A cab probably has its resonance around 80 Hz so ideally you would want to do exactly what you did. The ultimate solution would be to measure the LF resonance but that requires special test equipment. I've found that you can usually find it by ear though. As you adjust the LF resonance you'll hear the cabinet sympathize. There is no way around this at the moment as no modeler can measure the impedance of a guitar cabinet (despite any claims to the contrary). Note that this is not applicable when using FRFR and IRs." [http://forum.fractalaudio.com/threads/fw10-amps-into-real-cab-astounding.66965/#post-825662]
</blockquote>

<blockquote>
(before firmware Ares 11) "The default values in the amp block are based on the measured impedance of the most commonly used speaker for the selected amp. If it is a combo amp then the values are derived from the speaker that was in the cabinet. Most people who capture IRs are unable to also capture impedance data." [https://forum.fractalaudio.com/threads/something-cool-ive-been-working-on.75794/post-927165]
</blockquote>

<blockquote>
(before firmware Ares 11) "The biggest source of inaccuracy in our modeling is the fact that the speaker impedance is unknown. For each model we assume an impedance based on the speaker that is likely to be used with the amp. Even then impedance will vary from speaker-to-speaker. The difference between the assumed impedance and the actual impedance is small but audible. Tone Matching will correct this error. The amp controls will still behave the same and match up with the actual amp well." [http://forum.fractalaudio.com/threads/tone-matching.142664/#post-1688589]
</blockquote>

<blockquote>
"The resonant frequency goes up when mounted in a cabinet. It doesn't need to be spot-on. If you are within 10% you'll be fine. If you want to be anal about it you can use an impedance analyzer. This is what we use: Dayton Audio DATS Dayton Audio Test System 390-806." [http://forum.fractalaudio.com/threads/speaker-tab-settings-in-amp-block-g12k100.68009/#post-836372]
</blockquote>

<blockquote>
"Most guitar speakers are roughly the same when it comes to the high-frequency reactive behavior. The impedance increases starting around 1 kHz and then increases at 3-4 dB/octave. This is due to the voice coil inductance. A pure inductance would increase at 6 dB/oct. but there are eddy current losses that make the voice coil look "semi-inductive". The Axe-Fx II models this with a high-order lossy inductor model. The low-frequency response of guitar speakers, however, varies greatly between speakers of different makes and models. This low-frequency response is a sharp resonance typically in the range of 50-150 Hz. The magnitude of this resonance varies from several to 20 times the nominal impedance. The impedance of a speaker influences the response of a tube amp since a tube power amp is essentially a transconductance amplifier. It creates a current for an applied voltage. This current in turn creates a voltage across the speaker terminals that is dependent upon the impedance of the speaker. Therefore the power amp will resonate at the resonant frequency of the speaker. This causes certain notes to become emphasized as they excite the resonant frequency. Negative feedback around the power amp will reduce the amount of resonance but not all amps use negative feedback (i.e. Vox). The increased voltage amplitude at the resonant frequency also causes the power amp to clip sooner at the resonant frequency. Think of it this way: if the power tubes are swinging, say, 200 V at the midrange frequencies, they will swing X times more at the resonant frequency where X is the ratio of the resonant impedance to the nominal impedance. So if the resonant impedance is 10 times the nominal impedance the power tubes will want to swing 2000 volts. This is impossible so they will clip. For high-gain tones this can cause the tone to sound muddy or feel spongy. For lower gain tones this can thicken the tone and make it feel, well, more spongy. Cabinet/speaker IR data does not contain the impedance information. The only way to obtain impedance data is to measure the current vs. voltage vs. frequency (despite what modeler advertising literature would like you to think). The Axe-Fx uses default values of LF Resonant frequency and impedance for each amp model. For models based on combo amps these values are derived from measurements of the actual amp's speaker. For models based on amp heads the values are based on measurements of the cabinet most likely to be used with that head. You can adjust the frequency and impedance to suit your taste. Reducing the impedance (Low Res) will reduce the bass response and can give tighter bass. Raising the impedance will increase the bass response and can give a fuller sound. Altering the frequency (Low Freq) will change the frequencies at which the power amp resonates and tuning this to the key you are playing in can be an effective strategy, e.g. set it to 82 Hz if playing in E. Don't be afraid to try drastic settings. Try turning Low Res all the way to zero. Compensate by adding some bass with the Bass knob or the EQ section. As I mentioned earlier the LF Resonance will cause the power amp to clip earlier than it will when amplifying midrange frequencies. Turning down the Master Volume will increase the headroom in the power amp and reduce this clipping. Furthermore the Transformer Match also influences when the power amp clips. So there is a relationship between LF Res, MV and Transformer Match. Many manufacturers publish impedance data for their speakers. Eminence and Jensen and probably others publish detailed impedance data. You can look at the impedance plots and set the resonance parameters to match (roughly). The Low Res parameter is indicated from 0 to 10 and sets the resonance in dB from 0 to 24 dB (dB is a ratio of powers so it's not really the proper units for this but that's semantics). For example, the Jensen P12N has resonant frequency of about 100 Hz so you would set Low Freq to 100 Hz. The impedance at this frequency is about 40 ohms. To get the Low Res amount use the formula (20 * log10(Zr/Rdc)) / 2.4 where Zr is the impedance at the resonant frequency and Rdc is the DC resistance. For this speaker Low Res is then (20 * log10(40/6.2)) / 2.4 = 6.7. A power amp isn't perfect though. Winding resistance in the output transformer increases Rdc, typically by a couple ohms. Therefore our above example would become (20 * log10(40/8.2)) / 2.4 = 5.7. The exact value isn't overly critical though and all this is subtle nuances. The resonance Q is a bit more difficult to calculate. It is derived from the bandwidth at the points where the impedance "gain" is the square root of the resonance impedance gain. IOW, if the impedance is, say, 10 times the nominal impedance then the bandwidth is given by the frequencies where the response is 3.16 times the nominal impedance. For our example the resonance gain is 5 (40 / 8 = 5). So the bandwidth is the frequencies at which the impedance equals sqrt(5) * 8 = 18. From the graph this is approximately 75 Hz and 130 Hz. Q is defined as f0 / bw so our resulting Q is 100/60 = 1.67. Most speakers have a Q of around 2.0 or so. Again the exact value isn't overly critical and don't be afraid to try extreme settings (you can't break anything). Finally, just because real speakers behave like this doesn't mean we have to adhere to this behavior. Perhaps a better speaker has no resonance (Low and High Res are zero), or maybe the Q is a lot lower or higher. In our virtual world we can design a speaker that is impossible to construct in the physical universe. tl;dr version: Mess with Low Freq and Res if you want, or not." [https://forum.fractalaudio.com/threads/about-speaker-lf-resonance.78003]
</blockquote>

<blockquote>
"The speaker page is the impedance vs. frequency. For a guitar amp with no negative feedback the voltage frequency response of the power amp will very closely match this since the power amp is basically a current source (V = I * Z). There will a slight reduction in the peaks as the output impedance isn't infinite but it is very high and will therefore be very close." [http://forum.fractalaudio.com/threads/1-1-let-s-talk-a-b-testing-actual-amps-to-their-axe-fx-ii-counterparts.79701/page-4#post-970197]
</blockquote>

<blockquote>
"LF: in general the Q is between 2 and 2.5. The Hi Freq is usually between 1 and 1.5 kHz. Hi Freq sets the critical frequency (or corner frequency) of the inductive portion of the loudspeaker's response. The critical frequency is the frequency at which the reactive component of the impedance is equal to the resistive component. This is found by fc = R/(2*pi*L). For a typical speaker R is around 6 ohms and L is around 0.75 mH. Therefore fc = 1270. Jensens tend to have higher inductance so that would move this value down. Eminence speakers tend to have lower inductance so that would move this value up. Celestion does not publish their values so I used Eminence values when calculating the defaults. You'll notice the Marshally stuff has fc around 1500 which is consistent with a typical Eminence copy of a Greenback. => You cannot obtain speaker impedance via audio stimulus and microphone measurement. Impedance is defined as voltage divided by current so you need to measure the current vs. applied voltage across the frequency range of interest. I have the equipment to do it, and have measured many speakers, but the average person do esn't have the equipment nor the knowledge to use the data. The influence of speaker impedance is generally not that great. The exception are amps with no negative feedback. In these cases the speaker impedance has a much more pronounced effect on the overall response. These amps include Vox, Matchless and most other "Class-A" designs. As soon as you add negative feedback the response flattens considerably. However... Presence and Depth reduce negative feedback so if you dial significant amounts of those in then the speaker impedance becomes a factor again. All-in-all you only have to be in the ballpark. 1500 Hz is a good starting point for Hi Freq. Adjust up or down slightly by ear. I don't believe that 3000 Hz is accurate. I've never seen a speaker that would have the corner frequency that far out. => As I explained a few posts up I wouldn't set Hi Freq outside the range of 1.0 to 1.6 kHz. Vibroverb model is an exception (800 Hz) since it had a more voice coil inductance. => I call it critical frequency since it is similar to the critical or corner frequency of a filter. I had to come up with some way of setting the loudspeaker inductance relative to the resistance. Frequency seemed to make more sense. I thought about an inductance parameter but figured that would be too nebulous. At the default settings the impedance rise of the simulated voice coil matches very close with published data. I have overlaid the modeled impedance curve with published data and it is a very good fit. For example, take the JCM800 model. The graph on the SPKR page has a scale of +20 dB at the top. Look at the response at 2kHz. It's roughly 1/4 of full-scale which equates to 5 dB. If we look at the impedance curve for a typical 8-ohm speaker we see that the impedance at 2 kHz is roughly 13 ohms. For a 6.5 ohm voice coil (typical) this means that the voltage at the speaker is 6 dB higher at 2 kHz. Pretty darn close to what the graph is showing. While there is no high-frequency resonance in the speaker itself, a resonance IS formed due to the winding capacitance of the transformer. This capacitance resonates with the voice-coil inductance. => The negative feedback is set in the Advanced menu. The SPKR page only sets the impedance curve of the speaker/OT combo. The values chosen are prototypical for the speaker used with the modeled amp. You should not need to vary these parameters much IMO. I only ever vary Low Freq and High Freq. Whenever I'm matching an amp I adjust Low Freq to match the resonance of my reference cabinet. I occasionally vary Hi Freq to get more or less midrange bite." [https://forum.fractalaudio.com/threads/v6-firmware-time-to-release-the-monster-speaker-resonance-page.55045/page-18#post-704035]
</blockquote>

<blockquote>
"Negative feedback does not affect the speaker impedance. Speaker impedance is an independent variable. The default values are based on the speaker cabinet most commonly used with the amp. In the case of a combo it's the internal speaker. For heads it's the mating cabinet, if one. A typical speaker has a low-frequency resonance with some frequency, Q and magnitude. The Q is typically around 2, frequency around 100 and magnitude around 12 dB. These values are dependent upon the speaker construction and, to a lesser extent, the cabinet. The voice coil inductance causes the impedance to increase at high frequencies. Unlike a pure inductance which would increase at 6 dB/octave, voice coil inductance is semi-inductive and typically increases at 3-4 dB/octave. The "break" frequency is dependent upon the actual inductance and is adjustable. The Axe-Fx is unique in that it lets you adjust these values. Most products just use a fixed curve." [http://forum.fractalaudio.com/threads/the-speaker-page.108172/page-2#post-1295724]
</blockquote>

<blockquote>
"The voltage at the output of a tube amp is a function of the speaker's impedance curve. The impedance curve is set in the SPKR tab of the amp block. Real speakers respond to the VOLTAGE at their terminals, not the current. The amp block creates a virtual voltage which is a function of the amp model and the impedance curve. The cab block uses IRs which represent the measured sound from the speaker vs. an applied voltage at the speaker terminals. The aforementioned virtual voltage is sent to the cab block which then produces an audio signal by convolving the virtual voltage data with the IR. As I said in my previous post the IR is largely independent of it's impedance curve. The impedance curve can then be seen as just another tone and feel shaping tool. Bass too prominent? Turn down LF Resonance. Want more midrange? Lower HF Res Freq. The degree to which the impedance curve affects the output of the amp block is a function of the power tube type and the amount of negative feedback. The less negative feedback the more the impedance curve influences the output. Since Presence and Depth work by reducing negative feedback at high and low frequencies respectively, increasing them will also increase the influence of the impedance curve at those frequencies. The dynamic impedance of the power tubes also affects the output. A power triode, for example, has a much lower plate impedance than a tetrode or pentode and, therefore, the output will be mostly independent of the speaker impedance." [http://forum.fractalaudio.com/threads/the-speaker-page.108172/#post-1295117]
</blockquote>

<blockquote>
"You can simulate changing power tubes in the Axe-Fx by simply increasing or decreasing the LF and HF resonance values." [http://forum.fractalaudio.com/threads/why-power-tubes-sound-different.79962]
</blockquote>

<blockquote>
"The speaker resonance is NOT proportional to the master volume level in the real world. The speaker impedance curve does change under drive level (at the speaker terminals) and that is modeled but the amount of change is very small. The Axe-Fx III is extremely accurate in its modeling, especially the power amp modeling as that is where much of the magic happens. This has been proven time and time again in controlled studies. We compare the models to the amps at levels from barely audible to ear bleeding using measurement equipment as well as listening tests and blind A/B evaluations. In a loudspeaker the resonances do change a bit vs. applied voltage but the effect is subtle. The Axe-Fx III models this (it's the Speaker Compliance parameter). For all intents and purposes though it's pretty much a static network as the parameter shift only occurs at large excursion values which only occur at very low frequencies (excursion is the integral of applied voltage)." [https://forum.fractalaudio.com/threads/speaker-resonance-pa-equalization-tied-to-master-volume-level.155270]
</blockquote>

When using a solid-state power amp with a traditional guitar cab, finetuning LFR can get you better results.

Fractal Audio explains:
<blockquote>
"There are certain aspects that simply can't be modeled and require user intervention. For example, a speaker has a low-frequency resonance. A tube amp will create a higher output at that resonant frequency. The Axe-Fx has no way of knowing what that resonant frequency is and defaults to a value that is common for the speakers that are typically used with that amp. However, if you drive that speaker through a solid-state amp you won't excite the resonance unless you adjust the Speaker Resonant Frequency to match it." [http://forum.fractalaudio.com/threads/axe-fx-accuracy-issues.31759/page-2#post-449782]
</blockquote>

<blockquote>
"One way to find the SRF is to put a Filter block after the amp block. Set the type to Peaking, Q to 5 or so and Gain to 10 dB. Start with a Freq. of 50 Hz. Play some chugga-chugga and slowly adjust the Freq. until you hear and feel the cabinet resonate. Make a note of the frequency. Remove the filter block and set the amp block SRF to match. 4x12s typically have an SRF of between 80 and 120. Open back cabs are typically a bit lower." [http://forum.fractalaudio.com/threads/walkthrough-dialing-in-amps-on-the-axe-fx.31775/page-2#post-450458]
</blockquote>

<blockquote>
"This post is aimed at those who use a solid-state power amp into a conventional guitar cab. As is described in the post "About Speaker LF Resonance" a guitar cabinet has an impedance resonance in the low frequencies. This typically falls in the range of 50 to 100 Hz. A tube amp, being essentially a current source, will have a voltage output that follows the impedance curve. Speakers, being electromotive devices, respond to applied electromotive force (EMF) which we know as voltage. A solid-state power amp is a voltage amplifier and, hence, will not be influenced by the impedance of the speaker. When using a solid-state power amp into a conventional guitar cabinet the experience will be different if the simulated speaker in the Axe-Fx II is not adjusted to match the actual speaker. Whether or not this is important is up to the individual but I imagine a lot of the posts about "in-the-room using power amp and cab is not the same" are due to this. Unfortunately the Axe-Fx II cannot measure the speaker impedance characteristics as it is not directly connected to the speaker. No device can measure the speaker impedance without being directly connected to the speaker, despite what their marketing claims may infer (cough, ahem...), since impedance is, by definition, V/I and we cannot measure these unless connected to the speaker terminals. The only truly accurate way to set the simulated speaker is to measure the speaker being used with an impedance measuring device. These can be had relatively inexpensively in the form of the Woofer Tester 3 (from Dayton Audio IIRC). You can also make your own using a small value resistor (0.1 ohms or so) in series with you power amp and measure the voltage across the resistor. The next best method would be to estimate the impedance using published data from the speaker manufacturer. If the make and model are known the data may be available. Add approximately 10% to the published resonance frequency if the speaker is in a sealed box. The worst method, and the subject of some contention, is finding the resonance by "feel". No power amp has perfect damping. If you put a sine wave (use the Synth block) into the speaker you may be able to observe or feel the resonant frequency. The cone will have increased excursion at this frequency. Of course you may just be feeling the room resonance. I have used this technique successfully on several speakers but it takes practice. The main drawback is that the magnitude of the resonance is unknown. The Axe-Fx II's Low Res parameter is displayed in dimensionless units from 0 to 10. Each unit corresponds to 2.4 dB of impedance "gain". We define this as a gain since the our current source power amp will experience a voltage gain. This is relative to the DC resistance of the speaker. For example, if the speaker's resistance is 6 ohms and the impedance at resonance is 60 ohms then our impedance gain would be 20*log10(60/6) = 20 dB. Dividing by 2.4 gives a Low Res value of 8.3. Since a tube amp isn't a perfect current source these values should be reduced slightly. The exact value of the Q isn't too important. About 2.0 is a good starting point. Adjust up or down to taste. If you are anal more information is in the aforementioned post about deriving the value of Q. Once the simulated speaker is set correctly you may notice a difference in low-frequency behavior and pick attack." [https://forum.fractalaudio.com/threads/about-matching-your-cabinets-resonant-frequency.79816/]
</blockquote>

<blockquote>
(answering: "once I know what frequency to pick for my cab, and roughly which amount and Q to use, is it ok and expected to use the same settings for every amp model?"):

"Yes, keep the same settings for all models." [http://forum.fractalaudio.com/threads/clarification-of-lf-resonance-with-real-cab-speaker-tab.91139/#post-1097466]
</blockquote>

Firmware 22 and later for the Axe-Fx III enable automatic adjustment of the Speaker Impedance Curve in the Amp block when selecting a "dyna-cab" in the Cab block:

<blockquote>"The Amp block now features “Auto Dyna-Cab Impedance”. When set to ON the speaker impedance curve of the Amp block will follow the Cabinet Type in the first mixer slot of the associated Cabinet block. I.e., if the Cab Type in the first mixer slot of Cabinet 1 is, say, 4x12 5153 and the Mode is Dyna- Cab then Amp 1’s speaker impedance will automatically be set to 4x12 5153." </blockquote>

==HIGH FREQUENCY + HIGH FREQUENCY RESONANCE + SLOPE==

See [[#LOW_FREQUENCY_.2B_LOW_FREQUENCY_RESONANCE|Low Frequency Resonance]] (above).

From the Owners Manual:
<blockquote>
"A loudspeaker voice-coil presents an inductive load to the power amp at high frequencies. This inductive load, in conjunction with the output transformer capacitance, creates a high-frequency resonance at the specified frequency.""
</blockquote>

<blockquote>
"High Frequency Slope allows fine adjustment of the high-frequency impedance of the virtual voice coil (which affects the slope of the impedance curve). A speaker voice coil is “semi-inductive” due to eddy current losses in the motor. This presents an impedance to the power amp that is neither fully inductive nor fully resistive. The amount of resistive loss varies by brand and type. Reducing Slope simulates a speaker that is less inductive, increasing Slope simulates a speaker that is more inductive. Typical speakers range from 3.0 to 4.5 with the median being about 3.7. Lower values yield greater midrange while higher values are more scooped and sizzly."
</blockquote>

Fractal Audio explains:
<blockquote>
"The HF Resonance Frequency is the "corner frequency" of the voice coil inductance. As this inductance isn't a pure inductance due to eddy currents the calculation is a bit complex however it is roughly equal to: fc = R / (2 * PI * L), where R is the voice coil resistance and L is the inductance. A typical voice coil has R = 7 and L = 1 mH. This yields: fc = 7 / 6.28e-3 = 1100 Hz. Most voice coils are a bit lower inductance than this. The typical range for fc is 1200 - 1500 Hz." [https://forum.fractalaudio.com/threads/i-found-your-missing-high-end.155291/post-1848224]
</blockquote>

<blockquote>
"Most guitar speakers are roughly the same when it comes to the high-frequency reactive behavior. The impedance increases starting around 1 kHz and then increases at 3-4 dB/octave. This is due to the voice coil inductance. A pure inductance would increase at 6 dB/oct. but there are eddy current losses that make the voice coil look "semi-inductive". The Axe-Fx II models this with a high-order lossy inductor model. The low-frequency response of guitar speakers, however, varies greatly between speakers of different makes and models. This low-frequency response is a sharp resonance typically in the range of 50-150 Hz. The magnitude of this resonance varies from several to 20 times the nominal impedance. The impedance of a speaker influences the response of a tube amp since a tube power amp is essentially a transconductance amplifier. It creates a current for an applied voltage. This current in turn creates a voltage across the speaker terminals that is dependent upon the impedance of the speaker. Therefore the power amp will resonate at the resonant frequency of the speaker. This causes certain notes to become emphasized as they excite the resonant frequency. Negative feedback around the power amp will reduce the amount of resonance but not all amps use negative feedback (i.e. Vox). The increased voltage amplitude at the resonant frequency also causes the power amp to clip sooner at the resonant frequency. Think of it this way: if the power tubes are swinging, say, 200 V at the midrange frequencies, they will swing X times more at the resonant frequency where X is the ratio of the resonant impedance to the nominal impedance. So if the resonant impedance is 10 times the nominal impedance the power tubes will want to swing 2000 volts. This is impossible so they will clip. For high-gain tones this can cause the tone to sound muddy or feel spongy. For lower gain tones this can thicken the tone and make it feel, well, more spongy. Cabinet/speaker IR data does not contain the impedance information. The only way to obtain impedance data is to measure the current vs. voltage vs. frequency (despite what modeler advertising literature would like you to think). The Axe-Fx uses default values of LF Resonant frequency and impedance for each amp model. For models based on combo amps these values are derived from measurements of the actual amp's speaker. For models based on amp heads the values are based on measurements of the cabinet most likely to be used with that head. You can adjust the frequency and impedance to suit your taste. Reducing the impedance (Low Res) will reduce the bass response and can give tighter bass. Raising the impedance will increase the bass response and can give a fuller sound. Altering the frequency (Low Freq) will change the frequencies at which the power amp resonates and tuning this to the key you are playing in can be an effective strategy, e.g. set it to 82 Hz if playing in E. Don't be afraid to try drastic settings. Try turning Low Res all the way to zero. Compensate by adding some bass with the Bass knob or the EQ section. As I mentioned earlier the LF Resonance will cause the power amp to clip earlier than it will when amplifying midrange frequencies. Turning down the Master Volume will increase the headroom in the power amp and reduce this clipping. Furthermore the Transformer Match also influences when the power amp clips. So there is a relationship between LF Res, MV and Transformer Match. Many manufacturers publish impedance data for their speakers. Eminence and Jensen and probably others publish detailed impedance data. You can look at the impedance plots and set the resonance parameters to match (roughly). The Low Res parameter is indicated from 0 to 10 and sets the resonance in dB from 0 to 24 dB (dB is a ratio of powers so it's not really the proper units for this but that's semantics). For example, the Jensen P12N has resonant frequency of about 100 Hz so you would set Low Freq to 100 Hz. The impedance at this frequency is about 40 ohms. To get the Low Res amount use the formula (20 * log10(Zr/Rdc)) / 2.4 where Zr is the impedance at the resonant frequency and Rdc is the DC resistance. For this speaker Low Res is then (20 * log10(40/6.2)) / 2.4 = 6.7. A power amp isn't perfect though. Winding resistance in the output transformer increases Rdc, typically by a couple ohms. Therefore our above example would become (20 * log10(40/8.2)) / 2.4 = 5.7. The exact value isn't overly critical though and all this is subtle nuances. The resonance Q is a bit more difficult to calculate. It is derived from the bandwidth at the points where the impedance "gain" is the square root of the resonance impedance gain. IOW, if the impedance is, say, 10 times the nominal impedance then the bandwidth is given by the frequencies where the response is 3.16 times the nominal impedance. For our example the resonance gain is 5 (40 / 8 = 5). So the bandwidth is the frequencies at which the impedance equals sqrt(5) * 8 = 18. From the graph this is approximately 75 Hz and 130 Hz. Q is defined as f0 / bw so our resulting Q is 100/60 = 1.67. Most speakers have a Q of around 2.0 or so. Again the exact value isn't overly critical and don't be afraid to try extreme settings (you can't break anything). Finally, just because real speakers behave like this doesn't mean we have to adhere to this behavior. Perhaps a better speaker has no resonance (Low and High Res are zero), or maybe the Q is a lot lower or higher. In our virtual world we can design a speaker that is impossible to construct in the physical universe. tl;dr version: Mess with Low Freq and Res if you want, or not." [https://forum.fractalaudio.com/threads/about-speaker-lf-resonance.78003]
</blockquote>

<blockquote>
"LF: in general the Q is between 2 and 2.5. The Hi Freq is usually between 1 and 1.5 kHz. Hi Freq sets the critical frequency (or corner frequency) of the inductive portion of the loudspeaker's response. The critical frequency is the frequency at which the reactive component of the impedance is equal to the resistive component. This is found by fc = R/(2*pi*L). For a typical speaker R is around 6 ohms and L is around 0.75 mH. Therefore fc = 1270. Jensens tend to have higher inductance so that would move this value down. Eminence speakers tend to have lower inductance so that would move this value up. Celestion does not publish their values so I used Eminence values when calculating the defaults. You'll notice the Marshally stuff has fc around 1500 which is consistent with a typical Eminence copy of a Greenback. => You cannot obtain speaker impedance via audio stimulus and microphone measurement. Impedance is defined as voltage divided by current so you need to measure the current vs. applied voltage across the frequency range of interest. I have the equipment to do it, and have measured many speakers, but the average person do esn't have the equipment nor the knowledge to use the data. The influence of speaker impedance is generally not that great. The exception are amps with no negative feedback. In these cases the speaker impedance has a much more pronounced effect on the overall response. These amps include Vox, Matchless and most other "Class-A" designs. As soon as you add negative feedback the response flattens considerably. However... Presence and Depth reduce negative feedback so if you dial significant amounts of those in then the speaker impedance becomes a factor again. All-in-all you only have to be in the ballpark. 1500 Hz is a good starting point for Hi Freq. Adjust up or down slightly by ear. I don't believe that 3000 Hz is accurate. I've never seen a speaker that would have the corner frequency that far out. => As I explained a few posts up I wouldn't set Hi Freq outside the range of 1.0 to 1.6 kHz. Vibroverb model is an exception (800 Hz) since it had a more voice coil inductance. => I call it critical frequency since it is similar to the critical or corner frequency of a filter. I had to come up with some way of setting the loudspeaker inductance relative to the resistance. Frequency seemed to make more sense. I thought about an inductance parameter but figured that would be too nebulous. At the default settings the impedance rise of the simulated voice coil matches very close with published data. I have overlaid the modeled impedance curve with published data and it is a very good fit. For example, take the JCM800 model. The graph on the SPKR page has a scale of +20 dB at the top. Look at the response at 2kHz. It's roughly 1/4 of full-scale which equates to 5 dB. If we look at the impedance curve for a typical 8-ohm speaker we see that the impedance at 2 kHz is roughly 13 ohms. For a 6.5 ohm voice coil (typical) this means that the voltage at the speaker is 6 dB higher at 2 kHz. Pretty darn close to what the graph is showing. While there is no high-frequency resonance in the speaker itself, a resonance IS formed due to the winding capacitance of the transformer. This capacitance resonates with the voice-coil inductance. => The negative feedback is set in the Advanced menu. The SPKR page only sets the impedance curve of the speaker/OT combo. The values chosen are prototypical for the speaker used with the modeled amp. You should not need to vary these parameters much IMO. I only ever vary Low Freq and High Freq. Whenever I'm matching an amp I adjust Low Freq to match the resonance of my reference cabinet. I occasionally vary Hi Freq to get more or less midrange bite." [https://forum.fractalaudio.com/threads/v6-firmware-time-to-release-the-monster-speaker-resonance-page.55045/page-18#post-704035]
</blockquote>

<blockquote>
"In the SPKR page of the Amp block are various parameters. I've talked about low-frequency resonance in another post. In this post I will address high-frequency resonance. As with LF resonance the high output impedance of a tube power amp causes the frequency response to follow the impedance of the speaker. There are two primary components: LF resonance and a high-frequency boost. The HF boost is due to the inductance of the voice coil. At the frequency where the voice coil reactance is equal to its resistance the impedance will start to rise. If this were a "pure" inductance it would rise at 6 dB per octave. However eddy-current losses in the motor cause this inductance to be "semi-inductive" and the impedance typically rises between 3 and 4 dB per octave. Different brands and models of speakers behave differently. You can look at the spec sheet for a speaker to get an idea as to the behavior of the speaker. The formula for the break frequency is given by f = R / (2*pi*L). For example, if the voice coil inductance is 1 mH and the resistance is 7 ohms then the break frequency would be 7/(6.28*0.001) = 1.1 kHz. The Axe-Fx II allows you to adjust the virtual voice coil via the HI FREQ and HI RES parameters. The HI FREQ parameter sets the "break" frequency which is the frequency where the inductive reactance equals the voice coil resistance. For most speakers it is around 1000 Hz. It is lower for larger speakers and higher for smaller speakers usually. The HI RES parameter sets the rate at which the impedance increases. The default value of 5.83 is around 3.5 dB per octave. If you want a smoother sound you can increase HI FREQ and/or decrease HI RES. If you want more highs or "chime" you can decrease HI FREQ and/or increase HI RES. Experiment with different values to get a feel for the response. Note that the amount of feedback (Damping parameter) will influence the behavior of these controls. With no feedback (Damping = 0) the frequency response follows the impedance curve virtually 1-for-1. As Damping is increased the frequency response flattens and the impedance curve has less influence on the response. As with all things in the Axe-Fx, use your ears." [https://forum.fractalaudio.com/threads/about-hf-resonance.81121]
</blockquote>

<blockquote>
"HF Resonance is similar to the previous control but only changes the slope of the resonance. The default value is consistent with the typical “semi-inductance” of a speaker voice-coil. Varying this value will change the high-frequency load presented to the virtual power tubes."
</blockquote>

==XFORMER LOW + HIGH FREQUENCY (TRANSFORMER LF/HF)==

From the Owners Manual:
<blockquote>
"These set the output transformer bandwidth."
</blockquote>

<blockquote>
(firmware Cygnus 16.01) "The Transformer LF parameter effectively adjusts the transformer’s inductance. Increase this value to simulate a smaller transformer, decrease to simulate a larger transformer."
</blockquote>

Fractal Audio explains:
<blockquote>
"XFRMR LF sets the low frequency -3dB point of the output transformer. Most transformers actually have a very low -3dB point (contrary to internet wisdom) however their full-power -3dB point is significantly higher. The Xfrmr Drive control sets the full-power -3dB point." [http://forum.fractalaudio.com/threads/controlling-the-lows.96327/#post-1154831]
</blockquote>

Transformer is sometimes abbreviated to "XFRMR".

==SPEAKER IMPEDANCE CURVE==

From the Owners Manual:
<blockquote>
"Tucked away near the end of the advanced menu is this remarkable little parameter. It selects between 50+ high-order speaker impedance modeling curves. Changing the amp Type will load an appropriate curve automatically. The Cabinet Resonance parameter can be used to adjust the amount of cabinet resonance in the impedance curve, an effect made instantly more visible on the graph shown on the “Speaker” page of the amp block edit menu and in Axe-Edit III or FM3-Edit."
</blockquote>

<blockquote>
(firmware Ares 11) "Amp block now uses new high-order speaker impedance modeling. 52 speaker impedance models (and two LB-2 models) are included and can be selected using the Speaker Impedance Curve parameter (on the Advanced page). Selecting an amp model will load an appropriate default Speaker Impedance Curve for that amp model. The Cabinet Resonance parameter can be used to adjust the amount of cabinet resonance in the impedance curve."
</blockquote>

The Speaker Impedance Curve parameter is often abbreviated to SIC. It sets the desired impedance curve for the selected amp model. Together with the selected cab model (IR) in the Cab block, this parameter mainly affects "feel" and bass response.

You can choose from many provided curves. You can either choose a curve that authentically fits the selected cab model (IR), or another one that sounds and feels great.

Setting the Speaker Impedance Curve to "Resistive Load" is identical to turning off LF Resonance and HF Resonance. [https://www.thegearpage.net/board/index.php?threads/axe-fx-iii-and-power-station-2.2136319/post-30299688]

The parameter Cabinet Resonance on the Speaker page of the Amp block lets you set the desired amount of cabinet resonance in the curve (default: 100%).

Fractal Audio explains:

<blockquote>
"Firmware 11.0 introduces our new high-order speaker impedance modeling. We've curated the impedance data from nearly 50 cabinets. You'll now be able to select the impedance curve to use with an amp model (selecting an amp model loads the most appropriate curve for that model). Why is this important? When you look at speaker impedance curves they look pretty simple. However that data is obtained when the speaker is mounted on an infinite baffle. As soon as you mount the speaker in a cabinet that impedance data changes, sometimes quite radically. The modes of the cabinet introduce significant peaks and dips in the impedance due to the back EMF created. Some of the cabs we measured have deviations from the published curves by 4-5 dB or more. To understand why this happens the impedance of a speaker is dependent upon the acoustic load. In an infinite baffle the load is constant. Put the speaker in a box and the load is greater at some frequencies and lower at others because the sound waves bounce off the walls and constructively or destructively interfere with the motion of the speaker. For example, consider the sound emanating from the speaker and bouncing off the back wall of the cabinet. When the sound wave reaches the speaker it will either aid or oppose the motion of the speaker. If it aids the motion then the impedance will be lower and vice-versa." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-10-02.155004/post-1850592]
</blockquote>

<blockquote>
"The impedance has a nonlinear component but it is very small relative to the linear component. IOW the amplitude of the wave is proportional to speaker displacement so the impedance curve is relatively constant vs. applied voltage. The nonlinear effects occur as the voice coil moves out of the magnetic gap and this is already modeled." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-10-02.155004/post-1850628]
</blockquote>

<blockquote>
"A tube power amp is a transconductance amplifier, voltage in - current out. A speaker is a voltage transducer, voltage in - sound out. Since the power amp is driving current the voltage at the speaker is the current times the impedance of the speaker (Ohms law V = I*R). The voltage therefore is dependent upon the impedance. A solid-state power amp is a voltage amplifier, voltage in - voltage out. Since the power amp is driving voltage the voltage at the speaker is NOT dependent on the impedance of the speaker. When an IR is captured (correctly) it is done using a solid-state power amplifier so the effects of impedance do not influence the measurement. Some people try to use tube power amps to capture IRs. This is incorrect methodology. The Axe-Fx power amp simulation is a transconductance simulation. It uses a simulated speaker impedance to derive the output voltage that then drives the simulated cabinet (IR). Firmware 11.xx has 47 (and counting) speaker impedance curves that you can select that allow for different power amp transconductance responses. Moreover the impedance simulation is now a high-order network that simulates the perturbations in impedance due to cabinet resonance. If you are using a conventional guitar cab and solid-state power amp ideally you would want to know the impedance curve of the cabinet. This requires special test equipment although I'm working on a idea to use the outputs of the Axe-Fx directly along with a special cable to allow field measurements by users. At this time the impedance curve matching is a Matlab program though and requires some hand-tuning." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-11-00-public-beta.155500/post-1850920]
</blockquote>

<blockquote>"The graph shown is the resulting response of the SIC plus the response of the transformer." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-22-00-release.195047/page-22#post-2430996]</blockquote>

<blockquote>
"Choose an impedance curve that most closely matches the speaker you used." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-11-00-public-beta.155500/post-1850937]
</blockquote>

<blockquote>
"The Null curve simulates a purely resistive load. No real speaker exhibits this type of impedance curve. It's simply there for reference." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-11-00-public-beta.155500/post-1851632]
</blockquote>

<blockquote>
"The little spikes are due to reflections, both internal to the cabinet and external from the room. The sound bounces off things and when it arrives in phase or out of phase with the speaker it changes the impedance. Noise in the environment can also impact the measurement. Ideally the environment should be as quiet as possible." [https://forum.fractalaudio.com/threads/speaker-impedance-curve-measurements.155738/post-2148090]
</blockquote>

<blockquote>
"Air is very linear. The impedance curve changes, but not for those reasons. It changes because the amount of voice coil in the magnet gap changes as the speaker moves. When the speaker moves one way more windings are in the gap and vice-versa. This changes the effective voice coil inductance. Also, the low frequency resonance changes (slightly) as a function of displacement. This is due to the compliance of the suspension changing with displacement. Compliance also changes due to a change in Force Factor (B*l) which is a function of displacement. There are no nonlinear effects due to "chunking at higher volumes". The cab does not have "resistance". FWIW, the impedance curves in the Axe-Fx are not static. They are dynamic. You can vary the amount of impedance shift using the Speaker Compliance parameter." [https://forum.fractalaudio.com/threads/impedance-curves-are-my-new-go-to-for-tone-shaping.182195/post-2237264]
</blockquote>

<blockquote>"The response of a tube amp is dependent upon the speaker impedance. If you use a speaker with same impedance curve as the model then the response of the model will be very close to the real amp (component tolerances are still a factor). If your speaker's impedance curve is different then there will be audible differences. In the Amp block you can select different impedance curves. Switch through them and notice the difference in response, particularly in the bass. Our modeling is extremely accurate but matching a particular copy of an amp is limited to variables beyond our control like speaker impedance curve, component tolerances and design changes." [https://forum.fractalaudio.com/threads/fm3-firmware-version-6-01.191161/post-2375310]</blockquote>

<blockquote>"Amps with low amounts of negative feedback in the bass region are sensitive to the impedance curve. The 5153 is one of these amps due to its NFB circuit." [https://thegearforum.com/threads/evh-amp-vs-axe-fx-qc-and-tmp.3593/post-133163]</blockquote>

<blockquote>"The impedance curve MUST be in the amp block. A power tube is essentially a current source. So the output voltage of a tube amp is the current times the impedance. If the power amp is driven hard (and it usually is because that's where it sounds best) then the voltage will eventually clip. The lows and highs clip first because the impedance curve is sort of a bathtub shape. If the impedance curve is not in the amp block then the power amp cannot clip correctly. Negative feedback essentially flattens the impedance curve. So if the impedance curve isn't part of the amp block there's no way to flatten the curve depending upon the amp's negative impedance. The negative feedback is often shaped, i.e. Presence/Depth controls. The amount of signal fed back, however, is dependent upon the impedance curve because the output voltage is a function of the impedance curve. This results in a complex interaction between the impedance curve and the Presence/Depth controls. The power drawn from the power supply is a function of the impedance curve. The low frequencies and high frequencies clip earlier than the midrange so the midrange draws more power which results in more compression in the midrange. It's simply wrong to apply the impedance curve anywhere but in the amp block. Applying some generic impedance curve to IRs is crude and nowhere near to what a real amp does." [https://thegearforum.com/threads/fender-tone-master-pro.3286/page-182#post-145843]</blockquote>

<blockquote>"In a tube power amp the lows and highs distort first because they are boosted by the speaker impedance. This causes the sound to become more midrangey and focused. Then as the signal decays the sound becomes fuller and less midrangey. It's literally one of the most important things in the way a tube amp operates and is responsible for its unique and pleasing overdrive behavior and why they became the gold-standard. This is also what makes an AC30 so unique. AC30s have no negative feedback so the lows and highs are fully boosted by the speaker impedance. When you drive them hard they get focused. When you back off the volume the become full and chimey." [https://thegearforum.com/threads/fender-tone-master-pro.3286/page-184#post-145948]</blockquote>

Leon Todd explains this feature in [https://www.youtube.com/watch?v=wEgO5kE6FkU this video].

The Amp block in presets prior to firmware Ares 11 also relied on an impedance curve. A parameter in the [[Global Settings menu]] of the Axe-Fx III, FM3 and FM9 lets you decide to keep using the old values or update the preset to the newer specs. Then, when loading such a preset, the device either automatically selects the most fitting speaker impedance curve (you need to save the preset to make it permanent), or sticks with the "pre-11" impedance/resonance curve.

From the Owners Manual:
<blockquote>
(firmware Ares 11) "Setting Global “Update Pre-11.x Presets Spkr Imp Upon Load" parameter to YES will automatically update the Speaker Impedance Curve for the Amp blocks upon preset recall to use an appropriate Speaker Impedance Curve for that amp model. Setting the parameter to NO will leave existing presets unaffected. NOTE: Setting this to YES will also cause the EDITED LED to light indicating the preset has been modified."
</blockquote>

Firmware 18 for the Axe-Fx III (the FM9 and FM3 followed) also add the Speaker Impedance Curve parameter to the [[Global Settings menu]]. When set to DEFAULT the speaker impedance curve used when selecting an amp model is the default curve for that amp model, otherwise it is the selected curve. NOTE: this does not affect existing presets. The selected curve is used only when selecting a new amp model.

Firmware 22 and later for the Axe-Fx III enable automatic adjustment of the Speaker Impedance Curve in the Amp block when selecting a "dyna-cab" in the Cab block:

<blockquote>"The Amp block now features “Auto Dyna-Cab Impedance”. When set to ON the speaker impedance curve of the Amp block will follow the Cabinet Type in the first mixer slot of the associated Cabinet block. I.e., if the Cab Type in the first mixer slot of Cabinet 1 is, say, 4x12 5153 and the Mode is Dyna- Cab then Amp 1’s speaker impedance will automatically be set to 4x12 5153." </blockquote>

<blockquote>"All Dyna-Cabs have corresponding impedance curves that were taken from the actual cabs." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-22-00-release.195047/post-2431116]</blockquote>

===Speaker Impedance Curves list===

The current speaker impedance curves in the Amp block are listed below. The details are based on available information about the amps and cabs in Fractal Audio's possession. The information may be outdated.

# '''1x8 Champlifier''' — Fender Champ combo with 8" speaker
# '''1x10 Metro Blues''' — MESA Subway Blues combo with 10" Eminence Black Shadow
# '''1x10 Princetone''' — 1959 5F2-A Fender Tweed Princeton combo with 10" speaker
# '''1x10 Princetone Rev''' — blackface Fender Princeton Reverb combo with 10" speaker
# '''1x10 Princetone SF''' — silverface Fender Princeton combo with 10" speaker
# '''1x12 AC-20 DLX''' — Morgan AC20 Deluxe combo with 12" G12M75
# '''1x12 AST BV25''' — Swart Atomic Space Tone with 12" Mojotone BV-25m
# '''1x12 Brit G12H55''' — 1x12 cabinet with 12" Celestion G12H, low (bass) resonance (55 Hz)
# '''1x12 Brit G12H75''' — 1x12 cabinet with 12" Celestion G12H, high resonance (75 Hz)
# '''1x12 Brit G12M''' — 1x12 cabinet with 12" Celestion G12M (this curve is associated with the 1x12 Div13 CJ11 DynaCab)
# '''1x12 Brit G12T''' — 1x12 cabinet with 12" Celestion G12T (this curve is associated with the 1x12 G12T-100 DynaCab))
# '''1x12 Car Ambler''' — Carr Rambler combo with 12" speaker, probably Eminence Elsinore
# '''1x12 Class-A 15W''' — hand-wired 1x12 Vox AC15 reissue combo with 12" Alnico Blue
# '''1x12 Deluxe Oxford''' — Fender Deluxe Reverb combo with 12" Oxford
# '''1x12 Deluxe Tweed''' — 1957 Fender Tweed Deluxe combo with 12" speaker
# '''1x12 Deluxe Verb''' — Fender Deluxe Reverb combo with 12" speaker
# '''1x12 Deluxe Verb RI''' — reissue Fender Deluxe Reverb combo with 12" speaker (possibly Jensen C12-K) (this curve is associated with the 1x12 Deluxe Verb DynaCab)
# '''1x12 Dirty Shirley EV12L''' — Friedman Dirty Shirley combo or cabinet with 12" EV-12L
# '''1x12 G12T-75''' — 1x12 cabinet with 12" Celestion G12T-75
# '''1x12 Hot Kitty''' — Bad Cat Hot Cat 30 combo with 12" custom Celestion V30
# '''1x12 Jr Blues''' — Fender Blues Junior with 12" speaker (Eminence or Jensen?)
# '''1x12 Tweed Alnico Blue''' — Fender Tweed Deluxe with 12" Celestion Alnico Blue
# '''1x12 Tweed C12Q''' — Fender Tweed Deluxe with 12" Jensen C12Q
# '''1x12 Tweed Emmi''' — Victoria 20112 Deluxe Tweed combo with 12" Eminence
# '''1x12 USA Ext EV12''' — MESA extension speaker cabinet with 12" EV-12L
# '''1x12 V30''' — 1x12 cabinet with 12" Celestion V30
# '''1x12 Vibrato Lux''' — Fender Vibrolux combo with 12" speaker
# '''1x15 Heart Key''' — Harte HyDrive bass cabinet with 15" HyDrive speaker
# '''1x15 Portabass''' — Ampeg Portaflex bass cabinet with 15" Eminence
# '''1x15 Vibrato Verb''' — blackface Fender Vibroverb combo with 15" JBL D130
# '''2x10 Heart Key''' — Harte bass combo with two 10" HyDrive paper/aluminum cone speakers
# '''2x10 Super''' — brownface Fender Super combo with two 10" speakers
# '''2x10 Vibrato Lux''' — Fender Vibrolux combo with two 10" speakers
# '''2x12 Band Commander SRO''' — Fender Bandmaster with two 12" EV-SRO speakers
# '''2x12 Bassbuster''' — Fender BassBreaker cabinet with two Fane F70 speakers picture]
# '''2x12 Bassguy''' — blackface Fender Bassman combo or cabinet with two 12" speakers
# '''2x12 Class-A 30W''' — hand-wired VOX AC30 with two 12" speakers
# '''2x12 Class-A 30W Silver''' — VOX AC30 with two 12" Alnico Silvers (this curve is associated with the 2x12 Class-A 30W DynaCab)
# '''2x12 Class-A Greenback''' — VOX AC30 with two 12" Celestion G12M greenbacks
# '''2x12 Dizzy RV''' — Diezel rear-loaded cabinet with two 12" speakers
# '''2x12 Double Verb''' — blackface Fender Twin Reverb combo with two 12" Jensens (this curve is associated with the 2x12 Double Verb DynaCab)
# '''2x12 Double Verb SF''' — silverface Fender Twin Reverb combo with two 12" Jensens
# '''2x12 Godzilla''' — York Audio's Zilla Fatboy cabinet with 12" V30 and Creamback H75 speakers
# '''2x12 Guy Tron Alnico Blue''' — Guytron cabinet with two 12" Alnico Blues
# '''2x12 Jazz 120''' — Roland JC-120 combo with two 12" Roland Alnico speakers
# '''2x12 Lead 80''' — cabinet with two 12" Classic Lead 80 speakers
# '''2x12 Match Chief''' — Matchless Chieftain combo with two 12" Celestion G12H75 speakers
# '''2x12 USA C90 Open Back — Mesa open back cabinet with two 12" C90 speakers
# '''2x12 Recto''' — compact MESA Rectifier cabinet with two 12" speakers
# '''2x12 Two Stone 1265''' — Two-Rock cabinet with two Celestion G12-65 speakers
# '''2x12 TX Star''' — MESA Lone Star 2x12 combo or cabinet with two 12" speakers (probably Celestion C90 aka Black Shadow)
# '''4x10 Bassguy''' — Fender Bassman cabinet with four 10" speakers
# '''4x10 Bassguy RI''' — reissue 1959 Fender 5F6-A narrow-panel Tweed Bassman cabinet with four 10" Jensen P10s
# '''4x10 Brit JM45''' — Marshall JTM-45 cabinet with four 10" speakers
# '''4x10 Super Verb''' — Fender Super Reverb cabinet with four 10" speakers
# '''4x10 SV Bass''' — SVT bass cabinet with four 10" SVT speakers
# '''4x12 1960BV''' — 1999 Marshall 1960bv cabinet with original Celestion Marshall G12 Vintage speaker (Marshall OEM V30)
# '''4x12 5153''' — EVH 5150-III cabinet with four 12" speakers (probably G12H or G12-EVH)
# '''4x12 Basketweave''' — Marshall basketweave cabinet with four 12" speakers
# '''4x12 Brit 800''' — Marshall JCM800 cabinet with four 12" speakers
# '''4x12 Brit AX''' — Marshall 1960AX angled cabinet with four 12" speakers
# '''4x12 Brit Greenback''' — '72 Marshall cabinet with four 12" Celestion G12M greenbacks
# '''4x12 Brit TV''' — tall vertical angled Marshall 1960 cabinet with four 12" speakers (probably Celestion G12M greenbacks) (this curve is associated with the 4x12 1960TV DynaCab)
# '''4x12 Citrus''' — Orange cabinet with four 12" Celestion V30s
# '''4x12 Euro''': Bogner Standard cabinet with four 12" Celestion V30s
# '''4x12 Friedman''' — Friedman cabinet with two 12" Celestion V30s and two 12" Celestion G12M greenbacks. "The Friedman cab has two Greenbacks and two V30s. The impedance curve is for the cabinet as a whole. The DynaCabs are for the individual speakers. Therefore the same impedance curve applies to both DynaCabs." [https://forum.fractalaudio.com/threads/dynacab-pack-limited-public-beta.198581/post-2470963]
# '''4x12 Hipower''' — Possibly a Harry Joyce-era HiWatt cab with four 12" Fane speakers [https://forum.fractalaudio.com/threads/free-hj-4x12-rca-cab-pack.156177]
# '''4x12 Hipower Lindsey B''' — Lindsey Buckingham's HiWatt cab with four 12" speakers
# '''4x12 Hipower Pete T''' — Pete Townsend's HiWatt cab with four 12" Fane speakers [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-20-02-public-beta-beta-1.185043/post-2281949]
# '''4x12 Lerxst Omega''' — Lerxst Omega cabinet with four 12" speakers (probably greenbacks)
# '''4x12 London Town Tall''' — London City cabinet with four 12" speakers
# '''4x12 PVH 6160''' — Peavey 5150 cabinet with four 12" Sheffield speakers
# '''4x12 Recto Large''' — Mesa Oversized Rectifier cabinet with four 12" speakers
# '''4x12 Recto Slant''' — Mesa "slanted" Rectifier cabinet with four 12" speakers
# '''4x12 Recto Small''' — Mesa small Rectifier cabinet with four 12" speakers
# '''4x12 Recto Straight''' — Mesa "straight" Rectifier cabinet with four 12" speakers
# '''4x12 Rumble''' — Dumble cabinet with two 12" EV-12L speakers and two 12" EV-12S speakers in a X-pattern
# '''4x12 Solo 100''' — Soldano cabinet with four 12" speakers
# '''4x12 USA Lead C90''' — '80s Mesa cabinet with four 12" C90 speakers
# '''4x12 USA Semi-Open''' — MESA open/closed cabinet with four 12" speakers
# '''Double Notes Loadbox''' — based on a Two-Notes Torpedo
# '''Load Box LB-2 UK''' — derived from Fractal Audio's Load Box LB-2, set to "UK" voicing (= 4x12 with greenbacks, 100 Hz resonant frequency)
# '''Load Box LB-2 US''' — derived from Fractal Audio's Load Box LB-2, set to "US" voicing (= 1x12 with a Jensen speaker, 70Hz resonant frequency)
# '''Oxbow Loadbox''' — based on a Universal Audio Ox
# '''Resistive Load''' — flat curve which disables the speaker impedance / resonance modeling. Use this when connecting the Fractal Audio modeler to a tube amp

==CABINET RESONANCE==

This was introduced in firmware Ares 11, and this is not available on Axe-Fx II and AX8.

From the Owners Manual:
<blockquote>
"This parameter interacts with Speaker Impedance Curve, located on the Advanced page. Changing Cabinet Resonance alters the amount of cabinet resonance in the impedance curve."
</blockquote>

This parameter defaults to 100%.

==SPEAKER DRIVE==

From the Owners Manual:
<blockquote>
"This simulates distortion and gentle compression caused by pushing a speaker too far. It interacts with the Master which determines how hard the actual power amp is pushing. Don’t overlook this when striving for “vintage” tones as it helps make edge-of-breakup tones sound like an old, well-played amp."
</blockquote>

Note that if you crank it, it will start to sound like a fuzz or a blown speaker.

<blockquote>
"The range of the speaker drive parameter is far greater than you would be able to push any real speaker before it self-destructed. If it doesn't sound good set that high, simply turn it down." [http://forum.fractalaudio.com/threads/weird-speaker-drive-in-5-07.48341/#post-632608]
</blockquote>

<blockquote>
"There are architectural reasons for Speaker Drive being in the Amp block." [http://forum.fractalaudio.com/threads/speaker-drive-vs-motor-drive.125541/#post-1494086]
</blockquote>

<blockquote>
"Speaker Drive models the magnetic compression (which is actually distortion) that occurs due to the nonlinear speaker excursion vs. applied voltage." [http://forum.fractalaudio.com/threads/speaker-drive-vs-motor-drive.125541/page-2#post-1494537]
</blockquote>

Default value is 1 (as of firmware 23). Keep it at zero when using a traditional guitar speaker cabinet.

<blockquote>"Changed default values of Speaker Drive and Speaker Thump to better align with measurements of typical speakers."</blockquote>

<blockquote>
(about using Speaker Drive with a traditional cab) "I would say no. Your guitar cab is already distorting so you would be adding more distortion on top. As always, though, let your ears decide." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-6-02-public-beta.122103/page-7#post-1454119]
</blockquote>

In response to: "Can you compare and contrast Compression, Compliance, and Drive? Do they capture independent factors or if one of these parameters is turned up high the others should be turned down or off?":

* '''Speaker Compression''' models the reduction in volume as the voice coil heats up.
* '''Speaker Drive''' models the distortion of the cone/motor.
* '''Speaker Compliance''' models parameter shift as the voice coil moves within the magnet. The Bl product is a function of voice coil displacement. Bl is the "force factor" and is the product of magnetic field (B) times length of the coil in the magnet gap (l). [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-14.163656/post-1962917]
* '''Speaker Thump''' models the dynamic nonlinear behavior of a guitar speaker (mostly subsonic).
* '''Speaker Breakup''' sets the type speaker of breakup.

[https://forum.fractalaudio.com/threads/table-amp-settings-depending-on-power-amp-and-speaker.185259 Click here for recommended settings for different kinds of amplification]

The Speaker Drive algorithm has been improved in firmware 20.00 for the Axe-Fx III:

<blockquote>
(Release Notes) "New Speaker Drive algorithm in Amp block. This new algorithm more accurately models the frequency dependent distortion of guitar loudspeakers. The default value (upon resetting the block) is 2.0 which gives roughly 1 dB of compression. Setting the value to 0.0 defeats the speaker drive modeling. Higher values give a smoother and more focused sound, rounding off the “sharp edges” and yielding greater compression."
</blockquote>

<blockquote>
"Speaker Drive is free of aliasing." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-20-00-public-beta-beta-4.184197/post-2267206]
</blockquote>

<blockquote>"If you are using a real guitar speaker you may want to turn these controls down/off. With an FRFR I would not recommend that as FRFR speakers are not designed to distort like guitar speakers do." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-20-01-public-beta-beta-2.184738/post-2276849]</blockquote>

About Speaker Drive and Speaker Thump:
<blockquote>"Excessive values of either parameter can "destroy" the virtual voice coil. Don't turn things up that high." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-20-01-public-beta-beta-2.184738/post-2276769]</blockquote>

<blockquote>"If you want "nonlinear IRs" you need to use something like Volterra kernels. I've experimented with this and, in fact, the Speaker Drive and Speaker Thump parameters essentially create higher order Volterra kernels based on various amp parameters." [https://forum.fractalaudio.com/threads/anyone-try-using-ua-ox-stomp-for-their-cabs.198601/post-2470708]</blockquote>

==SPEAKER THUMP==

Added in firmware 20.01 for the Axe-Fx III. Uses this with FRFR amplification at low volumes.

Release notes:

<blockquote>"Added Speaker Thump control to Amp block. Speaker Thump models the dynamic, nonlinear behavior of a guitar speaker. A value of 5.0 roughly corresponds to an amplifier running into a speaker rated at the same power as the amplifier, i.e., a 100W amplifier running into a 100W speaker. The reset value is a conservative 2.5 which represents, i.e., a 50W amp running into a 100W speaker. Note that the majority of the response is in the subsonic region and the effect is primarily tactile. Existing presets are not affected and the value will be zero."</blockquote>

<blockquote>"If you are using a real guitar speaker you may want to turn these controls down/off. With an FRFR I would not recommend that as FRFR speakers are not designed to distort like guitar speakers do." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-20-01-public-beta-beta-2.184738/post-2276849]</blockquote>

[https://forum.fractalaudio.com/threads/table-amp-settings-depending-on-power-amp-and-speaker.185259 Click here for recommended settings for different kinds of amplification]

<blockquote>"Speaker Thump was a revelation after analyzing the Volterra kernels of guitar speakers driven near their power limits. I can't really say much more than that without giving away proprietary information. For me it's a must when using FRFR. It evokes that feeling of standing in front of a cranked 4x12." [https://forum.fractalaudio.com/threads/speaker-drive-and-thump-appreciation-thread.185272/post-2287427]</blockquote>

<blockquote>"If it sounds good it is good. A real guitar cab will creates its own thump AT HIGH VOLUMES. If you are playing at low volumes you can use Speaker Thump to simulate the high volume behavior." [https://forum.fractalaudio.com/threads/speaker-drive-and-thump-appreciation-thread.185272/post-2287433]</blockquote>

In response to: "Can you compare and contrast Compression, Compliance, and Drive? Do they capture independent factors or if one of these parameters is turned up high the others should be turned down or off?"

* '''Speaker Compression''' models the reduction in volume as the voice coil heats up.
* '''Speaker Drive''' models the distortion of the cone/motor.
* '''Speaker Compliance''' models parameter shift as the voice coil moves within the magnet. The Bl product is a function of voice coil displacement. Bl is the "force factor" and is the product of magnetic field (B) times length of the coil in the magnet gap (l). [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-14.163656/post-1962917]
* '''Speaker Thump''' models the dynamic nonlinear behavior of a guitar speaker (mostly subsonic).
* '''Speaker Breakup''' sets the type speaker of breakup.

Default value is 1.25 (as of firmware 23).

<blockquote>"Changed default values of Speaker Drive and Speaker Thump to better align with measurements of typical speakers."</blockquote>

About turning up Speaker Drive or Speaker Thump too high:

<blockquote>"Excessive values of either parameter can "destroy" the virtual voice coil. Don't turn things up that high." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-20-01-public-beta-beta-2.184738/post-2276769]</blockquote>

<blockquote>"Thump is a nonlinear process and you've essentially pushed the speaker to the point that the voice coil is traveling well outside the magnet gap. Turn Thump down. With a real speaker and amp you would have destroyed the speaker." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-20-02-release.185294/post-2288339]</blockquote>

==SPEAKER BREAKUP==

Added in firmware 20 for the Axe-Fx III.

Sets the type of speaker breakup.

Values: Soft, Medium (default), Hard.

In response to: "Can you compare and contrast Compression, Compliance, and Drive? Do they capture independent factors or if one of these parameters is turned up high the others should be turned down or off?"

* '''Speaker Compression''' models the reduction in volume as the voice coil heats up.
* '''Speaker Drive''' models the distortion of the cone/motor.
* '''Speaker Compliance''' models parameter shift as the voice coil moves within the magnet. The Bl product is a function of voice coil displacement. Bl is the "force factor" and is the product of magnetic field (B) times length of the coil in the magnet gap (l). [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-14.163656/post-1962917]
* '''Speaker Thump''' models the dynamic nonlinear behavior of a guitar speaker (mostly subsonic).
* '''Speaker Breakup''' sets the type speaker of breakup.

==SPEAKER COMPRESSION==

This was introduced in the Ares firmware, and is not available on Axe-Fx II and AX8.

From the Owners Manual:
<blockquote>
"Aka the “chunka chunka” parameter. It models the interaction of the power amp with the power compression of a virtual speaker. Typical guitar speakers compress between 3 and 6 dB depending upon construction, age, volume, etc. The default value is conservative and yields about 3 dB of compression. Master, Presence, and Depth will interact considerably with Speaker Compression, with higher causing more compression. A gain reduction meter shows the amount of Speaker Compression when this parameter row is selected. Note that this parameter does not reset to its default value when changing the Amp Type."
</blockquote>

From the release notes:

<blockquote>
"New Speaker Dynamics modeling. The Speaker Dynamics control adjusts the amount of virtual voice coil heating. Higher values result in more heating and commensurately higher voice coil resistance. The Speaker Time Constant will be reset to 2 seconds for existing presets. A typical guitar speaker has a voice coil thermal time constant in the range of several seconds." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486]
</blockquote>

<blockquote>
(Quantum 9) "Removed the “Motor Drive” and “Transformer Grind” algorithms and associated parameters from the Amp block. These have been replaced by the new “Speaker Compression” algorithm. This algorithm models the interaction of the power amp with the power compression of the virtual speaker. The “Spkr Comp” parameter controls the amount of virtual speaker compression. This value defaults to 3.0 when the Amp block is reset. It does not get reset when changing the model. If using the Axe-Fx II with a tube power amp and conventional guitar cab you may want to reduce this value to 0.0. The gain reduction meter shows the amount of virtual power compression (select the Spkr Comp knob to monitor the gain reduction). Typical guitar speakers compress between 3 and 6 dB depending upon construction, age, volume, etc. The default value is conservative and yields about 3 dB of compression. Note that the Master Volume control will interact considerably with the Speaker Compression algorithm as will the Presence and Depth controls. Higher values of Master Volume will cause more virtual speaker compression. [https://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-9-00-beta.130981/]"
</blockquote>

<blockquote>
(Ares 12.14) "Improved Amp block Speaker Compression modeling. New algorithm is more accurate and sounds smoother with more “growl”. [https://wiki.fractalaudio.com/wiki/index.php?title=Amp_modeling_progress#Firmware_Ares_12.x]"
</blockquote>

The Speaker Compression parameter replaced former parameters Motor Drive and Transformer Grind in the Amp block.

Default value is 1. Set it to zero when using a tube power amp and traditional guitar cab.

Fractal Audio explains:
<blockquote>
"Yes, the low end "weight" is what I immediately noticed. I don't use a lot, 1-2 typically. Just enough to thicken things up a bit. It's far more natural than the old algorithm which was an exotic compressor." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486/post-2067313]
</blockquote>

<blockquote>
"I call this one the "clanka-chunka burning love" firmware." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-9-00-beta.130981/#post-1551410]
</blockquote>

<blockquote>
"Notice how the low end goes "chunka chunka" and the top end "clanks". Pick squeaks are also more prominent." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-9-00-beta.130981/page-2#post-1551443]
</blockquote>

<blockquote>
"What I love about Speaker Comp is how it brings out the "chirp" on the unwound strings. Listen to all those great classic Marshall guitar tones and there's that chirp." [http://forum.fractalaudio.com/threads/beta-9-test-with-the-usa-iic-brt-dp-stereo-bbd-and-oh-zilla-irs.131008/#post-1551968]
</blockquote>

<blockquote>
"To really get the effect of speaker compression try the Speaker Compression knob. This behaves similarly to the output compressor but also "feeds back" to the power amp. As the speaker compresses the power amp behavior changes." [http://forum.fractalaudio.com/threads/tips-on-getting-rid-of-that-hifi-sound-1st-look-at-3.140533/#post-1665472]
</blockquote>

<blockquote>
"The default used to be 2.0. I reduced it to 1.0 because I felt it was better to be conservative with the default value and let people increase it if desired. I'm considering increasing the default back to 2.0 (or higher)." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-14.163656/post-1962918]
</blockquote>

<blockquote>
"I find I'm dialing in between 2 and 4. Sometimes even higher." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-14.163656/post-1962380]
</blockquote>

<blockquote>
"If using a tube power amp into a traditional cab all should be zero. If using a solid-state amp into a traditional cab I would recommend Speaker Compression and Compliance not be zero." [http://forum.fractalaudio.com/threads/axe-fx-iii-firmware-2-00-public-beta-2.144615/page-2#post-1710669]
</blockquote>

In response to: "Can you compare and contrast Compression, Compliance, and Drive? Do they capture independent factors or if one of these parameters is turned up high the others should be turned down or off?"

* '''Speaker Compression''' models the reduction in volume as the voice coil heats up.
* '''Speaker Drive''' models the distortion of the cone/motor.
* '''Speaker Compliance''' models parameter shift as the voice coil moves within the magnet. The Bl product is a function of voice coil displacement. Bl is the "force factor" and is the product of magnetic field (B) times length of the coil in the magnet gap (l). [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-14.163656/post-1962917]
* '''Speaker Thump''' models the dynamic nonlinear behavior of a guitar speaker (mostly subsonic).
* '''Speaker Breakup''' sets the type speaker of breakup.

[https://forum.fractalaudio.com/threads/table-amp-settings-depending-on-power-amp-and-speaker.185259 Click here for recommended settings for different kinds of amplification]

==SPEAKER COMPLIANCE==

This was introduced in the Ares firmware, and is not available on Axe-Fx II and AX8.

From the Owners Manual:
<blockquote>
"This control changes the nonlinear behavior of the virtual speaker. Selecting a new amp model or resetting the block will set the value to 50% which is a typical value for guitar speakers."
</blockquote>

Default valve is 50%. Set it to zero when using a tube power amp and traditional guitar cab. No need to turn it down when using a solid-state power amp.

From the release notes:
<blockquote>
"Improved Amp block speaker dynamic parameter modeling. The new Speaker Compliance parameter controls the nonlinear behavior of the virtual speaker. Existing presets will load with this parameter at 0.0 and will be unchanged tonally from the previous firmware (IOW your presets will not be altered). Selecting a new amp model or resetting the block will set the value to 5.0 which is a typical value for guitar speakers."
</blockquote>

Fractal Audio explains:
<blockquote>
"If using a tube power amp into a traditional cab all should be zero. If using a solid-state amp into a traditional cab I would recommend Speaker Compression and Compliance not be zero." [http://forum.fractalaudio.com/threads/axe-fx-iii-firmware-2-00-public-beta-2.144615/page-2#post-1710669]
</blockquote>

<blockquote>
"The easy way to understand compliance is to think of a spring. In Physics 101 we're taught that F = kx but that's an ideal spring. A real spring is nonlinear. Eventually you get to a point where compressing or stretching the string you run out of travel and the force goes nonlinear. A speaker is the same way. The suspension is essentially a spring and the greater the displacement the greater the force trying to restore the cone to its rest position. The compliance parameter controls how stiff that suspension is." [http://forum.fractalaudio.com/threads/axe-fx-iii-firmware-2-00-public-beta-2.144615/page-6#post-1711452]
</blockquote>

<blockquote>
"In a loudspeaker the resonances do change a bit vs. applied voltage but the effect is subtle. The Axe-Fx III models this (it's the Speaker Compliance parameter). For all intents and purposes though it's pretty much a static network as the parameter shift only occurs at large excursion values which only occur at very low frequencies (excursion is the integral of applied voltage)." [https://forum.fractalaudio.com/threads/speaker-resonance-pa-equalization-tied-to-master-volume-level.155270/post-1848002]
</blockquote>

<blockquote>
"An IR isn't the same as a real speaker. Speaker Compliance models the dynamic change in speaker impedance. When a speaker moves its impedance changes. The low-frequency resonance shifts and the inductance decreases thereby reducing the high frequencies. We model all this. You can adjust the intensity of the speaker impedance change via this control.
If you take a DI off the output of an amp and put it through and IR it will be brighter than the actual speaker because the IR is static but the speaker is dynamic." [https://thegearforum.com/threads/adventures-in-fractals-dual-rectifiers.3949/post-151425]
</blockquote>

In response to: "Can you compare and contrast Compression, Compliance, and Drive? Do they capture independent factors or if one of these parameters is turned up high the others should be turned down or off?"

* '''Speaker Compression''' models the reduction in volume as the voice coil heats up.
* '''Speaker Drive''' models the distortion of the cone/motor.
* '''Speaker Compliance''' models parameter shift as the voice coil moves within the magnet. The Bl product is a function of voice coil displacement. Bl is the "force factor" and is the product of magnetic field (B) times length of the coil in the magnet gap (l). [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-14.163656/post-1962917]
* '''Speaker Thump''' models the dynamic nonlinear behavior of a guitar speaker (mostly subsonic).
* '''Speaker Breakup''' sets the type speaker of breakup.

[https://forum.fractalaudio.com/threads/table-amp-settings-depending-on-power-amp-and-speaker.185259 Click here for recommended settings for different kinds of amplification]

==SPEAKER TIME CONSTANT==

From the Owners Manual:
<blockquote>
"This adjusts the thermal time constant of the virtual voice coil, affecting the attack and release of virtual Speaker Compression. Lower values cause the voice coil to heat and cool faster and viceversa."
</blockquote>

If Speaker Comp is zero, Speaker Time Constant is not operational.

From the release notes:
<blockquote>
(Cygnus amp modeling) "The Speaker Time Constant will be reset to 2 seconds for existing presets. A typical guitar speaker has a voice coil thermal time constant in the range of several seconds." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486/post-2067182]
</blockquote>

Fractal Audio explains:
<blockquote>
"It adjusts the thermal time constant of the virtual voice coil. Lower values cause the voice coil to heat and cool faster and vice-versa." [http://forum.fractalaudio.com/threads/speaker-time-constant.131886/#post-1561227]
</blockquote>

<blockquote>
"If Speaker Comp is zero the time constant does nothing. Any perceived difference is perceptual bias." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-9-00-firmware-release.131649/page-18#post-1560328]
</blockquote>

<blockquote>
"Time constant is dependent on the physical construction of the speaker." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-9-01-beta.131857/page-7#post-1561333]
</blockquote>

Also read the notes about the (removed) [[#MOTOR_DRIVE|Motor Drive]] parameter.

==OUTPUT MODE==

This was added in the Ares 1.16 firmware and is not available on Axe-Fx II and AX8.

From the Owners Manual:
<blockquote>
"The default value, “FRFR”, is designed for use while using “Full Range/Flat Response” monitors, or while recording. The “Solid State Power Amp + Cab” (“SS PWR AMP + CAB”) mode is intended for use while using a solid-state power amp and conventional guitar cab. In this mode speaker compression modeling behaves differently, relying on the speaker for compression while still simulating the interaction with the power amp."</blockquote>

<blockquote>"The SS PA + Cab Mode is NOT intended for use with “current drive” power amps, i.e. tube power amps, Class-D current feedback amps, etc. This mode CAN be used, however, with FRFR monitors in high volume applications where the monitor’s speakers are compressing, thereby achieving a more dynamic response."
</blockquote>

<blockquote>"Most modern Class-D amps are voltage feedback as AFAIK." [https://forum.fractalaudio.com/threads/table-amp-settings-depending-on-power-amp-and-speaker.185259/post-2488087]</blockquote>

Non-Class-D solid-state amps include: Matrix GT.

Class-D power amps include: Seymour Duncan PowerStage, Dayton.

Ideally, the user would be allowed to set this parameter per output. This isn't possible because it's part of the Amp block processing.

Fractal Audio explains:
<blockquote>
"Not possible as the processing is done in the Amp block not the Output block." [https://forum.fractalaudio.com/threads/frfr-ss-poweramp-option-per-output-mode.163839/post-1964181]
</blockquote>

[https://forum.fractalaudio.com/threads/table-amp-settings-depending-on-power-amp-and-speaker.185259 Click here for recommended settings for different kinds of amplification]

==AUTO DYNACAB IMPEDANCE==

Firmware 22 for the Axe-Fx III:

<blockquote>
"The Amp block now features “Auto Dyna-Cab Impedance”. When set to ON the speaker impedance curve of the Amp block will follow the Cabinet Type in the first mixer slot of the associated Cabinet block. I.e., if the Cab Type in the first mixer slot of Cabinet 1 is, say, 4x12 5153 and the Mode is Dyna-Cab then Amp 1’s speaker impedance will automatically be set to 4x12 5153."
</blockquote>

[[Cab block#DynaCabs|Read more about DynaCab cabinet modeling]]

=Input EQ=

Pre-EQ or Input EQ refers to the use of EQ to shape the guitar's tone before the distortion stage.

This was added to the Amp block with the arrival of firmware Ares. These parameters adjust a powerful set of filters at the input of the Amp block, so its effect is heard before preamp distortion or a front-end tone stack.

[http://forum.fractalaudio.com/threads/the-power-of-pre-eq.80951 Cliff's Tech Note]:

<blockquote>
* "As outlined in the MIMIC white-paper the fundamental paradigm of distorted guitar tone is EQ -> Distortion -> EQ. For higher gain tones the post-EQ is typically the tone stack and the Presence and Depth controls, when available. Therefore the user has access to the post-EQ but no control over the pre-EQ. One notable exception to this rule is the Mesa Mark series of amplifiers where the tone stack is located before the distortion.
* I suppose the ultimate amplifier would be one with dedicated pre-EQ and post-EQ controls although I can imagine many guitar players with looks of bewilderment when presented with such an amp. Indeed I believe there was an amp years ago that had separate input and output graphic EQs. I'm thinking it was made by Seymour Duncan but it was a long time ago so I'm not really sure. I don't believe it was terribly successful.
* So as we delve into the realms of higher gain tones we are the mercy of the amp designer and his choice of pre-EQ. The standard practice is to cut the lows before the distortion stages. There are various approaches to this: small coupling caps, partially bypassed cathodes, etc. These are simple methods and given the relatively simple nature of tube amps all we can really expect. Other popular pre-EQ techniques are shelving filters, i.e. the Marshall 470K, 470pF network and networks which roll off highs.
* The pre-EQ, along with the post-EQ, shapes the tone when the amount of distortion is low. As the distortion increases the tone becomes more dependent upon the post-EQ. Anyone who has adjusted a Mesa Mark series amp will attest to the seeming ineffectiveness of the tone controls at higher gains. They will also attest to the affect the tone controls have on the feel.
* So... the pre-EQ is an important part of the overall tone equation. We guitarists tend to focus upon the post-EQ and put graphic or parametric EQs after the amp but we neglect the pre-EQ. Therefore it is worthwhile to experiment with pre-EQ. The simplest approach to start with is using a graphic EQ before the amp block. Note how boosting or cutting certain bands affects the tone and feel. Note how the effect changes as the gain is increased or decreased.
* One popular studio technique in the 80's was to put a parametric EQ before an amp and boost a narrow band of frequencies. This gives a slight mid-emphasis to the sound and can be useful in helping the guitars stand out in a mix. This technique seems to have been lost over the years. Years ago Micheal Sweet from Stryper showed me the frequencies he used and IIRC he boosted around 800 Hz about 6 dB. I don't remember the Q but I would start around 1.4. Incidentally the frequencies he were boosting are just about the same as the frequencies that are cut by the tone stack. So when playing softly the net result is a flatter EQ. As you play harder the input EQ becomes less effective and the tone becomes more scooped.
* Pre-EQ can make amps sound warmer, or tighten the bass. It can be used to increase brightness without becoming harsh. Pre-EQ is also very useful with amps on the verge of breakup or mildly overdriven. Experiment with boosting frequencies to give your leads a more vocal character or make them more unique."</blockquote>

The Filter trick below can be applied using the Input EQ:

<blockquote>"This was a common technique in the 80's when tracking. If you have an Axe-Fx or other modeler with EQ options you can try it yourself. Put an EQ or Filter block before the amp. A parametric is best. Set the type to Peaking, Frequency to 1 kHz and Q to around 1 and gain to around 6 dB to start. Experiment with the parameters." </blockquote>

[https://www.youtube.com/watch?v=u_O0Dz_OUBY| Cooper Carter's EQ tips]

==TYPE + FREQUENCY + Q + GAIN==

These parameters work together to define a powerful multi-mode filter that can be used for anything from a subtle bump to an extreme spike, or from gentle to extreme shelving.

==LOW CUT==

Same as Low Cut Freq on the Preamp page.

==HIGH CUT==

This shaves highs off the input signal.

This is not the same as [[#HIGH_CUT_FREQUENCY|High Cut Frequency]] on the Preamp page.

==DEFINITION==

From the Owners Manual:
<blockquote>
"This control is a basic “tilt EQ” which adds highs/cuts lows, or vice versa. It is located at the amp type’s input, so its effect is heard before preamp distortion or a front-end tone stack."
</blockquote>

The tilt point is at 1kHz.

Positive values increase the amount of upper overtone saturation whilst negative values reinforce lower harmonics.

The [[Filter block]] also provides a [https://wiki.fractalaudio.com/wiki/index.php?title=Filter_block#Tilt_EQ Tilt EQ] type.

=Output EQ=

==TYPE + LOCATION + OFF/ON==

The Amp block has its own graphic EQ.

The EQ type and location (POST or PRE) can be selected through the EQ TYPE and EQ LOCATION parameters.

From the Owners Manual:
<blockquote>
"These parameters determine the number of bands, location, and on/off status of a graphic equalizer built in to the amp block. EQ Type sets number of bands and Q behavior (you can also change this from the Output EQ page using the NAV UP/DOWN buttons.) EQ Location sets the position of the equalizer. The default value of “OUTPUT” places the EQ at the output of the virtual power amp. “PRE PA” places the EQ between the preamp and power amp. The “INPUT” setting moves the Post EQ in front of the preamp. The EQ On/Off switch can be used to disable the EQ, and this setting can be controlled by a modifier."
</blockquote>

From the release notes:
<blockquote>
(firmware 19 for Axe-Fx II) "Added EQ Location parameter to Amp block. The sets the position of the graphic EQ. The default value of “Post P.A.” places the EQ at the output of the power amp. “Pre P.A.” places the EQ between the preamp and power amp. The graphic EQ in the Amp block is fixed in position at the output of the power amp section."
</blockquote>

Fractal Audio explains:
<blockquote>
(about the GEQ in the JPIIC model) "It's not that the Graphic EQ isn't the same, the TAPERS are not the same. On the real amp the controls do virtually nothing until you get near the ends of the range. If you move a slider to, say, 3/4 of its range it does almost nothing. If you were to set the model's slider to the same position you would get significantly more boost. I didn't model the nonlinear slider behavior because IMO it's a design flaw. Graphic EQs should have a nice, linear-in-dB response. Otherwise the graphic EQ is very accurate. The frequency and Q behavior is spot-on." [https://forum.fractalaudio.com/threads/real-jp2c-vs-axe-fx-3-sim-comparison.168942/post-2029916]
</blockquote>

<blockquote>
"The graphic EQ sliders aren't accurate in terms of position but they ARE accurate in dB and response. If you've ever used Mark series graphic EQ you'd notice that the sliders do very little in the middle and then rapidly change as you get near the top/bottom. This sucks so the Axe-Fx uses proper linear-in-dB controls." [https://forum.fractalaudio.com/threads/buttons-functioning-as-on-amps.170531/post-2052762]
</blockquote>

<blockquote>
"The tapers in the Axe-Fx are linear-in-dB. In the real amp (Mesa Mark series) they are quite nonlinear. For example, if we assume the sliders in the real amp go from -12 to +12, and we set a slider to +6 the corresponding position on the Axe-Fx might be only +3 dB. [https://forum.fractalaudio.com/threads/accurate-low-end-in-mesa-boogie-mark-iic-mark-v-jp-2c.177844/post-2166068]"
</blockquote>

The possible locations are:
* '''OUTPUT''' (default): The EQ is at the output of the virtual power amp.
* '''PRE PA''': The EQ is between the preamp and power amp.
* '''INPUT''': This moves the Post EQ to the location of the Pre EQ, in front of the preamp.

Tip: press Enter to reset all sliders to 0 dB (AX8 and Axe-Fx II only). Change the EQ type by pressing up/down.

The EQ can be turned off and on, also remotely.

The types of EQ available are:
* '''8 Band Variable Q'''
* '''7 Band Variable Q'''
* '''5 Band (Mark)''': this emulates the response of the on-board EQ in the Mesa Boogie Mark series amplifiers. When selecting amp models based on Mesa amps the type automatically changes to 5-band.
* '''8 Band Constant Q'''
* '''7 Band Constant Q'''
* '''5 Band Constant Q'''
* '''5 Band Passive'''
* '''4 Band Passive'''
* '''3 Band Passive'''
* '''3 Band Console'''

The 5-band EQ is especially useful with models based on Mesa Boogie's Mark series.

See [[EQ]] for more information about the EQ types.

=Dynamics=

==INPUT DYNAMICS==

This is not supported on the FM3 and FM9.

From the Owners Manual:
<blockquote>
"Sets the strength of an input dynamics processor. When set below zero, the amp type compresses, resulting in a smoother, less dynamic sound. When set greater than zero, the amp expands, resulting in a punchier, crunchier and more dynamic sound. Note that extreme values can have undesirable side-effects such as pumping or clipping."
</blockquote>

Fractal Audio explains:
<blockquote>
"Dynamics works at the input to the block. Negative values compress the input, positive values expand." [http://forum.fractalaudio.com/threads/output-comp-love.96779/#post-1160978]
</blockquote>

<blockquote>
"The Dynamics knob in the Amp block does the same thing as the Dynamics mode of the compressors." [http://forum.fractalaudio.com/threads/comp-vs-multicomp.107343/#post-1284495]
</blockquote>

<blockquote>
"The Dynamics type in the Compressor block is the same thing with more control." [http://forum.fractalaudio.com/threads/anyone-use-input-dynamics.146093/#post-1727558]
</blockquote>

Here is more information about missing support for Input Dynamics on the FM3:

<blockquote>
"Certain features were removed to allow the algorithms to run including the bias tremolo, input dynamics processing, and several other inauthentic enhancements." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-62#post-28446966]
</blockquote>

<blockquote>
"We removed all the superfluous stuff (bias tremolo, dynamic presence/depth, etc.) in order to get the core amp modeling to run on the slower processor." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-68#post-28450968]
</blockquote>

<blockquote>
"The Axe-Fx III contains various algorithms that allow you to enhance the amp modeling that don't exist on a real amp. I.e. dynamic presence/depth, input dynamic processing, etc. These were removed to allow the core amp modeling to run on the lower-powered processor." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-70#post-28454394]
</blockquote>

==MASTER BIAS EXCURSION==

This was introduced in the "Cygnus" amp modeling firmware. It scales ALL the bias excursion parameters. The default value for the various bias excursions is usually 100% but there are some amps where a bias excursion may be 0%, depending on the topology.

Fractal Audio explains:
<blockquote>
"16.00 and after use a new bias excursion algorithm which is much more accurate but also generates greater amounts of bias excursion. You'll never get 15.01 to get that choked 5E3 Tweed sound whereas 16.00 and later replicate it very accurately. Bias excursion reduces clarity and string separation but it's necessary for a realistic sound. I've said it before but I guess I need to say it again, if you want that 15.01 sound simply turn down Master Bias Excursion. That's why the control was added. [https://forum.fractalaudio.com/threads/moving-backward.180041/post-2206432]"
</blockquote>

<blockquote>"The simplest way to remove fizz is turn down Master Bias Excursion." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317936]</blockquote>

==OUTPUT COMPRESSION + TYPE + THRESHOLD + CLARITY==

From the Owners Manual:
<blockquote>
"This controls the ratio of a compressor specifically tailored to reduce the output dynamic range of the amp block. A gain reduction meter shows the amount of compression when this parameter row is selected."
</blockquote>

From the release notes:
<blockquote>
(firmware Quantum 7.02) "Improved Amp block output compressor. New algorithm is more musical and reacts faster to transients. If you are using this in your presets it is recommended to audition your presets and readjust as necessary. The Gain Reduction meter now shows the total gain including the makeup gain." "Non-zero values increase CPU usage. "The effect of the compressor setting can be watched on the DYN page of the Amp block."
</blockquote>

It offers three types of compression or gain enhancement, at the output section of the Amp block.

;'''OUTPUT''' : This simply compresses the output, similar to a Compressor block that follows the Amp block. It controls the ratio of a compressor specifically tailored to reduce the output dynamic range of the amp block. A gain reduction meter shows the amount of compression. Setting this to a non-zero value will increase CPU usage. The Out Comp parameter controls the amount of compression (compression ratio). The user can adjust the compression threshold if desired. The bar graph at the bottom of the menu displays the amount of gain reduction. A modifier can be attached to Output Comp. Output Comp Clarity affects Output Comp. It adjusts the bass response of the input dynamics and can be used to add clarity to the bass.

Fractal Audio explains:
<blockquote>
"The Output Compressor is a simplified version of the Compressor block." [http://forum.fractalaudio.com/threads/tips-on-getting-rid-of-that-hifi-sound-1st-look-at-3.140533/#post-1665472]
</blockquote>

<blockquote>
(sonic difference between Output Comp in Amp block and Comp block after Amp) "No different other than lack of advanced controls. Attack, release, etc. are fixed." [http://forum.fractalaudio.com/threads/what-is-the-sonic-difference-between-output-comp-in-amp-block-and-comp-block-after-amp.125469/#post-1492987]
</blockquote>

<blockquote>
"The compressor tries to apply make-up gain but it can only guess at the amount." [http://forum.fractalaudio.com/threads/output-comp-strangeness.87485/#post-1058658]
</blockquote>

<blockquote>
"Output Comp is compression ratio. Ratio = 1 + 3 * comp/10. Attack and release are fixed. Threshold is adjustable in the advanced menu." [http://forum.fractalaudio.com/threads/ouput-comp-recommendations.87494/#post-1058766]
</blockquote>

;'''FEEDBACK''' : This compresses the block output (see above), AND also applies dynamics to the input of the Amp block. You will get more distortion as you play harder and less when you play softer or roll back the volume.

Fractal Audio explains:
<blockquote>
"If you set the Compressor Type to Feedback and turn up the Output Compression you will get more distortion as you play harder. So you can create an amp that cleans up more when you play lightly or roll of the volume." [http://forum.fractalaudio.com/threads/feedback-parameter-in-amp-block-output-compressor.101388/#post-1216109]
</blockquote>

<blockquote>
"Here's a little trick to enhance the "clean up with guitar volume knob" thing. In the Amp block go to the Dynamics page. Set the Compressor Type to Feedback. Turn up the Output Compression to taste. Notice that when you play harder the amp will distort more. Now you can use the Input Drive and/or Trim to reduce the input gain so that when you play softer or roll off the volume the amp will clean up. Real amps get this from power supply sag but this requires the power amp be driven hard which can get muddy. This trick allows you to get that same response without cranking the Master Volume." [http://forum.fractalaudio.com/threads/clean-to-mean-w-the-volume-knob.144394]
</blockquote>

<blockquote>
"The Axe-Fx III models are extremely accurate. The Kemper has it's own vibe which a lot of people like. It's characterized by lots of midrange compression. You can replicate this on the Axe-Fx by setting the Output Compression type in the Amp block to Feedback and dialing in ~6 dB of compression. Adjust to taste." [https://forum.fractalaudio.com/threads/axe-fx-iii-clean-amp-sounds-compared-to-kemper-cleans.151497/post-1804532]
</blockquote>

;'''GAIN ENHANCER''' : This simulates the acoustic reinforcement of a loud amp coupling into the guitar and enhancing the output signal. Introduced in firmware Ares 9.01, this is a very popular feature, especially when playing through studio monitors or headphones at not-so-loud volume levels.

Fractal Audio explains:
<blockquote>
"At gig volumes you probably don't need any Gain Enhancer. It's designed to simulate the acoustic reinforcement of playing loud. But there are no rules so try it." [https://forum.fractalaudio.com/threads/fw10-gain-enhancer-reflections.155195/post-1847051]
</blockquote>

<blockquote>
"Instead of reducing input gain you can increase the Compressor Threshold. (...) All it does is shift the curve. The compression ratio doesn't change so it's the same as lowering input gain." [https://forum.fractalaudio.com/threads/gain-enhancer-appreciation-thread.154697/post-1841088]
</blockquote>

<blockquote>
(York Audio) "Here’s a hot tip for the edge of breakup fans out there. Set the amp’s input drive to where it’s basically clean, then edge up the Gain Enhancer until it breaks up the way you want when you hit it hard. Playing hard gives you big juicy chords, and lighter pick attack cleans it up while still sounding full. You get more sustain than if you just set the input drive hotter." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841963]
</blockquote>

<blockquote>
"If it's a very clean tone you won't hear anything. It's designed to enhance the gain of medium to high gain sounds." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-15-00-public-beta-1.168197/post-2020299]
</blockquote>

<blockquote>
"This will accentuate pick attack. Lower the gain and use your picking technique to dynamically control the gain." [https://forum.fractalaudio.com/threads/what-are-some-amp-and-drive-modes-that-work-well-for-getting-a-lowest-possible-amount-of-gain-modern-metal-sound.168212/post-2020291]
</blockquote>

<blockquote>
"If I'm playing softly I like it. At louder volumes I don't use it. That is, btw, precisely the intent as it simulates the acoustic reinforcement of a guitar played near a loud amp." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2051698]
</blockquote>

<blockquote>
"The gain enhancer is an algorithm that attempts to recreate the effect of playing in front of an amp. What I did was measure the spectrum of a guitar and then compared that to the spectrum when played in front of an amp. The physical feedback into the guitar is marked. I don't remember the exact numbers but it was at least several dB in the midrange. So what happens when you play in front of an amp is that the sound waves hit the guitar and reinforce the tone. It's a positive feedback loop which effectively increases (enhances) the gain in the midrange. When playing through monitors at low volumes or headphones you lose all that so the gain enhancer can be used to simulate the feedback loop."
</blockquote>

For more information see the '[https://forum.fractalaudio.com/threads/the-modelers-dont-clean-up-with-the-volume-knob-myth.154557 The "Modelers Don't Clean Up with the Volume Knob" Myth]' Tech Note.

Other parameters are:

;'''Threshold''' : Threshold sets the threshold of Output Compression. A lower value causes compression to occur for quieter signals.

;'''Clarity''' : Clarity is used in conjunction with the other Output Compression parameters, this adjusts the bass response of the compressor and can be used to add clarity to the low end.

=Legacy parameters=

[[image:Rip.png|link=|100px]]

==CATHODE FOLLOWER TIME / RATIO==

This was removed in firmware Ares 5 and later.

Attack time of the compressor and the maximum amount of compression with lower values giving more compression.

==CHARACTER==

No longer available in firmware Ares and later. Firmware 20 and later for the Axe-Fx III introduced the Dynamic Distortion block.

Extremely powerful “inverse homomorphic filters”. When playing softly these dynamic filters have little effect on the sound. As the amount of distortion increases, the influence of these filters increases. The Character Frequency control sets the center frequency of the filters while the Character control sets how pronounced the effect is. For example, to darken the tone when playing harder, one might set the frequency to 10 kHz and the amount to -5. Setting the amount to +5 will make the tone brighter when playing hard. The amount defaults to zero whenever an amp type is selected. This control is similar to Dynamic Presence and Dynamic Depth but the frequency is adjustable.

<blockquote>"The "Character" parameters are two of the most powerful advanced parameters available but I bet almost no one uses them. My secret formula: Character Frequency: 3000 - 5000 Hz, adjust to taste, Character: -0.5 to -1.0, adjust to taste." [https://forum.fractalaudio.com/threads/my-secret-formula.85426/] </blockquote>

<blockquote>"It is highly dependent on the amount of gain. This formula is designed for an "80's" lead tone. I use on for my JCM800 preset because I find JCM800s get shrill as you turn the gain up. It also works well with the SLO 100 and Recto models. The Character parameters control an "inverse homomorphic filter" which is a term I coined to describe a type of homomorphic signal processing. This filter is distortion dependent. The more distortion there is the more pronounced the effect of the filter. It's analogous to contrast and edge detection in image processing. The processing is dependent on the dynamic range of the image." [http://forum.fractalaudio.com/threads/my-secret-formula.85426/page-2#post-1036134] </blockquote>

<blockquote>"Added a new mode to the “Character” controls in the Amp block. A Char Type of “Dynamic” engages an exciting new mode of tone control. This can be used to fatten or scoop the tone as a function of picking strength. For example, set the Type to Dynamic, Char Freq to 450.0, Char Q to 0.7 and Char Amt to 4.0. This will cause the tone to get fatter and thicker as you play hard but without getting honky when playing soft."</blockquote>

==MOTOR DRIVE==

Removed from the Amp block in firmware Quantum 9 and later.

Available as a Cab block parameter on the Axe-Fx II.

Models the effect of high power levels on the speaker.

<blockquote>(Quantum 7.0) "Improved Motor Drive algorithm. New algorithm more accurately models the compression of guitar loudspeakers by factoring in the reactive aspects of the compression. The Motor Drive simulation is available in both the Amp block and Cab block now. It is recommended to use the simulation in the Amp block when using an FRFR configuration as the Amp block simulation uses the speaker resonance information in the calculations whereas the Cabinet block uses fixed values. When using a conventional guitar cab, or a hybrid configuration with monitoring via a conventional guitar cab and speaker emulation to FOH, the Motor Drive in the Cabinet block can be used instead. The simulation in the Amp block also has the advantage of being independent of the block’s output Level control. Gain monitoring of the Motor Drive is available on the MIX page of the Cabinet Block and the PWR DYN page of the Amp block. In the case of the Amp block the monitoring is available when the Motor Drive parameter is selected. Note that typical guitar speakers have around 3-6 dB of compression when driven hard with American speakers being on the low end of that range and British speakers being on the high end. Some speakers can exhibit even more compression than this with compression amounts of 8 dB or more depending upon the magnetic materials used and the construction of the speaker motor. The thermal time constant of the virtual voice coil is adjustable using the “Motor Time Const” parameter. Typical guitar speakers are anywhere from 0.05 to 1.0 seconds depending upon the mass of the voice coil and the materials used."</blockquote>

<blockquote>"Set it to 4.5 and rip the knob off." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-8-00-public-beta.126728/page-10#post-1508219]</blockquote>

When using two UltraRes cabs in a preset, don't use Motor Drive with only one of them, because this will cause a hollow sound.

<blockquote>"Motor drive isn't EQ. It models efficiency reduction due to thermal effects." [https://forum.fractalaudio.com/threads/anyone-using-speaker-drive-or-motor-drive-since-about-6-0.60651/#post-757563] And: "What I have found is that thermal compression is somewhat noticeable and measurable. This is modeled by the Motor Drive parameter." [https://forum.fractalaudio.com/threads/question-for-the-v11-beta-testers.73859/page-3#post-904487]</blockquote>

<blockquote>"Motor Drive will cause compression if not set to zero (as it models driver compression). Otherwise the cab block is completely linear and will not cause any compression." [http://forum.fractalaudio.com/threads/pick-attack-issues-thread-deleted.62238/page-2#post-772637]</blockquote>

<blockquote>"Motor Drive simulates power compression due to voice coil heating." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-6-02-public-beta.122103/page-4#post-1452979]</blockquote>

<blockquote>"Guitar loudspeakers are intentionally designed to compress. FRFR speakers do compress a bit but not nearly to the extent that guitar speakers do." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-02-public-beta.125473/page-5#post-1493261]</blockquote>

<blockquote>"Makes edge-of-breakup tone stupid easy." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-02-public-beta.125473/page-6#post-1493298]</blockquote>

<blockquote>"Speaker Drive models the magnetic compression (which is actually distortion) that occurs due to the nonlinear speaker excursion vs. applied voltage. Motor Drive models the change in power transfer due to heating of the voice coil. When the voice coil heats up the speaker sensitivity decreases, in some cases quite dramatically." [http://forum.fractalaudio.com/threads/speaker-drive-vs-motor-drive.125541/page-2#post-1494537]</blockquote>

<blockquote>"The thermal time constant of a typical guitar speaker is about 0.52 seconds. Magnetic time constants are zero." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-02-public-beta.125473/page-13#post-1494250]</blockquote>

<blockquote>"So what I've done for the final release is put Motor Drive in BOTH the Amp block and the Cab block. If you're strictly FRFR then you can use the Amp block. If you are using a conventional guitar cab or a hybrid configuration (convention cab for monitoring and direct to FOH) then you can use the Cab block. Doing it in the Amp block also has the advantage that the speaker resonance information in the Amp block is used to calculate the frequency dependent heating whereas the Cab block uses a fixed set of data that is representative of a typical speaker. Finally I've made the time constant adjustable. I did some more calculations and measurements and found that a typical guitar speaker is actually lower than what I had previously calculated because thinner wire is used than I was assuming. Regardless you can now set the thermal time constant to get whatever response rate feels best. When using the Motor Drive in the Amp block it's before the output Level control so you don't have to worry about the behavior changing when you adjust the Level knob." [http://forum.fractalaudio.com/threads/speaker-drive-vs-motor-drive.125541/#post-1494518]</blockquote>

<blockquote>"The actual value for a particular speaker is all over the map. The time constant is proportional to the mass and the thermal resistance of the voice coil. Both these values can vary widely. 200 ms is based on a typical theta of 1 degree C/W and a mass of 10g." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-02-firmware-release.125625/page-10#post-1495722]</blockquote>

<blockquote>"The formula is tau = M * C * theta where M = mass, C = specific heat of the voice coil material (typically copper) and theta = thermal resistance between the voice coil and the magnet gap." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-02-firmware-release.125625/page-11#post-1496045]</blockquote>

==PI BIAS SHIFT==

No longer available in firmware Ares and later.

<blockquote>(Quantum 7.00) "New algorithm also includes bias shifting which results in more harmonic spectrum variation with input amplitude. This improves feel, “knock” and creates sweeter single note soloing. The new “PI Bias Shift” parameter controls the amount of phase inverter bias shift. Note that some real amps are “spitty” in nature due to PI bias shifting, i.e. Trainwrecks, and the new algorithm is designed to replicate that behavior accurately. If you find the behavior undesirable reduce the PI Bias Shift value as desired although this will reduce authenticity."</blockquote>

==PICK ATTACK==

No longer available in firmware Ares and later.

Controls a sophisticated dynamic range processor that operates on leading edge transients. Negative values reduce pick attack while positive values enhance it.

On the Axe-Fx III and FM3, turn down the various Bias Excursion parameters for a similar effect as decreasing Pick Attack. [https://forum.fractalaudio.com/threads/how-to-reduce-pick-attack.152058/post-1809849]

<blockquote>"It doesn't have any particular frequency. Pick attack is impulsive so, by definition, it contains all frequencies. The standard approach to reducing attack is to use dynamics processing. The Axe-Fx II has a Pick Attack parameter which can be used to reduce the attack but the AX-8 does not have this parameter. You can try using the Gate/Expander to soften the attack." [http://forum.fractalaudio.com/threads/how-to-eq-out-pick-attack.118497/#post-1410629]</blockquote>

==TRANSFORMER GRIND==

No longer available in firmware Quantum 9 and later.

<blockquote>(Quantum 3.0) "Improved Amp block output transformer modeling. New model more accurately simulates dynamic core losses and leakage inductance. The “Xfrmr Grind” knob controls the intensity of the effect. Higher values result in more high frequency response and a more “open” sound. Very high values can yield a raspy, spitty tone common in vintage and/or low wattage amps. Modern “big iron” amps tend to have low values. Note that the audibility is dependent upon how hard the virtual power amp is driven and is more noticeable as the MV is increased. Also note that the effect in real amps is highly dependent on the speaker. Some speaker/transformer combinations exhibit significant high frequency dynamic boost while other combinations yield almost none. As always use your ears as the final determinant. Note: The Transformer Grind parameter will be set to a default value and the Dynamic Presence parameter will be reset to 0.0 for any presets created with previous firmware."</blockquote>

<blockquote>"Transformer Grind is what you want to get that top-end sizzle. Dynamic Presence is one of my "Inverse Homomorphic" filters and only approximates the dynamic presence boost found in some amps. Transformer Grind is an authentic model of what actually happens in those amps." [http://forum.fractalaudio.com/threads/q3-01-to-2-04-conversion.114090/#post-1364689]</blockquote>

<blockquote>"Some amps interact with some speakers resulting in a dynamic high frequency boost. It creates an aggressive, biting distortion. It depends on the amp (the amp's output transformer in particular) and the behavior of the speaker as it deviates from it's rest position. You can simulate this using the Transformer Grind parameter." [http://forum.fractalaudio.com/threads/raw-amp-sounds-anyone-know-how-to-get-them.121460/page-2#post-1445818]</blockquote>

==CATHODE FOLLOWER TYPE==

No longer available in firmware Ares 5.00 and later.

Selects between “Authentic”, which accurately models the compression in a tube amp, and “Ideal” which is an idealized distorting compressor. The idealized type is more focused and has tighter bass whereas the authentic type is bolder and looser. High gain players may prefer the ideal type due to its tight character.

<blockquote>"The “Ideal” cathode follower type is no longer supported as it is incompatible and has been removed from the GUI."</blockquote>

==DYNAMIC DAMPING==

No longer available in firmware Ares 10.00 and later.

Also known as Dynamic Impedance. Controls the reduction in plate impedance as a function of grid voltage. Higher values result in a more focused and forward midrange.

<blockquote>(Axe-Fx II) "Improved power amp modeling via improved modeling of the plate impedance of the power tubes. This gives tighter bass (less flub) and warmer highs when the virtual power amp is heavily driven (higher Master Volume settings). This also improves the feel and dramatically increases the “3-dimensionality” of the tone. The plate characteristics are adjustable via the new Dynamic Damping parameter. This parameter defaults to the appropriate value when an amp model or power tube type is selected. The power tube type presets the Dynamic Damping parameter as well as several internal parameters."</blockquote>

==CATHODE FOLLOWER HARDNESS==

No longer available in firmware Ares 14.00 and later.

<blockquote>(Owners Manual) "For models that use cathode followers, this adjust the shape, warmth, smoothness and decay of cathode follower distortion."</blockquote>

<blockquote>"The displayed value is 7.5 but the internal value is 0.75." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-9-04-firmware-release.134473/#post-1589113]</blockquote>

<blockquote>"It varies with brand of tube. The mean is around 7.5. Lower settings are smoother, higher settings are more aggressive." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-9-04-firmware-release.134473/#post-1589136]</blockquote>

==DYNAMIC DEPTH and DYNAMIC PRESENCE==

Removed in "Cygnus" amp modeling firmware. Firmware 20 and later for the Axe-Fx III introduced the Dynamic Distortion block.

Dynamic Presence:

<blockquote>(Owners Manual) "This models output transformer leakage inductance, resulting in a brightening of the tone when the virtual power amp is pushed. When playing softly or at lower gains, the influence of this control is lessened. Note that this only affects the power amp modeling and is dependent on the degree of power amp overdrive. This control can also be set negative to cause the tone to darken when playing harder. This can help dial in the sweet spot of an amp model. As the Master is increased, an amp becomes more liquid, more compressed and easier to play. However, the highs may get overly compressed, causing the amp to sound too dark. Dynamic Presence allows you to get the desired power amp drive and feel without high frequency loss."</blockquote>

Another way to look at it: distortion-dependent treble filter.

Dynamic Depth:

<blockquote>(Owners Manual) "Analogous to Dynamic Presence, above. This increases low frequencies when the virtual amp is being pushed. While real amps don’t display this behavior, it is a cool tone-shaping tool."</blockquote>

<blockquote>(firmware 10) "Dynamic Depth: analogous to the Dynamic Presence control, this increases or decreases low frequencies when the virtual power amp is being pushed. While real amps don’t display this behavior, it is a valuable tone-shaping tool. Another way to look at it: a distortion-dependent bass filter." </blockquote>

The FM3 hasn't supported Dynamic Presence and Dynamic Depth from the start.

About missing support for Dynamic Depth on the FM3:

<blockquote>"Certain features were removed to allow the algorithms to run including the bias tremolo, input dynamics processing, and several other inauthentic enhancements." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-62#post-28446966]</blockquote>

<blockquote>"We removed all the superfluous stuff (bias tremolo, dynamic presence/depth, etc.) in order to get the core amp modeling to run on the slower processor." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-68#post-28450968]</blockquote>

<blockquote>"The Axe-Fx III contains various algorithms that allow you to enhance the amp modeling that don't exist on a real amp. I.e. dynamic presence/depth, input dynamic processing, etc. These were removed to allow the core amp modeling to run on the lower-powered processor." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-70#post-28454394]</blockquote>

<blockquote>"Dynamic Depth is a non-physical tweak. It uses what I call "Inverse Homomorphic Processing". Anything other than zero is deviating from authentic. It's not wrong to use it but it will be less accurate." [https://forum.fractalaudio.com/threads/legacy-amp-models-consider-revisiting-full-honest-request-and-opinion.160349/post-1920107]</blockquote>

[[category:Axe-Fx2]]
[[category:Axe-Fx3]]
[[category:FM3]]
[[category:FM9]]
[[category:AX8]]
[[category:Sounds]]
[[category:All]]

Amp models list

2023-12-02T14:59:25Z

James-F: /* PLEXI 100W HIGH (1969 100W Marshall Plexi) */

This page lists all amp models in Fractal Audio’s current generation of guitar processors, with brief additional information (based on "Cygnus" amp modeling). Depending on the firmware, some models may not yet be available on every device. The information also partly applies to the previous generation of modelers (Axe-Fx II series and AX8). Many of the amp models are featured in [[Factory presets]].

[http://wiki.fractalaudio.com/axefx2/index.php?title=Yeks_Guide_to_the_Fractal_Audio_Amp_Models Yek's Guide to the Fractal Audio Amplifier Models] provides in-depth information about many amp models.

Fractal Audio owns all the amps on which the models are based, except the Bludotone. [https://thegearforum.com/threads/fractal-audio-firmware-update-thread.673/page-54#post-46151]

[[file:Allamps.jpg|500px]]

__TOC__

==1959SLP JUMPED (100W Marshall Super Lead Plexi 1959 reissue)==

[[file:SLP.png|300px]]

Models:
* Normal and Treble channels jumpered
* Normal channel
* Treble (High) channel

[[Cabinet models list| Cab:]] Marshall 4x12 (G12M, G12H)

Volume Normal, Volume Treble, Bass, Middle, Treble, Presence

Power tubes: EL34

# (about the Plexi model in the Standard/Ultra): "One of the first mods people make to real 'Plexi' Marshalls is to "clip the bright cap". The bright cap varied over the years, supposedly depending on what was lying around in the shop. The model defaults to the bright cap in the circuit. If you turn off Bright you're effectively clipping the bright cap. The bright cap in Marshalls can be very bright and harsh. However, if you crank the Master you might find the extra brightness helps compensate for the power amp getting darker."
# (about fizz) "It's the way a Plexi is supposed to sound. That's due to the cathode follower. That raspiness helps it cut through in a mix. I own three of them and they are that fizzy." [https://forum.fractalaudio.com/threads/high-end-fizz-is-this-normal.43598/#post-576475]
# "Don't be afraid to turn the bass all the way down or the treble all the way up. Just like with the actual amp. For example, on the normal channel of a Plexi most people turn the bass way down. Otherwise it's too flubby."
# "The old one (Plexi 100w model) has a 2.7K cathode resistor on the first stage, the new one (1959SLP) has an 820 ohm." [https://forum.fractalaudio.com/posts/1111403]
# "I based the SLP on using it with G12H(55) speakers which have a resonance of 55 Hz. When mounted in a typical cab the resonance will be in the low 70s. There is no right or wrong. Whatever sounds best." [https://forum.fractalaudio.com/posts/1159759]
# "My settings for a "typical" Plexi tone are Bass: 2, Mid: 8, Treble 7.5. Adjust Presence to taste." [https://forum.fractalaudio.com/posts/1179420]
# "What you are hearing is output transformer high frequency resonance. Old Plexis didn't do this because they had good transformers. New transformers are crappy and resonate at the cutoff frequency because they are underdamped. This causes a raspy, fizzy texture to the distortion. The transformer resonance is adjustable but the parameter isn't exposed to the user. When you turn it up you get that same squishy rasp that you are hearing. For the Plexis I have the damping set to flat with no resonance because that's how our vintage Plexis measure. Our 50W is a little underdamped but people complain about raspy high frequencies so I erred on the safe side." [http://forum.fractalaudio.com/threads/dimed-real-plexi-vs-dimed-simulation-q8-01.127161/page-2#post-1513888]
# "When modding Marshalls for higher gain sometimes the modder will decrease the input frequency response to reduce noise and fizziness. You can do this by reducing the high-cut frequency in the input EQ. Or you can use a high-shelf filter which is a little more subtle. Another technique is to put a capacitor across the second-to-last triode stage. This is the "Triode 1 Plate Freq" parameter. Reduce this to around 2 kHz to start which is typical of amps like an SLO100, etc." [https://forum.fractalaudio.com/threads/dialling-in-the-marshalls.143682/post-1707222]
# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]
# [[Amp_block#NEGATIVE_FEEDBACK|Negative feedback value]]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-1959slp-marshall-slp1959.111321/ Yek's write-up]

==1959SLP NORMAL==

# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]

==1959SLP TREBLE==

# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]

==1987X JUMPED (50W Marshall 1987X reissue) ==

[[file:1987X.png|300px]]

Models:
* Normal and Treble channels jumpered
* Normal channel
* Treble channel

[[Cabinet models list | Cab:]] Marshall 4x12 (G12M, G12H)

Volume Normal, Volume Treble, Bass, Middle, Treble, Presence

Notes: see 1959SLP

Power tubes: EL34

# "The 1987x doesn't have the 0.68uF cap on the last triode. Gives it a smoother distortion." [https://forum.fractalaudio.com/posts/1000388]
# "Our reference amp has no bright cap. Looks like it was that way from the factory. There are no signs it was removed. The location in the circuit board is empty and the solder joints do not appear to have been disturbed." [https://forum.fractalaudio.com/threads/1987x-bright-switch-off-by-default.145332/post-1718899]
# [[Amp_block#NEGATIVE_FEEDBACK|Negative feedback value]]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-1987x.111362/ Yek's write-up]

==1987X NORMAL==

==1987X TREBLE==

==5153 100W BLUE (EVH 5150-III)==

[[File:5153.png|300px]]

5150-III models:
* 100W amp, Blue channel
* 100W amp, Green channel
* 100W amp, Red channel
* 100W Stealth amp, Blue channel
* 100W Stealth amp, Green channel
* 100W Stealth amp, Red channel
* 50W amp, Blue channel

[[Cabinet models list| Cab:]] 5150 4x12 or 2x12 (G12H, G12EVH)

Gain, Low, Mid, High, Volume, Presence, Resonance (only on 50w model)

Power tubes: 6L6

# "IMO, it's a very good amp. The build-quality is great and the design is very good. It is similar to the previous versions but voiced a bit different. Personally, I think all of the 5150's have more gain stages than necessary which just makes for unnecessary failure points but the "OMG, this amp has sooo many toobz it must sound awesome" marketing makes it understandable. It's incredibly heavy though." [https://forum.fractalaudio.com/posts/679483]
# "A 5150 uses a fixed bias with no adjustment. Depending on the tubes used the bias can run from average to cold. The model uses average. Some people like a colder sound. If you prefer your amps biased cold, then reduce the bias parameter to taste." [https://forum.fractalaudio.com/posts/742231]
# "The 50W version has a different input network than the 100W version for that channel. The 50W version has about twice the gain as a result. Otherwise things are pretty similar. You can simulate this using the Input Trim knob." [https://forum.fractalaudio.com/posts/1042144]
# "The red channels (of 50w and 100w models) are identical." [http://forum.fractalaudio.com/threads/5153-50w-blue-red.106463/#post-1273739]
# "Some amps have a fixed depth circuit, e.g. 5153, Freidman BE/HBE, Dirty Shirley, TripTik, Tucana, et. al. In these cases the Depth knob will default to a value that corresponds to the fixed circuit." [https://forum.fractalaudio.com/threads/lets-talk-about-the-depth-control.88747/#post-1071598]
# "The 5150 models are absolutely identical to our reference amp." [https://forum.fractalaudio.com/threads/legacy-amp-models-consider-revisiting-full-honest-request-and-opinion.160349/post-1919792]
# "The Normal Gain input has a very low input impedance, about 44K in addition to cutting the gain in half. Use the Input Impedance feature of the Input block to simulate. Try 32K." [https://forum.fractalaudio.com/threads/why-fractal-is-good-for-my-sanity-and-my-wallet.167246/post-2008937]
# "A 5150's presence control has almost no effect from 0 to 7. After 7 the treble increases rapidly. The taper of the presence control in a 5150 is a log30 IIRC (maybe log10, I'd have to check my notes). If anything it should be linear. Ideally it should be reverse log. Our model uses a reverse log taper which gives a nice, smooth response over the full range. In most cases a reverse log taper would be the ideal taper. However reverse log taper pots are uncommon, difficult to source and cost more. Why they chose a log taper in the 5150 is a mystery. Since the power amp has similarities to a Marshall perhaps Eddie wanted the presence control to behave like his old Marshalls. Another possibility is the designer felt the amp was too bright with all knobs at noon (and a linear taper presence pot) and changed the taper to reduce the brightness." [https://www.thegearpage.net/board/index.php?threads/blind-test-mesa-dual-rectifier-vs-mystery-modeler-update-results-revealed.2208367/post-31639265]
# "Amps with low amounts of negative feedback in the bass region are sensitive to the impedance curve. The 5153 is one of these amps due to its NFB circuit." [https://thegearforum.com/threads/evh-amp-vs-axe-fx-qc-and-tmp.3593/post-133163]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-5153-evh-5150-iii.111404/ Yek's write-up]

==5153 50W BLUE==

==5153 100W GREEN==

==5153 100W RED==

==5153 100W STEALTH BLUE (EVH 5150III 100S 100W)==

[[File:5153S.jpg|300px]]

# "The Blue channel gain knob affects the Red channel somewhat. I modeled it with the Blue channel gain knob at noon." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-23-04-release.199875/post-2491407]
# "The Red channel has much more gain but the Gain pot taper is very different. The Red channel has a 5A taper, while the Blue channel has a 30A taper so at noon it will appear as though the Blue channel has more gain." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-23-04-release.199875/post-2491406]

==5153 100W STEALTH GREEN==

==5153 100W STEALTH RED==

==59 BASSGUY BRIGHT (1959 Fender narrow-panel Tweed Bassman, 5F6-A)==

[[file:bassman.jpg|300px]]

Models:
* Bright channel
* Normal channel
* Jumpered channels

[[Cabinet models list | Cab:]] Fender 4x10 with Jensen Alnico 25W P10R or 40W P10Q

Volume Normal, Volume Bright, Bass, Middle, Treble, Presence

Power tubes: 6L6/5881

# [before 19.02 for the Axe-Fx III] "There is no "High" channel on a 59 Bassman. There is a Normal and Bright channel. The Bright channel model is selected by turning on the Bright switch. The models are based on the higher gain input (the "1" input). To simulate the lower gain input simply set Input Trim to 0.5." [https://forum.fractalaudio.com/posts/1109139/]
# [19.02 and later for the Axe-Fx III] "Updated 59 Bassguy and 5F8 Tweed models to include both Drive controls."
# "All the Fender models except the 59 Bassman and 5F8 Tweed don't have cathode followers." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-00-beta-3.148907/page-3#post-1764588]
# ("Cygnus" amp modeling) "The Bassman was reworked using an original 59 Bassman 5F6-A as a reference. This has a 12AY7 input buffer which has less gain than the reissue which uses a 12AX7A (7025 actually, same thing)."
# ("Cygnus" amp modeling) "The Bassman and Deluxe Tweed models are both modeled using a 12AY7 as the input buffer. The Preamp Tube Type parameter only affects the tubes after the input buffer." [https://forum.fractalaudio.com/threads/12ay7-preamp-tube-for-tweed-deluxe-and-bassman-models.175834/post-2135435]
# "The input to the second 12AX7 is a summing node. Both volume controls affect the signal. If you plug into the Bright input the Normal volume control will also control the volume to some degree and change the frequency response." [https://forum.fractalaudio.com/threads/bassman-how-do-the-way-the-2-drive-controls-interact.181986/post-2232557]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-59-bassguy-59-fender-tweed-bassman-5f6-a.111275/ Yek's write-up]

==59 BASSGUY JUMPED==

==59 BASSGUY NORMAL==

==59 BASSGUY RI JUMPED (Fender 59 Bassman LTD Vintage Reissue)==

[[file:FENDER_BASSMAN_RI.jpg|275px]]

Model:
* Jumpered channels

[[Cabinet models list | Cab:]] Fender 4x10 with Jensen Alnico 25W P10R or 40W P10Q

Volume Normal, Volume Bright, Bass, Middle, Treble, Presence

Power tubes: 6L6

# See 59 Bassguy.
# "There are quite a few differences between a 5F6-A and the reissue: [https://forum.fractalaudio.com/threads/bassman-how-do-the-way-the-2-drive-controls-interact.181986/post-2358853]
## 12AX7A vs. 12AY7 input tube.
## Different tone stack (this is a big one).
## Different presence network.
## Different B+ voltage.
## 6L6s vs 5881s (minimal difference).

==5F1 TWEED (Fender narrow-panel Tweed Champ, 5F1)==

[[file:champ.jpg|300px]]

Model:
* Single channel

[[Cabinet models list| Cab:]] Fender 1x8

Volume

Power tubes: 6V6

# "This particular amp exhibits a unique breakup characteristic due to its single-ended design and simple circuit."

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-5f1-tweed-fender-champ.111067 Yek's write-up]

==5F1 TWEED EC (2011 Fender EC Vibro-Champ)==

[[file:EC-Vibro-Champ.jpg|300px]]

Model:
* Single channel

[[Cabinet models list| Cab:]] Fender 1x8

Volume, Tremolo

Power tubes: 6V6

# "The circuit is slightly different than the original 5F1. It has cathode bypass caps giving it more gain." [http://forum.fractalaudio.com/threads/fractal-audio-amp-models-5f1-tweed-fender-champ-5f1.111067/page-2#post-1508977]
# "It's a single-ended power amp with negative feedback and bias tremolo. Subtle is the only possibility with this configuration. Bias tremolo works by modulating the quiescent operating point of the power tubes. With a single-ended power amp with negative feedback the gain doesn't change much as you change the operating point, hence the tremolo effect is subtle. Bias tremolo works best on amps with little to no negative feedback." [https://forum.fractalaudio.com/threads/fw-q8-5f1-tweed-ec-4-scene-preset-vid-demo.126829/post-1509387]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-5f1-tweed-fender-champ.111067 Yek's write-up]

==5F8 TWEED BRIGHT (Keith Urban's 1959 Fender narrow-panel high-power "big box" Tweed Twin, 5F8==

[[file:5f8-2.jpg|300px]]

Models:
* Bright channel
* Jumpered channel
* Normal channel

[[Cabinet models list| Cab:]] Fender 2x12 (P12N, but Keith Urban's cab has Two-Rock speakers)

Volume Bright, Volume Normal, Presence, Middle, Bass, Treble

Power tubes: 6L6

# [before firmware 19.02 for the Axe-Fx III] Engage the Bright switch for the Bright channel
# "Based on a 1959 Fender Twin Amp. This particular model is based on Keith Urban’s “#1”. Thank you Keith for allowing us the use of your prized amplifier."
# "All the Fender models except the 59 Bassman and 5F8 Tweed don't have cathode followers." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-00-beta-3.148907/page-3#post-1764588]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-5f8-tweed-keith-urbans-high-power-fender-twin-amp.111123 Yek's write-up]

==5F8 TWEED JUMPED==

==5F8 TWEED NORMAL==

==65 BASSGUY BASS (1965 Blackface Fender Bassman head, AB165)==

[[file:ab165.png|300px]]

Models:
* Bass channel
* Normal channel

[[Cabinet models list | Cab:]] Fender 2x12 (Oxford)

Volume, Bass, Treble, fixed Presence circuit (Presence should be at 10), Bright switch (Normal channel only)

Power tubes: 6L6

# "Has a pissed-off Marshall vibe to it." [http://forum.fractalaudio.com/posts/490912]
# "The 65 Bassguy was matched to a 65 Bassman that Dweezil sent me. It's a vicious amp that sounds more like a Plexi than a Fender. It's the infamous AB165 circuit which is very crunchy and bright and does not sound like your typical Fender." [https://forum.fractalaudio.com/threads/am-i-the-only-one-who-noticed-that-some-amps-have-alot-more-gain.51123/page-2#post-658833]
# "It's a crazy sounding amp, sounds nothing like your typical Fender." [https://forum.fractalaudio.com/threads/another-v10-preview.62489]
# "The AB165 uses 7025 preamp tubes (which are relabeled 12AX7). The phase inverter, however, is a 12AT7. The secret to the AB165 is the summing stage. It uses a inverting summing amp to sum the Normal and Bass inputs. This stage clips, because of all the local negative feedback, quite hard." [http://forum.fractalaudio.com/posts/

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-65-bassguy-65-blackface-fender-bassman-ab165.111298/ Yek's write-up]

==65 BASSGUY NORMAL==

==6G12 CONCERT (1960 Brownface Fender Concert, 6G12)==

[[file:6G12.jpg|300px]]

Model:
* Vibrato channel

[[Cabinet models list | Cab:]] Fender 4x10 with Jensen Alnico 25W P10R or 40W P10Q, or ceramic 25W C10R, or Oxford

Volume, Bass, Treble, Presence, Vibrato (not modeled)

Power tubes: 6L6

# "Super 6G4 is a Brownface Fender Super. Concert 6G12 is a Brownface Fender Concert. They are very similar amps and both sound "old". They definitely have that early 60's vibe to them." [https://forum.fractalaudio.com/threads/axe-fx-ii-firmware-17-02-released.93734/#post-1124507]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-6g12-concert-60-fender-brownface-concert.111224/ Yek's write-up]

==6G4 SUPER (1960 Brownface Fender Super, 6G4)==

[[file:6G4.jpg|300px]]

Model:
* Vibrato channel

[[Cabinet models list | Cab:]] Fender 2x10 with Jensen Alnico 25W P10R, 40W P10Q or Oxford 10K5, or a Fender 2x12

Volume, Bass, Treble, Presence, Vibrato (not modeled)

Power tubes: 6L6

# "Super 6G4 is a Brownface Fender Super. Concert 6G12 is a Brownface Fender Concert. They are very similar amps and both sound "old". They definitely have that early 60's vibe to them." [https://forum.fractalaudio.com/threads/axe-fx-ii-firmware-17-02-released.93734/#post-1124507]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-6g4-super-60-fender-brownface-super.111173 Yek's write-up]

==AC-20 12AX7 BASS (Morgan AC20 Deluxe)==

[[file:morgan.jpg‎|300px]]

Models:
* 12AX7 Bass
* 12AX7 Treble
* EF86 Bass
* EF86 Treble

[[Cabinet models list | Cab:]] Morgan 1x12 (G12 Alnico Blue), DynaCab available

Volume, Cut, Sun/Moon switch (= Bright switch), Brilliance switch (= Bass Cut), power scaling (not modeled), EF86/12AX7 switch

Power tubes: EL84

# "The AC-20 model is based on the amp with the power scaling at maximum power which effectively disables it (and sounds best IMO)." [https://forum.fractalaudio.com/posts/1079502]
# "The AC-20 has power scaling. The Axe-Fx II does not model the power scaling circuit as there is no point in that." [https://forum.fractalaudio.com/threads/power-level-ac-20.89488/#post-1079494]
# "As with the real amp I dial in quite a bit of Hi-Cut." [http://forum.fractalaudio.com/threads/recommend-an-amp-for-p-w.106093/#post-1268874]
# "I think an AC-20 does the Vox thing better than Vox." [https://forum.fractalaudio.com/threads/recognition-and-respect-to-cliff-and-his-morgan-ac20.155040/post-1844685]
# "AC-30's have a poorly designed cathode follower. The bias point is totally wrong and crushes one side of the signal considerably. IMO either the cathode resistor should be 100K or the plate resistor of the preceding stage should be higher, 200K. The clipping is extremely asymmetric. Too much IMO. A little asymmetry is good because it warms things up. Too much causes excessive even-order harmonics which makes things fuzzy and indistinct. The clipping is so asymmetric on an AC-30 that it's almost a half-wave rectifier. You can tweak this by adjusting the Preamp Bias point and/or lowering the Cathode Follower Compression. Or you can lower the Harmonics value which reduces the asymmetric distortion. The downside of that is that it then overdrives the phase inverter causing blocking distortion from excessive bias excursion. Another thing to try is to increase the Grid Clipping value which will add a little headroom. Start with the Bias point. AC-30's are very sensitive to the tube type and part tolerances. A tiny change in the bias point can make a big difference. The default bias point is based on Mullard ECC83 tubes. I prefer the AC-20 because it doesn't have a cathode follower so doesn't suffer from these problems. The cathode follower in an AC-30 doesn't even do all that much. Normally you use a cathode follower to preset a low-impedance source to the tone stack but the tone stack in an AC-30 doesn't present that great of a load anyways." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-02.148983/page-11#post-1767187]
# "One reason I like the AC-20 is that it runs the tubes hotter and exhibits less crossover distortion." [https://forum.fractalaudio.com/threads/papery-buzz-under-some-models.149193/page-2#post-1772639]
# "The Sun/Moon equals the Bright Switch. The Bass/Treble switch would be different amp models. So AC20 EF86 Bass model would be the Bass/Treble switch in the Bass position, the switch on the back in EF86 position and then the Bright switch on the model is the Sun/Moon switch on the amp." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-10-00.154850/post-1842330]
# "So I was testing the next beta and selected the AC-20. Was hearing a lot of ghost notes compared to the old algorithm (in the debug build I can select between algorithms with a hidden parameter) and figured that couldn't be right. Hooked up the real AC-20 and, sure enough, ghost notes galore at the same settings." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-0-public-beta.154714/post-1840850]
# "Our reference amp is a head with matching 1x12 cab." [https://forum.fractalaudio.com/threads/recognition-and-respect-to-cliff-and-his-morgan-ac20.155040/post-1844744]
# "The normal channel on a Vox would be closest to the Morgan. The Brilliant channel is a "Top Boost" which means it has a tone stack and a significant midrange cut. The normal channel has no tone stack. You can't compare a a Morgan AC20 to the Brilliant channel of an AC30 and declare that one sounds better than the other. Totally different preamps and, therefore, different sound. Personally I think the AC20 is a better amp. Better made, better quality components, much better transformers. If you want that chimey AC30 sound you put an EQ before it and suck out some mids." [https://forum.fractalaudio.com/threads/how-accurate-is-fractals-amp-modeling.168786/post-2064189]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-ac-20-morgan-ac20-deluxe.111453/ Yek's write-up]

==AC-20 12AX7 TREBLE==

==AC-20 EF86 BASS==

==AC-20 EF86 TREBLE==

==ANGLE SEVERE 1 (Engl Savage 120)==

[[File:savage.png|300px]]

Models:
* Lead channel, Contour switch OFF (boosts lower midrange around 500 Hz)
* Lead channel, Contour switch ON (boosts from 1200 Hz and cuts lower midrange)

[[Cabinet models list | Cab:]] Engl 4x12 (V30, V60)

Gain (input sensitivity), Lead (degree of distortion), Lead Boost switch, Contour switch, Bass, Middle, Treble, Rough/Smooth switch (not modeled), Master, Presence, Depth Boost switch

Power tubes: 6550

# "From noon and up it's a presence boost, from noon down it's a presence cut." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-1-03-firmware-release.106931/page-12#post-1280997]
# "(...) Engl Savage presence network which reduces negative feedback as the control is turned down causing an increase in volume." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-5-cygnus-firmware-public-beta-2.170901/post-2059273]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-angel-severe-engl-savage-120.111501/ Yek's write-up]

==ANGLE SEVERE 2==

==ARCHEAN (100W PRS Archon)==

[[File:Archon.jpg|300px]]

Models:
* Archean: Lead channel with Bright switch OFF
* Archean Bright: Lead channel with Bright switch ON
* Archean Clean: Clean channel

Master, Bass, Middle, Treble, Bright switch, Volume, Depth, Presence, Output Power (not modeled)

Power tubes: 6L6

# "You have to crank the MV on the real amp. The preamp is very "dry" so to get the juices flowing the power amp needs to be working hard. This also smooths out that funky midrange." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-14-01.165716/page-10#post-1990153]
# "I think part of the reason the real Archon needs to be cranked is because the power supply is too stiff. It's got six (!!!) big caps filtering the B+. That's too much filtering IMO unless you're playing at arena volumes. If I were to make a modification to the amp it would be a switch to disconnect four of those caps so the supply is more bouncy at moderate volumes. Maybe also a tube rectifier to add some more sponge." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-14-01.165716/page-10#post-1990169]
# Based on 100W amp [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-14-01.165716/post-1990412]

[https://forum.fractalaudio.com/threads/fractal-audio-amp-models-archean-based-on-prs-archon.165751/ Yek's write-up]

==ARCHEAN BRIGHT==

==ARCHEAN CLEAN==

==ATOMICA HIGH (Cameron Atomica)==

[[file:atomica.jpg|300px]]

Models:
* Low gain input
* High gain input

[[Cabinet models list | Cab:]] cabinet with G12H speakers

Thump, Presence, Bass, Middle, Treble, Master, Gain, Edge (not modeled), 3-way Gain Voice switch

Power tubes: EL34

# "The Atomica can tolerate high MV because it is a "Jose-style MV". The Jose-style MV imparts a very high source resistance to the tone stack which causes much more insertion loss and therefore lower drive level into the power amp." [https://forum.fractalaudio.com/posts/748843]
# "Cameron amps are basically modified Marshalls. The Atomica is essentially a slightly modified JCM800 with a Jose-style zener clipper." [https://forum.fractalaudio.com/threads/dialling-in-the-marshalls.143682/page-5#post-1706652]
# (fuzzy tone with Bright on) "That's the way those amps sound with the bright switch on. It's due to the location of the drive control. Turn down the Preamp Bias Excursion to reduce it. The problem with those "Mid Stage Drive" designs using a Plexi drive network is that if you bypass the drive pot with a cap (bright cap) you also bypass any grid stoppage and the next stage goes into blocking distortion very easily. There's essentially a straight shot into the grid for all the high frequencies. Friedman probably realized this and that's why there's no bright cap on the BE as the BE is very similar to the Atomica." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2052829]
# "The Cameron is a genuine Cameron. I don't know the lineage of the Atomica." [https://forum.fractalaudio.com/threads/are-any-of-the-cameron-models-of-mark-cameron-built-amps.199792/#post-2489827]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-atomica-cameron-atomica.111547 Yek's write-up]

==ATOMICA LOW==

==BAND-COMMANDER (1968 Silverface/Blackface Fender Bandmaster head, AB763)==

[[file:bandmaster.jpg|300px]]

Model:
* Vibrato channel

[[Cabinet models list| Cab:]] Fender 2x12

Vibrato channel: Volume, Bright switch, Treble, Bass, Tremolo

Power tubes: 6L6

# "The vibrato channel is loaded down by the vibrato circuit. The normal channel isn't. You can probably get close using the vibrato channel model by increasing the MV trim." [http://forum.fractalaudio.com/threads/maroon-5-axe-fx-iii-awesomeness.146287/page-2#post-1730430]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-band-commander-68-fender-bandmaster-ab763.111596 Yek's write-up]

==BIG HAIR (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "It was a total guess. I just tuned it by ear. It's just my idea of what 80's hair metal might sound like." [http://forum.fractalaudio.com/posts/700269/]
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-big-hair.111635/ Yek's write-up]

==BLANKENSHIP LEEDS (Dweezil Zappa's Blankenship Leeds 21)==

[[file:blankenship.jpg|300px]]

Model:
* Single channel

[[Cabinet models list|Cab:]] 2x10, 1x12, 2x12 (G12M)

Volume, Tone, Tremolo

Power tubes: EL84

# "Based on a Blankenship Leeds which is a boutique version of an 18W Marshall. This particular amp is known for sounding “big” despite being relatively low power."
# "The model was matched to Dweezil's amp. He loaned it to me because it was one of his favorite amps and I can see why. It's a really cool amp."
# "The amp has no hi-cut circuit therefore the control won't do anything. Neither will the Depth."
# "18W Marshalls are kind of a bad design. The phase inverter drives the power tubes too hard which results in excessive bias excursion.” [http://forum.fractalaudio.com/threads/marshall-1974x.121516/#post-1446363]
# "The phase inverter design causes significant bias excursion. That bias excursion, however, causes the amp to sound more open when driven hard (at the expense of crossover distortion)." [https://www.thegearpage.net/board/index.php?threads/is-digital-getting-too-real.2275913/post-32977457]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-blanknshp-leeds-blankenship-leeds-21.111681/ Yek's write-up]

==BLUDOJAI CLEAN (Bludotone Ojai)==

[[File:ojai.png|300px]]

Models:
* Clean channel with PAB (Pre-Amp Bypass) OFF
* Overdrive channel with PAB OFF
* Overdrive channel with PAB ON

[[Cabinet models list|Cab:]] Bludotone 1x12, 2x12 (G12-65, EVM)

Volume, Overdrive Level (Overdrive channel only), Treble, Middle, Bass, Master, Presence. Switches: Bright, Mid (not modeled), Rock/Jazz (not modeled). Footswitchable Pre-Amp Bypass (PAB) which bypasses the tonestack (Bass / Middle / Treble)

Power tubes: 6L6

Forum member AustinBuddy, owner of the original amp:
# "The model is of a 100w 6L6 BludoDrive Ojai by Bludotone amps, using Fractal's MIMIC process. The Ojai has the same schematic as the famous "Tan" boutique amp played by Robben Ford. It pairs well with the factory Rumble 4X12 cabinet. On the Ojai there is a bright cap on the Master Volume. As you turn the MV down, it will get thinner. This makes the MV even more sensitive than usual since there’s another interaction going on. To get the most range out of this amp, experiment with Master Volume and listen how it interacts with low or high Drive settings, similar to the real amp. The breakup range/tones between is wide and dynamic and can respond to your playing dynamics, getting crunchier as you dig in and cleaner as you play lighter. The amp's Bass response should increase noticeably as you turn up the Master Volume from the default MV position. Pair it with a G12-65H speaker. Cab Pack 17 has many choices (full disclosure, I produced 5 of the 6 Cabs in that Cab Pack). The BludoMix Cab in factory firmware is a 1x12 Alnico dual port cab, and will sound good but perhaps a tad darker (great for Jazz) on clean sounds than the G12-65H will. Now, if you like, put a Zen drive in front on the BludoClean amp....or a boost...and listen to how that clean channel wakes up fast for grittier leads and touch-responsiveness. For BludoLead, take the Lead default amp values. Put the Master Volume on 5. Put drive at 4-5 and Overdrive at 4-5, and experiment with the tone stack swaps above. If you want the amp to feedback effortlessly on a note, raise the overdrive setting higher combined with the gain, provided you have sufficient volume coming out your speakers to hit your guitar pickups in a reinforcing loop, it will do it! Throw a boost or Zen drive on that, if you like..." [http://forum.fractalaudio.com/threads/dumble-ford-2-again.105028/page-2#post-1267280]

# "The tone stack in the PAB models is a neutral tone stack which is the same as lifting the ground. Put all knobs at noon if you want authentic." [http://forum.fractalaudio.com/threads/love-3-0-but.147215/page-3#post-1739726]
# "The tone stack in the PAB models is a neutral tone stack which is the same as lifting the ground. Put all knobs at noon if you want authentic. Unlike the amp, however, you can actually adjust the tone controls and something will happen. In the virtual realm we can have lifted tone stacks that actually still work." [http://forum.fractalaudio.com/threads/love-3-0-but.147215/page-3#post-1739726]
# "Pre, mid and post aren't absolute locations. They're relative to the particular model. In the Lead model there is a buffer and then three gain stages IIRC. Pre means the tone stack is before the three gain stage in this case. Changing it to Mid would put it after the first gain stage. In the Clean model there is only a buffer and one gain stage. In this case mid means the stack is between the buffer and gain stage. Changing it to pre would put it before the buffer. Since there are only two tubes pre would indicate before the buffer which is not what we want. In the PAB model there is no tone stack so I put a neutral tone stack after the gain stages (with a fixed attenuation after the buffer). This allows the most flexibility. The HRM case the neutral tone stack is replaced by a Marshall tone stack." [http://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-3-01.147229/page-2#post-1739969]
# "The real amp has Overdrive Volume (sometimes labeled Ratio) and a Master Volume. The models assume the Overdrive Volume is at maximum." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-16-01-cygnus.172911/post-2091820]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-bludojai-bludotone-ojai.111724/ Yek's write-up]

==BLUDOJAI LEAD==

Formerly: BLUDOJAI LEAD 1

==BLUDOJAI LEAD PAB==

Formerly: BLUDOJAI LEAD 2

==BOGFISH BROWN (Bogner Fish preamp)==

[[File:fish.png‎|300px]]

Models:
* Strato channel
* Brown channel

Master, Gain, Bass, Mid, Treble

Power tubes: EL34

# "I used the power amp models from the XTC." [https://forum.fractalaudio.com/threads/bogner-strato-and-brown-poweramp-modeling.76238/#post-931081]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-bogfish-bogner-fish.111780/ Yek's write-up]

==BOGFISH STRATO==

==BRIT 800 2204 HIGH (50W Marshall JCM 800 2204)==

[[file:2203.png|300px]]

Model:
* Single channel, low and high inputs

[[Cabinet models list |Cab:]] Marshall 4x12 (G12M, G12H, G12-75, V30)

Pre-Amp, Bass, Middle, Treble, Presence, Master

Power tubes: EL34

# "It is a very bright model. However, it sounds exactly like the amp it was based on. If it is too bright, you can adjust the various tone controls and parameters to reduce the brightness to your tastes. They are designed to be run loud and the brightness decreases as the MV is increased. The sound of 80's hair metal for sure." [https://forum.fractalaudio.com/threads/afxii-jcm800-model.38498/#post-525964]
# "The saturation switch switches in a zener diode clipping stage right before the tone stack. This is the Arrendondo Mod." [http://forum.fractalaudio.com/threads/axe-fx-ii-technical-questions-thread.35997/page-38#post-494304]
# "Rips my head off here. I have to turn the presence way down. Check the MV. Too high and will get muddy." [http://forum.fractalaudio.com/threads/jcm-800-sounds-a-bit-muddy-with-fw-6-0-tips.51063/#post-657800]
# "That "interference" is due to all the treble peaking used in the design. JCM800s have quite a bit of treble boost. When you first attack the string the note is unpitched. It's basically a brief explosion of noise. The treble boosting amplifies the upper frequencies of this noise burst which is what you hear. However, when you playing in a loud mix that treble boosting helps the sound cut. Modern designs use more carefully crafted treble boosting to retain the cut but tame some of the harshness of the attack. This is accomplished typically by putting a capacitor in parallel with the plate resistor(s) which rolls off around a few kHz. This preserves the treble boost in the upper midrange but softens the attack. I believe the SLO100 was one of the first amps to do this. You can see this in the Axe-Fx II as your Triode Freq parameters. You can soften the JCM800 attack by lowering the Triode Freq values. Most modern hi-gain designs use some form of HF rolloff like this. Another reason is that JCM800s use relatively low amounts of negative feedback (which is why they're so loud). This causes a treble boost in the power amp. Increase the Damping parameter to increase the negative feedback." [http://forum.fractalaudio.com/threads/cliff-how-can-i-ever-have-doubted-you.63107/#post-781950]
# "Those amps are all designed to get their character from power amp distortion. If you don't push the power amp all you are hearing is the preamp which is voiced to be trebly. The power amp then compresses the highs and the sound gets fatter." [https://forum.fractalaudio.com/posts/1235311]
# "It's a vertical input Canada export version. I went through several before settling on this one as it was the best sounding by far." [https://forum.fractalaudio.com/threads/jcm-800-question.103215/#post-1235691]
# (about moving Master volume to the post phase inverter) "It's called PPI MV or the "Lar-Mar Mod"." [http://forum.fractalaudio.com/threads/dial-in-popular-mods.119757/#post-1424257]
# "At low MV the source resistance into the PI is low which raises the highpass frequency due to the coupling cap and raises the lowpass frequency due to the Miller capacitance and snubber. As you increase the MV the source resistance increases which decreases both of these things. As you keep raising the MV the source resistance then starts to decrease as you get above 50% of the pot value." [http://forum.fractalaudio.com/threads/setting-the-master-volume.119903/page-2#post-1428935]
# "Some of them are really dull. We have two 50 watters. One is a Canadian export with bat-handle switches and sounds glorious. All nasty and spitty and full of "artifacts". The other is a "regular" one with the rocker switches. It sounds like it has a blanket over it in comparison. Our model is based on the Canadian one. Oh, and I should add that someone removed the bright cap from the Canadian one. Probably because it's so nasty with it in. I installed a new one to bring it back to it's original glory. The key to JCM800's is to crank the MV to overcome the brightness of the preamp." [http://forum.fractalaudio.com/threads/help-requested-new-afx-xl-and-digital-distortion-in-the-sound.123815/page-2#post-1478884]
# "Our reference amp had the bright cap removed by a previous owner. I put it back in. I like it on, even with a bright guitar." [http://forum.fractalaudio.com/threads/jcm800-with-our-without-bright-switch.131049/#post-1552301]
# "When modding Marshalls for higher gain sometimes the modder will decrease the input frequency response to reduce noise and fizziness. You can do this by reducing the high-cut frequency in the input EQ. Or you can use a high-shelf filter which is a little more subtle. Another technique is to put a capacitor across the second-to-last triode stage. This is the "Triode 1 Plate Freq" parameter. Reduce this to around 2 kHz to start which is typical of amps like an SLO100, etc." [https://forum.fractalaudio.com/threads/dialling-in-the-marshalls.143682/post-1707222]
# "The reference amp used for our model is a Canadian Export version (with the "bat handle" power switches). We have two JCM800s and this particular amp sounds way better than the regular one with the rocker type power switches. It's not as harsh with a warmer high end." [https://forum.fractalaudio.com/threads/nux-mg300-vs-fm3-comparison.165102/post-1980841]
# "We have two of them. One sounds amazing, the other not so much. The model is based, naturally, on the amazing sounding one." [https://forum.fractalaudio.com/threads/buttons-functioning-as-on-amps.170531/post-2052806]
# "JCM800s sound better with a hot bias IMO. The problem is the plate voltage is too high so when you set the bias higher the dissipation goes up and tube life is shortened. IMO they should've made the plate voltage around 420V. That would allow a hotter bias with longer tube life at the expense of slightly less volume but JCM800s are ungodly loud anyways so..." [https://forum.fractalaudio.com/threads/why-your-amp-doesnt-sound-like-our-amp.172907/post-2091305]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-800-and-brit-800-mod-jcm-800.111876 Yek's write-up]

==BRIT 800 2204 LOW==

==BRIT 800 2203 HIGH (100W Marshall JCM 800 2203 JMP)==

[[file:JCM8002203.jpg|300px]]

Model:
* Single channel, low and high inputs

[[Cabinet models list | Cab:]] Marshall 4x12 (G12M)

Presence, Bass, Middle, Treble, Master Volume, Pre-Amp Volume

Cliff's 2203 is an unmodified unit with metal toggle switches and faded brown grille cloth. It has vertical inputs and drake transformers.

Power tubes: EL34

# "It's a vertical input model." [https://forum.fractalaudio.com/threads/marshall-jmp-100w.198803/post-2481704]
# [https://forum.fractalaudio.com/threads/marshall-jmp-100w.198803 Forum discussion]
# [https://wiki.fractalaudio.com/wiki/images/0/05/JCM8002203.jpg Picture of the modeled amp]

==BRIT 800 2203 LOW==

==BRIT 800 #34 (50W Marshall JCM 800 with virtual Santiago #34 modifications)==

[[File:Logo small.png]]

Custom Fractal Audio model

Notes: see Brit 800

Power tubes: EL34

# "Based on the “Santiago #34” modifications."
# "The Brit 800 #34 does a better Slash than the AFS100 IMO. The AFS100 models are based on the actual amp but I think my version of #34 sounds more like AFD. I based the model on information I've collected over the years about the mods that were done." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-00-firmware-release.124944/page-5#post-1486357]
# "The Brit 800 #34 has a ton of treble boost and will squeal with certain guitars and/or certain IRs and/or certain types of amplification. Nature of the beast. No other amp has anywhere near the amount of treble boost. The AFD100 amp that Marshall produced years later (that was supposed to be a #34 copy) has nowhere near the amount of treble boost and has a huge snubber cap on the PI (which rolls off the treble). My gut tells me that they did this because they feared there would be too many reports of pickup squeal (or the amps would be too unstable at high gain)." [http://forum.fractalaudio.com/threads/squealing-like-mad.132058/#post-1563723]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-800-and-brit-800-mod-jcm-800.111876 Yek's write-up]

==BRIT 800 MOD (50W Marshall JCM 800 with virtual modifications)==

[[File:Logo small.png]]

Custom Fractal Audio model

Notes: see Brit 800

Power tubes: EL34

# "Based on popular modified Marshall JCM800. These mods make the amp “heavier” and less strident."

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-800-and-brit-800-mod-jcm-800.111876/#post-1338002 Yek's write-up]

==BRIT AFS100 1 (Marshall AFD100SCE)==

[[file:AFD.jpg|300px]]

Models:
* Amp in mode "#34"
* Amp in mode "AFD"

[[Cabinet models list |Cab:]] Marshall 4x12 (V30)

Gain, Bass, Middle, Treble, Presence, Master, #34/AFD switch, Depth (Brit Super model only)

Power tubes: 6550

# "I have an actual Slash signature model and spent a lot of time measuring, listening and comparing." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-2-01-firmware-release.111657/page-8#post-1337247]
# "The Brit 800 #34 does a better Slash than the AFS100 IMO. The AFS100 models are based on the actual amp but I think my version of #34 sounds more like AFD. I based the model on information I've collected over the years about the mods that were done." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-00-firmware-release.124944/page-5#post-1486357]
# "The Brit 800 #34 has a ton of treble boost and will squeal with certain guitars and/or certain IRs and/or certain types of amplification. Nature of the beast. No other amp has anywhere near the amount of treble boost. The AFD100 amp that Marshall produced years later (that was supposed to be a #34 copy) has nowhere near the amount of treble boost and has a huge snubber cap on the PI (which rolls off the treble). My gut tells me that they did this because they feared there would be too many reports of pickup squeal (or the amps would be too unstable at high gain)." [http://forum.fractalaudio.com/threads/squealing-like-mad.132058/#post-1563723]
# "The amount of treble peaking needed for an amp at a given drive is highly dependent on the guitar. For example my guess is that the AFD100 was designed around a Les Paul. With my Suhr it's much too bright because that's a very bright guitar. So one of the first things I do with the AFS100 model is turn down the bright cap a bit." [https://forum.fractalaudio.com/threads/firmware-1-11.140004/page-2#post-1660177]
# "Reference amp is a Slash AFD100 Signature Special Collector's Edition #76. Hand-signed by Slash with COA." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-19-00-beta-3.180388/post-2207142]
# "Default MV is quite high in that model which will mask the effect of the Presence control since the power amp is distorting heavily (I find that amp sounds best with the power amp driven hard). Turn the MV down and you'll notice the Presence control will have much more effect." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-00.189017/post-2343032]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-afs100-and-brit-super-marshall-afd100.111919/ Yek's write-up]

==BRIT AFS100 2==

==BRIT BROWN (custom model, producing the Plexi "Brown Sound")==

[[File:Logo small.png]]

Custom Fractal Audio model

[[Cabinet models list | Cab:]] Marshall 4x12 (G12M, G12H, G12-EVH, V30, JBL D120)

Power tubes: EL34

# "The Brit Brown was built by ear." [https://forum.fractalaudio.com/threads/evhs-original-plexi-and-the-fas-brit-brown-amp.81986/#post-995265]
# "Brit Brown is my personal take on what the ultimate "Brown" plexi should sound like. It's based on a 100W SLP with Arredondo mods and a few little voicing tweaks." [https://forum.fractalaudio.com/posts/1152917]
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]
# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-brown-and-fas-brown.111974/ Yek's write-up]

==BRIT JM45 (Marshall JTM 45)==

[[file:JTM.png|300px]]

Models:
* Treble (High) channel
* Normal and Bright channels jumpered

[[Cabinet models list |Cab:]] Marshall 4x12 (G12M, G12H)

Volume Normal, Volume High Treble, Bass, Middle, Treble, Presence

Power tubes: EL34

# "They had no Master Volumes so people rarely got the Drive past 3.00 since it would melt your face. Without the specter of having your skin flayed off as is afforded by a model of the amp, the temptation is to turn the Drive way up. When you do this the low notes get very muddy. Single notes can form an almost perfect square wave which will sound like a synthesizer." [http://forum.fractalaudio.com/threads/jm45-and-jm45-jump-sound-horrible-for-low-e-and-a-strings-not-a-bug.76286/#post-931633]
# "Our reference amp has a 100 pF bright cap. Many JTM45s did not but I think they sound better with one. A JTM45 with a bright cap is similar to a Superlead. If you want the Channel 1 sound with an Axe-Fx use the Brit JM45 Jump model and turn the Treble Drive knob all the way down." [http://www.thegearpage.net/board/index.php?threads/fractal-vs-helix-the-comparison-series-made-by-yours-truly.1757067/page-2#post-22868763]
# "When modding Marshalls for higher gain sometimes the modder will decrease the input frequency response to reduce noise and fizziness. You can do this by reducing the high-cut frequency in the input EQ. Or you can use a high-shelf filter which is a little more subtle. Another technique is to put a capacitor across the second-to-last triode stage. This is the "Triode 1 Plate Freq" parameter. Reduce this to around 2 kHz to start which is typical of amps like an SLO100, etc." [https://forum.fractalaudio.com/threads/dialling-in-the-marshalls.143682/post-1707222]
# "The very first models used a 5881, after that KT66 then EL34." [https://forum.fractalaudio.com/threads/jtm45-bug.164255/post-1969445]
# (negative feedback) "I've seen JTM45s with 27K off the 16-ohm tap. That's a lot of feedback. In this case you would then double the feedback on top of the 3.3 so 9.9 or so." [https://forum.fractalaudio.com/threads/negative-feedback.188769/post-2340464]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-jm45-marshall-jtm-45.112030/#post-1339718 Yek's write-up]

==BRIT JM45 JUMPED==

==BRIT JVM OD1 GREEN (Marshall JVM410H)==

[[file:jvm.png|300px]]

Models:
* OD1 Green
* OD1 Orange
* OD1 Red
* OD2 Green
* OD2 Orange
* OD2 Red

[[Cabinet models list |Cab:]] Marshall 4x12 (V30 and G12H)

Master, Bass, Middle, Treble, Gain, Presence, Resonance, Reverb (not modeled)

Power tubes: EL34

# "IMO, the reason the JVM sounds good is the plate cap on the second-to-last triode. That smooths out the tone considerably. The second-to-last triode is associated with "Triode 1 Freq" in the advanced parameters. You can adjust this to simulate adding a cap to the plate. The other thing that helps the tone is the 220K plate resistor on the last triode. This shifts the bias point down vs. a "classic" Marshall. Unfortunately the bias points aren't exposed to the user." [https://forum.fractalaudio.com/threads/holy-crap-the-new-jvm-sounds-great.44628/#post-588030]
# "The JVM has a huge plate resistor on the cathode follower, the JS does not." [https://forum.fractalaudio.com/threads/jvm-sounding-weird.150157/page-2#post-1785256]
# (about OD 1 Orange and Red compression):
#* "Real amp does this. Poor cathode follower design."
#* (why doesn't this happen with the Green channel) "Because the Green channel only has one tone stack hanging off the cathode follower."
#* (why doesn't this happen with the OD2 channels) "OD1 has a different tone stack. The gains are the same. The models are very accurate." [https://forum.fractalaudio.com/threads/jvm-410-model-issue.156087]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-jvm410-marshall-jvm410.112092/ Yek's write-up]

==BRIT JVM OD1 ORANGE==

==BRIT JVM OD1 RED==

==BRIT JVM OD2 GREEN==

==BRIT JVM OD2 ORANGE==

==BRIT JVM OD2 RED==

==BRIT PRE (Marshall JMP-1 preamp)==

[[image:Cliff JMP-1.jpg|300px]]

Model:
* OD channel

Volume, Gain, Bass, Mid, Treble, Presence, Bass Shift (not modeled)

Power tubes: EL34

# "The two channels have preset tone stacks. Then there is a digitally controlled 4-band graphic EQ which is the B/M/T and Presence. This technique gets around the problem of trying to digitally control a tone stack. The Triaxis uses LDRs in place of potentiometers. The Soldano X-99 uses motorized pots. Both techniques being expensive. So the JMP-1 uses a fixed tone stack and then a digitally controlled graphic EQ. The Axe-Fx model of the JMP-1 is "better" in the sense that the tone controls control the tone stack rather than a graphic EQ. You then have the separate graphic EQ to further tailor the sound. What I didn't do, and why people probably feel the model differs, is "normalize" the tone controls so that with B/M/T at noon the tone stacks match. On the Axe-Fx you might need to set the Bass to 3, Mid to 7, etc. to get the tone to match. I just used a standard Marshall tone stack whereas the JMP-1 uses a standard Marshall tone stack but the pots are replaced with fixed resistors but those values don't necessarily correspond to the pots at noon." [https://forum.fractalaudio.com/posts/1228348]
# "The JMP-1 tone controls have more range than the actual preamp. The preamp has about +/- 8 dB for each tone control while the model has the standard +/- 12 dB."
# "Brit Pre is a legacy model from the original Axe-Fx. It's not as accurate but some people really liked it so we kept it and created new models for the Ares/Cygnus platform." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-19-02-public-beta.181521/post-2224791]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-pre-and-brit-jmpre-1-marshall-jmp-1.112139/ Yek's write-up]

==BRIT SILVER (100W Lerxst Omega / Marshall 2555 Silver Jubilee)==

[[file:Lerxst.jpg|300px]]

Model:
* Lead channel

[[Cabinet models list |Cab:]] Marshall 4x12 (V30)

Presence, Bass, Middle, Treble, Gain, Master

Power tubes: EL34

# "Our reference amp for the Silver Jubilee is actually not a Silver Jubilee. It's a Lerxst Omega that Alex Lifeson gave me." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-5-cygnus-firmware-public-beta-2.170901/post-2058221]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-silver-marshall-silver-jubilee.112184 Yek's write-up]

==BRIT STUDIO 20 (Marshall SV20H)==

Model:
* Marshall Studio Vintage 20 (20W version of 1959 Super Lead Plexi)

Notes: see 1959SLP

Power tubes: EL34

# "The schematic doesn't show it but there's a cathode bypass cap on one of the triode stages." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2320134]
# "It's a cool little amp. It's very loud though. It's not really a "bedroom amp" IMO. Good for smaller gigs, rehearsals, etc." [https://forum.fractalaudio.com/threads/comparing-brit-20-to-real-sv20h-anyone-done-it.188338/post-2336176]

==BRIT SUPER (Marshall AFD100 schematics)==

[[file:AFD.jpg|300px]]

Model:
* Marshall AFD100 in AFD mode

Notes: see Brit AFS100

Power tubes: EL34

# "Brit Super model is based on the Marshall AFD100." [https://forum.fractalaudio.com/threads/great-sound-with-my-splawn-nitro-4cm-im-blown-away.55549/#post-700713]

==BUDDAH DUOMASTER (Budda Twinmaster)==

[[File:Logo small.png]]

Model:

* Single channel

[[Cabinet_models_list|Cab]]: 1x15 Budda Phat 15 or 1x12 Budda Phat 12

Bass, Treble, Volume

Power tubes: EL84

# "I bought a Budda Twinmaster, pulled it apart and traced the circuit since I couldn't find a schematic for it anywhere. Funky amp. Paraphase phase inverter. Weird Bridge-T sorta tone stack. I'm convinced the feedback is connected to the wrong node but I quadruple-checked and my schematic is definitely correct. I think it was probably a mistake but then they said "Hmmm, but it sounds good so don't fix it"." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-12-cygnus-firmware-public-release-candidate.172027/post-2075782]
# "The Buttery model was REPLACED by a Budda Twinmaster model. Totally different model." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-12-cygnus-firmware-public-release-candidate.172027/post-2076481]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-buttery-budda-twinmaster.112228/ Yek's write-up]

==CA3+ CLEAN (Custom Audio Amplifiers 3+ SE preamp)==

[[file:CAE.png|300px]]

Models:
* Clean channel
* Rhythm channel
* Lead channel

Gain, Bass, Middle, Treble, Master, Bright switch. Active tube EQ: Treble and Bass

Power tubes: EL34

# "The CA3+SE model is basically an OD100." [https://forum.fractalaudio.com/threads/is-the-suhr-od-100-in-the-axe.75090/#post-918169]
# "An OD100 is the head version of a CAE 3+."
# "That's a "James" tone-stack. You can find simulations on-line but typically you would get close using shelving filters with frequencies of 100 and 1000 Hz." [http://forum.fractalaudio.com/threads/cae-3-se-global-eq-anybody-know-the-freqs.33103/#post-461976]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-ca3-cae-3-se.112399/ Yek's write-up]

==CA3+ LEAD==

==CA3+ RHYTHM==

==CAMERON CCV 1A (Cameron CCV-100)==

[[file:ccv.jpg|300px]]

Models:
* (1A) Channel 1, less gain
* (1B) Channel 1, more gain
* (2A) Channel 2, Bright1 switch left, Bright2 switch left, Gain Style switch left
* (2B) Channel 2, Bright1 switch left, Bright2 switch right, Gain Style switch left
* (2C) Channel 2, Bright1 switch left, Bright2 switch left, Gain Style switch right
* (2D) Channel 2, Bright1 switch left, Bright2 switch right, Gain Style switch right [https://forum.fractalaudio.com/threads/just-a-heads-up.97371/#post-1168902]

Channel 1: Punch (= Resonance / Depth), Presence, Master, Bass, Middle, Treble and Gain, 3-way Voicing switch (resonance), 3-way Dark switch (presence), 3-way Gain Style switch (“Jose Master” gain/clipping), 3-way Bright switch (less noticeable at higher gain settings)

Channel 2: Punch (= Resonance / Depth), Presence, Solo Master, Master, Bass, Middle, Treble, two Gain controls, 3-way Gain Style switch, two Bright switches, Drive switch

The 2C and 2D models have lower output because of the Sat switch position.

Power tubes: EL34

# "The amp was modeled with the Voicing switch in the middle position. The "Dark" switch is the Negative feedback control. Set Negative Feedback to 3.6 to reproduce the switch in the middle position. Set it to 9.8 to reproduce the switch in the right position. 5.0 for left position (default). The amp has a dozen switches and, frankly, there isn't a lot of difference between some of the settings. The Drive switch sounds virtually identical whether left or right. I don't like it in the middle." [https://forum.fractalaudio.com/threads/just-a-heads-up.97371/#post-1168912]
# (about the Drive knob) "Our reference amp has a linear taper pot so the behavior is very abrupt. The model matches the amp extremely accurately (as do all G3 models)." [https://forum.fractalaudio.com/threads/fw-18-01-camron-ccv-not-a-bug.97385/#post-1168811]
# "It's a bit of a quirky amp and kind of a one-trick pony but, man, what a trick." [https://forum.fractalaudio.com/threads/fw-18-01-camron-ccv-not-a-bug.97385/#post-1168922]
# "Yes, it's actually not a very high gain amp. The topology is very similar to a JCM800." [https://forum.fractalaudio.com/threads/fw-18-01-camron-ccv-not-a-bug.97385/#post-1169347]
# "The key to the CCV sound is the Sat Switch." [https://forum.fractalaudio.com/posts/1169015]
# "Camerons have linear taper MV and you need it with them because the signal level into the power amp is very low due to the Jose topology." [https://forum.fractalaudio.com/threads/mv-poll.170996/post-2059425]
# "Humans perceive high frequency thermal noise as hiss. The more gain the more hiss. Diezel's have a lot of filtering. Large grid stoppers, plate capacitors, etc. This reduces the bandwidth which lowers the hiss. Camerons are pretty much wide open. Small grid stoppers or bypass caps on the grid stoppers, no plate caps, etc." [https://forum.fractalaudio.com/threads/why-lower-gain-cameron-ccv-amp-model-feels-more-noisy-than-much-higher-gain-herbie-3.188658/post-2339783]
# "The Cameron is a genuine Cameron. I don't know the lineage of the Atomica." [https://forum.fractalaudio.com/threads/are-any-of-the-cameron-models-of-mark-cameron-built-amps.199792/#post-2489827]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-cameron-ccv.112486/ Yek's write-up]

==CAMERON CCV 1B==

==CAMERON CCV 2A==

==CAMERON CCV 2B==

==CAMERON CCV 2C==

==CAMERON CCV 2D==

==CAPT HOOK 1A (Hook Captain 34)==

[[file:capt34.jpg|300px]]

Models:
* (1A) Channel 1, EQ Bypass switch OFF, Boost switch OFF
* (1B) Channel 1, EQ Bypass switch engaged (no Bass / Middle / Treble), Boost switch ON
* (2A) Channel 2, Edge switch OFF
* (2B) Channel 2, Edge switch ON
* (3A) Channel 3, Edge switch OFF
* (3B) Channel 3, Edge switch ON

[[Cabinet models list |Cab:]] Hook 2x12 or 4x12 (V30, G12H, G12-65, WGS)

Channel 1: Gain (with Pull function), Level, Bass, Mid, Treble, Boost switch (not modeled), EQ bypass switch, Bright switch. Shared: Presence and Balls

Channels 2 and 3: Gain, Level, Bass, Mid, Treble, Boost switch, Edge switch (changes tone stack). Shared: Presence and Balls

Power tubes: EL34

# "This amp uses a mu follower which yields a complex distortion with smooth decay. To simulate the Boost switch use the Boost switch in the amp block as it has the same amount of gain." [https://forum.fractalaudio.com/posts/1426113]
# "A mu follower is similar to a cascode configuration except the output is off the cathode instead of the plate. So the output impedance is lower." [http://forum.fractalaudio.com/threads/the-hook.120307/#post-1432379]
# (mimic Pull Gain on clean channel) "Just set the Tonestack Type to Hook Clean 2." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-5-00-firmware-released.120358/page-10#post-1433059]
# "The Capt. Hook's "thing" is that it's basically a JCM800 with the cathode follower replaced by a mu-follower. A mu-follower doesn't compress and distort like a cathode follower does. This results in the amp sounding more open and smoother." [http://forum.fractalaudio.com/threads/recommended-adjustment.133602/page-2#post-1579933]
# "The Hook Clean 1 is a Fender style tonestack which has a lot more insertion loss than the others." [https://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-5-00-firmware-released.120358/page-10#post-1433058]
# "The Hook uses a "mu follower" instead of a cathode follower. Cathode followers have low output impedance but distort quite easily. Mu followers address some of the problems of cathode followers." [https://forum.fractalaudio.com/threads/dialling-in-the-marshalls.143682/page-7#post-1708218]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-capt-34-hook-captain-34.119935 Yek's write-up]

==CAPT HOOK 1B==

==CAPT HOOK 2A==

==CAPT HOOK 2B==

==CAPT HOOK 3A==

==CAPT HOOK 3B==

==CAR ROAMER (Carr Rambler)==

[[file:rambler.jpg|300px]]

Model:
* Single channel

[[Cabinet models list |Cab:]] Carr 1x12 (Eminence Elsinore)

Volume, Treble, Middle, Bass, Pentode/Triode (not modeled), Reverb (not modeled), Tremolo

Power tubes: 6L6

# "It's basically a Deluxe Reverb preamp with a cathode bias 6L6 power amp and no negative feedback. Sort of a Fender-meets-Vox thing." [https://forum.fractalaudio.com/threads/carr.78974/#post-960532]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-car-roamer-carr-rambler.112529/ Yek's write-up]

==CAROL-ANN OD-2 (Carol-Ann OD-2)==

[[file:od2.jpg|300px]]

Model:
* Overdrive channel

Master, Pre Gain, Drive, Bass, Middle, Treble, Presence, Sparkle (not modeled), Shift switch (not modeled)

Power tubes: 6L6

# "CAs are definitely dark amps. Sound great though." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-10-cygnus-firmware-public-beta-7.171198/post-2066490]
# "If you like the base Dumble sound but want a little more gain without the fuzziness of a Fuchs try the Carol-Ann models." [https://forum.fractalaudio.com/threads/fuchs-ods-in-cygnus.172291/post-2081523]

Alan Phillips:
# "In the real world the OD2 is very very fussy on speaker choice too. The real world speakers of choice are EVM12L in a 1x12 rear ported and 2x12 with Celestion Classic Lead 80's. I found the 12L emulation did a pretty good job. Some of the others sounded so artificial with that model. Like a Rockman. Coupled with the right cab the emulated model does a good job of representing the basic tonal signature of the amp".
# "It's not a competitive model, it's a live demo of an OD2 as tweaked by me. Damn sight better than sound clips for auditioning to guys that haven't got the ability to get to a Dealer. Clearly it doesn't give you the full experience of the full amp, but is a good tonal taster. I repaired a Soldano SLO for him one day and when he came over my house to pick it up we just decided it would be a good idea to put a CA model in there. Having the actual builder involved kind of closes the loop fully. I'm happy to endorse that model because I put a lot of hours testing it and putting together a ton of technical information, fourier analysis graphs, frequency response graphs, schematics etc that would make validation of a mathematical model much easier. In reality even though the power amp and the preamp are modeled the pre-amp got the most effort. As I said in another thread, I tuned that by putting the axe in to the actual power amp of an OD2 and running that side by side with a full OD2. The final tweaks were made like that using parametric eq blocks that were hard coded in to the model. You could call that the icing on the cake and basically put the same level of tuning into the model as I do with a actual OD2. The only difference was I was using a GUI, not resistors and capacitors."
# "The OD2 and to some degree the OD3 uses HRM style gain staging with a Plexi PI and power amp. Thats common knowledge, I've talked about it in depth many times. I really liked the idea of driving the tonestack from a common cathode stage as opposed to a cathode follower like a Marshall because it got rid of some of the artifacts I don't like with say a JCM-800. Yes that's something that Dumble came up with that I have to give him major props for. I wanted an amp that would have a little more gain than a JCM-800 but with the character of a Plexi without any fizz or harsh upper mid/lower treble frequencies. Remember this was BEFORE anyone had even degooped or documented a Bluesmaster style circuit and the only thing Shad was building was his post count at AmpGarage asking about Dumble circuits. I do find it amazing it took other guys years to catch on with moving the pots to the front. It does require a bit more thought than just moving the pots as the ranges of those trimmers Dumble used is impractical when used as front panel controls (which they were not really intended to be). I do also agree with you that from a pure tone standpoint having nothing on the front panel is always going to be better. The JB100 model is basically an OD2 with the entire OD circuit on the board with predefined filters made up of quality components without adjustment through fragile trimmers. The OD2 was never designed to be put side by side in a Dumble clone fest in some guys living room with everyone playing their best Ford licks, it was designed to be used on stage for guys who played in cover/blues/wedding/classic rock bands. The seperate eq and the tube driven effects loop were added for that situation. I have always tried to avoid that association as much as possible because the average Dumble lover is typically looking for a particular set of tones that may or may not be found in this amp. Early customer interaction with guys like yourself made me want to make sure people knew it was not a tonal clone of a Dumble to avoid returns/misunderstandings. The OD-2 is not the best amp for those tones, I totally agree with you, but a Dumble or clone doesn't really do fast dampened power chords like the OD-2 will do either. On the other hand, it is much more suited for blues and classic rock, not the Ford/Carlton thing. Bear in mind that its function and tone that the average player is looking for, not a particular design architecture. The fact I did use an HRM style circuit obviously (and unfortunately) placed me in the Dumble category. However, 2500 amps later its not really seen that way any more as the CA's have always had their own thing going on tonally that is very much more in a modified Marshall vein. The newer models like the Triptik 2 have absolutely nothing in common with any Dumble, not even a common cathode driven tonestack. For anyone that has played a number of real Dumbles, there is a certain thing (I hear it more in the clean channel) that is uniquely his signature. There's a certain swirl to the clean tone that is always present in his amps. However the amp doesn't overdrive anywhere close to like what I like when pushed hard. For me I would rather focus on that tone in a Plexi Marshall, but who knows what the original guy he modified this for wanted. All of this hopefully explains why I have always shied away from the Dumble comparison thing, I was truly and honestly never trying to clone a Dumble." [https://www.thegearpage.net/board/index.php?threads/fuchs-ods-classic-whats-the-word.1845787/page-4#post-24506473]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-ca-od-2-carol-ann-od2.112259 Yek's write-up]

==CAROL-ANN TRIPTIK CLASSIC (Carol-Ann Triptik)==

[[file:triptik.jpg|300px]]

Models:
* Clean channel
* Classic channel
* Modern channel

[[Cabinet models list|Cab:]] Carol-Ann 1x12 (Scholz Classic)

Input Level, Drive on channels 2 and 3, Bass, Middle, Treble, Presence, Master, Classic/Modern voicing switching

Power tubes: EL34

# "This TripTik is badass. Dumble meets Marshall with a sprinkle of 5150 power amp." [https://forum.fractalaudio.com/threads/since-10-06-came-out.70996/#post-870346]
# "I think what people like about this amp is the same reason people like the BE/HBE. These amps share the same aggressive low-cut on the input and then add bass back in the power amp. This gives clear bass response without getting flubby."
# (speaker) "It's a Scholz Classic." [https://forum.fractalaudio.com/threads/axe-fx-ii-firmware-15-00-released.87350/page-7#post-1057172]
# "Some amps have a fixed depth circuit, e.g. 5153, Freidman BE/HBE, Dirty Shirley, TripTik, Tucana, et. al. In these cases the Depth knob will default to a value that corresponds to the fixed circuit." [https://forum.fractalaudio.com/threads/lets-talk-about-the-depth-control.88747/#post-1071598]
# "CAs are definitely dark amps. Sound great though." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-10-cygnus-firmware-public-beta-7.171198/post-2066490]
# "If you like the base Dumble sound but want a little more gain without the fuzziness of a Fuchs try the Carol-Ann models." [https://forum.fractalaudio.com/threads/fuchs-ods-in-cygnus.172291/post-2081523]

Alan Phillips from Carol-Ann:
# (Classic mode): "On the real amp, you would set the Input level at 2 O'clock and the Gain at 1 to 2 O'clock to get a great classic rock rhythm tone. It's not overly different in character to the modern setting, less gain and less low end essentially."
# "It does classic rock extremely well and has one of the best clean channels I've ever designed." [https://www.thegearpage.net/board/index.php?threads/carol-ann-od2r-the-best.1908068/#post-25776544]

[https://forum.fractalaudio.com/threads/fractal-audio-amp-models-ca-triptik-carol-ann-triptik.112303/ Yek's write-up]

==CAROL-ANN TRIPTIK CLEAN==

==CAROL-ANN TRIPTIK MODERN==

==CAROL-ANN TUCANA CLEAN (Carol-Ann Tucana 3)==

[[file:tucana.jpg|300px]]

Models:
* Clean channel
* Lead channel

Input Level, Bass, Mid, Treble, Gain (Overdrive channels), Master (all channels), Presence

Power tubes: KT88

# "One of the best amps in the world IMO. I have a Dumble and a Trainwreck and various other boutique amps and the Tucana is better than all of them." [https://forum.fractalaudio.com/posts/1153214]
# "Some amps have a fixed depth circuit, e.g. 5153, Freidman BE/HBE, Dirty Shirley, TripTik, Tucana, et. al. In these cases the Depth knob will default to a value that corresponds to the fixed circuit." [https://forum.fractalaudio.com/threads/lets-talk-about-the-depth-control.88747/#post-1071598]
# "CAs are definitely dark amps. Sound great though." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-10-cygnus-firmware-public-beta-7.171198/post-2066490]
# "If you like the base Dumble sound but want a little more gain without the fuzziness of a Fuchs try the Carol-Ann models." [https://forum.fractalaudio.com/threads/fuchs-ods-in-cygnus.172291/post-2081523]

Carol-Ann:
# "Now I can only speak for the actual amp, but my preference of speaker is a Celestion Creamback 65, though I gig these regularly with a 2x12 with Celestion T75's. Its pretty forgiving on speakers compared with some models. The foot controller and bias monitor are two of the wonderful features of the actual amp, but are both moot in the model......unless Cliff wants to model the effects of real world mains power fluctuations from place to place, but the 'green zone' of the bias monitor is 62-65% plate idle dissipation power and it measures and compensates for plate voltage and screen power , which means the real amp runs best at a slightly cooler bias. The bias monitor just allows you to set that consistently from venue to venue regardless of the main power." [https://forum.fractalaudio.com/posts/1035178]
# "It's very very difficult for anyone to get a bad tone out of the real amp. It's designed that way, the range and limits on the controls, even the biasmon system makes it difficult for even a very inexperienced player to FU. The real amp has a more British overtone to it due to the fact I am British and I designed it. The gain staging, overdrive voicing and output stage are night and day to ANYTHING Mesa, any owner of the real amp would attest to that." [https://forum.fractalaudio.com/posts/1049358]
# "The Tuc 3 is very very tolerant of most cabs and speakers, unlike say the OD2. I feel people need to approach this model very simply. Don't mess with extended parameters, basically don't try and redesign it. Use a reliable Celestion based cabinet model. I have a fantastic 4x12 with 2 old greenbacks and two old v30s that is the best cab I've played the real amp through. In actual levels of gain with the two adjustable gain controls, the amp has a maximum gain level very similar to the Triptik, the setting of these two controls with respect to each other is critical." [https://forum.fractalaudio.com/posts/1049367]
# "Real world, it has the same amount of actual gain as the Triptik. Way more than most people would need for recording or live playing. Input gain on 10 o clock, gain on 2 o clock is a 70s /80s lead tone, put the input level up to 2 o click and it's a very sustained lead tone or a very modern heavy rhythm tone." [https://forum.fractalaudio.com/posts/1049530]
# "You don't need to crank the real amp to get a ton of overdrive. I actually designed the original for myself and I play in a rock cover band. There's nowhere I would ever be able to get the amp to the point of pushing the power tubes in to overdrive. You gain stage a design based on its application. For a design that needs a lot of overdrive at a low volume, you do most of that and the harmonic makeup in the preamp. The Tucana falls in to this category. The master volumes in a 500 seat club rarely get above 10 O Clock on the real amp and at that point there's still tons of clean headroom left. Of course the power amp adds to the harmonic content, but it adds very little overdrive. Another interesting point to note is that the Tucana has a high pass filter in the power amp feedback loop, which gives you a nice tight low end because the bass is subjected to more gain. For an amp designed to be pushed hard in to power tube overdrive, this should be omitted as all bets are off in the feedback loop when you hit the rails. In other words that filter requires headroom to function properly, as does the presence control of any amp where it's a component of the feedback loop." [https://forum.fractalaudio.com/posts/1050147]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-ca-tucana-carol-ann-tucana-3.112349/ Yek's write-up]

==CAROL-ANN TUCANA LEAD==

==CITRUS A30 CLEAN (Orange AD30HTC)==

[[File:ad30.jpg|300px]]

Models:
* Clean channel
* Dirty channel

[[Cabinet models list |Cab:]] Orange 2x12 (V30)

Gain, Master, Bass, Middle, Treble

Power tubes: EL84

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-citrus-a30-orange-ad30htc.112584 Yek's write-up]

==CITRUS A30 DIRTY==

==CITRUS BASS 200 (Orange AD200B bass amp)==

[[file:orangebass.jpg|300px]]

Model:
* Single channel

[[Cabinet models list |Cab:]] Orange bass cab

Volume, Gain, Bass, Middle, Treble

Power tubes: 6550

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-citrus-bass-200-orange-ad200b.112631/ Yek's write-up]

==CITRUS RV50 (Orange Rockerverb 50 MK II)==

[[File:rockerverb50.jpg|300px]]

Model:
* Dirty channel

[[Cabinet models list | Cab:]] Orange 4x12 (V30)

Dirty channel: Volume, Gain, Treble, Middle, Bass, Reverb (not modeled)

Power tubes: EL34

# "The model is based on a MKII." [https://forum.fractalaudio.com/posts/1109941]
# "The power amp in a Rockerverb has very little negative feedback so it will boost the highs more than most power amps." [https://forum.fractalaudio.com/threads/sorting-out-the-high-end.117233/#post-1398890]
# "It's not a super high gain amp. It's called a Rockerverb not a Metalverb. It's only got four gain stages and there's significant padding between stages." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-12-cygnus-firmware-public-release-candidate.172027/post-2077006]
# (Gain) "It's a ganged pot so it behaves strangely." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-16-01-beta-1-public-beta.172736/post-2088693]
# "That amp doesn't have a high cut." [https://forum.fractalaudio.com/threads/hi-cut-control-on-citrus-rv50-not-working.178740/post-2178756]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-citrus-rv50-orange-rockerverb-50-mk-ii.112668/ Yek's write-up]

==CITRUS TERRIER (Orange Tiny Terror)==

[[File:tinyterror.jpg|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Orange 1x12 or 2x12 (G12H)

Volume, Gain, Tone (High Cut), 7w/15w switch (not modeled)

Power tubes: EL84

# "The actual amp has no tone stack and a single tone control. The tone control is actually a high cut control in the power amp and is therefore replicated by the Hi Cut parameter."
# "It's inaudible when clean." [https://forum.fractalaudio.com/posts/1063208]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-citrus-terrier-orange-tiny-terror.112702/ Yek's write-up]

==CLASS-A 15W TB (Vox AC15 Top Boost)==

[[file:ac15.jpg|300px]]

Model:
* Top Boost channel

[[Cabinet models list | Cab:]] Vox 1x12 (G12M, Alnico)

Volume, Cut, Bass, Treble

Power tubes: EL84

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-class-a-15w-tb-vox-ac-15.112743/ Yek's write-up]

==CLASS-A 30W (Vox AC30 Hand-Wired)==

[[file:ac30.jpg|300px]]

Models:
* AC-30: Normal channel of AC30HW
* AC-30 Bright: Normal channel, Brilliance input
* AC-30 Hot: Top Boost channel of AC30HW, in "Hot" mode (no Bass / Treble)
* AC-30 TB: Top Boost channel of AC30HW, in "Cool" mode

[[Cabinet models list | Cab:]] Vox 2x12 (Alnico, G12M)

Volume, Bright switch (Normal channel), Treble/Bass (Top Boost channel), Hot/Cool switch (Top Boost channel), Tone Cut, Master

Power tubes: EL84

# "Note that the particular AC-30 used for the model has this scratchy high end. (...) It's a hand-wired version and that can lead to this type of sound as the parasitics cause boosting of the very high frequencies when the amp is driven hard." [https://forum.fractalaudio.com/posts/970333]
# "I intentionally limited the midrange notch since, IMO, it's a design flaw in that tone stack. But you can recover that behavior by setting the Mid control fully CCW. Modern AC30's don't have this flaw. They use a Fender-style tone stack with a fixed mid resistor."
# "The bright cap value is normalized to a Drive pot of 1M. An AC30 has a 500K pot so the value will read out as half the actual value. IOW, it's displaying 60 pF which is equivalent to 120 pF." [https://forum.fractalaudio.com/posts/1064264]
# "The Hot model models the AC-30HW model set to Hot. This bypasses the EQ for more gain. For authenticity, leave all tone controls at noon."
# "AC30's have no negative feedback on the power amp. This means the output voltage follows the speaker impedance. Therefore you get a boost at the low frequency resonance of the speaker which causes the low end to get loose when you crank it." [http://forum.fractalaudio.com/threads/crunchy-ac-30-tb-need-some-help-tightening-up-the-low-end.117675/#post-1404022]
# "AC-30's have a poorly designed cathode follower. The bias point is totally wrong and crushes one side of the signal considerably. IMO either the cathode resistor should be 100K or the plate resistor of the preceding stage should be higher, 200K. The clipping is extremely asymmetric. Too much IMO. A little asymmetry is good because it warms things up. Too much causes excessive even-order harmonics which makes things fuzzy and indistinct. The clipping is so asymmetric on an AC-30 that it's almost a half-wave rectifier. You can tweak this by adjusting the Preamp Bias point and/or lowering the Cathode Follower Compression. Or you can lower the Harmonics value which reduces the asymmetric distortion. The downside of that is that it then overdrives the phase inverter causing blocking distortion from excessive bias excursion. Another thing to try is to increase the Grid Clipping value which will add a little headroom. Start with the Bias point. AC-30's are very sensitive to the tube type and part tolerances. A tiny change in the bias point can make a big difference. The default bias point is based on Mullard ECC83 tubes. I prefer the AC-20 because it doesn't have a cathode follower so doesn't suffer from these problems. The cathode follower in an AC-30 doesn't even do all that much. Normally you use a cathode follower to preset a low-impedance source to the tone stack but the tone stack in an AC-30 doesn't present that great of a load anyways." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-02.148983/page-11#post-1767187]
# "The reference AC30 is an AC30HWHD." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-07.150305/page-6#post-1788283]
# "Our Vox models are based on a fairly new AC30HWHD head. The model matches that particular amp very well. Will it match an AC30 from a different era exactly? Probably not." [https://forum.fractalaudio.com/threads/how-accurate-is-fractals-amp-modeling.168786/post-2027668]
# "The normal channel on a Vox would be closest to the Morgan. The Brilliant channel is a "Top Boost" which means it has a tone stack and a significant midrange cut. The normal channel has no tone stack. You can't compare a a Morgan AC20 to the Brilliant channel of an AC30 and declare that one sounds better than the other. Totally different preamps and, therefore, different sound. Personally I think the AC20 is a better amp. Better made, better quality components, much better transformers. If you want that chimey AC30 sound you put an EQ before it and suck out some mids." [https://forum.fractalaudio.com/threads/how-accurate-is-fractals-amp-modeling.168786/post-2064189]
# "So-called Class-A amps (like the AC30) don't actually exhibit much power supply sag because, well, they're Class-A (or nearly). The tubes are biased hot so when one tube is conducting more the other is conducting less and the net supply current doesn't change much. Contrast this with Class-AB where when one tube conducts the other goes into cutoff causing a net increase in supply current and concomitant supply sag. What Class-A amps do exhibit is "cathode squish". The capacitor on the cathodes charges up and shifts the bias point. This reduces the gain and acts as a sort of compressor. It's a unique compression and the amp "opens up" at the same time and crossover distortion increases." [https://www.thegearpage.net/board/index.php?threads/does-this-sound-like-an-ac30-to-you.2325505/post-34009664]
# "An AC-30 has no negative feedback which is why it sounds the way it does." [https://forum.fractalaudio.com/threads/help-me-dial-in-the-ac30.192021/post-2387421]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-class-a-30w-vox-ac-30.112787/ Yek's write-up]

==CLASS-A 30W BRIGHT==

==CLASS-A 30W HOT==

==CLASS-A 30W TB==

==COMET 60 (Komet 60)==

[[file:komet60.jpg‎‎|300px]]

Model:
* Single channel

Volume, Treble, Middle, Bass, Presence, Hi Cut, Touch Response switch: Fast/Gradual (not modeled)

Power tubes: EL34

# "The Komet is definitely a unique amp. Sort of like a Fender preamp into a Marshall power amp. Unique tone stack." [https://forum.fractalaudio.com/threads/new-amps-in-10-06.70362/#post-863547]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-comet-60-komet-60.112823/ Yek's write-up]

==COMET CONCOURSE (Komet Concorde)==

[[file:kometconcorde.jpg‎‎|300px]]

Model:
* Single channel

Volume, Treble, Middle, Bass, Presence, Hi Cut, Touch Response switch: Fast/Gradual (not modeled)

Power tubes: EL34

# "The Komet is definitely a unique amp. Sort of like a Fender preamp into a Marshall power amp. Unique tone stack." [https://forum.fractalaudio.com/threads/new-amps-in-10-06.70362/#post-863547]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-comet-concourse-komet-concorde.112872/ Yek's write-up]

==CORNFED M50 (Cornford MK50 II)==

[[file:cornford.png|300px]]

Formerly: CORNCOB

Model:
* Overdrive channel

[[Cabinet models list |Cab:]] Cornford 4x12 (V30)

Gain, Overdrive, Bass, Middle (500Hz), Treble, Master, Presence, Resonance

Power tubes: EL34

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-corncob-m50-cornford-mk50-ii.112922/ Yek's write-up]

==DAS METALL (Diezel VH4 schematics)==

[[File:vh4.jpg|300px]]

Notes: see Dizzy V4

Power tubes: 6L6

==DELUXE TWEED (1957 Fender narrow-panel Tweed Deluxe, 5E3)==

[[file:deluxe.jpg|300px]]

Models:
* Bright input
* Bright and Normal inputs jumpered

[[Cabinet models list |Cab:]] Fender 1x12 (P12R, C12N, Alnico)

Volume Normal, Volume Bright, Tone

Power tubes: 6V6

# "Deluxe Tweed” amp model based on a Fender 5E3 Deluxe. Note that this amp only has a single tone control. This is modeled by the Treble control in the Axe-Fx II. The Bass and Mid controls are functional and recreate the amp when set to noon. Also note that this amp suffers from extreme blocking distortion at or near maximum gain. This is common in very old designs. As it is virtually unplayable like this, the model uses a somewhat reduced level of grid conduction to lower the amount of blocking distortion and make the amp more playable at high Drive settings."
# "The G3 version of the 5E3 Deluxe Tweed model is a hoot. Totally unpredictable, nasty, gnarly and raunchy. I couldn't stop playing it yesterday. Just like the real amp you have to be careful with your volume control and how you approach the amp so that you keep it right on the edge of playability. So cool." [https://forum.fractalaudio.com/posts/1144722]
# "The Deluxe Tweed amp model is a 5E3. The 1x12 Deluxe Tweed Mix cab is the IR." [http://forum.fractalaudio.com/threads/59-deluxe.106336/page-2#post-1272464]
# "Yup, that's the key. Crank the treble almost all the way up." [http://forum.fractalaudio.com/threads/59-deluxe.106336/page-3#post-1273603]
# "The actual amp has no grid stopper resistor on the second stage and therefore has LOTS of blocking distortion." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-00-beta-3.148907/page-3#post-1764588]
# "IMO the designs are poor because... wait for it... they exhibit a papery buzz. The problem with most cathode biased Class A amps is, 1: they aren't really Class A (more like hot Class AB) and 2: They go into Class B operation when they are overdriven. The cathode capacitor charges up and the bias point shifts dramatically. This causes lots of crossover distortion (papery buzz). It's worse on lower notes because lower notes have more energy and charge the cap more. The is probably the reason Leo Fender switched to fixed bias amps with negative feedback. Fixed bias is just that, the bias point is fixed so the amp doesn't shift into Class B operation when overdriven (not as much anyways, depends on the bias circuit, grid stoppers, etc.). Negative feedback linearizes the amp and reduces the crossover distortion (at the expense of gain). That's why the buzzing went away when you increased negative feedback. Crossover distortion is a unique sound. For cleaner sounds it tends to be objectionable. For overdriven sounds some find it desirable. EVH ostensibly liked his amps biased cold to get some crossover distortion. There are even some amps that have circuits to intentionally generate crossover distortion. Some distortion pedals also do this. Lowering the Cathode Resistance reduces the crossover distortion as it keeps the amp in Class A operation longer but the tubes run hotter and don't last as long. This is not a problem with our virtual amps though. I forget the actual values but I'm pretty certain if you look at the Cathode Resistance value for those amps it's pretty high. This means the amps are biased somewhat cold to begin with and shift to very cold as soon as overdriven." [https://forum.fractalaudio.com/threads/papery-buzz-under-some-models.149193/page-2#post-1772639]
# (about fuzzy lows) "That's what those amps do. Always been that way. Just to be sure I just compared the Deluxe Verb model with the reference amp and it's correct. Those are old designs. Simple circuits with minimal frequency shaping. As such there's a lot of bass going into the power amp. That coupled with the resonance magnification of the speaker impedance causes frequencies around the resonance (in the 50-100 Hz region) to distort early. The low E string is 82 Hz so it's right in that zone." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1842156]
# "When you dime the controls and whack a big chord the sound "goes away" a bit just like the real amp and then comes back a bit later." [https://forum.fractalaudio.com/threads/you-guys-gals-are-in-for-another-treat.169535/post-2042185]
# ("Cygnus" amp modeling) "The 5E3 model is now "jumped" so it has both Normal and Bright drives. You can get all sorts of different distortion textures by playing with the two drives in conjunction with the tone control. As with the real amp everything now interacts. One of the beta testers was remarking that his 5E3 clone sounded more "choked" in comparison to the model. I said "I bet your clone has the wrong type of tube in V1. It's supposed to be a 12AY7 but many clones have a 12AX7A in V1." He checked and, sure enough, 12AX7A in V1." [https://forum.fractalaudio.com/threads/cygnus-beta-first-impressions.169942/post-2045461]
# ("Cygnus" amp modeling) "I've added a non-jumped version of the 5E3 with both volume knobs. Now we can wait for the inevitable "When I turn the Bright Drive all the way down the Normal Drive doesn't do anything" comments." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2051108]
# "Amp doesn't have a bright cap." [https://forum.fractalaudio.com/threads/deluxe-tweed-bright-switch.173082/post-2094005]
# "Some of the undesirable characteristics are what makes a particular amp unique. For example a Deluxe 5E3 is characterized by significant blocking distortion. Without that it doesn't sound like a Deluxe and you can't do the Neil Young thing." [https://www.thegearpage.net/board/index.php?threads/is-digital-getting-too-real.2275913/post-32977457]
# " If you plug into a real Deluxe the "unused" control effects the sound." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-17-00.177099/post-2159734]
# "I finished the 57 Tweed Deluxe today and it's glorious. Clean to "Cinammon Girl" with the volume knob. I never appreciated that amp until I spent some serious time with it." [https://forum.fractalaudio.com/threads/you-guys-gals-are-in-for-another-treat.169535/post-2042068]
# ("Cygnus" amp modeling) "The Bassman and Deluxe Tweed models are both modeled using a 12AY7 as the input buffer. The Preamp Tube Type parameter only affects the tubes after the input buffer." [https://forum.fractalaudio.com/threads/12ay7-preamp-tube-for-tweed-deluxe-and-bassman-models.175834/post-2135435]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-deluxe-tweed-fender-deluxe-5e3.113007/ Yek's write-up]

==DELUXE TWEED JUMPED==

==DELUXE VERB NORMAL (1965 Blackface Fender Deluxe Reverb, AB763)==

[[file:deluxereverb.jpg|300px]]

Models:
* Normal channel
* Vibrato channel

[[Cabinet models list |Cab:]] Fender 1x12 or 2x10 with a Jensen ceramic C12Q, or EVM 12L, or JBL D120, or a Fender 2x10 with a ceramic C10N or C10Q or a 25W Alnico P10R

Volume, Bass, Treble, Reverb, Vibrato (not modeled)

Power tubes: 6V6

# "A DR is numbered 1-10 so 3 on a DR is around 2.2 on the Axe-Fx. The model is based on the Vibrato input #1 which has more gain than the normal input. To simulate plugging into the #2 jack (which has half the gain) set Input Trim to 0.5." [https://forum.fractalaudio.com/posts/1260148]
# "We got our reference Deluxe Reverb out of storage today, hooked it up and measured and compared. Gain measures spot-on and A/B testing sounds identical. With a Suhr Modern guitar with stock pickups both the amp and the model were starting to break up around 3 (which equals 2.2 on the Axe-Fx since the knobs start at zero not one). A Deluxe Reverb breaks up easily since it has 6V6 power tubes. The preamp is virtually identical to a Twin Reverb but 6V6s break up earlier than 6L6s. For a given voltage into the power amp a 6V6 has about 70% of the headroom compared to a 6L6." [https://forum.fractalaudio.com/posts/1262483]
# "The values for the Deluxe Reverb model are based on measurements of an actual 65 Deluxe Reverb, not some hypothetical values on some spec sheet." [http://forum.fractalaudio.com/threads/speaker-page-does-any-of-this-make-sense.110373/#post-1322466]
# (fuzzy lows) "That's what those amps do. Always been that way. Just to be sure I just compared the Deluxe Verb model with the reference amp and it's correct. Those are old designs. Simple circuits with minimal frequency shaping. As such there's a lot of bass going into the power amp. That coupled with the resonance magnification of the speaker impedance causes frequencies around the resonance (in the 50-100 Hz region) to distort early. The low E string is 82 Hz so it's right in that zone." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1842156]
# "We have two Deluxe Reverbs, a vintage 1965 Deluxe Reverb that the model is based on and a Reissue. The vintage one sounds great, the reissue doesn't quite sound as good. It's biased too cold. The comparison was between the model and the Reissue because the vintage amp is worth a small fortune and I only use that when actually working on models. It stays in climate controlled storage otherwise." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1842188]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-deluxe-verb-65-fender-deluxe-reverb-ab763.113046/ Yek's write-up]

==DELUXE VERB VIBRATO==

==DIAMANTE FIRE (22W Diamond Del Fuego)==

[[File:Diamante.jpg|300px]]

22W Class-A amplifier with two channels, designed by Roy Blankenship, based on a '60s Class-A 18W Marshall.

Model:
* channel xx with or without tremolo

Fractal Audio:
# "Nasty little thing." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-20-01-public-beta-2-beta-5.184958/post-2280269]
# "Yeah, it's a cool little amp. It's got some different component values than the Leeds which gives a different vibe." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-20-01-public-beta-2-beta-5.184958/post-2280439]

[[Cabinet models list |Cab:]] single GH12H, V30

Tremolo controls, Volume, Tone

Power tubes: EL84

[https://kitarablogi.com/2011/12/10/review-diamond-del-fuego-english-summary/ Review and sound clips]

[https://www.youtube.com/watch?v=Sn_evdKRhgQ Amp factory tour]

[http://www.diamondamplification.com Diamond Amplification]

==DIRTY SHIRLEY (40W Friedman Dirty Shirley)==

[[File:dirtyshirley.jpg|300px]]

Models:
* Current version of the amp
* Earlier version of the amp with different component values, a little more aggressive than the regular model

[[Cabinet models list |Cab:]] Friedman 4x12 (V30, G12M, G12-65, G12H)

Gain, Master, Bass, Middle, Treble, Presence

Power tubes: 5881

# "If you want more clarity in the low mids (...) reduce Negative Feedback. Friedman's designs are a bit odd in that he takes the feedback off the speaker jack rather than off a transformer tap. (...) The amp will sound tighter and clearer in the low mids." [http://forum.fractalaudio.com/threads/underrated-amp-models.109894/page-2#post-1316362]
# "The design is weird as the negative feedback is taken off the speaker jack. So if you use a 16-ohm speaker you get more feedback (and much more bass) than if you use an 8-ohm speaker. (...) It's too much bass for me so I turn down the Depth and reduce Negative Feedback a bit." [http://forum.fractalaudio.com/threads/question-about-the-friedman-amp-presets.110511/#post-1322655]
# "At first I didn't like it but for some genres it works. The old version (new model) has a 2.2 nF cap on the cathode follower while the newer version has 4.7 nF. The larger cap smooths out the distortion. The cathode bypass cap values are different as well which changes the midrange response." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-00-public-beta-2.124097/page-18#post-1477587 ]
# "Some amps have a fixed depth circuit, e.g. 5153, Freidman BE/HBE, Dirty Shirley, TripTik, Tucana, et. al. In these cases the Depth knob will default to a value that corresponds to the fixed circuit." [https://forum.fractalaudio.com/threads/lets-talk-about-the-depth-control.88747/#post-1071598]
# "I always lower the negative feedback. Friedman amps are a bit strange because the negative feedback is taken off the speaker jack instead of one of the transformer taps. The matching cabs are 16 ohms but if you use an 8-ohm cab you'll get 30% less feedback." [http://forum.fractalaudio.com/threads/couple-of-observations-about-the-friedmans-in-7-02.126030/page-2#post-1504343]
# ("Cygnus" amp modeling) "Dirty Shirley 1 is actually the latest version of the amp." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2048948]
# "They are very dark amp when used with the matching 16-ohm cabinet. The feedback is off the speaker jack (don't ask me why, doesn't make sense). This results in a lot of negative feedback at high frequencies which makes the sound dark. The amp is modeled assuming a 16-ohm load. If you use them into an 8-ohm cabinet they're brighter. To simulate this lower the negative feedback by 1/sqrt(2). This results in a negative feedback value of 3." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2052720]
# "Dirty Shirley 2 is the brighter of the two (has a 2.2nF cathode cap instead of 4.7nF)." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2052814]
# "They are dark amps." [https://forum.fractalaudio.com/threads/cygnus-dirty-shirley-dark.173450/post-2100020]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-dirty-shirley-friedman-dirty-shirley.113088/ Yek's write-up]

==DIRTY SHIRLEY 2==

[[File:dirtyshirley.jpg|300px]]

==DIV/13 CJ (Divided By 13 CJ 11)==

[[File:cj11.jpg‎|300px]]

Models:
* Mid Gain Boost OFF
* Mid Gain Boost ON

[[Cabinet models list |Cab:]] Divided by 13 (G12M)

Volume (pull: midgain boost), Treble, Bass, Master

Power tubes: 6V6

# "It is a bassy amp. Works best with single coils." [http://forum.fractalaudio.com/threads/13-goodness-st-michael-blues.56060/#post-706664]
# "You increase the LOW CUT FREQ to reduce the fuzziness on bass notes but then it won't sound like the real thing." [https://forum.fractalaudio.com/posts/724268]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-div-13-cj11-divided-by-13-cj-11.113126/ Yek's write-up]

==DIV/13 CJ BOOST==

==DIV/13 FT37 HIGH (Divided By 13 FTR 37)==

[[File:ftr37.jpg‎|300px]]

Models:
* Low: channel 1, Mid Gain Boost OFF
* High: channel 1, Mid Gain Boost ON

[[Cabinet models list |Cab:]] Divided by 13 (G12H and Alnico)

Volume (pull: Boost), Treble, Bass

Power tubes: 6V6

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-div-13-ft37-divided-by-13-ftr-37.113127/ Yek's write-up]

==DIV/13 FT37 LOW==

==DIZZY V4 BLUE 2 (Diezel VH4)==

[[File:vh4blue.jpg|300px]]

Models:
* Blue faceplate, channel 2 Crunch
* Blue faceplate, channel 3 Mega
* Blue faceplate, channel 4 Lead
* Silver faceplate, channel 2 Crunch
* Silver faceplate, channel 3 Mega
* Silver faceplate, channel 4 Lead

[[Cabinet models list |Cab:]] Diezel 4x12 (V30, G12-100)

Power tubes: KT77

Gain, Volume, Bass, Mid, Treble, Presence (4kHz), Deep (80Hz), Bright switch (not on channels 3 and 4)

# "The reason Diezels compress so much is due to the cathode follower design. You can reduce the compression in the models by lowering the Compression parameter in the Cathode Follower section." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-14-00.165157/post-1981183]
# "The bright switch on channel 2 in the Silver version is not a conventional bright switch. It switches in a treble peaker later in the circuit. The model models the amp with the bright switch on." [https://forum.fractalaudio.com/threads/cygnus-dizzy-amps-bug.173361/post-2102309]
# "Humans perceive high frequency thermal noise as hiss. The more gain the more hiss. Diezel's have a lot of filtering. Large grid stoppers, plate capacitors, etc. This reduces the bandwidth which lowers the hiss. Camerons are pretty much wide open. Small grid stoppers or bypass caps on the grid stoppers, no plate caps, etc." [https://forum.fractalaudio.com/threads/why-lower-gain-cameron-ccv-amp-model-feels-more-noisy-than-much-higher-gain-herbie-3.188658/post-2339783]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-das-metall-and-dizzy-v4-diezel-vh4.112971/ Yek's write-up]

==DIZZY V4 BLUE 3==

==DIZZY V4 BLUE 4==

==DIZZY V4 SILVER 2==

[[File:vh4.jpg|300px]]

==DIZZY V4 SILVER 3==

==DIZZY V4 SILVER 4==

==DOUBLE VERB NORMAL (1966 blackface Fender Twin Reverb)==

[[file:twin.jpg|300px]]

Models:
* Normal: based on 1966 blackface Fender Twin Reverb, tuned by Andy Fuchs, AB763 circuit, Normal channel
* Vibrato: based on the Vibrato channel of the same amp
* Silverface: based on the Vibrato channel of a 1971 100 watts “Silverface”

[[Cabinet models list |Cab:]] Fender 2x12 with original speakers, DynaCab available

Volume, Bass, Middle, Treble, Bright switch, Reverb (not modeled), Vibrato (not modeled)

Power tubes: 6L6

# (make the Twin cleaner) "Reduce MV (or MV Trim). The biggest reason Silverface Twins were cleaner is because the PI had less gain. Reducing the MV or MV Trim will simulate the lower gain." [https://forum.fractalaudio.com/posts/910015]
# (original Double Verb model) "The Twin Reverb that the model is based on breaks up like that. The model is MIMIC'd and is extremely accurate. It's a Blackface Twin which breaks up easy compared to later Twins. Furthermore, as with all models, it is modeled on the "Hi" input. If you don't want it to break up as easy turn Input Trim to 0.5 to simulate using the "Low" input, reduce Input Drive and MV as necessary. You may want to turn the Bright Switch off as well. People who want squeaky clean usually turn the Bright Switch off on these amps. However, you'd be surprised that a Twin isn't nearly as clean as you think. It's just so damn loud that you get the sensation that it's clean because a light touch on the strings creates a lot of volume." [https://forum.fractalaudio.com/posts/968763]
# "The model is extremely accurate and is based on a 1966 Blackface Twin Reverb. Part of the reason the Blackface era are so sought after is because they distort. They are NOT clean amps by any stretch." [http://forum.fractalaudio.com/threads/twin-issue.119594/#post-1422765]
# "A Dual Showman with the AB763 circuit has one less gain stage than a Twin Reverb so it will have less gain. There are two gain stages. The Vibrato channel of an AB763 Twin Reverb has three gain stages. An AA769 Dual Showman Reverb on the Vibrato channel will have similar gain as it has three gain stages. The circuit number, i.e. AB763, does not mean that the circuits are identical. It refers to the circa of the design. An AB763 Dual Showman is not the same circuit as an AB763 Twin Reverb." [http://forum.fractalaudio.com/threads/twin-issue.119594/page-2#post-1423069]
# "The Super Reverb is really just a 50W version of a Twin Reverb with different speakers." [https://forum.fractalaudio.com/threads/wanted-amps-to-model.56753/page-4#post-713267]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-double-verb-fender-twin-reverb.113177 Yek's write-up]

==DOUBLE VERB SILVERFACE (1971 silverface Fender Twin Reverb)==

==DOUBLE VERB VIBRATO (1966 blackface Fender Twin Reverb)==

==DWEEZIL'S BASSGUY (Dweezil Zappa's 1965 blackface Fender Bassman, AB165)==

[[file:ab165.png|300px]]

Model:
* 1965 Bassman Bass channel modded by Blankenship

[[Cabinet models list |Cab:]] Fender 2x12 (Oxford)

Volume, Negative Feedback, fixed Presence circuit (Presence should be at 10)

Notes: see 65 Bassguy

Power tubes: 6L6

# "It's Dweezil's Blankenship modified Bassman. Dweezil's Bassman has two channels like a regular Bassman. The Normal channel is "normal" and corresponds to the 65 Bassguy Nrml model. The Bass Instrument channel is modified and that's the basis for the new model (Dweezil's B-man). It has a boatload of gain and sounds more like a Plexi than a Fender." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-3-00-public-beta.113410/page-5#post-1356686]
# "Just finished matching this modded 65 Bassman that Dweezil sent me. It's a crazy sounding amp, sounds nothing like your typical Fender. It was modded by Roy Blankenship." [https://forum.fractalaudio.com/threads/another-v10-preview.62489]
# "The 65 Bassguy was matched to a 65 Bassman that Dweezil sent me. It's a vicious amp that sounds more like a Plexi than a Fender. It's the infamous AB165 circuit which is very crunchy and bright and does not sound like your typical Fender." [https://forum.fractalaudio.com/threads/am-i-the-only-one-who-noticed-that-some-amps-have-alot-more-gain.51123/page-2#post-658833]
# "The actual amp has no tone stack so for maximum authenticity all tone controls would be at noon (but don't be afraid to tweak them). In the actual amp the Treble control is re-purposed as a Negative Feedback control. Experiment with different values of Negative Feedback. Lower values are looser." [http://forum.fractalaudio.com/threads/help-with-trying-out-a-new-amp-block-dweezils-b-man.114154/#post-1365573]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-65-bassguy-65-blackface-fender-bassman-ab165.111298/ Yek's write-up]

==ENERGYBALL (Engl Powerball)==

[[File:powerball.jpg|300px]]

Model:
* Lead channel

[[Cabinet models list |Cab:]] Engl 4x12 (V30, V60)

Lead channel: Gain, Lo/Hi Lead switch, Bass, Mid-Open, Mid-Focused, Treble, Open / Focused switch (boosts 300-500 Hz) mode

Power tubes: 6L6

# (Cygnus) "The model was completely redone." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-12-cygnus-firmware-public-release-candidate.172027/post-2079284]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-energyball-engl-powerball.113247/ Yek's write-up]

==EURO BLUE (Bogner Ecstasy 20th Anniversary)==

[[File:ecstasy.png|300px]]

Models:
* Blue channel, structure switch: Vintage
* Blue channel, structure switch: Modern
* Red channel, structure switch: Vintage
* Red channel, structure switch: Modern

[[Cabinet models list |Cab:]] Bogner 2x12 or 4x12 (V30)

Gain, Master, Bass, Middle, Treble, Presence, Bright switch, Structure switch (gain reduction), Old/New Style switch (not modeled), Excursion switch, Gain switch, Plexi Mode (not modeled)

Power tubes: EL34 (earlier models were based on the 6L6 version)

# "People think Bogners are dark but they really aren't. The reason they seem that way is the pot tapers. Most people assume knobs should be set somewhere around noon. If you do this on a Bogner it's like turning the treble way down on a Marshall. Close your eyes and adjust the tone controls with your ears. Don't be afraid to turn them way up or way down." [https://forum.fractalaudio.com/posts/1031334]
# "Human nature is to put the knobs near noon. We are reticent to deviate much from noon. Amp designers exploit this and use different tapers to change the sound of their amps WITH THE KNOBS AT NOON. A prime example are Bogner amps. Everyone says "Bogner amps are dark". No they aren't. But he uses a Log10A taper for the treble pot. It's a standard Marshall tone stack. Usually a linear taper pot is used for the treble. The treble knob at 5.0 (noon) on a Bogner is equivalent to the treble knob at 1.0 on a Marshall. People put the knob at 5.0 and go "wow, this amp is dark". No it isn't. If you turned the treble up to 8 or 9 it would sound a lot like a Plexi but humans are reticent to turn the knobs to extremes. Amp designers know this and exploit it to give their amps a "signature sound"." [https://forum.fractalaudio.com/posts/1047275]
# "Our reference amp is a 20th anniversary and N is Bright Off, B1 is 150 pF and B2 is 1000 pF for both channels. The models default to B1. Change the Bright Cap value to 1 nF to emulate B2. Or better yet use your ears to select a value that sounds best." [http://forum.fractalaudio.com/threads/bogner-ecstasy-pre-amp-eq-b1-n-b2.109077/#post-1305047]
# (Class A) "Turn up Power Tube Grid Bias. In real life that is tough on tubes as it makes them run very hot." [https://forum.fractalaudio.com/threads/replicating-the-bogner-ecstasy-class-a-mode.145294/#post-1718463]
# "Bogner's are notoriously "slow" due to the low B+ voltage. Main reason I can't get along with them. You can try increasing the Variac." [https://forum.fractalaudio.com/threads/fast-pick-attack-amp.170370/post-2049711]
# "Most amps use a linear taper for the treble pot. Bogners use a log taper. So when the knob is at noon on a Bogner it's similar to 8 o'clock on most amps." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486/post-2067364]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-euro-bogner-ecstasy.113278/ Yek's write-up]

==EURO BLUE MODERN==

==EURO RED==

==EURO RED MODERN==

==EURO UBER (Bogner Uberschall)==

[[file:uber.png|300px]]

Model:
* High gain channel

[[Cabinet models list | Cab:]] Bogner 4x12 Uberkab (G12-T75 and V30)

Gain, Master, Bass, Middle, Treble, Presence, Depth (only on Twin-Jet Uberschall)

Power tubes: EL34

# "People think Bogners are dark but they really aren't. The reason they seem that way is the pot tapers. Most people assume knobs should be set somewhere around noon. If you do this on a Bogner it's like turning the treble way down on a Marshall. Close your eyes and adjust the tone controls with your ears. Don't be afraid to turn them way up or way down." [https://forum.fractalaudio.com/posts/1031334]
# "Human nature is to put the knobs near noon. We are reticent to deviate much from noon. Amp designers exploit this and use different tapers to change the sound of their amps WITH THE KNOBS AT NOON. A prime example are Bogner amps. Everyone says "Bogner amps are dark". No they aren't. But he uses a Log10A taper for the treble pot. It's a standard Marshall tone stack. Usually a linear taper pot is used for the treble. The treble knob at 5.0 (noon) on a Bogner is equivalent to the treble knob at 1.0 on a Marshall. People put the knob at 5.0 and go "wow, this amp is dark". No it isn't. If you turned the treble up to 8 or 9 it would sound a lot like a Plexi but humans are reticent to turn the knobs to extremes. Amp designers know this and exploit it to give their amps a "signature sound"." [https://forum.fractalaudio.com/posts/1047275]
# "The feedback circuit is responsible for the behavior of the Presence and Depth controls. Certain Bogners and Diezels have a unique type of feedback circuit. There are no new parameters and nothing to do except twist the Presence and Depth knobs to your desired tone. Note that an Uberschall doesn't have a Depth knob. The default Depth value when you select the Euro Uber model is equivalent to the amp's fixed depth circuit." [https://forum.fractalaudio.com/posts/1159760]
# "Bogner's are notoriously "slow" due to the low B+ voltage. Main reason I can't get along with them. You can try increasing the Variac." [https://forum.fractalaudio.com/threads/fast-pick-attack-amp.170370/post-2049711]
# "Most amps use a linear taper for the treble pot. Bogners use a log taper. So when the knob is at noon on a Bogner it's similar to 8 o'clock on most amps." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486/post-2067364]
# "My Uber is a very early one and probably different than later models. It has the feedback of the 4-ohm tap whereas I've heard later versions have the feedback off the 8-ohm tap. To simulate this increase the Negative Feedback." [https://forum.fractalaudio.com/threads/bogner-uberschall-help.185084/post-2282705]
# "That model does the chugga-chugga better than Thomas the Tank Engine." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-00-release-candidate-beta-7.188382/post-2336626]

[https://forum.fractalaudio.com/threads/fractal-audio-amp-models-euro-uber-bogner-uberschall.113311/ Yek's write-up]

==FAS 6160 (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "Based on the PVH 6160 model but more open and less fizzy than the original amp. Also, a virtual choke has replaced the resistor found on the original’s power supply filter. This results in a bouncier feel."
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS BASS (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6550

# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS BROOTALZ (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6550

# "This amp was an accident. I was working on the Savage model and accidentally used the input stage from an SLO100. So it's the front end of an SLO100 with the back end of a Savage. It's probably an SLO100 power amp too but I'd have to check." [https://forum.fractalaudio.com/posts/1020502]
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]
# "Brootalz uses the Engl Savage presence network which reduces negative feedback as the control is turned down causing an increase in volume." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-5-cygnus-firmware-public-beta-2.170901/post-2059273]

[https://forum.fractalaudio.com/posts/1020502/ Yek's write-up]

==FAS BROWN (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: EL34

# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-brown-and-fas-brown.111974/ Yek's write-up]

==FAS BUTTERY (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model. In the original Cygnus release, it was replaced by an authentic Budda Twinmaster model. It returned in firmware 17 for the Axe-Fx III and later, and firmware for the FM3 and FM9.

Power tubes: EL84

# "I did the Buttery model by ear. I listened to some clips of Buddas (Matchbox 20... excellent!) and tweaked the model until I thought it sounded like one. Screwed around a little with the tube bias points until it had the right balance of harmonics and called it a day."
# "It's still the "ear tuned" version. I bought the amp but because it was so popular as-is I didn't dare change it." [https://forum.fractalaudio.com/threads/question-for-cliff-regarding-the-buttery-model.90943/#post-1095174]
# "Buttery is a virtual amp model that was created by ear. There is no physical, real amp that exists upon which it was based. It's like the FAS models. They exist solely in the virtual world. They all still benefit from the Quantum stuff though as they use the same underlying algorithms for the tube modeling. The amp model, regardless of how accurate it is (and it's probably grossly inaccurate as I never compared it to any actual amp) is very popular and that's why it was never matched to any real amp." [http://forum.fractalaudio.com/threads/question-for-cliff-regarding-the-buttery-model.90943/page-2#post-1283301]
# "Yeah, Buttery was a legacy model from the first Axe-Fx." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-12-cygnus-firmware-public-release-candidate.172027/post-2075782]
# "The previous model wasn't based on any real amp. It was a "FAS Original". [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-12-cygnus-firmware-public-release-candidate.172027/post-2076487]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-buttery-budda-twinmaster.112228/ Yek's write-up]

==FAS CLASS-A (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: EL84

# "A “Blackface” preamp into a cathode-biased 6L6 power amp with no negative feedback. This was a happy accident when originally modeling the Carr Rambler in the beta version of this release. Several mistakes were made in the model prior to MIMIC’ing the amp but the model was so well liked that we decided to make it into its own custom amp model."
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[https://forum.fractalaudio.com/posts/1355719/ Yek's write-up]

==FAS CRUNCH (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: EL34

# "Our take on the ultimate British-sounding amp. More dynamic and open than a Plexi, but with more gain."
# "My take on the ultimate Plexi." [https://forum.fractalaudio.com/threads/axe-fx-ii-firmware-9-public-beta.59414/page-22#post-744829]
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS EXPRESS (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Notes: see Wrecker Express

Power tubes: EL34

# "Based on hypothetical modifications to a Trainwreck Express."
# "It has a master volume. That's one of the "mods"." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-11-02-public-beta-5-beta_4.157025/post-1875792]
# (about the Trainwreck Express) "That amp exhibits a lot of blocking distortion (in the phase inverter) due to its design. You can reduce this via either the PI Bias Excursion or Master Bias Excursion parameters. Another option is to use the FAS Express model which puts some resistors between the last triode stage and the PI to reduce the bias excursion." [https://forum.fractalaudio.com/threads/blocking-distortion-found-in-trainwreck-express.182895/post-2247268]

==FAS HOT ROD (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: EL34

# "FAS Hot Rod is my version of what a modded Marshall should be. I find the BE/HBE a little too boomy and scooped. Bogners are too dark. Splawns don't have enough compression. Etc. So it's my take on a hot-rodded Marshall tone." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-1-02-firmware-release.106477/page-4#post-1274103]
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS LEAD 1 (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS LEAD 2 (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: EL34

# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS MODERN (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "This model is my interpretation of the ideal modern metal tone. In the digital realm we are not constrained by the limitations that face tube amp designers so we are free to implement designs that would be nearly impossible with a tube amp. The Axe-Fx II modeling includes a variety of general purpose filters that I can place anywhere in the signal path. So I put some second-order filters in there to tighten up the tone. Implementing second-order filters in a real tube amp is difficult and costly so is rarely seen." [https://forum.fractalaudio.com/posts/715029]
# "It's loosely based on a Recto but with tighter bass." [https://forum.fractalaudio.com/threads/fw-6-0-rectifier-obsevation.51197/#post-658849]
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]
# (about the MESA Rectifier) "Personally I hate the 39K resistor. It biases the stage much too cold for my tastes. It prevents blocking distortion but there are better ways to do it IMO. The FAS Modern model is similar but biases the stage more towards the center." [https://forum.fractalaudio.com/threads/new-amp-models.159097/post-1901438]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS MODERN II (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "This is a tighter version of the popular FAS Modern model with a 5150-style bass boost in the tone stack."
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS MODERN III (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS RHYTHM (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "Combines the best features of the British (Marshall) and USA (Mesa) crunch models."
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS SKULL CRUSHER (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "The nastiest, most brutal amp model to ever escape from the seventh circle."
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

==FAS WRECK (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Notes: see Wrecker Express

Power tubes: EL34

# "Based on the original WRECKER 1 model from the Axe-Fx Ultra."
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]
# "FAS Wreck model is better than any Trainwreck or Wreck-style amp IMO. All the good bits without the bad stuff." [https://forum.fractalaudio.com/threads/brad-paisley-z-wreck-with-blue-and-gold-2x12-cabinet.163617/post-1961880]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FOX ODS (Fuchs Overdrive Supreme 50)==

[[file:fuchs.jpg|300px]]

Models:
* ODS: Deep switch OFF, Pre Amp Bypass ON (no tone controls)
* ODS Deep: Deep switch ON, Pre Amp Bypass ON (no tone controls)

[[Cabinet models list | Cab:]] Fuchs 2x12 (Eminence)

Gain, High (pull: mid boost), Mid (pull: gain boost), Low, Input, Brite switch, Deep switch, Rock/Jazz switch (not modeled), Master, Accent (= Presence)

Power tubes: 6L6

# "Supposedly a Dumble ODS clone but our reference amp has way more gain than our Dumble." [https://forum.fractalaudio.com/posts/1174814]
# "The topology of the Fuchs is pure Dumble. The difference is that there is less padding between stages 2 and 3 (IIRC). So it's a high-gain Dumble. Personally I don't think the Dumble topology lends itself to that much gain but I didn't design the amp. If you like the base Dumble sound but want a little more gain without the fuzziness of a Fuchs try the Carol-Ann models." [https://forum.fractalaudio.com/threads/fuchs-ods-in-cygnus.172291/post-2081523]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fox-ods-fuchs-overdrive-supreme.113514/ Yek's write-up]

==FOX ODS DEEP==

==FRIEDMAN BE 2010 (Friedman BE)==

[[File:BE.jpg|300px]]

Old models (before "Cygnus" amp modeling):

* BE: based on old Marsha model, BE mode
* BE C45: based on Mark Day's BE-100, C45 switch engaged
* BE V1: based on Mark Day's BE-100, voice: right position (less mids)
* BE V2: based on Mark Day's BE-100, voice: left position (more mids)
* HBE: based on old Marsha model, HBE mode
* HBE 2018: based on 2018 BE-100, HBE mode
* HBE 2018 C45: based on 2018 BE-100, HBE mode, C45 switch engaged
* HBE V1: based on Mark Day's BE-100, HBE mode, voice: right position (less mids)
* HBE V2: based on Mark Day's BE-100, HBE mode, voice: left position (more mids)

Current models ("Cygnus" amp modeling):

* BE 2010: based on Friedman BE-100 from 2010 (probably the "Marsha" edition)
* BE C45: based on later BE-100, C45 switch engaged
* BE V1: based on later BE-100, voice in left position
* BE V1 Fat: based on later BE-100, voice in left position, FAT switch engaged
* BE V2: based on later BE-100, voice in middle position (brightest)
* BE V3: based on later BE-100, voice in right position
* HBE 2010: based on Friedman BE-100 from 2010 (probably the "Marsha" edition), HBE mode
* HBE C45: based on later BE-100, C45 switch engaged
* HBE V1: based on later BE-100, voice in left position
* HBE V1 Fat: based on later BE-100, voice in left position, FAT switch engaged
* HBE V2: based on later BE-100, voice in middle position (brightest)
* HBE V3: based on later BE-100, voice in right position

[[Cabinet models list | Cab:]] Friedman 4x12 (V30 and/or G12M)

Gain, Master, Bass, Middle, Treble, Presence, Bright (clean channel only). BE-100 Deluxe: Thump control. Switches: FAT, C45 (treble boost), SAT (model: SAT), 3-position Voice switch (changes the top-end response of the dirty channels)

Power tubes: EL34

# (before Cygnus) "The old model is an original, hand-built "Marsha". It's MUCH darker than Mark's newer BE/HBE. In fact it's so dark and boomy I emailed Dave to make sure the amp was built correctly. Turns out the snubber cap is the wrong value. But even with the snubber cap corrected it's still very dark and boomy which made me question as to whether there are other components that are incorrect. So we decided to redo the model based on Mark's amp which is the amp that was the demo model at Tone Merchants." [http://forum.fractalaudio.com/threads/the-new-hbe.112717/#post-1348497]
# (before Cygnus) "The models are based on two different amps. The V1 and V2 are based on Mark Day's BE100. The other models are based on our original "Marsha". Like most boutique amp makers Friedman's designs have evolved over time with changes to the circuit. The original Marsha we have is dark and bassy with lots of lowpass filtering. The newer amp is brighter and tighter. For now note that V1/V2 refer to the newer amp and represent the position of the Voicing switch." [http://forum.fractalaudio.com/threads/which-are-the-new-be-hbe-models.114510/#post-1369754]
# "The BE/HBE has a fixed depth circuit that gives a lot of bass boost. The model defaults the Depth to match this." [https://forum.fractalaudio.com/posts/833169]
# "If you want more clarity in the low mids from the BE/HBE reduce Negative Feedback. Friedman's designs are a bit odd in that he takes the feedback off the speaker jack rather than off a transformer tap. The mating cab for a BE/HBE is 16 ohms which means lots of feedback. But if you connect the amp to an 8 ohm load there is about 30% less feedback. The amp will sound tighter and clearer in the low mids." [http://forum.fractalaudio.com/threads/underrated-amp-models.109894/page-2#post-1316362]
# "The design is weird as the negative feedback is taken off the speaker jack. So if you use a 16-ohm speaker you get more feedback (and much more bass) than if you use an 8-ohm speaker. The model is based on using the matching cab. It's too much bass for me so I turn down the Depth and reduce Negative Feedback a bit." [http://forum.fractalaudio.com/threads/question-about-the-friedman-amp-presets.110511/#post-1322655]
# "I always lower the negative feedback. Friedman amps are a bit strange because the negative feedback is taken off the speaker jack instead of one of the transformer taps. The matching cabs are 16 ohms but if you use an 8-ohm cab you'll get 30% less feedback." [http://forum.fractalaudio.com/threads/couple-of-observations-about-the-friedmans-in-7-02.126030/page-2#post-1504343]
# "C45 is a treble boost on the input. Put a filter block before the amp as follows: Type: Tilt EQ - Freq: 700 Hz - Gain: 4.5 dB" [http://forum.fractalaudio.com/threads/friedman-hbe-with-c45-switch.110686/#post-1324975]
# [http://forum.fractalaudio.com/threads/friedman-be-100-hbe-channel-vs-the-axe-fx-3-hbe-model.144911 Discussion about the Bass control]
# "Some amps have a fixed depth circuit, e.g. 5153, Freidman BE/HBE, Dirty Shirley, TripTik, Tucana, et. al. In these cases the Depth knob will default to a value that corresponds to the fixed circuit." [https://forum.fractalaudio.com/threads/lets-talk-about-the-depth-control.88747/#post-1071598]
# "When you watch a video Dave himself turns the bass way up. Steve Stevens and Jerry Cantrell turn the bass way up too. If I did that with my guitar it would be a muddy mess. Puzzling to me because the BE has a fixed depth circuit and a significant amount of negative feedback so there is quite a bit of bass boost in the power amp as well." [https://forum.fractalaudio.com/threads/friedman-be-100-hbe-channel-vs-the-axe-fx-3-hbe-model.144911/#post-1714308]
# "The BE has very light power supply filtering like old Plexis." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-14-01.165716/post-1990715]
# (Cygnus) "All the Friedman models are now based on the latest amp. Our reference amp was made in 2018 and has the feedback off the 4-ohm tap." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2047861]
# (Cygnus) "That's the way the HBE channel sounds. The problem with the design is that the drive control is located between the 3rd and 4th gain stages. Too far back IMO. This causes a lot of distortion and also a lot of bias excursion before the drive control with no way to control it. In most amps the drive control is located after the first stage (input buffer). Some amps have a second drive control, typically called an Overdrive, located further downstream which allows you to balance the pre- and post distortion. One way to deal with it is to decrease the Input Trim and increase the Input Drive. You can also try reducing the Master Bias Excursion but that won't get rid of the pre-drive control distortion. A lot of people like this sound though. It has a certain stringy quality that many people find desirable." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-10-cygnus-firmware-public-beta-7.171198/post-2062927]
# (Cygnus) "There are now three "Voicings": V1, V2 and V3 corresponding to the three positions of the Voice switch." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486]
# Based on latest version of amp. There are now three "Voicings": V1, V2 and V3 corresponding to the three positions of the Voice switch." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486/post-2067182]
# "The BE100 design has changed over the years. Dave is constantly fiddling with things. The original "Marsha" (which became the BE100 after the cease-and-desist) had the Gain control after the second stage. Later versions have the gain control after the third stage so even if you turn the gain down you may still get some distortion. There were also numerous changes to component values, feedback tap, etc., etc. Our models are authentic recreations of the two particular versions we have. Whether those versions match your particular version is unknown." [https://forum.fractalaudio.com/threads/friedman-amps-in-axefx3-vs-helix.197851/post-2458958]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-friedman-be-and-hbe-friedman-be-100.113559 Yek's write-up]

==FRIEDMAN BE C45==

==FRIEDMAN BE V1==

==FRIEDMAN BE V1 FAT==

==FRIEDMAN BE V2==

==FRIEDMAN BE V3==

==FRIEDMAN HBE 2010==

==FRIEDMAN HBE C45==

==FRIEDMAN HBE V1==

==FRIEDMAN HBE V1 FAT==

==FRIEDMAN HBE V2==

==FRIEDMAN HBE V3 ==

==FRIEDMAN SMALL BOX (Friedman Smallbox)==

[[File:smallbox.jpg|300px]]

Model:
* Channel 2

[[Cabinet models list |Cab:]] Friedman 2x12 (G12M)

Gain, Master, Bass, Middle, Treble, Presence, Bright switch (channel 1 only, not modeled)

Power tubes: EL34

# "The schematic shows a 2.2 nF coupling cap off the first stage but the actual amp has a 4.7 nF. 2.2 nF would mean less bass. I can only assume the amp was built to the latest specs. If an amp model is "G3'd" it is deadly accurate. I go through the amps and check the values of each component, measure the voltages, compare the frequency response to the model, etc., etc., etc. If the model is too bassy for you then you would find the real amp too bassy, or at least our particular reference model." [http://forum.fractalaudio.com/threads/friedman-sm-box-smallbox.99488/#post-1193341]
# "If you want more clarity in the low mids (...) reduce Negative Feedback. Friedman's designs are a bit odd in that he takes the feedback off the speaker jack rather than off a transformer tap. (...) The amp will sound tighter and clearer in the low mids." [http://forum.fractalaudio.com/threads/underrated-amp-models.109894/page-2#post-1316362]
# "The design is weird as the negative feedback is taken off the speaker jack. So if you use a 16-ohm speaker you get more feedback (and much more bass) than if you use an 8-ohm speaker. (...) It's too much bass for me so I turn down the Depth and reduce Negative Feedback a bit." [http://forum.fractalaudio.com/threads/question-about-the-friedman-amp-presets.110511/#post-1322655]
# "I always lower the negative feedback. Friedman amps are a bit strange because the negative feedback is taken off the speaker jack instead of one of the transformer taps. The matching cabs are 16 ohms but if you use an 8-ohm cab you'll get 30% less feedback." [http://forum.fractalaudio.com/threads/couple-of-observations-about-the-friedmans-in-7-02.126030/page-2#post-1504343]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-friedman-sm-box-friedman-small-box.113604/ Yek's write-up]

==FRYETTE D60 LESS (Fryette Deliverance 60)==

[[file:fryette.jpg|300px]]

Models:
* "Less" mode
* "More" mode

[[Cabinet models list | Cab:]] Fryette 4x12 P50E (Fane F70G)

Gain 1, Gain 2, Master, Bass, Middle, Treble, Presence, Depth, More/Less switch

Power tubes: KT88

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fryette-d60-fryette-deliverance-60.113657/ Yek's write-up]

==FRYETTE D60 MORE==

==GIBTONE SCOUT (Gibson GA17RVT Scout)==

[[file:gibson.jpg‎|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Gibson 1x10

Volume, Tremolo, Reverb (not modeled)

Power tubes: 6AQ5

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-gibtone-scout.113698 Yek's write-up]

==HERBIE CH2+ (Diezel Herbert)==

[[File:herbert.jpg|300px]]

Models:
* Channel 2+ of original Herbert (based on Marshall JC800)
* Channel 2- of original Herbert (based on Marshall Plexi)
* Channel 3 of original Herbert (based on Diezel VH4)
* Channel 2+ of black-panel Herbert MK III

[[Cabinet models list |Cab:]] Diezel 4x12 (V30, G12-K100)

Gain (not on channel 1), Bass, Middle (1 kHz), Treble, Master, Presence (> 3kHz), Deep (120Hz), Mid-Cut (not modeled), Gain Boost switch (not modeled)

Power tubes: KT66

# "The reason Diezels compress so much is due to the cathode follower design. You can reduce the compression in the models by lowering the Compression parameter in the Cathode Follower section." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-14-00.165157/post-1981183]
# (reproducing the Mid Cut function) "Use a Peak EQ filter at 400 Hz with a Q of 1.4. Decrease its Gain until the desired scoop is achieved. Play with the Q to set the width of the scoop." [https://forum.fractalaudio.com/posts/1144887]
# "Humans perceive high frequency thermal noise as hiss. The more gain the more hiss. Diezel's have a lot of filtering. Large grid stoppers, plate capacitors, etc. This reduces the bandwidth which lowers the hiss. Camerons are pretty much wide open. Small grid stoppers or bypass caps on the grid stoppers, no plate caps, etc." [https://forum.fractalaudio.com/threads/why-lower-gain-cameron-ccv-amp-model-feels-more-noisy-than-much-higher-gain-herbie-3.188658/post-2339783]
# (the new Herbert model in firmware 21 for the Axe-Fx III) "I like it a lot more than the old version of the amp. The original Herbert is too dark, fuzzy, compressed and muddy IMO. Sounds great playing alone but when I play along with a recording it just gets lost. The new Herbert is tighter and sits in the mix better." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-00-release-candidate-2-beta-8.188778/post-2340412]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-herbie-diezel-herbert.113745 Yek's write-up]

==HERBIE CH2-==

==HERBIE CH3==

==HERBIE MK3 (Diezel Herbert MKIII)==

==HIPOWER BRILLIANT (Hiwatt DR103)==

[[file:hiwatt.jpg|300px]]

Models:
* Normal channel
* Brilliant channel
* Normal and Brilliant channels jumpered

[[Cabinet models list |Cab:]] Hiwatt 4x12 (Fane)

Volume, Master, Bass, Middle, Treble, Presence

Power tubes: EL34

# "I have a 1974 Hiwatt DR-103. The model is based on that. It is one of the Harry Joyce, Hylight era models. Still has the original tubes. Closet find and sounds glorious." [https://forum.fractalaudio.com/posts/497513]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-hipower-hiwatt-dr103.113789/ Yek's write-up]

==HIPOWER JUMPED==

==HIPOWER NORMAL==

==HOT KITTY (Bad Cat Hot Cat 30)==

[[file:hotcat.jpg|300px]]

Model:
* High gain channel

[[Cabinet models list | Cab:]] BadCat 1x12 (proprietary Celestion)

Gain, Edge (not modeled), Level, Bass, Mid-range switch (not modeled), Treble, Brilliance, Master

Power tubes: EL34

# "Brilliance is their name for Hi-Cut. I set the Edge control to where I thought it sounded best. It essentially does the same thing as the Bright knob though less precise."
# "The amp has a Hi Cut but it's labeled Brilliance. It's wired backwards so turning it CW gets brighter." [http://forum.fractalaudio.com/threads/hotkitty-1-05-is-nasty-as-hell.107651/page-2#post-1289111]
# "Those amps make a lot of IMD. The real amp does the same thing but you wouldn't normally use a subwoofer with one." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-00-public-beta-2.124097/page-14#post-1477200]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-hot-kitty-bad-cat-hot-cat-30.113829/ Yek's write-up]

==JMPRE-1 CLEAN 1 (Marshall JMP-1 preamp)==

[[image:Cliff JMP-1.jpg|300px]]

Models:
* Clean 1
* Clean 1 with Bass Shift engaged
* Clean 2
* Clean 2 with Bass Shift engaged
* OD1 mode
* OD1 mode with Bass Shift engaged
* OD2 mode
* OD2 with Bass Shift engaged

Volume, Gain, Bass, Mid, Treble, Presence (preamp), Bass shift, Depth

Power tubes: EL34

# "The power amp is based on a typical Marshall 100 watts power amp of the same era."
# [before firmware 19.02 for the Axe-Fx III] "The JMP-1 tone controls have more range than the actual preamp. The preamp has about +/- 8 dB for each tone control while the model has the standard +/- 12 dB."
# "Actually a JMP-1 is unique in that the tone controls do not interact. Most guitar amps use a passive "tone stack" where the controls interact. The JMP-1 has a fixed passive tone stack followed by an active 4-band EQ." [https://forum.fractalaudio.com/threads/is-the-brit-pre-good-enough.132950/#post-1573028]
# (Def Leppard) "The amp model you are looking for is "JMPre-1 OD1". Some cabs you might like to try with that amp model: Factory 2 #97 2x12 RECTO V60 57 OH, Factory 2 #995 4x12 UBER V30 57 OFF-AXIS, Factory 2 #530 4x12 BRIT 70s GB 121 I." [https://forum.fractalaudio.com/threads/are-phil-and-viv-using-brit-pre-or-jmpre-1-on-the-iii.139394]
# Firmware 19.02 and later for the Axe-Fx III:
#* Added JMPRE-1 Output EQ type to Amp block. This type replicates the active EQ used in the JMP-1 preamp.
#* Added Clean models.
#* The real amp has a fixed, passive tone stack with an active 4-band EQ. Therefore, the Bass/Mid/Treble controls when using Authentic Tone Controls are mapped to the Graphic EQ. Clean channels only: the passive tone stack itself, however, is adjustable. With all controls at noon the tone stack is equivalent to the real amp’s fixed tone stack. You can access these controls using the Ideal Tone Controls or via Axe-Edit.

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-pre-and-brit-jmpre-1-marshall-jmp-1.112139/ Yek's write-up]

==JMPRE-1 CLEAN 1 BASS SHIFT==

==JMPRE-1 CLEAN 2==

==JMPRE-1 CLEAN 2 BASS SHIFT==

==JMPRE-1 OD1==

==JMPRE-1 OD1 BASS SHIFT==

==JMPRE-1 OD2==

==JMPRE-1 OD2 BASS SHIFT==

==JR BLUES (Fender Blues Junior)==

[[file:bluesjr.jpg|300px]]

Models:
* Fat switch OFF
* Fat switch ON

[[Cabinet models list | Cab:]] Fender 1x12 (Eminence, Jensen C12N, P12R)

Bass, Middle, Treble, Gain, Volume, FAT button (boosts gain and midrange frequencies), Reverb (not modeled)

Power tubes: EL84

# "The Blues Jr. amp has a fixed presence circuit." [https://forum.fractalaudio.com/threads/question-of-proper-axe-eq-values-for-amps-that-dont-have-them.67260/#post-828733]
# "They're actually pretty decent little amps and sound great when cranked." [https://forum.fractalaudio.com/threads/forgot-how-loud-tube-amps-are.170551/post-2052934]
# "The Master Volume in a Blues Jr. is linear taper. This is ridiculous as it makes it very difficult to find the sweet spot. The model uses an audio taper instead which makes finding the sweet spot easier." [https://forum.fractalaudio.com/threads/cygnus-is-absolutely-magnificent.173225/post-2096570]
# "Blues Jr. is a very colored preamp. The best you can do is turn Bass and Treble to zero and Mid all the way up. That will make it somewhat flat but you still have the bright cap on the drive and the bandpass between the preamp and power amp." [https://forum.fractalaudio.com/threads/negative-results-playing-my-fm9-through-a-blues-jr.189057/post-2343390]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-jr-blues-fender-blues-junior.113925/ Yek's write-up]

==JR BLUES FAT==

==JS410 CRUNCH ORANGE (Marshall JVM410HJS)==

[[file:js.jpg|300px]]

Models:
* Crunch Orange: based on a JCM 2203
* Crunch Red: based on a modded JCM 2203
* Lead Green: like the OD1 channel on the original JVM410H
* Lead Orange: more gain
* Lead Red: even more gain

[[Cabinet models list | Cab:]] Marshall 4x12 (V30 and G12H)

Volume, Gain, Bass, Middle, Treble, Master, Presence, Resonance, Gate (not modeled), Mid-Shift (around 650hz off and around 500hz on, not modeled)

Power tubes: EL34

# "Joe said he puts all the tone controls at around 10:00." [http://forum.fractalaudio.com/threads/jvm-js-in-the-tonestack.109946/#post-1316690]
# "The JVM has a huge plate resistor on the cathode follower, the JS does not." [https://forum.fractalaudio.com/threads/jvm-sounding-weird.150157/page-2#post-1785256]
# "The model is based on Joe's personal amp. He sent it to me. When I entered the values from the schematic it didn't match. The tapers of the controls were different and there were some other differences. I can only assume that his personal amp is different than production models. This is often the case as production models are designed to be inexpensive to build (i.e., using control tapers that are used in other models to reduce inventory, etc.). Another possibility is there were changes made during production. It is not uncommon for amps to have changes made to the circuitry over the production run. For example, the Blues Jr. has had numerous revisions. The first ones sound nothing like the later models. This is sometimes done due to perceived customer reaction ("The amp is too dark" or "The amp is too harsh"). Simply adjusting BMT should get you what you want. Control tapers make a big difference. For example, a Bass pot that is a linear taper would need to be set to 1.0 to match a Log10A taper at 5.0." [https://forum.fractalaudio.com/threads/marshall-jvm410hjs-real-amp-versus-axe3.197259/post-2450481]
# Firmware 23: "Updated all JS410 Lead models based on a current production JVM410HJS. The Crunch models were tested and did not require updating."
# (Was there much different between the production Satriani amp and his own one?) "Yes, they measure quite differently." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-23-00-public-beta-1.198479/post-2467475]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-js410-marshall-jvm410hjs.114030/ Yek's write-up]

==JS410 CRUNCH RED==

==JS410 LEAD GREEN==

==JS410 LEAD ORANGE==

==JS410 LEAD RED==

==JAZZ 120 (Roland Jazz Chorus 120)==

[[File:jc120.jpg|300px]]

Model:
* Single model

[[Cabinet models list| Cab:]] Roland 2x12 ("silver" AlNiCo)

Volume, Bass, Mid, Treble, Bright switch. Not modeled: Distortion, Chorus, Reverb

Power tubes: none (solid-state)

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-jazz-120-roland-jazz-chorus-120.113865/ Yek's write-up]

==LEGEND 100 (Carvin Legacy VL100)==

[[file:legacy.jpg|300px]]

Formerley: CALI LEGGY (VL100) and LEGATO 100 (VL300)

Legacy models:
* Legend 100: lead channel of Carvin VL100 Legacy
* Legend 100 II: channel 3 of Carvin VL300 Legacy 3

[[Cabinet models list | Cab:]] Carvin 2x12 or 4x12 (V30)

VL100: Presence, Treble (11kHz), Mid (650Hz), Bass (80Hz), Drive, Volume

VL300: Bass, Middle, Treble, Presence, Drive, Volume, Master, Boost (not modeled), Reverb (not modeled), Gain switch (not modeled)

Power tubes: EL34

# "The thing that makes a Legacy unique is the tone stack. It uses a "James" tone stack which is more like hi-fi tone controls." [https://forum.fractalaudio.com/threads/thank-you-fractal-for-the-leggy-legacy-model-its-great.47586/#post-620139]
# "Adds the "Legato 100" model based on Steve Vai's Legacy 100. This model is unique in that it uses a Baxandall (sometimes called a "James") tone stack. More often used on tube hi-fi gear the controls are less interactive than a typical guitar amp tone stack and impart a different tonal quality." [https://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-4-01-beta.119527/]
# "The Legato 100 is based on a one-of-a-kind version owned by a certain Californian guitar player. It is a very dark amp. Part of this is due to the tapers on the tone pots. With everything at noon the tone stack looks like a highshelf with a good amount of high frequency cut. The tone stack is a Baxandall which is more common in hi-fi gear than guitar amps. It lends a unique character to the tone." [https://forum.fractalaudio.com/posts/1426142]
# "SV's personal settings are: Drive: 7.5, Bass: 6, Mid: 4, Treble: 8, Presence: 8. I had to increase the Mid control on the model to about 5 to match the amp which indicates the mid pot on the amp was greater than spec. This is not unusual. Typical consumer-grade pots have pretty poor tolerance in both end-to-end resistance and resistance at the midpoint." [https://forum.fractalaudio.com/posts/1429558]
# (Cygnus) "Carvin Legacy 100. Legend II is channel 3 from the Legacy 3." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-12-cygnus-firmware-public-release-candidate.172027/post-2075753]
# "What is happening is the power amp is oscillating at that very low frequency cabinet resonance. This occurs because the Legacy has so much negative feedback (12 dB, which is the highest of any amp I've ever modeled). Combined with the smallish output transformer there is a loss of phase margin at low frequencies which causes the power amp to become unstable. The Rumble cab is unique in that it is ported and has two different types of speakers in it. This causes a double resonance and one of the resonances is at a very low frequency. For typical power amps with reasonable amounts of feedback this isn't an issue." [https://forum.fractalaudio.com/threads/bizzare-yet-interesting-legend-amp-model-possible-issue.173492/post-2101586]
# "The tonestack in a Legacy is a James. A Baxandall is active." [https://forum.fractalaudio.com/threads/have-we-reached-the-end-of-new-amp-models-in-the-axe-3.184271/post-2483056]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-cali-leggy-and-legato-100-carvin-legacy-vl100.112449 Yek's write-up]

==LEGEND 100 II (Carvin Legacy VL300)==

==MATCHBOX CHIEFTAIN 1 (Matchless Chieftain)==

[[File:chieftain.jpg|300px]]

Formerly: BOUTIQUE 1 and BOUTIQUE 2

Models:
* Single channel
* Boosted for more gain and high-frequency emphasis

[[Cabinet models list |Cab:]] Matchless 2x12 (G12H)

Volume, Master, Bass, Mid, Treble, Brilliance

Power tubes: EL34

# "The secret of the Chieftain is the split cathode bias. Most "Class-A" amps use a shared cathode bias but the Chieftain uses separate cathode bias networks which results in less bias shift so there's less fizz." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-03.158240/post-1895726]
# "The "Treble" knob on the Chietain model is actually Preamp Presence. It's not part of the tone stack. It's a separate presence network at the output of the last stage. They just call it treble." [https://forum.fractalaudio.com/threads/matchbox-chiefman-factory-preset-treble-knob-modifier-weirdness.173485/post-2100361]
# "The Treble control in a Chieftain is actually a "Preamp Presence" control, similar to the Presence control in a Dual Rectifier in Modern mode. It is separate from the tone stack and located later in the gain stages. The tone stack has no treble control." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-00.189017/post-2344358]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-boutique-matchless-chieftain.111832/ Yek's write-up]

==MATCHBOX CHIEFTAIN 2==

==MATCHBOX D-30 (Matchless DC-30)==

[[File:dc30.jpg|300px]]

Models:
* Channel 1 (12AX7 preamp tubes), Master Volume bypassed
* Channel 2 (EF86 preamp tubes), Master Volume bypassed

[[Cabinet models list | Cab:]] Matchless 2x12 (25w G12M and 30w G12H)

Channel 1: Volume, Bass, Treble, Cut, bypassable Master

Channel 2: Volume, Tone, Cut, bypassable Master

Power tubes: EL84

# "The DC-30 is basically an AC-30 copy. The voltages are a bit different but the topology is nearly identical. However, IMO, it does sound better. Not sure why. Perhaps the better quality components. AC-30's have kind of crappy OTs." [https://forum.fractalaudio.com/posts/968982]
# (channel 2) "The switch selects the coupling capacitor between the EF86 and the volume pot." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-9-00-beta.130981/page-11#post-1552400]
# "Added “Matchbox D-30 EF86” amp model. While the real amp has a six-position Tone switch, the model has a continuously variable tone control. Note that the Tone control is mapped to the Bass control in Ideal mode as the Tone switch is essentially a bass cut control."
# “The new DC-30 model may have dethroned the mighty AC-20 as my favorite "Class A" model.” [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-11-01.156108/post-1858859]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-matchbox-d-30-matchless-dc-30.114129/ Yek's write-up]

==MATCHBOX D-30 EF86==

==MR Z HWY 66 (Dr. Z Route 66)==

[[file:route66.jpg|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Dr. Z 2x12 (V30 and G12H)

Volume, Bass, Treble

Power tubes: KT66

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-mr-z-hwy-66-dr-z-route-66.114166/ Yek's write-up]

==MR Z MZ-38 (Dr. Z Maz 38 SR)==

[[File:maz38.jpg|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Dr. Z 1x12 (G12H)

Volume, Master, Bass, Mid, Treble, Cut, Reverb on some models (not modeled)

Power tubes: EL84

# "Dr. Z is the quintessential country amp." [https://forum.fractalaudio.com/posts/828934]"
# "IMO the designs are poor because... wait for it... they exhibit a papery buzz. The problem with most cathode biased Class A amps is, 1: they aren't really Class A (more like hot Class AB) and 2: They go into Class B operation when they are overdriven. The cathode capacitor charges up and the bias point shifts dramatically. This causes lots of crossover distortion (papery buzz). It's worse on lower notes because lower notes have more energy and charge the cap more. The is probably the reason Leo Fender switched to fixed bias amps with negative feedback. Fixed bias is just that, the bias point is fixed so the amp doesn't shift into Class B operation when overdriven (not as much anyways, depends on the bias circuit, grid stoppers, etc.). Negative feedback linearizes the amp and reduces the crossover distortion (at the expense of gain). That's why the buzzing went away when you increased negative feedback. Crossover distortion is a unique sound. For cleaner sounds it tends to be objectionable. For overdriven sounds some find it desirable. EVH ostensibly liked his amps biased cold to get some crossover distortion. There are even some amps that have circuits to intentionally generate crossover distortion. Some distortion pedals also do this. Lowering the Cathode Resistance reduces the crossover distortion as it keeps the amp in Class A operation longer but the tubes run hotter and don't last as long. This is not a problem with our virtual amps though. I forget the actual values but I'm pretty certain if you look at the Cathode Resistance value for those amps it's pretty high. This means the amps are biased somewhat cold to begin with and shift to very cold as soon as overdriven. Then there's shared vs. split cathode. If you look at the schematics on the web the Maz-38 is shared cathode. I could never get the model to sound exactly like our reference amp. Finally I traced the entire circuit and our particular amp is a split cathode. As soon as I changed the model to split cathode it was spot on. This is not exposed to the user though (there's a hidden shared/split switch). Our particular amp says "Humbucker" inside the chassis. Not sure if the difference in the cathode circuit is because Dr. Z likes split cathode for humbucking guitars or what." [https://forum.fractalaudio.com/threads/papery-buzz-under-some-models.149193/page-2#post-1772639]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-mr-z-mz-8-and-mz-38-dr-z-maz-8-and-maz-38-sr.114213/ Yek's write-up]

==MR Z MZ-8 (Dr. Z Maz 8)==

[[File:maz8.jpg|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Dr.Z 1x12 (G12H)

Volume, Master, Bass, Mid, Treble, Cut, Reverb (not modeled), Pentode/Triode switch (not modeled)

Power tubes: EL84

# "Dr. Z is the quintessential country amp." [https://forum.fractalaudio.com/posts/828934]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-mr-z-mz-8-and-mz-38-dr-z-maz-8-and-maz-38-sr.114213/ Yek's write-up]

==NUCLEAR-TONE (Swart Atomic Space Tone)==

[[file:swart.jpg|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Swart 1x12 (Mojotone BV-25m)

Volume, Tone, Tremolo, Reverb (not modeled)

Power tubes: 6V6

# "It's unique character comes from the PI. It's a cathodyne phase inverter so it doesn't drive the grids as hard." [https://forum.fractalaudio.com/posts/828241]
# "The real amp is known for it's tremolo so that's why we used the bias trem on the preset. Bias trem works by modulating the power tube grid bias. One of the side-effects is that the effect becomes less pronounced as you play harder which makes it basically "auto ducking". Also since it's modulating the bias it gives an almost Univibe like effect since the phase changes a bit too." [http://forum.fractalaudio.com/threads/patch-62-nuclear-tone-weird-tremolo-effect.122258/#post-1454602]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-nuclear-tone-swart-atomic-space-tone.113700/ Yek's write-up]

==ODS-100 CLEAN (Dumble Overdrive Special)==

[[File:dumble.jpg|300px]]

Models:
* Clean: based on HRM circuit, Clean channel
* Ford: based on schematics of Robben Ford's #102 Dumble, Overdrive channel, Pre Amp Boost (PAB) OFF
* Ford PAB: same as Ford model, PAB ON (bypasses the tone controls), Mid switch OFF
* Ford PAB Mid: same as Ford model, PAB ON, Mid switch ON
* HRM: based on HRM circuit, Overdrive channel, Mid switch OFF
* HRM Mid: based on HRM circuit, Overdrive channel, Mid switch ON

[[Cabinet models list | Cab:]] Dumble 2x12 or 4x12 (G12-65, EVM)

Volume (Clean), Bass, Middle, Treble, Overdrive Level, Ratio, Volume (Overdrive), Master, Presence, Bright switch, Mid boost switch, Jazz/Rock switch (not modeled), Pre Amp Boost (PAB)

Power tubes: EL34

# "The ODS100 has two drive controls, one is right at the input, the other is in the lead boost section."
# "I hate to admit it but there is something special about a real Dumble. I don't know what it is but there is something in the voicing. The various clones I have are cool and have their own thing going but they don't sound like the Dumble. Hard amp to play though. Very unforgiving but tremendous clarity." [https://forum.fractalaudio.com/posts/824398]
# "They call HRM "Hot Rubber Monkey" but what it really means is "Hot Rod Marshall"." The HRM Dumbles have a fixed Marshall tone stack at the output of the lead channel. This gives a little scoop to the mids." [https://forum.fractalaudio.com/posts/828279]
# "My Dumble is S/N 0213 IIRC. It's an EL-34 ODS HRM." [https://forum.fractalaudio.com/posts/1170559]
# "The ODS-100 Ford 2 model is not based on the HRM model with the HRM tonestack removed. Whether or not the model matches any particular Dumble is unknown as we have not been able to procure a non-HRM Dumble yet. The model is based on schematics that were given to us that supposedly accurately represent Robben Ford's Dumble. Whether or not the schematics are accurate I do not know. The voltage divider at the output of V1B is set to 0.078 which is based on the values that are indicated on the schematic for the set-point of the trimmer. As no two Dumbles are identical it stands to reason that one person's interpretation of the ideal Dumble voicing may not agree with another's. Since V1 is running clean you can get more gain by simply increasing Input Trim. It will have basically the same effect as increasing the trimmer."
# "A signal divider, which is more correctly called a voltage divider, is calculated by taking the resistance to ground divided by the sum of the resistances. In this case the voltage divider would be 26.7/317 = 0.084. This is very close to the values that we were given (which yield 0.078). Our model also uses local feedback on V1B (which is about 2-3 dB less gain) and accounts for the voltage divider's affect on the AC load line. In fact all stages in a Dumble typically have an AC load-line that's different than the DC load-line due to the load resistance being significant in relation to the plate resistor. Since V1A and V1B run clean (linear) Input Trim will accomplish the same thing as increasing the trimmer into the drive stages. This is because a linear system is commutative (see any introductory Signals and Systems text for properties of linear systems). The commutative property is where A x B = B x A. Therefore it does not matter if the gain is before or after the linear stages."
# "The Mid switch, sometimes labeled "Deep", shorts out the 390 pF cap in the tone stack (which is in series with a 2 nF cap). All that is left then is the 2 nF cap. With PAB active this lowers the lowcut frequency." [http://forum.fractalaudio.com/threads/dumbles-in-q2.110382/#post-1321445]
# "Maybe the best clean model IMO. You have to really crank the MV though (just like the real amp)." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-8-00-public-beta.126728/page-7#post-1507967]
# "The only amps with a bright cap on the MV are Dumbles and their various clones/derivatives. This was/is done to compensate for the lack of a buffer for the fx loop. The loop send is taken right off the MV which means the output impedance is very high. Any significant length of cable will then attenuate the highs due to the cable capacitance. The bright cap boosts the highs to compensate. It's the same idea as a bright cap on your guitar's volume knob. Crude. FWIW, this is a terrible loop design but "it's a Dumble" so it's all part of the mystique. Dumble then released the "Dumbleator" which is nothing more than a buffer and recovery in an external box. Dumble fanatics, of course, claim that to have the true Dumble experience you MUST use the Dumbleator which is just another load of BS." [https://forum.fractalaudio.com/threads/pick-attack.137945/#post-1720592]
# "We actually own a real Dumble. I bought it off a lawyer (surprise, surprise) some years ago who was in trouble with the IRS. Also a matching 4x12 cab. Both in mint condition. At the time I paid $50K for both. Probably worth twice that now." [https://www.thegearpage.net/board/index.php?threads/modelers-with-accurate-dumble-models.2120479/page-7#post-30771582]
# "PAB disconnects some components in the tone stack. The treble cap is still in the circuit path." [https://forum.fractalaudio.com/threads/ods-pab.180951/#post-2215259]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-ods-100-dumble-overdrive-special.114390/ Yek's write-up]

==ODS-100 FORD==

==ODS-100 FORD PAB==

==ODS-100 FORD PAB MID==

==ODS-100 HRM==

==ODS-100 HRM MID==

==PVH 6160 BLOCK (Peavey "Block Letter" EVH 5150)==

[[File:5150.jpg|300px]]

Models:
* Rhythm channel with Crunch switch engaged
* Lead channel

[[Cabinet models list | Cab:]] Peavey 4x12 (Sheffield 1200)

Pre Gain, Post Gain (Master), Low, Mid, High, Resonance, Presence, Bright and Crunch switches (Rhythm channel only, not modeled)

Power tubes: 6L6

# "I have a "holy grail" Block Letter 5150 (supposedly). It sounds way better than most 5150s for some reason which is a good thing for you guys. I think it's partly due to the fact that it has a bias mod so it's biased a bit warmer than a stock version." [https://forum.fractalaudio.com/posts/1152978]
# (differences between Peavey 5150 and 6505) "There are differences. The input gain network is different and the coupling cap after the second triode stage is a different value." [https://forum.fractalaudio.com/threads/peavey-invective-killer-amp.172625/post-2088479]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-pvh-6160-block-evh-5150-“block-letter”.114607/ Yek's write-up]

==PVH 6160 BLOCK CRUNCH==

==PVH 6160+ CLEAN (Peavey 6505+ / EVH 5150-II)==

[[file:6505.jpg|300px]]

Models:
* Clean channel, Bright switch OFF
* Clean channel, Bright switch ON
* Crunch channel, Bright switch OFF
* Crunch channel, Bright switch ON
* Lead channel

[[Cabinet models list | Cab:]] Peavey 4x12 (V30)

Rhythm channel: Pre (gain), Bright switch (6dB at 2kHz), Crunch switch, Low, Mid, High, Post (Master), Resonance, Presence

Lead channel: Pre (gain), Low, Mid, High, Post (Master), Resonance, Presence

Power tubes: 6L6

# "Chris Quigley's 6505 was the reference amp. It's my amp now. It's a very good sounding one." [https://forum.fractalaudio.com/posts/824411]
# (channel 1) "Someone was looking for that amp model recently so I dug our 6505+ out and was surprised at how nice that channel sounds." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-1-03-firmware-release.106931/#post-1278700]
# "A 6505+ is identical to a 5150 except it has no bright cap. Use the 5150 model and turn off the bright switch." [https://forum.fractalaudio.com/threads/request-acoustic-peavy-6505.56527/#post-711922]
# "The Bright switch on clean and crunch channels does not engage a capacitor on the drive potentiometer as is typical but instead disengages a treble cut circuit"

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-pvh-6106-peavey-6160-evh-5150-ii.114608/ Yek's write-up]

==PVH 6160+ CLEAN BRIGHT==

==PVH 6160+ CRUNCH==

==PVH 6160+ CRUNCH BRIGHT==

==PVH 6160+ LEAD==

==PLEXI 100W 1970 (1970 100W Marshall Plexi)==

[[file:SLP.png|300px]]

Plexi models:
* 1970 100 watts, EL34
* 1969 100 watts, High Treble channel
* 1969 100 watts, Normal and High Treble channels jumpered
* 1969 100 watts, Normal channel
* 1972 50 watts, 6550 power tubes
* 6AC7 50 watts, 6AC7 power tubes
* 1981 50 watts JMP with master volume, EL34
* 1967 50 watts, EL34, High Treble channel ("High 1")
* 1967 50 watts, EL34, High Treble channel ("High 2") (2nd triode stage has a 0.68uF cathode bypass capacitor, which was added in the early 70’s and gives a slightly brighter tone)
* 1967 50 watts, EL34, Normal and High Treble channels jumpered
* 1967 50 watts, EL34, Normal channel

[[Cabinet models list | Cab:]] Marshall 4x12 (G12M, G12H)

Volume Normal / Volume Treble, Bass, Middle, Treble, Presence, Master (Plexi 2204 only)

# "1970 Marshall 1959SLP 100 has a darker, smoother sound than earlier Plexis."
# "One of the first mods people make to real 'Plexi' Marshalls is to "clip the bright cap". The bright cap varied over the years, supposedly depending on what was lying around in the shop. The model defaults to the bright cap in the circuit. If you turn off Bright you're effectively clipping the bright cap. The bright cap in Marshalls can be very bright and harsh. However, if you crank the Master you might find the extra brightness helps compensate for the power amp getting darker."
# "It's the way a Plexi is supposed to sound. That's due to the cathode follower. That raspiness helps it cut through in a mix. I own three of them and they are that fizzy." [https://forum.fractalaudio.com/posts/576475]
# "Don't be afraid to turn the bass all the way down or the treble all the way up. Just like with the actual amp. For example, on the Normal channel of a Plexi most people turn the bass way down. Otherwise it's too flubby." [https://forum.fractalaudio.com/posts/577248]
# "My settings for a "typical" Plexi tone are Bass: 2, Mid: 8, Treble 7.5. Adjust Presence to taste." [https://forum.fractalaudio.com/posts/1179420]
# "Try the Plexi 100W 1970 with Factory Cab 54. Be sure to dial it in like you would in 1970, i.e. turn the Mid, Treble and Presence way up; turn Norm Drive and Bass down a bit." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-2-00-public-beta-deux.109702/#post-1312811]
# (Boston/Rockman sound) "Plexi Jump. Everything on 7. Put a Filter block in front: Type: Peaking, Freq: ~800 Hz, Q: 0.707, Gain 12 dB."
# (Plexi 100W 1970) "I've never cared for that model nor the actual amp. IMO it doesn't have enough feedback (100K off the 4-ohm tap). Some amps of that era had 47K off the 4-ohm tap. Some had 47K off the 8-ohm tap. Some had 100K off the 8-ohm tap and some even had 47K off the 16-ohm tap! IOW all over the map. Bottom line: try adjusting Negative Feedback. I always raise it up a bit with that model. Around 4 or so." [http://forum.fractalaudio.com/threads/plexi-100watt-1970-is-something-wrong-with-it-now.125522/#post-1493932]
# "What you are hearing is output transformer high frequency resonance. Old Plexis didn't do this because they had good transformers. New transformers are crappy and resonate at the cutoff frequency because they are underdamped. This causes a raspy, fizzy texture to the distortion. The transformer resonance is adjustable but the parameter isn't exposed to the user. When you turn it up you get that same squishy rasp that you are hearing. For the Plexis I have the damping set to flat with no resonance because that's how our vintage Plexis measure. Our 50W is a little underdamped but people complain about raspy high frequencies so I erred on the safe side." [http://forum.fractalaudio.com/threads/dimed-real-plexi-vs-dimed-simulation-q8-01.127161/page-2#post-1513888]
# "When modding Marshalls for higher gain sometimes the modder will decrease the input frequency response to reduce noise and fizziness. You can do this by reducing the high-cut frequency in the input EQ. Or you can use a high-shelf filter which is a little more subtle. Another technique is to put a capacitor across the second-to-last triode stage. This is the "Triode 1 Plate Freq" parameter. Reduce this to around 2 kHz to start which is typical of amps like an SLO100, etc." [https://forum.fractalaudio.com/threads/dialling-in-the-marshalls.143682/post-1707222]
# "The Plexi 100W 1970 model is a non-MV "Plexi". Circuit is slightly different than the late 60's model (Plexi 100W)." [https://forum.fractalaudio.com/threads/marshall-amp-question.155223/post-1847908]
# "All the distortion comes from the power amp so the tone controls don't do much." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2052743]
# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]
# [[Amp_block#NEGATIVE_FEEDBACK|Negative feedback values]]
# "(100W model) Our reference amp has a 560p treble cap and a 10A treble pot taper. Both components appear to be original. The tech who checked it out after I bought it said it was one of the best sounding 100W Plexis he'd ever heard. That tech just happens to be Alan Phillips of Carol-Ann Amps. So I modeled it to agree with the reference amp." [https://forum.fractalaudio.com/threads/modeling-questions.199009/post-2491136]
# (100W model) It's a '69. The 50W might be a '67. Hard to keep track of it all. I must have at least a dozen Marshalls now." [https://forum.fractalaudio.com/threads/modeling-questions.199009/post-2491192] and [https://forum.fractalaudio.com/threads/nothing-like-a-real-plexi.64593/post-801933]
# (100W model) "All the pots are log pots in our reference amp" and "I was puzzled by the pot tapers but they all look original. I then thought about it a bit and wondered if that's why Bogner uses log pots for his amps. His stuff is definitely Plexi-inspired. Or maybe all Marshall could find at the surplus electronics store that week was log pots. Who knows." [https://forum.fractalaudio.com/threads/modeling-questions.199009/post-2491180]
# (50W model) "Our reference 50W Plexi has a 68nF presence cap and the presence network is JCM800-style." [https://forum.fractalaudio.com/threads/modeling-questions.199009/post-2491179]

[http://forum.fractalaudio.com/threads/late-70s-marshall-jmp-master-model-50w-mk2-lead.135541 Forum discussion about the Plexi 2204 model]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-plexi-marshall-plexi.114529/ Yek's write-up]

==PLEXI 100W HIGH (1969 100W Marshall Plexi)==

# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]
# "The power supply sags more in a 100W. On our reference 100W Plexi the supply sag is almost double that of our 50W." [https://forum.fractalaudio.com/threads/marshall-jmp-100w.198803/post-2478167]
# "The topology of that model does not support a bright cap and the actual amp has no bright cap." [http://forum.fractalaudio.com/threads/q2-01-plexi-50w-nrml-bright-cap-doesnt-work.111836/#post-1337410]
# "All the pots are Logarithmic pots in our reference amp." [https://forum.fractalaudio.com/threads/modeling-questions.199009/post-2491161], Authors Note: Standard Plexi tonestack has Linear pots for Mid and Treble, only Bass is Log.

==PLEXI 100W JUMPED==

==PLEXI 100W NORMAL==

==PLEXI 2204 (1981 50W Marshall JMP 2204)==

# "Based on a 1981 JMP 50W Master Volume head."
# (recommended settings) "Everything on 10."
# "There were several versions of the "2204" Plexi. Our model is based on a 1981 2204 Master Volume JMP. It has a different circuit than a JCM800." [https://forum.fractalaudio.com/threads/marshall-sound-clips.169296/post-2034903]
# "The model is based on the Hi input of a 1981 50W Master Volume "2204" Plexi. There were two versions of the 2204. One was essentially a Plexi with a Master Volume. Similar to a 1987x but with some different values and voltages in addition to the MV. The other was virtually identical to a JCM800. The model is the Plexi version. Mine is an '81 and doesn't have cascaded gain stages." [https://forum.fractalaudio.com/threads/plexi-2204-question.178464/]
# "It's a 1981 "CSA" 2204."[https://forum.fractalaudio.com/threads/plexi-2204-question.178464/post-2175316]
# [https://forum.fractalaudio.com/proxy.php?image=https%3A%2F%2Fimages.reverb.com%2Fimage%2Fupload%2Fs--0dABDsRq--%2Fa_exif%2Cc_limit%2Ce_unsharp_mask%3A80%2Cf_auto%2Cfl_progressive%2Cg_south%2Ch_620%2Cq_90%2Cw_620%2Fv1518443139%2Fvgiq3h9wiuaj0jw2wxhb.jpg&hash=5b419d07341f4bdad48af0657dcd11de Picture of the modeled amp]

==PLEXI 50W 6550 (1972 50W Marshall Plexi)==

* High Treble Channel

==PLEXI 50W 6CA7 (50W Marshall Plexi)==

Models:
* Single channel
* Jumped channels

# "That's based on my favorite Plexi. I have several but this particular one has 6CA7s and 82K grid resistors(!). Usually the grid resistors are 220K." [https://forum.fractalaudio.com/threads/plexi-50w-6ca7-sooooo-good.169084/post-2031777]

==PLEXI 50W 6CA7 JUMPED==

==PLEXI 50W HIGH 1 (1967 50W Marshall Plexi)==

==PLEXI 50W HIGH 2==

# "Similar to Plexi 50W High 1 except the second triode stage has a 0.68uF cathode bypass capacitor. The second bypass capacitor was added in the early 70’s and gives a slightly brighter tone."
# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]

==PLEXI 50W JUMPED==

==PLEXI 50W NORMAL==

# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]

==PORTA-BASS (Ampeg Portaflex bass amp)==

Model:
* Single channel

[[Cabinet models list | Cab:]] SVT cab with one or more 10”, 12” or 15” Eminence speakers

Gain, Volume, Bass, Mid, Treble, Mid Frequency (not modeled), input pad (not modeled), compression (not modeled), limiter (not modeled), Ultra Hi switch, Ultra Lo switch (not modeled)

It's not been disclosed on which Portaflex amplifier the model is based

Power tubes: 6L6

Notes: see SV Bass

==PRINCE TONE 5F2 (Fender Tweed Princeton, 5F2-A)==

[[file:princeton.jpg|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Fender 1x10 (C10n)

Volume, Tone

Power tubes: 6V6

[http://forum.fractalaudio.com/posts/1370144/ Yek's write-up]

==PRINCE TONE AA964 (silverface Fender Princeton without reverb, AA964)==

Model:
* Single channel

Volume, Bass, Treble

Power tubes: 6V6

# "Based on a Fender AA964 Princeton. This particular amp is an early CBS “Silverface” but still using pre-CBS design and components."

==PRINCE TONE REVERB (1966 blackface Fender Princeton with reverb, AA964)==

[[file:princetonreverb.jpg|300px]]

Model:
* Single channel

Volume, Bass, Treble, Reverb (not modeled)

Power tubes: 6V6

# "A Princeton Reverb has an extra gain stage due to the reverb recovery. Hence it has more gain." [https://forum.fractalaudio.com/threads/what-causes-this-volume-difference.97845/#post-1174202]

==RECTO1 ORANGE MODERN (MESA Dual Rectifier, 2 channels)==

[[file:recto.png|300px]]

Rectifier models:
* Recto1: original 2-channel Rectifier, Orange channel, Modern mode
* Recto1: original 2-channel Rectifier, Orange channel, Vintage mode
* Recto1: original 2-channel Rectifier, Red channel, Modern mode
* Recto2: later 3-channel Rectifier, Orange channel, Modern mode
* Recto2: later 3-channel Rectifier, Orange channel, Vintage mode
* Recto2: later 3-channel Rectifier, Red channel, Modern mode
* Recto2: later 3-channel Rectifier, Red channel, Vintage mode

[[Cabinet models list | Cab:]] Mesa 4x12 (V30)

Gain, Master, Bass, Middle, Treble, Presence

Power tubes: 6L6

# "The reason you're hearing the highs rolled off is because the Master is too high. As you increase the Master the highs get muffled. 7.02 for the Recto Master is ridiculous and will sound like crap." [https://forum.fractalaudio.com/threads/axe-fx-vs-tube-amps-my-first-experience.27192/page-3#post-412068]
# "Note that the Orange Modern and Red Modern models have no negative feedback and therefore the Presence control is a Hi Cut control." [https://forum.fractalaudio.com/threads/version-10-00-stuff.63202/#post-783037]
# "A typical Recto cabinet has a resonant frequency a little over 100 Hz." [https://forum.fractalaudio.com/threads/dual-recto-with-the-lb-2-vs-the-axe-fx-iii-and-more.143501/page-2#post-1699892]
# "The unique thing about a Dual Recto tone stack is that the Presence control is part of the tone stack. So the Recto tone controls also interact with the presence control." [https://forum.fractalaudio.com/threads/dual-recto-with-the-lb-2-vs-the-axe-fx-iii-and-more.143501/#post-1699011]
# "Rectos don't have a Depth control and even if they did it wouldn't do anything in Modern Red mode since that mode has no negative feedback. When you put a Recto into Modern Red mode it opens a relay which removes the NFB." [https://forum.fractalaudio.com/threads/recto-depth.92482/#post-1111780]
# "Real Rectos are bassy/fizzy beasts but that tone works great for certain genres." [https://forum.fractalaudio.com/posts/658849]
# "If you are using the Modern modes be very careful with the MV. If you turn it up too high it will flub out really quick. If in doubt reduce the MV. Compensate with the Level control." [https://forum.fractalaudio.com/posts/829334]
# "The Modern mode in Rectos has no negative feedback so there's a huge bass boost from the speaker impedance. Fortunately you can reduce this by reducing the LF Resonance on the Spkr tab which is something you can't do with the real amp without trying different speakers or cabinet." [https://forum.fractalaudio.com/posts/829906]
# "Depth works by varying the negative feedback at low frequencies. There is no NFB in the Modern Red mode so the Depth knob won't do anything." [https://forum.fractalaudio.com/posts/1111770]
# (Thordendal models) "The old Recto models weren't terribly accurate. When G3 came out the models were accurate but Fredrik contacted me and said something like "ahhhhh, I loved the old Recto model". So I took the old Recto models and made them "Thordendal" models." [http://forum.fractalaudio.com/threads/thordendal-modern-vs-recto-1-modern-red.91645/#post-1269530]
# "All passive tone controls interact and all the Axe-Fx tone stacks replicate this behavior. The unique thing about a Dual Recto tone stack is that the Presence control is part of the tone stack. So the Recto tone controls also interact with the presence control." [https://forum.fractalaudio.com/threads/dual-recto-eq-potentially-silly-question.93890/#post-1126242]
# "If you are using the Modern mode then it's all about the Spkr page. Since that mode has no negative feedback the speaker resonance has a tremendous effect on the sound. Adjust LF Res, Freq and Q to get desired response." [http://forum.fractalaudio.com/threads/anyone-have-any-luck-with-the-rectifier-models.109907/#post-1315682]
# "Another thing with the Modern modes is that the power amp distorts early (again since there is no negative feedback and, therefore, the power amp has a lot more gain). At 9:00 on the Master the power amp is distorting (it's probably a linear taper pot for the ol' "Wow, this amp is loud bro!"). (...) Another thing is that if you put ANYTHING in the loop of a Recto it changes the tone significantly. Even just a short cable. All the models were made with the loop off. And another thing is that Rectos changed a lot. I have three of them and they all sound completely different. One of them has a different value Gain pot than the others. One of them has a different value bright cap than the one with the same Gain pot. Since the gain pot and bright cap interact this makes a HUGE difference. Experiment with the Bright Cap value. The Recto1 models are based on our Rev. F (IIRC, whatever the desirable ones are). The Recto2 models are based on the latest version." [http://forum.fractalaudio.com/threads/anyone-have-any-luck-with-the-rectifier-models.109907/#post-1315714]
# "We have three of them, a single and two duals." [http://forum.fractalaudio.com/threads/when-were-the-rectos-improved.122719/#post-1459883]
# "If you want that Recto crunch but not so flubby and fizzy try the SOLO models." [http://forum.fractalaudio.com/threads/ax8-v7-00-public-beta.125015/page-3#post-1487394]
# "A Recto is not a Mark series amp. Totally different preamp topology. A Recto preamp is very similar to a SLO100." [https://forum.fractalaudio.com/threads/the-greatest-digital-guitar-recording-of-all-time.154788/post-1841448]
# (amp model closest to the MESA Roadster) "Recto 2." [https://forum.fractalaudio.com/threads/what-amp-model-is-closest-to-the-mesa-roadster.127060/post-1512755]
# "The Rectifier preamp is almost identical to an SLO100." ... "There's a treble cut on the tone stack and a some minor changes to the power amp and power supply but it's basically a ripoff. The schematics are readily available for both so anyone interested can see for themselves. Personally I hate the 39K resistor. It biases the stage much too cold for my tastes. It prevents blocking distortion but there are better ways to do it IMO. The FAS Modern model is similar but biases the stage more towards the center." [https://forum.fractalaudio.com/threads/new-amp-models.159097/post-1901310]
# "Using the loop on a modern 3-channel rectifier changes the tone pretty dramatically (we model the amp with the loop bypassed). There are several reasons for this:
## The source impedance to the power amp is changed.
## There is a treble peaker on the Output pot. Presumably this was done to counteract treble loss in the loop.
## An extra highpass filter is present due to the loop send stage. The corner frequency is around 30 Hz. That's low but it does affect subharmonics due to intermodulation. I would've made the capacitor around 1uF." [https://www.thegearpage.net/board/index.php?threads/blind-test-mesa-dual-rectifier-vs-mystery-modeler-update-results-revealed.2208367/post-31646126]
# "Recto2 is based on a new 3-channel Dual Rectifier. Recto1 is based on the original 2-channel." [https://www.thegearpage.net/board/index.php?threads/blind-test-mesa-dual-rectifier-vs-mystery-modeler-update-results-revealed.2208367/post-31647001]
# "I have three Rectos: an old Single Rectifier, an old (Rev. G maybe) Dual Rectifier and a new Dual Rectifier. They all sound completely different. The old Dual is the best sounding of the bunch." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-9-cygnus-firmware-public-beta-6.171176/post-2062420]
# "The MV taper of the model is authentic so just like the real amp the power amp starts to clip very early. With the real amp there's audible feedback (as in it gets insanely loud) but with the model you don't get that and humans have this weird thing where they don't like knobs to deviate from noon. I've debated changing the taper or adding a pad between the preamp and power amp but, in the end, I decided to keep things authentic." [https://forum.fractalaudio.com/threads/simple-tip-for-recto-tones.174349/post-2114224]
# "You have to be very careful with the Master Volume. A Recto will start saturating the power amp in Modern mode at VERY low MV settings. Once the power amp starts clipping the tone will change. With digital products I often see people set the MV higher than they would on the real amp because there are no sonic repercussions (i.e., pissing off the wife/neighbors, knocking Grandma's urn off the mantel, etc.). If an emulation sounds darker or more midrangey than the real amp try turning down the MV. If it's a good emulation you should find a point (around 1-2) where you can hear the power amp start to saturate. Go up/down from there to get the desired power amp overdrive." [https://www.thegearpage.net/board/index.php?threads/why-are-rectifier-emulations-so-off.2341907/post-34347979]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-recto1-and-recto2-mesa-dual-rectifier-2-ch-and-3-ch.114701/ Yek's write-up]

==RECTO1 ORANGE NORMAL==

==RECTO1 RED==

==RECTO2 ORANGE MODERN (MESA Dual Rectifier, 3 channels)==

==RECTO2 ORANGE VINTAGE==

==RECTO2 RED MODERN==

==RECTO2 RED VINTAGE==

==REVV GEN GREEN 1 (REVV GENERATOR 120)==

Models:
* Green channel, least aggression (green)
* Green channel, tight saturation (blue)
* Green channel, fat saturation (red)
* Purple Gain channel, least aggression (green)
* Purple Gain channel, tight saturation (blue)
* Purple Gain channel, fat saturation (red)
* Red Gain channel, least saturation (green)
* Red Gain channel, tight saturation (blue)
* Red Gain channel, fat aggression (red)

[[Cabinet models list | Cab:]] Revv 4x12 (V30)

Gain, Bass, Mid, Treble, Level, Master, Presence, Depth. Options on Clean and Crunch channels: Wide / Drive / Bright. Options on Purple and Red channels: Aggression / Bright / Cut / Fat.

Power tubes: 6L6

# "Revv is a great amp. Sort of a Marshall/SLO vibe but more open. Really well designed and built." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-22-00-release.195047/post-2429051]
# "The Revv actually has an MV that makes sense. Instead of driving the power amp into oblivion at around 3, power amp overdrive doesn't start happening until you turn the knob up quite a bit." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-22-00-release.195047/post-2429139]

==REVV GEN GREEN 2==

==REVV GEN GREEN 3==

==REVV GEN PURPLE 1==

==REVV GEN PURPLE 2==

==REVV GEN PURPLE 3==

==REVV GEN RED 1==

==REVV GEN RED 2==

==REVV GEN RED 3==

==RUBY ROCKET (Paul Ruby Rocket)==

[[File:rocket.jpg|300px]]

Models:
* Bright switch ON
* Bright switch OFF

[[Cabinet models list | Cab:]] 1x12 (Alnico, G12M)

Volume, Bass, Treble, Cut, Bright switch

Power tubes: EL84

# "The Ruby Rocket is not the same as an actual Trainwreck Rocket. There are topology differences and the amps don't sound the same." [https://forum.fractalaudio.com/posts/1154295]
# "Ruby Rocket is based on a Paul Ruby Rocket which is based on a TW Rocket but with some notable differences." [https://forum.fractalaudio.com/threads/axe-fx-ii-firmware-18-00-public-beta.96198/page-30#post-1154336]
# "The Bright switch changes a coupling cap and the treble cap in the tone stack. This cuts the bass, shifts the midrange and lowers the gain slightly. That's why there are two separate models. Otherwise you would just engage the Bright switch under the Treble knob."
# "The Ruby Rocket has a bright switch but it's actually a channel select (selects the bright channel)."

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-ruby-rocket-paul-ruby-rocket.114725/ Yek's write-up]

==RUBY ROCKET BRIGHT==

==SV BASS 1 (Ampeg SVT bass amp)==

[[File:ampeg.jpg|300px]]

SVT models:
* SV Bass 1: Fractal Audio's model prior to the change in firmware Ares 2.05 and later
* SV Bass 2: channel one of a 1970 Ampeg SVT with 6550 power tubes and the midrange switch in position 3

Note: on the Axe-Fx II (firmware Ares) these models are reversed [https://forum.fractalaudio.com/threads/sv-bass-1-and-sv-bass-2-in-ares-1-03.149364]

[[Cabinet models list | Cab:]] SVT 8x10

Volume, Treble, Midrange, Bass, Master, Midrange switch, Ultra-Hi switch (= Bright), Ultra-Lo switch (not modeled)

Power tubes: 6550

Uses a James tonestack [https://forum.fractalaudio.com/threads/have-we-reached-the-end-of-new-amp-models-in-the-axe-3.184271/post-2482710]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-sv-bass-ampeg-svt.115282/ Yek's write-up]

==SV BASS 2==

==SHIVER CLEAN (Bogner Shiva 20th Anniversary)==

[[File:shiva.png|300px]]

Models:
* Clean channel
* Lead channel

[[Cabinet models list | Cab:]] Bogner 1x12 or 2x12 (Classic 80, V30)

Clean channel: Volume, Bass, Treble, Bright switch. Shared: Master, Presence, Excursion, Boost switch (not modeled)

Lead channel: Gain, Volume, Bass, Middle, Treble, Shift EQ (not modeled), Bright switch, Mode switch (not modeled). Shared: Master, Presence, Excursion, Boost switch (not modeled)

Power tubes: KT88

# "People think Bogners are dark but they really aren't. The reason they seem that way is the pot tapers. Most people assume knobs should be set somewhere around noon. If you do this on a Bogner it's like turning the treble way down on a Marshall. Close your eyes and adjust the tone controls with your ears. Don't be afraid to turn them way up or way down." [https://forum.fractalaudio.com/posts/1031334]
# "Human nature is to put the knobs near noon. We are reticent to deviate much from noon. Amp designers exploit this and use different tapers to change the sound of their amps WITH THE KNOBS AT NOON. A prime example are Bogner amps. Everyone says "Bogner amps are dark". No they aren't. But he uses a Log10A taper for the treble pot. It's a standard Marshall tone stack. Usually a linear taper pot is used for the treble. The treble knob at 5.0 (noon) on a Bogner is equivalent to the treble knob at 1.0 on a Marshall. People put the knob at 5.0 and go "wow, this amp is dark". No it isn't. If you turned the treble up to 8 or 9 it would sound a lot like a Plexi but humans are reticent to turn the knobs to extremes. Amp designers know this and exploit it to give their amps a "signature sound"." [https://forum.fractalaudio.com/posts/1047275]
# "The original Shiva models were based on a borrowed amp. We now have a 20th Anniversary Shiva (with KT88s) and the new models are based on that amp. We did notice that this amp has less gain than the one used originally but the model is faithful to the amp." [https://forum.fractalaudio.com/posts/1152978]
# "Bogner's are notoriously "slow" due to the low B+ voltage. Main reason I can't get along with them. You can try increasing the Variac." [https://forum.fractalaudio.com/threads/fast-pick-attack-amp.170370/post-2049711]
# "Most amps use a linear taper for the treble pot. Bogners use a log taper. So when the knob is at noon on a Bogner it's similar to 8 o'clock on most amps." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486/post-2067364]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-shiver-bogner-shiva-20th-ann.114764/ Yek's write-up]

==SHIVER LEAD==

==SOLO 100 CLEAN (Soldano SLO-100)==

[[File:slo.jpg|300px]]

Models:
* Normal channel in Clean mode
* Normal channel in Rhythm mode
* Overdrive channel

[[Cabinet models list| Cab:]] Soldano 4x12 (Eminence)

Gain, Bass, Middle, Treble, Master, Presence, Bright switch (Normal channel only), Depth (with Depth mod)

Power tubes: 6L6

# "The SLO-100 is the loudest amp I've ever used. It feels like there's a small nuclear explosion going off inside when ever you hit a power chord. It's a wicked amp but not something I would recommend for anything but large gigs. If you like the SLO-100 model you might want to try the Recto models too. It's not widely known but the Rectifier preamp is a derivative of the SLO-100. Some minor changes but the basic topology is identical."
# "I have a really good SLO-100. An original black faceplate version. Pristine condition. That amp was one of the primary amps used in the G2 modeling development. It was by studying that and a really nice JCM-800 that I finally figured out the secret to cathode follower." [https://forum.fractalaudio.com/posts/562187]
# "Mine doesn't have the depth mod but I used the values from the schematic I have and I believe the schematic is correct." [https://forum.fractalaudio.com/posts/830925]
# "SLOs are brittle at low volumes. When you crank them up it smooths out. The problems is at cranked volumes they can kill small animals."
# "The key to an SLO100 is to run the MV high so that the mids thicken up. Otherwise it's a shrill mess. In certain contexts with the right IR it can be a cool sound." [https://forum.fractalaudio.com/posts/1146118]
# "Note that the knobs on '5' on the Axe-Fx correspond to '6' on an SLO because they go to 11. 'Noon' on an SLO isn't actually the knobs at half-way. The range of the knobs is like 8:00 to 6:00 as opposed to 7:00 to 5:00. They're biased clockwise." [https://forum.fractalaudio.com/posts/1057829]
# "Another caveat when comparing amps: many times the knobs aren't "centered". IOW if you put the Treble knob at noon it isn't actually at 50%. You can see this by turning the knob all the way down and all the way up. It may not be symmetrical. This happens when the pots don't have a flat spot and/or the pot is rotated within the mounting hole. Or in the case of an SLO100 it is intentional. On an SLO100 all the way down is around 8:00 and all the way up is 6:00 so 50% is around 1:00 not noon." [https://forum.fractalaudio.com/posts/1158815]
# "Many people find SLOs too bright. The "Warren Haynes" mod is a popular mod to reduce the brightness."
# "Those amps are all designed to get their character from power amp distortion. If you don't push the power amp all you are hearing is the preamp which is voiced to be trebly. The power amp then compresses the highs and the sound gets fatter."
# "If you want that Recto crunch but not so flubby and fizzy try the SOLO models. They're much brighter so I turn the treble down quite a bit." [http://forum.fractalaudio.com/threads/ax8-v7-00-public-beta.125015/page-3#post-1487394]
# "SLO 100s are NOT smooth amps. They are nasty, aggressive things that you have to crank the MV." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-00-beta-3.148907/page-4#post-1764615]
# "A Recto is not a Mark series amp. Totally different preamp topology. A Recto preamp is very similar to a SLO100." [https://forum.fractalaudio.com/threads/the-greatest-digital-guitar-recording-of-all-time.154788/post-1841448]
# "The Rectifier preamp is almost identical to an SLO100." [https://forum.fractalaudio.com/threads/new-amp-models.159097/post-1901310]
# "They're pretty awesome amps but to sound great you have to crank 'em and they're ear-splitting loud." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-09.162488/post-1947441]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-solo-100-soldano-slo-100.114877/ Yek's write-up]

==SOLO 100 LEAD==

==SOLO 100 RHYTHM==

==SOLO 88 CLEAN (Soldano X88R preamp)==

[[image:x88r.jpg|300px]]

Models:
* Clean channel
* Rhythm channel
* Lead channel

Gain, Bass, Middle, Treble, Volume, Bright switch (Clean and Rhythm channels only)

Power tubes: same as SLO-100 model (6L6)

# "Solo 88 RHY is based on an X88R since the rhythm channel of an X99 is identical to an SLO-100. FWIW, I have two X88Rs and the model agrees with both."

[https://forum.fractalaudio.com/posts/718846/ Yek's write-up]

==SOLO 88 LEAD==

==SOLO 88 RHYTHM==

==SOLO 99 CLEAN (Soldano/Caswell X99 preamp)==

[[File:Cliff X88.jpg|300px]]

Models:
* Clean channel
* Lead channel, Bright OFF
* Lead channel, Bright ON

Gain, Bass, Middle, Treble, Volume, Bright switch

Power tubes: same as SLO-100 model (6L6)

# "The rhythm channel of an X99 is identical to a SLO 100." [https://forum.fractalaudio.com/posts/718846]
# "Power amp: same as SLO100." [https://forum.fractalaudio.com/posts/1250203]
# "The bright cap on the X99 Clean is not across the Drive pot. The exposed "Bright Cap" is across the Drive pot, the X99 clean channel does not have one." [https://forum.fractalaudio.com/threads/found-a-bug-soldano-x99-clean-bright-cap.28046/post-418468]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-solo-88-and-solo-x99-soldano-x88r-and-x99.114878/ Yek's write-up]

==SOLO 99 LEAD==

==SOLO 99 LEAD BRIGHT==

==SPAWN NITROUS 1 (Splawn Nitro)==

[[file:nitro.gif|300px]]

Models:
* Overdrive channel in OD-1 (Rhythm) mode
* Overdrive channel in OD-2 (Lead) mode

[[Cabinet models list| Cab:]] Splawn 4x12 (G12M, G12-65, V30)

Resonance, Presence, Bass, Middle, Treble, Master, Gain

Power tubes: KT88

# "Based on a Splawn Nitro with KT-88 power tubes."

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-spawn-nitrous-splawn-nitro.114911/ Yek's write-up]

==SPAWN NITROUS 2==

==SPAWN Q-ROD OD1-1 (Splawn Quickrod)==

[[File:quickrod.jpg|300px]]

Models:
* Overdrive channel, Rhythm mode, 1st gear ("Plexi")
* Overdrive channel, Rhythm mode, 2nd gear ("hot-rodded JCM 800")
* Overdrive channel, Rhythm mode, 3rd gear ("super hot-rodded 800")
* Overdrive channel, Lead mode, 1st gear
* Overdrive channel, Lead mode, 2nd gear
* Overdrive channel, Lead mode, 3rd gear

[[Cabinet models list | Cab:]] Splawn (G12M, G12-65, V30)

Presence, Bass, Middle, Treble, Volume, Gain, Mode

Power tubes: EL34

# "The reason Splawns sound weird is because the tone stack is plate driven. You lose the cathode follower compression and the high source resistance of the plate alters the tone stack frequency response. The plate driven tone stack in the Splawn reduces the highs considerably. You can see this is you run Tone Stack Calculator for the Marshall tone stack and increase the source resistance." [https://forum.fractalaudio.com/posts/1070559]
# "OD2 switches in a cathode bypass cap which increases the gain of that stage." [https://forum.fractalaudio.com/posts/1158818]
# "The Quick Rod is a bit odd in that the Drive pot is linear taper. Most amps use an audio taper pot. This means that at noon the amp is nearly at full gain. Not sure why they did it that way but it is what it is." [https://forum.fractalaudio.com/posts/1159425]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-spawn-rod-splawn-quickrod.114968/ Yek's write-up]

==SPAWN Q-ROD OD1-2==

==SPAWN Q-ROD OD1-3==

==SPAWN Q-ROD OD2-1==

==SPAWN Q-ROD OD2-2==

==SPAWN Q-ROD OD2-3==

==SUHR BADGER 18 (Suhr Badger 18)==

[[File:badger18.jpg‎|300px]] [[File:badger30.jpg‎|300px]]

Badger models:
* Badger 18
* Badger 30

[[Cabinet models list | Cab:]] Suhr 1x12 or 2x12 (V30, G12M)

Bass, Middle, Treble, Gain, Power (controls Power Scaling, not modeled), Drive (acts as Master with Power at 10)

Power tubes: EL84 (Badger 18), EL34 (Badger 30)

# "The Badgers were MIMIC'd with power scaling at full. The knobs are a bit confusing on a Badger. The knob closest to the input jack is labeled "Gain". It is equivalent to the Drive knob in the Axe. The knob labeled Drive is the Master Volume." [https://forum.fractalaudio.com/posts/830810]
# "The controls on the Badger are a bit confusing. Master Volume is labeled Drive. You have the Drive at 10 which means your power amp is at full blast. This can make the bass muddy. Turn the Drive down." [https://www.thegearpage.net/board/index.php?threads/i-have-to-say-im-a-little-upset.2205478/post-31553496]
# "IMO the designs are poor because... wait for it... they exhibit a papery buzz. The problem with most cathode biased Class A amps is, 1: they aren't really Class A (more like hot Class AB) and 2: They go into Class B operation when they are overdriven. The cathode capacitor charges up and the bias point shifts dramatically. This causes lots of crossover distortion (papery buzz). It's worse on lower notes because lower notes have more energy and charge the cap more. The is probably the reason Leo Fender switched to fixed bias amps with negative feedback. Fixed bias is just that, the bias point is fixed so the amp doesn't shift into Class B operation when overdriven (not as much anyways, depends on the bias circuit, grid stoppers, etc.). Negative feedback linearizes the amp and reduces the crossover distortion (at the expense of gain). That's why the buzzing went away when you increased negative feedback. Crossover distortion is a unique sound. For cleaner sounds it tends to be objectionable. For overdriven sounds some find it desirable. EVH ostensibly liked his amps biased cold to get some crossover distortion. There are even some amps that have circuits to intentionally generate crossover distortion. Some distortion pedals also do this. Lowering the Cathode Resistance reduces the crossover distortion as it keeps the amp in Class A operation longer but the tubes run hotter and don't last as long. This is not a problem with our virtual amps though. I forget the actual values but I'm pretty certain if you look at the Cathode Resistance value for those amps it's pretty high. This means the amps are biased somewhat cold to begin with and shift to very cold as soon as overdriven. One reason I like the AC-20 is that it runs the tubes hotter and exhibits less crossover distortion. The worst amp in this regard is the Badger 18. The cathode resistors are very large and the amp shifts into Class B operation early causing a spitty, buzzy distortion quality. This amp, however, is liked by many so that just goes to show that some people like that. It's like fuzz pedals. Some people like that spitty sound. I personally don't like it. Then there's shared vs. split cathode. If you look at the schematics on the web the Maz-38 is shared cathode. I could never get the model to sound exactly like our reference amp. Finally I traced the entire circuit and our particular amp is a split cathode. As soon as I changed the model to split cathode it was spot on. This is not exposed to the user though (there's a hidden shared/split switch)." [https://forum.fractalaudio.com/threads/papery-buzz-under-some-models.149193/page-2#post-1772639]
# "The Badger doesn't have a Bright switch." [https://forum.fractalaudio.com/threads/fixed-next-rel-wild-rumbling-chirping-artifacts-switching-between-presets.154544/post-1837842]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-suhr-badger-18-and-30.115086 Yek's write-up]

==SUHR BADGER 30 (Suhr Badger 30)==

==SUPER VERB NORMAL (1964 Fender Super Reverb, AB763)==

[[file:superreverb.jpg‎|300px]]

Models:
* Normal channel
* Vibrato channel

[[Cabinet models list | Cab:]] Fender 4x10 (C10R, C10Q, P10R)

Volume, Bass, Middle (Vibrato channel only), Treble, Bright switch, Reverb (not modeled), Vibrato (not modeled)

Power tubes: 6L6

# "I modeled the Super with V1 pulled as most people pull V1 so the amp has more grunt. Turn down the MV to make it cleaner."
# "The Super Reverb model is based on the amp with V1 removed (which is a common mod). This increases the level into the power amp by about a factor of two." [https://forum.fractalaudio.com/threads/xl-units-quantum-6-fw-austin-buddy-raw-amp-bank-part-i-feedback.123065/#post-1464566]
# "The Super Reverb model is "Diaz Modded". IOW, I pulled V1. This gives the amp a lot more gain so it's not surprising you're getting breakup at around 1.5. You can un-mod the model by turning down the MV Trim to around 0.5." [https://forum.fractalaudio.com/posts/851580]
# "A Pro Reverb is basically identical to a Super Reverb except for the speakers (and faceplate)." [https://forum.fractalaudio.com/posts/933261] And: "The Blackface Pro Reverb, model AA165, was virtually identical to the AB763 Super Reverb except for the speakers and tone stacks. If you use the Super Verb model and set the Tone Stack type to Blackface you'll basically have a Pro Reverb. Set the Mid control fairly high to emulate the fixed 6.8K mid resistor. I'd say around 7 or 8." [https://forum.fractalaudio.com/posts/1079578]
# (blackface) "Not a huge change with the Silverfaced versions. They're a little cleaner and brighter but the topology is the same. Some minor circuit changes here and there. Same transformers. The biggest change, IMO, was changing the PI resistors to 47K which gives you a little less gain in the PI." [https://forum.fractalaudio.com/posts/1252495]
# "The Super Reverb is really just a 50W version of a Twin Reverb with different speakers." [https://forum.fractalaudio.com/threads/wanted-amps-to-model.56753/page-4#post-713267]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-super-verb-64-blackface-fender-super-reverb-ab763.115124 Yek's write-up]

==SUPER VERB VIBRATO==

==SUPERTWEED (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "Original." [https://forum.fractalaudio.com/threads/supertweed.172803/post-2088909]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-supertweed-custom-model.115143/ Yek's write-up]

==SUPREMO TREM (Supro 1964T)==

[[File:supro.png|300px]]

Model:
* single model

[[Cabinet models list | Cab:]] Supro 2x12

Volume, Tone

Power tubes: 6973

# "They're simple amps with minimal tone shaping." [https://forum.fractalaudio.com/threads/time-for-another-supro.154552/post-1838288]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-supremo-trem-supro-1964t.115232/ Yek's write-up]

==TEXAS STAR CLEAN (MESA Lone Star Classic)==

[[file:lonestar.png|300px]]

Models:
* Clean channel
* Lead channel

[[Cabinet models list | Cab:]] Mesa 2x12 (C90)

Drive, Gain, Treble, Mid, Bass, Presence, Master, Voicing (not modeled)

Power tubes: 6L6

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-tx-star-mesa-lone-star.115405/ Yek's write-up]

==TEXAS STAR LEAD==

==THORDENDAL MODERN (custom model of MESA Dual Rectifier)==

[[file:meshuggah.jpg|300px]]

Models:
* Modern mode
* Vintage mode

Power tubes: 6L6

Notes: see Recto

# "The old Recto models weren't terribly accurate. When G3 came out the models were accurate but Fredrik contacted me and said something like "ahhhhh, I loved the old Recto model". So I took the old Recto models and made them "Thordendal" models." [http://forum.fractalaudio.com/threads/thordendal-modern-vs-recto-1-modern-red.91645/#post-1269530]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-thordendal-pre-g3-recto-models.115326/ Yek's write-up]

==THORDENDAL VINTAGE==

==TREMOLO LUX (blackface Fender Tremolux, AA763)==

[[File:tremolux.jpg|300px]]

Models:
* Normal channel
* Vibrato channel

[[Cabinet models list | Cab:]] Fender 2x10

Vibrato channel: Volume, Bright switch, Treble, Bass, Tremolo controls

Power tubes: 6L6

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-tremolo-lux-fender-blackface-tremolux-aa763.115354/ Yek's write-up]

==TRIPLE CREST 2 (MESA Triple Crown TC-100)==

[[file:triplecrown.jpg|300px]]

Models:
* Low gain channel
* High gain channel

Gain, Treble, Mid, Bass, Normal / Tight switch, Presence, Reverb (not modeled), Master, attenuator (not modeled)

Power tubes: EL34

# “The actual amp’s “Tight” switch engages a built-in Tube Screamer circuit which can be replicated using a Drive block or the Amp block’s internal Boost feature.” [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-04.159140/post-1901363]
# "The clean channel is like every other Mesa clean channel: a Blackface Fender copy." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-05.159156/post-1901965]
# "The clean channel uses the same built-in tube screamer as the other channels. There's a single fixed tube screamer circuit at the input of the amp. It can be switched in via relays which are controlled by the channel switches." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-05.159156/post-1904010]
# "A Mesa Triple Crown has a built-in Tube Screamer set clean on the input." [https://www.thegearpage.net/board/index.php?threads/looks-like-fractal-devices-are-getting-a-new-modeling-update-cygnus.2224849/post-32213988]
# "The Triple Crest models are based off a Mesa Triple Crown which is "derived from" a Fender Tonemaster." [https://forum.fractalaudio.com/threads/triple-crown-info.174892/post-2121012]

==TRIPLE CREST 3==

==TUBE PRE (generic tube preamp model)==

[[file:Logo small.png]]

Custom Fractal Audio model of a generic tube preamp

Power tubes: 5881 (power amp disabled)

# "The Vintage tone stack is a passive EQ model but it has a flat response when the controls are at noon. If you want "active" EQ you need to set the type to Active." [https://forum.fractalaudio.com/threads/is-it-possible-to-bypass-the-preamp.70487/page-2#post-865226]
# "If you only need power amp modeling, for example when using an external pre-amp through the Axe-Fx, use the Tube Pre model. It uses the Vintage tonestack which is flat when the tone controls are at noon."
# "The "Vintage" tone stack is flat. The Tube Pre model uses the Vintage tone stack." [https://forum.fractalaudio.com/threads/is-it-possible-to-bypass-the-preamp.70487/#post-865192]
# (firmware Ares 14.00) "The Tube Pre model has been changed so that the power amp is off by default."

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-tube-pre.115357/ Yek's write-up]

==TWO STONE J35 (Two-Rock Jet 35)==

[[file:jet35.jpg‎|300px]]

Models:
* Lead mode, Preamp Bypass (PAB) OFF
* Lead mode, Preamp Bypass ON (tone controls bypassed)

[[Cabinet models list | Cab:]] Two Stone 2x12 (G12-65)

Treble, Mid, Bass, Gain, Master, Lead Gain, Pull Bright. No Presence on the original amp, but the model has a Presence control

Power tubes: 6L6

# "It's very smooth but there's this unique chirp or something that I've never heard in an amp before. When you hit the note there's this blast of high end that rapidly decays so it has an almost vocal quality. The frequency shaping is very different than most other amps." [https://forum.fractalaudio.com/posts/745084]
# "The Two Rock is the most unique amp I've ever modeled. Almost like a violin but with this really cool chirp on the pick attack." [https://forum.fractalaudio.com/posts/747921]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-two-stone-j35-two-rock-jet-35.115377/ Yek's write-up]

==TWO STONE J35 PAB==

==USA BASS 400 1 (MESA Bass 400 bass amp)==

[[file:mesabass400.jpg|300px]]

Models:
* Bass Shift OFF
* Bass Shift ON

[[Cabinet models list | Cab:]] Mesa bass speaker cabinet

Bass, Middle, Treble, Pull Bright, Bass Shift, Treble Shift (not modeled), 7-band GEQ, Master, Volume

Power tubes: 6550

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-usa-bass-400-mesa-bass-400.115439/ Yek's write-up]

==USA BASS 400 2==

==USA MK IIC+ (MESA/Boogie Mark IIC+)==

[[file:iic+.jpg|300px]]

IIC+ models:
* Lead Master with Pull Bright engaged
* Lead Master with Pull Bright off
* Lead Master with Pull Deep engaged
* Lead Master with Pull Deep off

[[Cabinet models list | Cab:]] Mesa 1x12 (C90, EVM)

Volume (pull: Bright), Treble (pull: Shift = Fat), Bass (pull: Shift, not modeled), Middle, Presence, Master rhythm (pull: Deep), Lead Drive and Master Lead (pull: Bright)

Power tubes: 6L6

# "The mode in the Mark V is based on the later SimulClass version." [https://forum.fractalaudio.com/posts/910018]
# "If you want the sound of the non-SimulClass version set Triode 1 Plate Freq to 1350 Hz." [https://forum.fractalaudio.com/posts/910386]
# "The Pull Bright on the Volume knob is the classic "Bright Cap" which engages a capacitor across the potentiometer. This is already modeled in the Axe-Fx via the Bright Switch. The Pull Bright on the Lead Master knob engages a 0.22uF cap on the cathode of the last triode in the overdrive circuit. As there is no switch for this in the Axe-Fx it requires a separate model. Cathode caps are very common in tube amps. If the value is large the stage has more gain and the response is relatively flat. If the value is small the stage has more gain at higher frequencies. Amp designers use cathode caps to shape the frequency response. Caps in the range of 0.1 to 1.0 uF are commonly used to reduce bass response. A cathode cap works by decreasing the amount of negative feedback through shunting higher frequencies to ground. This reduced negative feedback increases the gain (and reduces linearity). FWIW the Axe-Fx is the only modeler of which I'm aware that actually models triodes using a feedback technique. Other modelers use static waveshapers. The Axe-Fx triode models incorporate feedback so if there is a virtual cathode cap the stage is less linear in addition to having more gain." [https://forum.fractalaudio.com/posts/1186462]
# "The IIC+ does not have a gain boost and doesn't need one. There is plenty of gain. The Pull Deep switch engages a large cathode cap on the final triode stage. With Pull Deep off there is actually a shelving response into the power amp (bass is reduced)."
# (to emulate Pull Shift on the Bass) "Put a Tilt EQ before the amp block with a frequency of 320 Hz and a gain of -3 dB. Set the Level to +3 dB." [https://forum.fractalaudio.com/posts/1202633]
# "I have a Mark IIC+, a Mark IV, a Mark V and a Triaxis. They're all completely different. Mesa always says things like "sounds the same as a IIC+" but the circuits are different and, probably most important, the knob tapers are completely different." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-2-00-public-beta-numero-tres.109852/page-6#post-1315609]
# "The key to a good Boogie sound, IMO, is the Fat Switch. This is the treble Pull Shift on the IIC+ and the Pull Fat on the Mark IV. Mesa knew this and the Lead 2 modes on the Triaxis all had the treble shift engaged by default."
# "I always used the Fat switch with the real amp." (IIC+) [http://forum.fractalaudio.com/threads/mark-iic-amp-model-issues.121463/page-2#post-1446683]
# "On a Mark IV (at least on our reference amp) all three controls have a Log10A taper. On a Mark V the tapers are different so you get more midrange and treble for the same settings. Channel 3 on a Mark V is virtually identical to the Mark IV Lead channel except for the pot tapers." [https://forum.fractalaudio.com/threads/question-about-the-mark-series-graphic-eq-modeling.149223/post-1771767]
# "The IIC++ amp model is the same as the IIC+ with different tapers." [https://forum.fractalaudio.com/threads/question-about-the-mark-series-graphic-eq-modeling.149223/post-1770773]
# "The tone stack on a Boogie is pre-distortion. As you increase gain you want less bass into the distortion stages so the idea is you turn the bass down. In later versions of the Boogies (TriAxis for example) they changed the taper so that noon was equivalent to 1 on earlier models because people are reticent to move controls very far from noon for some weird reason." [https://forum.fractalaudio.com/threads/highly-compressed-sound-on-high-gain-amps.169132/post-2032825]
# "I begrudgingly dragged the amp out of storage today (as it weighs a metric ton) and repeated the measurements and did some A/B tests. As expected the models are extremely accurate. That being said it is a bear to dial in. Here are some tips:
#* The old version of the model incorrectly referenced the Mark IV tone stack. These tone stacks are identical except for the taper of the mid pot. The IIC+ has a linear pot and the Mark IV has a Log10 pot. I had it backwards in my earlier comments. My guess is that Mesa found that turning the midrange down sounds best (and it does) so they changed the pot taper to do this automatically since noon on a Log10 pot is equal to a 1.0 on a linear pot.
#* Commensurate with (1) I found myself turning the midrange down as well as the bass and turning the treble up.
#* I think the default Master Volume value is a bit high so you may want to turn that down. I've reduced the default for Quantum 2.03.
#* Turn the bright switch on. Every bit of information I've found says that people typically used the Pull Bright on the Volume knob. This is equivalent to the Bright switch under the Treble control on the model. I always turn it on and I've set it on by default for Q2.03.
#* USE THE EQ. The tone stack is pre-distortion which is atypical for a high-gain amp. Tone stacks are almost always post-distortion. Since the tone stack is pre-distortion you need to do your post distortion tone shaping using the EQ. The tone controls set the feel and the distortion texture, the EQ shapes the final tone. I like to do a gentle V-curve.
#* These were my settings for a killer high-gain tone: Model: USA IIC+ / Input Drive: 8.1 / Overdrive: 9-10 / Bass: 1.0 / Midrange: 1.8 / Treble: 8.9 / Presence: 4.5 / MV: 4.0 / Level: -20 dB / Bright Switch ON / 80 Hz: 4.8 / 240 Hz: 2.6 / 750 Hz: -4.5 / 2200: -0.2 / 6600: 0." [http://forum.fractalaudio.com/threads/mark-iic-tips.112378]
# "Treble Shift on the Tone page of USA IIC+ models is an alias of the “Fat” control found on the Preamp page and performs the same function." (firmware 22)

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-usa-iic-mesa-boogie-mark-iic.115442/ Yek's write-up]

==USA MK IIC+ BRIGHT==

==USA MK IIC+ DEEP==

==USA MK IIC+ DEEP BRIGHT==

==USA MK IIC++ (custom model of MESA/Boogie IIC+)==

[[File:Logo small.png]]

Formerly: METALLICA USA IIC++

This is not a model of Hetfield's own "crunchberries" amp, nor a model of a IIC+ with the IIC++ mod. It's the IIC+ model with different tapers. This was requested by Metallica's engineers after the main IIC+ models were updated, and it's part of Metallica's live sound.

Notes: see USA IIC+

# (from Metallica engineers) "This model is part of our live sound. This amp was removed when the new MKII models were added and firmware updated. I asked if it could be ported for Q3 as I was having a difficult time migrating to the updated firmware and retaining our earlier work." [https://forum.fractalaudio.com/threads/metallica-amp.115857/page-2#post-1384750]
# "The IIC++ amp model is the same as the IIC+ with different tapers." [https://forum.fractalaudio.com/threads/question-about-the-mark-series-graphic-eq-modeling.149223/post-1770773]

==USA JP IIC+ Green (MESA/Boogie JP-2C)==

[[File:Jp2c.jpg|300px]]

JP-2C models:
* Green: channel 1
* Red: channel 3
* Red: channel 3, Shred mode
* Yellow: channel 2
* Yellow: channel 2, Shred mode

Channel 1 (Mark IIC+ Clean): Gain, Master, Presence, Treble, Mid, Bass, Mid/Boost switch, graphic EQ, reverb (not modeled)

Channel 2 (Mark IIC+ Gain/Shred): (Pull) Gain, Master, (Pull) Presence, Treble, Mid, Bass, graphic EQ (not modeled), Shred mode switch

Channel 3 (Mark IIC+ Gain/Shred): (Pull) Gain, Master, (Pull) Presence, Treble, Mid, Bass, graphic EQ (not modeled), Shred mode switch

Power tubes: 6L6

# "The JP amp has a fixed input gain control. The "Gain" control on the amp is actually an Overdrive control. If you use Authentic controls there is no Input Gain on "Gain"." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-03.149363/page-3#post-1772020]
# "Presence Shift is Presence pull. Tone stack effectively has fat switch on." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-05.149428/page-10#post-1775746]
# (difference between the "JP Green" and "USA Clean") "JP has less gain and a much larger midrange potentiometer." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-06.149775/page-2#post-1777979]
# "JP himself gave the models his stamp of approval." [http://forum.fractalaudio.com/threads/i-am-confused-about-the-jp2c.153540/post-1826396]
# "JP (Green) has less gain (than USA Clean) and a much larger midrange potentiometer." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-06.149775/post-1777979]
# "Those are great amps. The particular amp used for the models was John Petrucci's personal recording amp. I didn't want to give it back and offered to buy it from him but he wouldn't sell it." [https://www.thegearpage.net/board/index.php?threads/fractal-fm3-reviews-tones-questions.2124913/post-31011638]
# "It's not that the Graphic EQ isn't the same, the TAPERS are not the same. On the real amp the controls do virtually nothing until you get near the ends of the range. If you move a slider to, say, 3/4 of its range it does almost nothing. If you were to set the model's slider to the same position you would get significantly more boost. I didn't model the nonlinear slider behavior because IMO it's a design flaw. Graphic EQs should have a nice, linear-in-dB response. Otherwise the graphic EQ is very accurate. The frequency and Q behavior is spot-on. If you have pulled the presence knob on the amp you have to activate the Presence Shift on the model. Otherwise they will sound VERY different. Presence shift gives a much more focused sound. I always use the Presence Shift. You can't compare the amp with a switch engaged to the model without the equivalent switch engaged. Of course it will sound different. The tapers of the other controls should be very close including the Presence and Master Volume. (...) JP himself was very impressed with the model and the model was matched to his PERSONAL head that he sent me." [https://forum.fractalaudio.com/threads/real-jp2c-vs-axe-fx-3-sim-comparison.168942/post-2029916]</blockquote>
# "I thought that Shred mode is the same as the Red mode on the Triaxis which is just a treble boost on the output when, in fact, it's a clean boost on the input similar to a Tube Screamer but without the treble rolloff." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486/post-2067465]
# (about the fixed internal gain) "Yellow is 2.9. Red is 5.7." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486/post-2067603]
# "JP2C doesn't have a depth knob. If a knob isn't present in the Authentic menu then it may not do anything in the Ideal menu." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-16-01-beta-1-public-beta.172736/post-2088439]
# "USA JP models have a fixed Input Drive so when switching to the models the Input Drive is reset to the default value. The Input Drive knob is not visible in the Authentic menu." [https://forum.fractalaudio.com/threads/bug-presence-not-working-at-the-usa-lead-models-triaxis-16-1-b.172777/post-2088655]
# "A JP IIC+ is not a Mark IV. They sound different. The biggest difference is in the behavior of the Presence Shift. With the Presence Shift on the JP IIC+ will be very similar to the Mark IV with its Presence Shift on. With the Presence Shifts off they are very different sounding." [https://forum.fractalaudio.com/threads/jp-ii-c-red-sounds-muffled-compared-to-mk-iv-mid-gain-in-fw-21-00-with-audio-and-preset.191858/post-2385695]
# "All these amps have the same basic circuit with minor differences. The only unique thing I've encountered in all my tests is the function of the Presence Shift pull on the JP2C. It's different than the pull shift on the other Mark amps." [https://forum.fractalaudio.com/threads/mesa-mark-iic-mark-iic-mark-vii-the-jp2c-mark-iic.192824/post-2398526]

==USA JP IIC+ Red==

==USA JP IIC+ Red Shred==

==USA JP IIC+ Yellow==

==USA JP IIC+ Yellow Shred==

==USA MK IV LEAD / RHYTHM (MESA/Boogie Mark IV)==

[[file:markiv.jpg|300px]]

Mark IV models:
* Rhythm 1 channel (previously: USA Clean model)
* Rhythm 2 channel
* Lead channel, Voicing: Harmonics, Pull Bright: engaged
* Lead channel, Voicing: Mid Gain, Pull Bright: engaged
* Lead channel, Voicing: Harmonics, Pull Bright: off
* Lead channel, Voicing: Mid Gain, Pull Bright: off

[[Cabinet models list | Cab:]] Mesa 1x12 (C90, V30)

Gain, Lead Drive, Treble, Bass, Mid, Presence, Master, graphic EQ, Pentode/Triode switch, Class-A/Simul-Class switch, Voicing switch (Mid Gain / Harmonics), Variac

Rhythm 1 channel: Pull Bright

Rhythm 2 channel: Pull Fat, Presence Shift

Lead channel: Pull Bright, Pull Fat, Presence Shift

Power tubes: 6L6

# "The MK V is basically a compendium of previous Mesa amps. There may be minor differences in tone due to circuit layout but nothing a few tweaks to the EQ can't fix." [https://forum.fractalaudio.com/posts/573437]
# “A Mark V is a greatest hits of the Mark IV and IIC+. You already have all those models.” [https://forum.fractalaudio.com/threads/wish-list-new-amps.137944/post-1991426]
# "Having owned multiple Mark IV's, multiple Triaxis's and a variety of other Boogie products, I can tell that the Mark series in general are a bitch to dial in. Once you figure them out though they are great amps. IMO, the key to a MKIV is to use the TMB to get the feel and the EQ to get the tone."
# "If it isn't Mid Gain then it's Harmonics." [https://forum.fractalaudio.com/posts/1165578]
# "The Depth knob is inactive on that amp model. The real amp doesn't have one either." [https://forum.fractalaudio.com/posts/1205835]
# "Fat and Presence shift work as the real amp." [https://forum.fractalaudio.com/posts/1246666]
# "USA Clean is based on the MKIV." [http://forum.fractalaudio.com/threads/mesa-iic-clean-channel.106851/#post-1280186]
# "With the presence control at noon it's roughly neutral. Turn it down and you are actually boosting bass and reducing treble." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-1-03-firmware-release.106931/page-12#post-1282192]
# "I have a Mark IIC+, a Mark IV, a Mark V and a Triaxis. They're all completely different. Mesa always says things like "sounds the same as a IIC+" but the circuits are different and, probably most important, the knob tapers are completely different." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-2-00-public-beta-numero-tres.109852/page-6#post-1315609]
# "The key to a good Boogie sound, IMO, is the Fat Switch. This is the treble Pull Shift on the IIC+ and the Pull Fat on the Mark IV. Mesa knew this and the Lead 2 modes on the Triaxis all had the treble shift engaged by default."
# "There isn't any way to run the virtual power tubes in triode mode... but you can change the Power Tube Type to "300B" which is a triode. When you run a pentode (or beam tetrode) in triode mode you connect the screen to the anode which effectively defeats the screen. This lowers the output impedance of the plate significantly which, in turn, lowers the output impedance of the amp itself making the voltage output less dependent on the speaker impedance. Using the 300B tube type should get you pretty close." [http://forum.fractalaudio.com/threads/mesa-mark-iv-pentode-triode-switch.122527/#post-1458293]
# (about the GEQ) "The range of the sliders is the same as the amp. The taper is not. The amp is much more abrupt since it uses linear taper (should use 'S'-taper)." [https://forum.fractalaudio.com/threads/question-about-the-mark-series-graphic-eq-modeling.149223/post-1769764]
# (about the difference between the "JP Green" and "USA Clean") "JP has less gain and a much larger midrange potentiometer." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-06.149775/page-2#post-1777979]
# (simulate Class-A mode) "Turn Power Tube Grid Bias all the way up." [https://forum.fractalaudio.com/threads/mesa-mk-4-class-a-possible.154438/post-1836241]
# "The tone stack on a Boogie is pre-distortion. As you increase gain you want less bass into the distortion stages so the idea is you turn the bass down. In later versions of the Boogies (TriAxis for example) they changed the taper so that noon was equivalent to 1 on earlier models because people are reticent to move controls very far from noon for some weird reason." [https://forum.fractalaudio.com/threads/highly-compressed-sound-on-high-gain-amps.169132/post-2032825]
# "A JP IIC+ is not a Mark IV. They sound different. The biggest difference is in the behavior of the Presence Shift. With the Presence Shift on the JP IIC+ will be very similar to the Mark IV with its Presence Shift on. With the Presence Shifts off they are very different sounding." [https://forum.fractalaudio.com/threads/jp-ii-c-red-sounds-muffled-compared-to-mk-iv-mid-gain-in-fw-21-00-with-audio-and-preset.191858/post-2385695]
# "Mark V is the same thing as a Mark IV w/ a few extra features. They sound virtually identical." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-02.191637/post-2382608]
# "The amp uses linear taper sliders. The ideal taper for this type of circuit is S-taper. S-taper will give you approximately linear-in-dB. The Axe-Fx III is precisely linear-in-dB." [https://forum.fractalaudio.com/threads/mark-series-eq.191595/post-2389621]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-usa-clean-lead-rhythm-mesa-boogie-mark-iv.115440/ Yek's write-up]

==USA MK IV LEAD BRIGHT==

==USA MK IV LEAD MID GAIN==

==USA MK IV LEAD MID GAIN BRIGHT==

==USA MK V GREEN (MESA/Boogie Mark V)==

==USA PRE CLEAN (MESA TriAxis preamp)==

[[file:triaxis.png|300px]]

Triaxis models:
* Rhythm Green
* Lead 1 Red (TX-4 board)
* Lead 2 Green
* Lead 2 Red
* Lead 2 Yellow

Drive, Lead Drive, Treble, Middle, Bass, Presence (preamp, on Lead 2 models), Dynamic Voice EQ (not modeled)

Power tubes: same as USA Lead model (6L6)

# "I used a Triaxis for, shoot, I dunno, over a decade before designing the Axe-Fx. I have two of them. So I'd say I'm pretty familiar with the tones. To my ears (and my measurement equipment), the Axe-Fx models are spot-on."
# "I can nail the sound of my Triaxis now by setting it (Bright) around 9:00 - 10:00." [https://forum.fractalaudio.com/posts/1001906] And: "10 on the Triaxis would be 0 dB on the Bright parameter. Anything below 10 is equivalent to less than noon on the Bright parameter. The "Presence" control on a Triaxis is always a hi cut, it never boosts. The Bright parameter is not an exact match to the Triaxis Presence control though. It is a fixed shelving filter. The Triaxis Presence control is passive so the center frequency changes with the amount of cut. It also changes the load on the plate which distorts the frequency response a bit too. The Presence parameter should be set to 5.00, which is neutral (see the manual for details)."
# "I have a Mark IIC+, a Mark IV, a Mark V and a Triaxis. They're all completely different. Mesa always says things like "sounds the same as a IIC+" but the circuits are different and, probably most important, the knob tapers are completely different." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-2-00-public-beta-numero-tres.109852/page-6#post-1315609]
# "The key to a good Boogie sound, IMO, is the Fat Switch. This is the treble Pull Shift on the IIC+ and the Pull Fat on the Mark IV. Mesa knew this and the Lead 2 modes on the Triaxis all had the treble shift engaged by default."
# "Mesa claims it's based on the IIC+ but it's different. The bright cap is different, the mid resistor is much greater, the source impedance of the drive "pot" is different, etc., etc, etc." [http://forum.fractalaudio.com/threads/three-hours-with-the-usa-pre-ld2-yellow.111624/#post-1335224]
# (firmware Quantum 7) "The USA Pre models now all use a MarkIV power amp model. The 2:90 power amp is basically the same as a MarkIV and does have a presence shift but it's accessed through a jack on the back (Voicing)." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-00-firmware-release.124944/page-15#post-1487194]
# "I gigged with a Triaxis for years. I never put Dynamic Voice above 1.0. Despite it's name, DV is just an EQ. It's the 5-band graphic EQ from the mark series with the potentiometers replaced by LDRs. It's really just a bunch of EQ presets and it interpolates between them as you increase the value." [http://forum.fractalaudio.com/threads/triaxis-model-live-use.147163/#post-1740122]
# "I have two of them. Both with the Lead 1 Red board." [https://forum.fractalaudio.com/threads/the-triaxis-is-spot-on.151673/post-1804830]
# "On our reference Triaxis (both of them) the Presence control doesn't do anything for the Clean and LD1 modes. The model's Presence knob is therefore the Power Amp Presence." [https://forum.fractalaudio.com/threads/triaxis-usa-pre-models-inconsistencies-in-controls.156431/post-1862912]
# "That's how our reference amps work. They are the later models with the TX4 board (different LD2 Red). When using the LD1 modes the Presence control doesn't do anything and is as if the control were at 10." [https://forum.fractalaudio.com/threads/triaxis-usa-pre-models-inconsistencies-in-controls.156431/post-1865080]
# "The tone stack on a Boogie is pre-distortion. As you increase gain you want less bass into the distortion stages so the idea is you turn the bass down. In later versions of the Boogies (TriAxis for example) they changed the taper so that noon was equivalent to 1 on earlier models because people are reticent to move controls very far from noon for some weird reason." [https://forum.fractalaudio.com/threads/highly-compressed-sound-on-high-gain-amps.169132/post-2032825]
# "Based on the Lead 1 Red mode of a Mesa Triaxis preamp with the TX-4 board."
# In "Cygnus" amp modeling firmware the Lead models have an authentic Preamp Presence control (not in the Lead 1 model).
# "I gigged a Triaxis for years and I would have the knobs pretty much at noon (5.0). The Triaxis is a Mark IV preamp under the hood but with very different tapers on the "pots". I.e., with BMT at 5.0 on the Triaxis the MKIV would be something like 1.0, 6.0, 6.0. I'm just going by memory here but the point being that the bass control on the Triaxis doesn't need to be turned way down like you would on a Mark series." [https://forum.fractalaudio.com/threads/bad-experience-with-choptones-i-need-a-2nd-opinion-watch-screenshots-plz.191948/post-2386734]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-usa-pre3-mesa-boogie-triaxis.115478/ Yek's write-up]

==USA PRE LD1 RED==

==USA PRE LD2 GREEN==

==USA PRE LD2 RED==

==USA PRE LD2 YELLOW==

==USA MK IV RHYTHM 1==

==USA MK IV RHYTHM 2==

==USA SUB BLUES (MESA Subway Blues)==

[[file:subwayblues.png|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Mesa 1x10 (Eminence Black Shadow), DynaCab available

Volume, Bass, Mid, Treble, FAT switch, Reverb (not modeled)

Power tubes: EL84

# "The Subway Blues model was completely redone. It will likely sound different than before." [https://forum.fractalaudio.com/threads/bug-mesa-subway-blues-very-different-in-ares-15-01-vs-cygnus-16-00.172363/post-2082472]
# "The reference amp is the later, single input version. The Fat switch replicates the amp's Fat switch." [https://forum.fractalaudio.com/threads/bug-mesa-subway-blues-very-different-in-ares-15-01-vs-cygnus-16-00.172363/post-2088907]

[http://forum.fractalaudio.com/threads/usa-sub-blues-mesa-boogie-subway-blues.115479/ Yek's write-up]

==VIBRA-KING (custom Fender Vibro-King)==

[[file:vibro-king.jpg|300px]]

Models:
* Fat switch ON
* Fat switch OFF

Volume, Treble, Bass, Middle, Fat switch, Tremolo, Reverb (not modeled)

[[Cabinet models list | Cab:]] Fender 3x10

Power tubes: 6L6

# "The model is based on the custom version which has higher plate voltages which causes more overdrive on the power tubes."

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-vibra-king-custom-fender-vibro-king.115485/ Yek's write-up]

==VIBRA-KING FAT==

==VIBRATO LUX (1962/1963 brownface Fender Vibrolux, 6G11)==

[[file:vibrolux.jpg|300px]]

Model:
* Bright channel (Normal channel: Bright OFF)

[[Cabinet models list | Cab:]] Fender 2x10 or 1x12

Vibrato channel: Volume, Bass, Treble, Vibrato (not modeled)

Power tubes: 6L6

# "Early Dire Straits tone is a Vibrolux (Vibrato Lux model). The Vibrato Lux model is based on the same model and year amp used on the eponymous album. There's a cab in there too." [https://forum.fractalaudio.com/posts/1111550]
# "It's a Vibrolux. That IR is from my personal 1962 Vibrolux. This is the amp used on Dire Straits eponymous album." [https://forum.fractalaudio.com/threads/vibrolux-g3-with-the-new-ir-is-just-ridiculous.97866/#post-1174387]
# "It's a Brownface." [https://forum.fractalaudio.com/threads/brownface-deluxe-or-closest-thing-to-it.80014/#post-973252]
# "Our reference amp is the same model Mark Knopfler used on the Dire Straits eponymous album. Match made in heaven with a Strat." [https://forum.fractalaudio.com/threads/definitely-a-problem.173700/post-2103923]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-vibrato-lux-fender-vibrolux-6g11.115713/ Yek's write-up]

==VIBRATO VERB (Fender Vibroverb)==

[[image:vibroverb.jpg|300px]]

Vibroverb models:
* Vibrato Verb: old model ported from the Axe-Fx Ultra
* Vibrato Verb AA: based on Cliff’s own 1964 blackface Vibroverb with AA763 circuit
* Vibrato Verb AB: based on AB763 circuit
* Vibrato Verb Custom: based on Custom Reissue

[[Cabinet models list | Cab:]] Fender 1x15 (Jensen C15N, JBL D130, Eminence)

Volume, Bass, Treble, Bright switch, Reverb (not modeled), Tremolo

Power tubes: 6L6

# "The Transformer Matching value for the CS model is based on the output transformer in the actual amp. Legend has it that SRV used a Bassman transformer which would lead to significant overmatching. To replicate this increase Xfrmr Match to around 1.8."
# "Some different component values in the AA vs. AB." [https://forum.fractalaudio.com/threads/vibrato-verb-models-explained.192318/post-2391593]
# "The 1x15 Vibroverb is a D130." [https://forum.fractalaudio.com/threads/what-dyna-cab-models-would-you-like-to-see-added.193380/post-2404043]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-vibrato-verb-fender-vibroverb.115734/ Yek's write-up]

==VIBRATO VERB AA (1964 blackface Fender Vibroverb, AA763)==

==VIBRATO VERB AB (Fender Vibroverb, AB763)==

==VIBRATO VERB CUSTOM (Fender Vibroverb Custom Reissue)==

==WRECKER EXPRESS (Trainwreck Express)==

[[file:trainwreck.jpg|300px]]

Models:
* Wrecker Express: Bright switch on original amp in center or top position
* Wrecker Express Bright: Bright switch on original amp in bottom (brightest) position

[[Cabinet models list | Cab:]] Marshall 4x12 (G12-M25)

Power tubes: EL34

Volume, Bass, Mid, Treble, Presence, three-position Bright switch (center: off, top: clarity and sparkle, bottom: jangly highs)

# "The secret to a Trainwreck is the output transformer. The impedance ratio is about twice that of other amps. I.e. typical 50W Marshall has a primary impedance of about 3200 ohms. A Trainwreck is about 6500 ohms. The causes the power tubes to clip much sooner." [https://forum.fractalaudio.com/posts/1116254]
# "Real Trainwrecks are very spitty amps. This is because the last stage heavily overdrives the phase inverter. 7.02 is faithful to the actual amps whereas previous firmwares were more idealized. As was indicated in the release notes you can dial out this behavior by decreasing the PI Bias Shift. If you set it to zero it will be like 6.xx." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-02-firmware-release.125625/page-17#post-1498318]
# [https://forum.fractalaudio.com/threads/trainwreck-express-tweaks.154796/post-1841547 Cliff's Tech Note]: "A real Trainwreck Express is a fizzy, spitty amp. Some people like this. The same people who like fuzz pedals and that quasi-half-wave rectified sound. Personally I like more clarity. The reason the Express is like this is primarily due to the last triode stage before the phase inverter (PI). This stage is biased very cold and drives the PI very hard due to the lack of any limiting resistor (grid stopper) between the triode and PI. The lack of a grid stopper resistor and large coupling capacitor create significant bias excursion (blocking distortion). It appears the designer attempted to minimize the bias excursion by biasing the triode cold which limits its positive excursion and therefore limits the PI grid conduction. Despite the cold bias point the PI grid is still heavily overdriven resulting in massive blocking distortion. The Axe-Fx allows you to reduce the amount of block distortion via the PI Bias Excursion parameter. Simply turn this down and the spittiness will go away. You can then also rebias the triode via the Preamp Bias parameter. Values closer to zero result in a more symmetric waveform." (...) "Turn PI Bias Excursion to 0. Set Preamp Bias to -0.15 or so. [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841487]"
# "The reason they clean up when you back off the volume is because the OT is so overmatched. It's about twice the optimum value." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841485]
# "The real amp is a nasty thing. Very spitty as one would expect given the lack of a grid stopper resistor between the last triode stage and the PI." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841549]
# "Got out the reference amp and it sounds the same. For all the hoopla surrounding Trainwrecks they're actually pretty bad designs. Tons of blocking distortion in the PI. If you don't want all that blocking distortion turn down PI Bias Excursion." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/page-4#post-1841474]
# "Turning down PI Bias Excursion yields the ultimate Trainwreck. Sounds much better than the real amp. I also adjusted the Preamp Bias so it wasn't so off-center." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/page-4#post-1841480]
# "The only difference (between the two Express models) is the Bright Cap. An Express (at least mine) has a three-position switch: Off, 100 pF, 500 pF. The amp block only supports Off and On and I figured people wouldn't know the fine details so a separate model seemed the easiest solution. Of course you can vary the Bright Cap but you'd have to know that the real amp has two caps, etc." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-10-01.154923/post-1843572]
# "That amp exhibits a lot of blocking distortion (in the phase inverter) due to its design. You can reduce this via either the PI Bias Excursion or Master Bias Excursion parameters. Another option is to use the FAS Express model which puts some resistors between the last triode stage and the PI to reduce the bias excursion." [https://forum.fractalaudio.com/threads/blocking-distortion-found-in-trainwreck-express.182895/post-2247268]
# "I got out my Trainwreck Express and compared it to the model last night and it's spot-on. Nasty, spitty, Neil Young-esque blocking distortion and all." [https://forum.fractalaudio.com/threads/blocking-distortion-found-in-trainwreck-express.182895/post-2247538]
# "That's what amps do. You don't hear it through a guitar cab typically but using close-mic'd IRs it's more noticeable. You can reduce it by turning on the Plate Suppressor diodes. Trainwrecks have plate suppressor diodes for just this reason." [https://forum.fractalaudio.com/threads/note-decay-crackle-sizzle-noise.193575/post-2407689]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-wrecker-express-trainwreck-express.115740/ Yek's write-up]

==WRECKER EXPRESS BRIGHT==

==WRECKER LIVERPOOL (Trainwreck Liverpool)==

[[file:trainwreck.jpg|300px]]

Models:
* Liverpool: Bright switch on original amp in center or top position
* Liverpool Bright: Bright switch on original amp in bottom (brightest) position

[[Cabinet models list | Cab:]] Marshall 4x12 (G12-M25)

Volume, Bass, Mid, Treble, Presence, three-position Bright switch (center: off, top: clarity and sparkle, bottom: jangly highs)

Power tubes: EL84

# "The secret to a Trainwreck is the output transformer. The impedance ratio is about twice that of other amps. I.e. typical 50W Marshall has a primary impedance of about 3200 ohms. A Trainwreck is about 6500 ohms. The causes the power tubes to clip much sooner." [https://forum.fractalaudio.com/posts/1116254]
# "Just because a power amp is "Class A" doesn't mean it can't have negative feedback. True that the majority do not but this particular amp has quite a bit of NF." [http://forum.fractalaudio.com/threads/wrecker-liverpool-neg-feedback-bug.116224/#post-1389082]
# "Uses a Vox-style phase inverter." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-00-public-beta.123082/page-7#post-1464730]
# "Real Trainwrecks are very spitty amps. This is because the last stage heavily overdrives the phase inverter. 7.02 is faithful to the actual amps whereas previous firmwares were more idealized. As was indicated in the release notes you can dial out this behavior by decreasing the PI Bias Shift. If you set it to zero it will be like 6.xx." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-02-firmware-release.125625/page-17#post-1498318]
# [https://forum.fractalaudio.com/threads/trainwreck-express-tweaks.154796/post-1841547 Cliff's Tech Note]: "A real Trainwreck Express is a fizzy, spitty amp. Some people like this. The same people who like fuzz pedals and that quasi-half-wave rectified sound. Personally I like more clarity. The reason the Express is like this is primarily due to the last triode stage before the phase inverter (PI). This stage is biased very cold and drives the PI very hard due to the lack of any limiting resistor (grid stopper) between the triode and PI. The lack of a grid stopper resistor and large coupling capacitor create significant bias excursion (blocking distortion). It appears the designer attempted to minimize the bias excursion by biasing the triode cold which limits its positive excursion and therefore limits the PI grid conduction. Despite the cold bias point the PI grid is still heavily overdriven resulting in massive blocking distortion. The Axe-Fx allows you to reduce the amount of block distortion via the PI Bias Excursion parameter. Simply turn this down and the spittiness will go away. You can then also rebias the triode via the Preamp Bias parameter. Values closer to zero result in a more symmetric waveform." (...) "Turn PI Bias Excursion to 0. Set Preamp Bias to -0.15 or so. [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841487]"
# (about the Tech Note) "Applies to the Liverpool because the preamp is almost identical to the Express." [https://forum.fractalaudio.com/threads/trainwreck-express-tweaks.154796/post-1842967]
# "The reason they clean up when you back off the volume is because the OT is so overmatched. It's about twice the optimum value." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841485]
# "Turning down PI Bias Excursion yields the ultimate Trainwreck. Sounds much better than the real amp. I also adjusted the Preamp Bias so it wasn't so off-center." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/page-4#post-1841480]
# "That's what amps do. You don't hear it through a guitar cab typically but using close-mic'd IRs it's more noticeable. You can reduce it by turning on the Plate Suppressor diodes. Trainwrecks have plate suppressor diodes for just this reason." [https://forum.fractalaudio.com/threads/note-decay-crackle-sizzle-noise.193575/post-2407689]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-wrecker-liverpool-trainwreck-liverpool.115741/ Yek's write-up]

==WRECKER LIVERPOOL BRIGHT==

==WRECKER ROCKET (Trainwreck Rocket)==

[[file:trainwreck.jpg|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Marshall 4x12 (G12-M25)

Volume, Treble, Bass, Cut

Power tubes: EL84

# "The secret to a Trainwreck is the output transformer. The impedance ratio is about twice that of other amps. I.e. typical 50W Marshall has a primary impedance of about 3200 ohms. A Trainwreck is about 6500 ohms. The causes the power tubes to clip much sooner." [https://forum.fractalaudio.com/posts/1116254]
# "The Rocket has a different preamp (than the Express) with the tone stack before the PI. This reduces the signal level substantially and lessens the amount of blocking distortion." [https://forum.fractalaudio.com/threads/trainwreck-express-tweaks.154796/post-1842967]
# "The reason they clean up when you back off the volume is because the OT is so overmatched. It's about twice the optimum value." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841485]
# "Real Trainwrecks are very spitty amps. This is because the last stage heavily overdrives the phase inverter. 7.02 is faithful to the actual amps whereas previous firmwares were more idealized. As was indicated in the release notes you can dial out this behavior by decreasing the PI Bias Shift. If you set it to zero it will be like 6.xx." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-02-firmware-release.125625/page-17#post-1498318]
# "Turning down PI Bias Excursion yields the ultimate Trainwreck. Sounds much better than the real amp. I also adjusted the Preamp Bias so it wasn't so off-center." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/page-4#post-1841480]
# "That's what amps do. You don't hear it through a guitar cab typically but using close-mic'd IRs it's more noticeable. You can reduce it by turning on the Plate Suppressor diodes. Trainwrecks have plate suppressor diodes for just this reason." [https://forum.fractalaudio.com/threads/note-decay-crackle-sizzle-noise.193575/post-2407689]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-wrecker-rocket-trainwreck-rocket.114726/ Yek's write-up]

[[category:Axe-Fx2]]
[[category:Axe-Fx3]]
[[category:FM3]]
[[category:FM9]]
[[category:AX8]]
[[category:Sounds]]
[[category:All]]

Amp block

2023-12-02T14:45:18Z

James-F: /* NEGATIVE FEEDBACK */

__TOC__
[[image:H_amps.png|link=]]
=The Amp block=

==Available on which products==

* '''Axe-Fx III''': 2 blocks
* '''FM3''': 1 block
* '''FM9''': 2 blocks
* '''Axe-Fx II''': 2 blocks
* '''AX8''': 1 block
* '''FX8''': n/a

==Channels or X/Y switching==

* '''Axe-Fx III''' and '''FM3''' and '''FM9''': 4 channels
* '''Axe-Fx II''': X/Y
* '''AX8''': X/Y

=About amp modeling=

[[image:Amp block.PNG|500px]]

==Fractal Audio's amp modelers==

* The Axe-Fx III is the flagship product, offering the most complete feature set.
* The FM9 offers the same amp modeling as the Axe-Fx III.
* The FM3 also provides the same amp modeling, but due to its lesser processing power, some features are not available.

<blockquote>
(FM3 versus Axe-Fx III) "They are the same quality. Certain features were removed to allow the algorithms to run including the bias tremolo, input dynamics processing (...)." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-62#post-28446966]
</blockquote>

<blockquote>
(FM3) "We removed all the superfluous stuff (bias tremolo, dynamic presence/depth, etc.) in order to get the core amp modeling to run on the slower processor." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-68#post-28450968]
</blockquote>

<blockquote>
(FM3) "The Axe-Fx III contains various algorithms that allow you to enhance the amp modeling that don't exist on a real amp. I.e. dynamic presence/depth, input dynamic processing, etc. These were removed to allow the core amp modeling to run on the lower-powered processor." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-70#post-28454394]
</blockquote>

<blockquote>
"We model things that other products simply cannot as it requires more CPU power than available. The Axe-Fx III dedicates an entire 1GHz DSP to just amp modeling. And this DSP is 2-4x more powerful clock for clock than typical DSPs. We even model esoteric things like the bias excursion in the phase inverter. And that's just one thing. There's dozens of other little things like that. Many that I can't talk about because they are secrets." [https://www.thegearpage.net/board/index.php?threads/axe-fx-iii-impression-from-a-long-term-helix-user.2144811/page-9#post-30492007]
</blockquote>

<blockquote>"Some of the amp models in the Axe-Fx III use 85% of the dedicated 1GHz DSP." [https://thegearforum.com/threads/new-headrush-pedalboard-headrush-prime.1817/post-62024]</blockquote>

The same applied to the earlier hardware generations (AX8 vs Axe-Fx II).

==Amplifier and cabinet modeling for beginners==

[[Amp and Cab modeling for beginners]]

==Amp modeling developments==

The [[Firmware_release_notes_-_Axe-Fx_III|Firmware Release Notes]] describe the ongoing development of amp modeling techniques. The amp-specific bits can be found on this page: [[Amp modeling progress]].

While Fractal Audio's processors also provide state-of-the art digital effects, the amp modeling is the flagship feature. Amp modeling is part of the firmware where each generation of Fractal Audio's has a name: G3, Ares, Quantum, Cygnus, Cygnus X-2.

==The Amp models==

All current amp models are listed on the [[Amplifier models list]] page in the wiki.

[[Yeks Guide to the Fractal Audio Amp Models|Yek's Guide to the Fractal Audio Amp Models]] (PDF) provides additional in-depth information.

Most amp models are showcased in the [[Factory presets]].

Fractal Audio owns all the amps on which the models are based, except the Bludotone. [https://thegearforum.com/threads/fractal-audio-firmware-update-thread.673/page-54#post-46151]

<blockquote>"I have close to 100 amps."[https://thegearforum.com/threads/fractal-talk.2745/post-132104]</blockquote>

<blockquote>"I own almost every amp that we've modeled. I have a Dumble, Trainwreck, Ruby Rocket, multiple Carol-Anns, a Mark IIC+, a Mark IV, a Mark V, a JP2C, (2) Triaxis, about a dozen Marshalls, at least a dozen Fenders, etc., etc. I have two BE 100s: an original Purple one made when Dave was just a little shop and a newer one with all the latest changes. We have a room with a pool table. You can't use it because there are amps stacked all around it and then more in the hallway and probably another 20 or so in my office. It's kind of ridiculous." [https://thegearforum.com/threads/fractal-talk.2745/post-132395]</blockquote>

[[image:Book.jpg|link=http://wiki.fractalaudio.com/axefx2/index.php?title=Yeks_Guide_to_the_Fractal_Audio_Amp_Models |150px]]

==Number of Amp blocks==

A preset on Fractal Audio's amp modelers can have one or two Amp blocks, depending on the product.

One of the DSPs on the circuit board of Fractal Audio's amp modelers is devoted to amp modeling. Therefore, adding a second Amp block (if the firmware supports it) increases total CPU usage just a little.

'''Axe-Fx II''' and '''III''' — two Amp blocks

'''FM3''' — one Amp block. The Amp block shares a core DSP with the Delay blocks.

'''FM9''' — two Amp blocks.

'''AX8''' — one Amp block.

Some of the [[Factory presets]] on the Axe-Fx III and FM9 demonstrate the use of two Amp blocks.

<blockquote>(Axe-Fx II) "There is actually a small amount of processing for the amp blocks done on the master DSP. That, along with inter-DSP communications, uses about 2% of the master DSP." [http://forum.fractalaudio.com/threads/ver-5-more-cpu-hungry.46744/page-3#post-610285] </blockquote>

When using a single Amp block in the Axe-Fx II, the Amp block runs at double the internal sampling frequency. This happens automatically; theirs is no parameter. Main benefit of this is less aliasing in high gain models.

Fractal Audio has not officially disclosed whether the sampling frequency still depends on the number of Amp blocks in an Axe-Fx III preset. Research by a forum member indicates that this is still the case.

<blockquote>(Axe-Fx III) "The reason I haven't added a third amp block is that I would have to reduce the oversample rate for all the amp blocks when three are in use and this would be detrimental to sound quality." [http://forum.fractalaudio.com/threads/three-amp-blocks.141345/page-20#post-1757734]</blockquote>

<blockquote>(FM3) "We could potentially do two amp blocks but at reduced quality and I don't want to do that. Part of the problem with other modelers is that they don't oversample enough (and use single-precision in places where you need double-precision). Then you get complaints of artifacts and ear fatigue and all the other things associated with inadequate sample rate and word length. The vast majority of users only use one amp block so we wanted to make something with one very high quality "Ares" amp block." [https://forum.fractalaudio.com/threads/announcing-the-fm3-amp-modeler-fx-processor.149900/page-5#post-1779298]</blockquote>

<blockquote>(Axe-Fx II, firmware 3.04) "In high-res mode the internal sampling rate is doubled so as to provide greater fidelity and resistance to aliasing. This mode is automatic and is selected whenever there is only one amp block in the layout grid. Adding a second amp block will revert to normal resolution. Note that switching between presets with differing number of amp blocks may introduce an additional delay as a “soft reset” of the amp blocks must be done whenever changing the resolution."</blockquote>

<blockquote>(Axe-Fx II) "The oversampling rate is cut in half when running two amps. It's probably not noticeable. Even when running at half, it's as fast or faster than every other product available." [http://forum.fractalaudio.com/threads/use-two-amps-less-quality.57125/#post-716531] </blockquote>

<blockquote>(Axe-Fx II) "I don't hear a difference but some claim they can. A single amp block runs the amp simulation at 16x oversampling. Two amp blocks run each simulation at 8x." [http://forum.fractalaudio.com/threads/v10-test-1-amp-block-hi-res-vs-2-amp-blocks-low-res.67096/#post-826852] </blockquote>

Switching between two Amp blocks in parallel rows, is the fastest way to switch between amp sounds without a gap.

Tips:
* When using a single Amp block in a preset on a processor that supports two Amp blocks, always use the first instance (AMP 1), or you might experience a "pop" when switching to that preset.
* When switching between two Amp blocks in parallel rows, make sure to set their Bypass Mode to Mute, to prevent bleed-through of dry signal from the bypassed Amp block.
* Adding a Drive block in front of only one of two Amp blocks in parallel rows, with both Amp blocks engaged, may cause phase cancellation because of latency. Solution: add a bypassed Drive block to the other row.

When using two Amp blocks, run them in two parallel grid rows. Do not place them in series on the same row.

<blockquote>"Don't put amp blocks in series. Especially when one is clean and the other is high-gain. Always put them in parallel and set the bypass mode to Mute." [http://forum.fractalaudio.com/threads/fw10-pop-when-switching-between-two-scenes-with-a-different-amp.67340/#post-831962] </blockquote>

<blockquote>"NEVER put amps in series. Put them in parallel and set the Bypass Mode to Mute." [https://forum.fractalaudio.com/threads/loud-crash-sound-when-changing-scenes.144050/#post-1704420] </blockquote>

Note that since the introduction of firmware 20 for the Axe-Fx III, this has changed. You can now put two Amp blocks in series.

==Preamp and power amp modeling==

[[image:Amp block.PNG|450px]]

In a real amp, the preamp constitutes the amp's unique tone. The power amp amplifies the weak output signal from the preamp, powers the speaker(s) and further sculpts the amp tone when turning it up.

The virtual preamp and power amp operate the same as their hardware equivalents, but the power amp can't drive physical speakers without the help of a hardware power amp.

The Amp block consists of the virtual preamp and the virtual power amp. Parameters for both are provided.

Power Amp modeling can be disabled (globally or per-preset), but there's no way for the user to separate both sections into separate blocks. This means that you can’t switch between (virtual) power amps for a given amp model.

<blockquote>"It's not impossible but it has implementation difficulties. The main problem is that the amp block is nonlinear and therefore oversamples the data. Any effect inserted between the virtual preamp and power amp would need to also run at the oversampled rate which means many times the CPU usage. For example, if the amp block is running 8x oversampled then the CPU usage for any effect inserted would by 8x as much (I'm not going to disclose our actual oversample rate). The other way is to downsample back to native sample rate, run the effect(s), and the upsample again. No problem right? Except the no-free-lunch theory gets in the way. Downsampling and upsampling add latency." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-2-00-firmware-release.110178/page-15#post-1321907] </blockquote>

If a simulated power amp without preamp is desired, for example when using an external preamp, use the Tube Pre amp model, with its tone controls set at default, and make sure that its power amp is enabled.

<blockquote>"Yes, the Tube Pre model is neutral." [http://forum.fractalaudio.com/threads/is-it-possible-to-bypass-the-preamp.70487/#post-864821] </blockquote>

To create a preamp-only Amp model, turn off Supply Sag in the Amp block (pre-Cygnus firmware) or turn off Power Amp Modeling in the Amp block (Cygnus firmware).

The Tube Pre amp model is a preamp-only model (firmware Ares 14.00 and later).

Depending on the firmware version, the Tube Pre's power amp is on or off at default.

==Authentic or idealized modeling==

When modeling an existing amp, the choice has to be made to create an authentic model, or an idealized model:

<blockquote>"Accuracy, warts and all. Otherwise people compare against the real amp and say "it doesn't sound the same". The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]</blockquote>

<blockquote>"The frequency response is identical to the actual amps modeled. That is part of the modeling process. The models are EQ-matched to the amps and the data stored in the firmware." [http://forum.fractalaudio.com/threads/another-trick-high-pass-low-pass.116016/#post-1386469] </blockquote>

<blockquote>(Axe-Fx II) "Even without matching the modeling is so accurate now that any deviations are less than 1 dB." [http://forum.fractalaudio.com/threads/another-trick-high-pass-low-pass.116016/#post-1386514] </blockquote>

<blockquote>"Depending upon the amp the low frequency response can be highly dependent upon the load. So selecting the right Speaker Impedance Curve becomes important. Dynamic Depth is a non-physical tweak. It uses what I call "Inverse Homomorphic Processing". Anything other than zero is deviating from authentic. It's not wrong to use it but it will be less accurate. The power amp modeling IS current modeling. Power tubes are essentially current sources (with some finite resistance in parallel). Dynamic Depth has nothing to do with this. The other big thing is Master Volume. As you raise the MV the power tubes will saturate on the lows and highs first which causes the tone to have more midrange and vice-versa. Most of the controls in the Axe-Fx match their physical counterparts. The exceptions are Presence and Master Volume. Most amps simply have the wrong taper for their Presence controls. For example a 5150 Presence control does absolutely nothing from 0 to 7. All the action happens in the upper 1/4 of the control's range which is just dumb. The Axe-Fx uses a proper taper which gives a nice, even response over the full range of the control. Likewise the Master Volume on many amps is too abrupt. By 2-3 on the knob the power amp is saturating. Again we use a more rational taper so that you have finer control over power amp distortion. The downside of this approach is that if you put the Presence and Master Volume controls in the same position as the amp it won't sound the same. People do this then post videos and proclaim "See? Modeling isn't accurate!!! Toobz rule brah."" [https://forum.fractalaudio.com/threads/legacy-amp-models-consider-revisiting-full-honest-request-and-opinion.160349/post-1920107]</blockquote>

<blockquote>"All our amp models are authentic." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-14-01.165716/post-1989383]</blockquote>

<blockquote>"What I do is try to replicate a real tube amp as accurately as possible as that is the gold standard. Cygnus is demonstrably more accurate. I have the math and measurements that prove it. IMO it makes playing the amps more enjoyable. It may make recording require some more work, just like you would with a real tube amp. I don't know as I haven't tried that. For now if you don't like the changes go back to 15.01 or try some of the advanced tweaks. One of the things that Cygnus models more accurately is bias excursion and, in general, there is more bias excursion than before. You may not like the sound of bias excursion but it is part of what makes a real tube amp sound and feel the way it does. So one tweak to try is to reduce Master Bias Excursion or any of the individual bias excursion parameters. The other thing with Cyngus is the power tube bias. The previous firmware biased the virtual power tubes a bit hot in comparison to real amps. This was necessary because of the algorithm to prevent unwanted crossover distortion. The new algorithms are more accurate and, as a result, the power tube bias matches the real amps. If you want that old sound increase the Power Tube Grid Bias. Try around 0.6 to start." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2051686]</blockquote>

==Authentic or idealized controls==

[[image:amp.jpg|300px|link=]]

'''Axe-Fx III''' and '''FM3''' and '''FM9''' — if "Tone Control Display" in the [[Global Settings menu]] is set to AUTHENTIC (default), only the controls which are present on the actual amp are displayed on the main Tone page. When set to IDEAL, all tone controls are displayed.

Important: if AUTHENTIC is selected, the Bass, Mid and Treble controls are reset to their default values when changing models. This ensures accuracy for models that may not have these controls.

<blockquote>"It needs to reset all controls because not all are displayed. I.e. a Deluxe Reverb has no Mid control. For the authentic controls to work properly the Mid control needs to be set to its default position at noon." [https://forum.fractalaudio.com/threads/fm3-firmware-version-4-00-beta-5.173859/post-2107135]</blockquote>

The Amp block has one or two gain controls (Gain, Overdrive) and tone (B/M/T) controls, similar to the equivalent real amps. The range and behavior of those controls is the same as on the real amp.

"Cygnus" amp modeling:

<blockquote>"If an amp has an MV taper of greater than 15A the model's taper will be 15A otherwise it will match the amp. I.e., a Blues Jr. has an MV taper that is linear (which is ridiculous). The model's taper will therefore be 15A. There are a handful of exceptions, i.e. Camerons have linear taper MV and you need it with them because the signal level into the power amp is very low due to the Jose topology." [https://forum.fractalaudio.com/threads/mv-poll.170996/post-2059425]</blockquote>

<blockquote>"In the vast majority of models the knobs behave the same as the amp. There are a handful of models where I've taken artistic license and changed the tapers to give a more useable response. For example the Master Volume in a Blues Jr. is linear taper. This is ridiculous as it makes it very difficult to find the sweet spot. The model uses an audio taper instead which makes finding the sweet spot easier. (..) and now Cygnus firmwares have authentic behavior for most models except in a handful of cases where the manufacturer's choice of taper is dumb." [https://forum.fractalaudio.com/threads/cygnus-is-absolutely-magnificent.173225/post-2096570]</blockquote>

Before "Cygnus", the virtual Master Volume control didn't behave like the original one.

If the real amp has two gain controls, the one closest to the 1/4" input is modeled as (Input) Drive in the model. The other one is Overdrive.

If the real amp has two inputs (f.e. Low and High), the model is based on the high input. Set Input Trim to 0.500 to get the equivalent of using the low input.

If the original amp doesn't have a Bright switch but the model has, the switch corresponds to either a hardwired bright switch on the inside of the amp or it selects the amp's Bright channel (if there's not a separate model of the Bright channel).

<blockquote>(firmware Ares 6) "In general most knobs now behave exactly like the actual amp when possible. In a few instances there may be minor discrepancies between the knob position of the model and actual amp due to programming constraints and/or peculiarities of the actual amp (such as poor potentiometer tolerance). Due to variations in presence circuit topologies the taper of the Presence parameter, in particular, may vary between the model and the actual amp. In other words, a different setting on the model may be required to achieve the same response as the actual amp. In most cases however, the Drive, Treble, Mid, and Bass knobs will be accurate to within 10% of the actual amp."</blockquote>

<blockquote>"The tapers of the controls isn't really MIMIC per se. It's just me doing the dog-work and measuring the tapers. So, in that regard, the tapers match my amps. However manufacturers are notorious for changing tapers, sometimes right in the middle of a production run due to part availability. Furthermore the tapers in the Axe-Fx assume "true" logarithmic pots. Consumer-grade log pots are not true logarithmic, they're a crude approximation. At noon on a pot you'll get a nearly perfect match assuming the pot has 0% tolerance. As you deviate from noon there may be some error due to the approximation in the actual amp. As you get to the ends of the travel the error will decrease to zero. At any point there shouldn't be more than 10% or so deviation between the Axe-Fx knob position and the real amp. Master Volume tapers are NOT matched. If they were the amp volumes would jump all over the place when you switched amp types. IIRC I use a Log10A for the MV." [http://forum.fractalaudio.com/threads/axe-fx-ii-firmware-version-12-04-public-beta.80497/page-17#post-978667] </blockquote>

<blockquote>"In most cases the knobs do translate. Usually within 10%." [http://forum.fractalaudio.com/threads/axe-sounding-terrible-through-guitar-cab.58613/#post-732551] </blockquote>

<blockquote>(older firmware) "If an amp has just "Tone" then that's mapped to Treble. Leave bass and mid at noon." [http://forum.fractalaudio.com/threads/question-of-proper-axe-eq-values-for-amps-that-dont-have-them.67260/#post-828717] </blockquote>

<blockquote>(older firmware) "If the amp has no Master Volume, set the MV to 10 (the model will default to 10 when you select it). If the amp has no midrange control, set the MID to 5.00. If the amp only has a "Tone" control, set Bass and Mid to noon and the Treble control is your tone control." [http://forum.fractalaudio.com/threads/axe-tone-controls-vs-real-amps-tone-controls-question.69693/#post-855688] </blockquote>

<blockquote>(before Cygnus) "Master Volume tapers are NOT matched. If they were. the amp volumes would jump all over the place when you switched amp types. IIRC I use a Log10A for the MV." [http://forum.fractalaudio.com/threads/axe-fx-ii-firmware-version-12-04-public-beta.80497/page-17#post-978667] </blockquote>

<blockquote>(before Cygnus) "The only controls that do not necessarily match are the Presence and Master Volume. The Master Volume taper is the same for every amp. This was done to provide some consistency in finding the "sweet spot" of power amp break up and to prevent wildly fluctuating volume levels. The Presence control has a reverse log taper which gives the control a more reasonable behavior than that of most tube amps. A typical tube amp's Presence control does nothing over the first 80% of it's rotation which is stupid." [http://forum.fractalaudio.com/threads/real-vs-model-collection-thread.93693/#post-1124915] </blockquote>

<blockquote>(before Cygnus) "Presence and Depth controls may not match the taper of the actual amp. On most amps the Presence control does nothing until you turn it almost all the way up. This seems a bit silly so we make the Presence behave more logically. Same goes for the Depth control. Drive, Bass, Mid and Treble will match the actual amp within the tolerance of the pots. Another caveat when comparing amps: many times the knobs aren't "centered". IOW if you put the Treble knob at noon it isn't actually at 50%. You can see this by turning the knob all the way down and all the way up. It may not be symmetrical. This happens when the pots don't have a flat spot and/or the pot is rotated within the mounting hole." [http://forum.fractalaudio.com/threads/new-18-00-public-beta.96570/page-7#post-1158815] </blockquote>

<blockquote>(before Cygnus) "IMO accuracy is paramount and that's why we've devoted so much in resources to that end. The purpose of a modeler is to model amps as accurately as possible. Now it's impossible to account for component tolerances and tone controls can vary as much as 20% or more between two same amps. We therefore model all amps assuming the tone controls are "perfect" ((IOW if the amp was designed with a 500K pot we use 500K even if our reference amp is off by some percentage). We also don't match the Presence and MV tapers for previously discussed reasons. In some cases the Depth taper does also not match although this is infrequent. However you can be assured that even if the tapers don't match the models will match at the extremes of the control range and therefore the model is accurate but there may not be a 1-to-1 correspondence between the amp's knob and Axe-Fx's knob, i.e. Presence on 7 on the amp may be 5 on the Axe-Fx but 0 on the amp will be 0 on the Axe-Fx." [http://forum.fractalaudio.com/threads/axe-fx-vs-real-amp.107447/page-3#post-1286881] </blockquote>

<blockquote>"Internet wisdom states that no two amps of the same type sound the same. That is true, but the reasons are far more simple than many would have you believe. Tales abound of esoteric effects such as wire dress, transformer orientation, phase of the moon, etc. And while these do have some effect, it is arguably inconsequential relative to the single biggest source of deviation: tone control tolerance. I've spent the last ten years modeling tube amps and the number one thing I see is that tone controls are very inconsistent devices. First of all the tolerance of the control is typically 20%. That's plus or minus 20% so 40% total. A 100K pot can be as low as 80K or as high as 120K. This is contrast to the tolerance of a typical passive component which is 5% or less (usually much less IME). Secondly the resistance at the midpoint can vary widely. A Log10A pot should be 10% of the resistance at midpoint. But, again, this can be off 20%. Let's take the case of a bass control which is typically wired as a rheostat. On one amp the pot might be 10% high and the midpoint 10% high. Therefore with the control at noon (assuming, say, a 1M pot) the resistance will be 121K. Another amp off the assembly line might be 10% low. Therefore the pot will be 81K. That's a 40K difference between the two amps and that's not even worst-case. Now you can make the amps sound the same by simply turning down the control on one and/or turning it up on the other." [http://forum.fractalaudio.com/threads/no-two-amps-sound-the-same-fact-or-fallacy.109537/] </blockquote>

<blockquote>"You'll never get the knobs to correspond exactly. Commercial quality potentiometers are terrible. They vary widely in both end-to-end resistance and resistance at midpoint. Variations of +/- 20% are common (that's 40% total!!!). The Axe-Fx always assumes an ideal potentiometer, i.e. a pot where the end-to-end and midpoint resistances are exactly the specified value. Furthermore commercial "audio taper" pots are not truly logarithmic. They use a crude piecewise approximation. The virtual pots in the Axe-Fx are true log. This is the #1 reason for the whole "no two amps sound the same". In fact they probably do sound the same but you need to adjust the pots on one (and possibly quite a bit) to make it sound like the other. For example if a tone control is at noon (5.00) on one amp you may need to set the other amp to anywhere from 3.00 to 7.00. This applies to any product that uses potentiometers, including drive pedals. This also means when matching any virtual amp/drive/etc. in the Axe-Fx to a real-world counterpart that you may need to deviate significantly to get the same sound. For example, to get our reference Dual Rectifier's orange channel to match the model I need to set the model's treble control to around 4.0 (with the amp's treble at noon). This is because the pot in the amp has a significant deviation from the intended resistance at the midpoint. It's a 250K linear taper pot but it reads around 100K/150K when set to the midpoint. This is quite typical of commercial quality pots." [http://forum.fractalaudio.com/threads/so-about-that-new-si-diode-clipping-in-q5-xx-drive-block.120955/page-2#post-1439816] </blockquote>

<blockquote>"A typical pot used in a guitar amp has a tolerance of ±20%. On top of that there is the matching of the taper. The taper can also be off as much as 20% at the midpoint. So if we take, say, a 100K linear taper pot that's perfect it will have a resistance of 50K at the midpoint. We assume perfect pots in the models. However an actual amp may have a pot that's low by 20% so that would be 80K. If the taper is perfect then it's only 40K at the midpoint (20% error). If the taper is off then it might only be 32K at the midpoint for a total error of 36% (!!!). To get the same response on the model you would need to set that control to 3.6 instead of 5.0. That's an absolute worst case and I've never seen that but I routinely see pots that are 20% off at the midpoint." [http://forum.fractalaudio.com/threads/dual-recto-with-the-lb-2-vs-the-axe-fx-iii-and-more.143501/#post-1699121]</blockquote>

<blockquote>"I routinely see more than 20%. Full-scale resistance is often off by up to 20%. Mid-scale resistance is then off by another 10-20%. For example a 1M linear pot might be 800K and then off another 40K at mid-scale for a total error of 28%." [https://forum.fractalaudio.com/threads/legacy-amp-models-consider-revisiting-full-honest-request-and-opinion.160349/post-1919890]</blockquote>

<blockquote>(before Cygnus) "Most of the controls in the Axe-Fx match their physical counterparts. The exceptions are Presence and Master Volume. Most amps simply have the wrong taper for their Presence controls. For example a 5150 Presence control does absolutely nothing from 0 to 7. All the action happens in the upper 1/4 of the control's range which is just dumb. The Axe-Fx uses a proper taper which gives a nice, even response over the full range of the control. Likewise the Master Volume on many amps is too abrupt. By 2-3 on the knob the power amp is saturating. Again we use a more rational taper so that you have finer control over power amp distortion. The downside of this approach is that if you put the Presence and Master Volume controls in the same position as the amp it won't sound the same. People do this then post videos and proclaim "See? Modeling isn't accurate!!! Toobz rule brah."" [https://forum.fractalaudio.com/threads/legacy-amp-models-consider-revisiting-full-honest-request-and-opinion.160349/post-1920107]</blockquote>

<blockquote>"If a knob isn't present in the Authentic menu then it may not do anything in the Ideal menu."</blockquote>

<blockquote>"If a parameter doesn't exist in the Authentic controls there is no guarantee that the parameter in the Ideal controls will be functional." [https://forum.fractalaudio.com/threads/hi-cut-control-on-citrus-rv50-not-working.178740/post-2178756] </blockquote>

<blockquote>"The sensitivity to pot value is very high. Consumer potentiometers have a 20% tolerance on end-to-end resistance and another 20% on midscale resistance. If the taper of the pot is Log10A and the pot is a nominal 1M then the midscale resistance should be 100K. If the pot is 20% low on end-to-end resistance (800K) and then another 20% low on midscale resistance then it's value at midscale would be only 64K. That's nearly half the nominal value. The potentiometer values used in the models use "nominal" values. If the amp was designed with 1M pots then we use 1M for the pot value. When comparing the models to the amps I routinely have to change the B/M/T controls +/-20% to get the model to match the amp. And this is expected. For example on my 5150 I have to set the model's bass control to 4 to match the amp at 5 (-20%). This is unsurprising since when we measured the pot in the amp it was about 20% low at mid-scale." [https://forum.fractalaudio.com/threads/buttons-functioning-as-on-amps.170531/post-2052812]</blockquote>

<blockquote>"Most of the tweaks in an Axe-Fx / FM3 are circuit tweaks so it would be equivalent to modding your amp. In the case of a Vibrolux the amp has a fixed midrange resistor in the tone stack. In the Authentic menu the midrange control is not there and the resistor value is fixed. When using the ideal page the midrange resistor is adjustable. This would be equivalent to modding your amp by adding a midrange pot." [https://www.thegearpage.net/board/index.php?threads/fractal-question.2267220/post-32792621]</blockquote>

Also read this: [https://forum.fractalaudio.com/threads/why-your-amp-doesnt-sound-like-our-amp.172907/#post-2090367 Why Your Amp Doesn't Sound Like Our Amp]

<blockquote>"A potentiometer has tolerances, two of them. The first is the end-to-end resistance. If a pot is rated at 1Mohm, 20% then it's end-to-end resistance can be anywhere from 800K to 1.2M. The second is midpoint resistance. That same pot might be a linear pot which implies the midpoint resistance is 50% of the end-to-end resistance. Again, there is a tolerance on this value, typically about 10%. Now, an ideal 1M, linear potentiometer will have a midpoint resistance of 500K. But a given amp may end up with a pot that is 20% low in end-to-end resistance and ALSO 10% low on midpoint resistance. So that pot is now 1/2 of 800K (400K) minus 10% which yields 360K. That particular amp will sound different than one that has a pot with tighter tolerances. It's is therefore impossible for one amp to sound exactly the same as another copy of the same amp and, by extension, a model of the amp to sound exactly like a particular copy of the amp. [https://www.thegearpage.net/board/index.php?threads/what-dont-you-like-about-fractals-modeling.2326185/post-34061838]</blockquote>

<blockquote>"If you take two copies of a particular amp and put all the knobs at 7, they won't sound the same. Likewise the model with all knobs at 7 won't sound the same either. However, the amps and the model will sound similar, very similar in most cases. We always assume the potentiometers in our models are ideal and have 0% tolerance both end-to-end and midpoint. Another way of saying this is if you put a knob on the real amp at 7, our model with the knob on 7 will be as close as another random copy of that amp with its knob on 7 will be." [https://www.thegearpage.net/board/index.php?threads/what-dont-you-like-about-fractals-modeling.2326185/post-34061891]</blockquote>

<blockquote>"The tolerance of potentiometers is terrible. You cannot set the knobs exactly the same as a given amp and expect things to match perfectly. For example, with BMT at noon on our reference 5150 I have to set the model's bass control to around 4.5 and the treble to nearly 6 to match. This is because the bass and treble pots are not perfect in the real amp. Do a search on potentiometer tolerance. End-to-end and center. You'll be amazed at just how poor consumer grade "quasi-log" pots are. Our models assume the pots are "perfect" and exhibit the exact resistance as specified. I.e. if it's a 1M 10A pot then it will be exactly 100K with the wiper at mid rotation. In a real amp the end-to-end resistance is +/- 20% and the midpoint can be off another 20%. Do the math and you'll see why no two amps sound the same at the same knob settings and why the model will not necessarily match a particular amp at the same knob settings. I assure you that our model is accurate. You may have to adjust the controls up or down as much as 20% to match a given amp. That's the nature of tolerance. Listening to the clip I would say turn the bass up to 7 or more, turn the treble and mid down a bit." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-00-release-candidate-2-beta-8.188778/post-2342264]</blockquote>

<blockquote>"There are many different types of "Log pots". Logarithmic potentiometers (more correctly known as audio taper pots) have "tapers". There are 5A, 10A, 20A, 25A, and 30A as well as reverse versions. The most commonly used tapers in guitar amps are 10A and 30A. The taper indicates the percentage of maximum resistance when the pot is halfway. I.e., a 1M 10A pot will be 100K at noon. A pot labeled as 1MA doesn't indicate the taper and Mesa, in particular, doesn't like to divulge the tapers they're using. When I compared our reference Mark IV to our reference Mark V the tapers of the controls were different." [https://forum.fractalaudio.com/threads/question-about-the-mark-series-graphic-eq-modeling.149223/post-2476619]</blockquote>

<blockquote>"In most cases the tapers are the same as the real amp. In a handful of cases they are not. This cannot change at this point since it would change existing presets." [https://forum.fractalaudio.com/threads/presence-taper-that-matches-the-real-amp.187775/post-2483234]</blockquote>

[[image:tapers.png|300px]]

The range of the Drive taper in the Axe-Fx is 0-10. Volume knobs on Fender amps go from 1 to 10. This translates to:

:Fender 1 = Axe 0.00 
:Fender 2 = Axe 1.11 
:Fender 3 = Axe 2.22 
:Fender 4 = Axe 3.33 
:Fender 5 = Axe 4.44 
:Fender 6 = Axe 5.55 
:Fender 7 = Axe 6.66 
:Fender 8 = Axe 7.78 
:Fender 9 = Axe 8.89 
:Fender 10 = Axe 10.00

<blockquote>"For a Fender the controls go 1-10. On the model they go 0 - 10. To replicate the amp's controls multiply by 1.1 and subtract 1.1. I had the amp set to 6, 6, 6 and set the model to 6, 6, 6 and there was too much bass and gain. But the correct value is 5.5, 5.5, 5.5." [http://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-00-beta.148607/page-15#post-1760226]</blockquote>

[http://forum.fractalaudio.com/threads/conversion-chart-for-real-amp-settings-vs-fas.106182 Conversion chart for amp controls which go to 10 or 11]

==Why your amp doesn't sound like Fractal Audio's==

Fractal Audio explains:

<blockquote>"The models in our products are based on our in-house reference amps. If a model doesn't sound like your version of that amp it won't sound like our reference amp either.

Why?

Component accuracy and drift. 
The components used in tube amps are low-cost, consumer-grade parts. They typically have tolerances of 10% or more. Over time the value of these components drifts. If your amp is old chances are it doesn't sound like it did when it was new. All our old reference amps are given a thorough checkup prior to modeling with any out-of-tolerance parts replaced.

Potentiometer tolerance. 
A typical consumer potentiometer has a tolerance of up to +/- 20%. That's huge and that's end-to-end accuracy. On top of that the midpoint accuracy can be another +/- 20%. So if you have a 1M pot it could be as low as 800K. If it's linear it's midpoint should be 400K but could be as low as 360K. Now your 1M pot that should be 500K at halfway is only 360K. That's an error of 28%!

Potentiometer taper. 
A big one. Potentiometers come in a variety of tapers: linear, 30A, 20A, 10A, etc. The taper on an audio taper pot (i.e. 30A) denotes the value of the pot at mid rotation. For example a 1M, 10A pot would be 10% of its value at "noon", or 100K. Manufacturers are constantly changing the taper of the pots in their amps. Sometimes the designer changes the taper as customers are reticent to turn knobs much away from noon. It's a weird psychological thing. Sometimes the manufacturer changes the taper due to availability concerns. Sometimes they change the taper when moving manufacturing locations. Sometimes they change the taper for no apparent reason at all. Another factor is that almost all amps don't use true log taper pots. They use "commercial log" taper which is a crude approximation to a log taper. This is because true log taper pots are expensive. Fractal Audio products use true log taper. This means that '7' on your amp is not exactly '7' on the model even if the pot in your amp is exactly 1M and its taper is exactly 10A. Why do we do it this way? Because the response is smoother and if true log pots were the same price as consumer log pots everyone would use true log taper. We model all amps assuming the pots are ideal. We assume the end-to-end resistance is exactly, say, 1M and the midpoint is, say, exactly 100K. We DO NOT use the values measured in our reference amp because no two amps are the same so we use the DESIGNERS INTENDED VALUE. What all this means is '3' on your amp is not necessarily the same as '3' on the Axe-Fx. Example: the Master Volume pot in a 5150 is a 1M, 15A audio taper pot. Theoretically it should be 150K at noon. On our reference amp it's about 15% low. If the reference amp's MV is set to '3' we have to set the model to around '2.5' to match. This is unsurprising due to the tolerance of the reference amp's pot.

Indicator accuracy. 
On many amps if you set a knob to noon it's not actually halfway in the pot's rotation. Why? Several reasons. Some amps are just weird. For example the Bogner Shiva's minimum rotation is around 6:00 and the maximum is around 4:00. So noon is actually past midpoint. Same with Soldanos. In other cases the knobs aren't oriented perfectly on the shaft. If it's a knurled shaft the knob may be off one tooth. If it's a smooth shaft then you're at the mercy of the human who put the knob on the shaft and tightened the set screw. This is why I prefer D-shafts. Finally the pot itself may be rotated relative to the panel. You can try this yourself. Turn the knob on your amp fully CCW. Note the position of the indicator. Now rotate fully CW. Note the marker position. If it's an old amp it's probably not symmetrical. Then there's the whole marking thing. Fender's are numbered 1-10. Soldanos go to 11. We use 0-10 so be wary of the amp's numbering.

Power Tube Bias. 
Another big one. The transconductance (gain) of a power tube can vary greatly. This is why power tubes are color coded, sold in matched sets, etc. Amps come in two flavors: fixed bias and cathode bias. Fixed bias amps apply a "fixed" voltage to the grid of the power tubes. Cathode bias amps use a resistor between the cathode and ground to self bias the tube. Most, but not all, fixed bias amps allow the user to adjust the bias point of the amp. This allows the bias point to be set to an optimum value for the particular set of tubes installed (since the transconductance can vary greatly). Some fixed bias amps do not allow adjustment. Examples are Mesa/Boogies, 5150s, and several other brands/types. The drawback of this is that the bias can vary greatly depending upon the gain of the tubes installed. Due to this the manufacturers err on the safe side and the bias is usually much colder than the ideal value. Most cathode biased amps are not adjustable. Again you are at the mercy of the tube's gain but these amps tend to be biased hot to begin with and have higher transformer matching which prevents excursion outside of the S.O.A. (safe operating area). If the bias is adjustable where the manufacturer decides to bias their tubes is a matter of preference. Most manufacturers bias their tubes on the cold side to prevent premature failure and reduce warranty claims. Especially the larger manufacturers. This leads to the question of "what is the ideal bias point?" The pervasive school of thought is you adjust the bias so the idle dissipation is 60-70% of the tube's peak power rating. This is a safe approach and ensures that the tubes don't "red plate" and live fairly long and prosperous lives. My opinion is that the ideal bias point is NOT a function of the tube's power rating. It's the point at which the power amp's transfer function is most linear. Unfortunately operating the tubes at that point can result in exceeding the tube's S.O.A. So the optimum bias point depends on the tube's power rating, the transformer primary impedance (matching) and the user's tolerance to tube replacement frequency. For example, if we bias an EL34 based power amp at 60% peak dissipation it's actually running fairly cold. If we know that the transformer is slightly overmatched we can bias the tubes hotter, 70% or even more. This will result in a warmer tone but the tubes will wear faster. What does all this mean? Well, I bias the virtual tubes on the warm side. EL34s are biased at around 70% because we don't have to worry about them wearing out. 6L6s are biased a little colder, around 60% but this is actually as "warm" as the EL34s because of the higher plate dissipation of a 6L6. In practice this means that the models in the Axe-Fx will biased warmer than a new amp straight out of the box as most amps are biased cold (too cold IMO). After you wear the tubes out and bring it to a tech the tech will replace those tubes and bias them hotter than factory. So if you're comparing your new, out-of-the box 5150 with the Axe-Fx model the amp will probably sound "colder". Some people like this, many do not. If you like a colder sounding power amp it's just a knob twist away." [https://forum.fractalaudio.com/threads/why-your-amp-doesnt-sound-like-our-amp.172907/post-2090367]</blockquote>

and:

<blockquote>"A potentiometer has tolerances, two of them. The first is the end-to-end resistance. If a pot is rated at 1Mohm, 20% then it's end-to-end resistance can be anywhere from 800K to 1.2M. The second is midpoint resistance. That same pot might be a linear pot which implies the midpoint resistance is 50% of the end-to-end resistance. Again, there is a tolerance on this value, typically about 10%. Now, an ideal 1M, linear potentiometer will have a midpoint resistance of 500K. But a given amp may end up with a pot that is 20% low in end-to-end resistance and ALSO 10% low on midpoint resistance. So that pot is now 1/2 of 800K (400K) minus 10% which yields 360K. That particular amp will sound different than one that has a pot with tighter tolerances. It's is therefore impossible for one amp to sound exactly the same as another copy of the same amp and, by extension, a model of the amp to sound exactly like a particular copy of the amp. [https://www.thegearpage.net/board/index.php?threads/what-dont-you-like-about-fractals-modeling.2326185/post-34061838]</blockquote>

and:

<blockquote>"If you take two copies of a particular amp and put all the knobs at 7, they won't sound the same. Likewise the model with all knobs at 7 won't sound the same either. However, the amps and the model will sound similar, very similar in most cases. We always assume the potentiometers in our models are ideal and have 0% tolerance both end-to-end and midpoint. Another way of saying this is if you put a knob on the real amp at 7, our model with the knob on 7 will be as close as another random copy of that amp with its knob on 7 will be." [https://www.thegearpage.net/board/index.php?threads/what-dont-you-like-about-fractals-modeling.2326185/post-34061891]</blockquote>

and:

<blockquote>
"The tolerance of potentiometers is terrible. You cannot set the knobs exactly the same as a given amp and expect things to match perfectly. For example, with BMT at noon on our reference 5150 I have to set the model's bass control to around 4.5 and the treble to nearly 6 to match. This is because the bass and treble pots are not perfect in the real amp. Do a search on potentiometer tolerance. End-to-end and center. You'll be amazed at just how poor consumer grade "quasi-log" pots are. Our models assume the pots are "perfect" and exhibit the exact resistance as specified. I.e. if it's a 1M 10A pot then it will be exactly 100K with the wiper at mid rotation. In a real amp the end-to-end resistance is +/- 20% and the midpoint can be off another 20%. Do the math and you'll see why no two amps sound the same at the same knob settings and why the model will not necessarily match a particular amp at the same knob settings. I assure you that our model is accurate. You may have to adjust the controls up or down as much as 20% to match a given amp. That's the nature of tolerance. Listening to the clip I would say turn the bass up to 7 or more, turn the treble and mid down a bit." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-00-release-candidate-2-beta-8.188778/post-2342264]</blockquote>

==Polarity==

<blockquote>
"All amp models have the same polarity so that you can mix them without weirdness." [http://forum.fractalaudio.com/threads/axr-fx-ii-xl-noise-over-palm-mute.119930/page-2#post-1444307]
</blockquote>

==Input impedance==

<blockquote>
"Tube amp models are always 1M (no capacitor)." [https://www.thegearpage.net/board/index.php?threads/fractal-fm3-fuzz-w-fixed-impedance.2214483/post-31728537]
</blockquote>

==Settings for FRFR or guitar speaker==

[https://forum.fractalaudio.com/threads/table-amp-settings-depending-on-power-amp-and-speaker.185259 Click here for the recommended Amp and Cab settings for each type of amplification]

==When using a tube power amp (and traditional cab)==

===Power amp modeling===

When using a [[Connections and levels|tube power amp for amplification]], it makes sense to disable Power Amp modeling. Of course, YMMV.

However, some tube amps, such as Fryette's Power Station and LX-II, are designed to have a neutral impact on the sound and allow Power Amp modeling to be enabled.

To turn off Power Amp modeling:

* Pre-Cygnus amp modeling: '''Turn off Supply Sag in the Amp block (display shows: "p.a. off")'''

* Cygnus amp modeling: '''Turn off Power Amp Modeling in the Amp block'''

and/or

* '''Disable Power Amp Modeling in the Global Settings menu'''

The result of switching it off in the amp model versus adjusting the global parameter is not exactly the same:

<blockquote>"If you shut the power amp modeling off from the Global menu, it is not exactly the same as turning it off (in the Amp block). This is because the virtual power amp always runs. So if you shut the power amp modeling off from the Global menu, the supply will still sag resulting in a more compressed response. If the Master is set high the sag can be quite pronounced." [http://forum.fractalaudio.com/threads/power-amp-sim-on-off-vs-sag-on-off-with-real-power-amp-behaviour-of-presence-control.121178/#post-1442553] </blockquote>

Turning off Power Amp modeling is not the same as bypassing the Amp block. If Power Amp modeling is disabled, preamp modeling will still run.

If Power Amp modeling is disabled, Depth and Presence are disabled (Quantum 9.03 and later), and Master Volume changes into a simple volume control. (Before Quantum 9.03, Presence turned into a shelving filter when power amp modeling was disabled.)

===Speaker-related parameters===

[[image:h_cabs.png|link=]]

When using an [[Connections_and_levels#Power_amp_and_guitar_speaker|external power amp and a traditional guitar speaker cabinet]] to amplify the modeler, make sure that [[Amp_block#SPEAKER_DRIVE|Speaker Drive]] is disabled in the Amp block. This parameter should be used only with virtual cabinet models.

Cabinet modeling should be disabled altogether when using a traditional guitar speaker cabinet, either by bypassing the Cab block in the preset, or by turning off Cabinet Modeling in the [[Global Settings menu]]. When using a speaker that's been designed for FRFR, do NOT turn off Cab Modeling.

When using a non-neutral tube power amp, turn off Power Amp Modeling (see above), [[Amp_block#SPEAKER_COMPRESSION|Speaker Compression]], [[Amp_block#SPEAKER_COMPLIANCE|Speaker Compliance]] and [[Amp_block#CABINET_RESONANCE|Cabinet Resonance]]. When using a solid-state power amp, you don't have to turn off these controls.

<blockquote>"If using a solid-state amp into a traditional cab I would recommend Speaker Compression and Compliance not be zero. If using a tube power amp into a traditional cab all should be zero." [http://forum.fractalaudio.com/threads/axe-fx-iii-firmware-2-00-public-beta-2.144615/page-2#post-1710669]</blockquote>

Low Freq and High Freq Resonance are pre-set frequencies at which the virtual amp resonates with the cab model. The values depend on the selected [[Amp_block#SPEAKER_IMPEDANCE_CURVE|Speaker Impedance Curve]] on the Speaker page of the Amp block (firmware Ares 11 and later). When using a real cabinet, you'll want to replace this with the "real" resonant frequency of the cabinet, if you know it.

Firmware 22 and later for the Axe-Fx III enables automatic adjustment of the Speaker Impedance Curve in the Amp block to the selection of a "DynaCab" in the Cab block:

<blockquote>"The Amp block now features “Auto Dyna-Cab Impedance”. When set to ON the speaker impedance curve of the Amp block will follow the Cabinet Type in the first mixer slot of the associated Cabinet block. I.e., if the Cab Type in the first mixer slot of Cabinet 1 is, say, 4x12 5153 and the Mode is Dyna- Cab then Amp 1’s speaker impedance will automatically be set to 4x12 5153." </blockquote>

Also take a look at the [[Amp_block#OUTPUT_MODE|Output Mode]] setting in the Amp block.

==Tweaking an amp==

First, load the correct default parameters for the selected amp type, by resetting the Amp block.

The Band-Commander (clean tone) and Friedman BE (dirty tone) amp types at default settings provide useful baseline tones and may be useful as reference when tweaking.

Be aware that the choice of a cab (IR) in the Cab block often has much more impact on the tone than tweaking controls in the Amp block.

<blockquote>"One of the things I've found really useful about these (far-field IRs) is they are a good starting point for dialing the amp block in. Near-field IRs can have excessive bass and/or treble. To compensate we might end up doing strange things in the amp block which throws off the distortion character and feel. When using a far-field IR it's very similar to how the amp sounds through a conventional cab. So what I'm doing is using one of the far-field IRs to start, dial in the amp block and then choose a near-field IR. I then adjust the low/high cuts in the cab block rather than adjusting the amp block." [https://forum.fractalaudio.com/threads/free-far-field-session-2-cab-pack-for-axe-fx-users.151232/post-1801544]</blockquote>

==Switching between amps==

Here are the most common methods to switch between amp models:

* Use different Presets.
* Switch between two Amp blocks in a preset via MIDI.
* Switch between two Amp blocks in a preset via Scenes.
* Switch between two Amp blocks with the Multiplexer block.
* Crossfade between two Amp blocks with the Mixer block.
* Use X/Y switching in a single Amp block.
* Use Channels with a single Amp block.
* Use Scenes and a Scene Controller with a single Amp block.

The time to switch scenes and presets depends on the device, available CPU and effect settings (bypassed or not, X/Y states and channels).

X/Y switching and switching Channels causes a short gap in the sound. The gap is caused by the necessity to briefly mute and unmute the sound. The gap doesn't occur in firmware 23 and later for the Axe-Fx III.

<blockquote>(AX8) "Our modeling is very detailed and whenever the amp model changes the "virtual circuit" needs to be reconfigured. We can switch quickly but often this causes clicks and pops due to the reconfiguration. So the amp block needs to run silently for a bit so things will settle. Then we unmute the block. This mute period is what you are hearing. Most other products just use a fixed algorithm and change the input/output EQ and gain. With this type of algorithm you can switch quickly without clicks and pops but, of course, you don't get the realism and detail." [http://forum.fractalaudio.com/threads/does-the-ax8-have-an-audio-gap.118736/page-2#post-1413280] </blockquote>

To avoid this, switch between two Amp blocks if the hardware allows it, or use Scene controllers to change amp settings instead of X/Y switching or Channels, or use [http://forum.fractalaudio.com/threads/various-presets-tricks.135770/#post-1625421 Bakerman's compression trick].

[https://www.youtube.com/watch?v=q-4bpljNxvA&t=50s Cooper Carter: Gapless Amp Switching on the Axe-Fx III]

[https://www.youtube.com/watch?v=9ncGcU0QS2A&t=61s Cooper Carter: Live Two Amp Blending]

Switching channels on the Axe-Fx III is very fast (and has disappeared in firmware 23 and later).

<blockquote>(Axe-Fx III) "The "gap" is arbitrary and is simply the time to fade down the old amp and fade up the new amp. You HAVE to do some ramp-down and ramp-up or you'll get artifacts as the gain can be completely different. If you just instantly switch from a clean amp to a distorted amp or vice-versa you'll get a pop. That's just basic signal processing." [http://forum.fractalaudio.com/threads/presenting-the-axe-fx-iii.134717/page-26#post-1593840] </blockquote>

<blockquote>(Axe-Fx III) "Feels seamless to me (and faster than any of my channel switching amps) but everyone has different definitions." [http://forum.fractalaudio.com/threads/presenting-the-axe-fx-iii.134717/page-27#post-1593846] </blockquote>

<blockquote>(Axe-Fx III) "Any faster than that and you risk pops or clicks if the levels and/or gains are markedly different. You can't change the laws of nature." [http://forum.fractalaudio.com/threads/presenting-the-axe-fx-iii.134717/page-31#post-1594370] </blockquote>

<blockquote>"On the III it mutes just the block so the reverb and delay are unaffected." [http://forum.fractalaudio.com/threads/axefx-iii-whats-missing.134747/page-5#post-1594439] </blockquote>

<blockquote>"The Axe-Fx switches amp channels very fast, 19 ms. This is comparable to a typical tube amp." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-22-00-public-beta-5-beta-11.194550/post-2423513]</blockquote>

Firmware 23 for the Axe-Fx:
<blockquote>"Preset, Scene and Channel changes are now gapless."</blockquote>

[https://forum.fractalaudio.com/threads/get-rid-of-switching-audio-gaps-p1-6-technical-measurements-and-info.195653/ More about audio gaps]

==Quick access to controls==

'''Axe-Fx III''' and '''FM9''' — Assign controls to the Performance Pages (when assigned). Or, from the Home screen, push Page Right and the AMP 1 or AMP 2 button.

'''FM3''' — Assign controls to the Performance Pages (when assigned). Or, from the Home screen, push Page Right and the AMP button.

'''Axe-Fx II''' — Assign a Quick-Jump button (X/Y) to the Amp block in the I/O menu.

==Cut, Bright, Fat and Boost switches==

All amp models have these switches, even if the original "real" amplifier doesn't have them. They can be set per scene or by pushing a button by assigning a controller. This can be an external controller or a Control Switch. [https://www.youtube.com/watch?v=kXvVf-vV8bI Here's a demo].

==Midrange smoothness==

Fractal Audio:

<blockquote>"The "midrange smoothness" is actually adjustable in our modeling but it's hidden from the user. A real tube power amp clips hardest in the low midrange frequencies because this is where the trough in the speaker impedance is located.

At those frequencies (if the transformer is slightly undermatched, as is often the case) the grids clip before the plates. Grid clipping is very hard, almost a hard limiter. Plate clipping is much softer. We model all this but the grid clipping "shape" is hidden from the user and varies by model.

Many modeling algorithms, however, treat everything with a single nonlinearity and ignore grid clipping. This makes the midrange clipping softer and leads to a "sameness" across the spectrum.

The clipping in a tube power amp can be divided into three categories:
Grid clipping. This occurs in the low midrange and is a harder distortion.
Plate clipping. The plates clip at the speaker low frequency resonance and in the upper midrange frequencies and beyond. Plate clipping is softer.
Transformer distortion. Transformer distortion is a complex distortion that increases with the inverse of frequency. It is sort of soft and farty.

Then there is crossover distortion which is not clipping but another form of nonlinearity.

The more nonlinearities you model, the more complicated the algorithm and the more CPU power required.

Then you get preamp distortion which is a whole 'nother can of worms." [https://www.thegearpage.net/board/index.php?threads/shootout-with-clips.2300109/post-33478318]</blockquote>

==Reset the amp==

===About the Amp block===

Amplifier models (aka “amp types”) are available through the AMP block. Here you select the type that you want. An amp model presents itself in the AMP block through its typical name, and its specific settings.

Some of these specific settings are displayed in the AMP block. Some of them are hidden from the user. They are (probably) part of a table which gets interpreted by the firmware upon loading an amp model, together with the appropriate amp modeling algorithm. All parameters are discussed in the owner’s manual and here in the wiki.

Disclaimer: the description above is a very simplified version of what's happening in the AMP block.

===Why would you want to reset an amp===

Resetting an amp means that settings in the AMP block are returned to their correct default values for the currently selected amp model.

====Because YOU changed things====

You can adjust settings in the AMP block. Not only basic stuff like volume, gain and tone, but also many parameters that go much deeper. You can extensively tweak the sound and feel of the amp model to your liking. This is a unique feature of Fractal Audio’s amp modelers.

If you tweak the more advanced settings, you deviate from the default parameter values specific to that amp model. By resetting an amp you make sure that the correct default settings for that amp model (hidden and visible) are put back in place.

====Because FRACTAL AUDIO changed things====

Fractal Audio continually improves its technology through firmware updates. These firmware updates include improvements to the underlying algorithms and to specific amp model settings, based on those algorithms. This poses a challenge for handling existing presets.

Changes to the core amp modeling algorithms are always applied, so the sound may change. There’s no way around this, meaning that there’s no support for older versions of core algorithms. If you want to stick to older algorithms, do not update the firmware.

Specific AMP block settings, whether visible or hidden, are sometimes updated to new default values automatically when updating firmware that includes amp modeling improvements. And sometimes they are not (not automatically), because some users want to keep existing values. The firmware comes with release notes that inform you about this. In general, there’s NO NEED to reset an amp after updating firmware, unless the release notes say so.

Resetting an amp makes sure that the correct default settings for that amp model (hidden and visible) are put back in place. For example, to get a clean start, or to compare settings and sound.

'''''Disclaimer:''''' ''The description above is a very simplified version of what's happening in the AMP block.''

===What happens when you reset an amp===

To accommodate users, Fractal Audio provides several methods to reset the amp, each with a different outcome.

The reset methods for the AMP block are:
# soft reset
# hard reset
# reset in the editor’s Manage Presets tool

These methods are explained below.

===SOFT reset (re-select)===

A “soft reset” means that you select another amp type in the AMP block and then re-select the previous amp type again. Or just select the current amp type again in the editor. This is referred to as a "soft reset".

When doing this, the amp model will be loaded again with most of its parameters returned to their default specific settings. It applies to the current amp channel only. The preset needs to be saved afterwards.

Whether the basic tone controls are left untouched OR also return to default when performing a soft reset, depends on the value of TONE CONTROL DISPLAY in the [[Global Settings menu]]:
* when set to AUTHENTIC: a soft reset will also return Bass / Middle/ Treble to their default values
* when set to IDEAL: a soft reset will not change the existing Bass / Middle / Treble settings.

The list below describes what happens when performing a soft reset, page by page (last checked in February 2021):

* Authentic / Ideal page — everything default, except: Bass/Mid/Treble (unless TONE CONTROL DISPLAY is set to AUTHENTIC), Gain, Overdrive, Input Select, Mute, Level, Balance.
* Preamp — everything default, except: Boost Type and Boost Level.
* Power Amp — everything default.
* Power Supply — everything default, except: Tremolo Frequency.
* Speaker — everything default.
* Speaker Drive — everything default, except: Speaker Compression, Speaker Time Const, Output Mode.
* Input EQ — everything default, except: Input Type and Q.
* Output EQ — everything default, except: EQ On/Off.
* Dynamics — everything default, except: Master Bias Excursion, Out Comp Type.

A soft reset guarantees that your AMP block settings are in line with the latest modeling defaults, while preserving your basic gain and tone settings (depending on the TONE CONTROL DISPLAY setting).

===HARD reset===

If you want each and every parameter of the amp model to be returned to its default value, without exceptions, you need to fully reset the model, on the hardware or in the editor. This is referred to as a "hard reset" or "full reset". It applies to the current amp channel only. The preset needs to be saved afterwards. A hard reset lets you start 100% fresh, a good way building a new preset.

On the hardware, select the AMP block, press EDIT, press RESET (soft knob A). This resets the current channel only.

In the software editor:
* select the AMP block, select the Block menu at the top of the editor and select Reset Channel, or
* right-click the AMP block (the context menu appears), click Edit and select Reset Channel, or
* select the AMP block, and press CTRL-I (Windows) or Command-I (Mac).

Note: removing and adding an AMP block on the grid is NOT the same as a hard reset.

===Reset in the editor’s Manage Preset tool===

This method has been made available in the latest version of the editors.

In Manage Presets, select one (or more!) presets, and use the context menu (right-click) to select "Reset AMP block".

This will reset ALL channels of the AMP block in the selected preset(s), while maintaining the settings on the Authentic page of the AMP block, and automatically saves the preset(s) too.

So why this option if a soft reset kinda accomplishes the same thing? Well, this method makes batch processing possible: resetting all channels of all AMP blocks in a bunch of presets through a single command.

However, be aware that this method will reset the following AMP block settings:
* graphic EQ
* speaker impedance curve

===Is “Refresh After New FW” the same as a reset===

The software editors provide a menu option "Refresh After New FW". This is NOT a reset command! It syncs the software with the hardware.

The Refresh command is executed by the editor by itself after updating updating the device with officially released firmware.
When testing BETA versions of firmware, the Refresh command may need to be executed manually to force the editor to sync with the hardware.

===Can you reset a single parameter to its intended default value===

No. A reset always resets the entire channel of the block.

You may think that double-clicking a control in the software editor resets it to its default value but that’s not the case: that value is just a generic default value, not necessarily the correct value for the specific parameter and amp type.

Ideally double-clicking should reset it to the correct value, but this is a limitation of the architecture at this time. [https://forum.fractalaudio.com/threads/fm3-firmware-version-3-01.168482/post-2024066]

==Preserve your amp tones==

So you have dialed in a perfect-sounding amp by tweaking some advanced parameters. And here comes a firmware update you absolutely don't want to skip. But you don't want to lose your carefully dialed-in sound.

Your current presets and amp settings are always connected to the currently loaded firmware version. If you upgrade the firmware and the firmware includes changes to the amp modeling, your sound may change.

Reapplying "old" amp block settings often is not the best choice. New defaults have been implemented for a reason, and may also be linked to changes in algorithms in the firmware. Using the same tweaked values may not result in the same sound.

Here are the methods you can use to backup your stuff, or re-use it:

* '''Fractal-Bot''' — save and load entire banks of presets, and firmware
* '''Software editor''' — export (save on disk) a single preset, and load a single preset (including ones from a bank), or make a "snapshot"
* '''Recall Effect''' (if available on your device) — load the values of an AMP block from one preset into another (not on Axe-Fx III)
* '''Global blocks''' (if available on your device) — save Amp block settings to different instances of a global block

==Amp gain==

There are many ways to increase or decrease amp gain.

IMPORTANT: adjusting Input Level or Input Pad in the I/O menu does not affect amp gain!

*'''Your guitar's output'''
* '''Global amp gain''' — adjust the global Amp Gain parameter in the system settings (Axe-Fx II and AX8 only). This parameter lets you adjust the range of gain of the amps in all presets. This is also possible per preset via the Input Trim parameter in the Amp block.

<blockquote>(Axe-Fx II) "The global Amp Gain is for people who use different guitars and want the input gain to be the same even though the guitars have different outputs. The unity gain feature in the II doesn't allow for this. It makes sure the signal your guitar puts out is what the input to the grid sees while still making sure the A/D converters get a good signal." [http://forum.fractalaudio.com/threads/incoming-incoming-incoming.39841/page-5#post-540320]</blockquote>

<blockquote>(Axe-Fx II) "They (Amp Gain and Input Trim) are basically the same thing. The global Amp Gain has a smaller range as it's designed for fine-tuning between guitars whereas the local trim allows you to radically alter the response of the model." [http://forum.fractalaudio.com/threads/input-trim-global-amp-gain.40418/#post-545862]</blockquote>

* '''Input 1 Gain ''' — This control in firmware Ares 12.12 and later for the Axe-Fx III (FM3 and FM9: n/a) allows trimming the Input 1 gain to adjust for variations in guitar output level without having to adjust each preset.
* '''Input block level''' — increase Level in the Input block to increase the signal strength entering the grid. The Level parameter in each block before the Amp block also has an impact on the signal entering the Amp block.
* '''Drive block''' — insert a Drive block before the Amp block. Select a type such as FET Boost or Tape Dist for a clean boost and attach a pedal to its Drive parameter. Or set a Drive block to TS808 or something similar with Drive all the way down and Level turned up to tighten low end.
* '''Input trim''' — Input Trim in the Amp block lets you decrease or increase the level of the signal going into the Amp block. The difference between the High and Low inputs on a Fender amp is around -6 dB, which equals to Input Trim at 0.500.
* '''Drive parameters''' — each Amp block has one or two Drive parameters controlling the amount of gain. You can assign an external controller to vary the gain.
* '''Master volume''' — increase Master Volume for more power amp distortion. Increase Mstr Vol Trim on the Advanced parameters page to increase the range of the master volume.
* '''Boost''' — engage Boost in the Amp block to crank the input level into the Amp block. Alternatively use a Filter or Volume block before the Amp block.
* '''Bright switch''' — engaging the Bright switch may increase gain with some models.
* '''Saturation''' — engage the Sat(uration) switch in the model.
* '''Pitch Follower''' — attach the Pitch internal controller to the Overdrive control. [https://forum.fractalaudio.com/threads/5-minute-tones-pitch-follower.152930/ Demonstration by Leon Todd]
* '''Gain Enhancer''' — this control simulates the acoustic reinforcement of a loud amp coupling into the guitar which also adds gain. [[Amp_block#OUTPUT_COMPRESSION_.2B_TYPE_.2B_THRESHOLD_.2B_CLARITY|More information]]
* '''Morph''': morph between gain settings using two amp blocks (Axe-Fx only) and Volume blocks. [https://www.youtube.com/watch?v=9ncGcU0QS2A Demonstration]
* Other possibilities:

<blockquote>(Jay Mitchell) "Cascade one amp block into another. Turn off "Sag" in the first one. Now you've got an extra preamp feeding your amp, which opens up an incredible spectrum of gain staging. For example, think Twin Reverb preamp, with Plexi tonestack set to "post," feeding a Plexi 2 with default settings. The possibilities exceed anything one person could hope to explore in a lifetime. You can get it awfully close. You want to minimize the effect of the preamp in Amp 2. To do this, set the 2nd Amp's Bright to off, MV to a high value and find a neutral setting for the tone controls in the 2nd Amp. Then use Drive in the 2nd Amp for your MV. The amp types you choose for this arrangement will make a huge difference, as will quite a few parameter settings."</blockquote>

<blockquote>(Jay Mitchell) "Start with Tape drive, set the clipping mode to "HV tube", Drive moderate, Level as appropriate for the amp block it's driving, and you'll have another tube gain stage, complete with EQ."</blockquote>

Adjusting gain on low notes only:

<blockquote>"If you want less distortion on low notes, there are several ways to achieve this:
# Use the Low Cut
# Increase Definition
# Increase Xfrmr LF.

The first two reduce low frequency content going into the preamp, the last one reduces it going into the power amp (there's a hidden low-cut between the preamp and power amp but the user doesn't have access to this). So it depends on where you are getting the distortion from. If it's mostly preamp distortion, use #1 or #2. Otherwise use #3. You can add bass back with the Depth knob or in the EQ page. The default settings are accurate for the amp being modeled. As amps become more modern, it seems people's taste agree with yours and many modern amps feature aggressive low-cut and then add bass back in the power amp. So what you are doing is "modernizing" your amp. For example, the HBE has a very high low-cut and then adds bass back with a fixed Depth circuit." [http://forum.fractalaudio.com/threads/warmth-from-6-0-to-9-0.59934/#post-747576]</blockquote>

Also:
* [https://forum.fractalaudio.com/threads/understanding-all-the-different-gain-controls.95018 Cliff's Tech Note about the different gain controls]
* [https://forum.fractalaudio.com/threads/wicked-wiki-4-adjusting-amp-gain.49193/ Wicked Wiki article]

==Clean up gain with the guitar==

<blockquote>"The amps clean up exactly like their analog counterparts. This is a common complaint with modelers because people use more gain because they listen at lower volumes. With a real amp the volume is loud which provides acoustic reinforcement to the guitar which enhances sustain. At lower volumes this is missing so people increase the gain." [http://forum.fractalaudio.com/threads/the-axe-and-guitar-volume-controls.145331/#post-1718891]</blockquote>

<blockquote>"It's actually one of the things we test when creating models. We even go beyond that. We compare the harmonic spectrum at various input levels as well to make sure the distortion characteristics change in the same way. And you can't do this with just a sine wave, you need to test both harmonic and intermodulation products." [http://forum.fractalaudio.com/threads/the-axe-and-guitar-volume-controls.145331/#post-1718918] </blockquote>

<blockquote>"Here's a little trick to enhance the "clean up with guitar volume knob" thing. In the Amp block go to the Dynamics page. Set the Compressor Type to Feedback. Turn up the Output Compression to taste. Notice that when you play harder the amp will distort more. Now you can use the Input Drive and/or Trim to reduce the input gain so that when you play softer or roll off the volume the amp will clean up. Real amps get this from power supply sag but this requires the power amp be driven hard which can get muddy. This trick allows you to get that same response without cranking the Master Volume." [http://forum.fractalaudio.com/threads/clean-to-mean-w-the-volume-knob.144394/]</blockquote>

<blockquote>"To increase the "clean up with volume knob" lower the gain, set the Compressor Type to Feedback and dial in a bit of Output Compression. You can also use the Gain Enhancer mode which results in a more dynamic sound." [https://www.thegearpage.net/board/index.php?threads/axe-fx-iii-effects.2260258/post-32648602] </blockquote>

[https://forum.fractalaudio.com/threads/the-modelers-dont-clean-up-with-the-volume-knob-myth.154557 Cliff's Tech note:]
<blockquote> "One often hears pundits proclaim "Modelers don't clean up when rolling off the volume knob". While this may be true of some products we actually test and compare this to our reference amps. We measure the THD and output volume at different stimulus levels to ensure that the response is the same. The reason for this myth stems from acoustic feedback. Real amps are LOUD. Modelers are usually played at much lower volumes.

Consider the following [https://forum.fractalaudio.com/attachments/volume_myth-png.58779 diagram]:

This is a block diagram of a model of what happens when playing a guitar with a speaker. Vg is the signal generator (your guitar). Sound waves from the speaker are fed back to your guitar and add to that signal. This signal is then attenuated by the the volume pot, k. The signal is amplified by the amp gain, A. Some portion of that signal is fed back, B.

The formula for a closed loop system like this is Acl = kA / (1 - kAB), where Acl denotes the closed loop gain. The open loop gain is given by Aol = kA.

Let's consider some examples.

In the first example let's assume the amp gain, A = 10, the volume knob is wide open, k = 1 and a mere 2% of the signal is fed back, B = 0.02. Using our formula we get:
Acl = 10 / (1 - 10 * 0.02) = 12.5.

The open loop gain is Aol = 10.

That tiny 2% of feedback has INCREASED the effective gain by 25% (!!!). If the amp is approaching distortion then it will get more distorted.

Now consider what happens if we roll of the volume knob a bit. Let's assume everything else is the same but we set our Log10A volume pot to halfway which means k = 0.1. Now we get:
Acl = 0.1 * 10 / (1 - 0.1 * 10 * 0.02) = 1.02
and Aol = 1

Rolling our volume knob to halfway now only gives a paltry 2% of gain increase for the same amount of acoustic feedback. So when the volume knob is wide open the amp has effectively almost 25% more gain than when rolled off halfway!

Now let's look at what happens when we lower the amount of feedback which would occur if we turned down the volume of our speaker. Let's leave everything the same but reduce our feedback to 1%.

Our first example with the volume pot wide open now becomes:
Acl = 10 / (1 - 10 * 0.01) = 11.1
Aol = 10

And our second example becomes:
Acl = 1.01
Aol = 1

So we see that the closed-loop gain is highly dependent upon the speaker volume. Simply reducing the speaker volume by 6dB lowers the effective gain increase considerably.

When playing with a loud amp the positive feedback from the speaker into the guitar effectively increases the gain of the amp when the volume control is wide open. As you roll the volume control off the amount of gain increase is lower. This gives the ILLUSION that the amp cleans up more when you roll of the volume but it's not the amp that is cleaning up, the signal into the amp is lowered more than if there were no feedback.

When using a modeler people almost always have the volume lower because amps are too loud. Lowering the volume reduces the feedback which in turn lowers the gain enhancement. To compensate people raise the gain of the model but now when you roll off the volume it doesn't clean up as much because the gain is higher. IOW, to compensate for the reduced feedback the user increases the gain, say, 25% to get the same effective gain as the loud amp but when rolling off the volume the amp gain is still 25% higher so it doesn't clean up as much.

P.S.
An interesting result occurs if we let B = 0.1:
Acl = 10 / (1 - 10 * 0.1) = 10 / 0 = infinity.
This is what happens for controlled feedback. The closed loop gain approaches infinity and the loop becomes unstable and oscillates. That's why controlled feedback is easier to obtain at higher volumes, the feedback coefficient is greater. Another way is to move closer to the speaker. Since sound pressure is inversely proportional to the square of the distance moving 50% closer results in four times the feedback!

You can simulate this by using the Output Compression control and setting the Compressor type to "Feedback". It won't simulate controlled feedback. It does a good job of simulating gain enhancement."</blockquote>

Cygnus SpectrumTrack:<blockquote>"SpectrumTrack(TM) ensures that the frequency response of the model matches the real amp at all levels of input excitation. If you've played other products you may notice that the response deviates if you roll down the volume on your guitar. For example, the ****** gets noticeably more midrangey when you roll off your guitar volume. The ***** gets thinner. Etc, etc. This error in response also manifests when varying your picking intensity, especially for low- to mid-gain tones. SpectrumTrack(TM) compares the model to the reference amp at a wide range of excitation levels and ensures that the model's response matches that of the reference amps." [https://forum.fractalaudio.com/threads/spectrumtrack™.173391/post-2099492] </blockquote>

==Bi-amping==

The Enhancer block and the Micro Delay / Mic Distance parameter in the Cab block let you create a stereo image out of a single mono guitar. Another approach is the Pitch trick in the Petrucci factory preset on the Axe-Fx III, FM3 and FM9. Or try this [https://forum.fractalaudio.com/threads/michael-dolces-ping-pong-trick.151065/#post-1797076 delay trick].

==Replicating the sound of Kemper amp profiles==

<blockquote>"The Axe-Fx III models are extremely accurate. The Kemper has its own vibe which a lot of people like. It's characterized by lots of midrange compression. You can replicate this on the Axe-Fx by setting the Output Compression type in the Amp block to Feedback and dialing in ~6 dB of compression. Adjust to taste. The distortion of the Kemper is smoother than a real amp as well. You can replicate this by decreasing the Power Amp Hardness." [https://forum.fractalaudio.com/threads/axe-fx-iii-clean-amp-sounds-compared-to-kemper-cleans.151497/post-1804532]</blockquote>

<blockquote>"Turn off all effects in the KP. Isolate the Cab in the KP. Then do an IR capture of it.
Turn on the Amp in the KP. Dial in an amp that's close. Be sure to listen with the guitar volume turned up and down as you (though the KP won't behave like the amp did in this test, it will help you hear the amount of gain and also the pre-EQ.) Then follow the cab with a Tone Match block if needed, using the instructions in the Tone Match Mini Manual. Method 2 is to use NO cab block in the Axe-Fx. Skip the IR capture and use a Tone Match block to achieve the match all at once." [https://forum.fractalaudio.com/threads/tonematching-kemper-and-capturing-irs.179681/post-2193681]</blockquote>

About profiling:
<blockquote>"Using neural networks is possible but training a NN takes hours and requires hardware that a consumer modeler would not have (i.e. inference accelerators). That said, my tests have shown that white-box modeling outperforms profiling and NN in terms of accuracy and aliasing. Whether that sounds "better" is subjective." [https://forum.fractalaudio.com/threads/iv-anywhere-on-the-horizon.184287/post-2273416]</blockquote>

==Noise, fizz, crackle, sizzle, intermodulation, crossover distortion==

Fizz and crackle are terms to describe certain things people hear when playing an amp model.

'''Fizz''' — high-frequency noise or hiss, which almost seems detached from the basic sound, floating above it. It's only there briefly after striking a chord or tone, like some kind of interference. Best heard when playing a model with power amp distortion.

'''Crackle''' — side-effect of the initial attack, which halts but not gradually, it kind of stutters before it stops. Best heard when playing a clean amp model at high master volume.

People play through their Fractal Audio amp modelers, hear fizz or crackle, and think there must be something wrong with the modeling or their settings. In fact, they are listening to the realistic equivalent of a real amp, because real amps also generate fizz and crackle. You need to listen very closely to the guitar speaker to hear it. That's why you'll hear it better through a modeler, because these emulate a close-miked guitar sound when using cabinet modeling.

Fizz and crackle attribute to the authenticity of amp modeling. They also help to make the guitar stand out in the mix.

<blockquote>"Fizz is desirable. Almost all high gain amps use a lot of feedback on the last triode stage to make it as "hard" as possible. This is typically done by using no cathode cap or a small cathode cap. You never see big cathode caps on the last stage of a high-gain amp. This gives lots of negative feedback and makes it clip harder. Another technique is to use negative feedback to the grid. This is done in 5150-based designs which makes the stage clip even harder. The last stage of a 5150 basically looks like a diode clipper. The harder the clipping the more overtones that are created and the better the tone cuts. Without those overtones your sound is lost in the mix. Amp designers know what they are doing. Trust them." [http://forum.fractalaudio.com/threads/fizz-is-good.67719/#post-833875] </blockquote>

<blockquote>"If you start trying to dial out what you call "fizz" and "artifacts" you're going to end up with a tone that doesn't cut. It might sound good to you but it won't fit in the mix. That fizz and sizzle is what makes those classic rock tones work. Listen to some isolated tracks of VH and AC/DC and you'll hear a ton of high-end sizzle. In the mix, however, it's not noticeable. If you remove it then the guitar sounds dead." [http://forum.fractalaudio.com/threads/tone-envy-a-case-of-the-fizzies.61661/#post-767039] </blockquote>

<blockquote>"Fizz on the decay is natural and it's what tube amps do. If you don't like it you can reduce the Triode Hardness but then it won't cut in the mix as well." [http://forum.fractalaudio.com/threads/tweaking-the-axe-fx-scratchyness.76600/#post-936024] </blockquote>

<blockquote>"The "fizziness" of clipping is determined by how "hard" the clipping is. There are three primary places that clipping occurs in a tube amp: the preamp tubes, the phase inverter and the power tube plates. Preamp tube clipping can range from soft to hard depending upon the design. Phase inverter (PI) clipping, which is actually the power tubes grids clipping, is very hard. Power tube clipping ranges from soft to hard depending upon the amount of negative feedback in the power amp. Preamp tube clipping is comprised of cutoff, which is soft, plus saturation, which tends to be hard. Actual saturation rarely occurs because most preamp stages are designed such that the grid clips before the tube enters saturation. Grid clipping is hard. Local negative feedback is used in the form of cathode caps to shape the response of a preamp stage. If there is no cathode cap then there is negative feedback at all frequencies which increases the hardness of the clipping. The last stage usually dominates the clipping. Some amps have no cathode cap on this stage, e.g. JCM800, and therefore have hard preamp clipping. The Axe-Fx II does not expose the negative feedback settings for the preamp stages to the user, these are hard-coded. Reducing the Triode Hardness parameter will soften the clipping more-or-less depending upon the particular amp model. In a typical tube amp the power tubes start to clip right about the same time the PI/grid clipping occurs. This is intentional so as to get the most power from the tubes. However some amps are intentionally mismatched as the designer's intent was to get more power tube clipping than PI clipping (i.e. Trainwrecks). The Transformer Match parameter adjusts the relative onset of power tube vs. PI/grid clipping. Lower values will cause the PI/grid clipping to occur before power tube clipping. Higher values will cause the power tubes to clip before the PI. Note that the power tube plates follow the impedance curve of the speaker so while the PI/grid may be designed to start clipping first, this only occurs in the midrange. At frequencies above 1 kHz or so the power tubes clip first since the voltage on the plates increases as a function of the speaker impedance. The first thing to clip tends to dominate as once you enter clipping the effect of clipping elsewhere is diminished. Negative feedback around the power amp attempts to linearize the transfer function. The more negative feedback the more the power amp is linearized. However this also causes the clipping to become harder. A power amp with no negative feedback will go into clipping softly. As you increase the negative feedback the "knee" gets sharper. The Damping parameter is the negative feedback control. Higher values give more feedback and harder clipping. Presence and Depth work by modifying the negative feedback. As you increase them the feedback gets less so by turning up the Presence you get softer clipping in the power amp. Therefore to decrease the hardness of the power amp clipping: reduce Damping, increase Presence, increase Transformer Match. To reduce preamp clipping hardness reduce Triode Hardness. There is no parameter exposed to adjust the PI hardness. HOWEVER, the relative hardness of clipping is not all that audible. You have to listen closely. The IR is far more important in the final result. Some IRs let through a lot more high frequencies and therefore sound more fizzy. Furthermore overanalyzing this is inadvisable. Many amps are specifically designed to clip hard as this gives a more aggressive tone that fits better in the mix. Some amps actually attempt to increase the hardness of the clipping as much as possible by using diode clipping or using very high values of negative feedback (i.e. Modded Marshalls, Camerons, 5150 III). Listening at low levels fools your ear. Our ears are more sensitive to midrange at low listening levels. This means we hear the clipping differently than when listening at the actual level the real amp would be generating." [http://forum.fractalaudio.com/threads/ghost-fizz.77539/page-7#post-947075] </blockquote>

<blockquote>"When listening to things at a low volume fizz will be more noticeable. Power amp distortion can be particularly fizzy but we don't notice it because the amp is usually really loud when the power amp is distorting." And: "I was sitting in my chair about 3 feet from a 4x12 A/B'ing a JCM800 to the prototype Axe-Fx II some years ago. I was astonished at all the grit and fizz coming from the amp. The model was way too smooth. I sat there just playing a major 3rd interval listening to the crackle from the amp whereas the model did not have this. The big thing was the crackle on the note decay. The amp sounded like frying bacon as the note died out. It would go "gcchhhh crackkklleee bzzzzzz". I grabbed other amps and noticed the same thing from all of them. It was then that I realized I had a lot of work to do and spent a couple years researching how to make a digital amp modeler replicate all that stuff. All that stuff, though, gives you note separation and helps you cut in the mix. It turns out that tube amps do strange things when overdriven and those old concepts of soft clipping circuits are wrong. Tube amps get nasty and clip very hard and very asymmetrically." [http://forum.fractalaudio.com/threads/getting-a-lot-of-fizz-when-turning-the-cab-sim-off-and-going-to-real-cab.79862/#post-971125]</blockquote>

<blockquote>"I prefer the "fizz" on probably because I grew up with it. I just like the extra grit. When you're playing in a group context that grit seems to make the guitar cut better and fills out the sound. Without it things sound sterile. I spent months trying to capture that. One day one of my employees came by the lab while I was working on the new algorithms. I was trying to explain the grit to him that I heard in my JCM800. "Hear that sizzle on top of the notes? Hear that raspy, bacon frying sound? That's what modelers are missing." So I spent months figuring out where that came from and how to replicate it. All IMHO." [http://forum.fractalaudio.com/threads/so-thats-what-you-were-calling-fizz.45253/#post-592172] </blockquote>

<blockquote>"The simplest way to remove fizz is turn down Master Bias Excursion." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317936]</blockquote>

<blockquote>"The "buzziness" of IM is a function of the "hardness" of the clipping circuit. The first thing you need to do is determine what is distorting: preamp or power amp. Power amp distortion is typically harder than preamp distortion due to global negative feedback. If you are using a modern amp model, i.e. something with a Master Volume, then there is a very good chance you might be overdriving the virtual power amp. In this case simply lowering the Master Volume will reduce IM. If it's preamp distortion then you can reduce Preamp Hardness or experiment with the Preamp Bias to change the distortion character. The Axe-Fx II is extremely accurate. Understanding how real amps work will allow you to adjust things to achieve your ultimate tone. To put this to rest (again, for the umpteenth time): http://www.fractalaudio.com/tmp/blues_jr.mp3. One clip is the amp, the other is the model. All controls set the same. The reason that it's more "noticeable" with modelers is that there is a lot more high frequency content in a typical IR. When you listen to your tube amp through its speaker you are in the far field and usually somewhat off-axis. There is less high frequency content reaching your ears compared to what a microphone records. Go put your amp in an isolation room and listen to it through the control room monitors. You'll be astonished at what you hear." [https://forum.fractalaudio.com/posts/1374762] </blockquote>

<blockquote>"The "buziness" of IM is a function of the clipping hardness. As I stated before you need to determine whether you are getting power amp or preamp distortion. In general preamp distortion is softer but not always. It depends on the circuitry. You can reduce the clipping hardness with the Preamp Hardness and Power Amp Hardness parameters. This ONLY changes the shape of the virtual tube though. The final clipping behavior is also dependent on the surrounding circuitry which the user has no control over. For example a JCM800 preamp actually clips pretty hard because there is no bypass cap on the last triode's cathode. Therefore there is a lot of local negative feedback on that stage which makes the resulting transfer function "harder". In contrast a 1959SL Plexi has a bypass cap which softens the transfer function. Power amp clipping behavior is dependent upon the amount of global negative feedback. The less feedback the softer the distortion. That's why "Class A" amps have softer clipping as they have no negative feedback. Fenders, otoh, typically have 3-6 dB of gain reduction which makes the power amp clip harder. Therefore you can reduce negative feedback to soften the clipping behavior if your distortion is coming from power amp overdrive." [http://forum.fractalaudio.com/threads/behind-note-buzz-help.114938/page-2#post-1374519] </blockquote>

<blockquote>"Crossover distortion occurs when you play very lightly. To really hear the effect of crossover distortion turn the Power Tube Bias parameter all the way down and play lightly. You'll hear a scratchy sound. This occurs because the waveform gets a kink in it at the point where one tube stops conducting and the other starts. Some people actually like the sound and I've heard rumors that EVH liked his amps biased cold to get some crossover distortion. Output transformers can create a type of crossover distortion as well due to the BH curve being nonlinear at the origin." [http://forum.fractalaudio.com/threads/does-anyone-else-get-a-crackling-sound-out-of-their-frfr.120078/page-4#post-1429273] </blockquote>

<blockquote>"It's called intermodulation. No only do actual amps do this, ANY device that distorts the signal will do this." [http://forum.fractalaudio.com/threads/unwanted-ring-mod-sounds-when-playing-double-stops.140598/#post-1666025] </blockquote>

<blockquote>A "Tweed" amp has a cathode biased power amp. Most Fenders are fixed bias but some of the earlier ones, like the 5E3, are cathode biased. Most cathode biased amps (often erroneously referred to as Class A) will go into Class-B operation when driven. Class-B operation creates crossover distortion. The reason a cathode biased amp goes into Class-B operation is because the capacitor in the cathode bias network charges up when the tubes conduct. For example with no input signal the voltage on the cap might be, say, 10V. When each tube conducts more current flows from the supply which charges the cap up and increases its voltage to, say, 20V. The bias voltage has effectively doubled which means the tubes are now biased very cold and the amp runs Class-B. When you stop playing the bias voltage settles back to 10V. Start playing again and the cathode cap charges up again. The time constant to charge the cap is on the order of milliseconds so it takes some time, it's not instantaneous. Some amps use separate cathode networks to reduce the amount of bias shift, i.e. Matchless, Bad Cat, etc. but this increases cost. The sound of Class-B operation is a raspy, fizzy, crackly sort of sound as crossover distortion creates a very different spectrum than clipping. Some people like the sound and there are actually pedals that intentionally create crossover distortion. Rumor has it that EVH liked his amps biased cold so he would get more crossover distortion. Crossover distortion is mostly in the high frequencies. When listening to the proverbial "amp in the room" the high frequency rolloff of the speaker will mask it to a great extent. Close micing an amp yields a lot more high frequencies which will make crossover distortion more noticeable. If you have an Axe-Fx you can experiment with the bias shift in these types of amps via the P.A. Cathode Resistance parameter. Turn it up and the bias will shift more resulting in more crossover distortion as the power amp is driven. Turn it down and the bias will not shift as much and the amp will remain in Class-AB operation longer. You can tell if an amp is cathode biased by the default value. If it is 0.0% then it's a fixed bias amp, otherwise it's cathode biased. Some amps exhibit this more than others. The Suhr Badger has a lot of bias shift but it's still a great sounding amp, probably because the conjunctive filter rolls off the high end which helps mask the crossover distortion." [https://www.thegearpage.net/board/index.php?threads/squirrel-comes-back-in-spades-in-helix-2-81-tweed-nrm-lol.2077647/page-16#post-29183540]</blockquote>

<blockquote>"The AC power supply is modeled and any hum and ghost notes in the power amp will be reproduced. What is not reproduced is hum due to AC heaters, thermal noise, and other sources of interference. These are considered objectionable." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-15-00-public-beta-1.168197/post-2020785]</blockquote>

<blockquote>"That's what amps do. You don't hear it through a guitar cab typically but using close-mic'd IRs it's more noticeable. You can reduce it by turning on the Plate Suppressor diodes. Trainwrecks have plate suppressor diodes for just this reason." [https://forum.fractalaudio.com/threads/note-decay-crackle-sizzle-noise.193575/post-2407689]</blockquote>

[http://en.wikipedia.org/wiki/Intermodulation Wikipedia: Intermodulation]

<blockquote>(crackling sound through FRFR) "That's what amps sound like. Go put an amp in an isolation room with an SM57 on it. Listen in the control room. You'll hear the same thing. You don't hear it as much using a real guitar cab because the high frequencies are rolled off which softens the sound." And: "You're probably just hearing "tube crackle". This is most noticeable when letting chords ring out as the sound decays. It's more noticeable with FRFR because of the extended high frequency response of near-field IRs. Tube crackle occurs when playing more than one note typically. When you play multiple notes (as in a chord or even a diad) the amplitude "bounces" around as the multiple notes reinforce each other or cancel each other. The result is an envelope that is not uniform. The peaks of the waveform clip but the troughs do not. This causes a crackling sound when you get on the edge of distortion because the points at which distortion occurs are far enough apart in time to be audile. You can reduce it by softening the distortion. Reducing Preamp and/or Power Amp Hardness will reduce the crackling but this will deviate from authenticity." [http://forum.fractalaudio.com/threads/does-anyone-else-get-a-crackling-sound-out-of-their-frfr.120078/page-4#post-1429200] </blockquote>

<blockquote>"Tube crackle is most noticeable when letting chords ring out as the sound decays. It's more noticeable with FRFR because of the extended high frequency response of near-field IRs. Tube crackle occurs when playing more than one note typically. When you play multiple notes (as in a chord or even a diad) the amplitude "bounces" around as the multiple notes reinforce each other or cancel each other. The result is an envelope that is not uniform. The peaks of the waveform clip but the troughs do not. This causes a crackling sound when you get on the edge of distortion because the points at which distortion occurs are far enough apart in time to be audile. You can reduce it by softening the distortion. Reducing Preamp and/or Power Amp Hardness will reduce the crackling but this will deviate from authenticity." [http://forum.fractalaudio.com/threads/does-anyone-else-get-a-crackling-sound-out-of-their-frfr.120078/page-2#post-1428924] </blockquote>

Fractal Audio's processors do not create or generate noise by themselves. Noise with high gain amp models is noise which enters the processor at the input and is then amplified by the processor.

<blockquote>(Axe-Fx II) "On the Ultra I would use the gate on high gain patches but I find I don't need it now. I did some measurements and the II is at least 10 dB better SNR." [http://forum.fractalaudio.com/threads/funny-thing-at-rehersal.41117/#post-552329] </blockquote>

<blockquote>"There are noise "reduction" techniques but all alter the desired signal in some way. Noise gates are among the most useful for our particular needs. Digital cameras use various techniques based on the statistics of the image (i.e. if an area of the image is monochromatic heavier filtering is applied). The Intelligent gate in the Axe-Fx uses some crude statistical processing where the statistics are based on the typical stats of a typical guitar. IOW, noise reduction is destructive. You can't beat the laws of physics. So you can't remove noise without somehow altering the original signal." [http://forum.fractalaudio.com/threads/eliminating-noise.109312/#post-1308096] </blockquote>

<blockquote>"The amp model doesn't add noise, it just amplifies it." [http://forum.fractalaudio.com/threads/eliminating-noise.109312/#post-1308121] </blockquote>

<blockquote>"To get the best noise performance it is important that the Instr In trim is set correctly in the I/O > Input menu. Set this as high as possible without clipping the input." [http://forum.fractalaudio.com/posts/956435] </blockquote>

<blockquote>"Guitars make noise. Amplifiers amplify that noise. A noise gate will remove that noise WHEN YOU ARE NOT PLAYING. Expecting a power conditioner to remove noise at the guitar is illogical. There are two types of noise guitars make: thermal noise (hiss) and interference (which isn't technically noise). You can't do anything to reduce the hiss aside from reducing the temperature considerably which isn't practical. You can reduce the bandwidth which will reduce the apparent noise but it may make the guitar sound dull. You can reduce interference (hum and buzz and other periodic noises) in two ways: at the source and at the receiver (the guitar is the receiver). To reduce it at the source you have to find the source(s) and shield them, reduce the loop area, etc. At the receiver you reduce interference by shielding or using humbucking pickups or ideally both. Computers are significant sources of interference. Computers with windows are especially bad. The inverse square law tells us that one way to reduce interference is to simply move further away from the source." [https://forum.fractalaudio.com/threads/weird-high-frequency-hiss.161463/post-1934363]</blockquote>

<blockquote>"Firmware cannot add or remove noise. Anyone having noise problems needs to look elsewhere in their system." [https://forum.fractalaudio.com/threads/fw-8-00-noise-issue.154243/post-1835202]</blockquote>

<blockquote>"They can hum do to tube imbalance but they don't add any thermal noise. [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-00.157866/post-1884224]</blockquote>

<blockquote>"Noise isn't modeled. All preamp tubes have separate heating elements. This is called "indirect heating". Directly heated cathodes are no longer used except for rectifier tubes. Regardless direct or indirect heating has no effect on the noise floor. Noise is due to the random motion of electrons in a conductor. You can't "reject" it. You can lower the noise floor by keeping resistor values low (since noise is proportional to resistance) and by paralleling the input triode. No modeler models noise. The dominant source of noise in any amp, whether real or virtual, is usually your guitar (or rather its pickups). A 10K ohm pickup will have -114 dBv of noise at room temperature. Modern A/D converters, when properly designed, can exceed this so the dominant source of noise is your guitar. This noise is then amplified by the amp (that's why they call them amplifiers). If the amp has, say, 60 dB of gain then that noise is now -114 + 60 = -54 dBv. Gain it up another 20 dB with the power amp and now you're at -34 which can be quite audible. The situation gets worse as you roll off the volume in your guitar as you then introduce more resistance. A typical guitar pot is 500K ohms with an audio taper. If you roll the volume pot down to 8 or so you can easily introduce another 100K of resistance into the signal path. This will increase the noise to -94 dBv which becomes -14 after amplification. Really noticeable then. Bottom line: if you have too much noise you have too much gain. Learning to play with less gain will improve your technique and the quality of your tone. Gain just masks poor technique and reduces clarity, string separation and dynamics." [http://forum.fractalaudio.com/threads/which-models-have-the-lowest-noise.124597/#post-1481877] </blockquote>

<blockquote>"There's not a modeler in existence that adds noise to match the noise of the amp being simulated. Noise is undesirable regardless of "realism". Hum and ghost notes are sometimes modeled but thermal noise never is primarily because the amount of thermal noise is partially dependent upon the resistance of the source (guitar pickup) which is a variable. Furthermore any modeler exhibiting that much thermal noise would be roundly criticized for being excessively noisy." [http://forum.fractalaudio.com/threads/ooooh-charts-and-graphs.135900/page-5#post-1609949] </blockquote>

<blockquote>"Gain doesn't add noise, it amplifies noise. SNR is determined by the hardware. There is equivalent noise at the input (engineering term is Noise Referred to Input). This is due to Brownian motion (thermal noise, also known as Johnson noise). That noise gets amplified. The amp block is digital and adds no noise. It only amplifies (that's why it's called an amplifier). To prove this to yourself, go into a noisy preset and disconnect the input to the amp block. The noise will go away because the amp block doesn't add noise. If it added noise you would still have noise at the output." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-19-00-beta-3.180388/post-2207022]</blockquote>

<blockquote>"Crackliness of the note decay is dependent upon how hard the clipping is. If it's the power amp clipping this is dependent on the hardness of the power tubes (Power Amp Hardness) and the amount of negative feedback (less = softer). If it's the preamp clipping it's dependent on the hardness of the preamp tube (Preamp Hardness) and the negative feedback around the last stage (not user adjustable). A JCM 800, for example, crackles like crazy because there is a lot of feedback on the last preamp stage (since there is no cathode bypass cap). A Friedman BE-100 preamp is similar to a JCM 800 but it has a cathode bypass cap on the last stage and the resulting distortion is much smoother." [http://forum.fractalaudio.com/threads/crackling-sound-in-the-tail-off.136170/#post-1612621] </blockquote>

<blockquote>"Blocking distortion occurs in older designs due to grid conduction. The grid gets forward biased which causes a net offset to develop on the coupling capacitor which, in turn, shifts the bias point. Modern designs incorporate various means of mitigating this (grid stoppers, for example). Some bias excursion is desirable though as without it the distortion can be "sterile". [http://forum.fractalaudio.com/threads/is-there-something-wrong-does-this-sound-normal-odd-distortion.138302/#post-1640780] </blockquote>

<blockquote>"Intermodulation is inevitable. To reduce it, reduce the gain, set bias points to 0 and reduce bias excursion". [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-15-01.168349/post-2023524]</blockquote>

<blockquote>"To reduce/eliminate crossover distortion increase Power Tube Grid Bias. A value of 1.0 will have no crossover distortion." [https://www.thegearpage.net/board/index.php?threads/axe-fx-iii-effects.2260258/post-32648602] </blockquote>

[http://forum.fractalaudio.com/threads/papery-buzz-under-some-models.149193/page-2#post-1772639 Forum discussion]

Aiken White Papers:
* [http://www.aikenamps.com/index.php/what-is-crossover-distortion Crossover distortion]
* [http://www.aikenamps.com/index.php/what-is-blocking-distortion Blocking distortion]

==Aliasing==

The Axe-Fx III lets you set the oversampling mode for Amp and Drive blocks through the Oversampling Mode parameter in the [[Setup menu#Global Settings menu|Setup menu]].

<blockquote>"Aliasing in important in every situation. Aliasing is the creation of harmonically unrelated and undesirable tones in the audible spectrum. Aliasing is most easily heard when playing single notes. It is masked when playing chords but raises the effective noise floor causing a loss of clarity. IME it also causes rapid ear fatigue. A real amp doesn't alias and good modelers have minimal aliasing. The most common way to reduce aliasing is to increase the sample rate either natively or by oversampling. You can also reduce aliasing using antiderivatives but this only works in very specialized cases when using waveshapers." [https://thegearforum.com/threads/modelers-and-aliasing.1815/post-59724]</blockquote>

<blockquote>"The only way to avoid aliasing is to increase the sample rate. Double the sample rate and you double the computational cost. At a minimum. Often times this will quadruple the computational cost because it becomes O^2 operations. Anything that does convolution-like processing (like a NN) will end up with O^2. I.e., if you double the sample rate the number of coefficients in an FIR doubles so you have to do twice as many operations for the FIR at twice the rate. Anything that generates significant distortion should be oversampled (assuming 44-48kHz native sample rate) by at least 4x. That's an absolute minimum IMO. This would cause an increase of 16x computations." [https://thegearforum.com/threads/modelers-and-aliasing.1815/post-59819]</blockquote>

<blockquote>"Any time you have a nonlinear transfer function you create distortion. In guitar gear the transfer function is usually some sort of clipping behavior. At the limit this turns a sine wave into a square wave. A square wave has harmonics that extend well into the ultrasonic range. If you don't oversample enough those harmonics alias into the audible spectrum. No amount of hand-waving changes that. The correct thing to do is to increase the sample rate and then downsample after all the processing is done." [https://thegearforum.com/threads/modelers-and-aliasing.1815/post-59845]</blockquote>

See also: [[Amp_block#Number_of_Amp_blocks|Number of Amp blocks]].

==Glossary of amplifier terms==

Aiken Amplification maintains a collection of very informative technical documents:
* [http://www.aikenamps.com/index.php/white-papers Aiken Amplification: White Papers]

Among these is a glossary of common amplifier terms, which is also included in [https://books.google.com/books/about/The_Guitar_Amp_Handbook.html?id=N9hAviH6gqEC Dave Hunter’s "The Guitar Amp Handbook"]. Make this your first stop when looking for a short explanation of something amp-related.
* [http://www.aikenamps.com/index.php/a-glossary-of-common-amplifier-terms Aiken Amplification: Glossay of common amplifier terms]

==Tube amplifiers explained==
Recommendations:
* [https://books.google.com/books/about/The_Tube_Amp_Book.html?id=JT1I7Ld76YsC The Tube Amp Book (Aspen Pittman)]
* [https://books.google.com/books/about/The_Guitar_Amp_Handbook.html?id=N9hAviH6gqEC The Guitar Amp Handbook (Dave Hunter)]
* [https://books.google.com/books/about/Amps.html?id=NgG8bmBayLwC AMPS! The Other Half Of Rock ‘n’ Roll (Ritchie Fliegler)]

==Tricks==

[[Amp_block#INPUT_TRIM | Simulate Low and High inputs of an amp]]

[[Amp_block#POWER_TUBE_GRID_BIAS | Run an amp in Class-A mode]]

[[Amp_block#POWER_TUBE_MISMATCH | Mismatch power tubes on purpose]]

[[Amp_block#POWER_TYPE | Get rid of ghost notes]]

[[Amp_block#SUPPLY_SAG | Change the rectifier type between tube and solid-state]]

[[Amp_block#LOW FREQUENCY + LOW FREQUENCY RESONANCE | Make a guitar cabinet resonate with a solid-state amp]]

[[Amp_block#OUTPUT_COMPRESSION_.2B_TYPE_.2B_THRESHOLD_.2B_CLARITY | Enhance the acoustic coupling at low volume levels]]

=Parameters=

[[image:Amp block.PNG|450px]]

The list of parameters below follows the editor's page structure.

=General=

==INPUT SELECT==

From the Owners Manual:
<blockquote>
"The Amp block processes audio in mono. This control determines how incoming stereo signals will be processed. You can input only “LEFT” or “RIGHT” channels, or “SUM L+R” (the default setting)."
</blockquote>

Adjust this to make two Amp blocks handle each side of a stereo signal separately. Or when using a single preset with two guitars, each with its own Amp block (FM3: n/a). Or to keep the stereo spread of a stereo delay placed before the Amp blocks.

==(OUTPUT) LEVEL==

The Output Level parameter in the Amp block controls the outgoing level of the Amp block. It has no effect on tone or gain.

It's also the recommended control to set the overall level of the preset, to match it to other presets and to prevent digital clipping.

This parameter can be directly controlled through a switch, assignable in the editor.

Fractal Audio explains:
<blockquote>
"The amp block is always the place to set your volume. The Level control is repeated at several places in the amp block menus for convenience so you don't have to keep switching pages. The Level control has no affect on the tone." [http://forum.fractalaudio.com/threads/so-many-volumes-options.55340/#post-698522]
</blockquote>

About leveling the output of the amp models:

<blockquote>"You can never make the amp models the same volume for the same settings. It's a mathematical impossibility. It also depends on the guitar. If you make two amp the same volume at, say, all knobs at noon, then they may be drastically different if you simply change the Drive from 5 to 7. For example, take a Twin Reverb and a Dual Rectifier and match the volume with all knobs at default. Now increase the Drive to 7.0. The Dual Rec won't get much louder, just more distorted. The Twin Reverb will get much louder. Secondly, the signal strength from the guitar will affect the volume. If you were to make the volume the same between two different amp models and then use a guitar with weaker/hotter pickups the volume may be quite different."</blockquote>

Watch "[https://www.youtube.com/watch?v=BWQ65u39nM8 AxeFxTutorials: Preset Leveling: Master Volume vs Level in the Amp Block]" to learn more.

=Authentic / Ideal=

Read "[[Amp_block#Authentic_or_idealized_amp_controls| Authentic or idealized controls]]" for more information.

==INPUT TRIM==

From the Owners Manual:

<blockquote>
“Amps without an Overdrive control (below) will display Input Trim instead. This allows you to adjust for more or less preamp gain than the actual circuit being modeled. This is different from the Input Drive in that it does NOT interact with the surrounding circuitry to change frequency response as it is varied. In short, use Input Trim to adjust gain without also changing tone.”
</blockquote>

This lets you adjust the range of gain of the amp by increasing or decreasing the signal level at the input of the Amp block. It's the same as Amp Gain in the system settings of the Axe-Fx II and AX8, and Input 1 Gain in the I/O menu on the Axe-Fx III and FM9, but Input Trim operates per preset instead of global. It's also the same as the "neutral" Input Boost type, but Input Boost can't lower the signal.

Values above 1 increase the level. Values below 1 lower the level. 1 is unity gain, 2 is twice.

Input Trim is different from Gain in that it does not interact with the surrounding circuitry to change frequency response as it is adjusted. Use Input Trim to adjust gain without also changing tone.

Fractal Audio explains:

<blockquote>
(Axe-Fx II) "They (Amp Gain and Input Trim) are basically the same thing. The global amp gain has a smaller range as it's designed to be for fine-tuning between guitars whereas the local trim allows you to radically alter the response of the model. The local trim is equivalent to -20 to +20 dB." [http://forum.fractalaudio.com/threads/input-trim-global-amp-gain.40418/#post-545862]
</blockquote>

If the real amp has two inputs (f.e. Low and High), the model is based on the High input. Set Input Trim to 0.500 to get the equivalent of the Low input.

To translate Input Trim values to dB, use this formula: "20 * LOG10(trim value)". In other words: calculate the LOG10 result of the input trim value, and multiply this with 20. Use the LOG10 function on a scientific calculator. Examples:
* Input Trim at 0.500 = -6dB, because: 20*LOG10(0.5)
* Input Trim at 4 = 12dB, because: 20*LOG10(4)

In the Input Trim's modifier menu, a controller can be attached to create a variable boost. This includes [[Scene controllers]]. See "[http://forum.fractalaudio.com/threads/scene-controller-accuracy-for-input-trim.127292/#post-1514686 Translate scene controller settings to Input Trim values]" for more information.

Fractal Audio explains:

<blockquote>
"You might want to convert the Input Trim parameter to dB if you're used to thinking of it that way. As a rule of thumb, every 2x multiplier = +6dB boost. In other words, Input Trim = 4.0 produces a +12dB boost." [http://www.sengpielaudio.com/calculator-db.htm Handy calculator]
</blockquote>

<blockquote>
"Input Trim is something you shouldn't play with normally unless you want to deviate from the actual amp. Input Trim allows you to reduce or increase the gain of the virtual amps input buffer. This is analogous to changing the type of tube for V1 in an actual amp. Some people like less gain for V1 so will replace a 12AX7 with a 12AT7. Some people want a little more gain." [http://forum.fractalaudio.com/threads/new-10-10-firmware-thoughts.71497/page-3#post-877347]
</blockquote>

<blockquote>
"The Axe-Fx II contains a parameter known as "Input Trim". This is just a straight gain control at the very front of the amp block. It has a range of 0.1 to 10.0 (-20 to +20 dB). So what use is a straight gain control at the front? Doesn't the w do the same thing? The short answer is "no". The long answer is "probably not". On many amps the Drive knob, which may also be called Gain or Volume, has what is known as a "bright cap" across the physical potentiometer. This capacitor shunts high frequencies around the pot so that the Drive control is not a straight gain. It has an associated frequency response. As the Drive is turned down more high frequencies are shunted around the pot which results in a net treble boost. If the Drive is turned all the way down the treble boost is maximum, if it is turned all the way up the treble boost is zero. The roots of the bright cap are due to manufacturers trying to compensate for different types of guitars. Guitars with single coil pickups tend to brighter but with less output. The user would then turn the Drive knob high on the amps. Conversely a guitar with humbuckers has more output but sounds darker. To compensate the user would typically turn the Drive down. This will result in a treble boost compensating for the darker response. The Input Trim control allows one to fine-tune the amount of treble boost first and then adjust the amount of distortion. So it is probably more correct to think of the Drive control as a combination Drive/Treble control. With this in mind experiment with the Drive control combined with the Input Trim. Indeed some manufacturers have actually implemented separate Drive and Trim controls on their amplifiers. For example the Fryette (VHT) Deliverance has two controls: a Gain knob and a Cut knob. The Gain knob has a bright cap across it while the Cut knob is just a straight volume adjustment. The purpose of these two knobs is exactly as described above." [https://forum.fractalaudio.com/threads/input-trim.81116]
</blockquote>

<blockquote>
"The Input Trim control allows you to adjust the input attenuation without changing the frequency response. If you turn down the Input Drive and the model has a bright cap the amp will get brighter. Now you may like the brighter tone but wish there were more gain. Input Trim allows you to increase the gain without changing the tone. Conversely you may like the darker tone with Input Drive set high but wish there were less gain. In this case you can lower Input Trim. Most real amps do not possess an Input Trim control. Instead they usually have a switch or two input jacks that select between a high-gain and low-gain input. Almost invariably the difference between these two jacks is 6 dB. All the Axe-Fx amps are modeled using the high-gain input or switch position (if any). To simulate the low-gain input set the Input Trim to 0.5 which is 6 dB less". [https://forum.fractalaudio.com/threads/understanding-all-the-different-gain-controls.95018/post-1138073]
</blockquote>

<blockquote>
"It controls the voltage divider into V1. Many amps, for example, have two 68K resistors feeding V1. If you plug into the High input the resistors are in parallel and the gain is 1.0. If you plug into the Low input the resistors are in series and the gain is 1/2. Input Trim is a more flexible way of accomplishing the same thing but without being constrained to only two gain values."
</blockquote>

<blockquote>
"All the models assume the "Hi" input on the amp was used if there are multiple inputs. If the amp has a Lo input this is typically half the sensitivity so you would set Input Trim to 0.5 to replicate. The beauty of Input Trim is you can set it to any value you like rather than being stuck with a switch with only two values." [http://forum.fractalaudio.com/threads/ax8-clean-tones-input-trim-is-the-key.120261/#post-1431111]
</blockquote>

<blockquote>
"Be sure to set your Input Trim properly. If you are using single-coil pickups then you want to increase the Input Trim. This will optimize the S/N Ratio. With a properly optimized SNR the Axe-Fx has less self-noise than your guitar." [http://forum.fractalaudio.com/threads/best-low-watt-amp-model-to-build-do-it-all-preset-by-altering-guitar-volume-knob.122796/#post-1460865]
</blockquote>

<blockquote>
"0.5 is equivalent to using the Low input jack on amps. If you are using high-output pickups it's often better to use the Low input to get into the sweet spot of the bright cap. [https://forum.fractalaudio.com/threads/the-modeler-equivalent-to-alternate-guitar-tunings.155649/post-1853194]
</blockquote>

==GAIN + OVERDRIVE + MASTER VOLUME==

'''About Gain and Master Volume'''

NOTE: "GAIN" is the same as "Input Drive".

Vintage amps don't have separate gain (drive) and master volume controls. Therefore, Master Volume defaults to "10" in models which are based on these amps. Use Gain to control the amount of preamp gain/distortion as well as volume on non-Master Volume amp models.

Treble peaker circuits found on the gain or volume control on many amps are also modeled. This can be heard as the low frequencies are attenuated more than the highs when the gain is turned down (and vice versa).

Fractal Audio explains:

<blockquote>
"For clean tones the Drive control should be set fairly low and the Master set very high. On a real "Blackface", for instance, the Master is essentially maxed since that amp has no master volume. A Blackface typically achieves full power at around 10-11 o'clock on the volume (Drive). It's also insanely loud. Beyond that everything starts to saturate and clip. If you set the Master low and the Drive high, for clean tones, the low end will tend to get muddy. Good cleans are obtained with little, if any, preamp distortion and a nice amount of power amp distortion. Power amp distortion has a much different character and tends to be glassy and bouncy. Preamp distortion is rougher and more compressed." [https://forum.fractalaudio.com/threads/power-amp-settings-depth-damp-sag.56116/post-706835]
</blockquote>

<blockquote>
"The real key is to adjust the relative amounts of each. You want to balance preamp and power amp distortion for the best tone. What I do is start with the MV low and turn up the drive until I get the desired amount of gain and sustain. Then turn up the MV until I get the desired compression. Then fine-tune each." [http://forum.fractalaudio.com/threads/pre-amp-vs-power-amp-distortion-in-axefxii.46055/#post-601681]
</blockquote>

'''Master Volume'''

From the Owners Manual:

<blockquote>
“The almighty Master Volume is a very important control. It determines the distortion and dynamics characteristics of the power amp simulator, and its setting at any moment can dramatically change the amp’s sound. As it is turned up, the tone controls will have less influence, and the sound will have more “bloom” and touch sensitivity. Settings for Master don’t necessarily correspond to knob positions on the amp being modeled. With a little experimentation, you will learn to dial in different great sounding Input Drive and Master combinations.

When you select an amp type, the Master will change to an appropriate/typical setting for that amp. If a real amp doesn’t have a Master, the “correct” setting will be applied i.e. “10”, or “wide open.”

* At high settings, less gain is usually required, especially for high-gain types.

* Amps designed for preamp distortion will typically sound great with the Master set low to prevent the tone becoming muddy or noisy. This includes the “USA Lead” types and others.

* Amps with negative feedback tend to have “crunchier” power amp distortion, which can get “raspy” when driven too hard. Experiment with the interactivity of Negative Feedback and Master on distortion tone.

* With Power Amp Modeling disabled, either globally or in one specific block, Master Volume becomes a simple level control with 40 dB of range.

* If more power amp gain is desired, Master Volume Trim in the Advanced menu can be used.”
</blockquote>

<blockquote>
(Axe-Fx II) "Amp models now default to a starting Master Volume setting when selected. Also, the proper setting for non-MV amps is now a Master Volume setting of 10.0. Non-MV amps, therefore, will default to a value of 10.0 when selected. If more MV drive is desired for non-MV amps, the new MSTR VOL TRIM parameter in the Advanced GUI page can be used to increase (or decrease) the Master Volume. The starting MV value for non-MV amps is roughly the “sweet spot” for the amp. This is the point where the power amp starts to contribute to the tone and feel of the amp. Decreasing the MV will typically cause the amp to get brighter and less compressed and increasing the MV will cause the amp to get more midrange focus and more compressed. As always, your ears should be your guide."
</blockquote>

<blockquote>
(Axe-Fx II) "The amp modeling improvements have resulted in a significantly increased “sweet spot” for the Master Volume control. Previous advice to keep the Master Volume low for high-gain amp types no longer applies and, in fact, increasing the Master Volume can result in better tone (more bloom and swirl) and much better feel (due to power supply sag). Therefore most non-MV amps now default to a higher value than previously. This may result in louder preset volume which will necessitate reducing the Output Level to compensate."
</blockquote>

The MSTR VOL TRIM parameter in the Advanced GUI page can be used to increase (or decrease) the Master Volume.

Fractal Audio explains:

<blockquote>
"Just multiplies the MV by the amount. You only need to use it if you want more power amp drive and your MV is already at 10. IOW, if MV is 10 and you set MV Trim to 2.0 then the MV will be 20." [http://forum.fractalaudio.com/threads/master-volume-trim.67870/#post-834697]
</blockquote>

<blockquote>
(before "Cygnus" amp modeling) "Master Volume tapers are NOT matched. If they were the amp volumes would jump all over the place when you switched amp types. IIRC I use a Log10A for the MV." [http://forum.fractalaudio.com/threads/axe-fx-ii-firmware-version-12-04-public-beta.80497/page-17#post-978667]
</blockquote>

<blockquote>
"The Master Volume (MV) DOES affect the tone. It sets the level into the power amp modeling. The Level control has no affect on the tone. For MV amps, i.e a 5150, adjust the MV until the desired amount of power amp distortion is obtained. Most MV amps rely on preamp distortion and don't produce much power amp distortion. If you turn the MV up too high on them the tone will get muddy and flubby. Non-MV amps rely primarily on power amp distortion so you need the level into the power amp to be hot enough to push the power amp into distortion." [http://forum.fractalaudio.com/threads/so-many-volumes-options.55340/#post-698522]
</blockquote>

<blockquote>
"I just start low and bring it up until I get the desired compression. Then I chug the E string and if it's too buzzy or flubby I drop it down a bit. For tight, high-gain stuff you want to keep it low. For liquid, spongy tones you want to set it higher."
</blockquote>

<blockquote>
"MV is the most important Amp block control for tone. You have to find the sweet spot. Start at 3 and increase until desired compression is reached. Stock presets are set to sweet spots, subjectively (based on the guitar used and personal opinion). Do not use MV for volume and don't turn it up too much (unless it's a non-MV amp). If an amp has Input Drive and Overdrive controls, use Input Drive for tone shaping and Overdrive as a flat gain control."
</blockquote>

<blockquote>
"As you increase the MV you drive the virtual power amp harder. As you drive the virtual power amp harder the frequency response becomes more dynamic, just like the real amp. And, just like a real amp, there is a sweet spot where the compression, dynamic frequency response, distortion, etc. just feel "right". The particular settings for the sweet spot depend on the Input Drive, tone controls, etc. so there are no hard-and-fast rules. So, as always, use your ears. And don't be afraid to use your ears. You'll be a better player when you learn how the controls interact and how to find the sweet spot. The great players in guitar history new how to work their amps. They didn't rely on someone else to tell them where to set the knobs, they learned themselves." [http://forum.fractalaudio.com/threads/axe-fx-ii-firmware-version-12-04-public-beta.80497/page-28#post-979668]
</blockquote>

<blockquote>
"With Version 13.xx firmware the constraints on MV are lessened. Due to the improved power tube modeling you can increase the MV more without the tone getting flubby or harsh."
</blockquote>

<blockquote>
"The way I dial in the MV is to turn up the MV until the amp stops getting louder. This is the point at which the power amp is saturating heavily. Then I back it off until I get the right amount of preamp and power amp distortion. That's the sweet spot where you get the tone and the dynamics. Too little MV and it's all preamp distortion and there's not much dynamics. Too much MV and the power amp is clipping too much and it can get flubby and/or harsh. Just as with a real tube amp you have to get the power amp cooking to get the best tone and feel. Get that power amp working hard and the supply bouncing around and things get nice." [http://forum.fractalaudio.com/threads/18beta-kick-in-the-balls.96781/page-2#post-1161823]
</blockquote>

<blockquote>
(before "Cygnus" amp modeling) "The taper of the MV on the Axe-Fx does not necessarily match the taper of the actual amp. We use the same taper on every model. IIRC it is a Log10 taper. Many amps use a taper that is more abrupt than that for marketing reasons. For example, a Blues Jr has a linear taper MV. This means the amp is near full volume when the MV is at 3. This gives the impression that an amp is "loud". When the unsuspecting customer is testing the amp and it gets really loud with the MV on 2 the customer instinctively goes "wow, this amp is loud, it must be good". Anyways we use a consistent Log10A taper on every model. In general this means you need to set the MV higher than you would on the real amp. For example if the real amp has a linear taper halfway on the model would be equivalent to 1 on the amp (assuming the amp is calibrated from 0 - 10). The taper of a logarithmic pot has the nomenclature LogXA where 'A' indicates audio and X is the percentage of the element resistance from wiper to CCW terminal with the pot at 50% rotation. So a 1 Megohm Log10A pot would have 100K between the wiper and the CCW terminal when the pot is at "noon"." [http://forum.fractalaudio.com/threads/18beta-kick-in-the-balls.96781/page-3#post-1162192]
</blockquote>

<blockquote>
"All Axe-Fx models have been "modded" to include a Master Volume. Setting the MV to 10 effectively removes it from the circuit." [http://forum.fractalaudio.com/threads/non-master-volume-amps-10-vs-9.98368/#post-1180180]
</blockquote>

<blockquote>
"Those amps (JCM, SLO) are all designed to get their character from power amp distortion. If you don't push the power amp all you are hearing is the preamp which is voiced to be trebly. The power amp then compresses the highs and the sound gets fatter." [http://forum.fractalaudio.com/threads/1-biggest-user-error.103152/page-3#post-1235311]
</blockquote>

<blockquote>
"I was helping a customer out yesterday. He was complaining about lack of feel and thinness. I asked him what his Master Volume was set at. He said 1.5. I asked "why so low?". He said "because that's where I set it on the real amp". I explained that the MV on the Axe-Fx has a much gentler taper than real amp and that 1.5 on the real amp is probably around 5 or more on the Axe-Fx. So he cranked the MV up and exclaimed "wow, that's what I'm looking for!". The MV taper on the Axe-Fx is a Log15A taper. This means the output is 15% of the input when the "pot" is at noon. Most amps use a higher taper than this, say 30A or even a linear taper. This is done as a marketing ploy. The unsuspecting customer sets the MV to 2.0 and goes "wow, this amp is loud". Thing is the amp doesn't get much louder. This also makes adjustment difficult because most of your volume range is constrained to a small fraction of the dial rotation. The Axe-Fx uses a gentler taper so that you can fine-tune the MV easier. So don't be afraid to crank that MV up. When the MV is turned up the virtual power amp works harder which causes the virtual power supply to sag which adds compression which adds feel. It also thickens up the tone when you play harder because the power amp is distorting. You'll get much better results if you learn to find the sweet spot. While playing, turn up the MV until the volume stops getting louder. At this point you are driving the power amp into heavy distortion. Now back off the MV until you get the desired tone and feel. With practice you'll learn to identify how much the power amp is being pushed and where the sweet spot is." [https://forum.fractalaudio.com/threads/1-biggest-user-error.103152/]
</blockquote>

<blockquote>
"If you want the best tones out of the Axe-Fx you should stop copying photos of knob settings and learn how the knobs work. MV is one of the most important knobs as it controls how hard the virtual power amp is driven. Learning to find the sweet spot is an exercise that will pay handsome dividends. Take the JCM800 model. Set the MV very low, say 1.0. Play for a while. The sound will be harsh and scooped with a stiff feel. Turn the MV up to 5.0. Notice how there is more midrange and a softer high-end response, more compression and a better feel. Turn it up all the way and it will get fuzzy and indistinct. A real amp does the same thing. Learning to dial in the MV is among the most important abilities to harness the most from your Axe-Fx." [http://forum.fractalaudio.com/threads/setting-the-master-volume-of-the-usa-iic-deep.107231/#post-1283394]
</blockquote>

<blockquote>
"The Master Volume (MV) controls how much signal level is sent to the power amp. Many vintage amps have no MV control and the power amp runs "wide open". Modern amps often get their distortion from the preamp and the Master Volume then allows the user to control the volume of the amp. The Master Volume in the Axe-Fx II, as well as on real amps, is probably the singular most powerful control in the amp block. As the Master Volume is increased the virtual power amp begins to distort. The virtual power amp also begins to sag and all sorts of beautiful magic occurs. The tone becomes more focused, the dynamic response changes, the note attack is accentuated, etc.”
</blockquote>

<blockquote>
“MV is the one knob that everyone should master (pun not intended). It sets the amount of power amp drive which, in turn, controls how much current is drawn from the power supply which causes the supply to sag. The trick is to find the sweet spot. Too much MV and it can get too compressed. To little and the amp will be stiff and too scooped. The MV works just like a real amp's MV except it won't get deafeningly loud if you turn it way up.” [http://forum.fractalaudio.com/threads/axe-fx-ii-firmware-17-04-released.94957/page-8#post-1138962]
</blockquote>

<blockquote>
"With high-gain amps I start with the MV very low, say 2.0. Dial in the tone and gain and then bring the MV up until you hit the sweet spot. Back off the gain a bit if it's too gainy at that point.” [http://forum.fractalaudio.com/threads/axe-fx-ii-firmware-17-04-released.94957/page-8#post-1139089]
</blockquote>

<blockquote>
"One common theme with new users is the "blanket over the sound" complaint. Often this is due to excessive Master Volume values. The Master Volume behaves just like the actual amps. However, unlike an actual amp, if you put it on 5.0 it won't cause your cat to hide for several days. This can cause the user to set the value too high as the physical feedback of painfully loud sound is not present. As you turn up the Master Volume many amps get darker and the bass gets mushy. The key is to find the sweet spot. Do this exercise: Take an amp like the HBE. Set the MV to around 2.5 and turn the Level to a comfortable volume. Turn the Presence up to around 8.0. Copy the settings to "Y" by double-clicking the "Y" button. Now you have the same amp model and values in X and Y. Turn up the MV in Y to, say, 6.0 and lower the Level until the volume is the same. Go back and forth between X and Y and notice how much darker Y is. This occurs because the virtual power amp is distorting, and quite heavily. Due to the impedance curve of the virtual speaker load this causes the bass and high treble frequencies to clip but not the midrange. The result is, naturally, compressed bass and high treble which can sound muddy and indistinct. Modern MV amps are not designed to overdrive the power amp considerably. They are designed to get most of their distortion from the preamp and then adjust the MV until the power amp just starts to clip which is the "sweet spot". Some amps, like the Recto Modern, will distort the power amp at very low MV values, around 2.0. In real life these amps are painfully loud at these settings but in our virtual world we are unaware of this because the Level control allows us to adjust the volume to any arbitrary level. Some modeling products intentionally limit how hard their virtual power amps can be overdriven. Even with the MV on 10 the virtual power amp is not being overdriven that much. Of course this is unrealistic. Our modeling is accurate and with the MV on 10 you will get the same amount of power amp distortion as the real amp when set to 10. With this great power comes great responsibility and that responsibility is understanding how the control works and how to set it properly." [http://forum.fractalaudio.com/threads/setting-the-master-volume.119903]
</blockquote>

<blockquote>
"A little trick you can do to get the "bounce" of high MV without the muddy bass is to reduce the LF Res value on the Spkr tab. This will reduce the amount of bass clipping in the virtual power amp allowing you to turn the MV up. You can also reduce the HF Res to reduce the amount of treble clipping." [http://forum.fractalaudio.com/threads/setting-the-master-volume.119903/page-2#post-1427734]
</blockquote>

<blockquote>
"At low MV the source resistance into the PI is low which raises the highpass frequency due to the coupling cap and raises the lowpass frequency due to the Miller capacitance and snubber. As you increase the MV the source resistance increases which decreases both of these things. As you keep raising the MV the source resistance then starts to decrease as you get above 50% of the pot value." [http://forum.fractalaudio.com/threads/setting-the-master-volume.119903/page-2#post-1428935]
</blockquote>

<blockquote>
"The Master Volume behaves just like the actual amps. However, unlike an actual amp, if you put it on 5.0 it won't cause your cat to hide for several days. This can cause the user to set the value too high as the physical feedback of painfully loud sound is not present. As you turn up the Master Volume many amps get darker and the bass gets mushy. The key is to find the sweet spot. Do this exercise: Take an amp like the HBE. Set the MV to around 2.5 and turn the Level to a comfortable volume. Turn the Presence up to around 8.0. Copy the settings to "Y" by double-clicking the "Y" button. Now you have the same amp model and values in X and Y. Turn up the MV in Y to, say, 6.0 and lower the Level until the volume is the same. Go back and forth between X and Y and notice how much darker Y is. This occurs because the virtual power amp is distorting, and quite heavily. Due to the impedance curve of the virtual speaker load this causes the bass and high treble frequencies to clip but not the midrange. The result is, naturally, compressed bass and high treble which can sound muddy and indistinct. Modern MV amps are not designed to overdrive the power amp considerably. They are designed to get most of their distortion from the preamp and then adjust the MV until the power amp just starts to clip which is the "sweet spot". Some amps, like the Recto Modern, will distort the power amp at very low MV values, around 2.0. In real life these amps are painfully loud at these settings but in our virtual world we are unaware of this because the Level control allows us to adjust the volume to any arbitrary level. Some modeling products intentionally limit how hard their virtual power amps can be overdriven. Even with the MV on 10 the virtual power amp is not being overdriven that much. Of course this is unrealistic. Our modeling is accurate and with the MV on 10 you will get the same amount of power amp distortion as the real amp when set to 10. With this great power comes great responsibility and that responsibility is understanding how the control works and how to set it properly." [http://forum.fractalaudio.com/threads/setting-the-master-volume.119903]
</blockquote>

<blockquote>
"MV increases the power amp drive. If the power amp is distorting then the apparent volume will decrease as the MV is increased. It's impossible to predict how much the volume will decrease because it's dependent on dozens of other things like the Input Drive, BMT, pickup output, presence of Drive block, etc." [http://forum.fractalaudio.com/threads/wont-happen-independency-of-master-volume-and-level-in-the-amp-block.137392/#post-1631262]
</blockquote>

<blockquote>
(before "Cygnus" amp modeling) "The Master Volume is the only knob in the amp models that may not have the same taper as the real amp. All the models use the same taper (10A IIRC) for consistency. Many amps use a more abrupt taper for marketing reasons. A more abrupt taper gives the impression that the amp is louder." [http://forum.fractalaudio.com/threads/axe-fx-iii-vs-real-fuchs-ods.142679/#post-1689129]
</blockquote>

<blockquote>
"As you raise the MV the power tubes will saturate on the lows and highs first which causes the tone to have more midrange and vice-versa. Most of the controls in the Axe-Fx match their physical counterparts. The exceptions are Presence and Master Volume. Most amps simply have the wrong taper for their Presence controls. For example a 5150 Presence control does absolutely nothing from 0 to 7. All the action happens in the upper 1/4 of the control's range which is just dumb. The Axe-Fx uses a proper taper which gives a nice, even response over the full range of the control. Likewise the Master Volume on many amps is too abrupt. By 2-3 on the knob the power amp is saturating. Again we use a more rational taper so that you have finer control over power amp distortion. The downside of this approach is that if you put the Presence and Master Volume controls in the same position as the amp it won't sound the same. People do this then post videos and proclaim "See? Modeling isn't accurate!!! Toobz rule brah."" [https://forum.fractalaudio.com/threads/legacy-amp-models-consider-revisiting-full-honest-request-and-opinion.160349/post-1920107]
</blockquote>

Firmware Ares 13:

<blockquote>
“Added “Headroom” monitoring meter to Amp block. The most common reason for “muddy” tones with high-gain amps is incorrect setting of the Master Volume control. The Headroom meter displays the voltage at the virtual power tubes in dB. If the Master Volume is too high the meter will be near 0 dB most of the time. Note that this only applies to amps where the power amp is intended to run “clean” like the 6160, Recto, etc. Non-Master Volume amps get their distortion from the power amp distorting so this recommendation does not apply.”
</blockquote>

<blockquote>
(headroom meter) "It can't go above 0 dB. The headroom meter is how close the plate voltage is to ground. It can't ever be below ground so 0 dB is the maximum." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-19-00.180535/post-2207889]
</blockquote>

"Cygnus" amp modeling:

<blockquote>
"If an amp has an MV taper of greater than 15A the model's taper will be 15A otherwise it will match the amp. I.e., a Blues Jr. has an MV taper that is linear (which is ridiculous). The model's taper will therefore be 15A. There are a handful of exceptions, i.e. Camerons have linear taper MV and you need it with them because the signal level into the power amp is very low due to the Jose topology." [https://forum.fractalaudio.com/threads/mv-poll.170996/post-2059425]
</blockquote>

<blockquote>
"In the vast majority of models the knobs behave the same as the amp. There are a handful of models where I've taken artistic license and changed the tapers to give a more useable response. For example the Master Volume in a Blues Jr. is linear taper. This is ridiculous as it makes it very difficult to find the sweet spot. The model uses an audio taper instead which makes finding the sweet spot easier. (..) and now Cygnus firmwares have authentic behavior for most models except in a handful of cases where the manufacturer's choice of taper is dumb." [https://forum.fractalaudio.com/threads/cygnus-is-absolutely-magnificent.173225/post-2096570]
</blockquote>

<blockquote>
"You have to be very careful with the Master Volume. A Recto will start saturating the power amp in Modern mode at VERY low MV settings. Once the power amp starts clipping the tone will change. With digital products I often see people set the MV higher than they would on the real amp because there are no sonic repercussions (i.e., pissing off the wife/neighbors, knocking Grandma's urn off the mantel, etc.). If an emulation sounds darker or more midrangey than the real amp try turning down the MV. If it's a good emulation you should find a point (around 1-2) where you can hear the power amp start to saturate. Go up/down from there to get the desired power amp overdrive." [https://www.thegearpage.net/board/index.php?threads/why-are-rectifier-emulations-so-off.2341907/post-34347979]
</blockquote>

<blockquote>"Sag is also dependent on Master Volume. The higher the MV, the more sag." [https://forum.fractalaudio.com/threads/can’t-nail-the-robben-ford-sound-and-i-know-exactly-why-help.199726/#post-2488659]</blockquote>

See AxeFxTutorials' "[https://www.youtube.com/watch?v=BWQ65u39nM8 Preset Leveling: Master Volume vs Level in the Amp Block]" for more information.

'''Gain, Overdrive:'''

From the Owners Manual:

<blockquote>
“Input Drive sets the amount of preamp gain/distortion. Used in conjunction with the Master Volume, Input Drive determines whether the sound will be clean, broken up, overdriven, or fully distorted. A treble peaker circuit found on the drive or volume control on many amps is also modeled. This can be heard as the low frequencies are attenuated more than the highs when the drive is turned down (and vice versa). For amps that have no Master Volume, Input Drive functions as the amp’s volume control.”

“Amps with Overdrive will not display Input Trim (above). Adjusts overdrive. Note that Input Drive and Overdrive are applied to the appropriate points in the circuit for the amp being modeled, i.e. prior to the last triode stage or prior to the third triode.”
</blockquote>

Some models have Gain and Overdrive controls.

If the real amp has two gain controls, the one closest to the 1/4" input is modeled as Input Drive in the model. The other one is Overdrive.

<blockquote>
(Axe-Fx II) "The Amp block now differentiates amps that have both Input Drive and Overdrive controls, i.e. Mesa Mark series, Dumble, etc. When a model is selected for amps of this type, the menu shows both controls. For other types the menu shows only the Input Drive control (which was formerly called simply “Drive”). The Overdrive control defaults to noon when amps with this control are selected. As such, any presets based on these amps may need to be updated as this control was not present previously and the amount of drive may differ now. Note that these two controls are applied to the appropriate point in the circuit for the amp being modeled, i.e. for Dumble-style amps the Overdrive is prior to the last triode stage. In Mesa Mark amps the Overdrive is applied prior to the third triode."
</blockquote>

Fractal Audio explains:

<blockquote>
"Input Drive increases the gain amount as you rotate the knob clockwise. As the gain increases the tone is shifted from a treble and upper mid emphasis, which produces an up front sparkling tone, to a lower mid and bass emphasis, which produces a thick meaty tone. Overdrive increases the gain amount as you rotate the knob clockwise but with no alteration of the tonal balance. Different combinations of Input Drive and Overdrive settings will have a dramatic effect on the response of the amplifier and the personality of your instrument. It is easy to get familiar with the action of these controls and you’ll be amazed with your ability to make any guitar sound mellow, fat, soulful or aggressive." [https://forum.fractalaudio.com/threads/understanding-input-drive-and-overdrive.71449/post-875745]
</blockquote>

<blockquote>
"Input Drive is the modeled amp's gain, drive, volume, etc. control. It adjusts the attenuation at the input to the amplifier gain stages after the input buffer. On a Marshall Plexi, for example it is the "Loudness" control. On a typical Fender amp it is the "Volume" control. On many high-gain amps it is called either "Gain" or "Drive". On a real amp this is implemented using a variable resistor called a potentiometer. Many amps include a "bright cap" on the drive control which is a small value capacitor placed across the terminals of the pot that bleeds treble frequencies through as the gain is reduced. Sometimes this bright cap is switchable via a switch on the amp. Sometimes it is fixed." [https://forum.fractalaudio.com/threads/understanding-all-the-different-gain-controls.95018/post-1138073]
</blockquote>

<blockquote>
"In a typical amp Input Drive is called various names (Drive, Volume, Gain, etc). It is the knob closest to the input jack. In many cases this potentiometer has a bright cap on it so the frequency response will be dependent on the knob position. In some amps there is also a second drive control. This is your Overdrive knob. It does not have a bright cap so it only affects the gain." [http://forum.fractalaudio.com/threads/new-10-10-firmware-thoughts.71497/page-3#post-877347]
</blockquote>

<blockquote>
"Sometimes they're labeled Gain, sometimes Drive, sometimes Volume. On an Soldano X88 they're labeled "Preamp"." [http://forum.fractalaudio.com/threads/authentic-amp-controls-amazing.148305/page-2#post-1754976]
</blockquote>

<blockquote>
"Some amps possess an attenuation control between the later gain stages. Examples of the are the Mesa/Boogie Mark series, Dumble ODS and others. This control allows the user to vary the gain staging. The Input Drive can be turned up and the Overdrive turned down so that the earlier stages distort more and the later stages distort less and vice-versa." [https://forum.fractalaudio.com/threads/understanding-all-the-different-gain-controls.95018/post-1138073]
</blockquote>

The range of the Gain taper in the amp modeler is 0-10. Volume controls on Fender amps go from 1 to 10, or 11 or 12. [[Amp_block#Authentic_or_idealized_controls| Go here]] for the translation of the real controls to the model.

You can attach a Scene Controller to Gain, and then use scenes to vary the amount of amp gain. Or use an internal or external controller instead. Note that with some amps models this bumps CPU usage.

Fractal Audio explains:

<blockquote>
"Depending upon the amp model it can take a lot of CPU to calculate the Input Drive network. Some amps have simple networks that are rapidly solved. Others, like the Hook Lead and Rhythm models have complex networks that require more math. If you attach a modifier to the Input Drive it is constantly recalculating the network which increases CPU usage."
</blockquote>

<blockquote>
"Some amps have complicated input drive circuitry that requires a lot of calculations. Adjusting the Input Drive control can result in crackling as the time required to recalculate the network is long. Don't attach a controller to the Input Drive on these amps." [https://forum.fractalaudio.com/threads/not-a-bug-possible-bug-in-carol-ann-od-2.153162/post-1821948]
</blockquote>

<blockquote>
"Takes a lot of math to calculate the Drive. Not a bug." [http://forum.fractalaudio.com/threads/not-a-bug-error-sound-with-solo100-rhy-if-it´s-drive-is-controlled-with-scene-controllers.132355/#post-1566823]
</blockquote>

About jumpered channels:

<blockquote>
"Even a small bit of capacitance difference at the inputs of these amps makes a difference. Our models assume a fairly short jumper cable (3-4 inches). In my tests just increasing the length of the jumper cable to 1 ft. changed the frequency response significantly. So if your Y-cable is more than a few inches long it will change things." [https://forum.fractalaudio.com/threads/plexi-input-modeling-question.188339/post-2336388]
</blockquote>

==OVERDRIVE VOLUME==

Added in firmware 21 for the Axe-Fx III. Release notes:

<blockquote>"Added “Overdrive Volume” parameter to Dumble-type amp models (ODS-100, Two Stone, etc.). This is sometimes labeled “Ratio” or “Lead Master”. As the Master Volume on these amps often has a bright capacitor the Overdrive Volume control allows setting the Master Volume higher to counteract the bright cap and then lowering the power amp drive with the Volume."</blockquote>

Fractal Audio:

<blockquote>"Most, if not all, Dumble-style amps have a Ratio/Volume/Lead Master/etc. control so this makes the models complete in that regard. My Fuchs ODS 50 does NOT have a bright cap on the MV but it has an "Output" control for the overdrive channel that is in series with MV." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-00-public-beta-2-beta-2.187991/post-2331157]</blockquote>

==BASS + MID + TREBLE==

From the Owners Manual:

<blockquote>
“While other modelers use simple filters to approximate amp tone controls, our products recreate the exact frequency and phase response characteristics of a classic passive tonestack. In most cases, knob positions can even be matched to settings on the original amps. (Though recognize that many types of amps were built inconsistently with different types of potentiometers from one run to another.)
</blockquote>

Many models provide tone controls NOT offered on the original amp. For example, many amps have no Mid control. To faithfully simulate such amps, set controls they are missing to “noon” (or “0” if you are using the “ACTIVE” Tonestack Type). Of course, you may still adjust these “bonus” controls to achieve innovative tones.” </blockquote>

The exact frequency and phase response characteristics of the tone stacks on the original amps are modeled.

If the real amp doesn't have one or more of these controls, like a Mid knob, leave it at the default (Mid: noon).

See [[Amp_block#Authentic or idealized models| Authentic or Idealized models]] for more information about these controls.

Fractal Audio Explains:

<blockquote>
"Setting bass and treble to zero on a passive tone stack tells you nothing about the response of the midrange control. On a Fender setting bass and treble to zero turns the midrange into a volume control. On a Marshall it turns it into some weird highshelf/lowpass thingy. A passive tonestack is a very different animal than active tone controls with well-behaved frequencies. Download and play with Duncan's TSC to see the effects." [https://www.thegearpage.net/board/index.php?threads/ir-properties.2047238/page-43#post-28717398]
</blockquote>

==HIGH TREBLE==

This parameter is named HIGH TREBLE in firmware Ares and later.

This was previously called the "Bright" knob.

From the Owners Manual:

<blockquote>
“Think of this as an extra tone control, useful to add “zing” or tame harsh highs.”
</blockquote>

It's a shelving filter between the preamp and power amp and can be used to darken or brighten the output of the preamp. It replicates the “Presence” control in the Mesa Triaxis preamp when set to negative values (the Presence control in the Triaxis is a high frequency cut shelving filter).

Do not confuse this with the [[#BRIGHT|Bright]] switch (see above).

Fractal Audio Explains:

<blockquote>
"The Bright Knob is an active fourth tone control at high frequencies. Think of it as "High Treble". You can use it to add a little zing to a preset or remove harsh high frequencies. You can also use it to simulate the behavior of the Presence control on a Triaxis (which is really just a high cut). Turn it down to simulate "Presence" settings less than 10." [http://forum.fractalaudio.com/threads/always-look-on-the-bright-side-of-life.110008/#post-1317029]
</blockquote>

==PRESENCE + HIGH CUT==

From the Owners Manual:

<blockquote>
“Boosts (or cuts) the upper frequencies from the virtual power amp by varying the negative feedback frequency response. Increased presence can help a sound cut through. Note that settings for Presence don’t necessarily correspond to knob positions on the amp being modeled."
</blockquote>

Presence is a high-frequency tone control for the power amp section. It boosts (or cuts) the upper frequencies from the virtual power amp by varying the negative feedback frequency response.

Amps with no negative feedback circuits in their design cannot utilize a realistic presence control. Therefore, if Negative Feedback is set (manually or automatically) to “0”, Presence won't do anything anymore (in "Cygnus" amp modeling firmware).

If Power Amp Modeling is turned off, Presence is disabled (Quantum 9.03 and later). Before Quantum 9.03, Presence turned into a shelving filter when power amp modeling was disabled.

The range (min/max) of the Presence knob in the model is the same as the range of the real Presence knob on the modeled amp.

In some USA amps (Mesa Boogie), the Presence knob can be engaged to enable the "Presence Shift" function. And in the USA Pre model, there are separate Presence controls for the preamp and the power amp.

Cygnus amp modeling: the Presence control in the Amp block now behaves like the actual amp rather than an idealized version. The Presence Frequency parameter is now a frequency multiplier rather than an absolute frequency as the frequency of the presence circuit depends on the Presence control position. The Presence Frequency parameter works by scaling the value of the virtual presence circuit’s capacitor value. Setting the Pres/Depth Type parameter to Active or Active Pres will override the authentic modeling and implement an ideal presence circuit with fixed center frequency.

Presence control is set to a default value when an amp model is selected. This is done because many amps, i.e. Double Verb, Deluxe Verb, et. al., have no presence control and the value should be set to zero for best accuracy. On the other hand some amps, i.e. Jr. Blues, 65 Bassman, et. al, have fixed presence networks. The Presence control will default to the appropriate value for these amps. For amps that do have a presence control, the Presence parameter will default to a value that is deemed typical for the model.

Fractal Audio Explains:

<blockquote>
"The Axe-Fx II presence operates just like a real amp and modifies the virtual power amp feedback. This actually does create a sort of "magic" since it changes the shape of the distortion vs. frequency. That's the advantage to the nonlinear feedback network that the Axe-Fx uses. Negative feedback makes the distortion transfer function "harder". The presence control reduces negative feedback at high frequencies. This increases the treble but also softens the transfer function so you get more highs but the softer distortion reduces the amount of harsh overtones." [http://forum.fractalaudio.com/threads/slo-100-models-on-axefx-and-amplitube.85267/#post-1033870]
</blockquote>

<blockquote>
"The effect of Presence and Depth is consistent with the behavior of the real amp and depends on the amount of negative feedback. As you decrease negative feedback the presence and depth controls have less effect (as in a real amp). Also, as you increase Master Volume the presence and depth may appear to be less effective (key word is "appear") as the power amp distorts more and this masks the effect of the controls." [http://forum.fractalaudio.com/threads/may-be-stupid-questions-on-fw15.87420/#post-1058088]
</blockquote>

<blockquote>
"A tube amp's presence control is basically a type of treble control. It affects a higher range of frequencies and operates on a different principle but the net effect is an increase in high frequencies. There is also a slight increase in distortion in the higher frequencies since the power amp becomes less linear for those frequencies".
</blockquote>

<blockquote>
"HiCut is dependent upon Damping, just like a real amp. Hi Cut is modeling the Miller capacitance at the input to the Phase Inverter. The more negative feedback, the less the Miller capacitance." [http://forum.fractalaudio.com/threads/adv-hi-cut.47260/#post-615856]
</blockquote>

<blockquote>
(before Cygnus amp modeling) "Presence and Depth controls may not match the taper of the actual amp. On most amps the Presence control does nothing until you turn it almost all the way up. This seems a bit silly so we make the Presence behave more logically. Same goes for the Depth control." [http://forum.fractalaudio.com/threads/new-18-00-public-beta.96570/page-7#post-1158815]
</blockquote>

<blockquote>
(before Cygnus amp modeling) [http://www.fractalaudio.com/downloads/manuals/axe-fx-2/Fractal-Audio-Systems-MIMIC-(tm)-Technology.pdf MIMIC whitepaper]: "Note however that the taper of the presence (and depth) control can deviate from the actual amp. In our tests we found that the presence control on many amps did nothing for the first 80% of its rotation and all the action occurred in the last 20%. We feel that this design anomaly is undesirable and therefore did not model that aspect."
</blockquote>

<blockquote>
(Axe-Fx II) "Improved Amp block feedback network accuracy especially for those amps that have depth networks. This causes the Presence and Depth controls to interact (as they would on a real amp) but yields greater realism."
</blockquote>

<blockquote>
(before Cygnus amp modeling) "The Presence control on the Axe-Fx is more linear. The Presence control on most amps does nothing for the first half of its rotation or more. I made it so the Presence control actually does something when you turn it. Therefore you typically need to set the Presence control lower than you would on the amp."
</blockquote>

<blockquote>
(before Cygnus amp modeling) "Most of the controls in the Axe-Fx match their physical counterparts. The exceptions are Presence and Master Volume. Most amps simply have the wrong taper for their Presence controls. For example a 5150 Presence control does absolutely nothing from 0 to 7. All the action happens in the upper 1/4 of the control's range which is just dumb. The Axe-Fx uses a proper taper which gives a nice, even response over the full range of the control. Likewise the Master Volume on many amps is too abrupt. By 2-3 on the knob the power amp is saturating. Again we use a more rational taper so that you have finer control over power amp distortion. The downside of this approach is that if you put the Presence and Master Volume controls in the same position as the amp it won't sound the same. People do this then post videos and proclaim "See? Modeling isn't accurate!!! Toobz rule brah."" [https://forum.fractalaudio.com/threads/legacy-amp-models-consider-revisiting-full-honest-request-and-opinion.160349/post-1920107]
</blockquote>

<blockquote>
"A 5150's presence control has almost no effect from 0 to 7. After 7 the treble increases rapidly. The taper of the presence control in a 5150 is a log30 IIRC (maybe log10, I'd have to check my notes). If anything it should be linear. Ideally it should be reverse log. Our model uses a reverse log taper which gives a nice, smooth response over the full range. In most cases a reverse log taper would be the ideal taper. However reverse log taper pots are uncommon, difficult to source and cost more. Why they chose a log taper in the 5150 is a mystery. Since the power amp has similarities to a Marshall perhaps Eddie wanted the presence control to behave like his old Marshalls. Another possibility is the designer felt the amp was too bright with all knobs at noon (and a linear taper presence pot) and changed the taper to reduce the brightness." [https://www.thegearpage.net/board/index.php?threads/blind-test-mesa-dual-rectifier-vs-mystery-modeler-update-results-revealed.2208367/post-31639265]
</blockquote>

==DEPTH==

From the Owners Manual:

<blockquote>
“Boosts low frequencies from the virtual power amp by varying the negative feedback frequency response. It is set by default to an appropriate value when the amp type is selected, but this setting may be overridden.”
</blockquote>

Operates the same as Presence (see above) but it handles the low frequencies.

Like Presence, Depth is disabled if Power Amp modeling is disabled.

Fractal Audio explains:

<blockquote>
"Excursion = Depth. Manufacturers like to give this control fancy names (Excursion, Whomp, Resonance, etc., etc.) but it's just a Depth control." [https://forum.fractalaudio.com/threads/who-sold-a-bogner-ecstasy-amp-for-axe-fx-ii.101766/#post-1220413]
</blockquote>

<blockquote>
"Depth = Resonance = "Whomp" = whatever colloquialism the manufacturer can think of. Depth differs from Bass in that it is applied in the power amp as opposed to the preamp. It is done by modifying the feedback network. Less lows are fed back thereby increasing bass response in the power amp. It is analogous to Presence except it affect bass instead of treble. If you look at the Axe-Fx II's menu you'll see the tab says "PWR AMP" thereby indicating it is a power amp control." [http://forum.fractalaudio.com/threads/amp-5150-depth-control-what-is-it.79186/#post-963090]
</blockquote>

<blockquote>
"Many amps have no depth circuit, e.g. Fenders, most Marshalls, and generally most older designs. In these cases the Depth knob will default to zero indicating the amp has no depth circuit. Some amps have a fixed depth circuit, e.g. 5153, Freidman BE/HBE, Dirty Shirley, TripTik, Tucana, et. al. In these cases the Depth knob will default to a value that corresponds to the fixed circuit. Finally some amps have a variable depth circuit, e.g. 5150, Diezel, et. al. In these cases the Depth knob defaults to a non-zero value that I think sounds good but that's just my taste. The choice of IR and the monitoring system can greatly influence the amount of perceived bass. The desired amount of bass is a preference. If you are into "classic" tones then a Depth of zero would be a logical choice." [http://forum.fractalaudio.com/threads/lets-talk-about-the-depth-control.88747/#post-1071598]
</blockquote>

<blockquote>
"Depth does not work at a Damping of 0 since Depth modifies the feedback and there is no feedback." [http://forum.fractalaudio.com/threads/damping.59333/#post-740665]
</blockquote>

<blockquote>
"The effect of the Presence and Depth is consistent with the behavior of the real amp and depends on the amount of negative feedback. As you decrease negative feedback the presence and depth controls have less effect (as in a real amp). Also, as you increase Master Volume the presence and depth may appear to be less effective (key word is "appear") as the power amp distorts more and this masks the effect of the controls." [http://forum.fractalaudio.com/threads/may-be-stupid-questions-on-fw15.87420/#post-1058088]
</blockquote>

<blockquote>
"I look at the Depth knob as a starting point. Just because the 5153 has a fixed depth circuit doesn't mean you can't adjust the knob. The only reason that it is fixed on that amp is there wasn't enough room to put in separate knobs for each channel. The 50W version has an adjustable Depth (it's called resonance and the knob is on the back). The original 5150 had adjustable Depth. The designers choice isn't necessarily best. It depends on the cabinet (or IR) and your personal preferences. Short answer: use your ears. I think too many people are scared to use their ears. But if you constantly rely on the ears of others you'll never learn how to create your own signature sound." [http://forum.fractalaudio.com/threads/lets-talk-about-the-depth-control.88747/#post-1071786]
</blockquote>

<blockquote>
(before Cygnus amp modeling) "Presence and Depth controls may not match the taper of the actual amp. On most amps the Presence control does nothing until you turn it almost all the way up. This seems a bit silly so we make the Presence behave more logically. Same goes for the Depth control." [http://forum.fractalaudio.com/threads/new-18-00-public-beta.96570/page-7#post-1158815]
</blockquote>

<blockquote>
(before Cygnus amp modeling) [http://www.fractalaudio.com/downloads/manuals/axe-fx-2/Fractal-Audio-Systems-MIMIC-(tm)-Technology.pdf MIMIC whitepaper]: "Note however that the taper of the presence (and depth) control can deviate from the actual amp. In our tests we found that the presence control on many amps did nothing for the first 80% of its rotation and all the action occurred in the last 20%. We feel that this design anomaly is undesirable and therefore did not model that aspect."
</blockquote>

<blockquote>
(Axe-Fx II) "Improved Amp block feedback network accuracy especially for those amps that have depth networks. This causes the Presence and Depth controls to interact (as they would on a real amp) but yields greater realism."
</blockquote>

<blockquote>
"Depth is dependent upon the speaker load. If your load doesn't match the internal speaker impedance curve exactly the response will be different. When I'm testing amps I have a special speaker impedance curve I use that is derived from the particular LB-2 that I use. The curve included in the firmware is a typical LB-2 response. Due to component tolerances the resonant frequency and magnitude can vary as much as 20%. Furthermore with the depth all the way up it is easy to start overdriving the power amp in the bass range. Again, due to pot tolerances the amp may be overdriving more or less than the model for a given MV setting. I should add that Depth is also dependent upon the open-loop gain of the power amp which, in turn, is dependent upon the transconductance and bias point of the power tubes. Therefore different power tubes and bias point will also affect the amount of low-frequency boost." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-00-release-candidate-2-beta-8.188778/post-2342487]
</blockquote>

==CUT==

From the Owners Manual:

<blockquote>
“Reduces the amount of low frequencies coming into the amp simulation. This can be used to achieve a “tighter” tone or to reduce low-end “flub”.”
</blockquote>

It is a first-order shelving filter (high-pass) at the input of the Amp block. This can be used to achieve a “tighter” tone and to reduce low-end “flub”. It defaults to 120 Hz. The frequency can be adjusted through the Low Cut Frequency parameter.

Note: Cut is the same as increasing Low Cut on the Input EQ page (see below).

Fractal Audio explains:
<blockquote>
"You can use a Filter block before the Amp set to Shelving if you want to add more flexibility to what the Cut switch is doing in the Amp block." [http://forum.fractalaudio.com/threads/new-cut-parameter.72470/#post-887770]
</blockquote>

<blockquote>
"120 Hz is where most amp designers put it. A typical cathode bypass has the pole at approx. 85 Hz. Assuming 6 dB gain reduction that puts the center frequency at 120 Hz." [http://forum.fractalaudio.com/threads/new-cut-parameter.72470/#post-887765]
</blockquote>

<blockquote>
"The bass cut switch is before the distortion so it will change the feel and breakup characteristics. The bass cut is basically intended to give you that Tube Screamer with Drive on 0 sound without having to use a dedicated Drive block." [http://forum.fractalaudio.com/threads/hi-cut-cab-bass-cut-amp-overkill.74445/#post-910785]
</blockquote>

<blockquote>
"Cut engages a lowshelf filter at the input. This would be analogous to partially bypassing the input buffer cathode on a tube amp." [http://forum.fractalaudio.com/threads/controlling-the-lows.96327/#post-1154831]
</blockquote>

==FAT==
From the Owners Manual:

<blockquote>
“Emphasizes midrange and adds “body” by shifting the tonestack center frequency.”
</blockquote>

This is similar to the FAT switch on a Mesa Boogie, which is a popular control for lead tones because it adds body to the tone.

Fractal Audio explains:
<blockquote>
"The Fat switch simply alters the tone stack treble capacitor. So the effect depends on the location of the tone stack." [http://forum.fractalaudio.com/threads/national-enquirer-fractal-fatswitch-fiasco.51361/#post-660652]
</blockquote>

<blockquote>
"The Fat Switch multiplies the tone stack treble cap by four. Depending upon the type of tone stack, tone control settings, position, etc., etc. the effect can be more or less noticeable." [http://forum.fractalaudio.com/threads/fat-switch.76310/#post-932073]
</blockquote>

<blockquote>
"The Fat switch changes a value in the tone stack which changes the response of the stack, shifting the mid dip down and making it less pronounced. The Tonestack Freq. parameter frequency scales all the reactive components in the tone stack which is something quite different." [http://forum.fractalaudio.com/threads/fat-switch-is-totally-different-than-axe-fx-ll.145247/page-2#post-1718101]
</blockquote>

==BRIGHT==
From the Owners Manual:

<blockquote>
“Many amplifiers contain a “treble peaker,” included as a pull or toggle switch, or even hard- wired. Each amp type includes this control (even if the original mode does not). The effect may be subtle or quite pronounced depending on the amp type. This is also affected by the Bright Cap setting. If the original amp had no bright circuit, Bright is OFF by default but can still be turned on to apply circuit values suited to an amp of that general type. If the amp has a hard-wired treble peaker, the default state is ON.”
</blockquote>

The Bright ''switch'' is not to be confused with the BRIGHT ''knob'' (Axe-Fx III, FM9 and FM3: High Treble) which is a shelving filter between the preamp and power amp (see below).

The Bright switch is either:
* the virtual equivalent of a bright switch (pull or toggle) on the real amp.
* the virtual equivalent of a bright cap on the volume or gain control of a real amp.
* the virtual equivalent of a hard-wired bright switch inside the amp.
* a method to change to the Bright channel of the original amp (if the original amp has a Normal and a Bright channel/input, and only the Normal channel/input has been modeled).

Bright caps are used to compensate for guitars with weak pickup loads, increasing treble as gain is decreased. It also changes the mids, which affects gain too.

If the modeled amp has a hard-wired treble peaker, the default state of the virtual Bright switch is ON.

Turning up the amp's Drive or Master may decrease the impact of the Bright switch, depending on the amp type.

The effect of the Bright switch on the tone can be controlled through the Bright Cap value parameter.

Some amp types, such as a Plexi, have a very high Bright Cap value, which has a large impact on the amount of gain.

Fractal Audio explains:
<blockquote>
"If an amp doesn't have a bright switch, the operation of of the models' bright switch is undefined. I chose what I considered a reasonable value for the bright cap but if that doesn't satisfy the user then they are free to change it to a different value." [http://forum.fractalaudio.com/threads/vh4-amps-bright-switch.70382/page-2#post-865222]
</blockquote>

<blockquote>
"The Bright switch always controls the bright cap on the input volume." [http://forum.fractalaudio.com/threads/any-way-to-disable-bright-cap-on-dumble.74295/#post-909499]
</blockquote>

<blockquote>
"The Bright switch switches in/out one or more capacitors on the Input Drive network." [http://forum.fractalaudio.com/threads/always-look-on-the-bright-side-of-life.110008/#post-1317029]
</blockquote>

<blockquote>
"The Bright Switch models the "bright cap" across the drive/gain/volume/comodjulator pot. Some amps have no bright cap, some amps have a hardwired bright cap and some amps give you a switch to turn it on/off. A bright cap increases treble as the pot is turned down. The original impetus for this was that guitars with weak pickups tend to be brighter and guitars with hot pickups tend to be darker. So you're likely to turn the gain up for the guitar with weak pickups which reduces treble response. On the guitar with hot pickups you're likely to turn the gain down which increases treble response to counteract the darker tone. If the amp has no bright cap the Bright Switch defaults to off. If the amp has a hardwired cap the switch defaults to on. If the amp has a switch it defaults to whatever we felt sounds the best. Our particular JCM800 reference amp has no bright cap because someone removed it. However the model has the switch on because that's the way the amp would've come from the factory. There are actually 11 different (IIRC) bright cap models in the Axe-Fx/AX-8. The earliest bright cap circuits were just a cap from the input terminal to the wiper. Over time designers have developed more complex circuits with resistors in series with the cap, another cap from the wiper to ground, treble peakers before/after the pot, etc. The user doesn't have the ability to select the model though, it is hard-coded into each model." [http://forum.fractalaudio.com/threads/fractal-vs-helix-let-the-comparisons-begin-video-series.119390/page-2#post-1423491]
</blockquote>

<blockquote>
"Those amps have a "bright switch" that is permanently on but there is no physical switch on the actual amp. The capacitor is hard-wired." [http://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-4-00-beta.148349/page-15#post-1756141]
</blockquote>

==BRIGHT CAP==

From the Owners Manual:
<blockquote>
“Sets the value of a virtual capacitor to determine the sonic effect of the Bright switch. Increasing this will make the preamp brighter and vice versa.“
</blockquote>

Fractal Audio explains:
<blockquote>
"That's one of my go-to tweaks. The amount of treble peaking needed for an amp at a given drive is highly dependent on the guitar. For example my guess is that the AFD100 was designed around a Les Paul. With my Suhr it's much too bright because that's a very bright guitar. So one of the first things I do with the AFS100 model is turn down the bright cap a bit." [http://forum.fractalaudio.com/threads/firmware-1-11.140004/page-2#post-1660177]
</blockquote>

<blockquote>
"Input Trim at 0.5 is equivalent to using the Low input jack on amps. If you are using high-output pickups it's often better to use the Low input to get into the sweet spot of the bright cap." [https://forum.fractalaudio.com/threads/the-modeler-equivalent-to-alternate-guitar-tunings.155649/post-1853194]
</blockquote>

==MASTER VOLUME TRIM==
From the Owners Manual:

<blockquote>
"Allows you to adjust the range of Master Volume. Increasing the value above 1.0 will cause more gain in the virtual power amp and vice versa."
</blockquote>

=Preamp=

==INPUT BOOST + TYPE + LEVEL==

From the Owners Manual:
<blockquote>"Acts as a “clean boost,” replicating the common technique of driving an amp harder by using a drive pedal with the “Drive” knob at 0 and the “Level” turned up. To use the boost, turn the switch on, choose the boost type (types are based on real pedals, each with its own EQ/color) and set the Boost Level as desired.

The Boost switch can be operated with a Modifier. These controls provide a way to give an amp model more gain without the CPU overhead of adding a drive block."</blockquote>

Increases the signal level at the input section of the Amp block.

'''AX8''' and '''Axe-Fx II''' — Boost is fixed at 12 dB.

'''Axe-Fx III''' and '''FM3''' and '''FM9''' — You can choose between many different [[#Input boost types|input boost types]]. These all act as clean boosts, replicating the oft-used “Drive on 0, adjust Level as desired” boost technique. This allows boosting the Amp block without requiring a separate Drive block. The difference between the various types is the EQ (frequency response) of each model. The Boost Level parameter sets the amount of boost. Using an input boost instead of a separate Drive bock saves CPU.

The gain range of the Input Boost has been increased in firmware Cygnus 16 and later.

Input 1 Gain (global parameter on the Axe-Fx III and FM9) and Input Trim in the Amp block have a similar function.

The Input Boost types are:

* '''AC Boost'''
* '''CC Boost''': "CC boost is based on ... nothing. I took a PEQ one day and was using at a boost. At one point I got something that sounded really good to me so I made it into a boost." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-6-04.152296/post-1812168]
* '''FAS Boost'''
* '''Full OD'''
* '''Grinder''': based on Fortin's Grind pedal. It incorporates Fortin's favorite 6IRTH and 6RIND settings. This type is not available as a type in the Drive block.
* '''JP IIC+ Shred''': replicates the “Shred” switch on the Mesa/Boogie JP2C.
* '''Mid Boost'''
* '''Neutral''': This is the default boost type. (Same as AX8 and Axe-Fx II).
* '''RCB Boost'''
* '''Shimmer'''
* '''Shred Boost''': A clean boost on the input similar to a Tube Screamer but without the treble roll-off (copied from the USA JP IIC+ Shred models).
* '''Super OD'''
* '''T808'''
* '''T808 Mod'''
* '''Treble Booster'''

See [[Drive block]] for more information about these types.

Fractal Audio explains:

<blockquote>
"The changes to the modeling of drives in firmware Ares 3.02 and later do not apply to these input boost types." [http://forum.fractalaudio.com/threads/faith-restored-in-my-axe.147281/page-3#post-1741111]
</blockquote>

<blockquote>
"The amp boosts are just the frequency shaping part of the drive. The clipping stuff is removed. It's analogous to turning the Drive knob all the way down and using the pedal as a clean boost." [http://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-3-02-public-beta.147926/page-11#post-1751115]
</blockquote>

==SATURATION + SATURATION DRIVE==

From the Owner's Manual:
<blockquote>“This engages a popular mod between the preamp and the tonestack for a thicker, more aggressive distortion character. “IDEAL” gives you the hotter output you wish a real amp had with saturation engaged.” “Saturation Drive controls the amount of saturation (see above). The default value differs for each mode.”</blockquote>

This is the virtual equivalent of Jose Arredondo’s famous Marshall amplifier modifications.

Enabling it decreases power amp smoothing, resulting in meaner distortion. This switch is enabled at default in certain models. Also try it with amp types such as JCM800, Friedman and Mesa Mark. With amp models that have no preamp gain, such as Plexis, saturation has no effect.

There are two types: AUTH and IDEAL. IDEAL pushes the virtual power amp harder which changes the tone.

<blockquote>(Axe-Fx II) "Amp block Sat Switch now has three settings: Off, On (Auth) and On (Ideal). On (Auth) replicates authentic saturation circuit behavior and will lower the volume out of the virtual preamp. On (Ideal) replicates the idealized behavior present in Version 14.xx and earlier firmware."</blockquote>

Fractal Audio explains:

<blockquote>"It switches in a zener diode clipping stage right before the tone stack. This is the so-called Jose Arrendondo Mod." [http://forum.fractalaudio.com/threads/axe-fx-ii-technical-questions-thread.35997/page-38#post-494304]</blockquote>

<blockquote>"The Sat (saturation) circuit is located between the preamp and power amp. If the model doesn't have much preamp gain, e.g. 59 Bassguy, then the sat switch will have little effect. A real amp would exhibit the same behavior. Amps like this get all their distortion from the power amp." [http://forum.fractalaudio.com/threads/may-be-stupid-questions-on-fw15.87420/#post-1058088]</blockquote>

<blockquote>"Sat switch works on all amps. However if an amp is getting its distortion from the power amp, i.e. Plexis, etc., then the affect may not be noticeable since the power amp distortion will mask any distortion occurring prior. Sat switches are typically employed on amps with master volumes for just this reason." [http://forum.fractalaudio.com/threads/saturation-switch-does-nothing-on-authentic-for-most-amps-not-g3-yet-maybe.104357/#post-1248576]</blockquote>

<blockquote>"It always works. If you turn down the MV its affects may be more noticeable. Be aware that a Plexi has low preamp gain and you may need to set Sat Drive quite high to get any saturation. The classic "Arredondo mod" involves adding a "saturation circuit" and a master volume as the sat circuit's affects are masked if the power amp is heavily distorted." [http://forum.fractalaudio.com/threads/saturation-switch-does-nothing-on-authentic-for-most-amps-not-g3-yet-maybe.104357/#post-1248582]</blockquote>

<blockquote>"The sat switch is located at the output of the preamp. If the distortion is coming from the power amp, i.e. a Plexi, then the effect is not very audible in Authentic mode (just as it would in a real amp)." [http://forum.fractalaudio.com/threads/0-3-sat-switch-on-has-no-audible-effect.132963/#post-1574314] </blockquote>

<blockquote>"The ideal setting will push the power amp harder which WILL change the tone." [https://forum.fractalaudio.com/threads/saturation-switch-changes-tone.161328/post-1931505]</blockquote>

==PREAMP TUBE TYPE==

From the Owner's Manual:

<Blockquote>
"Changes the characteristics of the virtual preamp tubes, based on real world examples."
</blockquote>

<blockquote>
"New RTS triode models. There are three new triode models based on our new algorithms: 12AX7A (default), ECC83 and 7025. The previous models are still available and may be selected with the Pre Tube Type parameter."
</blockquote>

<blockquote>
"Further improvement of preamp tube models based on measurements. The existing theoretical models, i.e. “Modern”, “Vintage”, etc., have been removed. There are now six extremely accurate preamp tube types: 12AX7A, ECC83, 7025, 12AX7B, ECC803 and EF86. Note that the EF86 type has been normalized to have roughly the same gain as the triode types."
</blockquote>

<blockquote>
"Updated all models to use an appropriate Preamp Tube Type when selected. I.e. British models will now use the ECC83 when selected."
</blockquote>

From the Axe-Fx II manual:

<blockquote>
"“Modern” (default) selects a triode characteristic representative of modern production tubes. “Vintage” selects a characteristic typical of tubes produced in the 50’s and 60’s. “Long Plate” replicates the softer saturation characteristic of so-called “Long Plate” triodes."
</blockquote>

<blockquote>
"There are now only two Preamp Tube Type options in the Amp block: Short Plate and Long Plate. The Vintage type has been removed. Short Plate is similar to the previous Modern model but has the improved saturation characteristics that were developed for the Long Plate model."
</blockquote>

<blockquote>
"There are now four Preamp Tube Types:
* Short Plate: an accurate model of a modern “short plate” production 12AX7.
* Long Plate: an accurate model of a classic “long plate” 12AX7.
* Modern: An idealized 12AX7 model. This is the same model from version 18.04 firmware. This model is useful for high gain tones that can benefit from the increased clarity and string separation.
* Vintage: Another idealized 12AX7 model also from version 18.04 firmware. Has a softer breakup than the Modern model. Useful for “vintage” tones where more base nonlinearity is present."
</blockquote>

<blockquote>
"The preamp modeling in 6.00 is the same as 5.xx except the parameters for the default tube type (12AX7A SYL) are different. The Sylvania 12AX7A is more nonlinear than other 12AX7As which results in more dynamics but will also result in more "background" distortion because the waveform is being distorted even when it isn't being clipped. The JJ version is more linear which will result in a tighter tone and less background distortion but less dynamics. For 6.01 I've also added back the old 12AX7B type which is the most linear of the types and clips hard. People who play with lots of gain tend to like this as it results in tighter tone and more aggressive harmonic content. There are two primary parameters associated with our preamp tube models. "Preamp Hardness" determines how abrupt the tube clips when it enters the saturation region. There is another parameter that determines how nonlinear the tube is between cutoff and saturation. This is currently not exposed to the user but I've been contemplating adding it. I've also changed the default type for British amps to the ECC83 model as these amps typically were equipped with ECC83s (duh). The ECC83 was the European equivalent of the 12AX7A and tended to be a bit more linear and clip a little harder." [http://forum.fractalaudio.com/threads/anyone-not-a-fan-of-quantum-6.121353/page-3#post-1446007]
</blockquote>

Fractal Audio explains:
<blockquote>
"The primary controls to adjust the saturation behavior are Preamp Tube Type, Preamp Hardness and Preamp Bias." [http://forum.fractalaudio.com/threads/suggestions-on-what-youve-done-to-enjoy-18-03.97925/page-9#post-1178319]
</blockquote>

<blockquote>
"The parameters for the 12AX7 were extracted from an RCA 12AX7A. The ECC83 was a Mullard." [http://forum.fractalaudio.com/threads/if-12ax7-and-ecc83-are-the-same.110515/#post-1323322]
</blockquote>

<blockquote>
"The 7025 was a Sylvania." [http://forum.fractalaudio.com/threads/if-12ax7-and-ecc83-are-the-same.110515/#post-1323463]
</blockquote>

<blockquote>
"People claim that preamp tubes sound different. They have no sound. They might have different characteristics though which cause the CIRCUIT to sound different. They might have more or less gain, or more or less capacitance, etc. It's such a crap-shoot though. Switching around tubes until you believe it sounds better. I prefer a more scientific approach. What are you trying to achieve? Okay, then lets reduce this coupling capacitor a bit." [https://forum.fractalaudio.com/threads/why-power-tubes-sound-different.79962/page-2#post-972959]
</blockquote>

==LOW CUT FREQUENCY==

This parameter sets the frequency of the [[#CUT|Cut]] switch (see above).

==HIGH CUT FREQUENCY==
From the Owners Manual:
<blockquote>
"This filters the highs at the very end of the preamp simulation. Experiment with this to fine-tune your tone. For example, some of the higher gain amp types are characterized by fairly heavy filtering after the preamp stage. Increase for a brighter tone or decrease for a darker tone."
</blockquote>

High Cut Frequency adjusts the cutoff frequency of a low-pass filter. This filter is placed between the virtual preamp and power amp, so it has a more dramatic effect than an EQ that might be placed before preamp distortion. It will cut off all frequencies above the specified value. It ranges from 2000-40000Hz.

This parameter is different from High Cut on the Input EQ page.

Fractal Audio explains:
<blockquote>(Quantum 3.00) "It's probably inaudible but there were a few amp models where the matching was indicating a loss of high-frequency response. This was traced to the high-cut filter. When the high-cut frequency is 20 kHz that means the response is 3 dB down at 20 kHz so you've still got some slight attenuation at, say, 15 kHz. So for the sake or accuracy it now goes to 40 kHz which pushes that pole well outside the audible range." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-3-00-public-beta-2.113734/page-3#post-1360576] </blockquote>

<blockquote>"The high cut frequency is due to the snubber cap in the PI. Friedman's use 100 pF (or more) for the snubber cap. A DSL only uses 47 pF so, yes, you would need to double the high cut frequency to match." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-05.149428/page-6#post-1773457]</blockquote>

<blockquote>"A snubber is a network used to reduce high frequencies. The term is a bit misused in tube amps. Typically a snubber is used to absorb transients in power circuits (like when a switch opens/closes). In a tube amp the "snubber cap" is a capacitor across the plates of the phase inverter (PI). This reduces the gain of the power amp at high frequencies. It was originally used to prevent the power amp from oscillating. Some modern amps employ large values for tone shaping." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-05.149428/page-6#post-1773475]</blockquote>

==PREAMP SAG==

From the Owners Manual:
<blockquote>
"Turning this ON causes the amp block to behave like an integrated tube head or combo amp. Turning this OFF simulates a separate preamp and power amp."
</blockquote>

==PREAMP TUBE HARDNESS==

Previously called: TRIODE HARDNESS (before firmware Cygnus 16 for the Axe-Fx II). [http://forum.fractalaudio.com/axe-fx-ii-discussion/91241-triode-hardness.html#post1098468]

From the Owners Manual:
<blockquote>
"This parameter controls how sharply the triodes enter saturation and can be used to simulate softer or harder tubes. The lower the value the softer the distortion. Higher values will cause the overtone series to have a less steep decay and will increase perceived “sparkle”. Use this control with Preamp Bias to control how chimey and “round” the tone is."
</blockquote>

The default value is 5.0 and is set to this value whenever the type is changed. The effect of this is subtle and most apparent at edge of breakup. Lower values give softer saturation, higher values give a more aggressive breakup.

Fractal Audio explains:

<blockquote>"What the parameter does now is control the asymmetry of the triode model. The higher the value, the more asymmetrical the clipping." [http://forum.fractalaudio.com/threads/v-10-triode-hardness.67091/#post-826849]</blockquote>

<blockquote>"Lower values will have less even and more odd harmonics. The smoothness/harshness of distortion is a function of the ratio of even to odd harmonics. The more symmetrical the clipping, the more odd and less even harmonics." [http://forum.fractalaudio.com/threads/v-10-triode-hardness.67091/#post-826877]</blockquote>

<blockquote>"The default hardness value is based on the tubes that were in the amp being modeled. Most tubes fall in the range of 8 to 9. Perhaps old Mullards or Gold Lions or whatever are softer and would be equivalent to 5 or less. I don't know, I've never tested any. In general lower values will sound softer (naturally) but have less note separation. Higher values will give a more aggressive distortion and better note separation. There are no rules. Adjust the value to your personal preference. I doubt a real tube would ever be able to get to a value of zero but that doesn't mean it isn't a useable sound." [http://forum.fractalaudio.com/threads/axe-fx-ii-firmware-v11-02-and-new-preset-banks.74402/page-4#post-910797]</blockquote>

<blockquote>"If you are right on the edge of breakup the triode hardness is very powerful as it controls the harmonic series. Higher values will cause the overtone series to have a less steep decay and will increase perceived "sparkle". Together with the preamp bias you can control how chimey and "round" the tone is (preamp bias effectively controls the ratio of even/odd harmonics)." [http://forum.fractalaudio.com/threads/more-gain-in-11-01.74457/#post-911002]</blockquote>

<blockquote>"Triode Hardness at zero gives a smoother distortion with reduced upper harmonics. However if you carefully compare a real tube preamp with the Axe-Fx models you'll clearly hear the difference as you reduce Triode Hardness. It's even more apparent when you compare the distortion spectrum. It's yet even more apparent when you use measurement techniques that learn the proper value." [http://forum.fractalaudio.com/threads/downgrading-to-fw9.76826/page-5#post-938344]</blockquote>

<blockquote>"The primary controls to adjust the saturation behavior are Preamp Tube Type, Preamp Hardness and Preamp Bias. (...) Preamp Hardness allows you to adjust how soft the saturation is." [http://forum.fractalaudio.com/threads/suggestions-on-what-youve-done-to-enjoy-18-03.97925/page-9#post-1178319]</blockquote>

<blockquote>"You can control the "shape" of the preamp and power amp distortion. The Preamp Hardness parameter controls the shape of the triode emulations. The lower the value the softer the distortion. The Power Amp Hardness controls the power amp clipping but that often is not noticeable because negative feedback around the power amp makes the distortion harder. Therefore you can make the power amp distortion softer by reducing Negative Feedback. A good example of this is a JCM800. A JCM800 has very hard preamp distortion (since there is no cathode bypass cap on the last stage) but has low negative feedback which softens the power amp distortion. The trick with that amp is to get the amp into the sweet spot by increasing the MV until you are getting some power amp distortion which softens the preamp distortion." [http://forum.fractalaudio.com/threads/scratchy-sound-on-this-patch-same-for-you.100622/page-2#post-1207496]</blockquote>

<blockquote>"There are two primary parameters associated with our preamp tube models. "Preamp Hardness" determines how abrupt the tube clips when it enters the saturation region. There is another parameter that determines how nonlinear the tube is between cutoff and saturation. This is currently not exposed to the user." [http://forum.fractalaudio.com/threads/anyone-not-a-fan-of-quantum-6.121353/page-3#post-1446007]</blockquote>

<blockquote>"0.00 is not symmetrical. In fact there is no value that is symmetrical." [http://forum.fractalaudio.com/threads/preamp-tube-type.122604/#post-1459051]</blockquote>

==TRIODE 1+2 PLATE FREQUENCY==

From the Owners Manual:
<blockquote>
"These parameters set the cutoff frequency of the last two triodes in the chain. Many amps have a capacitor across this triode’s plate resistor. This capacitor is used to smooth the response and reduce noise. You can adjust the amount of capacitance, and the resulting frequency, using these parameters."
</blockquote>

Fractal Audio explains:
<blockquote>
"It sets the cutoff frequency of the resistor/cap combination on the plate of the last triode stage (the previous stages are not user adjustable). Most amps have no cap on the last stage but a few do. You can vary this parameter to simulate increasing/decreasing the capacitor value. The frequency is only approximate since the actual frequency varies with the bias point/cathode impedance/drive/etc." [http://forum.fractalaudio.com/threads/amp-block-triode-plate-frequency.38144/#post-521777]
</blockquote>

<blockquote>
"This parameter sets the cutoff frequency of the plate impedance for the next-to-last triode in the chain. Many amps have a capacitor across this triode’s plate resistor. This capacitor is used to smooth the response and reduce noise. You can adjust the amount of capacitance, and the resulting frequency, using this parameter. The last triode plate capacitor is also exposed: Triode2 Plate Freq."
</blockquote>

==PREAMP BIAS==

From the Owners Manual:
<blockquote>“This adjusts the bias point of the last triode stage. This is the most important stage in the feel and texture of distortion, as it controls the ratio of even/odd harmonics. Values around zero will produce mostly odd harmonics. As you deviate from zero you’ll produce less odd and more even. Odd harmonics give clarity and a more aggressive, open tone but this can be cold and harsh. Adding even harmonics gives a warmer sound but too much and things can get muddy. Getting the right balance of even and odd harmonics is one of the keys to achieving “edge of breakup” tones.”
</blockquote>

Fractal Audio explains:
<blockquote>
"The further you move away from (roughly) zero the more even harmonics are introduced. It's an asymmetric transfer function, so you have to experiment." [http://forum.fractalaudio.com/threads/more-gain-in-11-01.74457/#post-911042]
</blockquote>

<blockquote>
"The primary controls to adjust the saturation behavior are Preamp Tube Type, Preamp Hardness and Preamp Bias. (...) Preamp Bias adjusts the bias point of the last triode stage which will control the ratio of even/odd harmonics. Values around zero will produce mostly odd harmonics. As you deviate from zero you'll produce less odd and more even." [http://forum.fractalaudio.com/threads/suggestions-on-what-youve-done-to-enjoy-18-03.97925/page-9#post-1178319]
</blockquote>

<blockquote>
"Bias points in an amp are important. The bias point of the last preamp stage is the most important. Therefore Quantum firmware exposes this bias point on the Pre Dyn tab as the Preamp Bias parameter. Most amps are biased slightly towards cutoff (negative). The closer you get to 0.0 the more odd harmonics and the fewer even harmonics. Experiment with this to craft your "Ultimate Tone" (TM, all rights reserved, use only as directed, these statements have not been evaluated by the FDA)." [https://forum.fractalaudio.com/threads/one-of-quantums-powerful-tools.104687]
</blockquote>

<blockquote>
"The Preamp Bias control in the Amp block controls the operating point of the last virtual triode stage in the preamp. This is the most important stage wrt to the feel and texture of distortion. The earlier stages are important but generally not nearly as much and the bias points are not exposed to the user. The operating point of a tube determines the symmetry of the clipping. If the tube is biased exactly halfway between the supply voltage and ground then it will clip symmetrically (greatly simplified). If the quiescent current is reduced the tube will biased more towards cutoff. If it is increased it will be biased more towards saturation. In general cutoff is smoother than saturation but it depends on the external circuitry. Negative values of Preamp Bias bias the virtual tube towards cutoff and positive values toward saturation. Symmetrical distortion has lots of odd harmonics and very little even harmonics. The more asymmetrical the distortion the more even harmonics are introduced. Odd harmonics give clarity and a more aggressive, open tone but this can be cold and harsh. Adding even harmonics gives a warmer sound but too much and things can get muddy. Getting the right balance of even and odd harmonics is one of the keys to achieving "edge of breakup" tones. Experiment with the bias point to find your optimum tone. Things get especially interesting when a cathode follower is involved. You can tell if an amp has a cathode follower if the Preamp Comp parameter is not zero. The cathode follower interacts with the last stage and slight adjustments to the bias point can cause major changes in the distortion characteristics. For example, the Dizzy Blue models are biased near zero (0.08 IIRC). If you play lightly you'll hear the bass is kind of stuffy and tubby. Reduce the Preamp Bias a bit and you'll hear the bass clean up. Too negative, however, and the sound can get indistinct. The good amp designers understand the interaction between the last stage and the cathode follower and tune the bias point for the desired distortion characteristics. The cathode follower is a bit of an imperfect design though. It's great for vintage Plexi and other high gain sounds but its clipping behavior is not ideally suited to certain tones. Therefore the Comp Type parameter allows you to choose an idealized cathode follower with different distortion characteristics (Comp Type == Ideal). Note that the behavior of this type is similar to the algorithms used in profiling modelers and other products. Try using the Ideal mode. You will likely need to reduce the amount of Preamp Comp as this mode has much more compression. Even amps that rely mostly on power amp distortion can benefit from fine tweaks to the Preamp Bias point. Shifting the bias point changes the harmonics into the power amp which changes the distortion character of the power amp (albeit less significantly)." [http://forum.fractalaudio.com/threads/preamp-bias.110726]
</blockquote>

<blockquote>
(firmware Ares 5.0) "The “Ideal” cathode follower type is no longer supported as it is incompatible and has been removed from the GUI."
</blockquote>

<blockquote>
"It's one of the main tools that amp designers use in voicing Marshall-style amps. For these amps you'll notice the amp gets tighter as you set Preamp Bias negative and chunkier for positive values. Too negative and things get thin and sputtery. Too positive and the lows get farty." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-5-02-firmware-released.120535/page-5#post-1434706]
</blockquote>

==PREAMP BIAS EXCURSION==

<blockquote>(Owners Manual) "Not to be confused with Bias Excursion on the Power Amp page, this is a separate parameter for the preamp. The higher the value, the more the bias shifts when the virtual tubes are overdriven."</blockquote>

Fractal Audio explains:
<blockquote>
"Bias Excursion is unrelated to the power supply stuff (sag, Variac, etc.).

Bias Excursion is grid bias shift caused by grid conduction. When a grid goes into forward conduction, charge "leaks" off the coupling capacitor. When the grid comes out of forward conduction the capacitor now has a net negative charge. This causes the bias point to shift negative.

Excessive bias excursion causes "blocking distortion".

Old amp designs, i.e. Fender 5E3 Tweed, exhibit copious bias excursion in the preamp and, hence, lots of blocking distortion. Part of its charm I suppose.

Power tubes also exhibit bias excursion. Some bias excursion in the power amp can be desirable. If you design the power amp in such a fashion so as the tubes go into forward conduction as the plates are clipping this will effectively reduce the bias and lower the gain causing the amp to "open up". To much bias excursion can cause excessive blocking distortion AND crossover distortion.

Designers can tailor the amount of bias excursion by adjusting the grid stopper resistor value."
[https://forum.fractalaudio.com/threads/rectifier-bias-excursion-time.179754/post-2194681]
</blockquote>

==TONESTACK TYPE + FREQUENCY + LOCATION==

The tonestack is the set of tone controls on an amplifier.

There are four main tone stacks used in most common guitar amplifiers: Marshall style, Fender style, Vox style, and the lesser used Baxandall or James style. These tone stacks vary in their construction, consisting of either a bass and treble control, or bass, mid, and treble controls. Some amplifiers have a tone stack consisting only of one control, usually a treble cut control, but sometimes it will be a single control that cuts treble at one end of the rotation, and cuts bass at the other end. These types of control are usually labeled "tone", or "cut". [http://www.aikenamps.com/index.php/a-glossary-of-common-amplifier-terms Source: Aiken]

'''Tonestack Type''' - it allows you to choose between various tonestacks.

<blockquote>(Owners Manual) “By default, the Bass, Mid and Treble controls operate as a “passive” tonestack: they simulate exactly the frequency and phase response of the classic passive tonestacks found in the original amplifiers many amp types are based on. This lets you change this behavior from “PASSIVE” to “ACTIVE”, or to substitute the passive tonestack of another amp.

Selecting a substitute tonestack allows you to mix and match amps and tone stacks to create your own hybrids. This allows you to use, for example, a Plexi-type tonestack on a Blackface amp model.

Selecting the “ACTIVE” type gives each tone control +/– 12 dB boost/cut operation for up to twice the range of a typical amplifier. Since the active tone controls are more sensitive, small adjustments have bigger effects. For example, full PASSIVE treble for a high-gain British amp would be equivalent to only +5.0 dB ACTIVE, leaving 7 dB of additional headroom! Active tone controls do not interact like those of a typical amplifier, so when you adjust the treble, the mid and bass are not affected. This can make dialing in a certain tone easier and quicker than it might be with a PASSIVE tonestack."

Selecting “Neutral” sets a well-behaved “hi-fi” kind of tone stack, where putting all the controls at noon will give you a flat response.

Selecting "Default" sets the default tone stack that comes with the flesh-and-blood amp.</blockquote>

'''Tonestack Freq''' - sets the center frequency of the tone controls to determine their effect on the sound. This control works whether you are using Active, Passive, or substitute tone stacks. This parameter defaults to an appropriate value whenever you change the amp TYPE, but it can then be changed as desired. But if you subsequently change the Tonestack Type, the Tonestack Frequency will not necessarily be correct anymore.

'''Tonestack Location''' - lets you change the location of the tone stack. “PRE” places the tone stack at the input to the virtual preamp, “POST” places the stack between the preamp and power amp. “MID” places it between the last two triode stages, and “END” places it after the power amp (which is physically impossible with a real amp).

<blockquote>(firmware 6) "Reworked most tone stacks based on amp matching results. In general most knobs now behave exactly like the actual amp when possible. In a few instances there may be minor discrepancies between the knob position of the model and actual amp due to programming constraints and/or peculiarities of the actual amp (such as poor potentiometer tolerance). Due to variations in presence circuit topologies the taper of the Presence parameter, in particular, may vary between the model and the actual amp. In other words, a different setting on the model may be required to achieve the same response as the actual amp. In most cases however, the Drive, Treble, Mid, and Bass knobs will be accurate to within 10% of the actual amp."</blockquote>

With some amp sims, such as the Lonestar, moving the tonestack location results in loss of volume.

<blockquote>"Whenever you set the bass and treble to zero the tone stack becomes basically "flat" and the mid becomes a volume control. Most tone stacks behave this way." [http://forum.fractalaudio.com/threads/interesting-find-eqs-at-zero-on-brit-pre-sounds-pretty-good.71226/#post-873182]</blockquote>

<blockquote>"Every amp model uses one of these tone stacks. Obviously as there are more models than tone stacks some models share tone stacks. If you set the Tone Stack Type to Default, the amp block will use the tone stack appropriate for that model. For example, the Plexi 50W models use the "Plexi" tone stack (not surprisingly). If you set the Type to Default then the selected tone stack will be the Plexi tone stack. If you set the Type to Plexi it will be the same tone stack. The reason I did it this way is so you don't have to remember what the default tone stack is for the model. Simply set the Type back to Default. BTW, the tone stack is one of the main things that gives an amp its particular voice. People wax on about NOS tubes and "vintage iron" and cloth insulation and other nonsense but at the end of the day it's 99% frequency response. The tone stack shapes the frequency response pretty drastically. Many so-called boutique amps are nothing more than a classic design with a tweaked tone stack. The Axe-Fx II is unique in that it is the only modeling device that accurately replicates a tone stack along with the interaction of the controls and influence of surrounding circuitry. I had to solve the mesh equations for each of the major tone stack types which wasn't easy. A tone stack is a 3rd-order network and coding that was a real challenge." [http://forum.fractalaudio.com/threads/when-to-change-the-tonestack-type.79267/#post-965179]</blockquote>

<blockquote>"A Deluxe Reverb, for example, has no Mid pot but a fixed resistor. The value of that resistor is 6.8K. If you use a "Fixed Mid" tone stack the value of the virtual resistor will be 6.8K when the Mid control is at noon." And: "If you use a "Fixed Mid" tone stack the value of the virtual resistor will be 6.8K when the Mid control is at noon." [http://forum.fractalaudio.com/threads/what-is-bf-fixed-mid-tone-stack.98757/#post-1185050]</blockquote>

<blockquote>"The Fat switch changes a value in the tone stack which changes the response of the stack, shifting the mid dip down and making it less pronounced. The Tonestack Freq. parameter frequency scales all the reactive components in the tone stack which is something quite different." [http://forum.fractalaudio.com/threads/fat-switch-is-totally-different-than-axe-fx-ll.145247/page-2#post-1718101]</blockquote>

<blockquote>"If you change the tone stack and don't change the frequency the tone stack will use the standard values. If you put a Dumble tone stack in a 5F8 you'll get a Dumble tone stack exactly as it is in a Dumble. If you change the frequency away from 470 Hz the tone stack values will scale." and "Tonestack Frequency is just a set number for each model. I was trying to make things less confusing than 0.1 - 10. When you select a tonestack it loads a tonestack model which is a bunch of resistor and capacitor values. When the tonestack loads it frequency scales the values based on the entered Tonestack Frequency divided by the default value. The default value matches that of the default tonestack. If you never touch the Tonestack Frequency then the tonestacks load unchanged (i.e. 700/700 = 1). When you select a different tonestack it's center frequency may be different than the default so the displayed frequency doesn't reflect that." [https://forum.fractalaudio.com/threads/match-tone-stack-to-frequency.147334]</blockquote>

<blockquote>"Tonestack Frequency is just a set number for each model. I was trying to make things less confusing than 0.1 - 10. When you select a tonestack it loads a tonestack model which is a bunch of resistor and capacitor values. When the tonestack loads it frequency scales the values based on the entered Tonestack Frequency divided by the default value. The default value matches that of the default tonestack. If you never touch the Tonestack Frequency then the tonestacks load unchanged (i.e. 700/700 = 1). When you select a different tonestack it's center frequency may be different than the default so the displayed frequency doesn't reflect that." [https://forum.fractalaudio.com/threads/match-tone-stack-to-frequency.147334/post-1804831] </blockquote>

<blockquote>"The following are the Fender tonestacks: [https://forum.fractalaudio.com/threads/differences-between-the-fender-tonestack-types-at-the-amp-block.165464/post-1985914]
Brownface: Brownface Vibroverb 
Blackface: Blackface Twin Reverb 
Bassguy: 59 Bassman 
Jr. Blues: Blues Junior 
Super Verb: Super Reverb 
BF Fixed Mid: Blackface with fixed mid resistor (6.8K) 
Vibrato-King: Vibro-king 
Vibrato-Lux: VibroLux 
Vibroverb AA: AA763 Vibroverb 
Super 6G4: Super Amp 6G4 
65 Bassman Bass: Bass channel of 65 Bassman 
Band-Commander: Blackface Bandmaster"
</blockquote>

<blockquote>"You can sweep the midrange frequency using the Tonestack Freq. control." [https://forum.fractalaudio.com/threads/no-option-for-active-tonestack.173832/post-2106254]</blockquote>

<blockquote>"Tonestack Freq frequency scales all the capacitors in the virtual tone stack. Even better than changing the slope resistor." [https://forum.fractalaudio.com/threads/blocks-between-preamp-and-power-amp.173335/post-2101589]</blockquote>

=Power Amp=

==POWER AMP MODELING==

Turns on/off power amp modeling in the Amp block.

Before this parameter was introduced in Cygnus firmware, power amp modeling could be turned off by turning down Supply Sag all the way.

When Power Amp Modeling is turned off, Master works as a simple volume, and Depth and Presence are deactivated.

<blockquote>(Cygnus) "With power amp modeling off the Presence control does nothing." [https://forum.fractalaudio.com/threads/modeling-questions.199009/post-2481687]</blockquote>

==NEGATIVE FEEDBACK==

From the Owners Manual:
<blockquote>
“This controls the amount of negative feedback, or damping, in the power amp simulation. Higher values give a tighter and brighter sound but can sound harsh at very high master volume levels. Lower values give a loose and gritty sound and feel. Like many other power amp parameters, Negative Feedback is set to an appropriate value whenever you change the amp type, but it can be changed as desired. For example, you might dial in some negative feedback on a “Top Boost” amp type to give the power amp a more “American” sound while still retaining the preamp voicing.”
</blockquote>

Changing Negative Feedback (Damping) between 0 and other values used to change the display on the hardware, and switch the Presence control between "Presence" and "HiCut". "Cygnus" amp modeling has changed this: Negative Feedback control no longer interacts with the Presence control. If you turn negative feedback to zero the Presence control won’t do anything as would happen on a real amp.

Adjusting negative feedback on a real amp impacts its volume. Fractal Audio manages this through automatic output level compensation, which works well when the power amp is not clipping (in firmware 23 and later this can be turned off). If the power amp is saturated, both Damping and Level must be increased to maintain the same level.

<blockquote>"The MV control behaves like the modeled amp. The compensation is only for NFB. If you turn NFB down the LEVEL out of the amp block is reduced and vice-versa. This way the volume stays relatively constant. Otherwise the volume changes drastically as you change the NFB." [https://thegearforum.com/threads/nmd-axe-fx-iii-mk-ii-turbo-j-f.3823/post-143580]</blockquote>

Firmware 23 release notes:
<blockquote>"Added NFB Compensation switch in Amp block. This defaults to On. Turning it off disables the negative feedback volume compensation at the output of the Amp block."</blockquote>

Fractal Audio explains:
<blockquote>
"The Axe-Fx attempts to normalize the volume as you change the damping. (...) However, if you are driving the "power amp" hard the equation falls apart because it assumes linear operation. Therefore there may be some volume change. This is done since otherwise you would constantly have to adjust your output volume as you change the damping. Unfortunately it is impossible to predict how saturated the power amp is since that depends on input level. The compensation isn't perfect, the idea is to minimize the volume fluctuations since without compensation the volume would fluctuate wildly." [http://forum.fractalaudio.com/threads/the-damp-control-is-strange.29243/#post-428774]
</blockquote>

<blockquote>
"Another factor which controls power amp hardness is Transformer Match. There are two primary distortion mechanisms in a power amp: grid clipping and plate clipping (PI clipping notwithstanding as this is only audible with a post-PI MV). Grid Clipping is extremely hard, almost a hard clipper (i.e. if(x>a) then x=a). Plate clipping is much softer. However most power amps are slightly undermatched which means the grids clip before the plates clip, but only at those frequencies where the speaker impedance is "nominal". At high frequencies (above 1kHz or so) the rising impedance of the speaker causes the plates to clip before the grids. At the low frequency resonance the plates also clip first. If you increase the transformer matching the plates will clip earlier and, since plate clipping is softer, the distortion will be softer. So turn up the Transformer Match and turn down Negative Feedback for softer power amp distortion." [http://forum.fractalaudio.com/threads/scratchy-sound-on-this-patch-same-for-you.100622/page-2#post-1207496]
</blockquote>

<blockquote>
"There are a two things that determine the smoothness of the power amp distortion:
# Power Amp Hardness. As you've discovered turning it down makes it smoother (obviously). The value controls the "kvb" of the tube model. It's the "knee voltage" for the plate. The formula for plate current is Ip = f(Vg1, Vg2) atan(Vp/kvb). The lower kvb the more abrupt the transition into clipping. Power Amp Hardness is the inverse of this normalized to the plate voltage.
# Negative Feedback. Negative feedback linearizes the power amp. At some point, though, the power amp then runs out of headroom and goes into clipping. The more negative feedback the more linear the response and the more abrupt the clipping. Less negative feedback, smoother clipping. 
I often turn P.A. Hardness down, usually between 3-4, because I like the smoother sound." [https://forum.fractalaudio.com/threads/power-amp-hardness.152582/post-1815292]
</blockquote>

<blockquote>
"Increasing negative feedback flattens the frequency response and increases linearity. You can achieve similar results by flattening the impedance curve in the Speaker page and increasing Power Tube Hardness." [https://forum.fractalaudio.com/threads/more-negative-feedback.153934/post-1829614]
</blockquote>

<blockquote>
"The more feedback the harder the distortion. Most people like less feedback. You also have to be careful as the greater the feedback the greater the chance of instability." [https://forum.fractalaudio.com/threads/evh-tone-deep-dive-feat-dave-friedman-and-pete-thorn.167641/post-2016591]
</blockquote>

From [https://forum.fractalaudio.com/threads/about-negative-feedback.79697/ Cliff's Tech Note]:

<blockquote>
"The Axe-Fx II allows the user to fine-tune the amount of negative feedback in the power via the Damping parameter. The term damping refers to the fact that increasing negative feedback lowers the output impedance and therefore "dampens" the response of the speaker. Power amps often specify their output impedance in terms of "Damping Factor" which is the ratio of the load impedance to the output impedance. The higher the damping factor the less the speaker impedance influences the frequency response. Let's examine what happens as you adjust the Damping parameter. As we increase the Damping we increase the negative feedback. This does several things:
* LOWERS THE GAIN of the power amp. This causes the power amp to not distort as easily since the signal is amplified less and therefore it won't clip as easily.
* Increases the linearity of the power amp. This reduces harmonic distortion but makes clipping "harder" as the transition to clipping is more abrupt.
* Flattens the frequency response. This makes the frequency response more linear and widens the bandwidth. The peaks in the frequency response due to the speaker impedance are flattened and broadened.
As we decrease Damping we decrease the negative feedback which does:
* Increases the gain of the power amp. The causes the power amp to clip more readily.
* Decreases the linearity of the power amp. This increases harmonic distortion and softens the transition into clipping.
* Increases frequency response distortion. The response becomes more scooped and the bandwidth is reduced.
Many guitar players like the sound of amps with no negative feedback. The Vox AC-30 is the classic example of an amp with no negative feedback. The power amp distortion is soft and the scooped response along with lots of harmonic distortion give a bell-like tone for high frequencies and warm low frequency response. The drawback to this is that the low end can get muddy as the low frequencies clip readily due to the frequency response distortion. These types of amps typically do not work well for high-gain tones although there are notable exceptions, i.e. the Dual Rectifier which uses a high-power power amp and bass reduction in the preamp to compensate for the increased bass response.
Fender and Marshall amps (and their derivatives) use varying amounts of negative feedback. The amount of feedback in Marshall amps was all over the map in the early years and seems as though the builders didn't really adhere to rigorous documentation and revision control. As such there can be quite a bit of variation in the sound of these early Marshalls.
So what is the correct amount? There is no definitive answer however there are some guidelines. For more vintage tones less Damping is typically desirable. This gives softer power amp breakup and more "baseline" distortion. For modern, high-gain tones more Damping may be desirable as these tones typically rely on preamp distortion and the power amp is desired to be neutral (which many players describe as "tight"). As stated before the Dual Rectifier in modern modes is a bit of an enigma. The power amp in this mode uses no negative feedback. You can hear this as an increase in volume when you flip the switch to Modern (remember that negative feedback reduces the gain so turning it off will increase the gain).
I have read some users recommending increasing the Damping to reduce the amount of power amp distortion in, for example, Fender models. I do not endorse this viewpoint. The distortion is primarily reduced because the gain is reduced but the power amp will sound more "sterile" due to the increased linearity and flatter frequency response. A better solution is to simply lower the Master Volume. This drives the power amp less while retaining the baseline harmonic distortion, softer transition into clipping and more scooped frequency response.
Modification of the error signal is commonly employed in guitar amps. This was first employed as the ubiquitous Presence control. The presence circuit reduces the amount of feedback at higher frequencies. Since the gain of the power amp is inversely proportional to the amount of feedback, reducing the amount of feedback over only a certain range of frequencies will therefore increase the gain of the amp at those frequencies. The presence control therefore boosts high frequencies. This concept was extended to low frequencies via the Depth or Resonance control. Basically these controls are bass and treble controls for the power amp but operate by reducing the feedback for those bands. On most amps setting these controls fully CCW will basically remove them from the circuit. Turning them CW will reduce the feedback in the prescribed bands thereby increasing the gain of these bands. An exception are Boogie (Mark series) power amps. The presence control in these amps is more complex and the flattest frequency response is achieved with the knob set to noon. Turning the knob CCW will reduce the treble response. Turning it CW will increase it.
Note that these all interact with the Damping control. To hear this reduce the Damping to a value just greater than zero. Note that the Presence and Depth controls will have almost no effect. This is logical since B (beta) is nearly zero and we can't reduce it further."
</blockquote>

Also see Aiken's White Papers
"[http://www.aikenamps.com/index.php/designing-for-global-negative-feedback Designing for Global Negative Feedback]" and "[http://www.aikenamps.com/index.php/what-is-negative-feedback What is Negative Feedback?]".

Fractal Audio:

<blockquote>"These are my notes for the various Plexis:

* Plexi 50W: 100K from 4-ohm tap
* 1987x: 100K from 8-ohm tap
* Plexi 100W: 47K from 8-ohm tap (off speaker jack with two 16-ohm cabs)
* Plexi 100W 1970: 100K from 4-ohm tap
* 1959SLP: 47K from 8-ohm tap
* Plexi 6550: 100K off 4-ohm tap
* 50W Normal - Normal channel. 100K feedback from 4-ohm tap. Cathode cap on second triode.
* 50W High 1 - Treble channel. 100K feedback from 4-ohm tap. No cathode cap on second triode.
* 50W High 2 - Treble channel. 100K feedback from 4-ohm tap. Cathode cap on second triode.
* 1987x Normal - Normal channel. 100K feedback from 8-ohm tap. No cathode cap on second triode.
* 1987x Treble - Treble channel. 100K feedback from 8-ohm tap. No cathode cap on second triode.

You need to know what tap the feedback is from. Going down a tap decreases the feedback by 0.707. Conversely going up a tap increases the feedback by1.414. Up two taps doubles the feedback (4-ohm to 16-ohm).

FWIW, our reference Plexis are 1967 and 1968. I've never seen one with a 27K feedback resistor. That's pretty low so I have to assume it's from the 4-ohm tap. If that is the case you would want to multiply the feedback by about 3.3. So if it's 1.5 you would set it to 4.95.

I've seen JTM45s with 27K off the 16-ohm tap. That's a lot of feedback. In this case you would then double the feedback on top of the 3.3 so 9.9 or so." [https://forum.fractalaudio.com/threads/negative-feedback.188769/post-2340401]</blockquote>

==PRESENCE FREQUENCY==

From the Owners Manual:
<blockquote>
"This multiplier alters the center frequency of the Presence control."
</blockquote>

==DEPTH FREQUENCY==

From the Owners Manual:
<blockquote>
"This multiplier alters the center frequency of the Depth control."
</blockquote>

==MASTER VOLUME CAP==

<blockquote>(Owners Manual) "Sets the value of the bright cap across the Master Volume control."</blockquote>

<blockquote>"Setting it to 1 pF defeats it." [http://forum.fractalaudio.com/threads/axe-fx-ii-firmware-v11-02-and-new-preset-banks.74402/page-2#post-910428]</blockquote>

==MASTER VOLUME LOCATION==

From the Owners Manual:
<blockquote>
"Sets the location of the Master Volume control. Most amps have the Master Volume before the phase inverter (“Pre PI”). On some amps (like the “Class-A” types) the Master Volume comes after the phase inverter (“PI”). A third option, “pre-triode,” is the default for “Hipower” amp types."
</blockquote>

Fractal Audio explains:
<blockquote>
"Most amps are Pre-PI, including Dumbles. Post-PI is rare and often does as a mod. This causes the PI to distort rather than the power tubes. It is a harsher sound."
</blockquote>

<blockquote>
"Moving the Master Volume after the Phase Inverter. This causes the phase inverter to distort. It is a popular mod on amps. In the Advanced menu change MV Location to "Post-PI"." [http://forum.fractalaudio.com/threads/post-pi-mv-try-it.84166/#post-1020827]
</blockquote>

<blockquote>
"Post-PI MV, Try It! Turns a lot of mid-gain amps into ripping monsters. I just tried it on the JCM800 and, dayum... The only caveat is that, like a real amp, the more you turn the MV down the less effective Presence and Depth become (since the loop gain is reduced)." [http://forum.fractalaudio.com/threads/post-pi-mv-try-it.84166]
</blockquote>

<blockquote>
"The swing of a properly designed PI is greater than the range of the power tube grids. For example a 6L6 will typically be biased around -50V. This gives a range of around 100V of swing at the power tube grids. A well-designed PI for an amp like this will typically swing at least 150V and usually closer to 200V or more. This means the grids clip before the PI clips. Then there are the power tube plates. Most designers choose the output transformer so that the plates just start to clip when the grids clip. This gives maximum power since current is maximum when the grids are driven to clipping so you want the plate voltage to be at its maximum excursion at this point. This is a matter of taste. Some designers slightly undermatch since the impedance of the speakers increases at low and high frequencies and this gives a more open tone. Others overmatch as this give a more touch-sensitive overdrive (i.e. Trainwrecks). When you put the MV after the PI you attenuate the signal from the PI going to the grids. This allows the PI to clip before the grids clip. The PI has a fair amount of negative feedback so it's a somewhat hard clipper which gives a fairly aggressive distortion." [http://forum.fractalaudio.com/threads/post-pi-mv-try-it.84166/#post-1021130]
</blockquote>

<blockquote>
"Post-PI is after the phase inverter. It won't do anything until you turn it down. At 10 the location is irrelevant because the control is wide open. Put it at, say, 5 and switch between the locations. The effect should be pretty dramatic. Post-PI is also known as the Lar/Mar master volume mod." [https://forum.fractalaudio.com/threads/fas-crunch-plexi-mv-location.180552/post-2207841]
</blockquote>

==XFORMER DRIVE (TRANSFORMER DRIVE)==

From the Owners Manual:
<blockquote>
"This models core saturation in the virtual output transformer. Higher values simulate a smaller, more easily saturated transformer. The distortion produced by an overdriven output transformer isn’t particularly pretty but it does play a role in the tone and without it the distortion would not be authentic."
</blockquote>

Transformer is often abbreviated to: XFRMR or XFORMER.

Fractal Audio explains:
<blockquote>
"Transformer Drive models the core saturation in the output transformer. The Drive increases the amount of core saturation." [http://forum.fractalaudio.com/threads/does-the-transformer-drive-parameter.39352/#post-535233]
</blockquote>

<blockquote>
"Don't overlook this when striving for "vintage" tones. I was playing around with this last night and it's very powerful in making edge-of-breakup tones sound like an old, well-played amp (if that's your thing). The higher you set the drive the more it saturates the virtual transformer's core. It doesn't affect the B+, that's done with the Sag parameter." [https://forum.fractalaudio.com/threads/tranformer-drive.41252]
</blockquote>

<blockquote>
"The size of the transformer is dictated by the necessary power handling. You can simulate smaller/larger transformers by adjusting the Transformer Drive parameter." [http://forum.fractalaudio.com/threads/x-former-match.63263/page-2#post-784589]
</blockquote>

<blockquote>
"Part of the sound of certain tube amps, particularly those who derive their distortion from power amp overdrive, is attributable to the output transformer. The distortion produced by an overdriven output transformer isn't particularly pretty but it does play a role in the tone and without it the distortion would not be authentic. When a transformer is overdriven the iron core saturates. This happens because all the magnetic domains are aligned with the field and no more can be "rotated". In engineering terms the flux density (B) no longer increases linearly with the flux intensity (H). Since a transformer presents an inductance to the power tubes the flux intensity is inversely proportional to the frequency applied. Therefore the distortion increases at lower frequencies. Manufacturers frequently specify the frequency response of the transformer at its rated power. For example Hammond specifies most of its output transformers of having a bandwidth of 70 Hz to 15 kHz (re. 1 kHz +/- 1 dB) at rated power. The bandwidth of the transformer, however, will be much greater when operated below it's rated power. The Axe-Fx II allows the user to adjust the amount of output transformer saturation via a parameter called XFRMR DRV (Transformer Drive). Lower values decreases the amount of distortion, higher values increase it. The parameter is normalized to a rated-power lower-frequency cutoff of 40 Hz, i.e. a value of 1.0 means that the virtual output transformer will have a lower cutoff frequency (-3 dB point) of 40 Hz when the virtual power amp is operating at the rated power of the transformer. So, if the transformer has a rated power of 50W and the lower cutoff frequency is 40 Hz at that power, setting XFRMR DRV to 1.0 will duplicate that behavior. The formula for rated power cutoff frequency is simply D = f_c / 40, where D is the drive level and f_c is the desired cutoff frequency. For example if we wanted to duplicate the aforementioned Hammond transformer we would first need to find the equivalent -3 dB frequency which is roughly 3/4 assuming it's -2 dB at 70 Hz (since they strangely specify +/- 1 dB) which would be about 50 Hz. Plugging into the formula we get D = 50 / 40 = 1.2. As always use your ears. I personally prefer a setting of around 1.5 - 2.0 for clean-to-lightly distorted tones. I find it adds a bit of richness to the bass frequencies. For higher gain tones I prefer less as it can sound muddy. Note that the effect of output transformer distortion is highly dependent upon the how hard the virtual power amp is driven which is a function of Master Volume and overall gain. There are lots of strange things that happen with an OT saturates but those are trade secrets and I can't elaborate further." [https://forum.fractalaudio.com/threads/transformer-drive.85592]
</blockquote>

<blockquote>
"Lowering the default value of Transformer Drive is similar to upgrading the hardware transformer."
</blockquote>

<blockquote>
"The transformer stuff is very subtle until you turn up Transformer Drive. Turn it up to 3-4 and it gives a cool compression and growl to the low end." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-15-01.168349/post-2022294]
</blockquote>

==XFORMER MATCHING (TRANSFORMER MATCHING)==

From the Owners Manual:
<blockquote>
“Transformer Matching is an extremely powerful parameter. Lower values cause power tubes to clip later and therefore the phase inverter and grid clipping becomes more predominant. At higher settings, power tubes clip sooner and the Resonance settings on the Speaker page become more pronounced. For optimum results bring up the Master until the desired amount of power amp distortion is achieved, then adjust Matching until the character of the distortion is as desired. The various LF and HF Resonance parameters interact strongly with this parameter, so be sure to experiment with those as well when crafting a tone.”
</blockquote>

Fractal Audio explains:
<blockquote>
If you want to simulate a speaker impedance mismatch you use Speaker Impedance. If you want to adjust the transformer impedance ratio you use Transformer Match." [https://forum.fractalaudio.com/threads/updated-speaker-impedance-control.171289/post-2105261]
</blockquote>

Firmware 19.06 release notes:

<blockquote>
"Speaker Impedance in firmware 19.06 and later models the interaction of the virtual transformer and speaker. The Transformer Matching parameter sets the impedance ratio (square of the turns ratio) of the output transformer. And the Speaker Impedance parameter sets the relative nominal impedance of the speaker. Example: to simulate connecting, e.g., a 4-ohm speaker to an 8-ohm output, set Speaker Impedance to 0.5. Conversely to simulate connecting a 16-ohm speaker, set it to 2.0."
</blockquote>

Decrease the value to make the amps sound more “broad”.

Fractal Audio explains:
<blockquote>
"What to use Transformer Match for: The turns ratio of transformers varies by manufacturer, era, etc. For example the original Drake transformers used in old 50W Marshalls had a primary impedance of 3.5K. Some newer transformers have an impedance of 3.2K, about 10% less. To replicate this set Transformer Match to 0.9. This will give a more "open" sound but also a harsher distortion. Increase matching to simulate a higher primary impedance. This will give a more compressed and smoother distortion. Some amps intentionally overmatch their transformers (Trainwrecks) which gives them their characteristic sound." [https://forum.fractalaudio.com/threads/transformer-match-vs-speaker-impedance.154391/post-1835564]
</blockquote>

<blockquote>
"This is an extremely powerful parameter that sets the relative output transformer primary impedance which in turn controls how easily the power tubes are driven into clipping. The higher the Master Volume setting the more pronounced the effect of this parameter. Decreasing the matching causes the power tubes to clip later and therefore the phase inverter and grid clipping becomes more predominant. Increasing the matching causes the power tubes to clip sooner. At lower settings the speaker resonance will be more pronounced, at higher settings the speaker resonance will be less pronounced. For optimum results bring up the Master until the desired amount of power amp distortion is achieved, then adjust the matching until the character of the distortion is as desired. The various LF and HF resonance parameters interact strongly with this parameter so be sure to experiment with those as well when crafting your ideal tone. The value of this parameter is relative to the actual transformer matching which is set internally and not directly exposed. The value is reset to 1.0 whenever they amp type is selected."
</blockquote>

<blockquote>
"Very powerful control. Use in moderation. It changes the turns ratio of the virtual output transformer. Primary impedance is a function of turns ratio. As you increase the turns ratio you increase the impedance by the square of the turns ratio: Zp = N^2 * Zs. An easier description: Increasing Transformer Match -> Thick. Decreasing Transformer Match -> Scooped." [https://forum.fractalaudio.com/threads/5-04-adv-parameters-xformer-match.48005/post-625102]
</blockquote>

<blockquote>
"One of the most powerful controls in the Amp Block Is Transformer Match. If you want a more "open" sound and feel, turn it down. If you want more compressed sound and feel, turn it up. A little goes a long way. Note that this control has more or less effect depending upon the setting of the Master Volume. Transformer Match has more influence at higher MV values and vice-versa. If you turn TM down, you may want to turn MV up to compensate and vice-versa. Turning it way up (around 2.0), for example, simulates the sound of running an 8-ohm speaker on the 4-ohm tap." [http://forum.fractalaudio.com/threads/one-of-the-most-powerful-controls-in-the-amp-block.52338]
</blockquote>

<blockquote>
"Don't overlook this parameter when your MV is set high. It is extremely powerful. A little in either direction can make a big difference. If you want a more open tone, turn it down slightly. If you want more compression and sustain, turn it up a bit. This parameter is essentially a "turns ratio" for the OT." [https://forum.fractalaudio.com/threads/transformer-match.56382]
</blockquote>

<blockquote>
"Higher values are "warmer" but more compressed. Lower values are more open but harsher. Only small adjustments are needed. Transformer Match is the single most powerful advanced parameter when dealing with non-MV amps (i.e. when you have the MV cranked)." [http://forum.fractalaudio.com/threads/warmth-from-6-0-to-9-0.59934/#post-747355]
</blockquote>

<blockquote>
"The most powerful advanced parameter is Transformer Match. When people try different tube brands or rebias their amp to use a different type of tube they make all kinds of hyperbolic claims about those tubes but it isn't really the tube that made the difference. Well it is but it's not because the tube is doing something special. It's simply because the tube has a different transconductance (gain). Amp designers choose an OT turns ratio such that the amp is "matched" to the load. However "matched" is a nebulous term since tube gains vary, speaker impedance is variable and bias point is adjustable. Therefore there is no absolute turns ratio that ensures perfect matching. Matching implies that the swing at the power tube grids just pushes the plates to the rails. If the output transformer is undermatched, the grids will clip before the plates hit the rails and vice-versa. Designers also select the turns ratio based on personal preference. Some designers prefer undermatched OT since this gives a more "open" sound, while others prefer overmatched since this gives more touch response. For example, a Trainwreck is highly overmatched. For a given OT, if the tubes have higher gain than originally then this effectively overmatches the OT and vice-versa. Now this matters most for non-MV amps that get their distortion from the power amp, i.e. old Marshall, Fender, etc. So... if you are going to experiment with any advanced parameter, start with Transformer Match. A little bit in either direction can make a big difference. Note that the Transformer Match parameter is relative to the internal value." [https://forum.fractalaudio.com/threads/the-most-powerful-advanced-amp-parameter.61820]
</blockquote>

<blockquote>
"Transformer match has nothing to do with the physical size of the transformer. It is the turns ratio. The higher the turns ratio (higher Transformer Match) the higher the reflected impedance from the speaker and vice-versa. The higher the value the sooner the power tubes distort. The optimum turns ratio is such that the maximum power can be obtained. Tube amps tend to be slightly undermatched though since the speaker impedance is not constant. This varies with the make/model of amp and is encoded in the model data. The size of the transformer is dictated by the necessary power handling. You can simulate smaller/larger transformers by adjusting the Transformer Drive parameter." [http://forum.fractalaudio.com/threads/x-former-match.63263/page-2#post-784589]
</blockquote>

<blockquote>
"The internal default value is based on the amp that was modeled and an assumed speaker voice coil resistance of 0.8 times the nominal impedance. I.e., if the speaker is rated at 8 ohms the assumed voice coil resistance is 6.4 ohms. Some speakers are slightly below this, others are above. 16-ohm Celestion Greenbacks, for example, are about 12 ohms so that would 0.75 times the nominal impedance. To simulate this you would reduce the matching to 0.75/0.8 = 0.9375. If you find yourself lowering this value consistently then your Master Volume is too high (assuming it's a MV amp). If it's a non-MV amp and you still find yourself lowering this value then you'll probably find the tone harsh or too scooped at loud volumes. In general I find people set the MV too high on MV amps. I think they don't realize that most MV amps achieve full volume around 2-4 on the MV knob and then it's just compression after that. Amp makers are partly to blame here as they do this on purpose to make their amps seem louder than they really are. Of course the sweet spot is that point at which the power amp starts to compress so you want to set the MV high enough to get into the sweet spot. It's a psychological thing. People always like a more "open" sound even though they don't really understand what makes a tone "open". When you lower the Transformer Match you reduce the power tube compression of the lows and highs. The problem is humans naturally gravitate to this to the point that they will make the tone excessively "open" and then it doesn't fit in the mix. I do not recommend deviating much from 0.9 - 1.1. Of course there are no rules. With real amps some people like that more open sound and achieve it by plugging their cab into the higher impedance output, i.e. plugging an 8-ohm cab into the 16-ohm jack. This would be equivalent to setting the match to 0.5. SRV liked it the other way round IIRC which would equate to a match value of 2.0." [http://forum.fractalaudio.com/threads/fw-11-03-xformer-match-settings.75161/#post-919805]
</blockquote>

<blockquote>
"Guitar folklore has it that SRV and Joe Walsh intentionally mismatched their speaker impedance. I imagine others have done this. The general idea is you plug an 8-ohm speaker into the 4-ohm jack or vice-versa. The Axe-Fx allows you to replicate this behavior using the Transformer Match control. To simulate plugging an 8-ohm speaker into the 4-ohm jack set Transformer Match to twice it's current setting (i.e. 2.0). For the other way around set it to half (i.e. 0.5). And you don't have to worry about frying your OT." [https://forum.fractalaudio.com/threads/simulating-speaker-impedance-mismatch.77944]
</blockquote>

<blockquote>
[https://forum.fractalaudio.com/threads/the-secret-weapon-transformer-match.98527/ Cliff's Tech Note]: "One of the most important "advanced tweaks" in the amp block is the Transformer Match parameter (XFRMR MATCH). This control sets the relative turns ratio of the virtual output transformer. Each amp model has a default turns ratio embedded in the model data. The Transformer Match parameter adjusts that ratio relative to this default value. Turning it down reduces the ratio and makes the transformer "undermatched". Turning it up increases the ratio and makes the transformer "overmatched". Why is this important? In a "classic" designed power amp the transformer turns ratio is selected to provide the full power the output tubes are capable of to the load. IOW, when the tubes are delivering their maximum current the voltage at the plates is near zero (the voltage swing is maximum) for the NOMINAL speaker impedance. If the transformer is undermatched the tubes won't fully saturate. If the transformer is overmatched the tubes will saturate early. Most guitar amps are slightly undermatched. This wouldn't really matter than much if the load were a simple resistance but a speaker is a reactive load. As mentioned in my other posts the impedance has a low-frequency resonance and a high-frequency boost. If the transformer were perfectly matched then the plate voltages would reach maximum excursion when the current was at a maximum only at those frequencies where the speaker impedance equals the nominal impedance. When the speaker impedance is greater than the nominal impedance the tubes saturate early. This has the effect of distorting the highs and lows before the mids. If you decrease the matching the highs and lows don't distort as quickly and the amp will sound more "open". However the distortion can be harsher since power tube current limiting is harder than voltage limiting. If you increase the transformer matching the highs and lows will distort sooner and the amp will sound more "compressed. The resulting distortion will be smoother due to the softer nature of the voltage limiting. As explained above a classic design selects the turns ratio to give the maximum power for the nominal speaker impedance. However the "nominal" speaker impedance is just that and the actual speaker impedance varies considerably from model to model. The impedance of a typical 8-ohm speaker can vary 20% or so. If the actual impedance is lower then this effectively undermatches the transformer and vice-versa. Furthermore the transconductance and maximum current capability of the power tubes varies. For example, the amp models in the Axe-Fx that use EL34s were modeled with Mullard tubes (as these are considered the best sounding). A set of JJ EL34s will actually produce slightly more current and saturate earlier. This effectively overmatches the output transformer. Some amps deliberately overmatch the output transformer, i.e. Trainwrecks. This results in a smoother power amp distortion with more compression of the highs and lows. The amount of overmatching is considerable, typically about 50% Now, the effect of the transformer matching is only evident when the power amp is distorting. Non-MV amps get most of the distortion from the power amp so the effects of altering this parameter should be readily apparent. Master Volume amps get most of their distortion from the preamp so the effects of altering this control may not be as noticeable if the MV is turned down. Small adjustments can make a big difference. I typically never adjust more than 20% (0.8 to 1.2) and usually less than 10%. If you find your tones are slightly too open and harsh turn up the Transformer Match slightly. Conversely if you find your tones too compressed turn it down a bit. Be warned that turning it down may seem to sound "better" because the volume will increase (our old friends Fletcher and Munson again) but then when you play loud it will be boomy and harsh. You want some of those high and lows to be distorted early so that things aren't too scooped."
</blockquote>

<blockquote>
"Another factor which controls power amp hardness is Transformer Match. There are two primary distortion mechanisms in a power amp: grid clipping and plate clipping (PI clipping notwithstanding as this is only audible with a post-PI MV). Grid Clipping is extremely hard, almost a hard clipper (i.e. if(x>a) then x=a). Plate clipping is much softer. However most power amps are slightly undermatched which means the grids clip before the plates clip, but only at those frequencies where the speaker impedance is "nominal". At high frequencies (above 1kHz or so) the rising impedance of the speaker causes the plates to clip before the grids. At the low frequency resonance the plates also clip first. If you increase the transformer matching the plates will clip earlier and, since plate clipping is softer, the distortion will be softer. So turn up the Transformer Match and turn down Negative Feedback for softer power amp distortion. However... designers know all this and they design an amp to sound best in a mix (at least the good ones do). Soft clipping sounds great when you are playing by yourself but as soon as you are in a band context the sound gets lost since hard clipping helps cut through the mix. Amps designed for rock typically have harder clipping than an amp designed for blues or jazz. A 5150, for example, has an extreme amount of negative feedback which makes the power amp very linear and clips very hard. A Deluxe Reverb, otoh, has low negative feedback and large cathode bypass caps on the last preamp stage. This makes the clipping softer and the sound less "clear"." [http://forum.fractalaudio.com/threads/scratchy-sound-on-this-patch-same-for-you.100622/page-2#post-1207496]
</blockquote>

<blockquote>
(firmware Ares 9) "New power amp modeling algorithm. This new algorithm now also separates the transformer matching from the speaker impedance. A new parameter, Speaker Impedance, allows adjusting the relative impedance of the virtual speaker. For example, to simulate connecting a 16-ohm speaker to an 8-ohm output set Speaker Impedance to 2.0. Transformer Matching, on the other hand, changes the impedance ratio of the virtual output transformer."
</blockquote>

<blockquote>
(firmware Ares 9) "Prior to 9.xx the "matching" was controlled by a single Transformer Match parameter. 9.xx introduces a new Speaker Impedance parameter. The distortion of a tube power amp is dependent upon the load presented to the power tubes. The overall sound, however, is also often dependent upon the voltage at the speaker since that voltage is fed back to the input." [https://forum.fractalaudio.com/threads/transformer-match-vs-speaker-impedance.154391/post-1835564]
</blockquote>

<blockquote>
(firmware Ares 10) "The range of the Transformer Match control has been reduced to 0.5 to 2.0. Existing presets will have this value reset to 1.0."
</blockquote>

Aiken has more information:
* [http://www.aikenamps.com/index.php/output-transformers-explained White Paper: Output Transformer]
* [http://www.aikenamps.com/index.php/a-glossary-of-common-amplifier-terms Glossary]

==SPEAKER IMPEDANCE (VOICE COIL RESISTANCE)==

"Speaker Impedance" was temporarily renamed "Voice Coil Resistance", and got its original name again in firmware 19.06 for the Axe-Fx III.

Speaker Impedance in firmware 19.06 and later models the interaction of the virtual transformer and speaker. The Transformer Matching parameter sets the impedance ratio (square of the turns ratio) of the output transformer. And the Speaker Impedance parameter sets the relative nominal impedance of the speaker. Example: to simulate connecting, e.g., a 4-ohm speaker to an 8-ohm output, set Speaker Impedance to 0.5. Conversely to simulate connecting a 16-ohm speaker, set it to 2.0.

Earlier:

<blockquote>(firmware 19.02) "Renamed Speaker Impedance to Voice Coil Resistance to more accurately describe the function of the control. Note that this includes all other “parasitic” resistances, i.e., speaker cable resistance, output transformer winding resistance, etc."</blockquote>

<blockquote>(firmware Ares 9) "New power amp modeling algorithm. This new algorithm now also separates the transformer matching from the speaker impedance. A new parameter, Speaker Impedance, allows adjusting the relative impedance of the virtual speaker. For example, to simulate connecting a 16-ohm speaker to an 8-ohm output set Speaker Impedance to 2.0. Transformer Matching, on the other hand, changes the impedance ratio of the virtual output transformer."</blockquote>

<blockquote>"Leave it at 1.0 for accuracy. When you select an impedance curve the actual speaker impedance is part of that data (but hidden from the user). The exposed Speaker Impedance control scales that loaded impedance." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-19-01.180998/post-2220824]</blockquote>

If you are using an MV amp (i.e. 5150) then you really don't need to adjust Speaker Impedance. If you want a more scooped sound lower the MV and vice-versa. Speaker Impedance is a useful control for non-MV amps (i.e. Plexis).

<blockquote>(firmware Ares 9) "Prior to 9.xx the "matching" was controlled by a single Transformer Match parameter. 9.xx introduces a new Speaker Impedance parameter. The distortion of a tube power amp is dependent upon the load presented to the power tubes. The overall sound, however, is also often dependent upon the voltage at the speaker since that voltage is fed back to the input.

What to use Speaker Impedance for: The actual impedance of a speaker can vary quite a bit. For example a Celestion Greenback is available in 8 and 16 ohm versions. The 8-ohm version has a DC resistance (DCR) of 6.57 ohms. The 16-ohm version has a DCR of 12.13 ohms. The Plexi models in the Axe-Fx assume 16-ohm speakers were used as the Marshall cabs used 16-ohm speakers.

The DCR normalized to the speaker impedance is therefore different for the two versions. For the 8-ohm version the DCR normalized to the impedance is 6.57/8 = 0.82. The 16-ohm version is 12.13/16 = 0.76. The relative impedance is therefore 0.82/0.76 = 1.08. Therefore the 8-ohm version of the speaker will increase the voltage at the primary by 8% which means the power amp breaks up a bit earlier (more gain). To simulate this increase Speaker Impedance to 1.08.

All the models use a DCR commensurate with the original speakers when available. For amp heads with no matching cabinet the DCR is assumed to be 6.7 ohms. I contemplated naming the control "Speaker DCR" but figured that was too vague but it's actually a better description of what the control does (and the internal parameter name is speaker_dcr).

Another use for Speaker Impedance is to simulate intentional mismatching. SRV, Joe Walsh, etc. would intentionally mismatch their amps by connecting the speaker to the "wrong" output jack. For example, to simulate connecting a 16-ohm speaker to the 8-ohm output jack set Speaker Impedance to 2.0 (or 1.9 in the case of a Greenback)." [https://forum.fractalaudio.com/threads/transformer-match-vs-speaker-impedance.154391/post-1835564]</blockquote>

<blockquote>"The Speaker Impedance Curves include the D.C.R. If you select, for example, the 4x12 Basketweave, its D.C.R. is 14.0 ohms. So if you have a cab with an actual D.C.R. of 14.5 the Speaker Impedance value would be 14.5 / 14.0 = 1.036." [https://forum.fractalaudio.com/threads/updated-speaker-impedance-control.171289/post-2105192]</blockquote>

==PHASE INVERTER BIAS EXCURSION==

From the Owners Manual:
<blockquote>
"Controls how much the virtual phase inverter bias shifts when overdriven."
</blockquote>

Fractal Audio explains:
<blockquote>
”PI Bias Excursion controls the virtual Phase Inverter bias excursion. It's a subtle effect on most amps but some amps display significant bias excursion, i.e. Trainwreck Express. It's a form of blocking distortion.” [https://forum.fractalaudio.com/threads/pi-bias-excursion.157062/post-1871331]
</blockquote>

Firmware 19.01 for the Axe-Fx III:

<blockquote>
"Improved Phase Inverter Bias Excursion accuracy for some amp models (mostly non-MV types). Note: The improved PI Bias Excursion accuracy results in an increase in bias excursion in most cases. Bias excursion primarily manifests as intermodulation distortion, particularly subharmonic distortion. This produces a chunkier tone with more growl and also yields a thicker tone when rolling off the volume or playing lightly. The amount of bias excursion can be adjusted using the PI Bias Excursion control in the Advanced menu."
</blockquote>

==CATHODE RESISTANCE==

From the Owners Manual:
<blockquote>
"There are two types of power tube bias: fixed bias and cathode bias. In a cathode biased amp a resistor is placed between the power tube cathode and ground thereby self-biasing the tube. This parameter sets the value of the virtual cathode resistor. Higher values result in a more negative bias and push operation towards Class-B, resulting in more crossover distortion."
</blockquote>

Fractal Audio explains:
<blockquote>
"Sets the cathode resistance of the power tubes. Should only be used with "Class A" amps, i.e. AC-20 DLX, etc. Lower values increase the bias current. Note that some amps have separate bias resistors while others have a shared bias resistor. The choice of split/shared is not exposed to the user." [http://forum.fractalaudio.com/threads/cathode-resistance.122674/#post-1459417]
</blockquote>

<blockquote>
"P.A. Cathode Resistance is the normalized value of the resistance seen by the cathodes of the virtual power tubes. Higher values bias the tubes colder (from Class-AB towards Class-B) and result in more crossover distortion (fizz). Lower values bias the tubes hotter and result in a smoother character." [https://forum.fractalaudio.com/threads/believe-it-or-not-cant-get-the-tweed-amps-to-sounds-fizzy-enough.168701/post-2026831]
</blockquote>

==CATHODE TIME CONSTANT==

From the Owners Manual:
<blockquote>
"This sets the time constant of the virtual RC cathode network for amp types that are cathode biased."
</blockquote>

==PLATE SUPPRESSOR DIODES==

Added in firmware 21 for the Axe-Fx III. Release notes:

<blockquote>"Added “Plate Suppressor Diodes” parameter. This value is set automatically when the amp model is chosen but the user can override the default setting. Most amps do not have suppressor diodes but some do (e.g., Trainwreck Express). These diodes (also called “snubber” or “flyback” diodes) prevent undershoot on the power tube plates due to inductive kick and reduce upper harmonics thereby reducing “fizz”."</blockquote>

Tech Note: [https://forum.fractalaudio.com/threads/about-the-plate-suppressor-diodes-parameter.188142/post-2333785]

<blockquote>"The new "Cygnus X-2" amp modeling introduced a new parameter called "Plate Suppressor Diodes". Plate suppressor diodes, also known as "snubber" or "flyback" diodes are diodes connected between the power tube plates and ground.

The purpose of these diodes is to clamp the inductive "kick" caused by the reactive load seen by the plates. A speaker is a reactive load and has a positive reactive component at high frequencies. This means it looks inductive. Inductors resist change in current. When the plate voltage drops rapidly to zero the inductance of the load causes the voltage to undershoot.

A suppressor diode clamps the voltage and prevents undershoot. This does two things:
1. It prevents excessive voltage at the plates and transformer primary. This protects the transformer from damage due to dielectric breakdown.
2. It also reduces "fizz". The undershoot manifests as increased high frequency content in the range where the load is inductive, typically from 1kHz and up.

Most amps don't have flyback diodes but there are a handful of notable exceptions: Trainwreck Express, Fender Blues Jr., Peavey 5150, and several others.

Flyback diodes were originally added to amps to protect the output transformer but most, if not all, techs don't realize that they also change the clipping behavior.

[[image:Snubber_diodes.PNG|link=]]

The blue trace is a plot of a tube power amp output with no flyback diodes. The green trace is the same power amp with flyback diodes. Those spikes in the voltage are what can damage a transformer and also what cause "fizz".

In a real tube amp these diodes are under intense stress and may fail. In our virtual world these diodes are indestructible.

So if you like your tones as fizz-free as possible experiment with the Plate Suppressor Diodes parameter. Note that turning them on will reduce the "chime" at edge-of-breakup and may not be suitable for vintage tones."
</blockquote>

<blockquote>"That's what amps do. You don't hear it through a guitar cab typically but using close-mic'd IRs it's more noticeable. You can reduce it by turning on the Plate Suppressor diodes. Trainwrecks have plate suppressor diodes for just this reason." [https://forum.fractalaudio.com/threads/note-decay-crackle-sizzle-noise.193575/post-2407689]</blockquote>

=Power Tubes + Cathode Follower (CF)=

==POWER TUBE TYPE==

From the Owners Manual:
<blockquote>
“Changes the characteristics of the virtual amp power tubes. The virtual power amp includes modeling of the plate impedance of the power tubes. Plate characteristics are adjustable via Dynamic Damping, an advanced parameter. The Tube Type parameter allows you to select from common power tube types: 6AQ5, 6L6/5881, 6V6, 300B (triode), 6550, 6973, EL34/6CA7, EL84/6BQ5, KT66, KT77, KT88, 5881 and 6L6GB.”
</blockquote>

<blockquote>
"Selecting a Power Tube Type loads the “knee voltage” for the power tubes and this voltage can be adjusted up or down using Power Tube Hardness. Higher values yield a lower knee voltage and more abrupt clipping and vice-versa. Existing presets will have Power Tube Hardness reset to 5.0 upon recall."
</blockquote>

<blockquote>
(Axe-Fx II) "Added Tube Type parameter to amp block. This allows selecting Tetrode (i.e. 6L6, KT66, etc.) or Pentode (i.e. EL34, 6BQ5, etc.) power tube types. The type defaults to the appropriate value when a model is chosen but may be overridden by the user."
</blockquote>

<blockquote>
(Axe-Fx II) "Added selectable power tube types for Amp block. Available types are: EL34, EL84, 6L6, 6V6, KT66, KT88, 6550, 6973, 6AQ5 and 300B (triode). Also available are an ideal tetrode and ideal pentode. The power tube type defaults to the appropriate type when the amp type is selected but may be overridden by the user. The power tube type presets the Dynamic Damping parameter as well as several internal parameters."
</blockquote>

Fractal Audio explains:
<blockquote>
"The tubes are "normalized" so that you don't have to do anything to the transformer. The internal values for the power tubes are based on typical transformer values. For example, the values derived for the EL34 are based on a primary impedance of 3200 ohms (assuming one pair of tubes). The impedance ratio of the transformer affects the values slightly as the plate impedance is reflected to the secondary (or the load is reflected to the primary) and the ratio therefore affects the interaction." [http://forum.fractalaudio.com/threads/axe-fx-ii-firmware-version-12-04-public-beta.80497/page-5#post-977955]
</blockquote>

<blockquote>
[https://forum.fractalaudio.com/threads/why-power-tubes-sound-different.79962/ Cliff's Tech Note]: "You'll often read that 6L6's sound "full" whereas EL34's have more midrange and other colloquial descriptions of the tone of a power tube. These myths are perpetuated by forum dwellers, uninformed tube "experts" and even amp manufacturers as marketing tools. Well, the fact is that power tubes do NOT sound different. They do not have any intrinsic tone. "But I can hear the difference when I change to a different type of power tube. How can that be?" A power tube has a very flat frequency response and they all clip roughly the same. If you put a resistive dummy load on a tube power amp (assuming it doesn't have any intentional frequency shaping) it will measure very flat. However a speaker is not a resistive load. A speaker is a highly reactive load. As I've mentioned in the other threads in this forum section a speaker has an impedance that is sort of scooped at the midrange frequencies. It is the impedance of the speaker that affects the tone of the amp and different types of power tubes react differently with that impedance. As I've mentioned before a power tube is nearly a current source. The operative word here is "nearly". No power tube has an infinite plate impedance and that's why power tubes sound different. A current source has infinite output impedance, an actual power tube has a finite output impedance. The output impedance of a power tube (or any active device for that matter) is defined as delta V / delta I which is the change in voltage vs. the change in current. Let's take a 6L6 for example. Let's assume that the tube has a quiescent operating point of 300V and let's assume we swing +/- 100V around that point. If we look at the plate graphs for a 6L6 at a bias of -10V we see that the plate current at 200V is 95 mA and at 400V it's 105 mA (roughly). Using our formula for impedance we get 200/0.01 = 20 Kohms. Now let's take an EL34. At 200V the current is 130 mA and at 400V the current is 150 mA. The plate impedance is therefore 10 Kohms which is half that of the 6L6. This lower output impedance "de-Q's", or flattens, the speaker impedance. Essentially the EL34 has a higher damping factor than a 6L6. This higher damping factor reduces the mid-scoop due to the speaker impedance. This makes the tone have more midrange. There's a little more to it as the output transformer plays a role as well and 6L6 power amps typically have a slightly higher impedance ratio. There's also different operating voltages and bias points but I'm trying to keep this simple. You can simulate changing power tubes in the Axe-Fx by simply increasing or decreasing the LF and HF resonance values."
</blockquote>

<blockquote>
"Changing the power tube between pentode and tetrode doesn't change the sound in the same way actually changing tubes would because it only changes the distortion curves. It does not change the transconductance so the transformer matching is constant. When you put different power tubes in an amp the difference in tone isn't due to some inherent difference in the "sound" of the tubes. It's mainly due to the different transconductances. The transconductance of an EL34 is about 30-40% more than the transconductance of a 6L6 ([http://forum.fractalaudio.com/threads/preamp-tube-types.94404/#post-1131521 edited]). This means that the plate current will be twice as great for a given grid voltage. This makes EL34s sound "more midrangey" and 6L6s sound "tighter" or "fuller". The truth is that if you bias them correctly and compensate for the difference in transconductance you will hear very little difference. Unfortunately you can't compensate for the transconductance easily in a real amp without changing the gain of the phase inverter and/or putting in a different output transformer." [http://forum.fractalaudio.com/threads/mark-v-tone-match.75082/#post-924520]
</blockquote>

<blockquote>
"There won't be the same variation you would get by substituting in a real amp because the transformer matching stays consistent. IOW, if you put an EL84 in a Plexi the transformer matching is going to be way too low because the transconductance is very different. The power tube models normalize the transconductance so switching power tubes also effectively installs the correct output transformer For example, a pair of EL-84s want around 8K primary impedance. A pair of EL-34s want around 3.2K. If you put EL-84s in a Plexi the transformer will then be very undermatched (and probably burn the tubes up). In the Axe-Fx if you change the tube type to EL-84 you get all the parameters of an EL-84 but the virtual transformer will be changed so that the matching stays the same. You will get the crunchier tone of the EL-84 though since its knee voltage (kvb) is roughly half that of an EL-34." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841268]
</blockquote>

<blockquote>
"There are a variety of parameters loaded when a tube type is selected. Hardness, which is inversely proportional to the knee voltage, is exposed to the user as it is the most audible." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841317]
</blockquote>

<blockquote>
(about Mesa's Mark IV Pentode/Triode switch) "There isn't any way to run the virtual power tubes in triode mode... but you can change the Power Tube Type to "300B" which is a triode. When you run a pentode (or beam tetrode) in triode mode you connect the screen to the anode which effectively defeats the screen. This lowers the output impedance of the plate significantly which, in turn, lowers the output impedance of the amp itself making the voltage output less dependent on the speaker impedance. Using the 300B tube type should get you pretty close." [https://forum.fractalaudio.com/threads/mesa-mark-iv-pentode-triode-switch.122527/post-1458293]
</blockquote>

<blockquote>
"The Axe-Fx automatically adjusts the output transformer to match the power tubes so the difference isn't nearly as apparent as it would be if you were to change the tubes in a real amp. In other words a pair of EL-34s wants to see about 3200 ohms whereas a pair of 6L6s want to see about 4000 ohms. The Axe-Fx III automatically increases the transformer matching if you change the tubes from EL-34 to 6L6. I've been debating removing this "mu normalization" but it would break existing presets where people had changed the tubes from the default type."
</blockquote>

And:

<blockquote>
“All the tube models are "normalized". IOW if you change tube types the bias current stays the same, the transconductance (mu) is the same, etc. All that changes are the tube parameters that determine the shape of the I/V curves. The reason for this is you would never put EL-84s in an amp designed for 6L6s. First of all they wouldn't fit, but more importantly the bias circuit would be all wrong and the transformer impedance ratio would be way off. It would sound completely wrong. What you mostly hear when you swap tubes in a real amp is the change in the transconductance and concomitant transformer mismatch. The curves aren't really all that much different. In fact the parameters for 6L6s and EL34s aren't all that different aside from the mu. A JJ 6L6GC has roughly the same parameters as a Mullard EL34. kvb for both is around 30V, the big difference is mu which means a pair 6L6s want a primary impedance of 4K whereas a pair of EL34s want around 3.2K. If you put 6L6s in an amp designed for EL34s the OT will be undermatched which will make the amp sound more "open" and the power amp won't distort as much. You also run the risk of redplating the tubes because you might go outside the SOA.So, all this being said, the biggest tools in your arsenal are the Transformer Match and Speaker Impedance parameters which can be used to simulate different matching." [https://forum.fractalaudio.com/threads/power-amp-power-tube-type-selection.155021]
</blockquote>

<blockquote>
(firmware Ares 12.09) "Added 6CA7 power tube type. While the 6CA7 is generally regarded as a substitute for the EL34 it is actually a different tube with the 6CA7 being a beam tetrode. This particular tube type is modeled after the original Sylvania “Fat Bottle” 6CA7."
</blockquote>

<blockquote>
"You can only use the transconductance values when changing between tubes with roughly the same maximum power dissipation. It doesn't work if you want to change a 6L6 to an EL84.

I know everyone wants this to work like a real amp but it's simply not going to happen. Some amps let you swap between EL34s and 6L6s and change bias accordingly. The problem is the Axe-Fx III lets you change between all the possible tube types. If you were to put an EL84 into an amp designed for EL34s it would sound terrible (and also destroy the EL84). A pair of EL84s wants to see upwards of 8K plate-to-plate. A pair of EL34s wants to see around 3.2K. If you put the EL84s in the amp the transformer would be extremely undermatched. It would also exceed the SOA of the tube and destroy it. In the Axe-Fx III the virtual tube wouldn't be destroyed but it would sound terrible and people would complain it doesn't sound right.

Those amps where you can use different power tubes don't swap the transformer. They just rebias the tubes. If the transformer turns ratio is optimized for 6L6s installing EL34s will cause the transformer to be slightly undermatched which is the primary reason the tone changes. Conversely if the transformer is optimized for EL34s installing 6L6s will cause it to be overmatched.

You have far more control over the power tube response with the Axe-Fx. Rather than complaining that swapping power tubes doesn't work exactly the same learn to use the fantastic power available to you. Learn to hear the difference changing the Transformer Matching and/or Speaker Impedance makes. These are controls you'll never find on a real amp. Changing the matching on a real amp involves removing the transformer and installing a new one. If you want fine gradation in matching you'd need something with many taps." [https://forum.fractalaudio.com/threads/no-differences-when-changing-tubes.163545/post-1962569]
</blockquote>

<blockquote>
"As it stands I don't change the transconductance when changing tubes. The problem is if I did change the transconductance things would change dramatically if, for example, going from a 6L6 to an EL84. An EL84 has around twice the transconductance. In a real amp you can't put EL84s in an amp designed for 6L6s. What I change are the parameters that control the frequency response and distortion." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-19-00.180535/post-2209626]
</blockquote>

Seymour Duncan talks about this further in "[https://www.seymourduncan.com/blog/latest-updates/know-your-amp-different-kinds-of-tubes Know Your Amp: Different Kinds of Tubes]".

==POWER TUBE GRID BIAS==

From the Owners Manual:
<blockquote>
“Sets the bias point of the virtual power amp. Lower values approach pure Class-B operation. Higher values approach pure Class-A operation.”
</blockquote>

Fractal Audio explains:
<blockquote>
"For as long as I can remember I've always biased my amps around 60% of maximum dissipation. But I just ran across a site that claims 70% is optimal for a Class-AB amp. So I tried it on my go-to Plexi patch and I do believe it sounds better. Set Power Tube Grid Bias to 0.7 to do this." [https://forum.fractalaudio.com/threads/hmmmm-bias-point.154630/post-1838912]
</blockquote>

<blockquote>
"The early Cygnus betas were colder than the later betas. Originally I had set the bias equal to the reference amps but many of the reference amps are biased cold because most manufacturers bias amps cold from the factory for warranty reasons. In the later betas I put the bias points at where a technician would typically bias an amp after replacing the tubes, i.e. 60-70% of max. plate dissipation." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-12-cygnus-firmware-public-release-candidate.172027/post-2076897]
</blockquote>

<blockquote>
To simulate an amplifier running in Class A, turn up Power Tube Grid Bias.
</blockquote>

<blockquote>
"Turn up Power Tube Grid Bias. In real life that is tough on tubes as it makes them run very hot." [http://forum.fractalaudio.com/threads/replicating-the-bogner-ecstasy-class-a-mode.145294/#post-1718463]
</blockquote>

<blockquote>
"Yes, turn Power Tube Grid Bias all the way up." [https://forum.fractalaudio.com/threads/mesa-mk-4-class-a-possible.154438/post-1836241]
</blockquote>

<blockquote>
[https://forum.fractalaudio.com/threads/why-your-amp-doesnt-sound-like-our-amp.172907/post-2090367 Why Your Amp Doesn't Sound Like Our Amp]: 
"The transconductance (gain) of a power tube can vary greatly. This is why power tubes are color coded, sold in matched sets, etc. Amps come in two flavors: fixed bias and cathode bias. Fixed bias amps apply a "fixed" voltage to the grid of the power tubes. Cathode bias amps use a resistor between the cathode and ground to self bias the tube. Most, but not all, fixed bias amps allow the user to adjust the bias point of the amp. This allows the bias point to be set to an optimum value for the particular set of tubes installed (since the transconductance can vary greatly). Some fixed bias amps do not allow adjustment. Examples are Mesa/Boogies, 5150s, and several other brands/types. The drawback of this is that the bias can vary greatly depending upon the gain of the tubes installed. Due to this the manufacturers err on the safe side and the bias is usually much colder than the ideal value. Most cathode biased amps are not adjustable. Again you are at the mercy of the tube's gain but these amps tend to be biased hot to begin with and have higher transformer matching which prevents excursion outside of the S.O.A. (safe operating area). If the bias is adjustable where the manufacturer decides to bias their tubes is a matter of preference. Most manufacturers bias their tubes on the cold side to prevent premature failure and reduce warranty claims. Especially the larger manufacturers. This leads to the question of "what is the ideal bias point?" The pervasive school of thought is you adjust the bias so the idle dissipation is 60-70% of the tube's peak power rating. This is a safe approach and ensures that the tubes don't "red plate" and live fairly long and prosperous lives. My opinion is that the ideal bias point is NOT a function of the tube's power rating. It's the point at which the power amp's transfer function is most linear. Unfortunately operating the tubes at that point can result in exceeding the tube's S.O.A. So the optimum bias point depends on the tube's power rating, the transformer primary impedance (matching) and the user's tolerance to tube replacement frequency. For example, if we bias an EL34 based power amp at 60% peak dissipation it's actually running fairly cold. If we know that the transformer is slightly overmatched we can bias the tubes hotter, 70% or even more. This will result in a warmer tone but the tubes will wear faster. What does all this mean? Well, I bias the virtual tubes on the warm side. EL34s are biased at around 70% because we don't have to worry about them wearing out. 6L6s are biased a little colder, around 60% but this is actually as "warm" as the EL34s because of the higher plate dissipation of a 6L6. In practice this means that the models in the Axe-Fx will biased warmer than a new amp straight out of the box as most amps are biased cold (too cold IMO). After you wear the tubes out and bring it to a tech the tech will replace those tubes and bias them hotter than factory. So if you're comparing your new, out-of-the box 5150 with the Axe-Fx model the amp will probably sound "colder". Some people like this, many do not. If you like a colder sounding power amp it's just a knob twist away."
</blockquote>

<blockquote>
"To reduce/eliminate crossover distortion increase Power Tube Grid Bias. A value of 1.0 will have no crossover distortion." [https://www.thegearpage.net/board/index.php?threads/axe-fx-iii-effects.2260258/post-32648602]
</blockquote>

<blockquote>
"There is not a linear relationship between the grid bias value and quiescent dissipation as a percentage of maximum. 0.5 is roughly 66% IIRC but I'd have to run the numbers again to be sure.

With a real tube amp there is no hard-and-fast rule. Some say 60%, some say 70%. But that's a simplistic view of the problem. The optimum value is dependent on many things: B+ voltage, transformer turns ratio, etc. For example, if the transformer is overmatched you can run the bias hotter and this is indeed how some amps are designed (i.e. Trainwrecks).

The reason for the "rule" in tube amps is to reduce crossover distortion while also preventing premature wear to the power tubes. The hotter the bias the more linear the response. However too much bias and there's the danger of the tubes momentarily operating outside the SOA which shortens tube life. Even if you stay within the SOA if you operate near the limits you'll shorten tube life. If you overmatch the transformer you move the load line and increase the SOA margin so you can increase the bias.

The Axe-Fx is immune to tube wear so there is no danger in running the bias hot if you like that sound. However the hotter the bias the less dynamic the response becomes. Also some people like a bit of crossover distortion. Legend has it that EVH liked his amps biased cold. Whether that was because of the added dynamics or the extra grit due to crossover distortion is unknown.

As always the correct answer is what sounds best." [https://forum.fractalaudio.com/threads/grid-bias-value.178012/post-2168640]
</blockquote>

<blockquote>
"The question is which amp? A 1968 100W Plexi with over 500V on the plates or a 50 watter with around 360V on the plates? The response of those two amps will be completely different at the same quiescent dissipation due to the different plate voltages. The 100W amp will require around 35 mA for 70% dissipation. The 50W amp will require 48 mA. Since the transconductance of a tube is fairly independent of the plate voltage the 50W amp will be operating in a much more linear region. However, it will clip the grids sooner. If you load up, say, a 1959SLP model in the Axe-Fx you'll notice the bias is lower than the 50W versions. This is why. This is also why a lot of people prefer the 50W Plexis.

Then we need to ask what type and brand of power tubes? NOS? The response of the tubes is dependent upon the exponent in the tube equation. The original Childs-Langmuir law says that the exponent is 1.5 but real tubes exhibit an exponent somewhere between 1.2 and 1.5. The greater the exponent the less linear the response.

Finally we need to ask what is the output transformer primary impedance. Is it 4K per pair? Is it 3.6K? Is it 3.2K? Primary impedance was all over the map in those days.

All these things interact. The hotter the bias the more linear the response, the higher the gain, the sooner the grids clip, etc. A good amp designer will balance all these things along with the transformer matching to get the desired response.

The correct answer is turn it up/down until it sounds how you want." [https://forum.fractalaudio.com/threads/grid-bias-value.178012/post-2168744]
</blockquote>

<blockquote>
"So-called Class-A amps (like the AC30) don't actually exhibit much power supply sag because, well, they're Class-A (or nearly). The tubes are biased hot so when one tube is conducting more the other is conducting less and the net supply current doesn't change much. Contrast this with Class-AB where when one tube conducts the other goes into cutoff causing a net increase in supply current and concomitant supply sag. What Class-A amps do exhibit is "cathode squish". The capacitor on the cathodes charges up and shifts the bias point. This reduces the gain and acts as a sort of compressor. It's a unique compression and the amp "opens up" at the same time and crossover distortion increases."[https://www.thegearpage.net/board/index.php?threads/does-this-sound-like-an-ac30-to-you.2325505/post-34009664]
</blockquote>

==POWER TUBE HARDNESS==

From the Owners Manual:
<blockquote>
(Owners Manual) “Selecting a Power Tube Type (above) loads the appropriate “knee voltage” for the selected power tubes. This voltage can be adjusted up or down using Power Tube Hardness. Higher values yield a lower knee voltage and more abrupt clipping and vice-versa.”
</blockquote>

<blockquote>
(firmware Ares 10.00) "Due to the changes in the power amp modeling algorithm the Power Tube Hardness parameter now behaves differently. Selecting a Power Tube Type loads the “knee voltage” for the power tubes and this voltage can be adjusted up or down using Power Tube Hardness. Higher values yield a lower knee voltage and more abrupt clipping and vice-versa. Existing presets will have Power Tube Hardness reset to 5.0 upon recall."
</blockquote>

Before firmware Ares 10.00, this controlled the hardness (shape) of the virtual power tube grid clipping. Higher values have a more abrupt transition into saturation. This parameter changes automatically when switching virtual power tubes.

Fractal Audio explains:
<blockquote>
"The hardness is tied to the tube type. I.e., if a model uses EL84s the default hardness will be 2. Different tube types will default to different hardness." [http://forum.fractalaudio.com/threads/fw-18-06-amps-automatically-set-to-power-amp-hardness-of-4-instead-of-3-medium.98572/#post-1182388]
</blockquote>

<blockquote>
"You can control the "shape" of the preamp and power amp distortion. The Preamp Hardness parameter controls the shape of the triode emulations. The lower the value the softer the distortion. The Power Amp Hardness controls the power amp clipping but that often is not noticeable because negative feedback around the power amp makes the distortion harder. Therefore you can make the power amp distortion softer by reducing Negative Feedback. A good example of this is a JCM800. A JCM800 has very hard preamp distortion (since there is no cathode bypass cap on the last stage) but has low negative feedback which softens the power amp distortion. The trick with that amp is to get the amp into the sweet spot by increasing the MV until you are getting some power amp distortion which softens the preamp distortion. Another factor which controls power amp hardness is Transformer Match. There are two primary distortion mechanisms in a power amp: grid clipping and plate clipping (PI clipping notwithstanding as this is only audible with a post-PI MV). Grid Clipping is extremely hard, almost a hard clipper (i.e. if(x>a) then x=a). Plate clipping is much softer. However most power amps are slightly undermatched which means the grids clip before the plates clip, but only at those frequencies where the speaker impedance is "nominal". At high frequencies (above 1kHz or so) the rising impedance of the speaker causes the plates to clip before the grids. At the low frequency resonance the plates also clip first. If you increase the transformer matching the plates will clip earlier and, since plate clipping is softer, the distortion will be softer. So turn up the Transformer Match and turn down Negative Feedback for softer power amp distortion." [http://forum.fractalaudio.com/threads/scratchy-sound-on-this-patch-same-for-you.100622/page-2#post-1207496]
</blockquote>

<blockquote>
(firmware Ares 6.01) "As you decrease Power Amp Hardness now the volume won't decrease, it'll just get smoother. I like reducing it on "Class A" amp types sometimes." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-6-01.151534/post-1803390]
</blockquote>

<blockquote>
"There are a two things that determine the smoothness of the power amp distortion:
# Power Amp Hardness. As you've discovered turning it down makes it smoother (obviously). The value controls the "kvb" of the tube model. It's the "knee voltage" for the plate. The formula for plate current is Ip = f(Vg1, Vg2) atan(Vp/kvb). The lower kvb the more abrupt the transition into clipping. Power Amp Hardness is the inverse of this normalized to the plate voltage.
# Negative Feedback. Negative feedback linearizes the power amp. At some point, though, the power amp then runs out of headroom and goes into clipping. The more negative feedback the more linear the response and the more abrupt the clipping. Less negative feedback, smoother clipping. 

I often turn P.A. Hardness down, usually between 3-4, because I like the smoother sound." [https://forum.fractalaudio.com/threads/power-amp-hardness.152582/post-1815292]
</blockquote>

<blockquote>
"There are parameters not exposed to the user that are changed. Hardness is a relative parameter. Specifically it's a multiplier on the tube's kvb. I.e., if the tube has a kvb of, say, 20, and you turn hardness to 10 the actual kvb becomes 5 (lower kvb equals "harder" response)." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-19-00.180535/post-2207828]
</blockquote>

<blockquote>
"Also depends on how hard the power amp is being driven. If the power amp isn't being driven into clipping then the type of tube doesn't make much difference. The key to a high-gain amp is getting the right blend of preamp and power amp distortion. Start with the MV low and dial in your tone. Then raise the MV until the headroom meter just starts to hit 0 dB. This is beginning of the "sweet spot". Experiment with higher/lower MV until you get the right blend of distortion and compression. Back off the preamp gain as necessary. Vintage amps got almost all their distortion from the power amp. Over the years designers added gain to the preamp. Modern amps get most of their distortion from the preamp but without a little power amp distortion things can sound flat and compressed. Preamp distortion isn't lively like power amp distortion." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-19-00.180535/post-2207848]
</blockquote>

<blockquote>
"The distortion of the Kemper is smoother than a real amp. You can replicate this by decreasing the Power Amp Hardness." [https://forum.fractalaudio.com/threads/axe-fx-iii-clean-amp-sounds-compared-to-kemper-cleans.151497/post-1804532]
</blockquote>

==POWER TUBE MISMATCH==

From the Owners Manual:
<blockquote>
“Use this to simulate a gain mismatch between the virtual push and pull power tubes. A value of zero represents perfectly matched tubes.”
</blockquote>

==POWER TUBE BIAS EXCURSION==

From the Owners Manual:
<Blockquote>
“Controls how much the grid bias shifts when the virtual power tube grids are overdriven."
</Blockquote>

<blockquote>
“The higher the value, the more the bias shifts when the virtual power tubes are overdriven. Bias excursion pushes a power amp from Class-AB operation towards Class-B operation, which can result in crossover distortion. A little goes a long way, but too much can lead to what is referred to as “blocking distortion” which can make an amp sound unpleasant.“
</blockquote>

Fractal Audio explains:
<blockquote>
"Bias excursion (in the power amp) occurs because the power tube grids forward conduct when the grid voltage is slightly greater than the cathode voltage. Now this isn't a problem by itself. However almost all tube amp designs use a capacitor coupled grid circuit. The phase inverter is coupled to the power tube grids via a capacitor. When the grid voltage exceeds the cathode voltage, which is typically zero volts in a fixed-bias topology, the grid will become forward-biased and look like a low resistance. This clamps the grid side of the coupling capacitor. This occurs when the phase inverter signal is large and swings toward the B+ supply. When the phase inverter signal swings the opposite direction the grid stops conducting and the capacitor is no longer clamped. However there is now excess charge on the capacitor. During the time the capacitor was clamped charge was building up on the phase inverter side. When the grid comes out of conduction that charge effectively reduces the power tube bias. For example, a typical 6L6 is biased around -50V. The clamping action would then push the bias voltage even more negative, say -75V. In some designs the the bias voltage can be reduced by nearly 100%! Since the bias voltage is shifted the phenomenon is referred to as "bias excursion". Like cathode squish, bias excursion pushes the power amp from Class-AB operation towards Class-B operation. As we know Class-B operation has lots of crossover distortion. Now this may seem bad but, in fact, there are positive attributes associated with bias excursion. When designed correctly bias excursion can actually help an amp sound more "open". This happens because as the bias shifts the gain of the power tubes decreases. This in turn prevents the power tube plates from saturating as easily. However too much bias excursion leads to what is referred to as "blocking distortion" which can make an amp sound farty and generally unpleasant. Blocking distortion occurs when the bias shifts so much that the tubes are basically shut off for a period of time. If the capacitor charges up rapidly but bleeds off slowly, combined with lots of excursion, this leads to blocking distortion. There are three associated parameters in the Axe-Fx II that allow you to alter the bias excursion behavior: Bias Excursion, Excursion Time and Recovery Time. Bias Excursion controls the amount of bias excursion. The higher the value the more the bias shifts when the virtual power tubes are overdriven. Excursion Time controls how rapidly the coupling capacitor charges when the virtual power tube grids are conducting. Recovery Time adjusts how quickly the excess charge bleeds off when the virtual grids are not conducting. Preamp tubes also exhibit bias excursion and too much of it can cause blocking distortion. Like power tube bias excursion, though, a little bit can help. The trick is getting the right amount." [https://forum.fractalaudio.com/threads/bias-excursion.99698/post-1195688]
</blockquote>

<blockquote>
(about blocking distortion) "Old Fenders are particularly prone to this. Reduce Bias Excursion to reduce at the expense of accuracy." [http://forum.fractalaudio.com/threads/is-there-something-wrong-does-this-sound-normal-odd-distortion.138302/#post-1640723]
</blockquote>

<blockquote>
"Blocking distortion occurs in older designs due to grid conduction. The grid gets forward biased which causes a net offset to develop on the coupling capacitor which, in turn, shifts the bias point. Modern designs incorporate various means of mitigating this (grid stoppers, for example). Some bias excursion is desirable though as without it the distortion can be "sterile". [http://forum.fractalaudio.com/threads/is-there-something-wrong-does-this-sound-normal-odd-distortion.138302/#post-1640780]
</blockquote>

<blockquote>
"Blocking distortion can be reduced by decreasing the Bias Excursion in the preamp." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-00-beta-3.148907/page-4#post-1764615]
</blockquote>

From the "Cygnus" amp modeling release notes:

<blockquote>
"The power amp bias algorithm is changed and the bias control works differently now. As with a real amp as you turn the bias down the gain also goes down. Typical values for bias are between 0.45 and 0.5 for fixed bias amps and 1.0 for cathode biased."
</blockquote>

Fractal Audio explains:

<blockquote>
"…Power tubes also exhibit bias excursion. Some bias excursion in the power amp can be desirable. If you design the power amp in such a fashion so as the tubes go into forward conduction as the plates are clipping this will effectively reduce the bias and lower the gain causing the amp to "open up". To much bias excursion can cause excessive blocking distortion AND crossover distortion…." [https://forum.fractalaudio.com/threads/rectifier-bias-excursion-time.179754/post-2194681]
</blockquote>

==POWER TUBE EXCURSION TIME + RECOVERY TIME==

From the Owners Manual:
<blockquote>
"These parameters are related to Pwr Tube Bias Excursion. They control how rapidly the coupling capacitor charges or bleeds off as the virtual power tube grids are conducting or not."
</blockquote>

==BIAS TREM FREQUENCY + DEPTH==

These are not supported on the AX8 and FM3.

From the Owners Manual:
<blockquote>
“These create true bias tremolo by varying the bias of the virtual power tubes. Bias Tremolo varies based on a multitude of variables including power amp settings, damping, bias parameters, and more. It is also “self-ducking” and decreases as you play harder. On some amp types, extreme bias depth can result in excessive crossover distortion. On other amps the amount of tremolo can vary greatly between loud and soft playing. All this, however, is part of the allure of bias tremolo as it results in a particularly organic sound. The sound of Bias Trem is available on the FM3 via the Tremolo/Pan block.”
</blockquote>

Bias Tremolo is a tremolo that’s built in the Amp block and is based on varying the bias of the virtual power tubes. The tremolo action is different from other types of tremolo and the amount of tremolo varies with a multitude of variables. Most importantly the tremolo is “self-ducking” and decreases at higher signal amplitudes. Bias tremolo is a somewhat crude tremolo circuit and its interaction with the power amp depends on many things including damping, bias, etc. On some amps high values of bias trem depth can result in excessive crossover distortion. On other amps the amount of tremolo can vary greatly between loud and soft playing. All this, however, is part of the allure of bias tremolo as it results in a particularly “organic” sound. Control of the bias tremolo is afforded by the Trem Freq and Trem Depth parameters. A modifier can be attached to Trem Depth to facilitate engaging and disengaging the tremolo via footswitch or for other applications.

If power amp modeling is disabled, Bias Tremolo won't work.

Bias Tremolo is also available as a type in the [[Tremolo/Panner block]] (firmware Ares).

Fractal Audio explains:
<blockquote>
"If the power tubes are being overdriven the bias tremolo can add lots of crossover distortion." [http://forum.fractalaudio.com/threads/info-on-the-new-bias-tremolo-feature-in-the-amp-block.67767/#post-833753]
</blockquote>

<blockquote>
"Bias trem doesn't work well with all amp models. It depends on the model and this is precisely why bias trem wasn't offered on every amp ever made. It works best on amps that are biased hotter and that don't have much gain. Even a Deluxe Reverb doesn't work that well with bias trem because the power amp overdrives too easily. That is why an actual Deluxe Reverb uses an optical trem instead." [http://forum.fractalaudio.com/threads/65-bassguy-sv-bass-citrus-bass-fas-bass-usa-bas-1-2-bias-trmolo-not-a-bug.87474/#post-1058577]
</blockquote>

<blockquote>
"Bias trem works by modulating the power tube grid bias. One of the side-effects is that the effect becomes less pronounced as you play harder which makes it basically "auto ducking". Also since it's modulating the bias it gives an almost Univibe like effect since the phase changes a bit too." [http://forum.fractalaudio.com/threads/patch-62-nuclear-tone-weird-tremolo-effect.122258/#post-1454602]
</blockquote>

<blockquote>
"Bias tremolo works by modulating the quiescent operating point of the power tubes. With a single-ended power amp with negative feedback the gain doesn't change much as you change the operating point, hence the tremolo effect is subtle. Bias tremolo works best on amps with little to no negative feedback." [http://forum.fractalaudio.com/threads/fw-q8-5f1-tweed-ec-4-scene-preset-vid-demo.126829/#post-1509387]
</blockquote>

<blockquote>
"Play harder and the effect is reduced. Just like a real bias trem because that's what it does, it modulates the power tube bias." [https://forum.fractalaudio.com/threads/can-the-origin-effects-revivaltrem-be-replicated.170499/post-2052388]
</blockquote>

About missing support for Bias Tremolo on the FM3:

<blockquote>
"Certain features were removed to allow the algorithms to run including the bias tremolo, input dynamics processing, and several other inauthentic enhancements." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-62#post-28446966]
</blockquote>

<blockquote>
"We removed all the superfluous stuff (bias tremolo, dynamic presence/depth, etc.) in order to get the core amp modeling to run on the slower processor." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-68#post-28450968]
</blockquote>

<blockquote>
"The Axe-Fx III contains various algorithms that allow you to enhance the amp modeling that don't exist on a real amp. I.e. dynamic presence/depth, input dynamic processing, etc. These were removed to allow the core amp modeling to run on the lower-powered processor." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-70#post-28454394]
</blockquote>

==CATHODE FOLLOWER COMPRESSION==

Also referred to as "Preamp Comp" or "CF Comp".

From the Owners Manual:
<blockquote>
"Sets the amount of compression in the virtual cathode follower. This interacts with other parameters listed in the Cathode Follower section of the Advanced page (Time, Ratio, etc.).”
</blockquote>

This sets the amount of cathode follower compression, and defaults to zero when the amp (model) doesn't have a cathode follower.

Fractal Audio explains:
<blockquote>
"Turning it up engages the cathode follower emulation. If the amp has no cathode follower the compression value will default to 0. This allows you to add a cathode follower to the amp, if desired." [https://forum.fractalaudio.com/threads/cathode-follower-compression.156241/post-1860500]
</blockquote>

<blockquote>
"The Compression knob in the Cathode Follower section controls the behavior of the preamp's cathode follower. Without getting too technical cathode followers are nonlinear compressors. They distort the signal and the distortion increases as more energy is input." [http://forum.fractalaudio.com/threads/tips-on-getting-rid-of-that-hifi-sound-1st-look-at-3.140533/#post-1665472]
</blockquote>

<blockquote>
"All the Fender models except the 59 Bassman and 5F8 Tweed don't have cathode followers." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-00-beta-3.148907/page-3#post-1764588 souce]
</blockquote>

==CATHODE FOLLOWER HARMONICS==

From the Owners Manual:
<blockquote>
"Simulates harmonics that occur naturally inside an amp as tubes interact. Higher values increase the interaction between virtual tubes, yielding “softer” distortion."
</blockquote>

==CATHODE FOLLOWER GRID CLIPPING==

From the Owners Manual:
<blockquote>
"Adjusts grid clipping in the cathode follower. Lower values reflect the softer response of classic British and American tubes like Mullard, Sylvania and RCA. Higher values simulate the response of modern Chinese and Russian tubes with more abrupt clipping."
</blockquote>

<blockquote>
(firmware Ares 5) “Grid Clipping” parameter has been added which allows the user to adjust the grid clipping in the cathode follower. The default value reflects the “softer” response of classic British and American tubes like Mullard, Sylvania and RCA. Higher values simulate the response of modern Chinese and Russian tubes with more abrupt clipping."
</blockquote>

Fractal Audio explains:
<blockquote>
"I personally like the Grid Clipping set low because it has the NOS tube vibe. High values remind me of JJ's and Chinese tubes which I'm not a particularly big fan." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-00-beta-3.148907/page-9#post-1764941]
</blockquote>

=Power Supply=

==SUPPLY SAG==

From the Owners Manual:
<blockquote>
"This controls virtual power amp dynamics. Higher settings simulate higher power supply impedance, and thus greater tube plate voltage “droop,” for a more compressed feel. This control interacts with the Master and will have little effect if the power amp is not being “pushed hard”. As Master is increased, the power amp draws more current from its power supply and the Supply Sag control will have more effect."
</blockquote>

<blockquote>"Sag is also dependent on Master Volume. The higher the MV, the more sag." [https://forum.fractalaudio.com/threads/can’t-nail-the-robben-ford-sound-and-i-know-exactly-why-help.199726/#post-2488659]</blockquote>

<blockquote>
(Quantum 2.0) "The power supply sag is now incredibly realistic and far superior to the "expander/compressor" techniques used in other products. Learning to adjust the pertinent parameters can make a good tone great. Supply Sag is the most fundamental of the power supply controls. It controls the virtual resistance of the AC input. In a real tube amp the supply sags due to a combination of power transformer resistance and rectifier resistance. Increasing Supply Sag increases this resistance and vice-versa. The higher the resistance the more the supply sags and the more bouncy and spongey the amp will feel. I like to increase Supply Sag a bit and reduce gain. You can monitor the virtual supply on the hardware by selecting the Supply Sag parameter. The gain reduction meter will display the supply voltage in dB relative to idle." [http://forum.fractalaudio.com/threads/quantum-2-00-tips-part-1.110275]
</blockquote>

<blockquote>
(Quantum 2.0) "For convenience the virtual power supply voltage (B+) can now be monitored on the PWR DYN tab of the amp block. When the Supply Sag control is selected the gain reduction meter will display the supply voltage in dB relative to the idle voltage."
</blockquote>

Sagging softens (squishes) the pick attack, coupled with a swelling rise in volume after the initial drop of the note.

High values of Sag along with low B+ Time Constant values can cause “ghost notes” when the supply type is AC (as in a real amp). Lower B+ Time Constant values will make the amp feel “faster” but too low can cause ghost notes.

Fractal Audio explains:
<blockquote>
"Ghost notes are intermodulation distortion between the power supply ripple and the audio. There are several ways to reduce it:
# Change the supply to DC. This will completely eliminate it as there will be no supply ripple.
# Reduce the supply sag. This will reduce the amount of ripple but also reduce the power amp compression due to supply sag.
# Increase the B+ time constant. This will also reduce the amount of ripple but slow the response of the supply." [https://forum.fractalaudio.com/threads/how-to-eliminate-ghost-notes.152478/post-1814089]
</blockquote>

<blockquote>
"Ghost notes are intermodulation products between the power supply and the note being played. Plexis often demonstrate this due to their fast power supplies (which yields more ripple). They're not harmonically related to the note being played. Some people find them undesirable, others find they add "complexity". Usually most audible on the G string in the middle of the fretboard. Many products do not accurately reproduce them or reproduce them at all." [https://www.thegearpage.net/board/index.php?threads/apartment-situation-kemper-or-fm3.2207095/post-31576395]
</blockquote>

<blockquote>
"Supply Sag models the power supply resistance. This includes the power transformer, rectifier and any other resistances before the filter caps. The higher the resistance, the more the supply droops when current is pulled from it by the power tubes. The more the supply droops, the spongier the feel." [http://forum.fractalaudio.com/threads/im-addicted-to-supply-sag.56648/#post-711961]
</blockquote>

In pre-Cygnus firmware, turning Supply Sag to zero disabled the power amp modeling in the Amp block in the preset. Cygnus firmware has a dedicated switch for this.

If the Power Amp Modeling switch is turned off, Master works as a simple volume, and Depth and Presence are deactivated.

Fractal Audio explains:
<blockquote>
"If you shut the power amp modeling off from the Global menu it is not exactly the same as turning it off in the Amp block. This is because the virtual power amp always runs. So if you shut the power amp modeling off from the Global menu the supply will still sag resulting in a more compressed response. If the Master is set high the sag can be quite pronounced." [http://forum.fractalaudio.com/threads/power-amp-sim-on-off-vs-sag-on-off-with-real-power-amp-behaviour-of-presence-control.121178/#post-1442553]
</blockquote>

<blockquote>(Cygnus) "With power amp modeling off the Presence control does nothing." [https://forum.fractalaudio.com/threads/modeling-questions.199009/post-2481687]</blockquote>

You use Supply Sag to simulate different rectifier types.

Fractal Audio explains:
<blockquote>
"Reduce to simulate solid-state, increase to simulate tube." [http://forum.fractalaudio.com/threads/rectifier-solidstate-vs-tube.102553/#post-1228660]
</blockquote>

Also read Aiken's White Paper '[http://www.aikenamps.com/index.php/what-is-sag What is "Sag"?]' for more information.

==B+ TIME CONSTANT==

From the Owners Manual:
<blockquote>
"This interacts with the Supply Sag control because it makes the virtual power supply response slower or faster. When the supply is fast the amp will sag rapidly accentuating the pick attack and compressing after. Most guitar players like this, but setting it too fast will cause excessive AC ripple and ghost notes. For convenience the virtual power supply voltage (B+) is shown as a meter on this page when the Supply Sag control is selected. (The meter shows dB, relative to the idle voltage.)"
</blockquote>

Fractal Audio explains:
<blockquote>
"B+ Time Constant is the time constant associated with the Supply Sag parameter. The power tubes draw current from the supply. The supply has a finite resistance. As the power tubes draw more current the supply voltage droops. The rate of change of the droop and recovery is dictated by the supply capacitance. The product of the resistance and capacitance is the time constant. It's typically around 10 ms. You can vary this using the B+ Time Constant parameter. It is not a simply compression though. As the supply sags, the headroom is reduced but many other things happen. One thing that happens is that the screen voltage droops. The screen voltage is derived from the B+. However the screen has it's own dynamic response, which is often 2nd-order since there is often a filter choke. If you listen carefully to the models with a filter choke you can hear the screen voltage "bounce" when you hit a power chord. The damping of the screen filter is not exposed to the user. When the screen voltage droops, the power tube gain decreases. It effectively shifts the bias point. There is quiescent draw from the supply as well. As you increase the bias (Power Tube Bias) the quiescent draw increases which decreases available headroom. The Axe-Fx II does not model all this stuff with compressors, like other products do. It actually uses a differential equation for the supply and the current from the power tubes. It then solves the equation at each sample instant to find the supply voltage and screen voltage." [http://forum.fractalaudio.com/threads/b-time-constant.46615/#post-608766]
</blockquote>

<blockquote>
"The effect of lower B+ is equivalent to increasing Transformer Match. A lower B+ means the plates clip sooner which is the same as increasing the turns ratio on the transformer. This is assuming that you rebias since typically lower the B+ affects the bias." [http://forum.fractalaudio.com/threads/is-there-a-parameter-to-manipulate-b-voltage-video-inside.60172/#post-751161]
</blockquote>

<blockquote>
"The attack comes first as things compress. Then the supply bounces due to a much slower time constant. Compression time constants are in the neighborhood of a few ms, B+ time constants are typically 10-20 ms. You can adjust these on the Advanced page. Many amp designers like a "fast" power supply but if you lower the B+ time constant too much you get ghost notes." [https://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-1-00-public-beta.103735/post-1245408]
</blockquote>

<blockquote>
"The higher the value the stiffer the power supply. This will result in less compression from the power amp. "Most" guitar players prefer a value around 10ms as it it accentuates the attack without excessive ghosting. It seems as though you prefer less attack so raising the value will accomplish that. Another option is to change the supply type to DC. This will eliminate any ghosting and give you a more "ideal" response. Most modelers use a DC power supply model but I've found that an AC supply model is key to achieving that last few percent of realism. The supply ripple is a big part of why old amps sound the way they do. Most guitar players actually like a percussive attack so that's why about 10ms has become a de-facto standard." [http://forum.fractalaudio.com/threads/i-had-a-b-time-constant-epiphany.106309/#post-1271768]
</blockquote>

<blockquote>
"High values of Sag along with low B+ Time Constant values can cause “ghost notes” when the supply type is AC (as in a real amp). Lower B+ Time Constant values will make the amp feel “faster” but too low can cause ghost notes."
</blockquote>

<blockquote>
"For convenience the virtual power supply voltage (B+) can now be monitored on the PWR DYN tab of the amp block. When the Supply Sag control is selected the gain reduction meter will display the supply voltage in dB relative to the idle voltage."
</blockquote>

<blockquote>
"B+ Time Constant controls the capacitance of the virtual power supply. The more capacitance the "slower" the supply and vice-versa. Most guitar players like a fast supply but too fast will cause excessive AC ripple and create ghost notes (although I think a little ghost note is cool). When the supply is fast it will sag rapidly accentuating the pick attack and compressing after. This parameter works in conjunction with Supply Sag parameter. The time constant remains constant so if you increase Supply Sag the virtual capacitance decreases." [http://forum.fractalaudio.com/threads/quantum-2-00-tips-part-1.110275]
</blockquote>

<blockquote>
[http://forum.fractalaudio.com/threads/ghost-notes.126903 Cliff's Tech Note about ghost notes]:

"A phenomenon present in some vintage amps is an artifact known as "ghost notes". Ghost notes are the result of intermodulation distortion between the note being played and ripple on the power supply. The ripple is at 120 Hz because the AC voltage is full-wave rectified. So there are frequency components of 120 Hz and its harmonics in the power supply. These frequency components mix with the note being played and create new tones that are not harmonically related to the note being played. Since it is intermodulation distortion, tones are created at the sum and difference frequencies. For example, if you play a D at the seventh fret on the G string this is 294 Hz. The intermodulation will create new tones at 294 - 120 = 174 Hz and 294 + 120 = 414 Hz. The harmonics of the note being played also factor in. The aforementioned D will also produce tones at multiples of 294 Hz and these mix with the 120 Hz and its harmonics. The G string above the 5th fret is most prone to this because of the harmonic spectrum of those notes. The amount of ripple on the supply is a function of the supply impedance. More capacitance and less resistance will reduce the ripple. Conversely less capacitance and/or more resistance will increase the ripple. You can adjust these values in the Axe-Fx using the Supply Sag and B+ Time Constant parameters. Supply Sag adjusts the virtual resistance of the power supply. B+ Time Constant adjusts the resulting time constant of the supply resistance and capacitance, i.e. as you increase the sag the time constant stays constant (capacitance decreases). To counter this increase B+ Time Constant. Old 100W Plexis exhibit this the most of any amp I've seen due to the high resistance of the power supply transformer. Our reference 100W Plexi has so much power supply resistance that the power supply sags up to 120V! This along with only 50 uF of power supply capacitance leads to prominent ghost notes."
</blockquote>

<blockquote>
"Ghost notes are intermodulation distortion between the power supply ripple and the audio. There are several ways to reduce it:
# Change the supply to DC. This will completely eliminate it as there will be no supply ripple.
# Reduce the supply sag. This will reduce the amount of ripple but also reduce the power amp compression due to supply sag.
# Increase the B+ time constant. This will also reduce the amount of ripple but slow the response of the supply." [https://forum.fractalaudio.com/threads/how-to-eliminate-ghost-notes.152478/post-1814089]
</blockquote>

<blockquote>
"Ghost notes are intermodulation products between the power supply and the note being played. Plexis often demonstrate this due to their fast power supplies (which yields more ripple). They're not harmonically related to the note being played. Some people find them undesirable, others find they add "complexity". Usually most audible on the G string in the middle of the fretboard. Many products do not accurately reproduce them or reproduce them at all." [https://www.thegearpage.net/board/index.php?threads/apartment-situation-kemper-or-fm3.2207095/post-31576395]
</blockquote>

==POWER TYPE==

From the Owners Manual:
<blockquote>
"These select between AC and DC virtual power supply types. AC rectification and resulting supply ripple are modeled, and the line frequency is also selectable. Note that as with a real tube amp, the AC Supply can cause “ghost notes” when Supply Sag is low and B+ Time Constant is high. Lower B+ Time Constant values will make the amp feel “faster,” but too low can also cause ghost notes."
</blockquote>

<blockquote>
(Axe-Fx II) "Amp block power supply modeling now models AC rectification and resulting supply ripple (if Pwr Supply Type is set to ‘AC’). The power supply type can be selected between AC and DC with the Pwr Supply Type parameter. The line frequency can be selected with the AC Line Freq parameter. Note that high values of Sag along with low B+ Time Constant values can cause “ghost notes” when the supply type is AC (as in a real amp). Lower B+ Time Constant values will make the amp feel “faster” but too low can cause ghost notes."
</blockquote>

This switches between virtual AC (Alternating Current) and DC (Direct Current).

AC LINE FREQUENCY is not the same parameter as AC LINE FREQUENCY in the unit's [[Setup menu|Global Settings menu]].

Fractal Audio explains:
<blockquote>
[http://forum.fractalaudio.com/threads/ghost-notes.126903 Cliff's Tech Note about ghost notes]:

"A phenomenon present in some vintage amps is an artifact known as "ghost notes". Ghost notes are the result of intermodulation distortion between the note being played and ripple on the power supply. The ripple is at 120 Hz because the AC voltage is full-wave rectified. So there are frequency components of 120 Hz and its harmonics in the power supply. These frequency components mix with the note being played and create new tones that are not harmonically related to the note being played. Since it is intermodulation distortion, tones are created at the sum and difference frequencies. For example, if you play a D at the seventh fret on the G string this is 294 Hz. The intermodulation will create new tones at 294 - 120 = 174 Hz and 294 + 120 = 414 Hz. The harmonics of the note being played also factor in. The aforementioned D will also produce tones at multiples of 294 Hz and these mix with the 120 Hz and its harmonics. The G string above the 5th fret is most prone to this because of the harmonic spectrum of those notes. The amount of ripple on the supply is a function of the supply impedance. More capacitance and less resistance will reduce the ripple. Conversely less capacitance and/or more resistance will increase the ripple. You can adjust these values in the Axe-Fx using the Supply Sag and B+ Time Constant parameters. Supply Sag adjusts the virtual resistance of the power supply. B+ Time Constant adjusts the resulting time constant of the supply resistance and capacitance, i.e. as you increase the sag the time constant stays constant (capacitance decreases). To counter this increase B+ Time Constant. Old 100W Plexis exhibit this the most of any amp I've seen due to the high resistance of the power supply transformer. Our reference 100W Plexi has so much power supply resistance that the power supply sags up to 120V! This along with only 50 uF of power supply capacitance leads to prominent ghost notes."
</blockquote>

<blockquote>
"The most notable thing would be the ghost notes. There is also a slight difference in feel." [http://forum.fractalaudio.com/threads/ac-power-frequency.67073/#post-826893]
</blockquote>

<blockquote>
"Those old amps make ghost notes. My 100W Plexi has some ghost notes that are louder than the fundamental. The easiest way to eliminate them (if you don't like/want them) is to simply set the Supply Type to DC. However, IMO, the ghost notes are a large part of the character of these designs and removing them isn't desirable. Don't over-analyze it. Recognize that certain designs produce ghost notes and embrace it." [http://forum.fractalaudio.com/threads/can-someone-check-this-out-jtm-45.70962/#post-870070]
</blockquote>

<blockquote>
"100 watters are usually worse because they have lighter filtering (50 uF vs. 100 uF) and draw more dynamic current." [http://forum.fractalaudio.com/threads/ac-vs-dc-power-supply-parameter-try-it.104471/#post-1250025]
</blockquote>

<blockquote>
(about the frequency) "One of the reason amps in Europe sound different than US." [http://forum.fractalaudio.com/threads/whats-the-advantage-of-ac-power-supply-type-and-ghost-notes.130281/#post-1545025]
</blockquote>

<blockquote>
"(...) Another option is to change the supply type to DC. This will eliminate any ghosting and give you a more "ideal" response. Most modelers use a DC power supply model but I've found that an AC supply model is key to achieving that last few percent of realism. The supply ripple is a big part of why old amps sound the way they do. Most guitar players actually like a percussive attack so that's why about 10ms has become a de-facto standard." [http://forum.fractalaudio.com/threads/i-had-a-b-time-constant-epiphany.106309/#post-1271768]
</blockquote>

<blockquote>
"So I was testing the next beta and selected the AC-20. Was hearing a lot of ghost notes compared to the old algorithm (in the debug build I can select between algorithms with a hidden parameter) and figured that couldn't be right. Hooked up the real AC-20 and, sure enough, ghost notes galore at the same settings." (...) "If you don't want authentic ghost notes set the Supply Type to DC." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-0-public-beta.154714/post-1840850]
</blockquote>

<blockquote>
"Ghost notes are intermodulation distortion between the power supply ripple and the audio. There are several ways to reduce it:
# Change the supply to DC. This will completely eliminate it as there will be no supply ripple.
# Reduce the supply sag. This will reduce the amount of ripple but also reduce the power amp compression due to supply sag.
# Increase the B+ time constant. This will also reduce the amount of ripple but slow the response of the supply." [https://forum.fractalaudio.com/threads/how-to-eliminate-ghost-notes.152478/post-1814089]
</blockquote>

<blockquote>
"Ghost notes are intermodulation products between the power supply and the note being played. Plexis often demonstrate this due to their fast power supplies (which yields more ripple). They're not harmonically related to the note being played. Some people find them undesirable, others find they add "complexity". Usually most audible on the G string in the middle of the fretboard. Many products do not accurately reproduce them or reproduce them at all." [https://www.thegearpage.net/board/index.php?threads/apartment-situation-kemper-or-fm3.2207095/post-31576395]
</blockquote>

==AC LINE FREQUENCY==

See [[#POWER_TYPE| Power Type]] for more information.

==VARIAC==

From the Owners Manual:
<blockquote>
"This sets the relative AC line voltage into the amp simulation. Volume varies greatly when a Variac is used with a real amp, but the virtual variac compensates for this."
</blockquote>

A Variac is said to be required to achieve VH's "Brown" sound. Try it at 75% with a Plexi.

Fractal Audio explains:
<blockquote>
"The whole amp voltage is reduced." [http://forum.fractalaudio.com/threads/preamp-bias.110726/page-2#post-1712822]
</blockquote>

<blockquote>
"The Spongy/Bold switch (on a Mesa) is basically a Variac." [http://forum.fractalaudio.com/threads/rectifier-solidstate-vs-tube.102553/#post-1228691]
</blockquote>

<blockquote>
"It's impossible to compensate exactly. Some manual adjustment of the volume may still be required." [http://forum.fractalaudio.com/threads/volume-changes-with-variac-setting.109951/#post-1316615]
</blockquote>

==SCREEN FREQUENCY + SCREEN Q==

From the Owners Manual:
<blockquote>
"These set the resonant frequency of the virtual power tubes’ screen filter, and the Q of that filter."
</blockquote>

=Speaker=

The parameters on this page shape the virtual speaker impedance curve and the resulting resonances in the virtual power amp. Amp and speaker interaction affects tone by causing an increase in power amp response at certain frequencies. Note that setting Negative Feedback greater than “0” flattens the effect of the response curve.

==LOW FREQUENCY + LOW FREQUENCY RESONANCE==

From the Owners Manual:
<blockquote>
"Guitar loudspeakers have strong low-frequency resonance. This shifts up slightly when the speaker is mounted in an enclosure. This resonance causes an increase in the power amplifier response due to the finite output impedance of the power amp."
</blockquote>

The default LF and HF Resonance settings in an amp model are based on the selected Speaker Impedance Curve in the Amp block (firmware Ares 11 and later). Before that firmware version, they were based on a typical guitar cabinet for the amp type.

Setting the Speaker Impedance Curve to "Resistive Load" is identical to turning off LF Resonance and HF Resonance. [https://www.thegearpage.net/board/index.php?threads/axe-fx-iii-and-power-station-2.2136319/post-30299688]

Fractal Audio explains:
<blockquote>
"The speaker tab is not an EQ. It allows you to adjust the impedance that the virtual speaker presents to the virtual power tubes. In most cases the resulting EQ is quite different than the impedance curve since negative feedback flattens the response. If you turn the damping all the way down then the EQ will be close to the impedance curve (but still influenced by the transformer)." [http://forum.fractalaudio.com/threads/amp-speaker-tab-versus-amp-graphic-eq.47917/#post-623896]
</blockquote>

<blockquote>
(before firmware Ares 11) "The default LF Resonance is based on the cab most likely to be used with that amp. For example, if you select a Twin Reverb model it will use the resonance data from the Twin Reverb amp that we used as the reference (we measured all the cabs as well as shooting IRs). Your 1960A cab probably has its resonance around 80 Hz so ideally you would want to do exactly what you did. The ultimate solution would be to measure the LF resonance but that requires special test equipment. I've found that you can usually find it by ear though. As you adjust the LF resonance you'll hear the cabinet sympathize. There is no way around this at the moment as no modeler can measure the impedance of a guitar cabinet (despite any claims to the contrary). Note that this is not applicable when using FRFR and IRs." [http://forum.fractalaudio.com/threads/fw10-amps-into-real-cab-astounding.66965/#post-825662]
</blockquote>

<blockquote>
(before firmware Ares 11) "The default values in the amp block are based on the measured impedance of the most commonly used speaker for the selected amp. If it is a combo amp then the values are derived from the speaker that was in the cabinet. Most people who capture IRs are unable to also capture impedance data." [https://forum.fractalaudio.com/threads/something-cool-ive-been-working-on.75794/post-927165]
</blockquote>

<blockquote>
(before firmware Ares 11) "The biggest source of inaccuracy in our modeling is the fact that the speaker impedance is unknown. For each model we assume an impedance based on the speaker that is likely to be used with the amp. Even then impedance will vary from speaker-to-speaker. The difference between the assumed impedance and the actual impedance is small but audible. Tone Matching will correct this error. The amp controls will still behave the same and match up with the actual amp well." [http://forum.fractalaudio.com/threads/tone-matching.142664/#post-1688589]
</blockquote>

<blockquote>
"The resonant frequency goes up when mounted in a cabinet. It doesn't need to be spot-on. If you are within 10% you'll be fine. If you want to be anal about it you can use an impedance analyzer. This is what we use: Dayton Audio DATS Dayton Audio Test System 390-806." [http://forum.fractalaudio.com/threads/speaker-tab-settings-in-amp-block-g12k100.68009/#post-836372]
</blockquote>

<blockquote>
"Most guitar speakers are roughly the same when it comes to the high-frequency reactive behavior. The impedance increases starting around 1 kHz and then increases at 3-4 dB/octave. This is due to the voice coil inductance. A pure inductance would increase at 6 dB/oct. but there are eddy current losses that make the voice coil look "semi-inductive". The Axe-Fx II models this with a high-order lossy inductor model. The low-frequency response of guitar speakers, however, varies greatly between speakers of different makes and models. This low-frequency response is a sharp resonance typically in the range of 50-150 Hz. The magnitude of this resonance varies from several to 20 times the nominal impedance. The impedance of a speaker influences the response of a tube amp since a tube power amp is essentially a transconductance amplifier. It creates a current for an applied voltage. This current in turn creates a voltage across the speaker terminals that is dependent upon the impedance of the speaker. Therefore the power amp will resonate at the resonant frequency of the speaker. This causes certain notes to become emphasized as they excite the resonant frequency. Negative feedback around the power amp will reduce the amount of resonance but not all amps use negative feedback (i.e. Vox). The increased voltage amplitude at the resonant frequency also causes the power amp to clip sooner at the resonant frequency. Think of it this way: if the power tubes are swinging, say, 200 V at the midrange frequencies, they will swing X times more at the resonant frequency where X is the ratio of the resonant impedance to the nominal impedance. So if the resonant impedance is 10 times the nominal impedance the power tubes will want to swing 2000 volts. This is impossible so they will clip. For high-gain tones this can cause the tone to sound muddy or feel spongy. For lower gain tones this can thicken the tone and make it feel, well, more spongy. Cabinet/speaker IR data does not contain the impedance information. The only way to obtain impedance data is to measure the current vs. voltage vs. frequency (despite what modeler advertising literature would like you to think). The Axe-Fx uses default values of LF Resonant frequency and impedance for each amp model. For models based on combo amps these values are derived from measurements of the actual amp's speaker. For models based on amp heads the values are based on measurements of the cabinet most likely to be used with that head. You can adjust the frequency and impedance to suit your taste. Reducing the impedance (Low Res) will reduce the bass response and can give tighter bass. Raising the impedance will increase the bass response and can give a fuller sound. Altering the frequency (Low Freq) will change the frequencies at which the power amp resonates and tuning this to the key you are playing in can be an effective strategy, e.g. set it to 82 Hz if playing in E. Don't be afraid to try drastic settings. Try turning Low Res all the way to zero. Compensate by adding some bass with the Bass knob or the EQ section. As I mentioned earlier the LF Resonance will cause the power amp to clip earlier than it will when amplifying midrange frequencies. Turning down the Master Volume will increase the headroom in the power amp and reduce this clipping. Furthermore the Transformer Match also influences when the power amp clips. So there is a relationship between LF Res, MV and Transformer Match. Many manufacturers publish impedance data for their speakers. Eminence and Jensen and probably others publish detailed impedance data. You can look at the impedance plots and set the resonance parameters to match (roughly). The Low Res parameter is indicated from 0 to 10 and sets the resonance in dB from 0 to 24 dB (dB is a ratio of powers so it's not really the proper units for this but that's semantics). For example, the Jensen P12N has resonant frequency of about 100 Hz so you would set Low Freq to 100 Hz. The impedance at this frequency is about 40 ohms. To get the Low Res amount use the formula (20 * log10(Zr/Rdc)) / 2.4 where Zr is the impedance at the resonant frequency and Rdc is the DC resistance. For this speaker Low Res is then (20 * log10(40/6.2)) / 2.4 = 6.7. A power amp isn't perfect though. Winding resistance in the output transformer increases Rdc, typically by a couple ohms. Therefore our above example would become (20 * log10(40/8.2)) / 2.4 = 5.7. The exact value isn't overly critical though and all this is subtle nuances. The resonance Q is a bit more difficult to calculate. It is derived from the bandwidth at the points where the impedance "gain" is the square root of the resonance impedance gain. IOW, if the impedance is, say, 10 times the nominal impedance then the bandwidth is given by the frequencies where the response is 3.16 times the nominal impedance. For our example the resonance gain is 5 (40 / 8 = 5). So the bandwidth is the frequencies at which the impedance equals sqrt(5) * 8 = 18. From the graph this is approximately 75 Hz and 130 Hz. Q is defined as f0 / bw so our resulting Q is 100/60 = 1.67. Most speakers have a Q of around 2.0 or so. Again the exact value isn't overly critical and don't be afraid to try extreme settings (you can't break anything). Finally, just because real speakers behave like this doesn't mean we have to adhere to this behavior. Perhaps a better speaker has no resonance (Low and High Res are zero), or maybe the Q is a lot lower or higher. In our virtual world we can design a speaker that is impossible to construct in the physical universe. tl;dr version: Mess with Low Freq and Res if you want, or not." [https://forum.fractalaudio.com/threads/about-speaker-lf-resonance.78003]
</blockquote>

<blockquote>
"The speaker page is the impedance vs. frequency. For a guitar amp with no negative feedback the voltage frequency response of the power amp will very closely match this since the power amp is basically a current source (V = I * Z). There will a slight reduction in the peaks as the output impedance isn't infinite but it is very high and will therefore be very close." [http://forum.fractalaudio.com/threads/1-1-let-s-talk-a-b-testing-actual-amps-to-their-axe-fx-ii-counterparts.79701/page-4#post-970197]
</blockquote>

<blockquote>
"LF: in general the Q is between 2 and 2.5. The Hi Freq is usually between 1 and 1.5 kHz. Hi Freq sets the critical frequency (or corner frequency) of the inductive portion of the loudspeaker's response. The critical frequency is the frequency at which the reactive component of the impedance is equal to the resistive component. This is found by fc = R/(2*pi*L). For a typical speaker R is around 6 ohms and L is around 0.75 mH. Therefore fc = 1270. Jensens tend to have higher inductance so that would move this value down. Eminence speakers tend to have lower inductance so that would move this value up. Celestion does not publish their values so I used Eminence values when calculating the defaults. You'll notice the Marshally stuff has fc around 1500 which is consistent with a typical Eminence copy of a Greenback. => You cannot obtain speaker impedance via audio stimulus and microphone measurement. Impedance is defined as voltage divided by current so you need to measure the current vs. applied voltage across the frequency range of interest. I have the equipment to do it, and have measured many speakers, but the average person do esn't have the equipment nor the knowledge to use the data. The influence of speaker impedance is generally not that great. The exception are amps with no negative feedback. In these cases the speaker impedance has a much more pronounced effect on the overall response. These amps include Vox, Matchless and most other "Class-A" designs. As soon as you add negative feedback the response flattens considerably. However... Presence and Depth reduce negative feedback so if you dial significant amounts of those in then the speaker impedance becomes a factor again. All-in-all you only have to be in the ballpark. 1500 Hz is a good starting point for Hi Freq. Adjust up or down slightly by ear. I don't believe that 3000 Hz is accurate. I've never seen a speaker that would have the corner frequency that far out. => As I explained a few posts up I wouldn't set Hi Freq outside the range of 1.0 to 1.6 kHz. Vibroverb model is an exception (800 Hz) since it had a more voice coil inductance. => I call it critical frequency since it is similar to the critical or corner frequency of a filter. I had to come up with some way of setting the loudspeaker inductance relative to the resistance. Frequency seemed to make more sense. I thought about an inductance parameter but figured that would be too nebulous. At the default settings the impedance rise of the simulated voice coil matches very close with published data. I have overlaid the modeled impedance curve with published data and it is a very good fit. For example, take the JCM800 model. The graph on the SPKR page has a scale of +20 dB at the top. Look at the response at 2kHz. It's roughly 1/4 of full-scale which equates to 5 dB. If we look at the impedance curve for a typical 8-ohm speaker we see that the impedance at 2 kHz is roughly 13 ohms. For a 6.5 ohm voice coil (typical) this means that the voltage at the speaker is 6 dB higher at 2 kHz. Pretty darn close to what the graph is showing. While there is no high-frequency resonance in the speaker itself, a resonance IS formed due to the winding capacitance of the transformer. This capacitance resonates with the voice-coil inductance. => The negative feedback is set in the Advanced menu. The SPKR page only sets the impedance curve of the speaker/OT combo. The values chosen are prototypical for the speaker used with the modeled amp. You should not need to vary these parameters much IMO. I only ever vary Low Freq and High Freq. Whenever I'm matching an amp I adjust Low Freq to match the resonance of my reference cabinet. I occasionally vary Hi Freq to get more or less midrange bite." [https://forum.fractalaudio.com/threads/v6-firmware-time-to-release-the-monster-speaker-resonance-page.55045/page-18#post-704035]
</blockquote>

<blockquote>
"Negative feedback does not affect the speaker impedance. Speaker impedance is an independent variable. The default values are based on the speaker cabinet most commonly used with the amp. In the case of a combo it's the internal speaker. For heads it's the mating cabinet, if one. A typical speaker has a low-frequency resonance with some frequency, Q and magnitude. The Q is typically around 2, frequency around 100 and magnitude around 12 dB. These values are dependent upon the speaker construction and, to a lesser extent, the cabinet. The voice coil inductance causes the impedance to increase at high frequencies. Unlike a pure inductance which would increase at 6 dB/octave, voice coil inductance is semi-inductive and typically increases at 3-4 dB/octave. The "break" frequency is dependent upon the actual inductance and is adjustable. The Axe-Fx is unique in that it lets you adjust these values. Most products just use a fixed curve." [http://forum.fractalaudio.com/threads/the-speaker-page.108172/page-2#post-1295724]
</blockquote>

<blockquote>
"The voltage at the output of a tube amp is a function of the speaker's impedance curve. The impedance curve is set in the SPKR tab of the amp block. Real speakers respond to the VOLTAGE at their terminals, not the current. The amp block creates a virtual voltage which is a function of the amp model and the impedance curve. The cab block uses IRs which represent the measured sound from the speaker vs. an applied voltage at the speaker terminals. The aforementioned virtual voltage is sent to the cab block which then produces an audio signal by convolving the virtual voltage data with the IR. As I said in my previous post the IR is largely independent of it's impedance curve. The impedance curve can then be seen as just another tone and feel shaping tool. Bass too prominent? Turn down LF Resonance. Want more midrange? Lower HF Res Freq. The degree to which the impedance curve affects the output of the amp block is a function of the power tube type and the amount of negative feedback. The less negative feedback the more the impedance curve influences the output. Since Presence and Depth work by reducing negative feedback at high and low frequencies respectively, increasing them will also increase the influence of the impedance curve at those frequencies. The dynamic impedance of the power tubes also affects the output. A power triode, for example, has a much lower plate impedance than a tetrode or pentode and, therefore, the output will be mostly independent of the speaker impedance." [http://forum.fractalaudio.com/threads/the-speaker-page.108172/#post-1295117]
</blockquote>

<blockquote>
"You can simulate changing power tubes in the Axe-Fx by simply increasing or decreasing the LF and HF resonance values." [http://forum.fractalaudio.com/threads/why-power-tubes-sound-different.79962]
</blockquote>

<blockquote>
"The speaker resonance is NOT proportional to the master volume level in the real world. The speaker impedance curve does change under drive level (at the speaker terminals) and that is modeled but the amount of change is very small. The Axe-Fx III is extremely accurate in its modeling, especially the power amp modeling as that is where much of the magic happens. This has been proven time and time again in controlled studies. We compare the models to the amps at levels from barely audible to ear bleeding using measurement equipment as well as listening tests and blind A/B evaluations. In a loudspeaker the resonances do change a bit vs. applied voltage but the effect is subtle. The Axe-Fx III models this (it's the Speaker Compliance parameter). For all intents and purposes though it's pretty much a static network as the parameter shift only occurs at large excursion values which only occur at very low frequencies (excursion is the integral of applied voltage)." [https://forum.fractalaudio.com/threads/speaker-resonance-pa-equalization-tied-to-master-volume-level.155270]
</blockquote>

When using a solid-state power amp with a traditional guitar cab, finetuning LFR can get you better results.

Fractal Audio explains:
<blockquote>
"There are certain aspects that simply can't be modeled and require user intervention. For example, a speaker has a low-frequency resonance. A tube amp will create a higher output at that resonant frequency. The Axe-Fx has no way of knowing what that resonant frequency is and defaults to a value that is common for the speakers that are typically used with that amp. However, if you drive that speaker through a solid-state amp you won't excite the resonance unless you adjust the Speaker Resonant Frequency to match it." [http://forum.fractalaudio.com/threads/axe-fx-accuracy-issues.31759/page-2#post-449782]
</blockquote>

<blockquote>
"One way to find the SRF is to put a Filter block after the amp block. Set the type to Peaking, Q to 5 or so and Gain to 10 dB. Start with a Freq. of 50 Hz. Play some chugga-chugga and slowly adjust the Freq. until you hear and feel the cabinet resonate. Make a note of the frequency. Remove the filter block and set the amp block SRF to match. 4x12s typically have an SRF of between 80 and 120. Open back cabs are typically a bit lower." [http://forum.fractalaudio.com/threads/walkthrough-dialing-in-amps-on-the-axe-fx.31775/page-2#post-450458]
</blockquote>

<blockquote>
"This post is aimed at those who use a solid-state power amp into a conventional guitar cab. As is described in the post "About Speaker LF Resonance" a guitar cabinet has an impedance resonance in the low frequencies. This typically falls in the range of 50 to 100 Hz. A tube amp, being essentially a current source, will have a voltage output that follows the impedance curve. Speakers, being electromotive devices, respond to applied electromotive force (EMF) which we know as voltage. A solid-state power amp is a voltage amplifier and, hence, will not be influenced by the impedance of the speaker. When using a solid-state power amp into a conventional guitar cabinet the experience will be different if the simulated speaker in the Axe-Fx II is not adjusted to match the actual speaker. Whether or not this is important is up to the individual but I imagine a lot of the posts about "in-the-room using power amp and cab is not the same" are due to this. Unfortunately the Axe-Fx II cannot measure the speaker impedance characteristics as it is not directly connected to the speaker. No device can measure the speaker impedance without being directly connected to the speaker, despite what their marketing claims may infer (cough, ahem...), since impedance is, by definition, V/I and we cannot measure these unless connected to the speaker terminals. The only truly accurate way to set the simulated speaker is to measure the speaker being used with an impedance measuring device. These can be had relatively inexpensively in the form of the Woofer Tester 3 (from Dayton Audio IIRC). You can also make your own using a small value resistor (0.1 ohms or so) in series with you power amp and measure the voltage across the resistor. The next best method would be to estimate the impedance using published data from the speaker manufacturer. If the make and model are known the data may be available. Add approximately 10% to the published resonance frequency if the speaker is in a sealed box. The worst method, and the subject of some contention, is finding the resonance by "feel". No power amp has perfect damping. If you put a sine wave (use the Synth block) into the speaker you may be able to observe or feel the resonant frequency. The cone will have increased excursion at this frequency. Of course you may just be feeling the room resonance. I have used this technique successfully on several speakers but it takes practice. The main drawback is that the magnitude of the resonance is unknown. The Axe-Fx II's Low Res parameter is displayed in dimensionless units from 0 to 10. Each unit corresponds to 2.4 dB of impedance "gain". We define this as a gain since the our current source power amp will experience a voltage gain. This is relative to the DC resistance of the speaker. For example, if the speaker's resistance is 6 ohms and the impedance at resonance is 60 ohms then our impedance gain would be 20*log10(60/6) = 20 dB. Dividing by 2.4 gives a Low Res value of 8.3. Since a tube amp isn't a perfect current source these values should be reduced slightly. The exact value of the Q isn't too important. About 2.0 is a good starting point. Adjust up or down to taste. If you are anal more information is in the aforementioned post about deriving the value of Q. Once the simulated speaker is set correctly you may notice a difference in low-frequency behavior and pick attack." [https://forum.fractalaudio.com/threads/about-matching-your-cabinets-resonant-frequency.79816/]
</blockquote>

<blockquote>
(answering: "once I know what frequency to pick for my cab, and roughly which amount and Q to use, is it ok and expected to use the same settings for every amp model?"):

"Yes, keep the same settings for all models." [http://forum.fractalaudio.com/threads/clarification-of-lf-resonance-with-real-cab-speaker-tab.91139/#post-1097466]
</blockquote>

Firmware 22 and later for the Axe-Fx III enable automatic adjustment of the Speaker Impedance Curve in the Amp block when selecting a "dyna-cab" in the Cab block:

<blockquote>"The Amp block now features “Auto Dyna-Cab Impedance”. When set to ON the speaker impedance curve of the Amp block will follow the Cabinet Type in the first mixer slot of the associated Cabinet block. I.e., if the Cab Type in the first mixer slot of Cabinet 1 is, say, 4x12 5153 and the Mode is Dyna- Cab then Amp 1’s speaker impedance will automatically be set to 4x12 5153." </blockquote>

==HIGH FREQUENCY + HIGH FREQUENCY RESONANCE + SLOPE==

See [[#LOW_FREQUENCY_.2B_LOW_FREQUENCY_RESONANCE|Low Frequency Resonance]] (above).

From the Owners Manual:
<blockquote>
"A loudspeaker voice-coil presents an inductive load to the power amp at high frequencies. This inductive load, in conjunction with the output transformer capacitance, creates a high-frequency resonance at the specified frequency.""
</blockquote>

<blockquote>
"High Frequency Slope allows fine adjustment of the high-frequency impedance of the virtual voice coil (which affects the slope of the impedance curve). A speaker voice coil is “semi-inductive” due to eddy current losses in the motor. This presents an impedance to the power amp that is neither fully inductive nor fully resistive. The amount of resistive loss varies by brand and type. Reducing Slope simulates a speaker that is less inductive, increasing Slope simulates a speaker that is more inductive. Typical speakers range from 3.0 to 4.5 with the median being about 3.7. Lower values yield greater midrange while higher values are more scooped and sizzly."
</blockquote>

Fractal Audio explains:
<blockquote>
"The HF Resonance Frequency is the "corner frequency" of the voice coil inductance. As this inductance isn't a pure inductance due to eddy currents the calculation is a bit complex however it is roughly equal to: fc = R / (2 * PI * L), where R is the voice coil resistance and L is the inductance. A typical voice coil has R = 7 and L = 1 mH. This yields: fc = 7 / 6.28e-3 = 1100 Hz. Most voice coils are a bit lower inductance than this. The typical range for fc is 1200 - 1500 Hz." [https://forum.fractalaudio.com/threads/i-found-your-missing-high-end.155291/post-1848224]
</blockquote>

<blockquote>
"Most guitar speakers are roughly the same when it comes to the high-frequency reactive behavior. The impedance increases starting around 1 kHz and then increases at 3-4 dB/octave. This is due to the voice coil inductance. A pure inductance would increase at 6 dB/oct. but there are eddy current losses that make the voice coil look "semi-inductive". The Axe-Fx II models this with a high-order lossy inductor model. The low-frequency response of guitar speakers, however, varies greatly between speakers of different makes and models. This low-frequency response is a sharp resonance typically in the range of 50-150 Hz. The magnitude of this resonance varies from several to 20 times the nominal impedance. The impedance of a speaker influences the response of a tube amp since a tube power amp is essentially a transconductance amplifier. It creates a current for an applied voltage. This current in turn creates a voltage across the speaker terminals that is dependent upon the impedance of the speaker. Therefore the power amp will resonate at the resonant frequency of the speaker. This causes certain notes to become emphasized as they excite the resonant frequency. Negative feedback around the power amp will reduce the amount of resonance but not all amps use negative feedback (i.e. Vox). The increased voltage amplitude at the resonant frequency also causes the power amp to clip sooner at the resonant frequency. Think of it this way: if the power tubes are swinging, say, 200 V at the midrange frequencies, they will swing X times more at the resonant frequency where X is the ratio of the resonant impedance to the nominal impedance. So if the resonant impedance is 10 times the nominal impedance the power tubes will want to swing 2000 volts. This is impossible so they will clip. For high-gain tones this can cause the tone to sound muddy or feel spongy. For lower gain tones this can thicken the tone and make it feel, well, more spongy. Cabinet/speaker IR data does not contain the impedance information. The only way to obtain impedance data is to measure the current vs. voltage vs. frequency (despite what modeler advertising literature would like you to think). The Axe-Fx uses default values of LF Resonant frequency and impedance for each amp model. For models based on combo amps these values are derived from measurements of the actual amp's speaker. For models based on amp heads the values are based on measurements of the cabinet most likely to be used with that head. You can adjust the frequency and impedance to suit your taste. Reducing the impedance (Low Res) will reduce the bass response and can give tighter bass. Raising the impedance will increase the bass response and can give a fuller sound. Altering the frequency (Low Freq) will change the frequencies at which the power amp resonates and tuning this to the key you are playing in can be an effective strategy, e.g. set it to 82 Hz if playing in E. Don't be afraid to try drastic settings. Try turning Low Res all the way to zero. Compensate by adding some bass with the Bass knob or the EQ section. As I mentioned earlier the LF Resonance will cause the power amp to clip earlier than it will when amplifying midrange frequencies. Turning down the Master Volume will increase the headroom in the power amp and reduce this clipping. Furthermore the Transformer Match also influences when the power amp clips. So there is a relationship between LF Res, MV and Transformer Match. Many manufacturers publish impedance data for their speakers. Eminence and Jensen and probably others publish detailed impedance data. You can look at the impedance plots and set the resonance parameters to match (roughly). The Low Res parameter is indicated from 0 to 10 and sets the resonance in dB from 0 to 24 dB (dB is a ratio of powers so it's not really the proper units for this but that's semantics). For example, the Jensen P12N has resonant frequency of about 100 Hz so you would set Low Freq to 100 Hz. The impedance at this frequency is about 40 ohms. To get the Low Res amount use the formula (20 * log10(Zr/Rdc)) / 2.4 where Zr is the impedance at the resonant frequency and Rdc is the DC resistance. For this speaker Low Res is then (20 * log10(40/6.2)) / 2.4 = 6.7. A power amp isn't perfect though. Winding resistance in the output transformer increases Rdc, typically by a couple ohms. Therefore our above example would become (20 * log10(40/8.2)) / 2.4 = 5.7. The exact value isn't overly critical though and all this is subtle nuances. The resonance Q is a bit more difficult to calculate. It is derived from the bandwidth at the points where the impedance "gain" is the square root of the resonance impedance gain. IOW, if the impedance is, say, 10 times the nominal impedance then the bandwidth is given by the frequencies where the response is 3.16 times the nominal impedance. For our example the resonance gain is 5 (40 / 8 = 5). So the bandwidth is the frequencies at which the impedance equals sqrt(5) * 8 = 18. From the graph this is approximately 75 Hz and 130 Hz. Q is defined as f0 / bw so our resulting Q is 100/60 = 1.67. Most speakers have a Q of around 2.0 or so. Again the exact value isn't overly critical and don't be afraid to try extreme settings (you can't break anything). Finally, just because real speakers behave like this doesn't mean we have to adhere to this behavior. Perhaps a better speaker has no resonance (Low and High Res are zero), or maybe the Q is a lot lower or higher. In our virtual world we can design a speaker that is impossible to construct in the physical universe. tl;dr version: Mess with Low Freq and Res if you want, or not." [https://forum.fractalaudio.com/threads/about-speaker-lf-resonance.78003]
</blockquote>

<blockquote>
"LF: in general the Q is between 2 and 2.5. The Hi Freq is usually between 1 and 1.5 kHz. Hi Freq sets the critical frequency (or corner frequency) of the inductive portion of the loudspeaker's response. The critical frequency is the frequency at which the reactive component of the impedance is equal to the resistive component. This is found by fc = R/(2*pi*L). For a typical speaker R is around 6 ohms and L is around 0.75 mH. Therefore fc = 1270. Jensens tend to have higher inductance so that would move this value down. Eminence speakers tend to have lower inductance so that would move this value up. Celestion does not publish their values so I used Eminence values when calculating the defaults. You'll notice the Marshally stuff has fc around 1500 which is consistent with a typical Eminence copy of a Greenback. => You cannot obtain speaker impedance via audio stimulus and microphone measurement. Impedance is defined as voltage divided by current so you need to measure the current vs. applied voltage across the frequency range of interest. I have the equipment to do it, and have measured many speakers, but the average person do esn't have the equipment nor the knowledge to use the data. The influence of speaker impedance is generally not that great. The exception are amps with no negative feedback. In these cases the speaker impedance has a much more pronounced effect on the overall response. These amps include Vox, Matchless and most other "Class-A" designs. As soon as you add negative feedback the response flattens considerably. However... Presence and Depth reduce negative feedback so if you dial significant amounts of those in then the speaker impedance becomes a factor again. All-in-all you only have to be in the ballpark. 1500 Hz is a good starting point for Hi Freq. Adjust up or down slightly by ear. I don't believe that 3000 Hz is accurate. I've never seen a speaker that would have the corner frequency that far out. => As I explained a few posts up I wouldn't set Hi Freq outside the range of 1.0 to 1.6 kHz. Vibroverb model is an exception (800 Hz) since it had a more voice coil inductance. => I call it critical frequency since it is similar to the critical or corner frequency of a filter. I had to come up with some way of setting the loudspeaker inductance relative to the resistance. Frequency seemed to make more sense. I thought about an inductance parameter but figured that would be too nebulous. At the default settings the impedance rise of the simulated voice coil matches very close with published data. I have overlaid the modeled impedance curve with published data and it is a very good fit. For example, take the JCM800 model. The graph on the SPKR page has a scale of +20 dB at the top. Look at the response at 2kHz. It's roughly 1/4 of full-scale which equates to 5 dB. If we look at the impedance curve for a typical 8-ohm speaker we see that the impedance at 2 kHz is roughly 13 ohms. For a 6.5 ohm voice coil (typical) this means that the voltage at the speaker is 6 dB higher at 2 kHz. Pretty darn close to what the graph is showing. While there is no high-frequency resonance in the speaker itself, a resonance IS formed due to the winding capacitance of the transformer. This capacitance resonates with the voice-coil inductance. => The negative feedback is set in the Advanced menu. The SPKR page only sets the impedance curve of the speaker/OT combo. The values chosen are prototypical for the speaker used with the modeled amp. You should not need to vary these parameters much IMO. I only ever vary Low Freq and High Freq. Whenever I'm matching an amp I adjust Low Freq to match the resonance of my reference cabinet. I occasionally vary Hi Freq to get more or less midrange bite." [https://forum.fractalaudio.com/threads/v6-firmware-time-to-release-the-monster-speaker-resonance-page.55045/page-18#post-704035]
</blockquote>

<blockquote>
"In the SPKR page of the Amp block are various parameters. I've talked about low-frequency resonance in another post. In this post I will address high-frequency resonance. As with LF resonance the high output impedance of a tube power amp causes the frequency response to follow the impedance of the speaker. There are two primary components: LF resonance and a high-frequency boost. The HF boost is due to the inductance of the voice coil. At the frequency where the voice coil reactance is equal to its resistance the impedance will start to rise. If this were a "pure" inductance it would rise at 6 dB per octave. However eddy-current losses in the motor cause this inductance to be "semi-inductive" and the impedance typically rises between 3 and 4 dB per octave. Different brands and models of speakers behave differently. You can look at the spec sheet for a speaker to get an idea as to the behavior of the speaker. The formula for the break frequency is given by f = R / (2*pi*L). For example, if the voice coil inductance is 1 mH and the resistance is 7 ohms then the break frequency would be 7/(6.28*0.001) = 1.1 kHz. The Axe-Fx II allows you to adjust the virtual voice coil via the HI FREQ and HI RES parameters. The HI FREQ parameter sets the "break" frequency which is the frequency where the inductive reactance equals the voice coil resistance. For most speakers it is around 1000 Hz. It is lower for larger speakers and higher for smaller speakers usually. The HI RES parameter sets the rate at which the impedance increases. The default value of 5.83 is around 3.5 dB per octave. If you want a smoother sound you can increase HI FREQ and/or decrease HI RES. If you want more highs or "chime" you can decrease HI FREQ and/or increase HI RES. Experiment with different values to get a feel for the response. Note that the amount of feedback (Damping parameter) will influence the behavior of these controls. With no feedback (Damping = 0) the frequency response follows the impedance curve virtually 1-for-1. As Damping is increased the frequency response flattens and the impedance curve has less influence on the response. As with all things in the Axe-Fx, use your ears." [https://forum.fractalaudio.com/threads/about-hf-resonance.81121]
</blockquote>

<blockquote>
"HF Resonance is similar to the previous control but only changes the slope of the resonance. The default value is consistent with the typical “semi-inductance” of a speaker voice-coil. Varying this value will change the high-frequency load presented to the virtual power tubes."
</blockquote>

==XFORMER LOW + HIGH FREQUENCY (TRANSFORMER LF/HF)==

From the Owners Manual:
<blockquote>
"These set the output transformer bandwidth."
</blockquote>

<blockquote>
(firmware Cygnus 16.01) "The Transformer LF parameter effectively adjusts the transformer’s inductance. Increase this value to simulate a smaller transformer, decrease to simulate a larger transformer."
</blockquote>

Fractal Audio explains:
<blockquote>
"XFRMR LF sets the low frequency -3dB point of the output transformer. Most transformers actually have a very low -3dB point (contrary to internet wisdom) however their full-power -3dB point is significantly higher. The Xfrmr Drive control sets the full-power -3dB point." [http://forum.fractalaudio.com/threads/controlling-the-lows.96327/#post-1154831]
</blockquote>

Transformer is sometimes abbreviated to "XFRMR".

==SPEAKER IMPEDANCE CURVE==

From the Owners Manual:
<blockquote>
"Tucked away near the end of the advanced menu is this remarkable little parameter. It selects between 50+ high-order speaker impedance modeling curves. Changing the amp Type will load an appropriate curve automatically. The Cabinet Resonance parameter can be used to adjust the amount of cabinet resonance in the impedance curve, an effect made instantly more visible on the graph shown on the “Speaker” page of the amp block edit menu and in Axe-Edit III or FM3-Edit."
</blockquote>

<blockquote>
(firmware Ares 11) "Amp block now uses new high-order speaker impedance modeling. 52 speaker impedance models (and two LB-2 models) are included and can be selected using the Speaker Impedance Curve parameter (on the Advanced page). Selecting an amp model will load an appropriate default Speaker Impedance Curve for that amp model. The Cabinet Resonance parameter can be used to adjust the amount of cabinet resonance in the impedance curve."
</blockquote>

The Speaker Impedance Curve parameter is often abbreviated to SIC. It sets the desired impedance curve for the selected amp model. Together with the selected cab model (IR) in the Cab block, this parameter mainly affects "feel" and bass response.

You can choose from many provided curves. You can either choose a curve that authentically fits the selected cab model (IR), or another one that sounds and feels great.

Setting the Speaker Impedance Curve to "Resistive Load" is identical to turning off LF Resonance and HF Resonance. [https://www.thegearpage.net/board/index.php?threads/axe-fx-iii-and-power-station-2.2136319/post-30299688]

The parameter Cabinet Resonance on the Speaker page of the Amp block lets you set the desired amount of cabinet resonance in the curve (default: 100%).

Fractal Audio explains:

<blockquote>
"Firmware 11.0 introduces our new high-order speaker impedance modeling. We've curated the impedance data from nearly 50 cabinets. You'll now be able to select the impedance curve to use with an amp model (selecting an amp model loads the most appropriate curve for that model). Why is this important? When you look at speaker impedance curves they look pretty simple. However that data is obtained when the speaker is mounted on an infinite baffle. As soon as you mount the speaker in a cabinet that impedance data changes, sometimes quite radically. The modes of the cabinet introduce significant peaks and dips in the impedance due to the back EMF created. Some of the cabs we measured have deviations from the published curves by 4-5 dB or more. To understand why this happens the impedance of a speaker is dependent upon the acoustic load. In an infinite baffle the load is constant. Put the speaker in a box and the load is greater at some frequencies and lower at others because the sound waves bounce off the walls and constructively or destructively interfere with the motion of the speaker. For example, consider the sound emanating from the speaker and bouncing off the back wall of the cabinet. When the sound wave reaches the speaker it will either aid or oppose the motion of the speaker. If it aids the motion then the impedance will be lower and vice-versa." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-10-02.155004/post-1850592]
</blockquote>

<blockquote>
"The impedance has a nonlinear component but it is very small relative to the linear component. IOW the amplitude of the wave is proportional to speaker displacement so the impedance curve is relatively constant vs. applied voltage. The nonlinear effects occur as the voice coil moves out of the magnetic gap and this is already modeled." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-10-02.155004/post-1850628]
</blockquote>

<blockquote>
"A tube power amp is a transconductance amplifier, voltage in - current out. A speaker is a voltage transducer, voltage in - sound out. Since the power amp is driving current the voltage at the speaker is the current times the impedance of the speaker (Ohms law V = I*R). The voltage therefore is dependent upon the impedance. A solid-state power amp is a voltage amplifier, voltage in - voltage out. Since the power amp is driving voltage the voltage at the speaker is NOT dependent on the impedance of the speaker. When an IR is captured (correctly) it is done using a solid-state power amplifier so the effects of impedance do not influence the measurement. Some people try to use tube power amps to capture IRs. This is incorrect methodology. The Axe-Fx power amp simulation is a transconductance simulation. It uses a simulated speaker impedance to derive the output voltage that then drives the simulated cabinet (IR). Firmware 11.xx has 47 (and counting) speaker impedance curves that you can select that allow for different power amp transconductance responses. Moreover the impedance simulation is now a high-order network that simulates the perturbations in impedance due to cabinet resonance. If you are using a conventional guitar cab and solid-state power amp ideally you would want to know the impedance curve of the cabinet. This requires special test equipment although I'm working on a idea to use the outputs of the Axe-Fx directly along with a special cable to allow field measurements by users. At this time the impedance curve matching is a Matlab program though and requires some hand-tuning." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-11-00-public-beta.155500/post-1850920]
</blockquote>

<blockquote>"The graph shown is the resulting response of the SIC plus the response of the transformer." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-22-00-release.195047/page-22#post-2430996]</blockquote>

<blockquote>
"Choose an impedance curve that most closely matches the speaker you used." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-11-00-public-beta.155500/post-1850937]
</blockquote>

<blockquote>
"The Null curve simulates a purely resistive load. No real speaker exhibits this type of impedance curve. It's simply there for reference." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-11-00-public-beta.155500/post-1851632]
</blockquote>

<blockquote>
"The little spikes are due to reflections, both internal to the cabinet and external from the room. The sound bounces off things and when it arrives in phase or out of phase with the speaker it changes the impedance. Noise in the environment can also impact the measurement. Ideally the environment should be as quiet as possible." [https://forum.fractalaudio.com/threads/speaker-impedance-curve-measurements.155738/post-2148090]
</blockquote>

<blockquote>
"Air is very linear. The impedance curve changes, but not for those reasons. It changes because the amount of voice coil in the magnet gap changes as the speaker moves. When the speaker moves one way more windings are in the gap and vice-versa. This changes the effective voice coil inductance. Also, the low frequency resonance changes (slightly) as a function of displacement. This is due to the compliance of the suspension changing with displacement. Compliance also changes due to a change in Force Factor (B*l) which is a function of displacement. There are no nonlinear effects due to "chunking at higher volumes". The cab does not have "resistance". FWIW, the impedance curves in the Axe-Fx are not static. They are dynamic. You can vary the amount of impedance shift using the Speaker Compliance parameter." [https://forum.fractalaudio.com/threads/impedance-curves-are-my-new-go-to-for-tone-shaping.182195/post-2237264]
</blockquote>

<blockquote>"The response of a tube amp is dependent upon the speaker impedance. If you use a speaker with same impedance curve as the model then the response of the model will be very close to the real amp (component tolerances are still a factor). If your speaker's impedance curve is different then there will be audible differences. In the Amp block you can select different impedance curves. Switch through them and notice the difference in response, particularly in the bass. Our modeling is extremely accurate but matching a particular copy of an amp is limited to variables beyond our control like speaker impedance curve, component tolerances and design changes." [https://forum.fractalaudio.com/threads/fm3-firmware-version-6-01.191161/post-2375310]</blockquote>

<blockquote>"Amps with low amounts of negative feedback in the bass region are sensitive to the impedance curve. The 5153 is one of these amps due to its NFB circuit." [https://thegearforum.com/threads/evh-amp-vs-axe-fx-qc-and-tmp.3593/post-133163]</blockquote>

Leon Todd explains this feature in [https://www.youtube.com/watch?v=wEgO5kE6FkU this video].

The Amp block in presets prior to firmware Ares 11 also relied on an impedance curve. A parameter in the [[Global Settings menu]] of the Axe-Fx III, FM3 and FM9 lets you decide to keep using the old values or update the preset to the newer specs. Then, when loading such a preset, the device either automatically selects the most fitting speaker impedance curve (you need to save the preset to make it permanent), or sticks with the "pre-11" impedance/resonance curve.

From the Owners Manual:
<blockquote>
(firmware Ares 11) "Setting Global “Update Pre-11.x Presets Spkr Imp Upon Load" parameter to YES will automatically update the Speaker Impedance Curve for the Amp blocks upon preset recall to use an appropriate Speaker Impedance Curve for that amp model. Setting the parameter to NO will leave existing presets unaffected. NOTE: Setting this to YES will also cause the EDITED LED to light indicating the preset has been modified."
</blockquote>

Firmware 18 for the Axe-Fx III (the FM9 and FM3 followed) also add the Speaker Impedance Curve parameter to the [[Global Settings menu]]. When set to DEFAULT the speaker impedance curve used when selecting an amp model is the default curve for that amp model, otherwise it is the selected curve. NOTE: this does not affect existing presets. The selected curve is used only when selecting a new amp model.

Firmware 22 and later for the Axe-Fx III enable automatic adjustment of the Speaker Impedance Curve in the Amp block when selecting a "dyna-cab" in the Cab block:

<blockquote>"The Amp block now features “Auto Dyna-Cab Impedance”. When set to ON the speaker impedance curve of the Amp block will follow the Cabinet Type in the first mixer slot of the associated Cabinet block. I.e., if the Cab Type in the first mixer slot of Cabinet 1 is, say, 4x12 5153 and the Mode is Dyna- Cab then Amp 1’s speaker impedance will automatically be set to 4x12 5153." </blockquote>

<blockquote>"All Dyna-Cabs have corresponding impedance curves that were taken from the actual cabs." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-22-00-release.195047/post-2431116]</blockquote>

===Speaker Impedance Curves list===

The current speaker impedance curves in the Amp block are listed below. The details are based on available information about the amps and cabs in Fractal Audio's possession. The information may be wrong.

# '''1x8 Champlifier''' — Fender Champ combo with 8" speaker
# '''1x10 Metro Blues''' — MESA Subway Blues combo with 10" Eminence Black Shadow
# '''1x10 Princetone''' — 1959 5F2-A Fender Tweed Princeton combo with 10" speaker
# '''1x10 Princetone Rev''' — blackface Fender Princeton Reverb combo with 10" speaker
# '''1x10 Princetone SF''' — silverface Fender Princeton combo with 10" speaker
# '''1x12 AC-20 DLX''' — Morgan AC20 Deluxe combo with 12" G12M75
# '''1x12 AST BV25''' — Swart Atomic Space Tone with 12" Mojotone BV-25m
# '''1x12 Brit G12H55''' — 1x12 cabinet with 12" Celestion G12H, low (bass) resonance (55 Hz)
# '''1x12 Brit G12H75''' — 1x12 cabinet with 12" Celestion G12H, high resonance (75 Hz)
# '''1x12 Brit G12M''' — 1x12 cabinet with 12" Celestion G12M (this curve is associated with the 1x12 Div13 CJ11 DynaCab)
# '''1x12 Brit G12T''' — 1x12 cabinet with 12" Celestion G12T (this curve is associated with the 1x12 G12T-100 DynaCab))
# '''1x12 Car Ambler''' — Carr Rambler combo with 12" speaker, probably Eminence Elsinore
# '''1x12 Class-A 15W''' — hand-wired 1x12 Vox AC15 reissue combo with 12" Alnico Blue
# '''1x12 Deluxe Oxford''' — Fender Deluxe Reverb combo with 12" Oxford
# '''1x12 Deluxe Tweed''' — 1957 Fender Tweed Deluxe combo with 12" speaker
# '''1x12 Deluxe Verb''' — Fender Deluxe Reverb combo with 12" speaker
# '''1x12 Deluxe Verb RI''' — reissue Fender Deluxe Reverb combo with 12" speaker (possibly Jensen C12-K) (this curve is associated with the 1x12 Deluxe Verb DynaCab)
# '''1x12 Dirty Shirley EV12L''' — Friedman Dirty Shirley combo or cabinet with 12" EV-12L
# '''1x12 G12T-75''' — 1x12 cabinet with 12" Celestion G12T-75
# '''1x12 Hot Kitty''' — Bad Cat Hot Cat 30 combo with 12" custom Celestion V30
# '''1x12 Jr Blues''' — Fender Blues Junior with 12" speaker (Eminence or Jensen?)
# '''1x12 Tweed Alnico Blue''' — Fender Tweed Deluxe with 12" Celestion Alnico Blue
# '''1x12 Tweed C12Q''' — Fender Tweed Deluxe with 12" Jensen C12Q
# '''1x12 Tweed Emmi''' — Victoria 20112 Deluxe Tweed combo with 12" Eminence
# '''1x12 USA Ext EV12''' — MESA extension speaker cabinet with 12" EV-12L
# '''1x12 V30''' — 1x12 cabinet with 12" Celestion V30
# '''1x12 Vibrato Lux''' — Fender Vibrolux combo with 12" speaker
# '''1x15 Heart Key''' — Harte HyDrive bass cabinet with 15" HyDrive speaker
# '''1x15 Portabass''' — Ampeg Portaflex bass cabinet with 15" Eminence
# '''1x15 Vibrato Verb''' — blackface Fender Vibroverb combo with 15" JBL D130
# '''2x10 Heart Key''' — Harte bass combo with two 10" HyDrive paper/aluminum cone speakers
# '''2x10 Super''' — brownface Fender Super combo with two 10" speakers
# '''2x10 Vibrato Lux''' — Fender Vibrolux combo with two 10" speakers
# '''2x12 Band Commander SRO''' — Fender Bandmaster with two 12" EV-SRO speakers
# '''2x12 Bassbuster''' — Fender BassBreaker cabinet with two Fane F70 speakers picture]
# '''2x12 Bassguy''' — blackface Fender Bassman combo or cabinet with two 12" speakers
# '''2x12 Class-A 30W''' — hand-wired VOX AC30 with two 12" speakers
# '''2x12 Class-A 30W Silver''' — VOX AC30 with two 12" Alnico Silvers (this curve is associated with the 2x12 Class-A 30W DynaCab)
# '''2x12 Class-A Greenback''' — VOX AC30 with two 12" Celestion G12M greenbacks
# '''2x12 Dizzy RV''' — Diezel rear-loaded cabinet with two 12" speakers
# '''2x12 Double Verb''' — blackface Fender Twin Reverb combo with two 12" Jensens (this curve is associated with the 2x12 Double Verb DynaCab)
# '''2x12 Double Verb SF''' — silverface Fender Twin Reverb combo with two 12" Jensens
# '''2x12 Godzilla''' — York Audio's Zilla Fatboy cabinet with 12" V30 and Creamback H75 speakers
# '''2x12 Guy Tron Alnico Blue''' — Guytron cabinet with two 12" Alnico Blues
# '''2x12 Jazz 120''' — Roland JC-120 combo with two 12" Roland Alnico speakers
# '''2x12 Lead 80''' — cabinet with two 12" Classic Lead 80 speakers
# '''2x12 Match Chief''' — Matchless Chieftain combo with two 12" Celestion G12H75 speakers
# '''2x12 USA C90 Open Back — Mesa open back cabinet with two 12" C90 speakers
# '''2x12 Recto''' — compact MESA Rectifier cabinet with two 12" speakers
# '''2x12 Two Stone 1265''' — Two-Rock cabinet with two Celestion G12-65 speakers
# '''2x12 TX Star''' — MESA Lone Star 2x12 combo or cabinet with two 12" speakers (probably Celestion C90 aka Black Shadow)
# '''4x10 Bassguy''' — Fender Bassman cabinet with four 10" speakers
# '''4x10 Bassguy RI''' — reissue 1959 Fender 5F6-A narrow-panel Tweed Bassman cabinet with four 10" Jensen P10s
# '''4x10 Brit JM45''' — Marshall JTM-45 cabinet with four 10" speakers
# '''4x10 Super Verb''' — Fender Super Reverb cabinet with four 10" speakers
# '''4x10 SV Bass''' — SVT bass cabinet with four 10" SVT speakers
# '''4x12 1960BV''' — 1999 Marshall 1960bv cabinet with original Celestion Marshall G12 Vintage speaker (Marshall OEM V30)
# '''4x12 5153''' — EVH 5150-III cabinet with four 12" speakers (probably G12H or G12-EVH)
# '''4x12 Basketweave''' — Marshall basketweave cabinet with four 12" speakers
# '''4x12 Brit 800''' — Marshall JCM800 cabinet with four 12" speakers
# '''4x12 Brit AX''' — Marshall 1960AX angled cabinet with four 12" speakers
# '''4x12 Brit Greenback''' — '72 Marshall cabinet with four 12" Celestion G12M greenbacks
# '''4x12 Brit TV''' — tall vertical angled Marshall 1960 cabinet with four 12" speakers (probably Celestion G12M greenbacks) (this curve is associated with the 4x12 1960TV DynaCab)
# '''4x12 Citrus''' — Orange cabinet with four 12" Celestion V30s
# '''4x12 Euro''': Bogner Standard cabinet with four 12" Celestion V30s
# '''4x12 Friedman''' — Friedman cabinet with two 12" Celestion V30s and two 12" Celestion G12M greenbacks. "The Friedman cab has two Greenbacks and two V30s. The impedance curve is for the cabinet as a whole. The DynaCabs are for the individual speakers. Therefore the same impedance curve applies to both DynaCabs." [https://forum.fractalaudio.com/threads/dynacab-pack-limited-public-beta.198581/post-2470963]
# '''4x12 Hipower''' — Possibly a Harry Joyce-era HiWatt cab with four 12" Fane speakers [https://forum.fractalaudio.com/threads/free-hj-4x12-rca-cab-pack.156177]
# '''4x12 Hipower Lindsey B''' — Lindsey Buckingham's HiWatt cab with four 12" speakers
# '''4x12 Hipower Pete T''' — Pete Townsend's HiWatt cab with four 12" Fane speakers [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-20-02-public-beta-beta-1.185043/post-2281949]
# '''4x12 Lerxst Omega''' — Lerxst Omega cabinet with four 12" speakers (probably greenbacks)
# '''4x12 London Town Tall''' — London City cabinet with four 12" speakers
# '''4x12 PVH 6160''' — Peavey 5150 cabinet with four 12" Sheffield speakers
# '''4x12 Recto Large''' — Mesa Oversized Rectifier cabinet with four 12" speakers
# '''4x12 Recto Slant''' — Mesa "slanted" Rectifier cabinet with four 12" speakers
# '''4x12 Recto Small''' — Mesa small Rectifier cabinet with four 12" speakers
# '''4x12 Recto Straight''' — Mesa "straight" Rectifier cabinet with four 12" speakers
# '''4x12 Rumble''' — Dumble cabinet with two 12" EV-12L speakers and two 12" EV-12S speakers in a X-pattern
# '''4x12 Solo 100''' — Soldano cabinet with four 12" speakers
# '''4x12 USA Lead C90''' — '80s Mesa cabinet with four 12" C90 speakers
# '''4x12 USA Semi-Open''' — MESA open/closed cabinet with four 12" speakers
# '''Double Notes Loadbox''' — based on a Two-Notes Torpedo
# '''Load Box LB-2 UK''' — derived from Fractal Audio's Load Box LB-2, set to "UK" voicing (= 4x12 with greenbacks, 100 Hz resonant frequency)
# '''Load Box LB-2 US''' — derived from Fractal Audio's Load Box LB-2, set to "US" voicing (= 1x12 with a Jensen speaker, 70Hz resonant frequency)
# '''Oxbow Loadbox''' — based on a Universal Audio Ox
# '''Resistive Load''' — flat curve which disables the speaker impedance / resonance modeling. Use this when connecting the Fractal Audio modeler to a tube amp

==CABINET RESONANCE==

This was introduced in firmware Ares 11, and this is not available on Axe-Fx II and AX8.

From the Owners Manual:
<blockquote>
"This parameter interacts with Speaker Impedance Curve, located on the Advanced page. Changing Cabinet Resonance alters the amount of cabinet resonance in the impedance curve."
</blockquote>

This parameter defaults to 100%.

==SPEAKER DRIVE==

From the Owners Manual:
<blockquote>
"This simulates distortion and gentle compression caused by pushing a speaker too far. It interacts with the Master which determines how hard the actual power amp is pushing. Don’t overlook this when striving for “vintage” tones as it helps make edge-of-breakup tones sound like an old, well-played amp."
</blockquote>

Note that if you crank it, it will start to sound like a fuzz or a blown speaker.

<blockquote>
"The range of the speaker drive parameter is far greater than you would be able to push any real speaker before it self-destructed. If it doesn't sound good set that high, simply turn it down." [http://forum.fractalaudio.com/threads/weird-speaker-drive-in-5-07.48341/#post-632608]
</blockquote>

<blockquote>
"There are architectural reasons for Speaker Drive being in the Amp block." [http://forum.fractalaudio.com/threads/speaker-drive-vs-motor-drive.125541/#post-1494086]
</blockquote>

<blockquote>
"Speaker Drive models the magnetic compression (which is actually distortion) that occurs due to the nonlinear speaker excursion vs. applied voltage." [http://forum.fractalaudio.com/threads/speaker-drive-vs-motor-drive.125541/page-2#post-1494537]
</blockquote>

Default value is 1 (as of firmware 23). Keep it at zero when using a traditional guitar speaker cabinet.

<blockquote>"Changed default values of Speaker Drive and Speaker Thump to better align with measurements of typical speakers."</blockquote>

<blockquote>
(about using Speaker Drive with a traditional cab) "I would say no. Your guitar cab is already distorting so you would be adding more distortion on top. As always, though, let your ears decide." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-6-02-public-beta.122103/page-7#post-1454119]
</blockquote>

In response to: "Can you compare and contrast Compression, Compliance, and Drive? Do they capture independent factors or if one of these parameters is turned up high the others should be turned down or off?":

* '''Speaker Compression''' models the reduction in volume as the voice coil heats up.
* '''Speaker Drive''' models the distortion of the cone/motor.
* '''Speaker Compliance''' models parameter shift as the voice coil moves within the magnet. The Bl product is a function of voice coil displacement. Bl is the "force factor" and is the product of magnetic field (B) times length of the coil in the magnet gap (l). [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-14.163656/post-1962917]
* '''Speaker Thump''' models the dynamic nonlinear behavior of a guitar speaker (mostly subsonic).
* '''Speaker Breakup''' sets the type speaker of breakup.

[https://forum.fractalaudio.com/threads/table-amp-settings-depending-on-power-amp-and-speaker.185259 Click here for recommended settings for different kinds of amplification]

The Speaker Drive algorithm has been improved in firmware 20.00 for the Axe-Fx III:

<blockquote>
(Release Notes) "New Speaker Drive algorithm in Amp block. This new algorithm more accurately models the frequency dependent distortion of guitar loudspeakers. The default value (upon resetting the block) is 2.0 which gives roughly 1 dB of compression. Setting the value to 0.0 defeats the speaker drive modeling. Higher values give a smoother and more focused sound, rounding off the “sharp edges” and yielding greater compression."
</blockquote>

<blockquote>
"Speaker Drive is free of aliasing." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-20-00-public-beta-beta-4.184197/post-2267206]
</blockquote>

<blockquote>"If you are using a real guitar speaker you may want to turn these controls down/off. With an FRFR I would not recommend that as FRFR speakers are not designed to distort like guitar speakers do." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-20-01-public-beta-beta-2.184738/post-2276849]</blockquote>

About Speaker Drive and Speaker Thump:
<blockquote>"Excessive values of either parameter can "destroy" the virtual voice coil. Don't turn things up that high." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-20-01-public-beta-beta-2.184738/post-2276769]</blockquote>

<blockquote>"If you want "nonlinear IRs" you need to use something like Volterra kernels. I've experimented with this and, in fact, the Speaker Drive and Speaker Thump parameters essentially create higher order Volterra kernels based on various amp parameters." [https://forum.fractalaudio.com/threads/anyone-try-using-ua-ox-stomp-for-their-cabs.198601/post-2470708]</blockquote>

==SPEAKER THUMP==

Added in firmware 20.01 for the Axe-Fx III. Uses this with FRFR amplification at low volumes.

Release notes:

<blockquote>"Added Speaker Thump control to Amp block. Speaker Thump models the dynamic, nonlinear behavior of a guitar speaker. A value of 5.0 roughly corresponds to an amplifier running into a speaker rated at the same power as the amplifier, i.e., a 100W amplifier running into a 100W speaker. The reset value is a conservative 2.5 which represents, i.e., a 50W amp running into a 100W speaker. Note that the majority of the response is in the subsonic region and the effect is primarily tactile. Existing presets are not affected and the value will be zero."</blockquote>

<blockquote>"If you are using a real guitar speaker you may want to turn these controls down/off. With an FRFR I would not recommend that as FRFR speakers are not designed to distort like guitar speakers do." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-20-01-public-beta-beta-2.184738/post-2276849]</blockquote>

[https://forum.fractalaudio.com/threads/table-amp-settings-depending-on-power-amp-and-speaker.185259 Click here for recommended settings for different kinds of amplification]

<blockquote>"Speaker Thump was a revelation after analyzing the Volterra kernels of guitar speakers driven near their power limits. I can't really say much more than that without giving away proprietary information. For me it's a must when using FRFR. It evokes that feeling of standing in front of a cranked 4x12." [https://forum.fractalaudio.com/threads/speaker-drive-and-thump-appreciation-thread.185272/post-2287427]</blockquote>

<blockquote>"If it sounds good it is good. A real guitar cab will creates its own thump AT HIGH VOLUMES. If you are playing at low volumes you can use Speaker Thump to simulate the high volume behavior." [https://forum.fractalaudio.com/threads/speaker-drive-and-thump-appreciation-thread.185272/post-2287433]</blockquote>

In response to: "Can you compare and contrast Compression, Compliance, and Drive? Do they capture independent factors or if one of these parameters is turned up high the others should be turned down or off?"

* '''Speaker Compression''' models the reduction in volume as the voice coil heats up.
* '''Speaker Drive''' models the distortion of the cone/motor.
* '''Speaker Compliance''' models parameter shift as the voice coil moves within the magnet. The Bl product is a function of voice coil displacement. Bl is the "force factor" and is the product of magnetic field (B) times length of the coil in the magnet gap (l). [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-14.163656/post-1962917]
* '''Speaker Thump''' models the dynamic nonlinear behavior of a guitar speaker (mostly subsonic).
* '''Speaker Breakup''' sets the type speaker of breakup.

Default value is 1.25 (as of firmware 23).

<blockquote>"Changed default values of Speaker Drive and Speaker Thump to better align with measurements of typical speakers."</blockquote>

About turning up Speaker Drive or Speaker Thump too high:

<blockquote>"Excessive values of either parameter can "destroy" the virtual voice coil. Don't turn things up that high." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-20-01-public-beta-beta-2.184738/post-2276769]</blockquote>

<blockquote>"Thump is a nonlinear process and you've essentially pushed the speaker to the point that the voice coil is traveling well outside the magnet gap. Turn Thump down. With a real speaker and amp you would have destroyed the speaker." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-20-02-release.185294/post-2288339]</blockquote>

==SPEAKER BREAKUP==

Added in firmware 20 for the Axe-Fx III.

Sets the type of speaker breakup.

Values: Soft, Medium (default), Hard.

In response to: "Can you compare and contrast Compression, Compliance, and Drive? Do they capture independent factors or if one of these parameters is turned up high the others should be turned down or off?"

* '''Speaker Compression''' models the reduction in volume as the voice coil heats up.
* '''Speaker Drive''' models the distortion of the cone/motor.
* '''Speaker Compliance''' models parameter shift as the voice coil moves within the magnet. The Bl product is a function of voice coil displacement. Bl is the "force factor" and is the product of magnetic field (B) times length of the coil in the magnet gap (l). [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-14.163656/post-1962917]
* '''Speaker Thump''' models the dynamic nonlinear behavior of a guitar speaker (mostly subsonic).
* '''Speaker Breakup''' sets the type speaker of breakup.

==SPEAKER COMPRESSION==

This was introduced in the Ares firmware, and is not available on Axe-Fx II and AX8.

From the Owners Manual:
<blockquote>
"Aka the “chunka chunka” parameter. It models the interaction of the power amp with the power compression of a virtual speaker. Typical guitar speakers compress between 3 and 6 dB depending upon construction, age, volume, etc. The default value is conservative and yields about 3 dB of compression. Master, Presence, and Depth will interact considerably with Speaker Compression, with higher causing more compression. A gain reduction meter shows the amount of Speaker Compression when this parameter row is selected. Note that this parameter does not reset to its default value when changing the Amp Type."
</blockquote>

From the release notes:

<blockquote>
"New Speaker Dynamics modeling. The Speaker Dynamics control adjusts the amount of virtual voice coil heating. Higher values result in more heating and commensurately higher voice coil resistance. The Speaker Time Constant will be reset to 2 seconds for existing presets. A typical guitar speaker has a voice coil thermal time constant in the range of several seconds." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486]
</blockquote>

<blockquote>
(Quantum 9) "Removed the “Motor Drive” and “Transformer Grind” algorithms and associated parameters from the Amp block. These have been replaced by the new “Speaker Compression” algorithm. This algorithm models the interaction of the power amp with the power compression of the virtual speaker. The “Spkr Comp” parameter controls the amount of virtual speaker compression. This value defaults to 3.0 when the Amp block is reset. It does not get reset when changing the model. If using the Axe-Fx II with a tube power amp and conventional guitar cab you may want to reduce this value to 0.0. The gain reduction meter shows the amount of virtual power compression (select the Spkr Comp knob to monitor the gain reduction). Typical guitar speakers compress between 3 and 6 dB depending upon construction, age, volume, etc. The default value is conservative and yields about 3 dB of compression. Note that the Master Volume control will interact considerably with the Speaker Compression algorithm as will the Presence and Depth controls. Higher values of Master Volume will cause more virtual speaker compression. [https://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-9-00-beta.130981/]"
</blockquote>

<blockquote>
(Ares 12.14) "Improved Amp block Speaker Compression modeling. New algorithm is more accurate and sounds smoother with more “growl”. [https://wiki.fractalaudio.com/wiki/index.php?title=Amp_modeling_progress#Firmware_Ares_12.x]"
</blockquote>

The Speaker Compression parameter replaced former parameters Motor Drive and Transformer Grind in the Amp block.

Default value is 1. Set it to zero when using a tube power amp and traditional guitar cab.

Fractal Audio explains:
<blockquote>
"Yes, the low end "weight" is what I immediately noticed. I don't use a lot, 1-2 typically. Just enough to thicken things up a bit. It's far more natural than the old algorithm which was an exotic compressor." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486/post-2067313]
</blockquote>

<blockquote>
"I call this one the "clanka-chunka burning love" firmware." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-9-00-beta.130981/#post-1551410]
</blockquote>

<blockquote>
"Notice how the low end goes "chunka chunka" and the top end "clanks". Pick squeaks are also more prominent." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-9-00-beta.130981/page-2#post-1551443]
</blockquote>

<blockquote>
"What I love about Speaker Comp is how it brings out the "chirp" on the unwound strings. Listen to all those great classic Marshall guitar tones and there's that chirp." [http://forum.fractalaudio.com/threads/beta-9-test-with-the-usa-iic-brt-dp-stereo-bbd-and-oh-zilla-irs.131008/#post-1551968]
</blockquote>

<blockquote>
"To really get the effect of speaker compression try the Speaker Compression knob. This behaves similarly to the output compressor but also "feeds back" to the power amp. As the speaker compresses the power amp behavior changes." [http://forum.fractalaudio.com/threads/tips-on-getting-rid-of-that-hifi-sound-1st-look-at-3.140533/#post-1665472]
</blockquote>

<blockquote>
"The default used to be 2.0. I reduced it to 1.0 because I felt it was better to be conservative with the default value and let people increase it if desired. I'm considering increasing the default back to 2.0 (or higher)." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-14.163656/post-1962918]
</blockquote>

<blockquote>
"I find I'm dialing in between 2 and 4. Sometimes even higher." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-14.163656/post-1962380]
</blockquote>

<blockquote>
"If using a tube power amp into a traditional cab all should be zero. If using a solid-state amp into a traditional cab I would recommend Speaker Compression and Compliance not be zero." [http://forum.fractalaudio.com/threads/axe-fx-iii-firmware-2-00-public-beta-2.144615/page-2#post-1710669]
</blockquote>

In response to: "Can you compare and contrast Compression, Compliance, and Drive? Do they capture independent factors or if one of these parameters is turned up high the others should be turned down or off?"

* '''Speaker Compression''' models the reduction in volume as the voice coil heats up.
* '''Speaker Drive''' models the distortion of the cone/motor.
* '''Speaker Compliance''' models parameter shift as the voice coil moves within the magnet. The Bl product is a function of voice coil displacement. Bl is the "force factor" and is the product of magnetic field (B) times length of the coil in the magnet gap (l). [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-14.163656/post-1962917]
* '''Speaker Thump''' models the dynamic nonlinear behavior of a guitar speaker (mostly subsonic).
* '''Speaker Breakup''' sets the type speaker of breakup.

[https://forum.fractalaudio.com/threads/table-amp-settings-depending-on-power-amp-and-speaker.185259 Click here for recommended settings for different kinds of amplification]

==SPEAKER COMPLIANCE==

This was introduced in the Ares firmware, and is not available on Axe-Fx II and AX8.

From the Owners Manual:
<blockquote>
"This control changes the nonlinear behavior of the virtual speaker. Selecting a new amp model or resetting the block will set the value to 50% which is a typical value for guitar speakers."
</blockquote>

Default valve is 50%. Set it to zero when using a tube power amp and traditional guitar cab. No need to turn it down when using a solid-state power amp.

From the release notes:
<blockquote>
"Improved Amp block speaker dynamic parameter modeling. The new Speaker Compliance parameter controls the nonlinear behavior of the virtual speaker. Existing presets will load with this parameter at 0.0 and will be unchanged tonally from the previous firmware (IOW your presets will not be altered). Selecting a new amp model or resetting the block will set the value to 5.0 which is a typical value for guitar speakers."
</blockquote>

Fractal Audio explains:
<blockquote>
"If using a tube power amp into a traditional cab all should be zero. If using a solid-state amp into a traditional cab I would recommend Speaker Compression and Compliance not be zero." [http://forum.fractalaudio.com/threads/axe-fx-iii-firmware-2-00-public-beta-2.144615/page-2#post-1710669]
</blockquote>

<blockquote>
"The easy way to understand compliance is to think of a spring. In Physics 101 we're taught that F = kx but that's an ideal spring. A real spring is nonlinear. Eventually you get to a point where compressing or stretching the string you run out of travel and the force goes nonlinear. A speaker is the same way. The suspension is essentially a spring and the greater the displacement the greater the force trying to restore the cone to its rest position. The compliance parameter controls how stiff that suspension is." [http://forum.fractalaudio.com/threads/axe-fx-iii-firmware-2-00-public-beta-2.144615/page-6#post-1711452]
</blockquote>

<blockquote>
"In a loudspeaker the resonances do change a bit vs. applied voltage but the effect is subtle. The Axe-Fx III models this (it's the Speaker Compliance parameter). For all intents and purposes though it's pretty much a static network as the parameter shift only occurs at large excursion values which only occur at very low frequencies (excursion is the integral of applied voltage)." [https://forum.fractalaudio.com/threads/speaker-resonance-pa-equalization-tied-to-master-volume-level.155270/post-1848002]
</blockquote>

In response to: "Can you compare and contrast Compression, Compliance, and Drive? Do they capture independent factors or if one of these parameters is turned up high the others should be turned down or off?"

* '''Speaker Compression''' models the reduction in volume as the voice coil heats up.
* '''Speaker Drive''' models the distortion of the cone/motor.
* '''Speaker Compliance''' models parameter shift as the voice coil moves within the magnet. The Bl product is a function of voice coil displacement. Bl is the "force factor" and is the product of magnetic field (B) times length of the coil in the magnet gap (l). [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-14.163656/post-1962917]
* '''Speaker Thump''' models the dynamic nonlinear behavior of a guitar speaker (mostly subsonic).
* '''Speaker Breakup''' sets the type speaker of breakup.

[https://forum.fractalaudio.com/threads/table-amp-settings-depending-on-power-amp-and-speaker.185259 Click here for recommended settings for different kinds of amplification]

==SPEAKER TIME CONSTANT==

From the Owners Manual:
<blockquote>
"This adjusts the thermal time constant of the virtual voice coil, affecting the attack and release of virtual Speaker Compression. Lower values cause the voice coil to heat and cool faster and viceversa."
</blockquote>

If Speaker Comp is zero, Speaker Time Constant is not operational.

From the release notes:
<blockquote>
(Cygnus amp modeling) "The Speaker Time Constant will be reset to 2 seconds for existing presets. A typical guitar speaker has a voice coil thermal time constant in the range of several seconds." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486/post-2067182]
</blockquote>

Fractal Audio explains:
<blockquote>
"It adjusts the thermal time constant of the virtual voice coil. Lower values cause the voice coil to heat and cool faster and vice-versa." [http://forum.fractalaudio.com/threads/speaker-time-constant.131886/#post-1561227]
</blockquote>

<blockquote>
"If Speaker Comp is zero the time constant does nothing. Any perceived difference is perceptual bias." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-9-00-firmware-release.131649/page-18#post-1560328]
</blockquote>

<blockquote>
"Time constant is dependent on the physical construction of the speaker." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-9-01-beta.131857/page-7#post-1561333]
</blockquote>

Also read the notes about the (removed) [[#MOTOR_DRIVE|Motor Drive]] parameter.

==OUTPUT MODE==

This was added in the Ares 1.16 firmware and is not available on Axe-Fx II and AX8.

From the Owners Manual:
<blockquote>
"The default value, “FRFR”, is designed for use while using “Full Range/Flat Response” monitors, or while recording. The “Solid State Power Amp + Cab” (“SS PWR AMP + CAB”) mode is intended for use while using a solid-state power amp and conventional guitar cab. In this mode speaker compression modeling behaves differently, relying on the speaker for compression while still simulating the interaction with the power amp."</blockquote>

<blockquote>"The SS PA + Cab Mode is NOT intended for use with “current drive” power amps, i.e. tube power amps, Class-D current feedback amps, etc. This mode CAN be used, however, with FRFR monitors in high volume applications where the monitor’s speakers are compressing, thereby achieving a more dynamic response."
</blockquote>

<blockquote>"Most modern Class-D amps are voltage feedback as AFAIK." [https://forum.fractalaudio.com/threads/table-amp-settings-depending-on-power-amp-and-speaker.185259/post-2488087]</blockquote>

Non-Class-D solid-state amps include: Matrix GT.

Class-D power amps include: Seymour Duncan PowerStage, Dayton.

Ideally, the user would be allowed to set this parameter per output. This isn't possible because it's part of the Amp block processing.

Fractal Audio explains:
<blockquote>
"Not possible as the processing is done in the Amp block not the Output block." [https://forum.fractalaudio.com/threads/frfr-ss-poweramp-option-per-output-mode.163839/post-1964181]
</blockquote>

[https://forum.fractalaudio.com/threads/table-amp-settings-depending-on-power-amp-and-speaker.185259 Click here for recommended settings for different kinds of amplification]

==AUTO DYNACAB IMPEDANCE==

Firmware 22 for the Axe-Fx III:

<blockquote>
"The Amp block now features “Auto Dyna-Cab Impedance”. When set to ON the speaker impedance curve of the Amp block will follow the Cabinet Type in the first mixer slot of the associated Cabinet block. I.e., if the Cab Type in the first mixer slot of Cabinet 1 is, say, 4x12 5153 and the Mode is Dyna-Cab then Amp 1’s speaker impedance will automatically be set to 4x12 5153."
</blockquote>

[[Cab block#DynaCabs|Read more about DynaCab cabinet modeling]]

=Input EQ=

Pre-EQ or Input EQ refers to the use of EQ to shape the guitar's tone before the distortion stage.

This was added to the Amp block with the arrival of firmware Ares. These parameters adjust a powerful set of filters at the input of the Amp block, so its effect is heard before preamp distortion or a front-end tone stack.

[http://forum.fractalaudio.com/threads/the-power-of-pre-eq.80951 Cliff's Tech Note]:

<blockquote>
* "As outlined in the MIMIC white-paper the fundamental paradigm of distorted guitar tone is EQ -> Distortion -> EQ. For higher gain tones the post-EQ is typically the tone stack and the Presence and Depth controls, when available. Therefore the user has access to the post-EQ but no control over the pre-EQ. One notable exception to this rule is the Mesa Mark series of amplifiers where the tone stack is located before the distortion.
* I suppose the ultimate amplifier would be one with dedicated pre-EQ and post-EQ controls although I can imagine many guitar players with looks of bewilderment when presented with such an amp. Indeed I believe there was an amp years ago that had separate input and output graphic EQs. I'm thinking it was made by Seymour Duncan but it was a long time ago so I'm not really sure. I don't believe it was terribly successful.
* So as we delve into the realms of higher gain tones we are the mercy of the amp designer and his choice of pre-EQ. The standard practice is to cut the lows before the distortion stages. There are various approaches to this: small coupling caps, partially bypassed cathodes, etc. These are simple methods and given the relatively simple nature of tube amps all we can really expect. Other popular pre-EQ techniques are shelving filters, i.e. the Marshall 470K, 470pF network and networks which roll off highs.
* The pre-EQ, along with the post-EQ, shapes the tone when the amount of distortion is low. As the distortion increases the tone becomes more dependent upon the post-EQ. Anyone who has adjusted a Mesa Mark series amp will attest to the seeming ineffectiveness of the tone controls at higher gains. They will also attest to the affect the tone controls have on the feel.
* So... the pre-EQ is an important part of the overall tone equation. We guitarists tend to focus upon the post-EQ and put graphic or parametric EQs after the amp but we neglect the pre-EQ. Therefore it is worthwhile to experiment with pre-EQ. The simplest approach to start with is using a graphic EQ before the amp block. Note how boosting or cutting certain bands affects the tone and feel. Note how the effect changes as the gain is increased or decreased.
* One popular studio technique in the 80's was to put a parametric EQ before an amp and boost a narrow band of frequencies. This gives a slight mid-emphasis to the sound and can be useful in helping the guitars stand out in a mix. This technique seems to have been lost over the years. Years ago Micheal Sweet from Stryper showed me the frequencies he used and IIRC he boosted around 800 Hz about 6 dB. I don't remember the Q but I would start around 1.4. Incidentally the frequencies he were boosting are just about the same as the frequencies that are cut by the tone stack. So when playing softly the net result is a flatter EQ. As you play harder the input EQ becomes less effective and the tone becomes more scooped.
* Pre-EQ can make amps sound warmer, or tighten the bass. It can be used to increase brightness without becoming harsh. Pre-EQ is also very useful with amps on the verge of breakup or mildly overdriven. Experiment with boosting frequencies to give your leads a more vocal character or make them more unique."</blockquote>

The Filter trick below can be applied using the Input EQ:

<blockquote>"This was a common technique in the 80's when tracking. If you have an Axe-Fx or other modeler with EQ options you can try it yourself. Put an EQ or Filter block before the amp. A parametric is best. Set the type to Peaking, Frequency to 1 kHz and Q to around 1 and gain to around 6 dB to start. Experiment with the parameters." </blockquote>

[https://www.youtube.com/watch?v=u_O0Dz_OUBY| Cooper Carter's EQ tips]

==TYPE + FREQUENCY + Q + GAIN==

These parameters work together to define a powerful multi-mode filter that can be used for anything from a subtle bump to an extreme spike, or from gentle to extreme shelving.

==LOW CUT==

Same as Low Cut Freq on the Preamp page.

==HIGH CUT==

This shaves highs off the input signal.

This is not the same as [[#HIGH_CUT_FREQUENCY|High Cut Frequency]] on the Preamp page.

==DEFINITION==

From the Owners Manual:
<blockquote>
"This control is a basic “tilt EQ” which adds highs/cuts lows, or vice versa. It is located at the amp type’s input, so its effect is heard before preamp distortion or a front-end tone stack."
</blockquote>

The tilt point is at 1kHz.

Positive values increase the amount of upper overtone saturation whilst negative values reinforce lower harmonics.

The [[Filter block]] also provides a [https://wiki.fractalaudio.com/wiki/index.php?title=Filter_block#Tilt_EQ Tilt EQ] type.

=Output EQ=

==TYPE + LOCATION + OFF/ON==

The Amp block has its own graphic EQ.

The EQ type and location (POST or PRE) can be selected through the EQ TYPE and EQ LOCATION parameters.

From the Owners Manual:
<blockquote>
"These parameters determine the number of bands, location, and on/off status of a graphic equalizer built in to the amp block. EQ Type sets number of bands and Q behavior (you can also change this from the Output EQ page using the NAV UP/DOWN buttons.) EQ Location sets the position of the equalizer. The default value of “OUTPUT” places the EQ at the output of the virtual power amp. “PRE PA” places the EQ between the preamp and power amp. The “INPUT” setting moves the Post EQ in front of the preamp. The EQ On/Off switch can be used to disable the EQ, and this setting can be controlled by a modifier."
</blockquote>

From the release notes:
<blockquote>
(firmware 19 for Axe-Fx II) "Added EQ Location parameter to Amp block. The sets the position of the graphic EQ. The default value of “Post P.A.” places the EQ at the output of the power amp. “Pre P.A.” places the EQ between the preamp and power amp. The graphic EQ in the Amp block is fixed in position at the output of the power amp section."
</blockquote>

Fractal Audio explains:
<blockquote>
(about the GEQ in the JPIIC model) "It's not that the Graphic EQ isn't the same, the TAPERS are not the same. On the real amp the controls do virtually nothing until you get near the ends of the range. If you move a slider to, say, 3/4 of its range it does almost nothing. If you were to set the model's slider to the same position you would get significantly more boost. I didn't model the nonlinear slider behavior because IMO it's a design flaw. Graphic EQs should have a nice, linear-in-dB response. Otherwise the graphic EQ is very accurate. The frequency and Q behavior is spot-on." [https://forum.fractalaudio.com/threads/real-jp2c-vs-axe-fx-3-sim-comparison.168942/post-2029916]
</blockquote>

<blockquote>
"The graphic EQ sliders aren't accurate in terms of position but they ARE accurate in dB and response. If you've ever used Mark series graphic EQ you'd notice that the sliders do very little in the middle and then rapidly change as you get near the top/bottom. This sucks so the Axe-Fx uses proper linear-in-dB controls." [https://forum.fractalaudio.com/threads/buttons-functioning-as-on-amps.170531/post-2052762]
</blockquote>

<blockquote>
"The tapers in the Axe-Fx are linear-in-dB. In the real amp (Mesa Mark series) they are quite nonlinear. For example, if we assume the sliders in the real amp go from -12 to +12, and we set a slider to +6 the corresponding position on the Axe-Fx might be only +3 dB. [https://forum.fractalaudio.com/threads/accurate-low-end-in-mesa-boogie-mark-iic-mark-v-jp-2c.177844/post-2166068]"
</blockquote>

The possible locations are:
* '''OUTPUT''' (default): The EQ is at the output of the virtual power amp.
* '''PRE PA''': The EQ is between the preamp and power amp.
* '''INPUT''': This moves the Post EQ to the location of the Pre EQ, in front of the preamp.

Tip: press Enter to reset all sliders to 0 dB (AX8 and Axe-Fx II only). Change the EQ type by pressing up/down.

The EQ can be turned off and on, also remotely.

The types of EQ available are:
* '''8 Band Variable Q'''
* '''7 Band Variable Q'''
* '''5 Band (Mark)''': this emulates the response of the on-board EQ in the Mesa Boogie Mark series amplifiers. When selecting amp models based on Mesa amps the type automatically changes to 5-band.
* '''8 Band Constant Q'''
* '''7 Band Constant Q'''
* '''5 Band Constant Q'''
* '''5 Band Passive'''
* '''4 Band Passive'''
* '''3 Band Passive'''
* '''3 Band Console'''

The 5-band EQ is especially useful with models based on Mesa Boogie's Mark series.

See [[EQ]] for more information about the EQ types.

=Dynamics=

==INPUT DYNAMICS==

This is not supported on the FM3 and FM9.

From the Owners Manual:
<blockquote>
"Sets the strength of an input dynamics processor. When set below zero, the amp type compresses, resulting in a smoother, less dynamic sound. When set greater than zero, the amp expands, resulting in a punchier, crunchier and more dynamic sound. Note that extreme values can have undesirable side-effects such as pumping or clipping."
</blockquote>

Fractal Audio explains:
<blockquote>
"Dynamics works at the input to the block. Negative values compress the input, positive values expand." [http://forum.fractalaudio.com/threads/output-comp-love.96779/#post-1160978]
</blockquote>

<blockquote>
"The Dynamics knob in the Amp block does the same thing as the Dynamics mode of the compressors." [http://forum.fractalaudio.com/threads/comp-vs-multicomp.107343/#post-1284495]
</blockquote>

<blockquote>
"The Dynamics type in the Compressor block is the same thing with more control." [http://forum.fractalaudio.com/threads/anyone-use-input-dynamics.146093/#post-1727558]
</blockquote>

Here is more information about missing support for Input Dynamics on the FM3:

<blockquote>
"Certain features were removed to allow the algorithms to run including the bias tremolo, input dynamics processing, and several other inauthentic enhancements." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-62#post-28446966]
</blockquote>

<blockquote>
"We removed all the superfluous stuff (bias tremolo, dynamic presence/depth, etc.) in order to get the core amp modeling to run on the slower processor." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-68#post-28450968]
</blockquote>

<blockquote>
"The Axe-Fx III contains various algorithms that allow you to enhance the amp modeling that don't exist on a real amp. I.e. dynamic presence/depth, input dynamic processing, etc. These were removed to allow the core amp modeling to run on the lower-powered processor." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-70#post-28454394]
</blockquote>

==MASTER BIAS EXCURSION==

This was introduced in the "Cygnus" amp modeling firmware. It scales ALL the bias excursion parameters. The default value for the various bias excursions is usually 100% but there are some amps where a bias excursion may be 0%, depending on the topology.

Fractal Audio explains:
<blockquote>
"16.00 and after use a new bias excursion algorithm which is much more accurate but also generates greater amounts of bias excursion. You'll never get 15.01 to get that choked 5E3 Tweed sound whereas 16.00 and later replicate it very accurately. Bias excursion reduces clarity and string separation but it's necessary for a realistic sound. I've said it before but I guess I need to say it again, if you want that 15.01 sound simply turn down Master Bias Excursion. That's why the control was added. [https://forum.fractalaudio.com/threads/moving-backward.180041/post-2206432]"
</blockquote>

<blockquote>"The simplest way to remove fizz is turn down Master Bias Excursion." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317936]</blockquote>

==OUTPUT COMPRESSION + TYPE + THRESHOLD + CLARITY==

From the Owners Manual:
<blockquote>
"This controls the ratio of a compressor specifically tailored to reduce the output dynamic range of the amp block. A gain reduction meter shows the amount of compression when this parameter row is selected."
</blockquote>

From the release notes:
<blockquote>
(firmware Quantum 7.02) "Improved Amp block output compressor. New algorithm is more musical and reacts faster to transients. If you are using this in your presets it is recommended to audition your presets and readjust as necessary. The Gain Reduction meter now shows the total gain including the makeup gain." "Non-zero values increase CPU usage. "The effect of the compressor setting can be watched on the DYN page of the Amp block."
</blockquote>

It offers three types of compression or gain enhancement, at the output section of the Amp block.

;'''OUTPUT''' : This simply compresses the output, similar to a Compressor block that follows the Amp block. It controls the ratio of a compressor specifically tailored to reduce the output dynamic range of the amp block. A gain reduction meter shows the amount of compression. Setting this to a non-zero value will increase CPU usage. The Out Comp parameter controls the amount of compression (compression ratio). The user can adjust the compression threshold if desired. The bar graph at the bottom of the menu displays the amount of gain reduction. A modifier can be attached to Output Comp. Output Comp Clarity affects Output Comp. It adjusts the bass response of the input dynamics and can be used to add clarity to the bass.

Fractal Audio explains:
<blockquote>
"The Output Compressor is a simplified version of the Compressor block." [http://forum.fractalaudio.com/threads/tips-on-getting-rid-of-that-hifi-sound-1st-look-at-3.140533/#post-1665472]
</blockquote>

<blockquote>
(sonic difference between Output Comp in Amp block and Comp block after Amp) "No different other than lack of advanced controls. Attack, release, etc. are fixed." [http://forum.fractalaudio.com/threads/what-is-the-sonic-difference-between-output-comp-in-amp-block-and-comp-block-after-amp.125469/#post-1492987]
</blockquote>

<blockquote>
"The compressor tries to apply make-up gain but it can only guess at the amount." [http://forum.fractalaudio.com/threads/output-comp-strangeness.87485/#post-1058658]
</blockquote>

<blockquote>
"Output Comp is compression ratio. Ratio = 1 + 3 * comp/10. Attack and release are fixed. Threshold is adjustable in the advanced menu." [http://forum.fractalaudio.com/threads/ouput-comp-recommendations.87494/#post-1058766]
</blockquote>

;'''FEEDBACK''' : This compresses the block output (see above), AND also applies dynamics to the input of the Amp block. You will get more distortion as you play harder and less when you play softer or roll back the volume.

Fractal Audio explains:
<blockquote>
"If you set the Compressor Type to Feedback and turn up the Output Compression you will get more distortion as you play harder. So you can create an amp that cleans up more when you play lightly or roll of the volume." [http://forum.fractalaudio.com/threads/feedback-parameter-in-amp-block-output-compressor.101388/#post-1216109]
</blockquote>

<blockquote>
"Here's a little trick to enhance the "clean up with guitar volume knob" thing. In the Amp block go to the Dynamics page. Set the Compressor Type to Feedback. Turn up the Output Compression to taste. Notice that when you play harder the amp will distort more. Now you can use the Input Drive and/or Trim to reduce the input gain so that when you play softer or roll off the volume the amp will clean up. Real amps get this from power supply sag but this requires the power amp be driven hard which can get muddy. This trick allows you to get that same response without cranking the Master Volume." [http://forum.fractalaudio.com/threads/clean-to-mean-w-the-volume-knob.144394]
</blockquote>

<blockquote>
"The Axe-Fx III models are extremely accurate. The Kemper has it's own vibe which a lot of people like. It's characterized by lots of midrange compression. You can replicate this on the Axe-Fx by setting the Output Compression type in the Amp block to Feedback and dialing in ~6 dB of compression. Adjust to taste." [https://forum.fractalaudio.com/threads/axe-fx-iii-clean-amp-sounds-compared-to-kemper-cleans.151497/post-1804532]
</blockquote>

;'''GAIN ENHANCER''' : This simulates the acoustic reinforcement of a loud amp coupling into the guitar and enhancing the output signal. Introduced in firmware Ares 9.01, this is a very popular feature, especially when playing through studio monitors or headphones at not-so-loud volume levels.

Fractal Audio explains:
<blockquote>
"At gig volumes you probably don't need any Gain Enhancer. It's designed to simulate the acoustic reinforcement of playing loud. But there are no rules so try it." [https://forum.fractalaudio.com/threads/fw10-gain-enhancer-reflections.155195/post-1847051]
</blockquote>

<blockquote>
"Instead of reducing input gain you can increase the Compressor Threshold. (...) All it does is shift the curve. The compression ratio doesn't change so it's the same as lowering input gain." [https://forum.fractalaudio.com/threads/gain-enhancer-appreciation-thread.154697/post-1841088]
</blockquote>

<blockquote>
(York Audio) "Here’s a hot tip for the edge of breakup fans out there. Set the amp’s input drive to where it’s basically clean, then edge up the Gain Enhancer until it breaks up the way you want when you hit it hard. Playing hard gives you big juicy chords, and lighter pick attack cleans it up while still sounding full. You get more sustain than if you just set the input drive hotter." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841963]
</blockquote>

<blockquote>
"If it's a very clean tone you won't hear anything. It's designed to enhance the gain of medium to high gain sounds." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-15-00-public-beta-1.168197/post-2020299]
</blockquote>

<blockquote>
"This will accentuate pick attack. Lower the gain and use your picking technique to dynamically control the gain." [https://forum.fractalaudio.com/threads/what-are-some-amp-and-drive-modes-that-work-well-for-getting-a-lowest-possible-amount-of-gain-modern-metal-sound.168212/post-2020291]
</blockquote>

<blockquote>
"If I'm playing softly I like it. At louder volumes I don't use it. That is, btw, precisely the intent as it simulates the acoustic reinforcement of a guitar played near a loud amp." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2051698]
</blockquote>

<blockquote>
"The gain enhancer is an algorithm that attempts to recreate the effect of playing in front of an amp. What I did was measure the spectrum of a guitar and then compared that to the spectrum when played in front of an amp. The physical feedback into the guitar is marked. I don't remember the exact numbers but it was at least several dB in the midrange. So what happens when you play in front of an amp is that the sound waves hit the guitar and reinforce the tone. It's a positive feedback loop which effectively increases (enhances) the gain in the midrange. When playing through monitors at low volumes or headphones you lose all that so the gain enhancer can be used to simulate the feedback loop."
</blockquote>

For more information see the '[https://forum.fractalaudio.com/threads/the-modelers-dont-clean-up-with-the-volume-knob-myth.154557 The "Modelers Don't Clean Up with the Volume Knob" Myth]' Tech Note.

Other parameters are:

;'''Threshold''' : Threshold sets the threshold of Output Compression. A lower value causes compression to occur for quieter signals.

;'''Clarity''' : Clarity is used in conjunction with the other Output Compression parameters, this adjusts the bass response of the compressor and can be used to add clarity to the low end.

=Legacy parameters=

[[image:Rip.png|link=|100px]]

==CATHODE FOLLOWER TIME / RATIO==

This was removed in firmware Ares 5 and later.

Attack time of the compressor and the maximum amount of compression with lower values giving more compression.

==CHARACTER==

No longer available in firmware Ares and later. Firmware 20 and later for the Axe-Fx III introduced the Dynamic Distortion block.

Extremely powerful “inverse homomorphic filters”. When playing softly these dynamic filters have little effect on the sound. As the amount of distortion increases, the influence of these filters increases. The Character Frequency control sets the center frequency of the filters while the Character control sets how pronounced the effect is. For example, to darken the tone when playing harder, one might set the frequency to 10 kHz and the amount to -5. Setting the amount to +5 will make the tone brighter when playing hard. The amount defaults to zero whenever an amp type is selected. This control is similar to Dynamic Presence and Dynamic Depth but the frequency is adjustable.

<blockquote>"The "Character" parameters are two of the most powerful advanced parameters available but I bet almost no one uses them. My secret formula: Character Frequency: 3000 - 5000 Hz, adjust to taste, Character: -0.5 to -1.0, adjust to taste." [https://forum.fractalaudio.com/threads/my-secret-formula.85426/] </blockquote>

<blockquote>"It is highly dependent on the amount of gain. This formula is designed for an "80's" lead tone. I use on for my JCM800 preset because I find JCM800s get shrill as you turn the gain up. It also works well with the SLO 100 and Recto models. The Character parameters control an "inverse homomorphic filter" which is a term I coined to describe a type of homomorphic signal processing. This filter is distortion dependent. The more distortion there is the more pronounced the effect of the filter. It's analogous to contrast and edge detection in image processing. The processing is dependent on the dynamic range of the image." [http://forum.fractalaudio.com/threads/my-secret-formula.85426/page-2#post-1036134] </blockquote>

<blockquote>"Added a new mode to the “Character” controls in the Amp block. A Char Type of “Dynamic” engages an exciting new mode of tone control. This can be used to fatten or scoop the tone as a function of picking strength. For example, set the Type to Dynamic, Char Freq to 450.0, Char Q to 0.7 and Char Amt to 4.0. This will cause the tone to get fatter and thicker as you play hard but without getting honky when playing soft."</blockquote>

==MOTOR DRIVE==

Removed from the Amp block in firmware Quantum 9 and later.

Available as a Cab block parameter on the Axe-Fx II.

Models the effect of high power levels on the speaker.

<blockquote>(Quantum 7.0) "Improved Motor Drive algorithm. New algorithm more accurately models the compression of guitar loudspeakers by factoring in the reactive aspects of the compression. The Motor Drive simulation is available in both the Amp block and Cab block now. It is recommended to use the simulation in the Amp block when using an FRFR configuration as the Amp block simulation uses the speaker resonance information in the calculations whereas the Cabinet block uses fixed values. When using a conventional guitar cab, or a hybrid configuration with monitoring via a conventional guitar cab and speaker emulation to FOH, the Motor Drive in the Cabinet block can be used instead. The simulation in the Amp block also has the advantage of being independent of the block’s output Level control. Gain monitoring of the Motor Drive is available on the MIX page of the Cabinet Block and the PWR DYN page of the Amp block. In the case of the Amp block the monitoring is available when the Motor Drive parameter is selected. Note that typical guitar speakers have around 3-6 dB of compression when driven hard with American speakers being on the low end of that range and British speakers being on the high end. Some speakers can exhibit even more compression than this with compression amounts of 8 dB or more depending upon the magnetic materials used and the construction of the speaker motor. The thermal time constant of the virtual voice coil is adjustable using the “Motor Time Const” parameter. Typical guitar speakers are anywhere from 0.05 to 1.0 seconds depending upon the mass of the voice coil and the materials used."</blockquote>

<blockquote>"Set it to 4.5 and rip the knob off." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-8-00-public-beta.126728/page-10#post-1508219]</blockquote>

When using two UltraRes cabs in a preset, don't use Motor Drive with only one of them, because this will cause a hollow sound.

<blockquote>"Motor drive isn't EQ. It models efficiency reduction due to thermal effects." [https://forum.fractalaudio.com/threads/anyone-using-speaker-drive-or-motor-drive-since-about-6-0.60651/#post-757563] And: "What I have found is that thermal compression is somewhat noticeable and measurable. This is modeled by the Motor Drive parameter." [https://forum.fractalaudio.com/threads/question-for-the-v11-beta-testers.73859/page-3#post-904487]</blockquote>

<blockquote>"Motor Drive will cause compression if not set to zero (as it models driver compression). Otherwise the cab block is completely linear and will not cause any compression." [http://forum.fractalaudio.com/threads/pick-attack-issues-thread-deleted.62238/page-2#post-772637]</blockquote>

<blockquote>"Motor Drive simulates power compression due to voice coil heating." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-6-02-public-beta.122103/page-4#post-1452979]</blockquote>

<blockquote>"Guitar loudspeakers are intentionally designed to compress. FRFR speakers do compress a bit but not nearly to the extent that guitar speakers do." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-02-public-beta.125473/page-5#post-1493261]</blockquote>

<blockquote>"Makes edge-of-breakup tone stupid easy." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-02-public-beta.125473/page-6#post-1493298]</blockquote>

<blockquote>"Speaker Drive models the magnetic compression (which is actually distortion) that occurs due to the nonlinear speaker excursion vs. applied voltage. Motor Drive models the change in power transfer due to heating of the voice coil. When the voice coil heats up the speaker sensitivity decreases, in some cases quite dramatically." [http://forum.fractalaudio.com/threads/speaker-drive-vs-motor-drive.125541/page-2#post-1494537]</blockquote>

<blockquote>"The thermal time constant of a typical guitar speaker is about 0.52 seconds. Magnetic time constants are zero." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-02-public-beta.125473/page-13#post-1494250]</blockquote>

<blockquote>"So what I've done for the final release is put Motor Drive in BOTH the Amp block and the Cab block. If you're strictly FRFR then you can use the Amp block. If you are using a conventional guitar cab or a hybrid configuration (convention cab for monitoring and direct to FOH) then you can use the Cab block. Doing it in the Amp block also has the advantage that the speaker resonance information in the Amp block is used to calculate the frequency dependent heating whereas the Cab block uses a fixed set of data that is representative of a typical speaker. Finally I've made the time constant adjustable. I did some more calculations and measurements and found that a typical guitar speaker is actually lower than what I had previously calculated because thinner wire is used than I was assuming. Regardless you can now set the thermal time constant to get whatever response rate feels best. When using the Motor Drive in the Amp block it's before the output Level control so you don't have to worry about the behavior changing when you adjust the Level knob." [http://forum.fractalaudio.com/threads/speaker-drive-vs-motor-drive.125541/#post-1494518]</blockquote>

<blockquote>"The actual value for a particular speaker is all over the map. The time constant is proportional to the mass and the thermal resistance of the voice coil. Both these values can vary widely. 200 ms is based on a typical theta of 1 degree C/W and a mass of 10g." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-02-firmware-release.125625/page-10#post-1495722]</blockquote>

<blockquote>"The formula is tau = M * C * theta where M = mass, C = specific heat of the voice coil material (typically copper) and theta = thermal resistance between the voice coil and the magnet gap." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-02-firmware-release.125625/page-11#post-1496045]</blockquote>

==PI BIAS SHIFT==

No longer available in firmware Ares and later.

<blockquote>(Quantum 7.00) "New algorithm also includes bias shifting which results in more harmonic spectrum variation with input amplitude. This improves feel, “knock” and creates sweeter single note soloing. The new “PI Bias Shift” parameter controls the amount of phase inverter bias shift. Note that some real amps are “spitty” in nature due to PI bias shifting, i.e. Trainwrecks, and the new algorithm is designed to replicate that behavior accurately. If you find the behavior undesirable reduce the PI Bias Shift value as desired although this will reduce authenticity."</blockquote>

==PICK ATTACK==

No longer available in firmware Ares and later.

Controls a sophisticated dynamic range processor that operates on leading edge transients. Negative values reduce pick attack while positive values enhance it.

On the Axe-Fx III and FM3, turn down the various Bias Excursion parameters for a similar effect as decreasing Pick Attack. [https://forum.fractalaudio.com/threads/how-to-reduce-pick-attack.152058/post-1809849]

<blockquote>"It doesn't have any particular frequency. Pick attack is impulsive so, by definition, it contains all frequencies. The standard approach to reducing attack is to use dynamics processing. The Axe-Fx II has a Pick Attack parameter which can be used to reduce the attack but the AX-8 does not have this parameter. You can try using the Gate/Expander to soften the attack." [http://forum.fractalaudio.com/threads/how-to-eq-out-pick-attack.118497/#post-1410629]</blockquote>

==TRANSFORMER GRIND==

No longer available in firmware Quantum 9 and later.

<blockquote>(Quantum 3.0) "Improved Amp block output transformer modeling. New model more accurately simulates dynamic core losses and leakage inductance. The “Xfrmr Grind” knob controls the intensity of the effect. Higher values result in more high frequency response and a more “open” sound. Very high values can yield a raspy, spitty tone common in vintage and/or low wattage amps. Modern “big iron” amps tend to have low values. Note that the audibility is dependent upon how hard the virtual power amp is driven and is more noticeable as the MV is increased. Also note that the effect in real amps is highly dependent on the speaker. Some speaker/transformer combinations exhibit significant high frequency dynamic boost while other combinations yield almost none. As always use your ears as the final determinant. Note: The Transformer Grind parameter will be set to a default value and the Dynamic Presence parameter will be reset to 0.0 for any presets created with previous firmware."</blockquote>

<blockquote>"Transformer Grind is what you want to get that top-end sizzle. Dynamic Presence is one of my "Inverse Homomorphic" filters and only approximates the dynamic presence boost found in some amps. Transformer Grind is an authentic model of what actually happens in those amps." [http://forum.fractalaudio.com/threads/q3-01-to-2-04-conversion.114090/#post-1364689]</blockquote>

<blockquote>"Some amps interact with some speakers resulting in a dynamic high frequency boost. It creates an aggressive, biting distortion. It depends on the amp (the amp's output transformer in particular) and the behavior of the speaker as it deviates from it's rest position. You can simulate this using the Transformer Grind parameter." [http://forum.fractalaudio.com/threads/raw-amp-sounds-anyone-know-how-to-get-them.121460/page-2#post-1445818]</blockquote>

==CATHODE FOLLOWER TYPE==

No longer available in firmware Ares 5.00 and later.

Selects between “Authentic”, which accurately models the compression in a tube amp, and “Ideal” which is an idealized distorting compressor. The idealized type is more focused and has tighter bass whereas the authentic type is bolder and looser. High gain players may prefer the ideal type due to its tight character.

<blockquote>"The “Ideal” cathode follower type is no longer supported as it is incompatible and has been removed from the GUI."</blockquote>

==DYNAMIC DAMPING==

No longer available in firmware Ares 10.00 and later.

Also known as Dynamic Impedance. Controls the reduction in plate impedance as a function of grid voltage. Higher values result in a more focused and forward midrange.

<blockquote>(Axe-Fx II) "Improved power amp modeling via improved modeling of the plate impedance of the power tubes. This gives tighter bass (less flub) and warmer highs when the virtual power amp is heavily driven (higher Master Volume settings). This also improves the feel and dramatically increases the “3-dimensionality” of the tone. The plate characteristics are adjustable via the new Dynamic Damping parameter. This parameter defaults to the appropriate value when an amp model or power tube type is selected. The power tube type presets the Dynamic Damping parameter as well as several internal parameters."</blockquote>

==CATHODE FOLLOWER HARDNESS==

No longer available in firmware Ares 14.00 and later.

<blockquote>(Owners Manual) "For models that use cathode followers, this adjust the shape, warmth, smoothness and decay of cathode follower distortion."</blockquote>

<blockquote>"The displayed value is 7.5 but the internal value is 0.75." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-9-04-firmware-release.134473/#post-1589113]</blockquote>

<blockquote>"It varies with brand of tube. The mean is around 7.5. Lower settings are smoother, higher settings are more aggressive." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-9-04-firmware-release.134473/#post-1589136]</blockquote>

==DYNAMIC DEPTH and DYNAMIC PRESENCE==

Removed in "Cygnus" amp modeling firmware. Firmware 20 and later for the Axe-Fx III introduced the Dynamic Distortion block.

Dynamic Presence:

<blockquote>(Owners Manual) "This models output transformer leakage inductance, resulting in a brightening of the tone when the virtual power amp is pushed. When playing softly or at lower gains, the influence of this control is lessened. Note that this only affects the power amp modeling and is dependent on the degree of power amp overdrive. This control can also be set negative to cause the tone to darken when playing harder. This can help dial in the sweet spot of an amp model. As the Master is increased, an amp becomes more liquid, more compressed and easier to play. However, the highs may get overly compressed, causing the amp to sound too dark. Dynamic Presence allows you to get the desired power amp drive and feel without high frequency loss."</blockquote>

Another way to look at it: distortion-dependent treble filter.

Dynamic Depth:

<blockquote>(Owners Manual) "Analogous to Dynamic Presence, above. This increases low frequencies when the virtual amp is being pushed. While real amps don’t display this behavior, it is a cool tone-shaping tool."</blockquote>

<blockquote>(firmware 10) "Dynamic Depth: analogous to the Dynamic Presence control, this increases or decreases low frequencies when the virtual power amp is being pushed. While real amps don’t display this behavior, it is a valuable tone-shaping tool. Another way to look at it: a distortion-dependent bass filter." </blockquote>

The FM3 hasn't supported Dynamic Presence and Dynamic Depth from the start.

About missing support for Dynamic Depth on the FM3:

<blockquote>"Certain features were removed to allow the algorithms to run including the bias tremolo, input dynamics processing, and several other inauthentic enhancements." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-62#post-28446966]</blockquote>

<blockquote>"We removed all the superfluous stuff (bias tremolo, dynamic presence/depth, etc.) in order to get the core amp modeling to run on the slower processor." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-68#post-28450968]</blockquote>

<blockquote>"The Axe-Fx III contains various algorithms that allow you to enhance the amp modeling that don't exist on a real amp. I.e. dynamic presence/depth, input dynamic processing, etc. These were removed to allow the core amp modeling to run on the lower-powered processor." [https://www.thegearpage.net/board/index.php?threads/fractal-audios-new-fm3.2040861/page-70#post-28454394]</blockquote>

<blockquote>"Dynamic Depth is a non-physical tweak. It uses what I call "Inverse Homomorphic Processing". Anything other than zero is deviating from authentic. It's not wrong to use it but it will be less accurate." [https://forum.fractalaudio.com/threads/legacy-amp-models-consider-revisiting-full-honest-request-and-opinion.160349/post-1920107]</blockquote>

[[category:Axe-Fx2]]
[[category:Axe-Fx3]]
[[category:FM3]]
[[category:FM9]]
[[category:AX8]]
[[category:Sounds]]
[[category:All]]

Axe-Fx III firmware release notes

2023-12-02T11:20:39Z

James-F:

[[image:Icon-firmware.png|link=]]
__NOTOC__

=23.04=

Fixed wrong Negative Feedback value for Brit 800 2203 models.

Fixed Bright switch off by default on 5153 100W Stealth Blue model.

=23.03=

Improved CPU usage.

Added "Nobelium OVD-1” Drive model based on a Nobels ODR-1. The BC (Bass Cut) switch is modeled via the Bass Response control. Set the Bass Response to 1.0 to duplicate the response of the pedal with the Bass Cut switch engaged. Set Bass Response to 5.0 to duplicate response with BC switch disengaged.

Added Sunrise Splendor model based on a JHS Morning Glory.

Added Gauss Drive model based on a Mesa Flux Drive.

Added Brit 800 2203 models.

Renamed Brit 800 to Brit 800 2204 High.

Added Brit 800 2204 Low model.

Added 5153 100W Stealth amp models.

Added USA MKV Green amp model.

Changed default values of Speaker Drive and Speaker Thump to better align with measurements of typical speakers.

Added NFB Compensation switch in Amp block. This defaults to On. Turning it off disables the negative feedback volume compensation at the output of the Amp block.

Fixed LFO2 not working in Chorus block.

Fixed wrong Distortion pot taper in DS1 Distortion models.

Fixed wrong Gain pot taper in Angle Severe models.

Fixed wrong output pad in USA JP IIC+ Green model.

Fixed wrong default tonestack in 1959SLP and Plexi 100W 1970 models.

Fixed EQ graphs in some blocks not updating when resetting the channel.

Fixed Output Configuration being overridden by Copy parameter. I.e., if Output 2 Configuration is set to Copy L->R but Copy Output 1 is ON then the output would have the same configuration as Output 1 (e.g., Stereo).

Various other fixes and improvements.

=23.02=

Fixed Rotary block LFO stuck.

=23.01=

Improved CPU usage.

Fixed audio artifacts can occur when switching Reverb block channels if there are different types between channels, i.e., switching between a plate reverb and a room reverb.

Fixed LFO quantization generating wrong number of steps.

=23.00=

Improved Amp block triode algorithm.

Improved Spring Reverb algorithm:
* New algorithm is based on a digital waveguide with scattering nodes. This algorithm achieves accurate spring reproduction recreating the iconic “drip” and flutter of classic spring tanks.
* There are two internal Spring Reverb types. The type can be selected using the Tank Type parameter. This parameter defaults to the appropriate type based on the model.
* The first type has all the springs in parallel. This is used by the British Spring and Studio Spring models. This is equivalent to an Accutronics Type 8 reverb tank.
* The second type has a pair of springs in series in parallel with one or more pairs of springs in series. This is equivalent to an Accutronics Type 4 (four springs) or Type 9 (six springs).
* For the second Spring Reverb type the reflection off the junction between the coupled springs is controlled by the Scattering parameter. Vintage Accutronics reverb tanks exhibit more reflection off the junction than modern, Asian-made reverb tanks.
* The “Drip” parameter controls the dispersion of the springs.
* The various models have different tone controls.
* Several new models have been added. The Tube Spring model is based on a 6G15 Tube Reverb and has an authentic tone control. Studio Spring is a hypothetical spring reverb with six long springs in parallel.
* Note that the Modulation parameters have been removed as they are not compatible with the new algorithm.
* Existing presets using Spring Reverb types are reset to default values. Audition as necessary.

Improved Reverb block early reflections. As a result, the default values of Early Level and Late Level for the models have been updated. Existing presets are automatically updated to the new values. Audition as necessary. The Early and Late Level parameters have also been removed from the Basic page of the Reverb block.

Added “Pre-Delay Tap” parameter to Reverb block. This selects the input to the reverb engine. When set to OUTPUT the behavior is as before. When set to INPUT the initial delay is absent. This allows more natural “Echo-Verb” sounds. This is now the default for these types of models and existing presets are automatically updated.

New Plate Reverb algorithm. This new algorithm captures the dispersion (Star Wars™ Laser “pew, pew” sound) and unique stereo imaging of classic plate reverbs. Dispersion is adjustable via the Dispersion parameter. Typical plates are around 25-50%. Set to higher values to exaggerate the effect. Stereo imaging is adjustable via the Pickup Spacing parameter.

Updated many of the Reverb models. Existing presets are not affected. Reselecting the model will load the new default values.

Improved Tremolo block:
* The optical tremolo algorithm has been completely rewritten.
* There are now three types of optical tremolo: Optical Trem 1: This type is based on optical pedal tremolos where depth controls the intensity of the LED. Optical Trem 2: This type is based on optical pedal tremolos where depth controls a “mixer” pot. This type has more “throb” than Optical Trem 1. Neon Trem: This type is based on the optical tremolo in classic “Blackface” amps which used a neon bulb to illuminate the LDR.
* The Tremolo type has been renamed “VCA Trem” and is based on a voltage-controlled amplifier topology.
* An LFO waveform monitor has been added for appropriate types.

Improved Tape Delay algorithm. The LFO1 Target and LFO2 Target parameters have also been removed from the Modulation tab as they are not applicable.

Improved Tape Chorus algorithm. The Number Voices parameter has also been removed from the GUI as it is not applicable to this type.

Updated Controller LFOs. The “Astable Beta” parameter for the LFOs has been renamed “Shape” and now controls the shape of the LFO for all types except Square and Random.

Updated all JS410 Lead models based on a current production JVM410HJS. The Crunch models were tested and did not require updating.

Added JS410 Lead Green amp model.

Added "2x12 USA C90 Open Back" speaker impedance curve.

Added Pitch High Cut parameter to Reverb block. This can be used to darken/brighten the pitch-shifted component of the reverb.

Added Modifier capability to High Cut parameter in Delay block.

Added Smoothing parameter to Cabinet block in Dyna-Cab mode.

Improved channel switching speed. Amp and Cabinet block channel switching times, in particular, are much improved. This, in turn, improves preset and scene switching times.

Preset, scene and channel changes are now gapless, if desired. A global parameter (Setup->Global Settings->Gapless Changes) allow turning this feature on or off.

Fixed NaN could occur in Euro Uber model at certain combinations of Presence and Speaker Impedance.

Various other fixes and improvements.

=22.01=

Added Revv Gen Green amp models.

=22.00=

Version 22 Introduces Dyna-Cab™ cabinet modeling.

The Cabinet block now has two modes of operation: Legacy and Dyna-Cab. Legacy is the previous style of operation.

Dyna-Cab cabinet modeling allows freely positioning the microphone. We took an approach of quality-over-quantity:

* Dyna-Cab IRs are a full 2048 samples.
* Mic positions are sampled at a fine spatial resolution.
* Four mic choices are available: Condenser, Ribbon and two Dynamic types.
* All IRs are time-aligned with each other. They have been processed using a new algorithm that ensures alignment without destroying phase information. You can mix-and-match IRs from different cabs/mics and they'll always be perfectly aligned.

The Amp block now features “Auto Dyna-Cab Impedance”. When set to ON the speaker impedance curve of the Amp block will follow the Cabinet Type in the first mixer slot of the associated Cabinet block. I.e., if the Cab Type in the first mixer slot of Cabinet 1 is, say, 4x12 5153 and the Mode is Dyna-Cab then Amp 1’s speaker impedance will automatically be set to 4x12 5153. If both Amp and Cab blocks are in the grid then Amp 1 will follow Cab 1 and Amp 2 will follow Cab 2. If only Cab 1 is in the grid both Amp blocks will follow Cab 1.

Added “Treble Shift” control to Tone page of USA IIC+ models. This is an alias of the “Fat” control found on the Preamp page and performs the same function.

Added clip warning if Input 1 clips. This is indicated on the Mini-Tuner.

Added meters to Input page of I/O menu. Input 1 meter will turn red if clipping occurs.

Added Speaker Impedance Curves for “2x12 Class-A 30W Silver”, “2x10 Heart Key” and “4x12 1960BV”.

Added “4 Band JMPRE-1” type to Graphic EQ block. Note that the upper two bands of this type have more boost/cut range than the version in the Amp block.

Added “Revv Gen” amp models based on a Revv Generator 120. There are three models for each of the Purple and Red channels corresponding to the three levels of the “Aggression” switch.

Improved Amp block channel switching speed.

Fixed side-chain filters not working in Gate block.

Fixed a filter in the Wah block not being initialized.

Various other fixes and improvements.

=21.04=

Fixed Tuner not working if Offsets are on.

=21.03=

Improved dynamic speaker modeling in Amp block.

Reverted bypass speed of Drive block to fast.

Fixed channel changes on blocks with “Slow Bypass” are not smooth.

Fixed IR(s) not loading in Cabinet block when switching channels if previous channel had a slot Soloed.

Fixed presets with lots of modifiers (>20) and moderately high CPU usage can cause starvation of graphics thread.

Improved Tuner.

=21.02=

Added "59 Bassguy RI Jumped" amp model based on a ’59 Bassman LTD Reissue.

Added “JP IIC+ Shred” Input Boost type to Amp block. This replicates the “Shred” switch on the Mesa/Boogie JP2C.

Added “Bosom Boost” Drive model based on a Friedman Buxom Boost.

Added “OD-One Overdrive” Drive model based on a Boss OD-1.

Improved Compressor block:
* Improved Studio FF Compressor 1 type. New algorithm yields smoother release and “fatter” compression. This type is suitable for a wide range of uses now including bus and mastering. Type has been renamed Studio FF Compressor.
* Improved Optical Compressor types. New algorithm features improved ballistics and inherent soft knee for vintage optical compression sounds.
* Improved Dynamics Processor type. New algorithm also supports various detector types.
* Improved JFET Compressor type.
* Added Optical Sustainer type based on optocoupler-based pedal compressors.
* Added Analog Sustainer type. This is an upwards compressor using the same “analog” gain computer as the Analog Compressor type yielding a natural soft-knee response.
* Added JFET Sustainer type. This is based on a rare JFET-based pedal compressor where the JFET is in the op-amp’s feedback network.
* The range of the Release Time has been increased to 2ms to 2s.
* Added graph for Analog Compressor and Sustainer types.
* New Auto-Makeup Gain algorithms for most types provides better output level tracking vs. Threshold and Ratio. Note: As a result, the output level of the compressor block may be slightly different compared to previous firmware. Auditioning presets that use the Compressor block is recommended.
* Selectable Auto-Makeup Gain has been added to Optical, Tube and Analog Compressor types.
* Studio FF Compressor 2 has been renamed Studio FF Sustainer.
* Studio FB Compressor 1 has been renamed Studio FB Compressor and Studio FB Compressor 2 has been renamed Studio FB Sustainer.
* Types have been alphabetized.

Improved Gate block:
* Improved Downward Expander type. The “Hold Time” parameter has been removed as it is not compatible and no longer needed with the new algorithm. This type has been renamed “Classic Expander” as it based off classic analog downward expanders.
* Added “Modern Expander” type. This type uses a novel approach to the envelope detector resulting in improved ballistics compared to traditional analog expanders. A “Knee Type” parameter has been added which allows selecting between hard-knee expansion and varying degrees of soft-knee expansion.

Improved Noise Gate in Input block:
* Improved performance based on new algorithm developed for Gate block.
* A Mode selection has been added allowing the user to select between “Easy” and “Advanced”. In Easy mode the number of parameters is reduced simplifying the adjustment procedure for those who are unfamiliar with the finer details of gates/expanders for guitar noise reduction applications.

Changed bypass/engage speed for the following blocks: Drive, Filter, Graphic EQ, Parametric EQ, Tremolo and Wah. These blocks now bypass/engage with a gentle fade as rapid bypass/engage with these types of blocks can sound abrupt.

Updated PVH 6160 Block and PVH 6160+ models. New models have more accurate Gain knob response.

Reduced default Power Tube Grid Bias for PVH 6160 and Recto models as previous default was hotter than these amps are typically run due to the non-adjustable bias.

Improved Speaker Thump algorithm in Amp block.

Added “Oxbow Loadbox” and “Double Notes Loadbox” speaker impedance curves based on a Universal Audio Ox and Two Notes Torpedo, respectively.

Fixed Transformer and Vintage preamp types in Cabinet block not ported correctly during a previous firmware update. This manifested as the distortion not being frequency dependent.

Various other fixes and improvements.

=21.01=

Added “Paragon” type to Wah block based on a Tycobrahe Parapedal.

Fixed Hi Treble not working in Amp block.

=21.00=

New “Cygnus X-2” amp modeling:

Improved Amp block output transformer algorithm. New algorithm more accurately models B-H curve resulting in a clearer low end. New algorithm now also accounts for effect of speaker impedance on transformer response.

Improved power tube modeling. This yields better dynamics, improved low frequency accuracy and more accurate interaction with output transformer.

Improved cathode follower algorithm. Provides more accurate “cleanup” when volume is rolled off.

Improved triode algorithm more accurately models plate bypass capacitors.

Improved dynamic frequency response accuracy. This yields more “crunch” and less “fizz” with high gain tones, especially for detuned styles.

Various other improvements.

All amp models have been updated as a result of the aforementioned improvements.

The default values of various parameters have been updated. Existing presets are automatically updated to the new values upon load.

Improved Drive block modeling to more accurately model effects of op-amp finite open-loop gain and GBW product.

Added “Griddle Cake” Drive model based on a Crowther Hot Cake. The “XLF” switch on the pedal can be replicated by turning the Bass Response knob fully CW.

Added “Overdrive Volume” parameter to Dumble-type amp models (ODS-100, Two Stone, etc.). This is sometimes labeled “Ratio” or “Lead Master”. As the Master Volume on these amps often has a bright capacitor the Overdrive Volume control allows setting the Master Volume higher to counteract the bright cap and then lowering the power amp drive with the Volume.

Added “Plate Suppressor Diodes” parameter. This value is set automatically when the amp model is chosen but the user can override the default setting. Most amps do not have suppressor diodes but some do (e.g., Trainwreck Express). These diodes (also called “snubber” or “flyback” diodes) prevent undershoot on the power tube plates due to inductive kick and reduce upper harmonics thereby reducing “fizz”.

The Ideal amp controls have been updated.

Added Brit Studio 20 Amp model based on a Marshall SV20H.

Added Plexi 50W 6CA7 Jumped Amp model. This is simply the jumped version of the Plexi 50W 6CA7.

Added features to the IR Capture Utility. The manual will be updated with the relevant information.

Renamed USA Clean to USA Rhythm 1 to be more in line with actual amp.

Reduced CPU usage in some cases.

Changed tone stack tapers for Class-A 30W TB to vintage specs.

Fixed wrong capacitor value in USA JP IIC+ models when Presence Shift is off.

Fixed wrong coupling capacitor value in 1959SLP Treble, 1959SLP Jumped and 1987x Treble amp models.

Fixed wrong resistor value in tone stack of Solo 88 Rhythm and Lead models. Probably not audible though.

Fixed low frequency behavior of Recto2 models due to loss of precision.

Fixed wrong treble pot taper in CA3+ models.

Fixed wrong capacitor value in Friedman HBE V1 Fat model.

Fixed wrong resistor value in AC-20 12AX7 models.

Fixed wrong Depth knob taper in Archean models.

Fixed wrong capacitor value and wrong feedback network connection in Energyball model.

Fixed missing resistor in Euro Uber tone stack.

Fixed High Mid control in Drive block set to minimum when importing presets created prior to 19.01.

Various other fixes and improvements.

=20.04=

More Drive block improvements. Drive block now incorporates the “Chase Transform Technique” for converting analog networks to equivalent digital filters. This improves accuracy in the high frequency region.

Added Esoteric Bass RCB and BB Pre AT Drive models.

Update BB Pre Drive model to match latest circuit (version 1.5).

Increased the range of the Level parameters in Multitap Delay to -100% to +100%.

Added cross feedback parameters to Quad Parallel type in Multitap Delay block. Added “Aurora Delay” preset to demonstrate capability.

Added PVH 6160 Crunch model.

Fixed Klone Chiron optional EQ not working.

FC: Fix Layout: Inc/Dec mini-display labels to show the correct destination layout when in Destination # or Destination Name.

Various other fixes and improvements.

=20.03=

Improved Drive block.

Fixed Amp block Transformer HF being incorrectly set when using two Amp blocks.

Fixed Amp block Bypass state not being set correctly when using Scene Manager in Axe-Edit.

Removed USB Buffer Level meters as they are no longer` applicable.

Various other fixes and improvements.

=20.02=

Improved speaker impedance curve fitting algorithm. This results in more accurate and more “colorful” modeling as the previous algorithm tended to damp box resonances somewhat. All the speaker impedance curves have been updated using the new routine. Existing presets are automatically updated to use the updated curves if “Update Pre-20.02 Presets Spkr Imp Upon Load” is set to YES.

Added 4x12 Lerxst Omega speaker impedance curve.

Added 1x12 Deluxe Oxford speaker impedance curve.

Added 4x12 Hipower Pete T speaker impedance curve.

Added 4x12 Hipower Lindsey B speaker impedance curve.

Added 4x12 USA Semi-Open speaker impedance curve.

Added 2x12 Dizzy RV speaker impedance curve.

Added 4x12 London Town Tall speaker impedance curve.

Fixed Tap Times lost during patch/channel changes in Rhythm Tap Delay mode of Ten-Tap Delay block.

The A-Z knob will work correctly in both directions when editing the name of a Setlist.

Changes will now be immediately reflected for all slots when editing a Setlist songs.

Various other fixes and improvements.

=20.01=

Added Speaker Thump control to Amp block. Speaker Thump models the dynamic, nonlinear behavior of a guitar speaker. A value of 5.0 roughly corresponds to an amplifier running into a speaker rated at the same power as the amplifier, i.e., a 100W amplifier running into a 100W speaker. The reset value is a conservative 2.5 which represents, i.e., a 50W amp running into a 100W speaker. Note that the majority of the response is in the subsonic region and the effect is primarily tactile. Existing presets are not affected and the value will be zero.

Improved Amp block output transformer modeling. This requires updated Transformer LF/HF values for the amp models. Existing presets are automatically updated to the new values upon recall.

Decreased minimum diffuser time in Delay block to 1%.

Added G12T-75 speaker impedance curve.

Added 2x12 Class-A Greenback speaker impedance curve.

Added 2x12 Two Stone 1265 speaker impedance curve.

Added Depth control to Authentic page for Brit Super, Brit 800 Mod and JMP-1 amp models.

Added Diamante Fire amp model based on a Diamond Del Fuego.

Changed “Drive” to “Gain” for Amp block preamp gain control as this is more consistent with naming in real amps.

Fixed switching channels on Drive block can cause pop.

Fixed switching channels on bypassed blocks can cause an audio gap.

Fixed wrong drive taper in Mr. Z Highway 66 model.

Fixed wrong capacitor value in Friedman Smallbox model.

FC: Fixed Factory Default layouts so FX Bypass and Channel switches use the correct blocks.

FC: Fixed an issue that prevented the Hold function from working correctly for some Stand-in Switches.

FC: Fixed UI to refresh when performing "Reset" on a Setlist or a Song from the front panel.

FC: Fixed Setlist functions to not load a song when "Song Load" is set to "None"

FC: Layout Link will no longer unduly trigger when exiting the Tuner.

FC: Preset: Select in Bank switches now stop flashing when the preset is changed by any means other than an FC footswitch (editor, front panel, etc.)

FC: Preset: Select in Bank switches now flash consistently when used with Bank: Select switches.

FC: Preset: Toggle in Bank now consistently and correctly loads the "Primary" preset after changing the bank.

FC: Removed "PREVIOUS" from Bank: Select function as it was replaced by "2nd Press = Previous Bank"

Various other fixes and improvements.

=20.00=

New “Block Mixer” algorithm results in faster/quieter scene and channel changes. This new algorithm allows placing Amp blocks in series without the concomitant sound bursts that would normally occur when switching scenes.

New Speaker Drive algorithm in Amp block. This new algorithm more accurately models the frequency dependent distortion of guitar loudspeakers. The default value (upon resetting the block) is 2.0 which gives roughly 1 dB of compression. Setting the value to 0.0 defeats the speaker drive modeling. Higher values give a smoother and more focused sound, rounding off the “sharp edges” and yielding greater compression.

Added new “Dynamic Distortion” block. This effect distorts the input signal dynamically, applying more distortion to different frequency ranges depending upon the shape of the filter. When the signal level is low the output will be the same as the input. As the signal level increases more distortion will occur in those bands boosted by the filter shape. This is a powerful tool for final shaping/mastering of your tone. The block contains a handful of presets which demonstrate the basic technique.

Added ability to use Pre-Delay in Reverb block as a simple echo. Pre-Delay now features Tempo, Feedback and Mix parameters. The pre-delay time has also been increased to 1s. Several types have been added demonstrating the capabilities.

Fixed Amp block Scene Ignore not being recalled correctly in some cases.

Fixed USB buffer level setting not sticking between power cycles.

Layout Link configured on a tap function for a footswitch will no longer incorrectly execute when activating the switch exits the Tuner.

Various other fixes and improvements.

NOTE: THIS FIRMWARE IS NOT COMPATIBLE WITH PREVIOUS VERSIONS OF AXE-EDIT. A NEW VERSION OF AXE-EDIT IS REQUIRED FOR USE WITH THIS VERSION.

NOTE: If you installed firmware 20.00 beta 4, you may find that some FC effect switches are now mapped to the wrong effects. For example, a switch that was set to bypass REVERB 1 may now bypass AMP 1 instead. This release prevents this problem from occurring you are upgrading from 19.x or older.

If you installed 20.00 beta 4, however, this will have already modified your layouts, so you will need to either restore them from a backup, or adjust the individual switches manually. Layouts can be restored using a "System" backup from Fractal-Bot, or a "Layouts" file from Axe-Edit. If you'd rather reset to the factory default FC layouts, find this under SETUP> FC Controllers> Reset.

=19.08=

Fixed error in Amp block low frequency resonance behavior.

=19.07=

Fixed bypass state can load wrong when switching from a preset with Scene Ignore on.

Changed Compressor block so that times display actual value for the various pedal types.

Various other fixes and improvements.

=19.06=

Added new Setlists/Songs feature, which can be used with an FC Controller to access presets and scenes in custom order during live performance. A new Setup menu area provides full access from the front panel, with a corresponding new area of Axe-Edit which offering import/export and more. For additional details, please see the Setlists & Songs Mini-Manual, located at: https://www.fractalaudio.com/sss-manual

Added Scene Ignore to Multiplexer block.

Improved Amp block transformer/speaker interaction modeling. The “Voice Coil Resistance” parameter has been repurposed/renamed “Speaker Impedance”. The various parameters work as follows:

* Transformer Matching: Sets the impedance ratio (square of the turns ratio) of the output transformer.
* Speaker Impedance: Sets the relative nominal impedance of the speaker. To simulate connecting, e.g., a 4-ohm speaker to an 8-ohm output you would set Speaker Impedance to 0.5. Conversely to simulate connecting a 16-ohm speaker you would set it to 2.0.

Update PI Bias Excursion parameters for many Amp models based on new measurement technique.

Fixed Parametric EQ and Megatap blocks can cause GUI hang if modifier attached to parameter and update rate is set to FAST.

Fixed crash in Plex block for certain types if Master Time is set to zero.

Fixed Amp block output transformer turns ratio being incorrectly calculated.

Fixed IR Player block displayed IR number off by one after preset recall.

Fixed Stand-in switches will now work correctly when assigned to a footswitch configured as a Per-Preset: Placeholder.

Fixed Ultra-Res IRs being truncated to 1K samples by IR Capture utility and Tone Match block.

Various other fixes and improvements.

=19.05=

Added “Scene Ignore” to most blocks. When set to ON, Scene Ignore instructs the block to ignore scene changes. Scene Ignore is a per-channel parameter. This allows turning Scene Ignore to OFF on one or more channels which will then allow a scene change to set the block to a desired state if the block is on that channel.

Improved CNFB algorithms in Amp block resulting in smoother distortion and improved clarity.

Improved preset/scene switching when input impedance changes between presets/scenes.

FC: Switch Ring Color settings of "Off" will now work correctly.

FC: Effect: Chan Select LED ring will properly be dim when an effect is bypassed.

Various other fixes and improvements.

=19.04=

Fixed some Amp models can NaN due to index out-of-bounds.

=19.03=

Added Dual Detune Delay type to Pitch block. This type is comprised of two detuners with delay up to 2.0 seconds. Each detuner can feed back to itself and/or the other detuner.

Renamed Oversampling Mode “BEST PERFORMANCE” to “BEST QUALITY” for clarity.

Fixed Amp block instability when Output Mode is set to FRFR and Voice Coil Resistance is set very high.

Fixed Bludojai Lead model missing resistor between last preamp stage and power amp.

FC: Fixed Stand-In Switches not displaying correctly for certain switches.

FC: When the Effects: Chan Select function is used with SMART BYPASS selected as 2nd Press, the main LCD will now display ENABLED/BYPASSED along with the configured channel.

FC: Corrected a bug which caused some per-preset switches to not show the desired mini-display text or LED ring color.

Various other fixes and improvements.

=19.02=

Updated 59 Bassguy and 5F8 Tweed models to include both Drive controls.

Added 59 Bassguy Normal, 5F8 Tweed Normal and 5F8 Tweed Jumped amp models.

Added JMPRE-1 Output EQ type to Amp block. This type replicates the active EQ used in the JMP-1 preamp (see below).

Added JMPre-1 Clean1/2 models. Note: The real amp has a fixed, passive tone stack with an active 4-band EQ. Therefore, the Bass/Mid/Treble controls when using Authentic Tone Controls are mapped to the Graphic EQ. The passive tone stack itself, however, is adjustable. With all controls at noon the tone stack is equivalent to the real amp’s fixed tone stack. You can access these controls using the Ideal Tone Controls or via Axe-Edit.

Updated JMPre-1 OD1/2 models. As with the Clean1/2 models the Bass/Mid/Treble controls now are mapped to the Graphic EQ when using Authentic Tone Controls.

Updated default cathode follower values for Matchbox D-30 model.

Added Spread control to Dual Delay and Tape types in Delay block. Spread acts as master pan in this case and is modifiable.

Added assignable third LFO to Delay block. This LFO can be assigned to Level, Pan or Spread and multiplies the corresponding value by the LFO value.

Added “Oversampling Mode” to Global menu. This parameter allows selecting between BEST PERFORMANCE and MIN. LATENCY.

Improved Input block gate performance.

Fixed Drive block can crash under rare circumstances when switching between certain models (from Blackglass 7K to diode-based model).

Fixed Amp block Transformer Match control not working properly.

Renamed Speaker Impedance to Voice Coil Resistance to more accurately describe the function of the control. Note that this includes all other “parasitic” resistances, i.e., speaker cable resistance, output transformer winding resistance, etc.

Rearranged order of pages in Amp block so that Input EQ and Output EQ are after Tone page.

Fixed Flanger block can cause loud transient at startup in rare circumstances.

The following FC enhancements/fixes are implemented:

* Added “Scene Level + Save” to the “Utility” functions.
* Added "Invert Mini-Displays" under the APPEARANCE section of the FC Controllers’ Config page.
* Added a “STARTUP VIEW” to the FC Controllers: Device page.
* Added an option for “2nd Press = Previous Bank” to Bank: Select function.
* Added an option for “2nd Press = Previous Preset” to Preset: Select and Preset: Select in Bank functions.
* Added the option “2nd Press" to Effect: Select Channel function. The two choices are "Smart Bypass" which is a pre-existing feature, and "Previous Channel" which toggles to the previously selected channel instead.
* Added a “Current Channel” Mini-Display Label option to Effect: Chan Inc/Dec.
* Added a 1.5 second delay to functions that trigger a save of the preset to allow multiple actions before a single save.
* Fixed Bank limit calculations in some circumstances.
* Updated the switch ring LED to be dim instead of off for Function Effect: Select Channel when Smart Bypass is ON and the effect is in the preset but the effect is bypassed.
* Fixed stand-in switches not executing the tap function correctly when a hold function is assigned.
* Added "Current" option to the display functions for Bank: Inc/Dec function.
* Added "Current Name" and "Current #" options to the display functions or Preset: Inc/Dec and Scene: Inc/Dec functions.
* Fixed an issue when changing function to "Bypass" when the currently selected effect does not have a Bypass function (e.g., Mixer, Multiplex).
* Fixed an issue when changing FC effect type from "MultiPlex" to an effect containing fewer channels.

Various other fixes and improvements.

=19.01=

Added Damping control to Modifiers. The default, EXPONENTIAL, is the classic damping style where the modifier value has an exponential attack/decay. LINEAR selects a linear attack/decay.

Added Type control to ADSRs. The default, EXPONENTIAL, is an analog style where the ADSR has an exponential attack/decay. LINEAR selects a linear attack/decay.

Improved Phase Inverter Bias Excursion accuracy for some amp models (mostly non-MV types). Note: The improved PI Bias Excursion accuracy results in an increase in bias excursion in most cases. Bias excursion primarily manifests as intermodulation distortion, particularly subharmonic distortion. This produces a chunkier tone with more growl and also yields a thicker tone when rolling off the volume or playing lightly. The amount of bias excursion can be adjusted using the PI Bias Excursion control in the Advanced menu.

Renamed Timothy and Suhr Riot Drive models to clarify switch position.

Added Hi Mid control to Drive block.

Fixed Blackglass 7K model as reference pedal was defective. Added “Grunt” and “Attack” knobs to GUI (Grunt switch on pedal is a selectable low cut so knob duplicates Low Cut control).

Changed response of Horizon Precision Drive “Attack” control to match pedal (was reversed previously). Any presets using this model should be adjusted accordingly.

Improved accuracy of “G-taper” used for tone control in some Drive models, i.e., T808, VS9, Super OD, etc. Impact on existing presets is likely negligible but any presets using Tube Screamer models and their variants should be auditioned.

Fixed selecting Gibtone Scout tone stack causes NaN in certain amp models.

Fixed Amp block headroom meter monitoring wrong circuit node.

Fixed GUI not being redrawn when switching between a knob menu and a list menu.

Various other fixes and improvements.

=19.00 =

Version 19.00 firmware represents the first use of the Chase Nonlinear Feedback (CNFB) technique for the solution of nonlinear ODEs. The power amp algorithm has been completely rewritten using the CNFB method. This provides improved accuracy, especially in the clipping and power supply sag behavior vs. frequency.

Added y-axis labels to RTA.

Added Time Shape parameter to Megatap Delay. The EXP/LOG setting is the default and behaves as before allowing time shapes between exponential and logarithmic (including linear). The SIGMOID setting is a four-quadrant shape that allows time shapes between sigmoid and inverse sigmoid. The COSINE and SINE settings select sine wave shapes with the Time Alpha parameter controlling the number of periods from 1 to 8.

Added 11 power tube types from various manufacturers.

Improved Amp block bypass/engage behavior to prevent level surges.

FC: Amp Level Save now has an option for 0 dB to allow saving a preset via a footswitch.

Fixed signal level into power amp a bit too high in 6160 models.

Fixed High Cut control not working in Mr. Z MZ-38 model.

Fixed Compressor block Auto Makeup Gain not being updated when changing types.

Fixed wrong op-amp clip threshold for DS1 models in Drive block.

Various other fixes and improvements.

<blockquote>"I would say that the biggest change in 19.x vs. 18.x is the clipping behavior of the power amp. The preamp is not changed at all so anything you are hearing is due to the new CNFB power amp stuff. The power amp clips softer now. This is more accurate, however. If you want a harder power amp clipping, which people that are into aggressive styles may desire, increase the Power Tube Hardness parameter. Or turn the MV down a little. 19.x also introduces an improved feedback algorithm in the power amp. It uses what I call "hybrid feedback" and is a way of replicating analog feedback in a nonlinear discrete-time system. This yields better frequency response accuracy above 10kHz compared to 18.x. 18.x tended to be a little brighter as a result. To get this brighter sound in 19.x increase the Transformer HF value." [https://forum.fractalaudio.com/threads/firmware-19-x-is-there-a-quick-fix-to-make-fas-amps-sound-like-18-x.181292/post-2222077]</blockquote>

=18.03=

Fixed Angle Severe and Energyball amp models hanging on certain combinations of Presence and Depth.

Fixed USB Output summed to mono if Global Output Mode set to MUTE.

Various other fixes and improvements.

=18.02=

Fixed cathode follower algorithm not working correctly for some models.

=18.01=

Fixed error in Amp block low frequency dynamic speaker impedance calculation.

=18.00=

Overhauled the Compressor block:

Improved Auto-Makeup gain behavior.
Added Input Level switch. When set to INSTRUMENT the detector is optimized for guitar-level signals, i.e., before an amp block. When set to LINE the detector is optimized for post-amp level signals.
The Pedal, Optical, Tube, Analog, JFET and Dynamicomp types have been completely redone resulting in improved performance. These types now inherently perform automatic makeup gain.
Auto Attack/Release has been removed from the Pedal and Dynamicomp types as it is no longer applicable.
NOTE: Due to all these changes the behavior and output volume of the Compressor block may be different. It is recommended to audition any presets using the Compressor block and adjust as required.
Improved Stack/Hold implementation in Delay block so that “texture” is applied to audio when Stack/Hold is on.

Improved Amp block cathode follower algorithm. Algorithm now uses higher order solution of nonlinear ODE for more accurate low frequency response.

Improved Amp block power amp algorithm. New algorithm more accurately models dynamic changes in speaker impedance resulting in more “complexity”.

Improved Tape preamp types in Cabinet block.

Added check to prevent excessive message queuing, i.e., when selecting amp model using Value knob.

Added MUTE option to Output 1/2 Configuration. This allows muting the analog outputs while still passing data via USB. This can be used when using the Axe-Fx III in conjunction with computer plug-ins.

Added global Speaker Impedance Curve. When set to DEFAULT the speaker impedance curve used when selecting an amp model is the default curve for that amp model, otherwise it is the selected curve. NOTE: this does not affect existing presets. The selected curve is used only when selecting a new amp model.

Added Input Level switch to Compressor block. This allows tailoring the compressor’s response for instrument level or line level signals.

Added several new Impedance Curves to Amp block. Thank you to Dr. Bonkers Soundlab for these.

Added Modifier capability to LFO Enable and Mod Frequency in Filter block.

Added RCB Boost to Amp block Boost types.

Reduced CPU usage for background GUI tasks.

Fixed DS-1 Drive types have no gain when Drive is at 0.0.

Fixed Reverb pitch buffers not being cleared if Pitch Mix is zero.

Fixed Turbo version aborting processing at CPU usage lower than limit.

Fixed Angle Severe models becoming unstable with certain speaker impedance curves. Note: the presence network for these models has been updated. Presets using these amp models should be auditioned as the tone may have changed.

Various other fixes and improvements.

=17.02=

Added “ALL” as an option to Spillover in Global Settings. When Spillover is set to ALL the Delay, Reverb, Plex, Multi-Delay, Megatap and Ten-Tap blocks will not clear their buffers when switching presets.

Fixed Amp block Master Volume not working properly for JS410 and Texas Star models (introduced in 17.01).

Improved IR Player block so that volume is consistent if Mode is set to Parallel and only one IR is being used.

Fixed Plex and Multi-Delay Blocks displaying wrong type when recalling preset.

=17.01=

Added 10 FullRes IRs to the Legacy bank provided by Valhallir and York Audio. These are at the end of the bank. These can be loaded into the IR Player blocks or into Slots 3 and 4 of the Cabinet blocks. Note that Slots 1 and 2 of the Cabinet blocks do not support FullRes.

Adjusted Looper behavior so that when reaching the maximum recording time the behavior switches to that defined by Record 2nd Press ONLY on the first pass of a new recording.

Added dedicated Pitch Shifting to the Reverb block. This can be used to create “Shimmer Reverbs” easier than using separate Pitch and Reverb blocks (and with less CPU usage). Several new types are included to demonstrate the capability.

The Pitch Direction parameter controls the direction of the pitch shifters. FORWARD runs both shifters forward. REVERSE runs both in reverse. FOR/REV runs Voice 1 forward and Voice 2 in reverse. REV/FOR runs Voice 1 in reverse and Voice 2 forward.

The Pitch Position parameter controls the location of the pitch shifters. INPUT locates the shifters at the input of the block. MATRIX locates the shifters inside the reverb matrix. FEEDBACK locates the shifters in the matrix feedback loop. MATRIX and FEEDBACK can yield more intense effects and also helps the reverb “stick” to the notes better. FEEDBACK builds slightly slower than MATRIX. CAUTION: The MATRIX and FEEDBACK positions can cause instability at high values of Pitch Mix and Pitch Feedback. In general Pitch Feedback should be low or zero when using MATRIX or FEEDBACK.

Overhauled the Megatap block. See the updated Blocks Guide for details.

Added modulation to Diffusers in the Delay, Multitap and Megatap blocks.

Improved Auto-Swell type in Volume block. Added S-Taper to taper selections.

Added Modern Gate type to Gate block. This type is similar to the Classic Gate except the gate opens in a constant linear-in-dB manner. This naturally makes the attack slower as the gate first opens and can be used for both traditional gating and for special effects like audio swells.

Increased maximum sustain for the applicable types in the Compressor block. Existing presets are automatically updated.

Added new types to the Multitap Delay block.

Added new types to the Plex Delay block.

Added LFO for filter in Plex Delay block.

Added new types to Flanger block.

Improved accuracy of Master Volume in Amp block for low settings.

Improved accuracy of Drive block Drive control for low settings.

Fixed wrong resistor value in Solo 88 Lead input circuit. Impact is probably negligible.

Fixed wrong resistor value in USA Pre LD2 overdrive circuit. This increases gain slightly. You may need to audition any presets using these models and adjust gain accordingly.

Fixed Multitap block bandpass filters not being disabled if Master Q set to minimum.

Fixed block input not muting in bypass if Bypass Mode is Thru.

Fixed Chorus block left delay line getting unsynchronized when switching between types.

Fixed pressing Tuner button in Axe-Edit brings up Reverb UI.

Fixed Amp block power tube “kvb” not being set correctly in rare circumstances. This caused the output level of the amp block to change depending upon the previous preset used.

Fixed wrong B+ voltage for Temolo Lux amp model.

Fixed IR Capture not saving correctly if IR Type set to UltraRes.

Improved CPU usage.

Various other fixes and improvements.

=17.00=

Version 17 introduces FullResTM Impulse Response processing. FullRes processes IRs up to 64K points with zero latency using a novel technique. This provides up to 1.37 seconds of response time. Seasoned producers and engineers often mix in “Room Mics” during recording to increase the depth and liveliness of recordings. However, the typical live room has a reverb time of 500-700 milliseconds, well beyond the 20-40 ms afforded by typical IR processing. FullRes allows capturing the full response of a typical live room and even the response of small-to-medium halls and clubs. FullRes can also be used for convolution reverb applications for reverb times less than 1.37 seconds.

The IR Player block and the Cabinet block both support FullRes IRs. The last two slots of the Cabinet block support FullRes. This is sufficient to provide two room mics, a left and a right, along with two direct mics within a single Cabinet block.

The new FullRes User IR bank supports up to 64 FullRes IRs. When capturing an IR selecting the USER FR bank will automatically set the IR Type to FullRes. Likewise, when setting the IR Type to FullRes the bank will automatically be set to USER FR. FullRes IRs can be processed with minimum-phase or auto- trim, if desired. However, minimum-phase is not recommended as this will tend to destroy the reflection information.

The Scratchpad bank has been updated to support FullRes IRs.

NOTE: The FullRes User IR bank is only available on the Axe-Fx III Mark II. The original Axe-Fx III has less non-volatile memory and therefore does not have the necessary resources to store the IRs. The Scratchpad bank supports FullRes IRs but the data will be lost when the unit is powered off.

IR management has been completely rewritten providing smoother performance and better integration with Axe-Edit.

The IR Player block now supports two IRs with individual level and pan controls for each IR. Setting the IR Length to OFF defeats the IR. A Mix control is also provided so the block can be used as a convolution reverb. A Mode control allows the two IRs to be in parallel or series. When in series the individual level and pan controls are defeated and removed from the UI.

Increased Mic Distance range in Cabinet block to 3.4m (~11 feet). This allows delaying room mic IRs that have been trimmed to remove the leading silence. The alignment graph now features a Zoom control that changes the abscissa between 3ms and 12ms.

Improved Pitch Detection performance.

The UI has been improved to support double-tap of certain keys as follows:
* Double-tapping EDIT edits the previous block.
* Double-tapping HOME enters the layout grid.
* Double-tapping STORE prompts immediately.
* When on the Home or Layout pages double-tapping the Quick Entry knobs does the following:
** A: Enters the Amp 1 menu.
** B: Enters the Drive 1 menu.
** C: Enters the Cab 1 menu.
** D: Enters the Delay 1 menu.
** E: Enters the Reverb 1 menu.

The buttons in the effects GUI have been simplified to a single page.

Fixed names of Dizzy V4 2 and Dizzy V4 3 swapped.

Added FAS Buttery amp model.

Added 1S1588T diode SPICE model to Drive block. This is the Toshiba version of the 1S1588 and is reportedly the diode used in the “best sounding” TS-808s. The T808 OD models have been updated to use this diode. Existing presets are unchanged.

Added “Valve Screamer VS9” and "Maxoff 808" Drive models.

Improved scene switching to prevent signal “leaking” into bypassed blocks.

Added Max Loop Time parameter to Looper. This sets the maximum recording time. This allows a loop to be automatically created once the loop time exceeds this value.

Changed Looper behavior so that if recording and time reaches the maximum recording time the mode changes to that specified by Record 2nd Press.

Added support for Axe-Fx III Mark II “Turbo”.

Various fixes and improvements.

=16.05=

Improved behavior of Synth block Shift control when attached to a modifier.

Fixed Compressor block GUI not displaying properly in some cases.

Fixed FAS Brootalz model inadvertently changed since it was referencing the Angle Severe presence network which was changed.

Fixed Master Time not working in Plex block for Plex Detune and Plex Shift types.

Fixed Tone Match block IR Slot number in Export page not displaying correctly in some circumstances.

=16.04=

Added “Indicate Edited on Scene Change” to Global Settings.

Improved Sequencer functionality. The Run control has now been expanded to STOP | PAUSE | RUN. When set to PAUSE the sequencer will halt but not reset the sequence count. The Step control allows manually stepping the sequencer when the sequencer is paused or running.

Improved Rotary block drive algorithm.

Fixed using two Amp blocks in certain combinations of models causing high frequency whine.

=16.03=

Updated Amp block default Excursion Time and Release Time values as some were entered incorrectly. Existing presets are automatically updated to the new default values upon recall.

Improved Delay block algorithms and models. Improved menus by adding a basic Config page with the essential controls and an Advanced page with all the controls for that model. Added a Master Time control.

Added Compander type to Compressor block. The Transients control adjusts the transient modification. Values less than zero soften the attack, value greater than zero emphasize the attack.

Improved Amp block power amp transient response accuracy.

Fixed wrong attenuation between preamp and power amp in Class-A 30W Bright model.

Fixed Headroom meter stuck in certain circumstances when using two Amp blocks.

Fixed Amp block displaying wrong channel number when setting channel via Scene Manager in Axe-Edit.

Fixed pop when switching channels on Input block when using different gate types.

=16.02=

Improved Amp block power tube grid bias excursion algorithm. The default Excursion Time and Release Time values have been updated as a result. Existing presets are automatically updated to the new default values upon recall.

Improved Delay block so repeats do not degrade when Hold is activated.

Added Rows 1-6 as Reference Sources for Tone Match block.

Added Power Amp Modeling ON|OFF control to Amp block and removed that functionality from the Supply Sag control. Existing presets are automatically updated upon recall.

Fixed Master Comb Time not working in Multitap Delay block when using Quad Series type.

Fixed Reverb High Cut Slope not working.

=16.01=

Improved output transformer / speaker impedance interaction modeling. This yields more accurate low frequency response. Note that the Transformer LF parameter effectively adjusts the transformer’s inductance. Increase this value to simulate a smaller transformer, decrease to simulate a larger transformer.

Improved power amp cathode current calculation accuracy for cathode biased models.

Updated default Power Tube Grid Bias and Negative Feedback on many models based on new measurement technique. NOTE: As a result of this existing presets will update the aforementioned parameters to the new default values upon recall.

Added frequency cursor to Parametric EQ graph.

Updated Blackglass 7K Drive block model. Previous model was incorrect due to defective reference unit.

Increased gain range of Filter and Parametric EQ blocks to +/-20 dB. Also increased gain range of input EQ in Amp block. Existing presets are automatically updated.

Improved Reverb algorithms. Added a couple new types.

Fixed incorrect channel indication in Amp block when changing scenes if Scene Revert is true.

Fixed incorrect Drive control taper in Jr. Blues amp models.

Fixed missing UI for several Friedman amp models.

Fixed missing pad between preamp and power amp in USA Pre Lead models.

Fixed pop when changing Amp block channels between models with disparate gains.

Fixed switching to a preset with a Reverse Delay from certain other presets causes noise burst at switchover.

=16.00=

New “Cygnus” amp modeling algorithms.

Added “Sonic Dist” Drive type.

Fixed popping when switching channels in Drive block in rare cases.

Fixed Studio FF Compressor 2 type not working properly if Knee is set to “Hard”.

Fixed Delay block maximum time limited to 8s regardless of entered time.

Fixed Amp block not updating properly when changing scenes if Scene Revert is on.

Various other fixes and enhancements.

=15.01=

Improved output transformer modeling in Amp block. For typical values of Transformer Drive the difference is subtle but mathematically more accurate adding a pleasing low-end growl and improving “tightness” in high-gain sounds. For high values of Transformer Drive the difference is more pronounced. If you have increased Transformer Drive on your presets above the default value then you should audition your presets.

Fixed Depth control not working on some amp models.

And: MCMLXXXI Drive MODEL, based on 1981 Inventions DRV.

=15.00=

Improved Amp block power amp modeling. Improved algorithm yields accurate dynamic frequency response which results in clearer bass and extended highs. More “chug”, “thump” and “chime”. NOTE: Existing presets should be auditioned. While the overall tone isn’t significantly changed, the transient frequency response is enhanced which may alter the tonal perception.

Added ability to route AES/SPDIF or USB 5/6 to any input. This has been achieved by changing “SPDIF/AES Select” to “Digital Input Source” which allows choosing between AES, SPDIF or USB 5/6. Each input now has an “Input Source” selectable between Analog or Digital.

Increased maximum delay time for Delay blocks to 16 seconds.

Added “DS1 Distortion” Drive type.

Added “DS1 Distortion Mod” Drive type based on a DS1 w/ popular mods.

Added “59 Bassguy Jump” amp model.

Many of the Fender® amps have been “modified” with authentic presence and depth networks even if the real amp doesn’t have them (this was required for the new power amp algorithm). When the Tone Control Display is set to IDEAL the Presence and Depth controls can be used to shape the power amp response just as if the real amp had been modified. Setting the Presence and Depth controls to zero effectively removes the modifications. WARNING!!! If your presets use non-zero values of Presence and/or Depth for amp models whose real counterparts do not have presence and/or depth circuits your presets may sound different and should be adjusted accordingly. I.e., if you have turned Presence up for the Deluxe Verb model your preset’s tone will have changed as a real Deluxe Reverb does not have a presence network (and Presence defaults to zero for that model).

Fixed GUI bug for TS9DX Hot model.

Fixed Scales menu in Global Settings.

Fixed clicking in Amp block if large number of modifiers are connected to controls.

Fixed modifiers connected to Amp block can cause unwanted change if modifier is only active for one channel.

Fixed erroneous values can be displayed when changing channels on a block and the GUI configuration between channels is different, i.e. different number of EQ sliders or different authentic amp parameters.

Fixed second pot of ganged dual pot in Citrus Terrier amp model applied at wrong point in circuit.

Fixed Ratio at maximum in Compressor block should display “INFINITE” but doesn’t when first entering page.

=14.06=

Fixed bypass state not changing in Layout menu when zoomed out.

Fixed Metronome Level controls in Tempo menu not updating.

Fixed LFO Phase parameter doesn't work when LFO Type is set to ASTABLE.

Fixed 0.2 dB loss in some blocks (i.e. the Return block).

Reduced audio gap when switching channels in Amp block.

Added “TS9DX Hot” Drive model.

=14.05=

Improved client-server protocol to reduce message traffic. This results in snappier GUI performance especially for presets with high CPU usage. The new protocol is backwards compatible with Axe-Edit, however the latest version of Axe-Edit is required to take full advantage of the improvements.

Improved Amp block power tube grid clipping algorithm.

Fixed error in Studio FB compressor type that could result in distortion under certain circumstances.

Fixed wrong gain constant in Tube Drive 4-Knob model.

Fixed feedback network not fully initialized in Recto and Triple Crest models. In most cases this is inaudible but in rare cases when switching between Amp block channels the tone and gain of the power amp could be incorrect.

Fixed LFO Phase not working when LFO type is set to Astable.

Fixed incorrect extra feedback path in Pitch block for Quad Chromatic Delay and Quad Diatonic Delay types.

=14.04=

Fixed NaN when setting a tone control to zero in certain amp models (introduced in 14.02).

=14.03=

Fixed Cabinet block LF/HF damping applied to only left/right respectively.

Fixed setting a tone control to maximum in Amp block can cause NaN in certain models (introduced in 14.02).

=14.02=

Fixed Euro Uber model gain dropping if Input Drive set to maximum.

Fixed Fat Switch changing wrong capacitor value on Archean model.

=14.01=

Added semi-parametric EQ to Multitap Delay block. The EQ is similar to the Filter block with the addition of selectable low cut and high cut filter slopes. Note that the overall gain of the EQ automatically adjusts to unity when using any filter types that boost frequencies so as to prevent instability.

Added second source to Modifiers. A Modifier can now have two sources: Source 1 and Source 2. Each modifier has an individual Scale parameter from 0 to 100%. The operation between the two sources is selected via the Operation parameter and allows addition, subtraction or multiplication of the two sources.

Changed behavior of Random LFO so that value changes when switching from Stop to Run.

Improved boot time.

Updated Euro Uber amp model. It is recommended to do a soft reset of the model by deselecting and then reselecting the Amp type.

Added several new amp models.

Fixed wrong capacitor value in Brit JVM OD1 Orange and Red models.

=14.00=

Improved Amp block cathode follower accuracy. The Hardness parameter has been removed and the default values have been changed. Existing presets are automatically updated. If you have edited the cathode follower parameters you should audition your presets as these parameters will automatically be reset to default values when the preset is loaded.

Because of the cathode follower change the following amp models have been updated:
* Friedman Small Box
* Dizzy V4 Blue (all models)
* Herbie (all models)
* Recto 1/2 (all models)

Due to the discovery of a measurement error the JMPre-1 models have been completely reworked. If you are using any of these models it is recommended to reset the block and audition your preset(s).

The Tube Pre model has been changed so that the power amp is off by default.

Added a couple new amp models.

Fixed turning Diffusion Time all the way up in Delay block causes noise.

Fixed ADSR graph goes funky if Attack time is set very low and other times are relatively large.

Fixed knob labels for sliders not centered under sliders if number of sliders is less than 5.

=13.03=

Added modifier capability to Multitap Delay block Level parameters.

Added modifier capability to Synth block Attack parameters.

Fixed Amp block generating NaN at startup in rare cases due to uninitialized data. Fixed output level knob value not applied to Output 1/2 if Global EQ type set to NONE. Fixed first preset may be temporarily erased if corrupted data in User Cab Bank.

FC: Tuner will now automatically display whenever tuner is displayed on Axe-Fx III.

=13.02=

Added “Compulsion Distortion HP” Drive type. Existing type name changed to “Compulsion Distortion LP”.

Added “Tuner on Heel Down” to MIDI/Remote. The corresponding controller will automatically display the tuner when the value is less than 5%. Typically the user would set this to the same CC# (or internal/external pedal) that they use for their primary volume control, whether that is assigned to a global volume control or to a modifier in a Volume block. For example, if you use CC #23 as External Control 1 and connect that to the Volume 1 block in all your presets then set this to 23. Likewise if you use FC 1 Pedal 1 as a global Input 1 Volume control then set this to FC 1 Pedal 1. Now when you set your expression pedal to the heel down position the tuner will automatically display.

Added marker to ADSR graphs. Also changed ADSR graphs to show curves in linear units (rather than log).

Added Master Chorus Rate and Master Chorus Depth parameters to Multitap Delay block. The Master Rate and Master Depth have been renamed Master LFO Rate and Master LFO Depth. Master LFO Depth no longer controls the chorus depth.

Improved layout of Multitap Delay GUI.

Improved Drive block CPU usage for diode-based models.

Improved CPU usage for Reverb block in high-quality modes.

Fixed filter modulation not working in Multitap Delay block.

Fixed Graphic EQ not working for Output 1 and 2.

Fixed USB/Digital Metronome Level controlling wrong output.

=13.01=

Fixed global Input Gain loading wrong value.

Changed global Input Gain and Amp block Input Trim to read in linear units due to confusion over the meaning of dB.

=13.00=

Improved Drive block modeling. New algorithm uses a novel solution to solve the nonlinear ODE of a diode clipper with memory (i.e. a capacitor). The accuracy of the diode I-V curve is also greatly improved. This new algorithm has the accuracy of implicit iterative solutions with speed rivaling explicit solutions. CPU usage is only slightly increased vs. the previous algorithm. Note that many of the Drive models will now behave differently and presets should be auditioned. The behavior of the tone controls in some models has also changed. Of note are the Timmy models where the tone controls are now faithful to the actual pedal and decrease bass/treble when turned clockwise.

The Drive block now features a “Bass Response” control for types based on the Rat, Tube Screamer and various derivates. In some models this is duplicated on the Basic page as it is the Bass/Voice/etc. control (and renamed accordingly). This function was previously provided by the Low Cut control. The Low Cut control is now a separate control that allows adjusting the input highpass frequency. Existing presets will automatically be updated with the new default value for the Low Cut control.

Added Bias control to GUI of all Drive block models.

Added “Headroom” monitoring meter to Amp block. The most common reason for “muddy” tones with high-gain amps is incorrect setting of the Master Volume control. The Headroom meter displays the voltage at the virtual power tubes in dB. If the Master Volume is too high the meter will be near 0 dB most of the time. Note that this only applies to amps where the power amp is intended to run “clean” like the 6160, Recto, etc. Non-Master Volume amps get their distortion from the power amp distorting so this recommendation does not apply.

Added Global EQ to all outputs. Note that the EQ for Outputs 3 and 4 is not active if that output has Copy Input 1 set and the corresponding Output block is not in the patch.

Added selectable Graphic/Parametric EQ for Global Output EQs.

=12.14=

Improved Amp block Speaker Compression modeling. New algorithm is more accurate and sounds smoother with more “growl”.

Fixed incorrect default Negative Feedback for Deluxe Verb models (correct value is 2.00 if you want to update existing presets).

Fixed NaN when changing Drive block type if modifier is attached to Drive or Tone.

=12.13=

Changed Amp block Input Trim to read in dB.

Fixed Setup -> MIDI/Remote menu corrupted.

=12.12=

Added Modifier capability to:
* Controller block LFO Output B Phase
* Input block Output Level
* Amp block Variac
* Amp block Input EQ Frequency
* Amp block Graphic EQ
* Parametric EQ block Freq, Q and Gain
* Graphic EQ block sliders

Added Input 1 Gain parameter to Setup->I/O->Input menu. This allows trimming the Input 1 gain to adjust for variations in guitar output level without having to adjust each preset.

Changed Home menu behavior so that selected page doesn’t change after recalling a preset from the Preset page.

FC: FC #4 will now reflect the appropriate layout

FC: Disable FC-6/FC-12 compatibility mode when loading FC-6 factory defaults

NOTE: This firmware is NOT compatible with Axe-Edit versions prior to 1.06.00. You MUST install 1.06.00 or later BEFORE using Axe-Edit with this firmware.

=12.11=

Added LFO High Cut to Controllers.

Fixed Flanger block Rate not updating correctly.

Fixed missing PHV 6160+ CLEAN tone stack string.

NOTE: This firmware is NOT compatible with Axe-Edit versions prior to 1.06.00. You MUST install 1.06.00 or later BEFORE using Axe-Edit with this firmware.

=12.10=

Changed External Controller Initial Values to be continuously adjustable from 0 to 100%.

Fixed Amp block crackling in rare cases.

Fixed Amp block Variac has no effect when Supply Type is set to DC.

Fixed NaN if Reverb block Crossover Freq is set very high and Low Freq Time is set very low.

NOTE: This firmware is NOT compatible with Axe-Edit versions prior to 1.06.00. You MUST install 1.06.00 or later BEFORE using Axe-Edit with this firmware.

=12.09=

Improved power tube modeling yields smoother overdrive especially for semi-clean and edge-of-distortion tones.

Increased Amp block B+ monitor range as Variac settings can cause B+ voltage to fluctuate beyond visible limits.

Added 6CA7 power tube type. While the 6CA7 is generally regarded as a substitute for the EL34 it is actually a different tube with the 6CA7 being a beam tetrode. This particular tube type is modeled after the original Sylvania “Fat Bottle” 6CA7.

Increased tuner sensitivity.

Fixed clicking when changing MUTE/SOLO switches in Cabinet block while playing.

Fixed click/pop in Pitch block when going from negative (or no) shift to positive shift.

Fixed Pitch block Custom Scale number not displaying correctly.

=12.08=

Improved Reverb algorithms.

Added ECONOMY mode to Reverb block. This can be used to reduce CPU usage when building elaborate presets.

Decreased minimum Attack Time of Compressor block to 0.1 ms. Existing presets are automatically updated.

Added JFET Compressor type.

Added three new Studio Compressor types. Studio FF Compressor 2 is similar to Studio FF Compressor 1 (formerly called Studio Compressor) except that it is an “upwards compressor” as opposed to a downwards compressor. Studio FB Compressor 1 and 2 are feedback compressors with downwards and upwards compression respectively. As these are feedback compressors, they yield a different sound than a feedforward compressor commonly referred to as “fat” with smoother dynamics. Note that nature of feedback compressors can result in distortion at extreme control settings (fast attack/release, high ratio, etc.). It is therefore recommended to set Auto Att/Rel to ON in these instances.

Improved Intelligent Pitch Shifter algorithm. This applies to all Pitch types except Dual and Quad Detune or when the Tracking Mode is set to OFF. The pitch detection algorithms have also been improved. The Tracking Mode parameter has been renamed “Pitch Tracking” and is selectable between OFF, FAST and SMOOTH.

Improved pitch detection for Synthesizer and Ring Modulator blocks.

Improved Crystal Echoes algorithm. The Crossfade Time and Crossfade Type parameters have been removed as they are no longer applicable.

Added Diffusion to Crystals type in Pitch block. This can be used to “smear” transients for a softer sound.

Improved Plex Shift and Plex Shimmer types in the Plex block. The Cross-fade parameter has been removed. For the Plex Detune type the Cross-fade parameter has been renamed Granule Length as that is a more accurate description.

Improved Envelope Followers in Megatap, Multitap and Plex Delay blocks.

Added PVH 6160+ Clean Bright and PVH 6160+ Crunch Bright amp models based on a Peavey 6505+ Rhythm channel with the Bright switch engaged. Note that the bright switch on this channel does not engage a capacitor on the drive potentiometer as is typical but instead disengages a treble cut circuit.

Renamed PVH 6160+ Rhythm and PVH Rhythm B models PHV 6160+ Clean and PVH 6160+ Crunch respectively for clarity.

Improved Downward Expander in Gate block when Detector Type is PEAK.

Removed the Frequency Range parameters from the Multiband Compression block and extended the range of the Crossover Frequency parameters to cover the entire range previously available. Existing presets are automatically updated. Note that when adjusting a Crossover Frequency that the unit will automatically adjust the complementary frequency to ensure the mid band is at least one octave wide.

Fixed Tremolo block trigger turning off even when threshold is set to OFF.

Fixed wrong resistor value in Brit JVM models causing excessive blocking distortion.

Fixed using Astable LFO type in some effects causes noise.

Fixed switching between types in Chorus block can causes clicks.

Fixed wrong default Depth value for 5153 Red model (real amp has fixed depth resistor). Removed Depth controls from all 5153 Authentic GUI pages (except 5153 50W Blue for which the real amp does have a Depth control).

Fixed Drive block clicking when changing channels when bypassed.

FC: Views for Layout Link will now be restored properly after reboot.

FC: When entering the Master Layout menu via the switch-combo, the FC-6 will now always go to View 1.

FC: Per-Preset labels will no longer be displayed for unassigned switches.

=12.07=

Improved Compressor block. The RMS detector type has been improved resulting in smoother decay. The Auto Attack/Release algorithm has been improved resulting in less “chatter” when using low attack and/or release times. The Tube Compressor and Analog Compressor types now support RMS+Peak detector mode. A new knee shape algorithm in the Studio Compressor has been implemented resulting in a more musical tangential response like that of classic analog compressors.

Improved Downward Expander in Gate block. The RMS detector type has been improved resulting in smoother decay. Added Detector Type parameter which allows selecting between RMS (default) and Peak types.

Improved Multiband Compressor based on improvements to Compressor block. Added Auto Attack/Release mode.

Improved Astable LFO type so that adjustments to Beta, which can occur when changing channels, do not cause “baseline wander”.

FC: When navigating the editor or front panel, certain screens will no longer reset the value used by external modifiers for FC Pedals.

=12.06=

Improved performance of noise gate in Input block. Both the Classic and Intelligent types have been improved. The new Noise Reducer type reduces noise while preserving the attack of the note. It does this by using intelligent filtering to remove line noise and high frequency hiss will leaving the rest of the spectrum intact. Be sure to set the global Line Frequency to a value commensurate with the AC frequency in your country. Note that the Classic and Intelligent types can achieve complete silence while the Noise Reducer type can let some sound through as it is designed to be as transparent and unobtrusive as possible.

Improved Downward Expander type in the Gate block.

Fixed zipper noise when using an FC pedal to control input volume.

Fixed Delay Time not sticking for Ten Tap Delay.

Removed Bass, Mid and Treble controls from Capt Hook 1B amp model as this mode models the channel with the EQ Bypass engaged.

Fixed incorrect Dry Level in following Drive block models (was 100%, should be 0%): Shred Distortion M-Zone Distortion Ruckus (all versions)

Fixed High Slope controls in Cabinet block non-functional.

Added graphs to Setup -> I/O -> Pedal menu for pre/post-calibration visualization.

FC: Fix Tap Tempo function setting incorrect tempo when assigned to a stand-in switch.

FC: Fix Tuner not exiting when tapping a Stand-In Switch whose Hold function is Tuner.

FC: Fix UI of Stand-In Switches page not showing text representations of settings.

FC: Fix View Inc/Dec when accessing MLM on an FC-6 via Master Layout "Switch-Combo".

FC: Fix View Inc/Dec mini-LCD display when set to "Destination #".

FC: The main LCD will now display the correct first preset in the bank if the Global Setting for "Display Offset" is set to '1.'

FC: Stand-in switches will now perform their hold function based on the Hold Function Mode specified on the Config page of FC Controllers.

=12.04 / 12.05=

Updated the default value of P.A. Cathode Bias Resistor for some models. Existing presets are NOT changed. The new default values are listed here if you want to apply them to your presets:

* AC-20 DLX: 61%
* Boutique 1,2: 48%
* Blankenship Leeds: 58%
* Car Roamer: 56%
* Class-A 15W TB: 56%
* Class-A 30W: 46%
* Citrus A30: 56%
* Citrus Terrier: 60%
* Deluxe Tweed: 49%
* Div/13 CJ: 56%
* Div/13 FT37: 56%
* FAS Class-A: 56%
* Gibtone Scout: 76%
* Hot Kitty: 50%
* Matchbox D30: 59%
* Nuclear Tone: 78%
* Wrecker Liverpool: 59%

Improved pedal calibration.

Changed parameter value display to update if control is attached to modifier.

Added Triple Crest amp models based on a Mesa Triple Crown TC-100. Note that the actual amp’s “Tight” switch engages a built-in Tube Screamer circuit which can be replicated using a Drive block or the Amp block’s internal Boost feature.

Fixed a couple mistakes in Citrus Terrier amp model.

Fixed clicking when engaging/bypassing effects which change input impedance.

Fixed some parameters that should be modifiable (i.e. Chorus Rate, Rotary Rate, etc.) are not displayed as such.

Added modifier capability to ADSR Sustain Level.

=12.03=

Improved Amp modeling.

Added Low Cut to Dual Chorus type.

Improved Delay block Stack/Hold operation when using short delay times.

Added DynamiComp type to Compressor block. This is a pedal-style compressor with a faster attack behavior.

Fixed Input block UI.

Fixed Modifier graph when changing scenes remotely.

Fixed audio glitch when switching between two presets using Spring reverb.

Fixed fuzzy tone from some amp models if Sat Switch is engaged.

<Blockquote>”The sidechain filter changed in 12.03. Instead of a single bandpass it is now a highpass and a lowpass. With the single bandpass the lowcut and highcut frequencies were constrained from being greater/less than each other. gate to behave differently than it does now.“ [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-04.159140/post-1901681]</Blockquote>

=12.02=

Fixed UI unresponsive if modifier attached to Filter block Frequency control.

Fixed Filter block graph does not update if type changed from Axe-Edit.

=12.01=

Added Stack/Hold to Reverse, Dual and Sweep Delay types. All delay types now support Stack/Hold.

Added ALLPASS type to Filter block. This is a multi-stage “Phase Rotator” with feedback. With feedback set to zero it can be used to change the shape of transients. Using feedback causes constructive and destructive interference and can be used to create interesting tonalities. The Order can be set from 1 to 12 with progressively more phase rotation occurring. Attaching a modifier to the Frequency parameter can result in interesting chorus or wah effects. The red trace in the GUI is the phase response.

Improved preset/scene switching.

Fixed artifacts in Wah block when Control knob is attached to a high-speed source, i.e. LFO with high rate.

Fixed some values not displaying correctly (i.e. High Crossover Freq. in Multiband Compressor).

Fixed some parameters being unintentionally reset when editing a block.

=12.00=

Added “2x12 Godzilla” Speaker Impedance Curve based on a Zilla Fatboy.

Complete overhaul of the Flanger block. See Flanger page.

Complete overhaul of the Phaser block. See Phaser page.

Added separate Filter Slope controls for the Cabinet block. The range of the slopes has been extended to include 18 and 24 dB/octave. Existing presets will be automatically updated to the correct values based on the previous Filter Slope value.

Added separate Low Cut Slope control for Delay block. Updated models accordingly.

Added “FAS Express” amp model based on hypothetical modifications to a Trainwreck Express.

Improved messaging system so that changing presets while Axe-Edit is running does not cause audio dropout (requires Axe-Edit version 1.4.00 or later).

Improved Scene switching speed.

Added LFO Quantize to Filter, Flanger and Phaser blocks.

Added Triggering to Tremolo block. When the Tremolo is triggered the Tremolo will engage and the LFO phase will start at the Start Phase value. This allows easily synchronizing the Tremolo to your playing. Set to “OFF” to defeat the trigger.

Added Optical Tremolo type to Tremolo block.

Addded “Astable” type to LFOs. This simulates an astable Op-amp Multivibrator as is commonly found in effect pedals. “Beta” controls the shape of the LFO. High values approach a square wave while low values approach a triangle wave.

Added Stack/Hold parameter to Plex Delay and Plex Verb types in the Plex block. When set to STACK incoming audio is stacked on existing audio and held. When set to HOLD existing audio is held.

Changed Hold parameter in Delay block to Stack/Hold (see above).

Changed Hold parameter in Reverb block to Stack/Hold (see above).

Added “OD 250” Drive model based on a DOD Overdrive 250 (gray version).

Added adjustable slope to Parametric EQ block for outer bands when type is set to BLOCKING.

Added LFO monitors to Control block.

Drive block EQ now supports placement pre- or post-distortion.

Added “Stereo Mind Guy” delay type.

Added ULTRA-HIGH quality mode to Reverb block. This mode increases the modulation at the expense of a slight increase in CPU usage.

Fixed loss of precision in certain amp models (i.e. Plexi 50W Normal) when Input Drive is set very low.

Fixed Align tab in Cabinet block not displaying traces properly after changing channels/scenes from Axe- Edit.

=11.01=

Updated Speaker Impedance Curves for 2x12 Jazz 120, 4x10 Brit JM45 and 4x12 Hipower. Also added the following new curves: 2x12 Bassbuster (based on a Fender Bass Breaker), 1x12 Tweed Alnico Blue (based on a Fender Deluxe with Celestion Blue), 4x12 PVH 6160 (based on a Peavey 5150 w/ Sheffields), 4x12 Euro (based on a Bogner standard), 2x12 Recto (based on a Mesa Rectifier)

Added “Matchbox D-30 EF86” amp model. While the real amp has a six-position Tone switch, the model has a continuously variable tone control. Note that the Tone control is mapped to the Bass control in Ideal mode as the Tone switch is essentially a bass cut control.

=11.00=

Amp block now uses new high-order speaker impedance modeling. 52 speaker impedance models (and two LB-2 models) are included and can be selected using the Speaker Impedance Curve parameter (on the Advanced page). Selecting an amp model will load an appropriate default Speaker Impedance Curve for that amp model. The Cabinet Resonance parameter can be used to adjust the amount of cabinet resonance in the impedance curve. NOTE: The 2x12 Bassguy, 2x12 Jazz 120, 4x10 Brit JM45 and 4x12 Hipower data is incomplete and will be updated in a future release.

Setting Global “Update Pre-11.x Presets Spkr Imp Upon Load" parameter to YES will automatically update the Speaker Impedance Curve for the Amp blocks upon preset recall to use an appropriate Speaker Impedance Curve for that amp model. Setting the parameter to NO will leave existing presets unaffected. NOTE: Setting this to YES will also cause the EDITED LED to light indicating the preset has been modified.

Fixed Recto1/2 models default Negative Feedback and Power Tube Bias values slightly too low.

Fixed loss of precision in Drive block Tone control for some models (Rat, Timothy, et. al.) causing low frequency build-up over time.

=10.02=

Fixed popping noise can occur when switching between certain amp models. This also results in faster, smoother preset, scene and channel changes.

Fixed wrong Basic tab of Drive block when Ruckus LED/Si type selected.

Added Wrecker Liverpool Bright amp model. This models the amp with the three-position Bright switch in the brightest position.

=10.01=

Fixed divide-by-zero can happen in Drive block when using certain combinations of different diode types and a very strong input signal or when switching between different types.

Fixed can’t access Drive block Advanced GUI page for Ruckus LED/Si type.

Changed Drive block Slew Limit to Slew Rate and updated default value of the models. Existing presets will be updated to the new default value upon recall. Note that the parameter now controls the slew rate and lower values equal less high frequency response at high amplitudes and vice-versa (the action is reversed from the previous firmware versions).

Added Wrecker Express Bright amp model. This models the amp with the three-position Bright switch in the down position.

=10.0=

Added Downtune control to Tuner. The Downtune control allows for simplified tuning when tuning down one to four semitones. The Tuner display will read the “natural” name of the note, i.e. if tuning down one semitone an Eb will read E. In addition any blocks that utilize pitch information will also be transposed accordingly.

Added Display Mode control to Tuner. This control allows selecting between all flats, all sharps or a mixture of sharps/flats for the displayed note name.

New power amp modeling algorithm. This algorithm improves the plate impedance accuracy substantially. This yields tighter bass, crunchier midrange and “chimier” highs.

Due to the changes in the power amp modeling algorithm the Power Tube Hardness parameter now behaves differently. Selecting a Power Tube Type loads the “knee voltage” for the power tubes and this voltage can be adjusted up or down using Power Tube Hardness. Higher values yield a lower knee voltage and more abrupt clipping and vice-versa. Existing presets will have Power Tube Hardness reset to 5.0 upon recall.

The range of the Transformer Match control has been reduced to 0.5 to 2.0. Existing presets will have this value reset to 1.0.

The Ideal Tetrode and Ideal Pentode power tube models are no longer applicable and have been replaced with 5881 and 6L6GB models, respectively.

The PI Bias Excursion values have been updated for some amp models. Existing presets will automatically be updated to the new default values. If you typically alter this parameter you should audition your presets.

The Amp block Dynamic Impedance parameter is no longer applicable and has been removed.

Added KT77 power tube type.

Improved Drive block. New diode modeling algorithm improves clipping accuracy especially for diodes with higher saturation currents, i.e. 1N270 and other germanium types.

Added D9E and D18 diode models to Drive block. These are Soviet germanium diodes valued for their smooth distortion characteristics.

Added “Ruckus LED/Si” type to Drive block. This model is based on a Suhr Riot with the toggle switch set to select the hybrid LED/Silicon Diode position.

Added “5 Band Mark” type to Graphic EQ block.

Fixed exported Tone Matches may, in rare cases, not sound the same as the Tone Match.

Fixed long delay times (over 1.5 seconds) in Plex Shift can cause artifacts.

=9.01=

Fixed Amp block input drive network instability in rare cases when switching between certain presets.

Fixed some amp models can become unstable for certain combinations of Negative Feedback and high values of Speaker Impedance and/or Transformer Match.

Added “Gain Enhancer” mode to Amp block Output Compressor. This mode can be used to simulate the acoustic reinforcement of a loud amp coupling into the guitar and enhancing the output signal.

=9.0=

New power amp modeling algorithm. This new algorithm now also separates the transformer matching from the speaker impedance. A new parameter, Speaker Impedance, allows adjusting the relative impedance of the virtual speaker. For example, to simulate connecting a 16-ohm speaker to an 8-ohm output set Speaker Impedance to 2.0. Transformer Matching, on the other hand, changes the impedance ratio of the virtual output transformer.

To support the new power amp algorithm the internal transformer matching values and negative feedback values have been updated. The new negative feedback values will load when selecting an existing preset. If you typically adjust Negative Feedback when creating a preset be sure to audition your presets as the parameter value will be reset to the default value upon preset load.

Fixed Amp block Output EQ wrong frequencies if EQ Location set to “Input”.

Fixed Amp block “Hi-Cut” calculation for amps without negative feedback. This affects the following models:

* All AC-20 models
* All Class-A 15W and 30W models
* Citrus Terrier
* Boutique 1 and 2
* FAS Class A
* Hot Kitty
* Matchbox D-30
* Mr. Z MZ-8 and MZ-38
* Ruby Rocket and Ruby Rocket Bright
* Supremo Trem
* Wrecker Rocket

Fixed incorrect default P.A. Cathode Resistance value for Citrus Terrier model (correct value is 96%) and Class-A 15W model (correct value is 83%).

=8.0=

Improved amp modeling.

Added Swap Scene function to Layout->Tools.

Fixed Plex block Shimmer Verb causing NaN if Reverb Size set to 0%.

Fixed Tone Match block erroneous results on preset recall due to uninitialized data.

Fixed sluggish Axe-Edit behavior after boot on high CPU presets.

Fixed Rotary block Input Select not working correctly.

Fixed Compressor block sidechain filter not working if gain set to 0.0 dB.

=7.01=

Firmware image now uses compressed initialization. This results in a smaller file size and faster firmware updates.

Added Input Select to Megatap Delay, Multitap Delay, Plex Delay, Reverb and Rotary blocks.

Fixed Input Impedance not set correctly if an active effect is in a different row and prior column than the effect that should be controlling the impedance.

FC: Fixed stand-in switches not activating the down half of their assigned function.

=7.0=

Improved power amp modeling. New algorithm accounts for variation in load voltage as a function of transformer turns ratio. I.e. reducing the Transformer Matching will reduce the output level and vice- versa.

Fixed low output level for Shred Distortion Drive model.

FC: Fixed tap function executing on hold when "Hold Execute" is set to "Switch Up". FC: Fixed switch executing from wrong layout after a stand-in switch is used.

FC: Fixed MLM functionality when cloning mixed units (FC-12's and FC-6's).

FC: Added FC-6/FC-12 compatibility mode. When enabled, FC-6(s) will use buttons 1, 2, 3 for the bottom row and buttons 7, 8, 9 for the top row. Accessible from HOME->SETUP->FC Controllers->Config Page, FC-6/FC-12 Compatibility Mode. It is disabled by default.

FC: When "Reveal Holds" is active the hold function states will be displayed (with default ring colors only) and button presses will execute the hold functions.

FC: Fixed hold functions firing on the MLM hold switch (switch 3 on FC-6 and switch 6 on FC-12) preventing MLM mode from executing.

=6.04=

Reduced background task priority on high CPU presets to improve client (i.e. Axe-Edit) performance.

Added “CC Boost” type to Amp block.

Improved CPU usage.

Optimized LCD graphics for better response.

Changed FC tuner note names to match main tuner (i.e. Eb instead of D#).

Added Solo feature to Parametric EQ block. When a band is soloed the frequency range for that band is isolated allowing the user to fine-tune the band.

Fixed output level of PI Fuzz model too low.

Fixed Modifier auto-engage not working when Auto-Engage is set to SLOW POSITION and the Update Rate is set to FAST.

Fixed Supremo Trem model missing Tone control in Authentic mode. Note: the Tone control is mapped to High Cut in Ideal mode.

Fixed FC and Axe-Edit not displaying tempo correctly if preset using global tempo. FC: Fixed Layout Link not executing if no function is assigned to the switch.

FC: Added Mode parameter to Utility/Reveal Hold for Momentary/Toggle.

FC: Added Hold Function Execute Mode: TIMEOUT or SWITCH UP. "TIMEOUT" is same as the previous behavior. When set to "SWITCH UP", the hold function executes when you release the held footswitch, allowing precise musical timing.

FC: Fixed Per-Preset/Placeholder #24 not working.

=6.03=

Fixed long preset load time if preset using Filter block with Frequency parameter connected to modifier.

=6.02=

Added LFO to Filter block. When enabled, the LFO will modulate the frequency of the filter between the Frequency and the Mod. Frequency. The local LFO simplifies modulated filtering and frees up the global LFOs for other tasks.

Added adjustable filter to Plex block wet signal. Filter can be any of the standard types (all types except comb filter types). Frequency, Q and Gain are modifiable.

Added Shimmer Verb type to Plex block.

The Mode parameter in the IR Player block has been replaced by a Length parameter.

Changed Home page behavior so that menu stays on selected tab when returning. Pressing HOME while on the Home page resets to first tab.

FC: Improved communication reliability when using very long cables (requires FC firmware version 1.08).

FC: Fix preset tempo being used when global is selected .

FC: Add Layout Inc/Dec function.

=6.01=

Fixed memory allocation error causing boot irregularities.

=6.00=

Firmware 6.00 introduces the PERFORM tabs found on the HOME screen of the Axe-Fx III. There are two PERFORM tabs: Per-Preset and Global. The PERFORM tabs can be configured with up to 10 user-selected controls from any of the blocks found in the current preset (including CONTROLLERS and GLOBAL). Configuration of the PERFORM tabs is done via Axe-Edit III. Allowable controls include rotary knobs, push-buttons, drop-downs, and toggle controls (e.g., on/off controls).

''The "Perform-PP" controls are stored per-preset. Adding or removing a control from "Perform- PP" will change the EDIT state of the preset.''

''The "Perform-Gbl" controls are stored in the Global Settings. Adding or removing a control from "Perform-Gbl" is automatically saved to the Global Settings.''

''Performance controls are added via the editor from a block's parameter view. The editor's selected parameter control is assigned to the desired Performance tab through a popup menu.

''The editor's Perform view is accessed via the "Perform" button or the Tools / Performance menu. From this view, Per-Preset Performance controls can be imported and/or exported using the "Block Library" control. Additionally, the view's "Per-Preset" and "Global" tabs allow label editing for controls already assigned to the "Perfrom-PP" and "Perform-Gbl" tabs.''

Changed Cabinet, IR Player and Tone Match block IR windowing so that window length is proportional to IR length (rather than a constant window length).

Doubled length of IR Capture Utility sweep. This improves SNR in challenging environments, i.e. a large, noisy room when capturing “far-field” IRs. The time between sweeps has also been increased to allow the room reverberation to decay sufficiently before starting the next sweep.

Improved Amp block power amp modeling.

Added five “Manual” controllers to Controllers menu. These can be used as modifiers for real-time manipulation of parameters from the front panel.

Combined LFO 1 and LFO 2 menus into a single menu.

Fixed Ring Mod block left/right slightly unbalanced.

Fixed Looper allows playback even if no loop exists causing noise.

FC: Further fixes for startup timing issues.

FC: Fixed Inc/Dec functions' upper limits defaulting to zero.

FC: Fixed learning of FC external pedals and switches in MIDI/Remote.

FC: Fixed external switch polarity not showing correctly on the FC Controllers Remote page.

=5.08=

Added Low Cut and High Cut to individual IRs in Cabinet block. Filter slopes are also selectable from 6 to 24 dB/oct.

Added IR Length parameter to individual IRs in Cabinet block. Shorter lengths can be used to remove room reflections and/or decrease CPU usage.

Changed Pitch block so that pitch detection is performed even when block is bypassed. This allows using the Learn function while the block is in bypass.

Fixed sometimes unit will hang at boot if an FC-12 running firmware version 1.06 or later is connected.

Fixed pop when switching from Hipower amp models to certain other amp models.

FC: Fix Layout Link not working when in MLM mode.

FC: Fix EZ Page changing values of Switch 1 even if no switch has been selected .

FC: Fix inc/dec wrap operation.

=5.07=

Improved Preset/Scene/Channel switching time.

Fixed wrong default Cathode Follower Compression values for Brit JVM and JS410 amp models.

Fixed AES/SPDIF input shifted by one bit causing clipping at -6 dBFS.

FC: Added support for stand-in switches (assign external switches to perform a function assigned to an FC switch).

FC: Support for FC firmware 1.06 (switch behavior and polarity)

FC: Added shortcut keys to/from Per-Preset and Global

FC: Added warning on switch page if the switch is overridden in the current preset

FC: Fix per-preset overrides not working on MLM page 2 for the FC-6

FC: Fix layout link and MLM interaction (switch 3 for the FC-6 and switch 6 for the FC-12)

FC: Fix layout link for per preset switches

=5.06=

Added USA JP IIC+ Green amp model (channel 1).

Fixed wrong internal transformer matching value for Friedman Small Box model.

Fixed popping when switching between channels/scenes/patches with very different block levels.

Fixed incorrect error message when updating USB firmware via Fractal-Bot.

Fixed Upper Limit on functions in the Bank category reverting to '51' on restart (regardless of bank size).

Fixed FC layout names getting clobbered if knob A is used to Nav while editing.

Fixed loading defaults squashing the version (and other dummy params) on the devices page.

Display Effect name for Effect functions on the Overrides page of Per-Preset FC Settings.

Configurable timeout for the notifications on the FC main LCD.

Updated FC function Effect->Channel Select to turn off the LED ring if the effect is bypased and Smart Bypass is enabled.

Added TEST ON and TEST OFF to CS MIDI for the FC.

=5.05=

Fixed missing menu for USA JP IIC+ Yellow amp model when using authentic controls.

=5.04=

Added USA JP IIC+ Yellow amp model (channel 2).

NOTE: To emulate the “Shred” mode turn the High Treble control to approximately 3-4 dB (or adjust to taste, you are not limited by a single switch).

Fixed corruption in FC Remote menu.

=5.03=

Added USA JP IIC+ Red amp model (channel 3). NOTE: To emulate the “Shred” mode turn the High Treble control to approximately 3-4 dB (or adjust to taste, you are not limited by a single switch).

Fixed hold functions on page two of the Master Layout Menu for the FC-6.

Fixed FC Bank -> Inc/Dec function's upper limit from resetting to the maximum bank number on reboot or bank size change.

Fixed copy/paste of FC Layouts not setting Layout Link.

Fixed FC Layout Link for hold functions not surviving a reboot.

Fixed wet data muting during channel change in Multitap block.

=5.02=

Fixed presets created with firmware prior to 3.00 defaulting Amp block EQ Off/On parameter to Off instead of On.

=5.01=

Fixed presets created with firmware prior to 3.00 not loading various parameters correctly. These parameters are primarily the Spread parameters in the Chorus, Flanger, Rotary and Reverb blocks, among others.

=5.00=

Completely new Amp block cathode follower algorithm yielding more accurate results. The “Ideal” cathode follower type is no longer supported as it is incompatible and has been removed from the GUI. The Cathode Follower Time and Ratio parameters have also been removed as they are no longer applicable. A “Grid Clipping” parameter has been added which allows the user to adjust the grid clipping in the cathode follower. Lower values reflect the softer response of classic British and American tubes like Mullard, Sylvania and RCA. Higher values simulate the response of modern Chinese and Russian tubes with more abrupt clipping.

Updated various Amp block parameters related to new cathode follower algorithm. Existing presets are automatically updated to the new values.

Added AES/SPDIF Input Level control. This is located in the I/O->USB/AES menu. NOTE: this parameter will default to -40 dB after installation of the firmware. Be sure to adjust to the desired level if using the AES or SPDIF inputs.

Added Treble Booster and Mid Booster boost types to Amp block.

Improved Scene/Channel change logic. Only the wet data is muted when changing scenes and channels now leaving the dry data intact which results in smoother transitions.

Changed Control block Envelope Follower behavior so that when the signal exceeds the threshold the control value starts at zero rather than jumping to the threshold value.

Fixed wrong bass pot taper in Friedman Small Box model.

Fix FC per-preset corruption with some presets.

NOTE: Due to the new algorithms several amp block parameters are reset to default values when loading old presets. Included in these parameters is Preamp Bias Excursion. If you had altered this parameter in a preset note that it will be reset and you may want to readjust it.

<blockquote>"All models have been improved as there was a change to the triode algorithms as well." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-00-beta.148607/page-3#post-1759653]</blockquote>

=4.03=

Fixed Div/13 CJ 11 amp model muted when two Amp blocks used.

=4.02=

Fixed issue with certain amp models, i.e. Legato 100, exhibiting excessive blocking distortion.

Fixed loss of communications with FC-X foot controllers after being left on for very long periods of time, i.e. overnight.

Various fixes and improvement for FC-X controllers.

=4.01=

Fixed triode modeling algorithm for amp models with “cold clipping” stages, i.e. Recto, SLO, etc.

=4.00=

Improved Amp block preamp tube modeling.

Improved Amp block cathode follower grid modeling.

Improved power amp modeling for “Class-A” type amp models.

Added modifier capability to Decay Time, Level 1-8 and Pan 1-8 controls in Plex Delay block.

Added Presence Shift control to Amp block Tone page for the appropriate models when using Authentic controls.

Added SV Bass 1 amp model. This is the original SV Bass model prior to the change in 2.05. The new SV Bass model added at 2.05 has been renamed SV Bass 2.

Added FAS Skull Crusher amp model. The nastiest, most brutal amp model to ever escape from the seventh circle.

Reworked PI Fuzz model based on older “Triangle” version reference. A soft-reset of the model is required to load the new parameter values. Note that duplicating the behavior of a fuzz pedal requires that the pedal be the first non-bypassed block following the Input 1 block and the input block impedance must be set to Auto since fuzz pedals load down the guitar’s pickups.

Added “Unlink All Blocks From Global” function to Layout->Tools menu. This unlinks all blocks from any global blocks to which they may be linked.

Expanded the names of the “USA” models to more accurately indicate the switch settings.

Fixed Tone page for Plexi 100W 1970 not showing Normal Drive control.

Fixed incorrect capacitor value and wrong default Low Cut value in BB Pre Drive model.

Fixed wrong default Low Cut value in Eternal Love and Esoteric ACB Drive models.

Fixed Output EQ in Amp block not being redrawn when changing channels and number of bands is different.

Fixed wrong triode plate frequency in Herbie CH3 model.

Fixed wrong mid and treble tapers in all Herbie models. Existing presets should be auditioned.

=3.02=

Improved Drive block. WARNING!!! The sound of some of the drive models may have changed significantly.

* Drive models based on op-amp and diode clipping topologies have been completely overhauled.
* For many types there is now a “Dry Gain” control. This parameter controls the amount of “dry” signal mixed with the “wet” (distorted) signal. For a Tube Screamer-based model this will default to 100% due to the topology. For other types this will default to 0. Values up to 200% are allowed. Note that the dry data is added before any tone controls and therefore is not exactly equivalent to a mix but rather replicates the behavior of analog circuits.
* Drive types based on op-amp and diode clipping circuits now allow control over the type and quantity of diodes in the positive and negative polarity. For example, the user can select (2) 1N34A diodes for positive signal polarity and (1) red LED for negative. Experiment with the various diode types and quantities to obtain new and unique sounds.
* The Basic GUI page now reflects only the controls found on the actual pedal. In cases where the actual pedal does not have any tone controls a simple Tone control is included for convenience.
* Added several new types.

Added “All” to Tuner Input Source selection. This sums all inputs.

Added Global "Tone Control Display" parameter. When set to Authentic (default) only those controls present on the actual amp are displayed. When set to Ideal all tone controls are displayed. Also, when set to Authentic the Bass, Mid and Treble controls are reset to default values when changing models to ensure accuracy for models that may not have these controls.

Fixed Tone Match block not updating correctly between preset changes if different Mode used.

Fixed loss of low frequency resolution for Tone Match block when set to Off-Line mode.

=3.01=

Fixed Graphic EQ pages not responding to navigation buttons.

Fixed FC load defaults correctly sets bank size before configuring switches.

Fixed FC use "Scene X" on main LCD if scene name is blank.

Fixed load FC-12 defaults won't switch first FC to layout 7.

Fixed FC scene name not updating if character(s) removed from end.

=3.00=

Improved amp modeling.

Improved speaker compliance algorithm.

Improved algorithms for modulation effects.

Improved Tone Match block graphs.

Improved Reverb block.

Added “EQ Off / On” control to Amp block. This modifiable parameter turns the graphic EQ on and off.

Added Plex Verb type to Plex block. While the Reverb block is designed for authentic, natural-sounding reverbs, the Plex Verb type is designed for large, ethereal reverb sounds. This type is also simple to use with no time, tempo, level or pan parameters required. For best results turn the Diffusion Mix up when using this type.

Added Spread and Pre-Delay controls to Plex block.

Increased the range of the Low Freq Time and High Freq Time in the Reverb block. This allows for creative reverb sounds. Several new reverb types have been added to illustrate these effects.

The Chorus, Flanger, Plex, Reverb and Rotary blocks now supports Spread values from -200% to 200%. Values beyond +/-100% increase the apparent image beyond the stereo field. The action of the spread control has also been improved so that the apparent volume remains constant vs. spread value.

Fixed IR Capture utility sometimes not working in Cab+DI mode.

Fixed slow response in IR Capture configuration menu when changing bank/slot.

Fixed Cabinet block graphs not showing traces for non-UltraRes IRs.

Fixed Input Source for Pitch Follower not exposed.

Fixed FC-X custom Mini-Display Label for Effect, Chan Select.

=2.05=

NOTE: The firmware now displays diagnostics during the first phase of the boot routine. [http://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-2-05.146395]

Added Threshold parameter for all types in Compressor block.

Change Drive block behavior so that when changing the Drive Type the graphic EQ is reset.

Reworked SV Bass amp model. Model is now based on a 1970 Ampeg SVT with 6550 power tubes and the midrange switch in position 3.

Cabinet block now automatically corrects the polarity of IRs that are inverted, i.e. captured from the back of a cabinet.

Added floor reflection modeling to Cabinet block. The intensity of the floor reflections can be adjusted with the new “Floor Reflections” parameter. Floor reflections play a large role in “amp in the room” sound. If the amp is on a carpet the floor reflections are minimal. If the amp is on a wood or other hard surface the floor reflections are significant. Existing presets will initialize this value to 0% so as to not change the sound. The default value is 50%. Note that negative values, while not realistic, are supported which inverts the reflection.

Added Diffusion to the Cabinet block room modeling.

Improved IR Capture Utility. User can now select between conventional deconvolution and reverse filter processing. In a high-noise environment the reverse filter technique can provide better results. In low-noise environments the conventional technique can provide slightly better bandwidth and magnitude accuracy. Note that the prior firmware used the reverse filter technique.

Added Processing parameter to IR Capture Utility. This selects between “Minimum-Phase” which transforms the IR into a minimum-phase version, “Auto-Trim” which removes the leading silence, and “None” which applies no processing at all. Note: prior firmware always used minimum-phase processing.

Added Delay Compensation to IR Capture Utility. This allows compensating for time-of-flight delay when capturing IRs. For example when capturing far-field IRs there may be significant time delay due to the distance of the mic from the speaker. This can reduce the precision of the measurement if the delay is excessive. To use the compensation configure the graph to the Time display. Do a test sweep and note the waveform delay. Dial in the desired amount of compensation delay and repeat as necessary. Note that the speed of sound is roughly 1 ft/ms so a mic that is 10 ft from the speaker would incur roughly 10 ms of delay. Note that IR Capture Utility will automatically compensate for delays up to approximately 20 ms (1K samples). Correction is only required for delays greater than 20 ms.

Added alignment graph to Cabinet block showing a zoomed time series of the IRs allowing visual adjustment of the mic distance. When using IRs that have not been minimum-phase processed this facilitates aligning the IRs.

Added Volume Increment/Decrement CCs for Output 2.

Added “Analog Compressor” to Compressor block. This compressor has a natural soft-knee response and captures the vibe of the classic compressors of the 70’s and 80’s.

Added Mix control to Multiband Compressor block.

Added Knee Type control to Multiband Compressor block.

Corrected the VU meters in the Output block to compensate for the “unity gain” nature of Outputs 3 and 4. Note that the Output block meters are BEFORE the Level controls (pre-fader) on the front panel and are therefore unaffected by the Level controls. The meters indicate the internal signal level relative to full-scale (dBFS).

Renamed Dumble-style amp models with PAB on accordingly.

Changed Volume Inc/Dec behavior so that muting is not performed.

Various changes and fixes for FC-6/12 foot controllers. Note: this firmware, or a later version, should be installed for proper operation of the foot controllers.

Fixed clicking noise in Pitch block at certain values of shift and tracking.

Fixed Cabinet block LF Damping and HF Damping parameters sometimes not working.

Fixed output gain of Compressor block when using either of the Pedal types dependent upon the Ratio control of the Studio type.

Fixed crash when adjusting Amp block Screen Q rapidly.

=2.04=

Added “Tube Compressor” type to Compressor block. This type is based on classic tube compressors like the Altec Lansing 436C. Since this type uses “variable mu” processing it may add subtle, and possibly desirable, distortion to the audio.

Added “FF Comb” and “FB Comb” types to Filter block. FF Comb is a feed-forward comb filter and FB Comb is a feedback comb filter. Delay Time controls the order of the comb filters, higher values result in more closely spaced notches and vice-versa. Depth controls the intensity of the filter, higher values result in deeper notches/peaks and vice-versa.

Added Comb Filter Type parameter to Multidelay block. The names of the parameters in the block have been changed from “Resonator” to “Comb Filter”.

Added clock sync checking in I/O menu. If the user selects one of the digital input sources (SPDIF or AES) as the clock source and there is no valid input the menu will indicate no clock source.

Changed Cabinet block Room Size display to meters for clarity.

Fixed Cabinet block does not update if a newly captured IR is saved to an IR location in use.

Fixed Cabinet block “AIR” mixing is done before level normalization.

Fixed USB 5/6 Input Level affects SPDIF/AES input level.

Fixed setting size very low on room types in Reverb block can cause crash.

=2.03=

Changed Looper behavior so that Play indicator only lights during recording when overdubbing.

Added Looper Crossfade parameter. When set to ON the loop fades out/in at the end/start of the loop.

Improved Cabinet block room emulation. New algorithm provides denser and more immersive reflections.

Added Room Shape parameter to Cabinet block which selects between and hall and room shape.

Added “Bias Trem” type to Tremolo block. This uses a tube emulation algorithm to replicate the bias tremolo used in vintage tube amps.

Added “Harmonic Trem” type to Tremolo block. This recreates the famous sound of the tremolo circuit in the old “Brownface” amplifiers. This effect splits the spectrum and applies modulation to the two frequency bands. The Crossover Slope parameter selects the filter order for the crossover. The original circuit used a 6 dB/octave crossover. Higher slopes can give a more intense effect. The crossover frequency can be changed with the Crossover Frequency parameter. Note: unlike most implementations the Axe-Fx III version is full stereo and can be used before or after the Amp block without losing stereo separation. Additionally the effect supports LFO phase for the left/right which can be used to achieve unique sounds. Furthermore the effect supports LFO types other than Sine for even more unique sounds.

Note: both the Bias Trem and Harmonic Trem use nonlinear processing techniques and, as such, may add distortion to the audio signal just as their tube-based counterparts would.

Added “Grinder” boost type based on a Fortin Grind to the Amp block.

Added USB Input Level controls. These are located in Setup->I/O->USB. Note that these values will default to -40 dB after the firmware upgrade.

Changed background tasks to run dynamically based on available processing time. This prevents sluggish behavior of Axe-Edit and MIDI controllers immediately after startup.

Fixed IR capture export not working consistently causing issues with Cab-Lab 3.

Fixed incompatibility with Live mode in Cab-Lab 3 when using Axe-Fx III as the audio interface.

Fixed Reverb block NaN if setting size extremely low and turning modulation depth way up.

=2.02=

Fixed issue in phase inverter modeling causing excessive bias excursion in some amp models.

Fixed Reverb block causing crash if setting size to less than 6.0 for certain types.

Fixed FC GUI corruption when changing presets via foot controller.

Various other fixes and enhancements for FC-X controllers.

=2.01=

Added “Filter Type” to Compressor Side-chain.

Added “Auto-Swell” type to Volume block. This simulates “pinky swells” using the guitar volume knob. Threshold sets the input power to start the volume swell. When the input power drops below the threshold the swell circuit is reset and the volume drops to zero. Attack sets the rate at which the volume increases.

Increased size of VU meters and added gain readout in Layout GUI.

Added ability to select the source of USB Outputs 7,8 (to computer). Inputs 2-4 can be assigned to USB 7,8.

Improved Amp block phase inverter modeling.

Fixed minor error in Amp block voltage to speaker displacement transfer function causing more parameter shift than expected for a given Speaker Compliance setting.

=2.0=

Improved Amp block speaker dynamic parameter modeling. The new Speaker Compliance parameter controls the nonlinear behavior of the virtual speaker. Existing presets will load with this parameter at 0.0 and will be unchanged tonally from the previous firmware (IOW your presets will not be altered). Selecting a new amp model or resetting the block will set the value to 50% which is a typical value for guitar speakers.

Improved Amp block cathode follower modeling.

Improved Looper cross-fade at start/end of loop.

Improved stability and latency of Pitch block.

Improved anti-aliasing performance of Pitch block.

Added Temperament parameter to Pitch block. When set to “Just”, pitch shifting uses just temperament with ratios defined by the harmonic overtone series. When set to the default value of “Equal”, equal temperament tuning is used. Just temperament can be used to give a “sweeter” harmony, especially when followed by distortion.

Added “Virtual Capo” type to Pitch block. This is a simple one-voice pitch shift that is intended for drop-tuning and virtual capo use and is easy to configure and use.

Changed Pitch block behavior so that when selecting Whammy or Virtual Capo types the Mix is automatically set to 100%, otherwise 50%.

Improved algorithms in Multitap block.

Added two options to the Filter Order in the Cabinet block. “L: 6, H: 12” sets the filter slope to 6 dB/octave for the low cut and 12 dB/octave for the high cut. “L: 12, H: 6” sets the filter slope to 12 dB/octave for the low cut and 6 dB/octave for the high cut.

Changed Looper meter, CPU meter and Layout VU meter colors to cyan so that thresholds are visible to those with red-green colorblindness.

Fixed Looper not playing when pressing Once if Trim Start is nonzero.

Fixed MIDI running status ignored if active sense messages received between status messages.

Fixed Master Resonator Time not working in Multitap Delay.

Fixed diffusion not working on delay lines 2-4 in certain types in Multitap Delay.

Various changes and fixes for FC-X controllers.

Minor tweaks and improvements to the GUI.

=1.19=

Public beta versions only.

=1.18=

Fixed meters on Home->Meters sometimes getting stuck.

Fixed MIDI-Over-USB hanging when receiving certain SysEx messages intended for other products. This occurs with some DAW software (i.e. Logic) at startup causing subsequent SysEx commands to be ignored rendering Axe-Edit non-responsive.

Fixed certain 3rd-party MIDI SysEx messages not processed properly when SysEx messages are also being received via USB (i.e. changing a block bypass state or channel via a MIDI foot controller while also using Axe-Edit).

Fixed adjustments to global Noisegate Offset do not take effect until editing Input block.

Fixed booting to preset with two amp blocks does not correctly initialize.

Fixed block channel change so that muting does not occur if block is bypassed.

Fixed IR Player block allows linking to Global Blocks.

Changed range of Attack and Release parameters in Input block gate to more suitable values.

=1.17=

Fixed NaN when selecting “USA” amp types.

=1.16=

Improved Multiband Compressor block so that mid-band gain is automatically compensated for crossover response.

Added Frequency Range parameters to Multiband Compressor block. This selects between Low and High frequency ranges yielding more flexible crossover frequencies.

Added Crossover Slope parameter to Multiband Compressor block. Choices are 12 and 24 dB/octave.

Added FAS Boost to Amp block input boost types.

Added Output Mode to Amp block. The default value, FRFR, is the classic mode and designed for use with monitors or recording. The SS PA + Cab mode is intended for use with a solid-state power amp and conventional guitar cab. In this mode speaker compression modeling behaves differently relying on the speaker for compression while still simulating the interaction with the power amp. NOTE: this mode is not intended for use with current drive power amps, i.e. tube power amps, Class-D current feedback amps (Quilter Tone Block), etc. NOTE: this mode CAN be used with FRFR monitors in high volume applications where the monitor’s speakers are compressing thereby achieving a more dynamic response.

Added 10-band, 2/3 octave types to Graphic EQ block. These types center the filter frequencies on a narrower range best suited to finely sculpting guitar tones.

Added 10-band, 2/3 octave graphic equalizer to Drive block. The EQ can be enabled/disabled via the Graphic EQ parameter which is also modifiable.

Added 8-band, 2/3 octave graphic equalizer to Wah block. The EQ can be enabled/disabled via the EQ parameter which is also modifiable.

Fixed moving cabs with Axe-Edit causes corrupted empty slots.

Fixed Looper status not reported correctly via MIDI.

Fixed Looper doesn’t always start if threshold is off.

Fixed metronome turning on when executing Reset System Parameters.

Various fixes and changes for FC series foot controllers.

=1.15=

Added (2) IR Player blocks. These are simple versions of the Cabinet block that can be used to process IRs for various purposes such as applying Tone Matches separate from the Tone Match block. For example, an IR Player block can be used to apply a Tone Match of a guitar at the beginning of a chain leaving the Tone Match block available for amp matching.

Added Output 1 Volume Increment and Output 1 Volume Decrement CC assignments. When the CC assigned to Volume Increment/Decrement is received the scene volume for Output 1 is incremented or decremented by 1 dB and the preset automatically saved.

Added Metronome function. To enable the metronome press the Tempo button and adjust the level for the desired output(s). Note: the metronome levels persist across presets and are reset to OFF at power on.

Improved Looper block:
# Added Record Threshold parameter. When set to a value greater than -80 dB recording will not start until the input signal exceeds the set value. The Record icon will blink when the Looper is armed for recording and will turn solid when recording starts. The meter at the bottom of the page can be used to help set the Threshold. Use the soft knob or main Value knob to adjust the threshold value (or use the Record Threshold parameter on the Config page).
# Added Trim Start and Trim End parameters to the Looper block. These parameters can be used to adjust the start and end points of the loop. The graph on the Control page provides visualization of the loop and the start/end points.
# Added Quantize parameter. When set to ON the loop length is quantized to the nearest beat.
# Added Record 2nd Press parameter. Choices are Overdub – existing behavior, second press of Record ends loop and enters overdub; Play – second press of Record ends loop and enters play; Stop – second press of Record ends loop.
# Added Speed parameter. When Speed is set to HALF the virtual tape runs at half the normal speed. The speed can be also be toggled via a MIDI CC message.
# Improved cross-fading at the start and end of the loop.

Added Mode parameter to Tone Match block. When set to OFF-LINE the processing is adjusted to better suit matching recorded sources such as guitar stems. When set to LIVE the processing is as before and better suited to matching a real-time source such as the output of a guitar amp.

Added Damping Time to Sequencer. This controls the time it takes to slew from the one value to the next.

Improved CPU usage for Synthesizer block when oscillator type is white or pink noise.

Improved Tuner.

Various GUI tweaks and improvements.

Changes/improvements to 3rd-Party MIDI device support (see AXE-FX III MIDI FOR THIRD-PARTY DEVICES document for details).

Fixed ADSR graphs not initializing properly on preset recall.

Fixed some parameter displays dependent on Tempo, i.e. Delay Time, not updating when new Tempo is entered.

Fixed Mixer and Multiplexer blocks shouldn’t be bypassable.

Fixed Tremolo block bug when LFO Type set to SAW DOWN.

=1.14=

Added MIDI CC for Looper Stop. This allows stopping recording or playback of the Looper via MIDI automation.

Added Friedman HBE 2018 C45 amp model.

Added gain monitoring for Input Dynamics control in Amp block.

Fixed MIDI status dump not working correctly.

Fixed divide-by-zero fault if turning Master Volume to zero on JS410 amp models.

=1.13=

Added “Dual Chorus” type to Chorus block. This type has independent LFOs for the left and right delay lines. Delay lines are BBD emulations.

Added “SSB Upper” and “SSB Lower” types to Ring Modulator block. These select the upper and lower sidebands of the modulation, respectively.

Added single-sideband ring modulators to Multidelay block. These can be used to create strange and interesting echo sounds. To defeat the modulators turn Master Ring Mod Mix to 0.

Added chorusing to individual delay lines in Multidelay block. There are four LFOs, one for each delay line. The rate and depth of each LFO is individually adjustable. These add to the main LFOs which modulate each delay line at the same frequency but different phases. By using short delay times the Multidelay block can now act as four parallel choruses, each with independent rate and depth.

Added Quad-Tap Band Delay type to Multidelay block. This type has the same configuration as the Quad-Tap delay except the filters are outside the feedback paths.

Added band highlighting to RTA block. Turn Value knob to select desired band. The frequency of the selected band is displayed in the upper left corner.

Increased number of channels in Multiplexer block to six, one for each row.

Changed preset recall behavior if Ignore Redundant PC is on. If Ignore Redundant PC is on and the desired scene (set via PC mapping) is different than the current scene the preset is not loaded but the scene IS changed.

Added MIDI support for 3rd-party devices to set/get scene, channel, bypass, scene names and preset names, control the Looper, tap tempo, etc. via System Exclusive messages. See the Axe-Fx III MIDI for Third-Party Devices document for implementation details.

Added Preset Increment/Decrement controllers. These can be used to increment/decrement the current preset. The Preset Start and Preset End parameters control the range of presets selected and selection wraps at the limits. Preset mapping and offsets are ignored.

Improved Tempo accuracy for MIDI clock.

Fixed Barberpole type in Phaser block broken.

Fixed no preset loading on startup if Ignore Redundant PC is on.

Fixed Scratchpad Cab #1 not loading automatically when doing an IR capture.

Various changes and fixes for FC controllers.

=1.12=

Added Global Block support for Input 1 block.

Added Scene Volumes to Output block.

Improved Multidelay block. The Band Delay type has been replaced by a more flexible Quad Parallel Delay. The Quad Parallel Delay and the Quad Series Delay now feature four delay lines in a parallel or series configuration, respectively, as before, with the output of each delay line feeding a series combination of a bandpass filter and a resonator. Added drive, low-cut and hi-cut filters allow further tone sculpting. To defeat the bandpass filters set Master Q to minimum. To defeat the resonators set Master Resonator Feedback to 0.

Improved Spring Reverb algorithm. New algorithm features improved dispersion modeling and adjustable low and high frequency decay time ratios.

Improved knob response for fine adjustments.

Fixed Reverb GUI so that only valid parameters show on All page for selected type.

Fixed system backup hanging if on preset containing certain types of foot controller data.

Fixed engaging Tuner causes reset of External Controller values.

Fixed Ignore Redundant PC not working.

Fixed Tremolo block not updating rate when entering tempo.

=1.11=

<blockquote>"1.11 fixed a minor mistake in the Output and MBC blocks GUI's. Not worth a public release." [http://forum.fractalaudio.com/threads/firmware-1-11.140004/page-2#post-1660386] </blockquote>

Fixed Multiband Compressor and Output GUI.

Fixed Looper block Dry Level not working.

=1.10=

Improved Scene/Channel switching.

Added “Stereoizer” type to Enhancer block. While the Classic and Modern types rely on micro-delays and inversions to create artificial stereo, the new Stereoizer uses multiple high-order filters to create a realistic stereo image.

Fixed Phaser block level dropping 3 dB when effect is engaged.

=1.09=

Added “Effect Bypass Mode” to MIDI menu. When set to “Value” the bypass state of an effect assigned to a CC is controlled by the CC value. When set to “Toggle” the bypass state toggles whenever the CC message is received, regardless of the value.

Added “Default Scene” parameter to Global menu. When set to “As Saved” the scene selected when recalling a preset is the scene that was active when the preset was saved. When set to a particular scene value that scene will always be selected when a preset is recalled.

Added Channel parameter to modifiers. This allows applying the modifier to all channels or only a selected channel of an effect block.

Added Tilt EQ to Amp block Input EQ types.

Added Boost Type and Boost Level to Amp block. There are seven boost types: Neutral, T808, T808 Mod, Super OD, Full OD, AC Boost and Shimmer. All boosts act as “clean boosts” replicating the oft-used “Drive on 0, adjust Level as desired” boost technique. The boost allows boosting the amp block without requiring a separate Drive block. The Boost Level parameter controls the amount of boost.

Added Modifier ability to Formant block Resonance parameter.

Added “Prompt on Edited Preset Change” parameter to Global Settings. When set to ON the unit will prompt before changing presets if the current preset has been edited (and prevent you from losing your edits). NOTE: Be sure to change this value to OFF before performing!

Added Global Blocks. There are 8 Global Blocks per effect instance. Not all effects support Global Blocks (i.e. Mixer, RTA, etc.). There are four operations associated with a Global Block:
# Link To Global Block: This operation links the selected effect with a Global Block. The Global Block data is NOT loaded. Upon saving the preset the Global Block is saved. Any other presets linked to this Global Block will load the Global Block data upon recall.
# Load From Global Block: This operation loads data from a selected Global Block but does NOT link the block.
# Link To and Load From Global Block: This operation links an effect to a Global Block AND loads data from the Global Block. Upon saving the preset the Global Block is saved. Any other presets linked to this Global Block will load the Global Block data upon recall.
# Unlink From Global Block. This operation disassociates the effect from any Global Blocks.
Global Block operations are accessible from the Tools page in the Layout menu.

Improved scene switching algorithm resulting in much faster, smoother scene changes.

Improved Reverb algorithms.

Changed Looper behavior:
# Pressing Undo while recording undoes the last recorded layer, as before. Pressing Undo when the loop is stopped now erases the loop data. Pressing Undo during playback undoes the last recorded layer. Pressing Undo again (during playback) restores the undone layer. Subsequent presses toggle the layer on and off.
# Pressing Record now always starts a new layer (previously pressing Record during the first layer stopped recording and entered playback).
# Pressing Once while recording stops the loop.

Added Dry Level parameter to Looper Block.

Improved Input block noise gate. When the Type is set to Intelligent (default) the noise gate now provides smart EMI filtering which reduces hum and buzz. NOTE: For best results the AC Line Frequency parameter in the Global Settings menu should be set to match the power line frequency of your country (i.e. 60 Hz for North America, 50 Hz for EU, etc.).

Improved Amp block output transformer modeling.

Various changes to support Axe-Edit.

Various changes to support FC-6/12 controllers.

Changed default value for Setup -> MIDI -> Program Change to ON.

Fixed Scene MIDI block not sending correct data on preset change.

Fixed cabinet names not showing up in cab picker until background tasks are finished.

Fixed wrong Preamp Bias value in Plexi 2204 model.

Fixed Pitch block LFO Tempo not being updated on tempo changes.

Fixed RTA block not updating on preset change.

Fixed noise in Looper block when pressing Undo.

Fixed Modifier Auto-Engage working erratically if Update Rate set to Slow or Medium.

Fixed MIDI PC Offset not being applied.

Fixed crash if flooding unit with MIDI data during boot.

Fixed hang if MIDI Send PC is set to OMNI.

=1.08=

Various changes to support Axe-Edit.

Fixed Channels not copying correctly when using Scene copy utility function.

Fixed Global data not being saved after import (restore).

Fixed Reverb hold not working for Spring types.

=1.07=

Fixed Pitch block not setting number of voices correctly, i.e. Whammy modes should have one voice but two voices were audible.

Fixed Input 1 Level Meters not scaled properly when input source is USB.

Fixed minor bug in Rotary GUI.

Fixed wrong default Output Level value in Return block.

Fixed garbage data in SPDIF output buffer if no Output 1 block in layout.

Added “Update Rate” parameter to Modifiers. Values are Slow | Medium | Fast. The Update Rate selects the rate at which the modifier updates the target parameter. For most applications a slow rate is sufficient. Under some circumstances a slow rate may cause “zipper noise”. Increasing the rate will reduce the noise at the expense of increased CPU usage.

=1.06=

Added “Solo” ability to Cab block.

Added “Plexi 2204” Amp model based on a 1981 JMP 50W Master Volume head.

Added modifier capability to Resonator block Chord and Frequency parameters.

Fixed Output block buffer stuck when bypassed causing high pitched tone.

Fixed Pitch block not initializing correctly on patch change.

Fixed Pitch block sometimes getting “stuck” on negative harmony shifts.

Fixed distortion on Crystal Echoes pitch type if Direction is set to Reverse and Shift is set to +4.

Fixed MIDI message(s) immediately following a PC message being ignored, i.e. Scene Select CC.

Fixed some minor GUI bugs.

=1.05=

Added ability to route block when Layout is zoomed out.

Added Input Source select to ADSR and Envelope in Control block. Fixed MIDI bank select.

Fixed Scene Copy function not copying Amp block bypass states.

Fixed can’t select Amp type when creating a new preset if the previous preset had the Amp block channel as anything other than ‘A’.

Fixed External Controller initial values not being applied and garbage values in any of these controllers that are not assigned.

=1.04=

Fixed low-cut and high-cut filters not working in Multitap Delay block.

Fixed Amp blocks bypass states not being preserved across preset changes.

Fixed Tone Match block Smoothing parameter not working.

Fixed Quad Tape Delay missing modifier for Motor Speed (formerly labeled Tape Speed).

Fixed MIDI CC Channel changes not responding above values of 3.

Various GUI enhancements and improvements.

=1.03=

First public firmware release.

=1.01/1.02=

Initial firmware release on the first shipped units.

No release notes.

[[category:Axe-Fx3]]
[[category:All]]

Amp models list

2023-12-02T07:40:23Z

James-F: /* PLEXI 50W 6550 (1972 50W Marshall Plexi) */

This page lists all amp models in Fractal Audio’s current generation of guitar processors, with brief additional information (based on "Cygnus" amp modeling). Depending on the firmware, some models may not yet be available on every device. The information also partly applies to the previous generation of modelers (Axe-Fx II series and AX8). Many of the amp models are featured in [[Factory presets]].

[http://wiki.fractalaudio.com/axefx2/index.php?title=Yeks_Guide_to_the_Fractal_Audio_Amp_Models Yek's Guide to the Fractal Audio Amplifier Models] provides in-depth information about many amp models.

Fractal Audio owns all the amps on which the models are based, except the Bludotone. [https://thegearforum.com/threads/fractal-audio-firmware-update-thread.673/page-54#post-46151]

[[file:Allamps.jpg|500px]]

__TOC__

==1959SLP JUMPED (100W Marshall Super Lead Plexi 1959 reissue)==

[[file:SLP.png|300px]]

Models:
* Normal and Treble channels jumpered
* Normal channel
* Treble (High) channel

[[Cabinet models list| Cab:]] Marshall 4x12 (G12M, G12H)

Volume Normal, Volume Treble, Bass, Middle, Treble, Presence

Power tubes: EL34

# (about the Plexi model in the Standard/Ultra): "One of the first mods people make to real 'Plexi' Marshalls is to "clip the bright cap". The bright cap varied over the years, supposedly depending on what was lying around in the shop. The model defaults to the bright cap in the circuit. If you turn off Bright you're effectively clipping the bright cap. The bright cap in Marshalls can be very bright and harsh. However, if you crank the Master you might find the extra brightness helps compensate for the power amp getting darker."
# (about fizz) "It's the way a Plexi is supposed to sound. That's due to the cathode follower. That raspiness helps it cut through in a mix. I own three of them and they are that fizzy." [https://forum.fractalaudio.com/threads/high-end-fizz-is-this-normal.43598/#post-576475]
# "Don't be afraid to turn the bass all the way down or the treble all the way up. Just like with the actual amp. For example, on the normal channel of a Plexi most people turn the bass way down. Otherwise it's too flubby."
# "The old one (Plexi 100w model) has a 2.7K cathode resistor on the first stage, the new one (1959SLP) has an 820 ohm." [https://forum.fractalaudio.com/posts/1111403]
# "I based the SLP on using it with G12H(55) speakers which have a resonance of 55 Hz. When mounted in a typical cab the resonance will be in the low 70s. There is no right or wrong. Whatever sounds best." [https://forum.fractalaudio.com/posts/1159759]
# "My settings for a "typical" Plexi tone are Bass: 2, Mid: 8, Treble 7.5. Adjust Presence to taste." [https://forum.fractalaudio.com/posts/1179420]
# "What you are hearing is output transformer high frequency resonance. Old Plexis didn't do this because they had good transformers. New transformers are crappy and resonate at the cutoff frequency because they are underdamped. This causes a raspy, fizzy texture to the distortion. The transformer resonance is adjustable but the parameter isn't exposed to the user. When you turn it up you get that same squishy rasp that you are hearing. For the Plexis I have the damping set to flat with no resonance because that's how our vintage Plexis measure. Our 50W is a little underdamped but people complain about raspy high frequencies so I erred on the safe side." [http://forum.fractalaudio.com/threads/dimed-real-plexi-vs-dimed-simulation-q8-01.127161/page-2#post-1513888]
# "When modding Marshalls for higher gain sometimes the modder will decrease the input frequency response to reduce noise and fizziness. You can do this by reducing the high-cut frequency in the input EQ. Or you can use a high-shelf filter which is a little more subtle. Another technique is to put a capacitor across the second-to-last triode stage. This is the "Triode 1 Plate Freq" parameter. Reduce this to around 2 kHz to start which is typical of amps like an SLO100, etc." [https://forum.fractalaudio.com/threads/dialling-in-the-marshalls.143682/post-1707222]
# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]
# [[Amp_block#NEGATIVE_FEEDBACK|Negative feedback value]]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-1959slp-marshall-slp1959.111321/ Yek's write-up]

==1959SLP NORMAL==

# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]

==1959SLP TREBLE==

# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]

==1987X JUMPED (50W Marshall 1987X reissue) ==

[[file:1987X.png|300px]]

Models:
* Normal and Treble channels jumpered
* Normal channel
* Treble channel

[[Cabinet models list | Cab:]] Marshall 4x12 (G12M, G12H)

Volume Normal, Volume Treble, Bass, Middle, Treble, Presence

Notes: see 1959SLP

Power tubes: EL34

# "The 1987x doesn't have the 0.68uF cap on the last triode. Gives it a smoother distortion." [https://forum.fractalaudio.com/posts/1000388]
# "Our reference amp has no bright cap. Looks like it was that way from the factory. There are no signs it was removed. The location in the circuit board is empty and the solder joints do not appear to have been disturbed." [https://forum.fractalaudio.com/threads/1987x-bright-switch-off-by-default.145332/post-1718899]
# [[Amp_block#NEGATIVE_FEEDBACK|Negative feedback value]]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-1987x.111362/ Yek's write-up]

==1987X NORMAL==

==1987X TREBLE==

==5153 100W BLUE (EVH 5150-III)==

[[File:5153.png|300px]]

5150-III models:
* 100W amp, Blue channel
* 100W amp, Green channel
* 100W amp, Red channel
* 100W Stealth amp, Blue channel
* 100W Stealth amp, Green channel
* 100W Stealth amp, Red channel
* 50W amp, Blue channel

[[Cabinet models list| Cab:]] 5150 4x12 or 2x12 (G12H, G12EVH)

Gain, Low, Mid, High, Volume, Presence, Resonance (only on 50w model)

Power tubes: 6L6

# "IMO, it's a very good amp. The build-quality is great and the design is very good. It is similar to the previous versions but voiced a bit different. Personally, I think all of the 5150's have more gain stages than necessary which just makes for unnecessary failure points but the "OMG, this amp has sooo many toobz it must sound awesome" marketing makes it understandable. It's incredibly heavy though." [https://forum.fractalaudio.com/posts/679483]
# "A 5150 uses a fixed bias with no adjustment. Depending on the tubes used the bias can run from average to cold. The model uses average. Some people like a colder sound. If you prefer your amps biased cold, then reduce the bias parameter to taste." [https://forum.fractalaudio.com/posts/742231]
# "The 50W version has a different input network than the 100W version for that channel. The 50W version has about twice the gain as a result. Otherwise things are pretty similar. You can simulate this using the Input Trim knob." [https://forum.fractalaudio.com/posts/1042144]
# "The red channels (of 50w and 100w models) are identical." [http://forum.fractalaudio.com/threads/5153-50w-blue-red.106463/#post-1273739]
# "Some amps have a fixed depth circuit, e.g. 5153, Freidman BE/HBE, Dirty Shirley, TripTik, Tucana, et. al. In these cases the Depth knob will default to a value that corresponds to the fixed circuit." [https://forum.fractalaudio.com/threads/lets-talk-about-the-depth-control.88747/#post-1071598]
# "The 5150 models are absolutely identical to our reference amp." [https://forum.fractalaudio.com/threads/legacy-amp-models-consider-revisiting-full-honest-request-and-opinion.160349/post-1919792]
# "The Normal Gain input has a very low input impedance, about 44K in addition to cutting the gain in half. Use the Input Impedance feature of the Input block to simulate. Try 32K." [https://forum.fractalaudio.com/threads/why-fractal-is-good-for-my-sanity-and-my-wallet.167246/post-2008937]
# "A 5150's presence control has almost no effect from 0 to 7. After 7 the treble increases rapidly. The taper of the presence control in a 5150 is a log30 IIRC (maybe log10, I'd have to check my notes). If anything it should be linear. Ideally it should be reverse log. Our model uses a reverse log taper which gives a nice, smooth response over the full range. In most cases a reverse log taper would be the ideal taper. However reverse log taper pots are uncommon, difficult to source and cost more. Why they chose a log taper in the 5150 is a mystery. Since the power amp has similarities to a Marshall perhaps Eddie wanted the presence control to behave like his old Marshalls. Another possibility is the designer felt the amp was too bright with all knobs at noon (and a linear taper presence pot) and changed the taper to reduce the brightness." [https://www.thegearpage.net/board/index.php?threads/blind-test-mesa-dual-rectifier-vs-mystery-modeler-update-results-revealed.2208367/post-31639265]
# "Amps with low amounts of negative feedback in the bass region are sensitive to the impedance curve. The 5153 is one of these amps due to its NFB circuit." [https://thegearforum.com/threads/evh-amp-vs-axe-fx-qc-and-tmp.3593/post-133163]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-5153-evh-5150-iii.111404/ Yek's write-up]

==5153 50W BLUE==

==5153 100W GREEN==

==5153 100W RED==

==5153 100W STEALTH BLUE (EVH 5150III 100S 100W)==

[[File:5153S.jpg|300px]]

# "The Blue channel gain knob affects the Red channel somewhat. I modeled it with the Blue channel gain knob at noon." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-23-04-release.199875/post-2491407]
# "The Red channel has much more gain but the Gain pot taper is very different. The Red channel has a 5A taper, while the Blue channel has a 30A taper so at noon it will appear as though the Blue channel has more gain." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-23-04-release.199875/post-2491406]

==5153 100W STEALTH GREEN==

==5153 100W STEALTH RED==

==59 BASSGUY BRIGHT (1959 Fender narrow-panel Tweed Bassman, 5F6-A)==

[[file:bassman.jpg|300px]]

Models:
* Bright channel
* Normal channel
* Jumpered channels

[[Cabinet models list | Cab:]] Fender 4x10 with Jensen Alnico 25W P10R or 40W P10Q

Volume Normal, Volume Bright, Bass, Middle, Treble, Presence

Power tubes: 6L6/5881

# [before 19.02 for the Axe-Fx III] "There is no "High" channel on a 59 Bassman. There is a Normal and Bright channel. The Bright channel model is selected by turning on the Bright switch. The models are based on the higher gain input (the "1" input). To simulate the lower gain input simply set Input Trim to 0.5." [https://forum.fractalaudio.com/posts/1109139/]
# [19.02 and later for the Axe-Fx III] "Updated 59 Bassguy and 5F8 Tweed models to include both Drive controls."
# "All the Fender models except the 59 Bassman and 5F8 Tweed don't have cathode followers." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-00-beta-3.148907/page-3#post-1764588]
# ("Cygnus" amp modeling) "The Bassman was reworked using an original 59 Bassman 5F6-A as a reference. This has a 12AY7 input buffer which has less gain than the reissue which uses a 12AX7A (7025 actually, same thing)."
# ("Cygnus" amp modeling) "The Bassman and Deluxe Tweed models are both modeled using a 12AY7 as the input buffer. The Preamp Tube Type parameter only affects the tubes after the input buffer." [https://forum.fractalaudio.com/threads/12ay7-preamp-tube-for-tweed-deluxe-and-bassman-models.175834/post-2135435]
# "The input to the second 12AX7 is a summing node. Both volume controls affect the signal. If you plug into the Bright input the Normal volume control will also control the volume to some degree and change the frequency response." [https://forum.fractalaudio.com/threads/bassman-how-do-the-way-the-2-drive-controls-interact.181986/post-2232557]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-59-bassguy-59-fender-tweed-bassman-5f6-a.111275/ Yek's write-up]

==59 BASSGUY JUMPED==

==59 BASSGUY NORMAL==

==59 BASSGUY RI JUMPED (Fender 59 Bassman LTD Vintage Reissue)==

[[file:FENDER_BASSMAN_RI.jpg|275px]]

Model:
* Jumpered channels

[[Cabinet models list | Cab:]] Fender 4x10 with Jensen Alnico 25W P10R or 40W P10Q

Volume Normal, Volume Bright, Bass, Middle, Treble, Presence

Power tubes: 6L6

# See 59 Bassguy.
# "There are quite a few differences between a 5F6-A and the reissue: [https://forum.fractalaudio.com/threads/bassman-how-do-the-way-the-2-drive-controls-interact.181986/post-2358853]
## 12AX7A vs. 12AY7 input tube.
## Different tone stack (this is a big one).
## Different presence network.
## Different B+ voltage.
## 6L6s vs 5881s (minimal difference).

==5F1 TWEED (Fender narrow-panel Tweed Champ, 5F1)==

[[file:champ.jpg|300px]]

Model:
* Single channel

[[Cabinet models list| Cab:]] Fender 1x8

Volume

Power tubes: 6V6

# "This particular amp exhibits a unique breakup characteristic due to its single-ended design and simple circuit."

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-5f1-tweed-fender-champ.111067 Yek's write-up]

==5F1 TWEED EC (2011 Fender EC Vibro-Champ)==

[[file:EC-Vibro-Champ.jpg|300px]]

Model:
* Single channel

[[Cabinet models list| Cab:]] Fender 1x8

Volume, Tremolo

Power tubes: 6V6

# "The circuit is slightly different than the original 5F1. It has cathode bypass caps giving it more gain." [http://forum.fractalaudio.com/threads/fractal-audio-amp-models-5f1-tweed-fender-champ-5f1.111067/page-2#post-1508977]
# "It's a single-ended power amp with negative feedback and bias tremolo. Subtle is the only possibility with this configuration. Bias tremolo works by modulating the quiescent operating point of the power tubes. With a single-ended power amp with negative feedback the gain doesn't change much as you change the operating point, hence the tremolo effect is subtle. Bias tremolo works best on amps with little to no negative feedback." [https://forum.fractalaudio.com/threads/fw-q8-5f1-tweed-ec-4-scene-preset-vid-demo.126829/post-1509387]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-5f1-tweed-fender-champ.111067 Yek's write-up]

==5F8 TWEED BRIGHT (Keith Urban's 1959 Fender narrow-panel high-power "big box" Tweed Twin, 5F8==

[[file:5f8-2.jpg|300px]]

Models:
* Bright channel
* Jumpered channel
* Normal channel

[[Cabinet models list| Cab:]] Fender 2x12 (P12N, but Keith Urban's cab has Two-Rock speakers)

Volume Bright, Volume Normal, Presence, Middle, Bass, Treble

Power tubes: 6L6

# [before firmware 19.02 for the Axe-Fx III] Engage the Bright switch for the Bright channel
# "Based on a 1959 Fender Twin Amp. This particular model is based on Keith Urban’s “#1”. Thank you Keith for allowing us the use of your prized amplifier."
# "All the Fender models except the 59 Bassman and 5F8 Tweed don't have cathode followers." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-00-beta-3.148907/page-3#post-1764588]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-5f8-tweed-keith-urbans-high-power-fender-twin-amp.111123 Yek's write-up]

==5F8 TWEED JUMPED==

==5F8 TWEED NORMAL==

==65 BASSGUY BASS (1965 Blackface Fender Bassman head, AB165)==

[[file:ab165.png|300px]]

Models:
* Bass channel
* Normal channel

[[Cabinet models list | Cab:]] Fender 2x12 (Oxford)

Volume, Bass, Treble, fixed Presence circuit (Presence should be at 10), Bright switch (Normal channel only)

Power tubes: 6L6

# "Has a pissed-off Marshall vibe to it." [http://forum.fractalaudio.com/posts/490912]
# "The 65 Bassguy was matched to a 65 Bassman that Dweezil sent me. It's a vicious amp that sounds more like a Plexi than a Fender. It's the infamous AB165 circuit which is very crunchy and bright and does not sound like your typical Fender." [https://forum.fractalaudio.com/threads/am-i-the-only-one-who-noticed-that-some-amps-have-alot-more-gain.51123/page-2#post-658833]
# "It's a crazy sounding amp, sounds nothing like your typical Fender." [https://forum.fractalaudio.com/threads/another-v10-preview.62489]
# "The AB165 uses 7025 preamp tubes (which are relabeled 12AX7). The phase inverter, however, is a 12AT7. The secret to the AB165 is the summing stage. It uses a inverting summing amp to sum the Normal and Bass inputs. This stage clips, because of all the local negative feedback, quite hard." [http://forum.fractalaudio.com/posts/

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-65-bassguy-65-blackface-fender-bassman-ab165.111298/ Yek's write-up]

==65 BASSGUY NORMAL==

==6G12 CONCERT (1960 Brownface Fender Concert, 6G12)==

[[file:6G12.jpg|300px]]

Model:
* Vibrato channel

[[Cabinet models list | Cab:]] Fender 4x10 with Jensen Alnico 25W P10R or 40W P10Q, or ceramic 25W C10R, or Oxford

Volume, Bass, Treble, Presence, Vibrato (not modeled)

Power tubes: 6L6

# "Super 6G4 is a Brownface Fender Super. Concert 6G12 is a Brownface Fender Concert. They are very similar amps and both sound "old". They definitely have that early 60's vibe to them." [https://forum.fractalaudio.com/threads/axe-fx-ii-firmware-17-02-released.93734/#post-1124507]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-6g12-concert-60-fender-brownface-concert.111224/ Yek's write-up]

==6G4 SUPER (1960 Brownface Fender Super, 6G4)==

[[file:6G4.jpg|300px]]

Model:
* Vibrato channel

[[Cabinet models list | Cab:]] Fender 2x10 with Jensen Alnico 25W P10R, 40W P10Q or Oxford 10K5, or a Fender 2x12

Volume, Bass, Treble, Presence, Vibrato (not modeled)

Power tubes: 6L6

# "Super 6G4 is a Brownface Fender Super. Concert 6G12 is a Brownface Fender Concert. They are very similar amps and both sound "old". They definitely have that early 60's vibe to them." [https://forum.fractalaudio.com/threads/axe-fx-ii-firmware-17-02-released.93734/#post-1124507]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-6g4-super-60-fender-brownface-super.111173 Yek's write-up]

==AC-20 12AX7 BASS (Morgan AC20 Deluxe)==

[[file:morgan.jpg‎|300px]]

Models:
* 12AX7 Bass
* 12AX7 Treble
* EF86 Bass
* EF86 Treble

[[Cabinet models list | Cab:]] Morgan 1x12 (G12 Alnico Blue), DynaCab available

Volume, Cut, Sun/Moon switch (= Bright switch), Brilliance switch (= Bass Cut), power scaling (not modeled), EF86/12AX7 switch

Power tubes: EL84

# "The AC-20 model is based on the amp with the power scaling at maximum power which effectively disables it (and sounds best IMO)." [https://forum.fractalaudio.com/posts/1079502]
# "The AC-20 has power scaling. The Axe-Fx II does not model the power scaling circuit as there is no point in that." [https://forum.fractalaudio.com/threads/power-level-ac-20.89488/#post-1079494]
# "As with the real amp I dial in quite a bit of Hi-Cut." [http://forum.fractalaudio.com/threads/recommend-an-amp-for-p-w.106093/#post-1268874]
# "I think an AC-20 does the Vox thing better than Vox." [https://forum.fractalaudio.com/threads/recognition-and-respect-to-cliff-and-his-morgan-ac20.155040/post-1844685]
# "AC-30's have a poorly designed cathode follower. The bias point is totally wrong and crushes one side of the signal considerably. IMO either the cathode resistor should be 100K or the plate resistor of the preceding stage should be higher, 200K. The clipping is extremely asymmetric. Too much IMO. A little asymmetry is good because it warms things up. Too much causes excessive even-order harmonics which makes things fuzzy and indistinct. The clipping is so asymmetric on an AC-30 that it's almost a half-wave rectifier. You can tweak this by adjusting the Preamp Bias point and/or lowering the Cathode Follower Compression. Or you can lower the Harmonics value which reduces the asymmetric distortion. The downside of that is that it then overdrives the phase inverter causing blocking distortion from excessive bias excursion. Another thing to try is to increase the Grid Clipping value which will add a little headroom. Start with the Bias point. AC-30's are very sensitive to the tube type and part tolerances. A tiny change in the bias point can make a big difference. The default bias point is based on Mullard ECC83 tubes. I prefer the AC-20 because it doesn't have a cathode follower so doesn't suffer from these problems. The cathode follower in an AC-30 doesn't even do all that much. Normally you use a cathode follower to preset a low-impedance source to the tone stack but the tone stack in an AC-30 doesn't present that great of a load anyways." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-02.148983/page-11#post-1767187]
# "One reason I like the AC-20 is that it runs the tubes hotter and exhibits less crossover distortion." [https://forum.fractalaudio.com/threads/papery-buzz-under-some-models.149193/page-2#post-1772639]
# "The Sun/Moon equals the Bright Switch. The Bass/Treble switch would be different amp models. So AC20 EF86 Bass model would be the Bass/Treble switch in the Bass position, the switch on the back in EF86 position and then the Bright switch on the model is the Sun/Moon switch on the amp." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-10-00.154850/post-1842330]
# "So I was testing the next beta and selected the AC-20. Was hearing a lot of ghost notes compared to the old algorithm (in the debug build I can select between algorithms with a hidden parameter) and figured that couldn't be right. Hooked up the real AC-20 and, sure enough, ghost notes galore at the same settings." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-0-public-beta.154714/post-1840850]
# "Our reference amp is a head with matching 1x12 cab." [https://forum.fractalaudio.com/threads/recognition-and-respect-to-cliff-and-his-morgan-ac20.155040/post-1844744]
# "The normal channel on a Vox would be closest to the Morgan. The Brilliant channel is a "Top Boost" which means it has a tone stack and a significant midrange cut. The normal channel has no tone stack. You can't compare a a Morgan AC20 to the Brilliant channel of an AC30 and declare that one sounds better than the other. Totally different preamps and, therefore, different sound. Personally I think the AC20 is a better amp. Better made, better quality components, much better transformers. If you want that chimey AC30 sound you put an EQ before it and suck out some mids." [https://forum.fractalaudio.com/threads/how-accurate-is-fractals-amp-modeling.168786/post-2064189]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-ac-20-morgan-ac20-deluxe.111453/ Yek's write-up]

==AC-20 12AX7 TREBLE==

==AC-20 EF86 BASS==

==AC-20 EF86 TREBLE==

==ANGLE SEVERE 1 (Engl Savage 120)==

[[File:savage.png|300px]]

Models:
* Lead channel, Contour switch OFF (boosts lower midrange around 500 Hz)
* Lead channel, Contour switch ON (boosts from 1200 Hz and cuts lower midrange)

[[Cabinet models list | Cab:]] Engl 4x12 (V30, V60)

Gain (input sensitivity), Lead (degree of distortion), Lead Boost switch, Contour switch, Bass, Middle, Treble, Rough/Smooth switch (not modeled), Master, Presence, Depth Boost switch

Power tubes: 6550

# "From noon and up it's a presence boost, from noon down it's a presence cut." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-1-03-firmware-release.106931/page-12#post-1280997]
# "(...) Engl Savage presence network which reduces negative feedback as the control is turned down causing an increase in volume." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-5-cygnus-firmware-public-beta-2.170901/post-2059273]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-angel-severe-engl-savage-120.111501/ Yek's write-up]

==ANGLE SEVERE 2==

==ARCHEAN (100W PRS Archon)==

[[File:Archon.jpg|300px]]

Models:
* Archean: Lead channel with Bright switch OFF
* Archean Bright: Lead channel with Bright switch ON
* Archean Clean: Clean channel

Master, Bass, Middle, Treble, Bright switch, Volume, Depth, Presence, Output Power (not modeled)

Power tubes: 6L6

# "You have to crank the MV on the real amp. The preamp is very "dry" so to get the juices flowing the power amp needs to be working hard. This also smooths out that funky midrange." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-14-01.165716/page-10#post-1990153]
# "I think part of the reason the real Archon needs to be cranked is because the power supply is too stiff. It's got six (!!!) big caps filtering the B+. That's too much filtering IMO unless you're playing at arena volumes. If I were to make a modification to the amp it would be a switch to disconnect four of those caps so the supply is more bouncy at moderate volumes. Maybe also a tube rectifier to add some more sponge." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-14-01.165716/page-10#post-1990169]
# Based on 100W amp [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-14-01.165716/post-1990412]

[https://forum.fractalaudio.com/threads/fractal-audio-amp-models-archean-based-on-prs-archon.165751/ Yek's write-up]

==ARCHEAN BRIGHT==

==ARCHEAN CLEAN==

==ATOMICA HIGH (Cameron Atomica)==

[[file:atomica.jpg|300px]]

Models:
* Low gain input
* High gain input

[[Cabinet models list | Cab:]] cabinet with G12H speakers

Thump, Presence, Bass, Middle, Treble, Master, Gain, Edge (not modeled), 3-way Gain Voice switch

Power tubes: EL34

# "The Atomica can tolerate high MV because it is a "Jose-style MV". The Jose-style MV imparts a very high source resistance to the tone stack which causes much more insertion loss and therefore lower drive level into the power amp." [https://forum.fractalaudio.com/posts/748843]
# "Cameron amps are basically modified Marshalls. The Atomica is essentially a slightly modified JCM800 with a Jose-style zener clipper." [https://forum.fractalaudio.com/threads/dialling-in-the-marshalls.143682/page-5#post-1706652]
# (fuzzy tone with Bright on) "That's the way those amps sound with the bright switch on. It's due to the location of the drive control. Turn down the Preamp Bias Excursion to reduce it. The problem with those "Mid Stage Drive" designs using a Plexi drive network is that if you bypass the drive pot with a cap (bright cap) you also bypass any grid stoppage and the next stage goes into blocking distortion very easily. There's essentially a straight shot into the grid for all the high frequencies. Friedman probably realized this and that's why there's no bright cap on the BE as the BE is very similar to the Atomica." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2052829]
# "The Cameron is a genuine Cameron. I don't know the lineage of the Atomica." [https://forum.fractalaudio.com/threads/are-any-of-the-cameron-models-of-mark-cameron-built-amps.199792/#post-2489827]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-atomica-cameron-atomica.111547 Yek's write-up]

==ATOMICA LOW==

==BAND-COMMANDER (1968 Silverface/Blackface Fender Bandmaster head, AB763)==

[[file:bandmaster.jpg|300px]]

Model:
* Vibrato channel

[[Cabinet models list| Cab:]] Fender 2x12

Vibrato channel: Volume, Bright switch, Treble, Bass, Tremolo

Power tubes: 6L6

# "The vibrato channel is loaded down by the vibrato circuit. The normal channel isn't. You can probably get close using the vibrato channel model by increasing the MV trim." [http://forum.fractalaudio.com/threads/maroon-5-axe-fx-iii-awesomeness.146287/page-2#post-1730430]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-band-commander-68-fender-bandmaster-ab763.111596 Yek's write-up]

==BIG HAIR (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "It was a total guess. I just tuned it by ear. It's just my idea of what 80's hair metal might sound like." [http://forum.fractalaudio.com/posts/700269/]
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-big-hair.111635/ Yek's write-up]

==BLANKENSHIP LEEDS (Dweezil Zappa's Blankenship Leeds 21)==

[[file:blankenship.jpg|300px]]

Model:
* Single channel

[[Cabinet models list|Cab:]] 2x10, 1x12, 2x12 (G12M)

Volume, Tone, Tremolo

Power tubes: EL84

# "Based on a Blankenship Leeds which is a boutique version of an 18W Marshall. This particular amp is known for sounding “big” despite being relatively low power."
# "The model was matched to Dweezil's amp. He loaned it to me because it was one of his favorite amps and I can see why. It's a really cool amp."
# "The amp has no hi-cut circuit therefore the control won't do anything. Neither will the Depth."
# "18W Marshalls are kind of a bad design. The phase inverter drives the power tubes too hard which results in excessive bias excursion.” [http://forum.fractalaudio.com/threads/marshall-1974x.121516/#post-1446363]
# "The phase inverter design causes significant bias excursion. That bias excursion, however, causes the amp to sound more open when driven hard (at the expense of crossover distortion)." [https://www.thegearpage.net/board/index.php?threads/is-digital-getting-too-real.2275913/post-32977457]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-blanknshp-leeds-blankenship-leeds-21.111681/ Yek's write-up]

==BLUDOJAI CLEAN (Bludotone Ojai)==

[[File:ojai.png|300px]]

Models:
* Clean channel with PAB (Pre-Amp Bypass) OFF
* Overdrive channel with PAB OFF
* Overdrive channel with PAB ON

[[Cabinet models list|Cab:]] Bludotone 1x12, 2x12 (G12-65, EVM)

Volume, Overdrive Level (Overdrive channel only), Treble, Middle, Bass, Master, Presence. Switches: Bright, Mid (not modeled), Rock/Jazz (not modeled). Footswitchable Pre-Amp Bypass (PAB) which bypasses the tonestack (Bass / Middle / Treble)

Power tubes: 6L6

Forum member AustinBuddy, owner of the original amp:
# "The model is of a 100w 6L6 BludoDrive Ojai by Bludotone amps, using Fractal's MIMIC process. The Ojai has the same schematic as the famous "Tan" boutique amp played by Robben Ford. It pairs well with the factory Rumble 4X12 cabinet. On the Ojai there is a bright cap on the Master Volume. As you turn the MV down, it will get thinner. This makes the MV even more sensitive than usual since there’s another interaction going on. To get the most range out of this amp, experiment with Master Volume and listen how it interacts with low or high Drive settings, similar to the real amp. The breakup range/tones between is wide and dynamic and can respond to your playing dynamics, getting crunchier as you dig in and cleaner as you play lighter. The amp's Bass response should increase noticeably as you turn up the Master Volume from the default MV position. Pair it with a G12-65H speaker. Cab Pack 17 has many choices (full disclosure, I produced 5 of the 6 Cabs in that Cab Pack). The BludoMix Cab in factory firmware is a 1x12 Alnico dual port cab, and will sound good but perhaps a tad darker (great for Jazz) on clean sounds than the G12-65H will. Now, if you like, put a Zen drive in front on the BludoClean amp....or a boost...and listen to how that clean channel wakes up fast for grittier leads and touch-responsiveness. For BludoLead, take the Lead default amp values. Put the Master Volume on 5. Put drive at 4-5 and Overdrive at 4-5, and experiment with the tone stack swaps above. If you want the amp to feedback effortlessly on a note, raise the overdrive setting higher combined with the gain, provided you have sufficient volume coming out your speakers to hit your guitar pickups in a reinforcing loop, it will do it! Throw a boost or Zen drive on that, if you like..." [http://forum.fractalaudio.com/threads/dumble-ford-2-again.105028/page-2#post-1267280]

# "The tone stack in the PAB models is a neutral tone stack which is the same as lifting the ground. Put all knobs at noon if you want authentic." [http://forum.fractalaudio.com/threads/love-3-0-but.147215/page-3#post-1739726]
# "The tone stack in the PAB models is a neutral tone stack which is the same as lifting the ground. Put all knobs at noon if you want authentic. Unlike the amp, however, you can actually adjust the tone controls and something will happen. In the virtual realm we can have lifted tone stacks that actually still work." [http://forum.fractalaudio.com/threads/love-3-0-but.147215/page-3#post-1739726]
# "Pre, mid and post aren't absolute locations. They're relative to the particular model. In the Lead model there is a buffer and then three gain stages IIRC. Pre means the tone stack is before the three gain stage in this case. Changing it to Mid would put it after the first gain stage. In the Clean model there is only a buffer and one gain stage. In this case mid means the stack is between the buffer and gain stage. Changing it to pre would put it before the buffer. Since there are only two tubes pre would indicate before the buffer which is not what we want. In the PAB model there is no tone stack so I put a neutral tone stack after the gain stages (with a fixed attenuation after the buffer). This allows the most flexibility. The HRM case the neutral tone stack is replaced by a Marshall tone stack." [http://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-3-01.147229/page-2#post-1739969]
# "The real amp has Overdrive Volume (sometimes labeled Ratio) and a Master Volume. The models assume the Overdrive Volume is at maximum." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-16-01-cygnus.172911/post-2091820]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-bludojai-bludotone-ojai.111724/ Yek's write-up]

==BLUDOJAI LEAD==

Formerly: BLUDOJAI LEAD 1

==BLUDOJAI LEAD PAB==

Formerly: BLUDOJAI LEAD 2

==BOGFISH BROWN (Bogner Fish preamp)==

[[File:fish.png‎|300px]]

Models:
* Strato channel
* Brown channel

Master, Gain, Bass, Mid, Treble

Power tubes: EL34

# "I used the power amp models from the XTC." [https://forum.fractalaudio.com/threads/bogner-strato-and-brown-poweramp-modeling.76238/#post-931081]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-bogfish-bogner-fish.111780/ Yek's write-up]

==BOGFISH STRATO==

==BRIT 800 2204 HIGH (50W Marshall JCM 800 2204)==

[[file:2203.png|300px]]

Model:
* Single channel, low and high inputs

[[Cabinet models list |Cab:]] Marshall 4x12 (G12M, G12H, G12-75, V30)

Pre-Amp, Bass, Middle, Treble, Presence, Master

Power tubes: EL34

# "It is a very bright model. However, it sounds exactly like the amp it was based on. If it is too bright, you can adjust the various tone controls and parameters to reduce the brightness to your tastes. They are designed to be run loud and the brightness decreases as the MV is increased. The sound of 80's hair metal for sure." [https://forum.fractalaudio.com/threads/afxii-jcm800-model.38498/#post-525964]
# "The saturation switch switches in a zener diode clipping stage right before the tone stack. This is the Arrendondo Mod." [http://forum.fractalaudio.com/threads/axe-fx-ii-technical-questions-thread.35997/page-38#post-494304]
# "Rips my head off here. I have to turn the presence way down. Check the MV. Too high and will get muddy." [http://forum.fractalaudio.com/threads/jcm-800-sounds-a-bit-muddy-with-fw-6-0-tips.51063/#post-657800]
# "That "interference" is due to all the treble peaking used in the design. JCM800s have quite a bit of treble boost. When you first attack the string the note is unpitched. It's basically a brief explosion of noise. The treble boosting amplifies the upper frequencies of this noise burst which is what you hear. However, when you playing in a loud mix that treble boosting helps the sound cut. Modern designs use more carefully crafted treble boosting to retain the cut but tame some of the harshness of the attack. This is accomplished typically by putting a capacitor in parallel with the plate resistor(s) which rolls off around a few kHz. This preserves the treble boost in the upper midrange but softens the attack. I believe the SLO100 was one of the first amps to do this. You can see this in the Axe-Fx II as your Triode Freq parameters. You can soften the JCM800 attack by lowering the Triode Freq values. Most modern hi-gain designs use some form of HF rolloff like this. Another reason is that JCM800s use relatively low amounts of negative feedback (which is why they're so loud). This causes a treble boost in the power amp. Increase the Damping parameter to increase the negative feedback." [http://forum.fractalaudio.com/threads/cliff-how-can-i-ever-have-doubted-you.63107/#post-781950]
# "Those amps are all designed to get their character from power amp distortion. If you don't push the power amp all you are hearing is the preamp which is voiced to be trebly. The power amp then compresses the highs and the sound gets fatter." [https://forum.fractalaudio.com/posts/1235311]
# "It's a vertical input Canada export version. I went through several before settling on this one as it was the best sounding by far." [https://forum.fractalaudio.com/threads/jcm-800-question.103215/#post-1235691]
# (about moving Master volume to the post phase inverter) "It's called PPI MV or the "Lar-Mar Mod"." [http://forum.fractalaudio.com/threads/dial-in-popular-mods.119757/#post-1424257]
# "At low MV the source resistance into the PI is low which raises the highpass frequency due to the coupling cap and raises the lowpass frequency due to the Miller capacitance and snubber. As you increase the MV the source resistance increases which decreases both of these things. As you keep raising the MV the source resistance then starts to decrease as you get above 50% of the pot value." [http://forum.fractalaudio.com/threads/setting-the-master-volume.119903/page-2#post-1428935]
# "Some of them are really dull. We have two 50 watters. One is a Canadian export with bat-handle switches and sounds glorious. All nasty and spitty and full of "artifacts". The other is a "regular" one with the rocker switches. It sounds like it has a blanket over it in comparison. Our model is based on the Canadian one. Oh, and I should add that someone removed the bright cap from the Canadian one. Probably because it's so nasty with it in. I installed a new one to bring it back to it's original glory. The key to JCM800's is to crank the MV to overcome the brightness of the preamp." [http://forum.fractalaudio.com/threads/help-requested-new-afx-xl-and-digital-distortion-in-the-sound.123815/page-2#post-1478884]
# "Our reference amp had the bright cap removed by a previous owner. I put it back in. I like it on, even with a bright guitar." [http://forum.fractalaudio.com/threads/jcm800-with-our-without-bright-switch.131049/#post-1552301]
# "When modding Marshalls for higher gain sometimes the modder will decrease the input frequency response to reduce noise and fizziness. You can do this by reducing the high-cut frequency in the input EQ. Or you can use a high-shelf filter which is a little more subtle. Another technique is to put a capacitor across the second-to-last triode stage. This is the "Triode 1 Plate Freq" parameter. Reduce this to around 2 kHz to start which is typical of amps like an SLO100, etc." [https://forum.fractalaudio.com/threads/dialling-in-the-marshalls.143682/post-1707222]
# "The reference amp used for our model is a Canadian Export version (with the "bat handle" power switches). We have two JCM800s and this particular amp sounds way better than the regular one with the rocker type power switches. It's not as harsh with a warmer high end." [https://forum.fractalaudio.com/threads/nux-mg300-vs-fm3-comparison.165102/post-1980841]
# "We have two of them. One sounds amazing, the other not so much. The model is based, naturally, on the amazing sounding one." [https://forum.fractalaudio.com/threads/buttons-functioning-as-on-amps.170531/post-2052806]
# "JCM800s sound better with a hot bias IMO. The problem is the plate voltage is too high so when you set the bias higher the dissipation goes up and tube life is shortened. IMO they should've made the plate voltage around 420V. That would allow a hotter bias with longer tube life at the expense of slightly less volume but JCM800s are ungodly loud anyways so..." [https://forum.fractalaudio.com/threads/why-your-amp-doesnt-sound-like-our-amp.172907/post-2091305]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-800-and-brit-800-mod-jcm-800.111876 Yek's write-up]

==BRIT 800 2204 LOW==

==BRIT 800 2203 HIGH (100W Marshall JCM 800 2203 JMP)==

[[file:JCM8002203.jpg|300px]]

Model:
* Single channel, low and high inputs

[[Cabinet models list | Cab:]] Marshall 4x12 (G12M)

Presence, Bass, Middle, Treble, Master Volume, Pre-Amp Volume

Cliff's 2203 is an unmodified unit with metal toggle switches and faded brown grille cloth. It has vertical inputs and drake transformers.

Power tubes: EL34

# "It's a vertical input model." [https://forum.fractalaudio.com/threads/marshall-jmp-100w.198803/post-2481704]
# [https://forum.fractalaudio.com/threads/marshall-jmp-100w.198803 Forum discussion]
# [https://wiki.fractalaudio.com/wiki/images/0/05/JCM8002203.jpg Picture of the modeled amp]

==BRIT 800 2203 LOW==

==BRIT 800 #34 (50W Marshall JCM 800 with virtual Santiago #34 modifications)==

[[File:Logo small.png]]

Custom Fractal Audio model

Notes: see Brit 800

Power tubes: EL34

# "Based on the “Santiago #34” modifications."
# "The Brit 800 #34 does a better Slash than the AFS100 IMO. The AFS100 models are based on the actual amp but I think my version of #34 sounds more like AFD. I based the model on information I've collected over the years about the mods that were done." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-00-firmware-release.124944/page-5#post-1486357]
# "The Brit 800 #34 has a ton of treble boost and will squeal with certain guitars and/or certain IRs and/or certain types of amplification. Nature of the beast. No other amp has anywhere near the amount of treble boost. The AFD100 amp that Marshall produced years later (that was supposed to be a #34 copy) has nowhere near the amount of treble boost and has a huge snubber cap on the PI (which rolls off the treble). My gut tells me that they did this because they feared there would be too many reports of pickup squeal (or the amps would be too unstable at high gain)." [http://forum.fractalaudio.com/threads/squealing-like-mad.132058/#post-1563723]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-800-and-brit-800-mod-jcm-800.111876 Yek's write-up]

==BRIT 800 MOD (50W Marshall JCM 800 with virtual modifications)==

[[File:Logo small.png]]

Custom Fractal Audio model

Notes: see Brit 800

Power tubes: EL34

# "Based on popular modified Marshall JCM800. These mods make the amp “heavier” and less strident."

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-800-and-brit-800-mod-jcm-800.111876/#post-1338002 Yek's write-up]

==BRIT AFS100 1 (Marshall AFD100SCE)==

[[file:AFD.jpg|300px]]

Models:
* Amp in mode "#34"
* Amp in mode "AFD"

[[Cabinet models list |Cab:]] Marshall 4x12 (V30)

Gain, Bass, Middle, Treble, Presence, Master, #34/AFD switch, Depth (Brit Super model only)

Power tubes: 6550

# "I have an actual Slash signature model and spent a lot of time measuring, listening and comparing." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-2-01-firmware-release.111657/page-8#post-1337247]
# "The Brit 800 #34 does a better Slash than the AFS100 IMO. The AFS100 models are based on the actual amp but I think my version of #34 sounds more like AFD. I based the model on information I've collected over the years about the mods that were done." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-00-firmware-release.124944/page-5#post-1486357]
# "The Brit 800 #34 has a ton of treble boost and will squeal with certain guitars and/or certain IRs and/or certain types of amplification. Nature of the beast. No other amp has anywhere near the amount of treble boost. The AFD100 amp that Marshall produced years later (that was supposed to be a #34 copy) has nowhere near the amount of treble boost and has a huge snubber cap on the PI (which rolls off the treble). My gut tells me that they did this because they feared there would be too many reports of pickup squeal (or the amps would be too unstable at high gain)." [http://forum.fractalaudio.com/threads/squealing-like-mad.132058/#post-1563723]
# "The amount of treble peaking needed for an amp at a given drive is highly dependent on the guitar. For example my guess is that the AFD100 was designed around a Les Paul. With my Suhr it's much too bright because that's a very bright guitar. So one of the first things I do with the AFS100 model is turn down the bright cap a bit." [https://forum.fractalaudio.com/threads/firmware-1-11.140004/page-2#post-1660177]
# "Reference amp is a Slash AFD100 Signature Special Collector's Edition #76. Hand-signed by Slash with COA." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-19-00-beta-3.180388/post-2207142]
# "Default MV is quite high in that model which will mask the effect of the Presence control since the power amp is distorting heavily (I find that amp sounds best with the power amp driven hard). Turn the MV down and you'll notice the Presence control will have much more effect." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-00.189017/post-2343032]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-afs100-and-brit-super-marshall-afd100.111919/ Yek's write-up]

==BRIT AFS100 2==

==BRIT BROWN (custom model, producing the Plexi "Brown Sound")==

[[File:Logo small.png]]

Custom Fractal Audio model

[[Cabinet models list | Cab:]] Marshall 4x12 (G12M, G12H, G12-EVH, V30, JBL D120)

Power tubes: EL34

# "The Brit Brown was built by ear." [https://forum.fractalaudio.com/threads/evhs-original-plexi-and-the-fas-brit-brown-amp.81986/#post-995265]
# "Brit Brown is my personal take on what the ultimate "Brown" plexi should sound like. It's based on a 100W SLP with Arredondo mods and a few little voicing tweaks." [https://forum.fractalaudio.com/posts/1152917]
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]
# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-brown-and-fas-brown.111974/ Yek's write-up]

==BRIT JM45 (Marshall JTM 45)==

[[file:JTM.png|300px]]

Models:
* Treble (High) channel
* Normal and Bright channels jumpered

[[Cabinet models list |Cab:]] Marshall 4x12 (G12M, G12H)

Volume Normal, Volume High Treble, Bass, Middle, Treble, Presence

Power tubes: EL34

# "They had no Master Volumes so people rarely got the Drive past 3.00 since it would melt your face. Without the specter of having your skin flayed off as is afforded by a model of the amp, the temptation is to turn the Drive way up. When you do this the low notes get very muddy. Single notes can form an almost perfect square wave which will sound like a synthesizer." [http://forum.fractalaudio.com/threads/jm45-and-jm45-jump-sound-horrible-for-low-e-and-a-strings-not-a-bug.76286/#post-931633]
# "Our reference amp has a 100 pF bright cap. Many JTM45s did not but I think they sound better with one. A JTM45 with a bright cap is similar to a Superlead. If you want the Channel 1 sound with an Axe-Fx use the Brit JM45 Jump model and turn the Treble Drive knob all the way down." [http://www.thegearpage.net/board/index.php?threads/fractal-vs-helix-the-comparison-series-made-by-yours-truly.1757067/page-2#post-22868763]
# "When modding Marshalls for higher gain sometimes the modder will decrease the input frequency response to reduce noise and fizziness. You can do this by reducing the high-cut frequency in the input EQ. Or you can use a high-shelf filter which is a little more subtle. Another technique is to put a capacitor across the second-to-last triode stage. This is the "Triode 1 Plate Freq" parameter. Reduce this to around 2 kHz to start which is typical of amps like an SLO100, etc." [https://forum.fractalaudio.com/threads/dialling-in-the-marshalls.143682/post-1707222]
# "The very first models used a 5881, after that KT66 then EL34." [https://forum.fractalaudio.com/threads/jtm45-bug.164255/post-1969445]
# (negative feedback) "I've seen JTM45s with 27K off the 16-ohm tap. That's a lot of feedback. In this case you would then double the feedback on top of the 3.3 so 9.9 or so." [https://forum.fractalaudio.com/threads/negative-feedback.188769/post-2340464]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-jm45-marshall-jtm-45.112030/#post-1339718 Yek's write-up]

==BRIT JM45 JUMPED==

==BRIT JVM OD1 GREEN (Marshall JVM410H)==

[[file:jvm.png|300px]]

Models:
* OD1 Green
* OD1 Orange
* OD1 Red
* OD2 Green
* OD2 Orange
* OD2 Red

[[Cabinet models list |Cab:]] Marshall 4x12 (V30 and G12H)

Master, Bass, Middle, Treble, Gain, Presence, Resonance, Reverb (not modeled)

Power tubes: EL34

# "IMO, the reason the JVM sounds good is the plate cap on the second-to-last triode. That smooths out the tone considerably. The second-to-last triode is associated with "Triode 1 Freq" in the advanced parameters. You can adjust this to simulate adding a cap to the plate. The other thing that helps the tone is the 220K plate resistor on the last triode. This shifts the bias point down vs. a "classic" Marshall. Unfortunately the bias points aren't exposed to the user." [https://forum.fractalaudio.com/threads/holy-crap-the-new-jvm-sounds-great.44628/#post-588030]
# "The JVM has a huge plate resistor on the cathode follower, the JS does not." [https://forum.fractalaudio.com/threads/jvm-sounding-weird.150157/page-2#post-1785256]
# (about OD 1 Orange and Red compression):
#* "Real amp does this. Poor cathode follower design."
#* (why doesn't this happen with the Green channel) "Because the Green channel only has one tone stack hanging off the cathode follower."
#* (why doesn't this happen with the OD2 channels) "OD1 has a different tone stack. The gains are the same. The models are very accurate." [https://forum.fractalaudio.com/threads/jvm-410-model-issue.156087]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-jvm410-marshall-jvm410.112092/ Yek's write-up]

==BRIT JVM OD1 ORANGE==

==BRIT JVM OD1 RED==

==BRIT JVM OD2 GREEN==

==BRIT JVM OD2 ORANGE==

==BRIT JVM OD2 RED==

==BRIT PRE (Marshall JMP-1 preamp)==

[[image:Cliff JMP-1.jpg|300px]]

Model:
* OD channel

Volume, Gain, Bass, Mid, Treble, Presence, Bass Shift (not modeled)

Power tubes: EL34

# "The two channels have preset tone stacks. Then there is a digitally controlled 4-band graphic EQ which is the B/M/T and Presence. This technique gets around the problem of trying to digitally control a tone stack. The Triaxis uses LDRs in place of potentiometers. The Soldano X-99 uses motorized pots. Both techniques being expensive. So the JMP-1 uses a fixed tone stack and then a digitally controlled graphic EQ. The Axe-Fx model of the JMP-1 is "better" in the sense that the tone controls control the tone stack rather than a graphic EQ. You then have the separate graphic EQ to further tailor the sound. What I didn't do, and why people probably feel the model differs, is "normalize" the tone controls so that with B/M/T at noon the tone stacks match. On the Axe-Fx you might need to set the Bass to 3, Mid to 7, etc. to get the tone to match. I just used a standard Marshall tone stack whereas the JMP-1 uses a standard Marshall tone stack but the pots are replaced with fixed resistors but those values don't necessarily correspond to the pots at noon." [https://forum.fractalaudio.com/posts/1228348]
# "The JMP-1 tone controls have more range than the actual preamp. The preamp has about +/- 8 dB for each tone control while the model has the standard +/- 12 dB."
# "Brit Pre is a legacy model from the original Axe-Fx. It's not as accurate but some people really liked it so we kept it and created new models for the Ares/Cygnus platform." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-19-02-public-beta.181521/post-2224791]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-pre-and-brit-jmpre-1-marshall-jmp-1.112139/ Yek's write-up]

==BRIT SILVER (100W Lerxst Omega / Marshall 2555 Silver Jubilee)==

[[file:Lerxst.jpg|300px]]

Model:
* Lead channel

[[Cabinet models list |Cab:]] Marshall 4x12 (V30)

Presence, Bass, Middle, Treble, Gain, Master

Power tubes: EL34

# "Our reference amp for the Silver Jubilee is actually not a Silver Jubilee. It's a Lerxst Omega that Alex Lifeson gave me." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-5-cygnus-firmware-public-beta-2.170901/post-2058221]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-silver-marshall-silver-jubilee.112184 Yek's write-up]

==BRIT STUDIO 20 (Marshall SV20H)==

Model:
* Marshall Studio Vintage 20 (20W version of 1959 Super Lead Plexi)

Notes: see 1959SLP

Power tubes: EL34

# "The schematic doesn't show it but there's a cathode bypass cap on one of the triode stages." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2320134]
# "It's a cool little amp. It's very loud though. It's not really a "bedroom amp" IMO. Good for smaller gigs, rehearsals, etc." [https://forum.fractalaudio.com/threads/comparing-brit-20-to-real-sv20h-anyone-done-it.188338/post-2336176]

==BRIT SUPER (Marshall AFD100 schematics)==

[[file:AFD.jpg|300px]]

Model:
* Marshall AFD100 in AFD mode

Notes: see Brit AFS100

Power tubes: EL34

# "Brit Super model is based on the Marshall AFD100." [https://forum.fractalaudio.com/threads/great-sound-with-my-splawn-nitro-4cm-im-blown-away.55549/#post-700713]

==BUDDAH DUOMASTER (Budda Twinmaster)==

[[File:Logo small.png]]

Model:

* Single channel

[[Cabinet_models_list|Cab]]: 1x15 Budda Phat 15 or 1x12 Budda Phat 12

Bass, Treble, Volume

Power tubes: EL84

# "I bought a Budda Twinmaster, pulled it apart and traced the circuit since I couldn't find a schematic for it anywhere. Funky amp. Paraphase phase inverter. Weird Bridge-T sorta tone stack. I'm convinced the feedback is connected to the wrong node but I quadruple-checked and my schematic is definitely correct. I think it was probably a mistake but then they said "Hmmm, but it sounds good so don't fix it"." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-12-cygnus-firmware-public-release-candidate.172027/post-2075782]
# "The Buttery model was REPLACED by a Budda Twinmaster model. Totally different model." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-12-cygnus-firmware-public-release-candidate.172027/post-2076481]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-buttery-budda-twinmaster.112228/ Yek's write-up]

==CA3+ CLEAN (Custom Audio Amplifiers 3+ SE preamp)==

[[file:CAE.png|300px]]

Models:
* Clean channel
* Rhythm channel
* Lead channel

Gain, Bass, Middle, Treble, Master, Bright switch. Active tube EQ: Treble and Bass

Power tubes: EL34

# "The CA3+SE model is basically an OD100." [https://forum.fractalaudio.com/threads/is-the-suhr-od-100-in-the-axe.75090/#post-918169]
# "An OD100 is the head version of a CAE 3+."
# "That's a "James" tone-stack. You can find simulations on-line but typically you would get close using shelving filters with frequencies of 100 and 1000 Hz." [http://forum.fractalaudio.com/threads/cae-3-se-global-eq-anybody-know-the-freqs.33103/#post-461976]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-ca3-cae-3-se.112399/ Yek's write-up]

==CA3+ LEAD==

==CA3+ RHYTHM==

==CAMERON CCV 1A (Cameron CCV-100)==

[[file:ccv.jpg|300px]]

Models:
* (1A) Channel 1, less gain
* (1B) Channel 1, more gain
* (2A) Channel 2, Bright1 switch left, Bright2 switch left, Gain Style switch left
* (2B) Channel 2, Bright1 switch left, Bright2 switch right, Gain Style switch left
* (2C) Channel 2, Bright1 switch left, Bright2 switch left, Gain Style switch right
* (2D) Channel 2, Bright1 switch left, Bright2 switch right, Gain Style switch right [https://forum.fractalaudio.com/threads/just-a-heads-up.97371/#post-1168902]

Channel 1: Punch (= Resonance / Depth), Presence, Master, Bass, Middle, Treble and Gain, 3-way Voicing switch (resonance), 3-way Dark switch (presence), 3-way Gain Style switch (“Jose Master” gain/clipping), 3-way Bright switch (less noticeable at higher gain settings)

Channel 2: Punch (= Resonance / Depth), Presence, Solo Master, Master, Bass, Middle, Treble, two Gain controls, 3-way Gain Style switch, two Bright switches, Drive switch

The 2C and 2D models have lower output because of the Sat switch position.

Power tubes: EL34

# "The amp was modeled with the Voicing switch in the middle position. The "Dark" switch is the Negative feedback control. Set Negative Feedback to 3.6 to reproduce the switch in the middle position. Set it to 9.8 to reproduce the switch in the right position. 5.0 for left position (default). The amp has a dozen switches and, frankly, there isn't a lot of difference between some of the settings. The Drive switch sounds virtually identical whether left or right. I don't like it in the middle." [https://forum.fractalaudio.com/threads/just-a-heads-up.97371/#post-1168912]
# (about the Drive knob) "Our reference amp has a linear taper pot so the behavior is very abrupt. The model matches the amp extremely accurately (as do all G3 models)." [https://forum.fractalaudio.com/threads/fw-18-01-camron-ccv-not-a-bug.97385/#post-1168811]
# "It's a bit of a quirky amp and kind of a one-trick pony but, man, what a trick." [https://forum.fractalaudio.com/threads/fw-18-01-camron-ccv-not-a-bug.97385/#post-1168922]
# "Yes, it's actually not a very high gain amp. The topology is very similar to a JCM800." [https://forum.fractalaudio.com/threads/fw-18-01-camron-ccv-not-a-bug.97385/#post-1169347]
# "The key to the CCV sound is the Sat Switch." [https://forum.fractalaudio.com/posts/1169015]
# "Camerons have linear taper MV and you need it with them because the signal level into the power amp is very low due to the Jose topology." [https://forum.fractalaudio.com/threads/mv-poll.170996/post-2059425]
# "Humans perceive high frequency thermal noise as hiss. The more gain the more hiss. Diezel's have a lot of filtering. Large grid stoppers, plate capacitors, etc. This reduces the bandwidth which lowers the hiss. Camerons are pretty much wide open. Small grid stoppers or bypass caps on the grid stoppers, no plate caps, etc." [https://forum.fractalaudio.com/threads/why-lower-gain-cameron-ccv-amp-model-feels-more-noisy-than-much-higher-gain-herbie-3.188658/post-2339783]
# "The Cameron is a genuine Cameron. I don't know the lineage of the Atomica." [https://forum.fractalaudio.com/threads/are-any-of-the-cameron-models-of-mark-cameron-built-amps.199792/#post-2489827]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-cameron-ccv.112486/ Yek's write-up]

==CAMERON CCV 1B==

==CAMERON CCV 2A==

==CAMERON CCV 2B==

==CAMERON CCV 2C==

==CAMERON CCV 2D==

==CAPT HOOK 1A (Hook Captain 34)==

[[file:capt34.jpg|300px]]

Models:
* (1A) Channel 1, EQ Bypass switch OFF, Boost switch OFF
* (1B) Channel 1, EQ Bypass switch engaged (no Bass / Middle / Treble), Boost switch ON
* (2A) Channel 2, Edge switch OFF
* (2B) Channel 2, Edge switch ON
* (3A) Channel 3, Edge switch OFF
* (3B) Channel 3, Edge switch ON

[[Cabinet models list |Cab:]] Hook 2x12 or 4x12 (V30, G12H, G12-65, WGS)

Channel 1: Gain (with Pull function), Level, Bass, Mid, Treble, Boost switch (not modeled), EQ bypass switch, Bright switch. Shared: Presence and Balls

Channels 2 and 3: Gain, Level, Bass, Mid, Treble, Boost switch, Edge switch (changes tone stack). Shared: Presence and Balls

Power tubes: EL34

# "This amp uses a mu follower which yields a complex distortion with smooth decay. To simulate the Boost switch use the Boost switch in the amp block as it has the same amount of gain." [https://forum.fractalaudio.com/posts/1426113]
# "A mu follower is similar to a cascode configuration except the output is off the cathode instead of the plate. So the output impedance is lower." [http://forum.fractalaudio.com/threads/the-hook.120307/#post-1432379]
# (mimic Pull Gain on clean channel) "Just set the Tonestack Type to Hook Clean 2." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-5-00-firmware-released.120358/page-10#post-1433059]
# "The Capt. Hook's "thing" is that it's basically a JCM800 with the cathode follower replaced by a mu-follower. A mu-follower doesn't compress and distort like a cathode follower does. This results in the amp sounding more open and smoother." [http://forum.fractalaudio.com/threads/recommended-adjustment.133602/page-2#post-1579933]
# "The Hook Clean 1 is a Fender style tonestack which has a lot more insertion loss than the others." [https://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-5-00-firmware-released.120358/page-10#post-1433058]
# "The Hook uses a "mu follower" instead of a cathode follower. Cathode followers have low output impedance but distort quite easily. Mu followers address some of the problems of cathode followers." [https://forum.fractalaudio.com/threads/dialling-in-the-marshalls.143682/page-7#post-1708218]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-capt-34-hook-captain-34.119935 Yek's write-up]

==CAPT HOOK 1B==

==CAPT HOOK 2A==

==CAPT HOOK 2B==

==CAPT HOOK 3A==

==CAPT HOOK 3B==

==CAR ROAMER (Carr Rambler)==

[[file:rambler.jpg|300px]]

Model:
* Single channel

[[Cabinet models list |Cab:]] Carr 1x12 (Eminence Elsinore)

Volume, Treble, Middle, Bass, Pentode/Triode (not modeled), Reverb (not modeled), Tremolo

Power tubes: 6L6

# "It's basically a Deluxe Reverb preamp with a cathode bias 6L6 power amp and no negative feedback. Sort of a Fender-meets-Vox thing." [https://forum.fractalaudio.com/threads/carr.78974/#post-960532]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-car-roamer-carr-rambler.112529/ Yek's write-up]

==CAROL-ANN OD-2 (Carol-Ann OD-2)==

[[file:od2.jpg|300px]]

Model:
* Overdrive channel

Master, Pre Gain, Drive, Bass, Middle, Treble, Presence, Sparkle (not modeled), Shift switch (not modeled)

Power tubes: 6L6

# "CAs are definitely dark amps. Sound great though." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-10-cygnus-firmware-public-beta-7.171198/post-2066490]
# "If you like the base Dumble sound but want a little more gain without the fuzziness of a Fuchs try the Carol-Ann models." [https://forum.fractalaudio.com/threads/fuchs-ods-in-cygnus.172291/post-2081523]

Alan Phillips:
# "In the real world the OD2 is very very fussy on speaker choice too. The real world speakers of choice are EVM12L in a 1x12 rear ported and 2x12 with Celestion Classic Lead 80's. I found the 12L emulation did a pretty good job. Some of the others sounded so artificial with that model. Like a Rockman. Coupled with the right cab the emulated model does a good job of representing the basic tonal signature of the amp".
# "It's not a competitive model, it's a live demo of an OD2 as tweaked by me. Damn sight better than sound clips for auditioning to guys that haven't got the ability to get to a Dealer. Clearly it doesn't give you the full experience of the full amp, but is a good tonal taster. I repaired a Soldano SLO for him one day and when he came over my house to pick it up we just decided it would be a good idea to put a CA model in there. Having the actual builder involved kind of closes the loop fully. I'm happy to endorse that model because I put a lot of hours testing it and putting together a ton of technical information, fourier analysis graphs, frequency response graphs, schematics etc that would make validation of a mathematical model much easier. In reality even though the power amp and the preamp are modeled the pre-amp got the most effort. As I said in another thread, I tuned that by putting the axe in to the actual power amp of an OD2 and running that side by side with a full OD2. The final tweaks were made like that using parametric eq blocks that were hard coded in to the model. You could call that the icing on the cake and basically put the same level of tuning into the model as I do with a actual OD2. The only difference was I was using a GUI, not resistors and capacitors."
# "The OD2 and to some degree the OD3 uses HRM style gain staging with a Plexi PI and power amp. Thats common knowledge, I've talked about it in depth many times. I really liked the idea of driving the tonestack from a common cathode stage as opposed to a cathode follower like a Marshall because it got rid of some of the artifacts I don't like with say a JCM-800. Yes that's something that Dumble came up with that I have to give him major props for. I wanted an amp that would have a little more gain than a JCM-800 but with the character of a Plexi without any fizz or harsh upper mid/lower treble frequencies. Remember this was BEFORE anyone had even degooped or documented a Bluesmaster style circuit and the only thing Shad was building was his post count at AmpGarage asking about Dumble circuits. I do find it amazing it took other guys years to catch on with moving the pots to the front. It does require a bit more thought than just moving the pots as the ranges of those trimmers Dumble used is impractical when used as front panel controls (which they were not really intended to be). I do also agree with you that from a pure tone standpoint having nothing on the front panel is always going to be better. The JB100 model is basically an OD2 with the entire OD circuit on the board with predefined filters made up of quality components without adjustment through fragile trimmers. The OD2 was never designed to be put side by side in a Dumble clone fest in some guys living room with everyone playing their best Ford licks, it was designed to be used on stage for guys who played in cover/blues/wedding/classic rock bands. The seperate eq and the tube driven effects loop were added for that situation. I have always tried to avoid that association as much as possible because the average Dumble lover is typically looking for a particular set of tones that may or may not be found in this amp. Early customer interaction with guys like yourself made me want to make sure people knew it was not a tonal clone of a Dumble to avoid returns/misunderstandings. The OD-2 is not the best amp for those tones, I totally agree with you, but a Dumble or clone doesn't really do fast dampened power chords like the OD-2 will do either. On the other hand, it is much more suited for blues and classic rock, not the Ford/Carlton thing. Bear in mind that its function and tone that the average player is looking for, not a particular design architecture. The fact I did use an HRM style circuit obviously (and unfortunately) placed me in the Dumble category. However, 2500 amps later its not really seen that way any more as the CA's have always had their own thing going on tonally that is very much more in a modified Marshall vein. The newer models like the Triptik 2 have absolutely nothing in common with any Dumble, not even a common cathode driven tonestack. For anyone that has played a number of real Dumbles, there is a certain thing (I hear it more in the clean channel) that is uniquely his signature. There's a certain swirl to the clean tone that is always present in his amps. However the amp doesn't overdrive anywhere close to like what I like when pushed hard. For me I would rather focus on that tone in a Plexi Marshall, but who knows what the original guy he modified this for wanted. All of this hopefully explains why I have always shied away from the Dumble comparison thing, I was truly and honestly never trying to clone a Dumble." [https://www.thegearpage.net/board/index.php?threads/fuchs-ods-classic-whats-the-word.1845787/page-4#post-24506473]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-ca-od-2-carol-ann-od2.112259 Yek's write-up]

==CAROL-ANN TRIPTIK CLASSIC (Carol-Ann Triptik)==

[[file:triptik.jpg|300px]]

Models:
* Clean channel
* Classic channel
* Modern channel

[[Cabinet models list|Cab:]] Carol-Ann 1x12 (Scholz Classic)

Input Level, Drive on channels 2 and 3, Bass, Middle, Treble, Presence, Master, Classic/Modern voicing switching

Power tubes: EL34

# "This TripTik is badass. Dumble meets Marshall with a sprinkle of 5150 power amp." [https://forum.fractalaudio.com/threads/since-10-06-came-out.70996/#post-870346]
# "I think what people like about this amp is the same reason people like the BE/HBE. These amps share the same aggressive low-cut on the input and then add bass back in the power amp. This gives clear bass response without getting flubby."
# (speaker) "It's a Scholz Classic." [https://forum.fractalaudio.com/threads/axe-fx-ii-firmware-15-00-released.87350/page-7#post-1057172]
# "Some amps have a fixed depth circuit, e.g. 5153, Freidman BE/HBE, Dirty Shirley, TripTik, Tucana, et. al. In these cases the Depth knob will default to a value that corresponds to the fixed circuit." [https://forum.fractalaudio.com/threads/lets-talk-about-the-depth-control.88747/#post-1071598]
# "CAs are definitely dark amps. Sound great though." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-10-cygnus-firmware-public-beta-7.171198/post-2066490]
# "If you like the base Dumble sound but want a little more gain without the fuzziness of a Fuchs try the Carol-Ann models." [https://forum.fractalaudio.com/threads/fuchs-ods-in-cygnus.172291/post-2081523]

Alan Phillips from Carol-Ann:
# (Classic mode): "On the real amp, you would set the Input level at 2 O'clock and the Gain at 1 to 2 O'clock to get a great classic rock rhythm tone. It's not overly different in character to the modern setting, less gain and less low end essentially."
# "It does classic rock extremely well and has one of the best clean channels I've ever designed." [https://www.thegearpage.net/board/index.php?threads/carol-ann-od2r-the-best.1908068/#post-25776544]

[https://forum.fractalaudio.com/threads/fractal-audio-amp-models-ca-triptik-carol-ann-triptik.112303/ Yek's write-up]

==CAROL-ANN TRIPTIK CLEAN==

==CAROL-ANN TRIPTIK MODERN==

==CAROL-ANN TUCANA CLEAN (Carol-Ann Tucana 3)==

[[file:tucana.jpg|300px]]

Models:
* Clean channel
* Lead channel

Input Level, Bass, Mid, Treble, Gain (Overdrive channels), Master (all channels), Presence

Power tubes: KT88

# "One of the best amps in the world IMO. I have a Dumble and a Trainwreck and various other boutique amps and the Tucana is better than all of them." [https://forum.fractalaudio.com/posts/1153214]
# "Some amps have a fixed depth circuit, e.g. 5153, Freidman BE/HBE, Dirty Shirley, TripTik, Tucana, et. al. In these cases the Depth knob will default to a value that corresponds to the fixed circuit." [https://forum.fractalaudio.com/threads/lets-talk-about-the-depth-control.88747/#post-1071598]
# "CAs are definitely dark amps. Sound great though." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-10-cygnus-firmware-public-beta-7.171198/post-2066490]
# "If you like the base Dumble sound but want a little more gain without the fuzziness of a Fuchs try the Carol-Ann models." [https://forum.fractalaudio.com/threads/fuchs-ods-in-cygnus.172291/post-2081523]

Carol-Ann:
# "Now I can only speak for the actual amp, but my preference of speaker is a Celestion Creamback 65, though I gig these regularly with a 2x12 with Celestion T75's. Its pretty forgiving on speakers compared with some models. The foot controller and bias monitor are two of the wonderful features of the actual amp, but are both moot in the model......unless Cliff wants to model the effects of real world mains power fluctuations from place to place, but the 'green zone' of the bias monitor is 62-65% plate idle dissipation power and it measures and compensates for plate voltage and screen power , which means the real amp runs best at a slightly cooler bias. The bias monitor just allows you to set that consistently from venue to venue regardless of the main power." [https://forum.fractalaudio.com/posts/1035178]
# "It's very very difficult for anyone to get a bad tone out of the real amp. It's designed that way, the range and limits on the controls, even the biasmon system makes it difficult for even a very inexperienced player to FU. The real amp has a more British overtone to it due to the fact I am British and I designed it. The gain staging, overdrive voicing and output stage are night and day to ANYTHING Mesa, any owner of the real amp would attest to that." [https://forum.fractalaudio.com/posts/1049358]
# "The Tuc 3 is very very tolerant of most cabs and speakers, unlike say the OD2. I feel people need to approach this model very simply. Don't mess with extended parameters, basically don't try and redesign it. Use a reliable Celestion based cabinet model. I have a fantastic 4x12 with 2 old greenbacks and two old v30s that is the best cab I've played the real amp through. In actual levels of gain with the two adjustable gain controls, the amp has a maximum gain level very similar to the Triptik, the setting of these two controls with respect to each other is critical." [https://forum.fractalaudio.com/posts/1049367]
# "Real world, it has the same amount of actual gain as the Triptik. Way more than most people would need for recording or live playing. Input gain on 10 o clock, gain on 2 o clock is a 70s /80s lead tone, put the input level up to 2 o click and it's a very sustained lead tone or a very modern heavy rhythm tone." [https://forum.fractalaudio.com/posts/1049530]
# "You don't need to crank the real amp to get a ton of overdrive. I actually designed the original for myself and I play in a rock cover band. There's nowhere I would ever be able to get the amp to the point of pushing the power tubes in to overdrive. You gain stage a design based on its application. For a design that needs a lot of overdrive at a low volume, you do most of that and the harmonic makeup in the preamp. The Tucana falls in to this category. The master volumes in a 500 seat club rarely get above 10 O Clock on the real amp and at that point there's still tons of clean headroom left. Of course the power amp adds to the harmonic content, but it adds very little overdrive. Another interesting point to note is that the Tucana has a high pass filter in the power amp feedback loop, which gives you a nice tight low end because the bass is subjected to more gain. For an amp designed to be pushed hard in to power tube overdrive, this should be omitted as all bets are off in the feedback loop when you hit the rails. In other words that filter requires headroom to function properly, as does the presence control of any amp where it's a component of the feedback loop." [https://forum.fractalaudio.com/posts/1050147]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-ca-tucana-carol-ann-tucana-3.112349/ Yek's write-up]

==CAROL-ANN TUCANA LEAD==

==CITRUS A30 CLEAN (Orange AD30HTC)==

[[File:ad30.jpg|300px]]

Models:
* Clean channel
* Dirty channel

[[Cabinet models list |Cab:]] Orange 2x12 (V30)

Gain, Master, Bass, Middle, Treble

Power tubes: EL84

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-citrus-a30-orange-ad30htc.112584 Yek's write-up]

==CITRUS A30 DIRTY==

==CITRUS BASS 200 (Orange AD200B bass amp)==

[[file:orangebass.jpg|300px]]

Model:
* Single channel

[[Cabinet models list |Cab:]] Orange bass cab

Volume, Gain, Bass, Middle, Treble

Power tubes: 6550

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-citrus-bass-200-orange-ad200b.112631/ Yek's write-up]

==CITRUS RV50 (Orange Rockerverb 50 MK II)==

[[File:rockerverb50.jpg|300px]]

Model:
* Dirty channel

[[Cabinet models list | Cab:]] Orange 4x12 (V30)

Dirty channel: Volume, Gain, Treble, Middle, Bass, Reverb (not modeled)

Power tubes: EL34

# "The model is based on a MKII." [https://forum.fractalaudio.com/posts/1109941]
# "The power amp in a Rockerverb has very little negative feedback so it will boost the highs more than most power amps." [https://forum.fractalaudio.com/threads/sorting-out-the-high-end.117233/#post-1398890]
# "It's not a super high gain amp. It's called a Rockerverb not a Metalverb. It's only got four gain stages and there's significant padding between stages." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-12-cygnus-firmware-public-release-candidate.172027/post-2077006]
# (Gain) "It's a ganged pot so it behaves strangely." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-16-01-beta-1-public-beta.172736/post-2088693]
# "That amp doesn't have a high cut." [https://forum.fractalaudio.com/threads/hi-cut-control-on-citrus-rv50-not-working.178740/post-2178756]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-citrus-rv50-orange-rockerverb-50-mk-ii.112668/ Yek's write-up]

==CITRUS TERRIER (Orange Tiny Terror)==

[[File:tinyterror.jpg|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Orange 1x12 or 2x12 (G12H)

Volume, Gain, Tone (High Cut), 7w/15w switch (not modeled)

Power tubes: EL84

# "The actual amp has no tone stack and a single tone control. The tone control is actually a high cut control in the power amp and is therefore replicated by the Hi Cut parameter."
# "It's inaudible when clean." [https://forum.fractalaudio.com/posts/1063208]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-citrus-terrier-orange-tiny-terror.112702/ Yek's write-up]

==CLASS-A 15W TB (Vox AC15 Top Boost)==

[[file:ac15.jpg|300px]]

Model:
* Top Boost channel

[[Cabinet models list | Cab:]] Vox 1x12 (G12M, Alnico)

Volume, Cut, Bass, Treble

Power tubes: EL84

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-class-a-15w-tb-vox-ac-15.112743/ Yek's write-up]

==CLASS-A 30W (Vox AC30 Hand-Wired)==

[[file:ac30.jpg|300px]]

Models:
* AC-30: Normal channel of AC30HW
* AC-30 Bright: Normal channel, Brilliance input
* AC-30 Hot: Top Boost channel of AC30HW, in "Hot" mode (no Bass / Treble)
* AC-30 TB: Top Boost channel of AC30HW, in "Cool" mode

[[Cabinet models list | Cab:]] Vox 2x12 (Alnico, G12M)

Volume, Bright switch (Normal channel), Treble/Bass (Top Boost channel), Hot/Cool switch (Top Boost channel), Tone Cut, Master

Power tubes: EL84

# "Note that the particular AC-30 used for the model has this scratchy high end. (...) It's a hand-wired version and that can lead to this type of sound as the parasitics cause boosting of the very high frequencies when the amp is driven hard." [https://forum.fractalaudio.com/posts/970333]
# "I intentionally limited the midrange notch since, IMO, it's a design flaw in that tone stack. But you can recover that behavior by setting the Mid control fully CCW. Modern AC30's don't have this flaw. They use a Fender-style tone stack with a fixed mid resistor."
# "The bright cap value is normalized to a Drive pot of 1M. An AC30 has a 500K pot so the value will read out as half the actual value. IOW, it's displaying 60 pF which is equivalent to 120 pF." [https://forum.fractalaudio.com/posts/1064264]
# "The Hot model models the AC-30HW model set to Hot. This bypasses the EQ for more gain. For authenticity, leave all tone controls at noon."
# "AC30's have no negative feedback on the power amp. This means the output voltage follows the speaker impedance. Therefore you get a boost at the low frequency resonance of the speaker which causes the low end to get loose when you crank it." [http://forum.fractalaudio.com/threads/crunchy-ac-30-tb-need-some-help-tightening-up-the-low-end.117675/#post-1404022]
# "AC-30's have a poorly designed cathode follower. The bias point is totally wrong and crushes one side of the signal considerably. IMO either the cathode resistor should be 100K or the plate resistor of the preceding stage should be higher, 200K. The clipping is extremely asymmetric. Too much IMO. A little asymmetry is good because it warms things up. Too much causes excessive even-order harmonics which makes things fuzzy and indistinct. The clipping is so asymmetric on an AC-30 that it's almost a half-wave rectifier. You can tweak this by adjusting the Preamp Bias point and/or lowering the Cathode Follower Compression. Or you can lower the Harmonics value which reduces the asymmetric distortion. The downside of that is that it then overdrives the phase inverter causing blocking distortion from excessive bias excursion. Another thing to try is to increase the Grid Clipping value which will add a little headroom. Start with the Bias point. AC-30's are very sensitive to the tube type and part tolerances. A tiny change in the bias point can make a big difference. The default bias point is based on Mullard ECC83 tubes. I prefer the AC-20 because it doesn't have a cathode follower so doesn't suffer from these problems. The cathode follower in an AC-30 doesn't even do all that much. Normally you use a cathode follower to preset a low-impedance source to the tone stack but the tone stack in an AC-30 doesn't present that great of a load anyways." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-02.148983/page-11#post-1767187]
# "The reference AC30 is an AC30HWHD." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-07.150305/page-6#post-1788283]
# "Our Vox models are based on a fairly new AC30HWHD head. The model matches that particular amp very well. Will it match an AC30 from a different era exactly? Probably not." [https://forum.fractalaudio.com/threads/how-accurate-is-fractals-amp-modeling.168786/post-2027668]
# "The normal channel on a Vox would be closest to the Morgan. The Brilliant channel is a "Top Boost" which means it has a tone stack and a significant midrange cut. The normal channel has no tone stack. You can't compare a a Morgan AC20 to the Brilliant channel of an AC30 and declare that one sounds better than the other. Totally different preamps and, therefore, different sound. Personally I think the AC20 is a better amp. Better made, better quality components, much better transformers. If you want that chimey AC30 sound you put an EQ before it and suck out some mids." [https://forum.fractalaudio.com/threads/how-accurate-is-fractals-amp-modeling.168786/post-2064189]
# "So-called Class-A amps (like the AC30) don't actually exhibit much power supply sag because, well, they're Class-A (or nearly). The tubes are biased hot so when one tube is conducting more the other is conducting less and the net supply current doesn't change much. Contrast this with Class-AB where when one tube conducts the other goes into cutoff causing a net increase in supply current and concomitant supply sag. What Class-A amps do exhibit is "cathode squish". The capacitor on the cathodes charges up and shifts the bias point. This reduces the gain and acts as a sort of compressor. It's a unique compression and the amp "opens up" at the same time and crossover distortion increases." [https://www.thegearpage.net/board/index.php?threads/does-this-sound-like-an-ac30-to-you.2325505/post-34009664]
# "An AC-30 has no negative feedback which is why it sounds the way it does." [https://forum.fractalaudio.com/threads/help-me-dial-in-the-ac30.192021/post-2387421]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-class-a-30w-vox-ac-30.112787/ Yek's write-up]

==CLASS-A 30W BRIGHT==

==CLASS-A 30W HOT==

==CLASS-A 30W TB==

==COMET 60 (Komet 60)==

[[file:komet60.jpg‎‎|300px]]

Model:
* Single channel

Volume, Treble, Middle, Bass, Presence, Hi Cut, Touch Response switch: Fast/Gradual (not modeled)

Power tubes: EL34

# "The Komet is definitely a unique amp. Sort of like a Fender preamp into a Marshall power amp. Unique tone stack." [https://forum.fractalaudio.com/threads/new-amps-in-10-06.70362/#post-863547]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-comet-60-komet-60.112823/ Yek's write-up]

==COMET CONCOURSE (Komet Concorde)==

[[file:kometconcorde.jpg‎‎|300px]]

Model:
* Single channel

Volume, Treble, Middle, Bass, Presence, Hi Cut, Touch Response switch: Fast/Gradual (not modeled)

Power tubes: EL34

# "The Komet is definitely a unique amp. Sort of like a Fender preamp into a Marshall power amp. Unique tone stack." [https://forum.fractalaudio.com/threads/new-amps-in-10-06.70362/#post-863547]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-comet-concourse-komet-concorde.112872/ Yek's write-up]

==CORNFED M50 (Cornford MK50 II)==

[[file:cornford.png|300px]]

Formerly: CORNCOB

Model:
* Overdrive channel

[[Cabinet models list |Cab:]] Cornford 4x12 (V30)

Gain, Overdrive, Bass, Middle (500Hz), Treble, Master, Presence, Resonance

Power tubes: EL34

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-corncob-m50-cornford-mk50-ii.112922/ Yek's write-up]

==DAS METALL (Diezel VH4 schematics)==

[[File:vh4.jpg|300px]]

Notes: see Dizzy V4

Power tubes: 6L6

==DELUXE TWEED (1957 Fender narrow-panel Tweed Deluxe, 5E3)==

[[file:deluxe.jpg|300px]]

Models:
* Bright input
* Bright and Normal inputs jumpered

[[Cabinet models list |Cab:]] Fender 1x12 (P12R, C12N, Alnico)

Volume Normal, Volume Bright, Tone

Power tubes: 6V6

# "Deluxe Tweed” amp model based on a Fender 5E3 Deluxe. Note that this amp only has a single tone control. This is modeled by the Treble control in the Axe-Fx II. The Bass and Mid controls are functional and recreate the amp when set to noon. Also note that this amp suffers from extreme blocking distortion at or near maximum gain. This is common in very old designs. As it is virtually unplayable like this, the model uses a somewhat reduced level of grid conduction to lower the amount of blocking distortion and make the amp more playable at high Drive settings."
# "The G3 version of the 5E3 Deluxe Tweed model is a hoot. Totally unpredictable, nasty, gnarly and raunchy. I couldn't stop playing it yesterday. Just like the real amp you have to be careful with your volume control and how you approach the amp so that you keep it right on the edge of playability. So cool." [https://forum.fractalaudio.com/posts/1144722]
# "The Deluxe Tweed amp model is a 5E3. The 1x12 Deluxe Tweed Mix cab is the IR." [http://forum.fractalaudio.com/threads/59-deluxe.106336/page-2#post-1272464]
# "Yup, that's the key. Crank the treble almost all the way up." [http://forum.fractalaudio.com/threads/59-deluxe.106336/page-3#post-1273603]
# "The actual amp has no grid stopper resistor on the second stage and therefore has LOTS of blocking distortion." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-00-beta-3.148907/page-3#post-1764588]
# "IMO the designs are poor because... wait for it... they exhibit a papery buzz. The problem with most cathode biased Class A amps is, 1: they aren't really Class A (more like hot Class AB) and 2: They go into Class B operation when they are overdriven. The cathode capacitor charges up and the bias point shifts dramatically. This causes lots of crossover distortion (papery buzz). It's worse on lower notes because lower notes have more energy and charge the cap more. The is probably the reason Leo Fender switched to fixed bias amps with negative feedback. Fixed bias is just that, the bias point is fixed so the amp doesn't shift into Class B operation when overdriven (not as much anyways, depends on the bias circuit, grid stoppers, etc.). Negative feedback linearizes the amp and reduces the crossover distortion (at the expense of gain). That's why the buzzing went away when you increased negative feedback. Crossover distortion is a unique sound. For cleaner sounds it tends to be objectionable. For overdriven sounds some find it desirable. EVH ostensibly liked his amps biased cold to get some crossover distortion. There are even some amps that have circuits to intentionally generate crossover distortion. Some distortion pedals also do this. Lowering the Cathode Resistance reduces the crossover distortion as it keeps the amp in Class A operation longer but the tubes run hotter and don't last as long. This is not a problem with our virtual amps though. I forget the actual values but I'm pretty certain if you look at the Cathode Resistance value for those amps it's pretty high. This means the amps are biased somewhat cold to begin with and shift to very cold as soon as overdriven." [https://forum.fractalaudio.com/threads/papery-buzz-under-some-models.149193/page-2#post-1772639]
# (about fuzzy lows) "That's what those amps do. Always been that way. Just to be sure I just compared the Deluxe Verb model with the reference amp and it's correct. Those are old designs. Simple circuits with minimal frequency shaping. As such there's a lot of bass going into the power amp. That coupled with the resonance magnification of the speaker impedance causes frequencies around the resonance (in the 50-100 Hz region) to distort early. The low E string is 82 Hz so it's right in that zone." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1842156]
# "When you dime the controls and whack a big chord the sound "goes away" a bit just like the real amp and then comes back a bit later." [https://forum.fractalaudio.com/threads/you-guys-gals-are-in-for-another-treat.169535/post-2042185]
# ("Cygnus" amp modeling) "The 5E3 model is now "jumped" so it has both Normal and Bright drives. You can get all sorts of different distortion textures by playing with the two drives in conjunction with the tone control. As with the real amp everything now interacts. One of the beta testers was remarking that his 5E3 clone sounded more "choked" in comparison to the model. I said "I bet your clone has the wrong type of tube in V1. It's supposed to be a 12AY7 but many clones have a 12AX7A in V1." He checked and, sure enough, 12AX7A in V1." [https://forum.fractalaudio.com/threads/cygnus-beta-first-impressions.169942/post-2045461]
# ("Cygnus" amp modeling) "I've added a non-jumped version of the 5E3 with both volume knobs. Now we can wait for the inevitable "When I turn the Bright Drive all the way down the Normal Drive doesn't do anything" comments." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2051108]
# "Amp doesn't have a bright cap." [https://forum.fractalaudio.com/threads/deluxe-tweed-bright-switch.173082/post-2094005]
# "Some of the undesirable characteristics are what makes a particular amp unique. For example a Deluxe 5E3 is characterized by significant blocking distortion. Without that it doesn't sound like a Deluxe and you can't do the Neil Young thing." [https://www.thegearpage.net/board/index.php?threads/is-digital-getting-too-real.2275913/post-32977457]
# " If you plug into a real Deluxe the "unused" control effects the sound." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-17-00.177099/post-2159734]
# "I finished the 57 Tweed Deluxe today and it's glorious. Clean to "Cinammon Girl" with the volume knob. I never appreciated that amp until I spent some serious time with it." [https://forum.fractalaudio.com/threads/you-guys-gals-are-in-for-another-treat.169535/post-2042068]
# ("Cygnus" amp modeling) "The Bassman and Deluxe Tweed models are both modeled using a 12AY7 as the input buffer. The Preamp Tube Type parameter only affects the tubes after the input buffer." [https://forum.fractalaudio.com/threads/12ay7-preamp-tube-for-tweed-deluxe-and-bassman-models.175834/post-2135435]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-deluxe-tweed-fender-deluxe-5e3.113007/ Yek's write-up]

==DELUXE TWEED JUMPED==

==DELUXE VERB NORMAL (1965 Blackface Fender Deluxe Reverb, AB763)==

[[file:deluxereverb.jpg|300px]]

Models:
* Normal channel
* Vibrato channel

[[Cabinet models list |Cab:]] Fender 1x12 or 2x10 with a Jensen ceramic C12Q, or EVM 12L, or JBL D120, or a Fender 2x10 with a ceramic C10N or C10Q or a 25W Alnico P10R

Volume, Bass, Treble, Reverb, Vibrato (not modeled)

Power tubes: 6V6

# "A DR is numbered 1-10 so 3 on a DR is around 2.2 on the Axe-Fx. The model is based on the Vibrato input #1 which has more gain than the normal input. To simulate plugging into the #2 jack (which has half the gain) set Input Trim to 0.5." [https://forum.fractalaudio.com/posts/1260148]
# "We got our reference Deluxe Reverb out of storage today, hooked it up and measured and compared. Gain measures spot-on and A/B testing sounds identical. With a Suhr Modern guitar with stock pickups both the amp and the model were starting to break up around 3 (which equals 2.2 on the Axe-Fx since the knobs start at zero not one). A Deluxe Reverb breaks up easily since it has 6V6 power tubes. The preamp is virtually identical to a Twin Reverb but 6V6s break up earlier than 6L6s. For a given voltage into the power amp a 6V6 has about 70% of the headroom compared to a 6L6." [https://forum.fractalaudio.com/posts/1262483]
# "The values for the Deluxe Reverb model are based on measurements of an actual 65 Deluxe Reverb, not some hypothetical values on some spec sheet." [http://forum.fractalaudio.com/threads/speaker-page-does-any-of-this-make-sense.110373/#post-1322466]
# (fuzzy lows) "That's what those amps do. Always been that way. Just to be sure I just compared the Deluxe Verb model with the reference amp and it's correct. Those are old designs. Simple circuits with minimal frequency shaping. As such there's a lot of bass going into the power amp. That coupled with the resonance magnification of the speaker impedance causes frequencies around the resonance (in the 50-100 Hz region) to distort early. The low E string is 82 Hz so it's right in that zone." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1842156]
# "We have two Deluxe Reverbs, a vintage 1965 Deluxe Reverb that the model is based on and a Reissue. The vintage one sounds great, the reissue doesn't quite sound as good. It's biased too cold. The comparison was between the model and the Reissue because the vintage amp is worth a small fortune and I only use that when actually working on models. It stays in climate controlled storage otherwise." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1842188]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-deluxe-verb-65-fender-deluxe-reverb-ab763.113046/ Yek's write-up]

==DELUXE VERB VIBRATO==

==DIAMANTE FIRE (22W Diamond Del Fuego)==

[[File:Diamante.jpg|300px]]

22W Class-A amplifier with two channels, designed by Roy Blankenship, based on a '60s Class-A 18W Marshall.

Model:
* channel xx with or without tremolo

Fractal Audio:
# "Nasty little thing." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-20-01-public-beta-2-beta-5.184958/post-2280269]
# "Yeah, it's a cool little amp. It's got some different component values than the Leeds which gives a different vibe." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-20-01-public-beta-2-beta-5.184958/post-2280439]

[[Cabinet models list |Cab:]] single GH12H, V30

Tremolo controls, Volume, Tone

Power tubes: EL84

[https://kitarablogi.com/2011/12/10/review-diamond-del-fuego-english-summary/ Review and sound clips]

[https://www.youtube.com/watch?v=Sn_evdKRhgQ Amp factory tour]

[http://www.diamondamplification.com Diamond Amplification]

==DIRTY SHIRLEY (40W Friedman Dirty Shirley)==

[[File:dirtyshirley.jpg|300px]]

Models:
* Current version of the amp
* Earlier version of the amp with different component values, a little more aggressive than the regular model

[[Cabinet models list |Cab:]] Friedman 4x12 (V30, G12M, G12-65, G12H)

Gain, Master, Bass, Middle, Treble, Presence

Power tubes: 5881

# "If you want more clarity in the low mids (...) reduce Negative Feedback. Friedman's designs are a bit odd in that he takes the feedback off the speaker jack rather than off a transformer tap. (...) The amp will sound tighter and clearer in the low mids." [http://forum.fractalaudio.com/threads/underrated-amp-models.109894/page-2#post-1316362]
# "The design is weird as the negative feedback is taken off the speaker jack. So if you use a 16-ohm speaker you get more feedback (and much more bass) than if you use an 8-ohm speaker. (...) It's too much bass for me so I turn down the Depth and reduce Negative Feedback a bit." [http://forum.fractalaudio.com/threads/question-about-the-friedman-amp-presets.110511/#post-1322655]
# "At first I didn't like it but for some genres it works. The old version (new model) has a 2.2 nF cap on the cathode follower while the newer version has 4.7 nF. The larger cap smooths out the distortion. The cathode bypass cap values are different as well which changes the midrange response." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-00-public-beta-2.124097/page-18#post-1477587 ]
# "Some amps have a fixed depth circuit, e.g. 5153, Freidman BE/HBE, Dirty Shirley, TripTik, Tucana, et. al. In these cases the Depth knob will default to a value that corresponds to the fixed circuit." [https://forum.fractalaudio.com/threads/lets-talk-about-the-depth-control.88747/#post-1071598]
# "I always lower the negative feedback. Friedman amps are a bit strange because the negative feedback is taken off the speaker jack instead of one of the transformer taps. The matching cabs are 16 ohms but if you use an 8-ohm cab you'll get 30% less feedback." [http://forum.fractalaudio.com/threads/couple-of-observations-about-the-friedmans-in-7-02.126030/page-2#post-1504343]
# ("Cygnus" amp modeling) "Dirty Shirley 1 is actually the latest version of the amp." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2048948]
# "They are very dark amp when used with the matching 16-ohm cabinet. The feedback is off the speaker jack (don't ask me why, doesn't make sense). This results in a lot of negative feedback at high frequencies which makes the sound dark. The amp is modeled assuming a 16-ohm load. If you use them into an 8-ohm cabinet they're brighter. To simulate this lower the negative feedback by 1/sqrt(2). This results in a negative feedback value of 3." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2052720]
# "Dirty Shirley 2 is the brighter of the two (has a 2.2nF cathode cap instead of 4.7nF)." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2052814]
# "They are dark amps." [https://forum.fractalaudio.com/threads/cygnus-dirty-shirley-dark.173450/post-2100020]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-dirty-shirley-friedman-dirty-shirley.113088/ Yek's write-up]

==DIRTY SHIRLEY 2==

[[File:dirtyshirley.jpg|300px]]

==DIV/13 CJ (Divided By 13 CJ 11)==

[[File:cj11.jpg‎|300px]]

Models:
* Mid Gain Boost OFF
* Mid Gain Boost ON

[[Cabinet models list |Cab:]] Divided by 13 (G12M)

Volume (pull: midgain boost), Treble, Bass, Master

Power tubes: 6V6

# "It is a bassy amp. Works best with single coils." [http://forum.fractalaudio.com/threads/13-goodness-st-michael-blues.56060/#post-706664]
# "You increase the LOW CUT FREQ to reduce the fuzziness on bass notes but then it won't sound like the real thing." [https://forum.fractalaudio.com/posts/724268]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-div-13-cj11-divided-by-13-cj-11.113126/ Yek's write-up]

==DIV/13 CJ BOOST==

==DIV/13 FT37 HIGH (Divided By 13 FTR 37)==

[[File:ftr37.jpg‎|300px]]

Models:
* Low: channel 1, Mid Gain Boost OFF
* High: channel 1, Mid Gain Boost ON

[[Cabinet models list |Cab:]] Divided by 13 (G12H and Alnico)

Volume (pull: Boost), Treble, Bass

Power tubes: 6V6

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-div-13-ft37-divided-by-13-ftr-37.113127/ Yek's write-up]

==DIV/13 FT37 LOW==

==DIZZY V4 BLUE 2 (Diezel VH4)==

[[File:vh4blue.jpg|300px]]

Models:
* Blue faceplate, channel 2 Crunch
* Blue faceplate, channel 3 Mega
* Blue faceplate, channel 4 Lead
* Silver faceplate, channel 2 Crunch
* Silver faceplate, channel 3 Mega
* Silver faceplate, channel 4 Lead

[[Cabinet models list |Cab:]] Diezel 4x12 (V30, G12-100)

Power tubes: KT77

Gain, Volume, Bass, Mid, Treble, Presence (4kHz), Deep (80Hz), Bright switch (not on channels 3 and 4)

# "The reason Diezels compress so much is due to the cathode follower design. You can reduce the compression in the models by lowering the Compression parameter in the Cathode Follower section." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-14-00.165157/post-1981183]
# "The bright switch on channel 2 in the Silver version is not a conventional bright switch. It switches in a treble peaker later in the circuit. The model models the amp with the bright switch on." [https://forum.fractalaudio.com/threads/cygnus-dizzy-amps-bug.173361/post-2102309]
# "Humans perceive high frequency thermal noise as hiss. The more gain the more hiss. Diezel's have a lot of filtering. Large grid stoppers, plate capacitors, etc. This reduces the bandwidth which lowers the hiss. Camerons are pretty much wide open. Small grid stoppers or bypass caps on the grid stoppers, no plate caps, etc." [https://forum.fractalaudio.com/threads/why-lower-gain-cameron-ccv-amp-model-feels-more-noisy-than-much-higher-gain-herbie-3.188658/post-2339783]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-das-metall-and-dizzy-v4-diezel-vh4.112971/ Yek's write-up]

==DIZZY V4 BLUE 3==

==DIZZY V4 BLUE 4==

==DIZZY V4 SILVER 2==

[[File:vh4.jpg|300px]]

==DIZZY V4 SILVER 3==

==DIZZY V4 SILVER 4==

==DOUBLE VERB NORMAL (1966 blackface Fender Twin Reverb)==

[[file:twin.jpg|300px]]

Models:
* Normal: based on 1966 blackface Fender Twin Reverb, tuned by Andy Fuchs, AB763 circuit, Normal channel
* Vibrato: based on the Vibrato channel of the same amp
* Silverface: based on the Vibrato channel of a 1971 100 watts “Silverface”

[[Cabinet models list |Cab:]] Fender 2x12 with original speakers, DynaCab available

Volume, Bass, Middle, Treble, Bright switch, Reverb (not modeled), Vibrato (not modeled)

Power tubes: 6L6

# (make the Twin cleaner) "Reduce MV (or MV Trim). The biggest reason Silverface Twins were cleaner is because the PI had less gain. Reducing the MV or MV Trim will simulate the lower gain." [https://forum.fractalaudio.com/posts/910015]
# (original Double Verb model) "The Twin Reverb that the model is based on breaks up like that. The model is MIMIC'd and is extremely accurate. It's a Blackface Twin which breaks up easy compared to later Twins. Furthermore, as with all models, it is modeled on the "Hi" input. If you don't want it to break up as easy turn Input Trim to 0.5 to simulate using the "Low" input, reduce Input Drive and MV as necessary. You may want to turn the Bright Switch off as well. People who want squeaky clean usually turn the Bright Switch off on these amps. However, you'd be surprised that a Twin isn't nearly as clean as you think. It's just so damn loud that you get the sensation that it's clean because a light touch on the strings creates a lot of volume." [https://forum.fractalaudio.com/posts/968763]
# "The model is extremely accurate and is based on a 1966 Blackface Twin Reverb. Part of the reason the Blackface era are so sought after is because they distort. They are NOT clean amps by any stretch." [http://forum.fractalaudio.com/threads/twin-issue.119594/#post-1422765]
# "A Dual Showman with the AB763 circuit has one less gain stage than a Twin Reverb so it will have less gain. There are two gain stages. The Vibrato channel of an AB763 Twin Reverb has three gain stages. An AA769 Dual Showman Reverb on the Vibrato channel will have similar gain as it has three gain stages. The circuit number, i.e. AB763, does not mean that the circuits are identical. It refers to the circa of the design. An AB763 Dual Showman is not the same circuit as an AB763 Twin Reverb." [http://forum.fractalaudio.com/threads/twin-issue.119594/page-2#post-1423069]
# "The Super Reverb is really just a 50W version of a Twin Reverb with different speakers." [https://forum.fractalaudio.com/threads/wanted-amps-to-model.56753/page-4#post-713267]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-double-verb-fender-twin-reverb.113177 Yek's write-up]

==DOUBLE VERB SILVERFACE (1971 silverface Fender Twin Reverb)==

==DOUBLE VERB VIBRATO (1966 blackface Fender Twin Reverb)==

==DWEEZIL'S BASSGUY (Dweezil Zappa's 1965 blackface Fender Bassman, AB165)==

[[file:ab165.png|300px]]

Model:
* 1965 Bassman Bass channel modded by Blankenship

[[Cabinet models list |Cab:]] Fender 2x12 (Oxford)

Volume, Negative Feedback, fixed Presence circuit (Presence should be at 10)

Notes: see 65 Bassguy

Power tubes: 6L6

# "It's Dweezil's Blankenship modified Bassman. Dweezil's Bassman has two channels like a regular Bassman. The Normal channel is "normal" and corresponds to the 65 Bassguy Nrml model. The Bass Instrument channel is modified and that's the basis for the new model (Dweezil's B-man). It has a boatload of gain and sounds more like a Plexi than a Fender." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-3-00-public-beta.113410/page-5#post-1356686]
# "Just finished matching this modded 65 Bassman that Dweezil sent me. It's a crazy sounding amp, sounds nothing like your typical Fender. It was modded by Roy Blankenship." [https://forum.fractalaudio.com/threads/another-v10-preview.62489]
# "The 65 Bassguy was matched to a 65 Bassman that Dweezil sent me. It's a vicious amp that sounds more like a Plexi than a Fender. It's the infamous AB165 circuit which is very crunchy and bright and does not sound like your typical Fender." [https://forum.fractalaudio.com/threads/am-i-the-only-one-who-noticed-that-some-amps-have-alot-more-gain.51123/page-2#post-658833]
# "The actual amp has no tone stack so for maximum authenticity all tone controls would be at noon (but don't be afraid to tweak them). In the actual amp the Treble control is re-purposed as a Negative Feedback control. Experiment with different values of Negative Feedback. Lower values are looser." [http://forum.fractalaudio.com/threads/help-with-trying-out-a-new-amp-block-dweezils-b-man.114154/#post-1365573]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-65-bassguy-65-blackface-fender-bassman-ab165.111298/ Yek's write-up]

==ENERGYBALL (Engl Powerball)==

[[File:powerball.jpg|300px]]

Model:
* Lead channel

[[Cabinet models list |Cab:]] Engl 4x12 (V30, V60)

Lead channel: Gain, Lo/Hi Lead switch, Bass, Mid-Open, Mid-Focused, Treble, Open / Focused switch (boosts 300-500 Hz) mode

Power tubes: 6L6

# (Cygnus) "The model was completely redone." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-12-cygnus-firmware-public-release-candidate.172027/post-2079284]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-energyball-engl-powerball.113247/ Yek's write-up]

==EURO BLUE (Bogner Ecstasy 20th Anniversary)==

[[File:ecstasy.png|300px]]

Models:
* Blue channel, structure switch: Vintage
* Blue channel, structure switch: Modern
* Red channel, structure switch: Vintage
* Red channel, structure switch: Modern

[[Cabinet models list |Cab:]] Bogner 2x12 or 4x12 (V30)

Gain, Master, Bass, Middle, Treble, Presence, Bright switch, Structure switch (gain reduction), Old/New Style switch (not modeled), Excursion switch, Gain switch, Plexi Mode (not modeled)

Power tubes: EL34 (earlier models were based on the 6L6 version)

# "People think Bogners are dark but they really aren't. The reason they seem that way is the pot tapers. Most people assume knobs should be set somewhere around noon. If you do this on a Bogner it's like turning the treble way down on a Marshall. Close your eyes and adjust the tone controls with your ears. Don't be afraid to turn them way up or way down." [https://forum.fractalaudio.com/posts/1031334]
# "Human nature is to put the knobs near noon. We are reticent to deviate much from noon. Amp designers exploit this and use different tapers to change the sound of their amps WITH THE KNOBS AT NOON. A prime example are Bogner amps. Everyone says "Bogner amps are dark". No they aren't. But he uses a Log10A taper for the treble pot. It's a standard Marshall tone stack. Usually a linear taper pot is used for the treble. The treble knob at 5.0 (noon) on a Bogner is equivalent to the treble knob at 1.0 on a Marshall. People put the knob at 5.0 and go "wow, this amp is dark". No it isn't. If you turned the treble up to 8 or 9 it would sound a lot like a Plexi but humans are reticent to turn the knobs to extremes. Amp designers know this and exploit it to give their amps a "signature sound"." [https://forum.fractalaudio.com/posts/1047275]
# "Our reference amp is a 20th anniversary and N is Bright Off, B1 is 150 pF and B2 is 1000 pF for both channels. The models default to B1. Change the Bright Cap value to 1 nF to emulate B2. Or better yet use your ears to select a value that sounds best." [http://forum.fractalaudio.com/threads/bogner-ecstasy-pre-amp-eq-b1-n-b2.109077/#post-1305047]
# (Class A) "Turn up Power Tube Grid Bias. In real life that is tough on tubes as it makes them run very hot." [https://forum.fractalaudio.com/threads/replicating-the-bogner-ecstasy-class-a-mode.145294/#post-1718463]
# "Bogner's are notoriously "slow" due to the low B+ voltage. Main reason I can't get along with them. You can try increasing the Variac." [https://forum.fractalaudio.com/threads/fast-pick-attack-amp.170370/post-2049711]
# "Most amps use a linear taper for the treble pot. Bogners use a log taper. So when the knob is at noon on a Bogner it's similar to 8 o'clock on most amps." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486/post-2067364]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-euro-bogner-ecstasy.113278/ Yek's write-up]

==EURO BLUE MODERN==

==EURO RED==

==EURO RED MODERN==

==EURO UBER (Bogner Uberschall)==

[[file:uber.png|300px]]

Model:
* High gain channel

[[Cabinet models list | Cab:]] Bogner 4x12 Uberkab (G12-T75 and V30)

Gain, Master, Bass, Middle, Treble, Presence, Depth (only on Twin-Jet Uberschall)

Power tubes: EL34

# "People think Bogners are dark but they really aren't. The reason they seem that way is the pot tapers. Most people assume knobs should be set somewhere around noon. If you do this on a Bogner it's like turning the treble way down on a Marshall. Close your eyes and adjust the tone controls with your ears. Don't be afraid to turn them way up or way down." [https://forum.fractalaudio.com/posts/1031334]
# "Human nature is to put the knobs near noon. We are reticent to deviate much from noon. Amp designers exploit this and use different tapers to change the sound of their amps WITH THE KNOBS AT NOON. A prime example are Bogner amps. Everyone says "Bogner amps are dark". No they aren't. But he uses a Log10A taper for the treble pot. It's a standard Marshall tone stack. Usually a linear taper pot is used for the treble. The treble knob at 5.0 (noon) on a Bogner is equivalent to the treble knob at 1.0 on a Marshall. People put the knob at 5.0 and go "wow, this amp is dark". No it isn't. If you turned the treble up to 8 or 9 it would sound a lot like a Plexi but humans are reticent to turn the knobs to extremes. Amp designers know this and exploit it to give their amps a "signature sound"." [https://forum.fractalaudio.com/posts/1047275]
# "The feedback circuit is responsible for the behavior of the Presence and Depth controls. Certain Bogners and Diezels have a unique type of feedback circuit. There are no new parameters and nothing to do except twist the Presence and Depth knobs to your desired tone. Note that an Uberschall doesn't have a Depth knob. The default Depth value when you select the Euro Uber model is equivalent to the amp's fixed depth circuit." [https://forum.fractalaudio.com/posts/1159760]
# "Bogner's are notoriously "slow" due to the low B+ voltage. Main reason I can't get along with them. You can try increasing the Variac." [https://forum.fractalaudio.com/threads/fast-pick-attack-amp.170370/post-2049711]
# "Most amps use a linear taper for the treble pot. Bogners use a log taper. So when the knob is at noon on a Bogner it's similar to 8 o'clock on most amps." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486/post-2067364]
# "My Uber is a very early one and probably different than later models. It has the feedback of the 4-ohm tap whereas I've heard later versions have the feedback off the 8-ohm tap. To simulate this increase the Negative Feedback." [https://forum.fractalaudio.com/threads/bogner-uberschall-help.185084/post-2282705]
# "That model does the chugga-chugga better than Thomas the Tank Engine." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-00-release-candidate-beta-7.188382/post-2336626]

[https://forum.fractalaudio.com/threads/fractal-audio-amp-models-euro-uber-bogner-uberschall.113311/ Yek's write-up]

==FAS 6160 (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "Based on the PVH 6160 model but more open and less fizzy than the original amp. Also, a virtual choke has replaced the resistor found on the original’s power supply filter. This results in a bouncier feel."
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS BASS (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6550

# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS BROOTALZ (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6550

# "This amp was an accident. I was working on the Savage model and accidentally used the input stage from an SLO100. So it's the front end of an SLO100 with the back end of a Savage. It's probably an SLO100 power amp too but I'd have to check." [https://forum.fractalaudio.com/posts/1020502]
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]
# "Brootalz uses the Engl Savage presence network which reduces negative feedback as the control is turned down causing an increase in volume." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-5-cygnus-firmware-public-beta-2.170901/post-2059273]

[https://forum.fractalaudio.com/posts/1020502/ Yek's write-up]

==FAS BROWN (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: EL34

# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-brown-and-fas-brown.111974/ Yek's write-up]

==FAS BUTTERY (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model. In the original Cygnus release, it was replaced by an authentic Budda Twinmaster model. It returned in firmware 17 for the Axe-Fx III and later, and firmware for the FM3 and FM9.

Power tubes: EL84

# "I did the Buttery model by ear. I listened to some clips of Buddas (Matchbox 20... excellent!) and tweaked the model until I thought it sounded like one. Screwed around a little with the tube bias points until it had the right balance of harmonics and called it a day."
# "It's still the "ear tuned" version. I bought the amp but because it was so popular as-is I didn't dare change it." [https://forum.fractalaudio.com/threads/question-for-cliff-regarding-the-buttery-model.90943/#post-1095174]
# "Buttery is a virtual amp model that was created by ear. There is no physical, real amp that exists upon which it was based. It's like the FAS models. They exist solely in the virtual world. They all still benefit from the Quantum stuff though as they use the same underlying algorithms for the tube modeling. The amp model, regardless of how accurate it is (and it's probably grossly inaccurate as I never compared it to any actual amp) is very popular and that's why it was never matched to any real amp." [http://forum.fractalaudio.com/threads/question-for-cliff-regarding-the-buttery-model.90943/page-2#post-1283301]
# "Yeah, Buttery was a legacy model from the first Axe-Fx." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-12-cygnus-firmware-public-release-candidate.172027/post-2075782]
# "The previous model wasn't based on any real amp. It was a "FAS Original". [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-12-cygnus-firmware-public-release-candidate.172027/post-2076487]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-buttery-budda-twinmaster.112228/ Yek's write-up]

==FAS CLASS-A (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: EL84

# "A “Blackface” preamp into a cathode-biased 6L6 power amp with no negative feedback. This was a happy accident when originally modeling the Carr Rambler in the beta version of this release. Several mistakes were made in the model prior to MIMIC’ing the amp but the model was so well liked that we decided to make it into its own custom amp model."
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[https://forum.fractalaudio.com/posts/1355719/ Yek's write-up]

==FAS CRUNCH (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: EL34

# "Our take on the ultimate British-sounding amp. More dynamic and open than a Plexi, but with more gain."
# "My take on the ultimate Plexi." [https://forum.fractalaudio.com/threads/axe-fx-ii-firmware-9-public-beta.59414/page-22#post-744829]
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS EXPRESS (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Notes: see Wrecker Express

Power tubes: EL34

# "Based on hypothetical modifications to a Trainwreck Express."
# "It has a master volume. That's one of the "mods"." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-11-02-public-beta-5-beta_4.157025/post-1875792]
# (about the Trainwreck Express) "That amp exhibits a lot of blocking distortion (in the phase inverter) due to its design. You can reduce this via either the PI Bias Excursion or Master Bias Excursion parameters. Another option is to use the FAS Express model which puts some resistors between the last triode stage and the PI to reduce the bias excursion." [https://forum.fractalaudio.com/threads/blocking-distortion-found-in-trainwreck-express.182895/post-2247268]

==FAS HOT ROD (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: EL34

# "FAS Hot Rod is my version of what a modded Marshall should be. I find the BE/HBE a little too boomy and scooped. Bogners are too dark. Splawns don't have enough compression. Etc. So it's my take on a hot-rodded Marshall tone." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-1-02-firmware-release.106477/page-4#post-1274103]
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS LEAD 1 (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS LEAD 2 (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: EL34

# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS MODERN (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "This model is my interpretation of the ideal modern metal tone. In the digital realm we are not constrained by the limitations that face tube amp designers so we are free to implement designs that would be nearly impossible with a tube amp. The Axe-Fx II modeling includes a variety of general purpose filters that I can place anywhere in the signal path. So I put some second-order filters in there to tighten up the tone. Implementing second-order filters in a real tube amp is difficult and costly so is rarely seen." [https://forum.fractalaudio.com/posts/715029]
# "It's loosely based on a Recto but with tighter bass." [https://forum.fractalaudio.com/threads/fw-6-0-rectifier-obsevation.51197/#post-658849]
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]
# (about the MESA Rectifier) "Personally I hate the 39K resistor. It biases the stage much too cold for my tastes. It prevents blocking distortion but there are better ways to do it IMO. The FAS Modern model is similar but biases the stage more towards the center." [https://forum.fractalaudio.com/threads/new-amp-models.159097/post-1901438]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS MODERN II (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "This is a tighter version of the popular FAS Modern model with a 5150-style bass boost in the tone stack."
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS MODERN III (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS RHYTHM (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "Combines the best features of the British (Marshall) and USA (Mesa) crunch models."
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FAS SKULL CRUSHER (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "The nastiest, most brutal amp model to ever escape from the seventh circle."
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]

==FAS WRECK (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Notes: see Wrecker Express

Power tubes: EL34

# "Based on the original WRECKER 1 model from the Axe-Fx Ultra."
# "The FAS models are idealized and have some of the "design flaws" removed or reduced." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841528]
# "If I had my way there would be only FAS models but too many people demand reproductions of existing amps." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944014]
# "The FAS models typically remove or minimize the undesirable characteristics of those old amps. Guitar tube amp design was nascent in the 60s and 70s and designers didn't fully understand the impact of overdriving tubes. One of the biggest issues was blocking distortion which is excessive bias excursion. When the grid conducts it shifts the bias point and in those old amps it can shift so much that the tube goes into cutoff prematurely. More modern designs employ grid stoppers and smaller coupling capacitors to reduce bias excursion." [https://forum.fractalaudio.com/threads/fas-class-a-is-even-better-than-the-real-thing.162257/post-1944071]
# "FAS Wreck model is better than any Trainwreck or Wreck-style amp IMO. All the good bits without the bad stuff." [https://forum.fractalaudio.com/threads/brad-paisley-z-wreck-with-blue-and-gold-2x12-cabinet.163617/post-1961880]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fas-models.113360/ Yek's write-up]

==FOX ODS (Fuchs Overdrive Supreme 50)==

[[file:fuchs.jpg|300px]]

Models:
* ODS: Deep switch OFF, Pre Amp Bypass ON (no tone controls)
* ODS Deep: Deep switch ON, Pre Amp Bypass ON (no tone controls)

[[Cabinet models list | Cab:]] Fuchs 2x12 (Eminence)

Gain, High (pull: mid boost), Mid (pull: gain boost), Low, Input, Brite switch, Deep switch, Rock/Jazz switch (not modeled), Master, Accent (= Presence)

Power tubes: 6L6

# "Supposedly a Dumble ODS clone but our reference amp has way more gain than our Dumble." [https://forum.fractalaudio.com/posts/1174814]
# "The topology of the Fuchs is pure Dumble. The difference is that there is less padding between stages 2 and 3 (IIRC). So it's a high-gain Dumble. Personally I don't think the Dumble topology lends itself to that much gain but I didn't design the amp. If you like the base Dumble sound but want a little more gain without the fuzziness of a Fuchs try the Carol-Ann models." [https://forum.fractalaudio.com/threads/fuchs-ods-in-cygnus.172291/post-2081523]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fox-ods-fuchs-overdrive-supreme.113514/ Yek's write-up]

==FOX ODS DEEP==

==FRIEDMAN BE 2010 (Friedman BE)==

[[File:BE.jpg|300px]]

Old models (before "Cygnus" amp modeling):

* BE: based on old Marsha model, BE mode
* BE C45: based on Mark Day's BE-100, C45 switch engaged
* BE V1: based on Mark Day's BE-100, voice: right position (less mids)
* BE V2: based on Mark Day's BE-100, voice: left position (more mids)
* HBE: based on old Marsha model, HBE mode
* HBE 2018: based on 2018 BE-100, HBE mode
* HBE 2018 C45: based on 2018 BE-100, HBE mode, C45 switch engaged
* HBE V1: based on Mark Day's BE-100, HBE mode, voice: right position (less mids)
* HBE V2: based on Mark Day's BE-100, HBE mode, voice: left position (more mids)

Current models ("Cygnus" amp modeling):

* BE 2010: based on Friedman BE-100 from 2010 (probably the "Marsha" edition)
* BE C45: based on later BE-100, C45 switch engaged
* BE V1: based on later BE-100, voice in left position
* BE V1 Fat: based on later BE-100, voice in left position, FAT switch engaged
* BE V2: based on later BE-100, voice in middle position (brightest)
* BE V3: based on later BE-100, voice in right position
* HBE 2010: based on Friedman BE-100 from 2010 (probably the "Marsha" edition), HBE mode
* HBE C45: based on later BE-100, C45 switch engaged
* HBE V1: based on later BE-100, voice in left position
* HBE V1 Fat: based on later BE-100, voice in left position, FAT switch engaged
* HBE V2: based on later BE-100, voice in middle position (brightest)
* HBE V3: based on later BE-100, voice in right position

[[Cabinet models list | Cab:]] Friedman 4x12 (V30 and/or G12M)

Gain, Master, Bass, Middle, Treble, Presence, Bright (clean channel only). BE-100 Deluxe: Thump control. Switches: FAT, C45 (treble boost), SAT (model: SAT), 3-position Voice switch (changes the top-end response of the dirty channels)

Power tubes: EL34

# (before Cygnus) "The old model is an original, hand-built "Marsha". It's MUCH darker than Mark's newer BE/HBE. In fact it's so dark and boomy I emailed Dave to make sure the amp was built correctly. Turns out the snubber cap is the wrong value. But even with the snubber cap corrected it's still very dark and boomy which made me question as to whether there are other components that are incorrect. So we decided to redo the model based on Mark's amp which is the amp that was the demo model at Tone Merchants." [http://forum.fractalaudio.com/threads/the-new-hbe.112717/#post-1348497]
# (before Cygnus) "The models are based on two different amps. The V1 and V2 are based on Mark Day's BE100. The other models are based on our original "Marsha". Like most boutique amp makers Friedman's designs have evolved over time with changes to the circuit. The original Marsha we have is dark and bassy with lots of lowpass filtering. The newer amp is brighter and tighter. For now note that V1/V2 refer to the newer amp and represent the position of the Voicing switch." [http://forum.fractalaudio.com/threads/which-are-the-new-be-hbe-models.114510/#post-1369754]
# "The BE/HBE has a fixed depth circuit that gives a lot of bass boost. The model defaults the Depth to match this." [https://forum.fractalaudio.com/posts/833169]
# "If you want more clarity in the low mids from the BE/HBE reduce Negative Feedback. Friedman's designs are a bit odd in that he takes the feedback off the speaker jack rather than off a transformer tap. The mating cab for a BE/HBE is 16 ohms which means lots of feedback. But if you connect the amp to an 8 ohm load there is about 30% less feedback. The amp will sound tighter and clearer in the low mids." [http://forum.fractalaudio.com/threads/underrated-amp-models.109894/page-2#post-1316362]
# "The design is weird as the negative feedback is taken off the speaker jack. So if you use a 16-ohm speaker you get more feedback (and much more bass) than if you use an 8-ohm speaker. The model is based on using the matching cab. It's too much bass for me so I turn down the Depth and reduce Negative Feedback a bit." [http://forum.fractalaudio.com/threads/question-about-the-friedman-amp-presets.110511/#post-1322655]
# "I always lower the negative feedback. Friedman amps are a bit strange because the negative feedback is taken off the speaker jack instead of one of the transformer taps. The matching cabs are 16 ohms but if you use an 8-ohm cab you'll get 30% less feedback." [http://forum.fractalaudio.com/threads/couple-of-observations-about-the-friedmans-in-7-02.126030/page-2#post-1504343]
# "C45 is a treble boost on the input. Put a filter block before the amp as follows: Type: Tilt EQ - Freq: 700 Hz - Gain: 4.5 dB" [http://forum.fractalaudio.com/threads/friedman-hbe-with-c45-switch.110686/#post-1324975]
# [http://forum.fractalaudio.com/threads/friedman-be-100-hbe-channel-vs-the-axe-fx-3-hbe-model.144911 Discussion about the Bass control]
# "Some amps have a fixed depth circuit, e.g. 5153, Freidman BE/HBE, Dirty Shirley, TripTik, Tucana, et. al. In these cases the Depth knob will default to a value that corresponds to the fixed circuit." [https://forum.fractalaudio.com/threads/lets-talk-about-the-depth-control.88747/#post-1071598]
# "When you watch a video Dave himself turns the bass way up. Steve Stevens and Jerry Cantrell turn the bass way up too. If I did that with my guitar it would be a muddy mess. Puzzling to me because the BE has a fixed depth circuit and a significant amount of negative feedback so there is quite a bit of bass boost in the power amp as well." [https://forum.fractalaudio.com/threads/friedman-be-100-hbe-channel-vs-the-axe-fx-3-hbe-model.144911/#post-1714308]
# "The BE has very light power supply filtering like old Plexis." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-14-01.165716/post-1990715]
# (Cygnus) "All the Friedman models are now based on the latest amp. Our reference amp was made in 2018 and has the feedback off the 4-ohm tap." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2047861]
# (Cygnus) "That's the way the HBE channel sounds. The problem with the design is that the drive control is located between the 3rd and 4th gain stages. Too far back IMO. This causes a lot of distortion and also a lot of bias excursion before the drive control with no way to control it. In most amps the drive control is located after the first stage (input buffer). Some amps have a second drive control, typically called an Overdrive, located further downstream which allows you to balance the pre- and post distortion. One way to deal with it is to decrease the Input Trim and increase the Input Drive. You can also try reducing the Master Bias Excursion but that won't get rid of the pre-drive control distortion. A lot of people like this sound though. It has a certain stringy quality that many people find desirable." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-10-cygnus-firmware-public-beta-7.171198/post-2062927]
# (Cygnus) "There are now three "Voicings": V1, V2 and V3 corresponding to the three positions of the Voice switch." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486]
# Based on latest version of amp. There are now three "Voicings": V1, V2 and V3 corresponding to the three positions of the Voice switch." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486/post-2067182]
# "The BE100 design has changed over the years. Dave is constantly fiddling with things. The original "Marsha" (which became the BE100 after the cease-and-desist) had the Gain control after the second stage. Later versions have the gain control after the third stage so even if you turn the gain down you may still get some distortion. There were also numerous changes to component values, feedback tap, etc., etc. Our models are authentic recreations of the two particular versions we have. Whether those versions match your particular version is unknown." [https://forum.fractalaudio.com/threads/friedman-amps-in-axefx3-vs-helix.197851/post-2458958]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-friedman-be-and-hbe-friedman-be-100.113559 Yek's write-up]

==FRIEDMAN BE C45==

==FRIEDMAN BE V1==

==FRIEDMAN BE V1 FAT==

==FRIEDMAN BE V2==

==FRIEDMAN BE V3==

==FRIEDMAN HBE 2010==

==FRIEDMAN HBE C45==

==FRIEDMAN HBE V1==

==FRIEDMAN HBE V1 FAT==

==FRIEDMAN HBE V2==

==FRIEDMAN HBE V3 ==

==FRIEDMAN SMALL BOX (Friedman Smallbox)==

[[File:smallbox.jpg|300px]]

Model:
* Channel 2

[[Cabinet models list |Cab:]] Friedman 2x12 (G12M)

Gain, Master, Bass, Middle, Treble, Presence, Bright switch (channel 1 only, not modeled)

Power tubes: EL34

# "The schematic shows a 2.2 nF coupling cap off the first stage but the actual amp has a 4.7 nF. 2.2 nF would mean less bass. I can only assume the amp was built to the latest specs. If an amp model is "G3'd" it is deadly accurate. I go through the amps and check the values of each component, measure the voltages, compare the frequency response to the model, etc., etc., etc. If the model is too bassy for you then you would find the real amp too bassy, or at least our particular reference model." [http://forum.fractalaudio.com/threads/friedman-sm-box-smallbox.99488/#post-1193341]
# "If you want more clarity in the low mids (...) reduce Negative Feedback. Friedman's designs are a bit odd in that he takes the feedback off the speaker jack rather than off a transformer tap. (...) The amp will sound tighter and clearer in the low mids." [http://forum.fractalaudio.com/threads/underrated-amp-models.109894/page-2#post-1316362]
# "The design is weird as the negative feedback is taken off the speaker jack. So if you use a 16-ohm speaker you get more feedback (and much more bass) than if you use an 8-ohm speaker. (...) It's too much bass for me so I turn down the Depth and reduce Negative Feedback a bit." [http://forum.fractalaudio.com/threads/question-about-the-friedman-amp-presets.110511/#post-1322655]
# "I always lower the negative feedback. Friedman amps are a bit strange because the negative feedback is taken off the speaker jack instead of one of the transformer taps. The matching cabs are 16 ohms but if you use an 8-ohm cab you'll get 30% less feedback." [http://forum.fractalaudio.com/threads/couple-of-observations-about-the-friedmans-in-7-02.126030/page-2#post-1504343]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-friedman-sm-box-friedman-small-box.113604/ Yek's write-up]

==FRYETTE D60 LESS (Fryette Deliverance 60)==

[[file:fryette.jpg|300px]]

Models:
* "Less" mode
* "More" mode

[[Cabinet models list | Cab:]] Fryette 4x12 P50E (Fane F70G)

Gain 1, Gain 2, Master, Bass, Middle, Treble, Presence, Depth, More/Less switch

Power tubes: KT88

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-fryette-d60-fryette-deliverance-60.113657/ Yek's write-up]

==FRYETTE D60 MORE==

==GIBTONE SCOUT (Gibson GA17RVT Scout)==

[[file:gibson.jpg‎|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Gibson 1x10

Volume, Tremolo, Reverb (not modeled)

Power tubes: 6AQ5

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-gibtone-scout.113698 Yek's write-up]

==HERBIE CH2+ (Diezel Herbert)==

[[File:herbert.jpg|300px]]

Models:
* Channel 2+ of original Herbert (based on Marshall JC800)
* Channel 2- of original Herbert (based on Marshall Plexi)
* Channel 3 of original Herbert (based on Diezel VH4)
* Channel 2+ of black-panel Herbert MK III

[[Cabinet models list |Cab:]] Diezel 4x12 (V30, G12-K100)

Gain (not on channel 1), Bass, Middle (1 kHz), Treble, Master, Presence (> 3kHz), Deep (120Hz), Mid-Cut (not modeled), Gain Boost switch (not modeled)

Power tubes: KT66

# "The reason Diezels compress so much is due to the cathode follower design. You can reduce the compression in the models by lowering the Compression parameter in the Cathode Follower section." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-14-00.165157/post-1981183]
# (reproducing the Mid Cut function) "Use a Peak EQ filter at 400 Hz with a Q of 1.4. Decrease its Gain until the desired scoop is achieved. Play with the Q to set the width of the scoop." [https://forum.fractalaudio.com/posts/1144887]
# "Humans perceive high frequency thermal noise as hiss. The more gain the more hiss. Diezel's have a lot of filtering. Large grid stoppers, plate capacitors, etc. This reduces the bandwidth which lowers the hiss. Camerons are pretty much wide open. Small grid stoppers or bypass caps on the grid stoppers, no plate caps, etc." [https://forum.fractalaudio.com/threads/why-lower-gain-cameron-ccv-amp-model-feels-more-noisy-than-much-higher-gain-herbie-3.188658/post-2339783]
# (the new Herbert model in firmware 21 for the Axe-Fx III) "I like it a lot more than the old version of the amp. The original Herbert is too dark, fuzzy, compressed and muddy IMO. Sounds great playing alone but when I play along with a recording it just gets lost. The new Herbert is tighter and sits in the mix better." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-00-release-candidate-2-beta-8.188778/post-2340412]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-herbie-diezel-herbert.113745 Yek's write-up]

==HERBIE CH2-==

==HERBIE CH3==

==HERBIE MK3 (Diezel Herbert MKIII)==

==HIPOWER BRILLIANT (Hiwatt DR103)==

[[file:hiwatt.jpg|300px]]

Models:
* Normal channel
* Brilliant channel
* Normal and Brilliant channels jumpered

[[Cabinet models list |Cab:]] Hiwatt 4x12 (Fane)

Volume, Master, Bass, Middle, Treble, Presence

Power tubes: EL34

# "I have a 1974 Hiwatt DR-103. The model is based on that. It is one of the Harry Joyce, Hylight era models. Still has the original tubes. Closet find and sounds glorious." [https://forum.fractalaudio.com/posts/497513]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-hipower-hiwatt-dr103.113789/ Yek's write-up]

==HIPOWER JUMPED==

==HIPOWER NORMAL==

==HOT KITTY (Bad Cat Hot Cat 30)==

[[file:hotcat.jpg|300px]]

Model:
* High gain channel

[[Cabinet models list | Cab:]] BadCat 1x12 (proprietary Celestion)

Gain, Edge (not modeled), Level, Bass, Mid-range switch (not modeled), Treble, Brilliance, Master

Power tubes: EL34

# "Brilliance is their name for Hi-Cut. I set the Edge control to where I thought it sounded best. It essentially does the same thing as the Bright knob though less precise."
# "The amp has a Hi Cut but it's labeled Brilliance. It's wired backwards so turning it CW gets brighter." [http://forum.fractalaudio.com/threads/hotkitty-1-05-is-nasty-as-hell.107651/page-2#post-1289111]
# "Those amps make a lot of IMD. The real amp does the same thing but you wouldn't normally use a subwoofer with one." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-00-public-beta-2.124097/page-14#post-1477200]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-hot-kitty-bad-cat-hot-cat-30.113829/ Yek's write-up]

==JMPRE-1 CLEAN 1 (Marshall JMP-1 preamp)==

[[image:Cliff JMP-1.jpg|300px]]

Models:
* Clean 1
* Clean 1 with Bass Shift engaged
* Clean 2
* Clean 2 with Bass Shift engaged
* OD1 mode
* OD1 mode with Bass Shift engaged
* OD2 mode
* OD2 with Bass Shift engaged

Volume, Gain, Bass, Mid, Treble, Presence (preamp), Bass shift, Depth

Power tubes: EL34

# "The power amp is based on a typical Marshall 100 watts power amp of the same era."
# [before firmware 19.02 for the Axe-Fx III] "The JMP-1 tone controls have more range than the actual preamp. The preamp has about +/- 8 dB for each tone control while the model has the standard +/- 12 dB."
# "Actually a JMP-1 is unique in that the tone controls do not interact. Most guitar amps use a passive "tone stack" where the controls interact. The JMP-1 has a fixed passive tone stack followed by an active 4-band EQ." [https://forum.fractalaudio.com/threads/is-the-brit-pre-good-enough.132950/#post-1573028]
# (Def Leppard) "The amp model you are looking for is "JMPre-1 OD1". Some cabs you might like to try with that amp model: Factory 2 #97 2x12 RECTO V60 57 OH, Factory 2 #995 4x12 UBER V30 57 OFF-AXIS, Factory 2 #530 4x12 BRIT 70s GB 121 I." [https://forum.fractalaudio.com/threads/are-phil-and-viv-using-brit-pre-or-jmpre-1-on-the-iii.139394]
# Firmware 19.02 and later for the Axe-Fx III:
#* Added JMPRE-1 Output EQ type to Amp block. This type replicates the active EQ used in the JMP-1 preamp.
#* Added Clean models.
#* The real amp has a fixed, passive tone stack with an active 4-band EQ. Therefore, the Bass/Mid/Treble controls when using Authentic Tone Controls are mapped to the Graphic EQ. Clean channels only: the passive tone stack itself, however, is adjustable. With all controls at noon the tone stack is equivalent to the real amp’s fixed tone stack. You can access these controls using the Ideal Tone Controls or via Axe-Edit.

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-brit-pre-and-brit-jmpre-1-marshall-jmp-1.112139/ Yek's write-up]

==JMPRE-1 CLEAN 1 BASS SHIFT==

==JMPRE-1 CLEAN 2==

==JMPRE-1 CLEAN 2 BASS SHIFT==

==JMPRE-1 OD1==

==JMPRE-1 OD1 BASS SHIFT==

==JMPRE-1 OD2==

==JMPRE-1 OD2 BASS SHIFT==

==JR BLUES (Fender Blues Junior)==

[[file:bluesjr.jpg|300px]]

Models:
* Fat switch OFF
* Fat switch ON

[[Cabinet models list | Cab:]] Fender 1x12 (Eminence, Jensen C12N, P12R)

Bass, Middle, Treble, Gain, Volume, FAT button (boosts gain and midrange frequencies), Reverb (not modeled)

Power tubes: EL84

# "The Blues Jr. amp has a fixed presence circuit." [https://forum.fractalaudio.com/threads/question-of-proper-axe-eq-values-for-amps-that-dont-have-them.67260/#post-828733]
# "They're actually pretty decent little amps and sound great when cranked." [https://forum.fractalaudio.com/threads/forgot-how-loud-tube-amps-are.170551/post-2052934]
# "The Master Volume in a Blues Jr. is linear taper. This is ridiculous as it makes it very difficult to find the sweet spot. The model uses an audio taper instead which makes finding the sweet spot easier." [https://forum.fractalaudio.com/threads/cygnus-is-absolutely-magnificent.173225/post-2096570]
# "Blues Jr. is a very colored preamp. The best you can do is turn Bass and Treble to zero and Mid all the way up. That will make it somewhat flat but you still have the bright cap on the drive and the bandpass between the preamp and power amp." [https://forum.fractalaudio.com/threads/negative-results-playing-my-fm9-through-a-blues-jr.189057/post-2343390]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-jr-blues-fender-blues-junior.113925/ Yek's write-up]

==JR BLUES FAT==

==JS410 CRUNCH ORANGE (Marshall JVM410HJS)==

[[file:js.jpg|300px]]

Models:
* Crunch Orange: based on a JCM 2203
* Crunch Red: based on a modded JCM 2203
* Lead Green: like the OD1 channel on the original JVM410H
* Lead Orange: more gain
* Lead Red: even more gain

[[Cabinet models list | Cab:]] Marshall 4x12 (V30 and G12H)

Volume, Gain, Bass, Middle, Treble, Master, Presence, Resonance, Gate (not modeled), Mid-Shift (around 650hz off and around 500hz on, not modeled)

Power tubes: EL34

# "Joe said he puts all the tone controls at around 10:00." [http://forum.fractalaudio.com/threads/jvm-js-in-the-tonestack.109946/#post-1316690]
# "The JVM has a huge plate resistor on the cathode follower, the JS does not." [https://forum.fractalaudio.com/threads/jvm-sounding-weird.150157/page-2#post-1785256]
# "The model is based on Joe's personal amp. He sent it to me. When I entered the values from the schematic it didn't match. The tapers of the controls were different and there were some other differences. I can only assume that his personal amp is different than production models. This is often the case as production models are designed to be inexpensive to build (i.e., using control tapers that are used in other models to reduce inventory, etc.). Another possibility is there were changes made during production. It is not uncommon for amps to have changes made to the circuitry over the production run. For example, the Blues Jr. has had numerous revisions. The first ones sound nothing like the later models. This is sometimes done due to perceived customer reaction ("The amp is too dark" or "The amp is too harsh"). Simply adjusting BMT should get you what you want. Control tapers make a big difference. For example, a Bass pot that is a linear taper would need to be set to 1.0 to match a Log10A taper at 5.0." [https://forum.fractalaudio.com/threads/marshall-jvm410hjs-real-amp-versus-axe3.197259/post-2450481]
# Firmware 23: "Updated all JS410 Lead models based on a current production JVM410HJS. The Crunch models were tested and did not require updating."
# (Was there much different between the production Satriani amp and his own one?) "Yes, they measure quite differently." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-23-00-public-beta-1.198479/post-2467475]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-js410-marshall-jvm410hjs.114030/ Yek's write-up]

==JS410 CRUNCH RED==

==JS410 LEAD GREEN==

==JS410 LEAD ORANGE==

==JS410 LEAD RED==

==JAZZ 120 (Roland Jazz Chorus 120)==

[[File:jc120.jpg|300px]]

Model:
* Single model

[[Cabinet models list| Cab:]] Roland 2x12 ("silver" AlNiCo)

Volume, Bass, Mid, Treble, Bright switch. Not modeled: Distortion, Chorus, Reverb

Power tubes: none (solid-state)

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-jazz-120-roland-jazz-chorus-120.113865/ Yek's write-up]

==LEGEND 100 (Carvin Legacy VL100)==

[[file:legacy.jpg|300px]]

Formerley: CALI LEGGY (VL100) and LEGATO 100 (VL300)

Legacy models:
* Legend 100: lead channel of Carvin VL100 Legacy
* Legend 100 II: channel 3 of Carvin VL300 Legacy 3

[[Cabinet models list | Cab:]] Carvin 2x12 or 4x12 (V30)

VL100: Presence, Treble (11kHz), Mid (650Hz), Bass (80Hz), Drive, Volume

VL300: Bass, Middle, Treble, Presence, Drive, Volume, Master, Boost (not modeled), Reverb (not modeled), Gain switch (not modeled)

Power tubes: EL34

# "The thing that makes a Legacy unique is the tone stack. It uses a "James" tone stack which is more like hi-fi tone controls." [https://forum.fractalaudio.com/threads/thank-you-fractal-for-the-leggy-legacy-model-its-great.47586/#post-620139]
# "Adds the "Legato 100" model based on Steve Vai's Legacy 100. This model is unique in that it uses a Baxandall (sometimes called a "James") tone stack. More often used on tube hi-fi gear the controls are less interactive than a typical guitar amp tone stack and impart a different tonal quality." [https://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-4-01-beta.119527/]
# "The Legato 100 is based on a one-of-a-kind version owned by a certain Californian guitar player. It is a very dark amp. Part of this is due to the tapers on the tone pots. With everything at noon the tone stack looks like a highshelf with a good amount of high frequency cut. The tone stack is a Baxandall which is more common in hi-fi gear than guitar amps. It lends a unique character to the tone." [https://forum.fractalaudio.com/posts/1426142]
# "SV's personal settings are: Drive: 7.5, Bass: 6, Mid: 4, Treble: 8, Presence: 8. I had to increase the Mid control on the model to about 5 to match the amp which indicates the mid pot on the amp was greater than spec. This is not unusual. Typical consumer-grade pots have pretty poor tolerance in both end-to-end resistance and resistance at the midpoint." [https://forum.fractalaudio.com/posts/1429558]
# (Cygnus) "Carvin Legacy 100. Legend II is channel 3 from the Legacy 3." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-12-cygnus-firmware-public-release-candidate.172027/post-2075753]
# "What is happening is the power amp is oscillating at that very low frequency cabinet resonance. This occurs because the Legacy has so much negative feedback (12 dB, which is the highest of any amp I've ever modeled). Combined with the smallish output transformer there is a loss of phase margin at low frequencies which causes the power amp to become unstable. The Rumble cab is unique in that it is ported and has two different types of speakers in it. This causes a double resonance and one of the resonances is at a very low frequency. For typical power amps with reasonable amounts of feedback this isn't an issue." [https://forum.fractalaudio.com/threads/bizzare-yet-interesting-legend-amp-model-possible-issue.173492/post-2101586]
# "The tonestack in a Legacy is a James. A Baxandall is active." [https://forum.fractalaudio.com/threads/have-we-reached-the-end-of-new-amp-models-in-the-axe-3.184271/post-2483056]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-cali-leggy-and-legato-100-carvin-legacy-vl100.112449 Yek's write-up]

==LEGEND 100 II (Carvin Legacy VL300)==

==MATCHBOX CHIEFTAIN 1 (Matchless Chieftain)==

[[File:chieftain.jpg|300px]]

Formerly: BOUTIQUE 1 and BOUTIQUE 2

Models:
* Single channel
* Boosted for more gain and high-frequency emphasis

[[Cabinet models list |Cab:]] Matchless 2x12 (G12H)

Volume, Master, Bass, Mid, Treble, Brilliance

Power tubes: EL34

# "The secret of the Chieftain is the split cathode bias. Most "Class-A" amps use a shared cathode bias but the Chieftain uses separate cathode bias networks which results in less bias shift so there's less fizz." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-03.158240/post-1895726]
# "The "Treble" knob on the Chietain model is actually Preamp Presence. It's not part of the tone stack. It's a separate presence network at the output of the last stage. They just call it treble." [https://forum.fractalaudio.com/threads/matchbox-chiefman-factory-preset-treble-knob-modifier-weirdness.173485/post-2100361]
# "The Treble control in a Chieftain is actually a "Preamp Presence" control, similar to the Presence control in a Dual Rectifier in Modern mode. It is separate from the tone stack and located later in the gain stages. The tone stack has no treble control." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-00.189017/post-2344358]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-boutique-matchless-chieftain.111832/ Yek's write-up]

==MATCHBOX CHIEFTAIN 2==

==MATCHBOX D-30 (Matchless DC-30)==

[[File:dc30.jpg|300px]]

Models:
* Channel 1 (12AX7 preamp tubes), Master Volume bypassed
* Channel 2 (EF86 preamp tubes), Master Volume bypassed

[[Cabinet models list | Cab:]] Matchless 2x12 (25w G12M and 30w G12H)

Channel 1: Volume, Bass, Treble, Cut, bypassable Master

Channel 2: Volume, Tone, Cut, bypassable Master

Power tubes: EL84

# "The DC-30 is basically an AC-30 copy. The voltages are a bit different but the topology is nearly identical. However, IMO, it does sound better. Not sure why. Perhaps the better quality components. AC-30's have kind of crappy OTs." [https://forum.fractalaudio.com/posts/968982]
# (channel 2) "The switch selects the coupling capacitor between the EF86 and the volume pot." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-9-00-beta.130981/page-11#post-1552400]
# "Added “Matchbox D-30 EF86” amp model. While the real amp has a six-position Tone switch, the model has a continuously variable tone control. Note that the Tone control is mapped to the Bass control in Ideal mode as the Tone switch is essentially a bass cut control."
# “The new DC-30 model may have dethroned the mighty AC-20 as my favorite "Class A" model.” [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-11-01.156108/post-1858859]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-matchbox-d-30-matchless-dc-30.114129/ Yek's write-up]

==MATCHBOX D-30 EF86==

==MR Z HWY 66 (Dr. Z Route 66)==

[[file:route66.jpg|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Dr. Z 2x12 (V30 and G12H)

Volume, Bass, Treble

Power tubes: KT66

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-mr-z-hwy-66-dr-z-route-66.114166/ Yek's write-up]

==MR Z MZ-38 (Dr. Z Maz 38 SR)==

[[File:maz38.jpg|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Dr. Z 1x12 (G12H)

Volume, Master, Bass, Mid, Treble, Cut, Reverb on some models (not modeled)

Power tubes: EL84

# "Dr. Z is the quintessential country amp." [https://forum.fractalaudio.com/posts/828934]"
# "IMO the designs are poor because... wait for it... they exhibit a papery buzz. The problem with most cathode biased Class A amps is, 1: they aren't really Class A (more like hot Class AB) and 2: They go into Class B operation when they are overdriven. The cathode capacitor charges up and the bias point shifts dramatically. This causes lots of crossover distortion (papery buzz). It's worse on lower notes because lower notes have more energy and charge the cap more. The is probably the reason Leo Fender switched to fixed bias amps with negative feedback. Fixed bias is just that, the bias point is fixed so the amp doesn't shift into Class B operation when overdriven (not as much anyways, depends on the bias circuit, grid stoppers, etc.). Negative feedback linearizes the amp and reduces the crossover distortion (at the expense of gain). That's why the buzzing went away when you increased negative feedback. Crossover distortion is a unique sound. For cleaner sounds it tends to be objectionable. For overdriven sounds some find it desirable. EVH ostensibly liked his amps biased cold to get some crossover distortion. There are even some amps that have circuits to intentionally generate crossover distortion. Some distortion pedals also do this. Lowering the Cathode Resistance reduces the crossover distortion as it keeps the amp in Class A operation longer but the tubes run hotter and don't last as long. This is not a problem with our virtual amps though. I forget the actual values but I'm pretty certain if you look at the Cathode Resistance value for those amps it's pretty high. This means the amps are biased somewhat cold to begin with and shift to very cold as soon as overdriven. Then there's shared vs. split cathode. If you look at the schematics on the web the Maz-38 is shared cathode. I could never get the model to sound exactly like our reference amp. Finally I traced the entire circuit and our particular amp is a split cathode. As soon as I changed the model to split cathode it was spot on. This is not exposed to the user though (there's a hidden shared/split switch). Our particular amp says "Humbucker" inside the chassis. Not sure if the difference in the cathode circuit is because Dr. Z likes split cathode for humbucking guitars or what." [https://forum.fractalaudio.com/threads/papery-buzz-under-some-models.149193/page-2#post-1772639]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-mr-z-mz-8-and-mz-38-dr-z-maz-8-and-maz-38-sr.114213/ Yek's write-up]

==MR Z MZ-8 (Dr. Z Maz 8)==

[[File:maz8.jpg|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Dr.Z 1x12 (G12H)

Volume, Master, Bass, Mid, Treble, Cut, Reverb (not modeled), Pentode/Triode switch (not modeled)

Power tubes: EL84

# "Dr. Z is the quintessential country amp." [https://forum.fractalaudio.com/posts/828934]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-mr-z-mz-8-and-mz-38-dr-z-maz-8-and-maz-38-sr.114213/ Yek's write-up]

==NUCLEAR-TONE (Swart Atomic Space Tone)==

[[file:swart.jpg|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Swart 1x12 (Mojotone BV-25m)

Volume, Tone, Tremolo, Reverb (not modeled)

Power tubes: 6V6

# "It's unique character comes from the PI. It's a cathodyne phase inverter so it doesn't drive the grids as hard." [https://forum.fractalaudio.com/posts/828241]
# "The real amp is known for it's tremolo so that's why we used the bias trem on the preset. Bias trem works by modulating the power tube grid bias. One of the side-effects is that the effect becomes less pronounced as you play harder which makes it basically "auto ducking". Also since it's modulating the bias it gives an almost Univibe like effect since the phase changes a bit too." [http://forum.fractalaudio.com/threads/patch-62-nuclear-tone-weird-tremolo-effect.122258/#post-1454602]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-nuclear-tone-swart-atomic-space-tone.113700/ Yek's write-up]

==ODS-100 CLEAN (Dumble Overdrive Special)==

[[File:dumble.jpg|300px]]

Models:
* Clean: based on HRM circuit, Clean channel
* Ford: based on schematics of Robben Ford's #102 Dumble, Overdrive channel, Pre Amp Boost (PAB) OFF
* Ford PAB: same as Ford model, PAB ON (bypasses the tone controls), Mid switch OFF
* Ford PAB Mid: same as Ford model, PAB ON, Mid switch ON
* HRM: based on HRM circuit, Overdrive channel, Mid switch OFF
* HRM Mid: based on HRM circuit, Overdrive channel, Mid switch ON

[[Cabinet models list | Cab:]] Dumble 2x12 or 4x12 (G12-65, EVM)

Volume (Clean), Bass, Middle, Treble, Overdrive Level, Ratio, Volume (Overdrive), Master, Presence, Bright switch, Mid boost switch, Jazz/Rock switch (not modeled), Pre Amp Boost (PAB)

Power tubes: EL34

# "The ODS100 has two drive controls, one is right at the input, the other is in the lead boost section."
# "I hate to admit it but there is something special about a real Dumble. I don't know what it is but there is something in the voicing. The various clones I have are cool and have their own thing going but they don't sound like the Dumble. Hard amp to play though. Very unforgiving but tremendous clarity." [https://forum.fractalaudio.com/posts/824398]
# "They call HRM "Hot Rubber Monkey" but what it really means is "Hot Rod Marshall"." The HRM Dumbles have a fixed Marshall tone stack at the output of the lead channel. This gives a little scoop to the mids." [https://forum.fractalaudio.com/posts/828279]
# "My Dumble is S/N 0213 IIRC. It's an EL-34 ODS HRM." [https://forum.fractalaudio.com/posts/1170559]
# "The ODS-100 Ford 2 model is not based on the HRM model with the HRM tonestack removed. Whether or not the model matches any particular Dumble is unknown as we have not been able to procure a non-HRM Dumble yet. The model is based on schematics that were given to us that supposedly accurately represent Robben Ford's Dumble. Whether or not the schematics are accurate I do not know. The voltage divider at the output of V1B is set to 0.078 which is based on the values that are indicated on the schematic for the set-point of the trimmer. As no two Dumbles are identical it stands to reason that one person's interpretation of the ideal Dumble voicing may not agree with another's. Since V1 is running clean you can get more gain by simply increasing Input Trim. It will have basically the same effect as increasing the trimmer."
# "A signal divider, which is more correctly called a voltage divider, is calculated by taking the resistance to ground divided by the sum of the resistances. In this case the voltage divider would be 26.7/317 = 0.084. This is very close to the values that we were given (which yield 0.078). Our model also uses local feedback on V1B (which is about 2-3 dB less gain) and accounts for the voltage divider's affect on the AC load line. In fact all stages in a Dumble typically have an AC load-line that's different than the DC load-line due to the load resistance being significant in relation to the plate resistor. Since V1A and V1B run clean (linear) Input Trim will accomplish the same thing as increasing the trimmer into the drive stages. This is because a linear system is commutative (see any introductory Signals and Systems text for properties of linear systems). The commutative property is where A x B = B x A. Therefore it does not matter if the gain is before or after the linear stages."
# "The Mid switch, sometimes labeled "Deep", shorts out the 390 pF cap in the tone stack (which is in series with a 2 nF cap). All that is left then is the 2 nF cap. With PAB active this lowers the lowcut frequency." [http://forum.fractalaudio.com/threads/dumbles-in-q2.110382/#post-1321445]
# "Maybe the best clean model IMO. You have to really crank the MV though (just like the real amp)." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-8-00-public-beta.126728/page-7#post-1507967]
# "The only amps with a bright cap on the MV are Dumbles and their various clones/derivatives. This was/is done to compensate for the lack of a buffer for the fx loop. The loop send is taken right off the MV which means the output impedance is very high. Any significant length of cable will then attenuate the highs due to the cable capacitance. The bright cap boosts the highs to compensate. It's the same idea as a bright cap on your guitar's volume knob. Crude. FWIW, this is a terrible loop design but "it's a Dumble" so it's all part of the mystique. Dumble then released the "Dumbleator" which is nothing more than a buffer and recovery in an external box. Dumble fanatics, of course, claim that to have the true Dumble experience you MUST use the Dumbleator which is just another load of BS." [https://forum.fractalaudio.com/threads/pick-attack.137945/#post-1720592]
# "We actually own a real Dumble. I bought it off a lawyer (surprise, surprise) some years ago who was in trouble with the IRS. Also a matching 4x12 cab. Both in mint condition. At the time I paid $50K for both. Probably worth twice that now." [https://www.thegearpage.net/board/index.php?threads/modelers-with-accurate-dumble-models.2120479/page-7#post-30771582]
# "PAB disconnects some components in the tone stack. The treble cap is still in the circuit path." [https://forum.fractalaudio.com/threads/ods-pab.180951/#post-2215259]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-ods-100-dumble-overdrive-special.114390/ Yek's write-up]

==ODS-100 FORD==

==ODS-100 FORD PAB==

==ODS-100 FORD PAB MID==

==ODS-100 HRM==

==ODS-100 HRM MID==

==PVH 6160 BLOCK (Peavey "Block Letter" EVH 5150)==

[[File:5150.jpg|300px]]

Models:
* Rhythm channel with Crunch switch engaged
* Lead channel

[[Cabinet models list | Cab:]] Peavey 4x12 (Sheffield 1200)

Pre Gain, Post Gain (Master), Low, Mid, High, Resonance, Presence, Bright and Crunch switches (Rhythm channel only, not modeled)

Power tubes: 6L6

# "I have a "holy grail" Block Letter 5150 (supposedly). It sounds way better than most 5150s for some reason which is a good thing for you guys. I think it's partly due to the fact that it has a bias mod so it's biased a bit warmer than a stock version." [https://forum.fractalaudio.com/posts/1152978]
# (differences between Peavey 5150 and 6505) "There are differences. The input gain network is different and the coupling cap after the second triode stage is a different value." [https://forum.fractalaudio.com/threads/peavey-invective-killer-amp.172625/post-2088479]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-pvh-6160-block-evh-5150-“block-letter”.114607/ Yek's write-up]

==PVH 6160 BLOCK CRUNCH==

==PVH 6160+ CLEAN (Peavey 6505+ / EVH 5150-II)==

[[file:6505.jpg|300px]]

Models:
* Clean channel, Bright switch OFF
* Clean channel, Bright switch ON
* Crunch channel, Bright switch OFF
* Crunch channel, Bright switch ON
* Lead channel

[[Cabinet models list | Cab:]] Peavey 4x12 (V30)

Rhythm channel: Pre (gain), Bright switch (6dB at 2kHz), Crunch switch, Low, Mid, High, Post (Master), Resonance, Presence

Lead channel: Pre (gain), Low, Mid, High, Post (Master), Resonance, Presence

Power tubes: 6L6

# "Chris Quigley's 6505 was the reference amp. It's my amp now. It's a very good sounding one." [https://forum.fractalaudio.com/posts/824411]
# (channel 1) "Someone was looking for that amp model recently so I dug our 6505+ out and was surprised at how nice that channel sounds." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-1-03-firmware-release.106931/#post-1278700]
# "A 6505+ is identical to a 5150 except it has no bright cap. Use the 5150 model and turn off the bright switch." [https://forum.fractalaudio.com/threads/request-acoustic-peavy-6505.56527/#post-711922]
# "The Bright switch on clean and crunch channels does not engage a capacitor on the drive potentiometer as is typical but instead disengages a treble cut circuit"

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-pvh-6106-peavey-6160-evh-5150-ii.114608/ Yek's write-up]

==PVH 6160+ CLEAN BRIGHT==

==PVH 6160+ CRUNCH==

==PVH 6160+ CRUNCH BRIGHT==

==PVH 6160+ LEAD==

==PLEXI 100W 1970 (1970 100W Marshall Plexi)==

[[file:SLP.png|300px]]

Plexi models:
* 1970 100 watts, EL34
* 1969 100 watts, High Treble channel
* 1969 100 watts, Normal and High Treble channels jumpered
* 1969 100 watts, Normal channel
* 1972 50 watts, 6550 power tubes
* 6AC7 50 watts, 6AC7 power tubes
* 1981 50 watts JMP with master volume, EL34
* 1967 50 watts, EL34, High Treble channel ("High 1")
* 1967 50 watts, EL34, High Treble channel ("High 2") (2nd triode stage has a 0.68uF cathode bypass capacitor, which was added in the early 70’s and gives a slightly brighter tone)
* 1967 50 watts, EL34, Normal and High Treble channels jumpered
* 1967 50 watts, EL34, Normal channel

[[Cabinet models list | Cab:]] Marshall 4x12 (G12M, G12H)

Volume Normal / Volume Treble, Bass, Middle, Treble, Presence, Master (Plexi 2204 only)

# "1970 Marshall 1959SLP 100 has a darker, smoother sound than earlier Plexis."
# "One of the first mods people make to real 'Plexi' Marshalls is to "clip the bright cap". The bright cap varied over the years, supposedly depending on what was lying around in the shop. The model defaults to the bright cap in the circuit. If you turn off Bright you're effectively clipping the bright cap. The bright cap in Marshalls can be very bright and harsh. However, if you crank the Master you might find the extra brightness helps compensate for the power amp getting darker."
# "It's the way a Plexi is supposed to sound. That's due to the cathode follower. That raspiness helps it cut through in a mix. I own three of them and they are that fizzy." [https://forum.fractalaudio.com/posts/576475]
# "Don't be afraid to turn the bass all the way down or the treble all the way up. Just like with the actual amp. For example, on the Normal channel of a Plexi most people turn the bass way down. Otherwise it's too flubby." [https://forum.fractalaudio.com/posts/577248]
# "My settings for a "typical" Plexi tone are Bass: 2, Mid: 8, Treble 7.5. Adjust Presence to taste." [https://forum.fractalaudio.com/posts/1179420]
# "Try the Plexi 100W 1970 with Factory Cab 54. Be sure to dial it in like you would in 1970, i.e. turn the Mid, Treble and Presence way up; turn Norm Drive and Bass down a bit." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-2-00-public-beta-deux.109702/#post-1312811]
# (Boston/Rockman sound) "Plexi Jump. Everything on 7. Put a Filter block in front: Type: Peaking, Freq: ~800 Hz, Q: 0.707, Gain 12 dB."
# (Plexi 100W 1970) "I've never cared for that model nor the actual amp. IMO it doesn't have enough feedback (100K off the 4-ohm tap). Some amps of that era had 47K off the 4-ohm tap. Some had 47K off the 8-ohm tap. Some had 100K off the 8-ohm tap and some even had 47K off the 16-ohm tap! IOW all over the map. Bottom line: try adjusting Negative Feedback. I always raise it up a bit with that model. Around 4 or so." [http://forum.fractalaudio.com/threads/plexi-100watt-1970-is-something-wrong-with-it-now.125522/#post-1493932]
# "What you are hearing is output transformer high frequency resonance. Old Plexis didn't do this because they had good transformers. New transformers are crappy and resonate at the cutoff frequency because they are underdamped. This causes a raspy, fizzy texture to the distortion. The transformer resonance is adjustable but the parameter isn't exposed to the user. When you turn it up you get that same squishy rasp that you are hearing. For the Plexis I have the damping set to flat with no resonance because that's how our vintage Plexis measure. Our 50W is a little underdamped but people complain about raspy high frequencies so I erred on the safe side." [http://forum.fractalaudio.com/threads/dimed-real-plexi-vs-dimed-simulation-q8-01.127161/page-2#post-1513888]
# "When modding Marshalls for higher gain sometimes the modder will decrease the input frequency response to reduce noise and fizziness. You can do this by reducing the high-cut frequency in the input EQ. Or you can use a high-shelf filter which is a little more subtle. Another technique is to put a capacitor across the second-to-last triode stage. This is the "Triode 1 Plate Freq" parameter. Reduce this to around 2 kHz to start which is typical of amps like an SLO100, etc." [https://forum.fractalaudio.com/threads/dialling-in-the-marshalls.143682/post-1707222]
# "The Plexi 100W 1970 model is a non-MV "Plexi". Circuit is slightly different than the late 60's model (Plexi 100W)." [https://forum.fractalaudio.com/threads/marshall-amp-question.155223/post-1847908]
# "All the distortion comes from the power amp so the tone controls don't do much." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-4-cygnus-firmware-public-beta.170253/post-2052743]
# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]
# [[Amp_block#NEGATIVE_FEEDBACK|Negative feedback values]]
# "(100W model) Our reference amp has a 560p treble cap and a 10A treble pot taper. Both components appear to be original. The tech who checked it out after I bought it said it was one of the best sounding 100W Plexis he'd ever heard. That tech just happens to be Alan Phillips of Carol-Ann Amps. So I modeled it to agree with the reference amp." [https://forum.fractalaudio.com/threads/modeling-questions.199009/post-2491136]
# (100W model) It's a '69. The 50W might be a '67. Hard to keep track of it all. I must have at least a dozen Marshalls now." [https://forum.fractalaudio.com/threads/modeling-questions.199009/post-2491192] and [https://forum.fractalaudio.com/threads/nothing-like-a-real-plexi.64593/post-801933]
# (100W model) "All the pots are log pots in our reference amp" and "I was puzzled by the pot tapers but they all look original. I then thought about it a bit and wondered if that's why Bogner uses log pots for his amps. His stuff is definitely Plexi-inspired. Or maybe all Marshall could find at the surplus electronics store that week was log pots. Who knows." [https://forum.fractalaudio.com/threads/modeling-questions.199009/post-2491180]
# (50W model) "Our reference 50W Plexi has a 68nF presence cap and the presence network is JCM800-style." [https://forum.fractalaudio.com/threads/modeling-questions.199009/post-2491179]

[http://forum.fractalaudio.com/threads/late-70s-marshall-jmp-master-model-50w-mk2-lead.135541 Forum discussion about the Plexi 2204 model]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-plexi-marshall-plexi.114529/ Yek's write-up]

==PLEXI 100W HIGH (1969 100W Marshall Plexi)==

# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]
# "The power supply sags more in a 100W. On our reference 100W Plexi the supply sag is almost double that of our 50W." [https://forum.fractalaudio.com/threads/marshall-jmp-100w.198803/post-2478167]
# "The topology of that model does not support a bright cap and the actual amp has no bright cap." [http://forum.fractalaudio.com/threads/q2-01-plexi-50w-nrml-bright-cap-doesnt-work.111836/#post-1337410]
# "All the pots are Logarithmic pots in our reference amp." [https://forum.fractalaudio.com/threads/modeling-questions.199009/post-2491161]

==PLEXI 100W JUMPED==

==PLEXI 100W NORMAL==

==PLEXI 2204 (1981 50W Marshall JMP 2204)==

# "Based on a 1981 JMP 50W Master Volume head."
# (recommended settings) "Everything on 10."
# "There were several versions of the "2204" Plexi. Our model is based on a 1981 2204 Master Volume JMP. It has a different circuit than a JCM800." [https://forum.fractalaudio.com/threads/marshall-sound-clips.169296/post-2034903]
# "The model is based on the Hi input of a 1981 50W Master Volume "2204" Plexi. There were two versions of the 2204. One was essentially a Plexi with a Master Volume. Similar to a 1987x but with some different values and voltages in addition to the MV. The other was virtually identical to a JCM800. The model is the Plexi version. Mine is an '81 and doesn't have cascaded gain stages." [https://forum.fractalaudio.com/threads/plexi-2204-question.178464/]
# "It's a 1981 "CSA" 2204."[https://forum.fractalaudio.com/threads/plexi-2204-question.178464/post-2175316]
# [https://forum.fractalaudio.com/proxy.php?image=https%3A%2F%2Fimages.reverb.com%2Fimage%2Fupload%2Fs--0dABDsRq--%2Fa_exif%2Cc_limit%2Ce_unsharp_mask%3A80%2Cf_auto%2Cfl_progressive%2Cg_south%2Ch_620%2Cq_90%2Cw_620%2Fv1518443139%2Fvgiq3h9wiuaj0jw2wxhb.jpg&hash=5b419d07341f4bdad48af0657dcd11de Picture of the modeled amp]

==PLEXI 50W 6550 (1972 50W Marshall Plexi)==

* High Treble Channel

==PLEXI 50W 6CA7 (50W Marshall Plexi)==

Models:
* Single channel
* Jumped channels

# "That's based on my favorite Plexi. I have several but this particular one has 6CA7s and 82K grid resistors(!). Usually the grid resistors are 220K." [https://forum.fractalaudio.com/threads/plexi-50w-6ca7-sooooo-good.169084/post-2031777]

==PLEXI 50W 6CA7 JUMPED==

==PLEXI 50W HIGH 1 (1967 50W Marshall Plexi)==

==PLEXI 50W HIGH 2==

# "Similar to Plexi 50W High 1 except the second triode stage has a 0.68uF cathode bypass capacitor. The second bypass capacitor was added in the early 70’s and gives a slightly brighter tone."
# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]

==PLEXI 50W JUMPED==

==PLEXI 50W NORMAL==

# "There's a 0.68uF cap on the second triode." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-20-05-public-beta-beta-1.187133/post-2317922]

==PORTA-BASS (Ampeg Portaflex bass amp)==

Model:
* Single channel

[[Cabinet models list | Cab:]] SVT cab with one or more 10”, 12” or 15” Eminence speakers

Gain, Volume, Bass, Mid, Treble, Mid Frequency (not modeled), input pad (not modeled), compression (not modeled), limiter (not modeled), Ultra Hi switch, Ultra Lo switch (not modeled)

It's not been disclosed on which Portaflex amplifier the model is based

Power tubes: 6L6

Notes: see SV Bass

==PRINCE TONE 5F2 (Fender Tweed Princeton, 5F2-A)==

[[file:princeton.jpg|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Fender 1x10 (C10n)

Volume, Tone

Power tubes: 6V6

[http://forum.fractalaudio.com/posts/1370144/ Yek's write-up]

==PRINCE TONE AA964 (silverface Fender Princeton without reverb, AA964)==

Model:
* Single channel

Volume, Bass, Treble

Power tubes: 6V6

# "Based on a Fender AA964 Princeton. This particular amp is an early CBS “Silverface” but still using pre-CBS design and components."

==PRINCE TONE REVERB (1966 blackface Fender Princeton with reverb, AA964)==

[[file:princetonreverb.jpg|300px]]

Model:
* Single channel

Volume, Bass, Treble, Reverb (not modeled)

Power tubes: 6V6

# "A Princeton Reverb has an extra gain stage due to the reverb recovery. Hence it has more gain." [https://forum.fractalaudio.com/threads/what-causes-this-volume-difference.97845/#post-1174202]

==RECTO1 ORANGE MODERN (MESA Dual Rectifier, 2 channels)==

[[file:recto.png|300px]]

Rectifier models:
* Recto1: original 2-channel Rectifier, Orange channel, Modern mode
* Recto1: original 2-channel Rectifier, Orange channel, Vintage mode
* Recto1: original 2-channel Rectifier, Red channel, Modern mode
* Recto2: later 3-channel Rectifier, Orange channel, Modern mode
* Recto2: later 3-channel Rectifier, Orange channel, Vintage mode
* Recto2: later 3-channel Rectifier, Red channel, Modern mode
* Recto2: later 3-channel Rectifier, Red channel, Vintage mode

[[Cabinet models list | Cab:]] Mesa 4x12 (V30)

Gain, Master, Bass, Middle, Treble, Presence

Power tubes: 6L6

# "The reason you're hearing the highs rolled off is because the Master is too high. As you increase the Master the highs get muffled. 7.02 for the Recto Master is ridiculous and will sound like crap." [https://forum.fractalaudio.com/threads/axe-fx-vs-tube-amps-my-first-experience.27192/page-3#post-412068]
# "Note that the Orange Modern and Red Modern models have no negative feedback and therefore the Presence control is a Hi Cut control." [https://forum.fractalaudio.com/threads/version-10-00-stuff.63202/#post-783037]
# "A typical Recto cabinet has a resonant frequency a little over 100 Hz." [https://forum.fractalaudio.com/threads/dual-recto-with-the-lb-2-vs-the-axe-fx-iii-and-more.143501/page-2#post-1699892]
# "The unique thing about a Dual Recto tone stack is that the Presence control is part of the tone stack. So the Recto tone controls also interact with the presence control." [https://forum.fractalaudio.com/threads/dual-recto-with-the-lb-2-vs-the-axe-fx-iii-and-more.143501/#post-1699011]
# "Rectos don't have a Depth control and even if they did it wouldn't do anything in Modern Red mode since that mode has no negative feedback. When you put a Recto into Modern Red mode it opens a relay which removes the NFB." [https://forum.fractalaudio.com/threads/recto-depth.92482/#post-1111780]
# "Real Rectos are bassy/fizzy beasts but that tone works great for certain genres." [https://forum.fractalaudio.com/posts/658849]
# "If you are using the Modern modes be very careful with the MV. If you turn it up too high it will flub out really quick. If in doubt reduce the MV. Compensate with the Level control." [https://forum.fractalaudio.com/posts/829334]
# "The Modern mode in Rectos has no negative feedback so there's a huge bass boost from the speaker impedance. Fortunately you can reduce this by reducing the LF Resonance on the Spkr tab which is something you can't do with the real amp without trying different speakers or cabinet." [https://forum.fractalaudio.com/posts/829906]
# "Depth works by varying the negative feedback at low frequencies. There is no NFB in the Modern Red mode so the Depth knob won't do anything." [https://forum.fractalaudio.com/posts/1111770]
# (Thordendal models) "The old Recto models weren't terribly accurate. When G3 came out the models were accurate but Fredrik contacted me and said something like "ahhhhh, I loved the old Recto model". So I took the old Recto models and made them "Thordendal" models." [http://forum.fractalaudio.com/threads/thordendal-modern-vs-recto-1-modern-red.91645/#post-1269530]
# "All passive tone controls interact and all the Axe-Fx tone stacks replicate this behavior. The unique thing about a Dual Recto tone stack is that the Presence control is part of the tone stack. So the Recto tone controls also interact with the presence control." [https://forum.fractalaudio.com/threads/dual-recto-eq-potentially-silly-question.93890/#post-1126242]
# "If you are using the Modern mode then it's all about the Spkr page. Since that mode has no negative feedback the speaker resonance has a tremendous effect on the sound. Adjust LF Res, Freq and Q to get desired response." [http://forum.fractalaudio.com/threads/anyone-have-any-luck-with-the-rectifier-models.109907/#post-1315682]
# "Another thing with the Modern modes is that the power amp distorts early (again since there is no negative feedback and, therefore, the power amp has a lot more gain). At 9:00 on the Master the power amp is distorting (it's probably a linear taper pot for the ol' "Wow, this amp is loud bro!"). (...) Another thing is that if you put ANYTHING in the loop of a Recto it changes the tone significantly. Even just a short cable. All the models were made with the loop off. And another thing is that Rectos changed a lot. I have three of them and they all sound completely different. One of them has a different value Gain pot than the others. One of them has a different value bright cap than the one with the same Gain pot. Since the gain pot and bright cap interact this makes a HUGE difference. Experiment with the Bright Cap value. The Recto1 models are based on our Rev. F (IIRC, whatever the desirable ones are). The Recto2 models are based on the latest version." [http://forum.fractalaudio.com/threads/anyone-have-any-luck-with-the-rectifier-models.109907/#post-1315714]
# "We have three of them, a single and two duals." [http://forum.fractalaudio.com/threads/when-were-the-rectos-improved.122719/#post-1459883]
# "If you want that Recto crunch but not so flubby and fizzy try the SOLO models." [http://forum.fractalaudio.com/threads/ax8-v7-00-public-beta.125015/page-3#post-1487394]
# "A Recto is not a Mark series amp. Totally different preamp topology. A Recto preamp is very similar to a SLO100." [https://forum.fractalaudio.com/threads/the-greatest-digital-guitar-recording-of-all-time.154788/post-1841448]
# (amp model closest to the MESA Roadster) "Recto 2." [https://forum.fractalaudio.com/threads/what-amp-model-is-closest-to-the-mesa-roadster.127060/post-1512755]
# "The Rectifier preamp is almost identical to an SLO100." ... "There's a treble cut on the tone stack and a some minor changes to the power amp and power supply but it's basically a ripoff. The schematics are readily available for both so anyone interested can see for themselves. Personally I hate the 39K resistor. It biases the stage much too cold for my tastes. It prevents blocking distortion but there are better ways to do it IMO. The FAS Modern model is similar but biases the stage more towards the center." [https://forum.fractalaudio.com/threads/new-amp-models.159097/post-1901310]
# "Using the loop on a modern 3-channel rectifier changes the tone pretty dramatically (we model the amp with the loop bypassed). There are several reasons for this:
## The source impedance to the power amp is changed.
## There is a treble peaker on the Output pot. Presumably this was done to counteract treble loss in the loop.
## An extra highpass filter is present due to the loop send stage. The corner frequency is around 30 Hz. That's low but it does affect subharmonics due to intermodulation. I would've made the capacitor around 1uF." [https://www.thegearpage.net/board/index.php?threads/blind-test-mesa-dual-rectifier-vs-mystery-modeler-update-results-revealed.2208367/post-31646126]
# "Recto2 is based on a new 3-channel Dual Rectifier. Recto1 is based on the original 2-channel." [https://www.thegearpage.net/board/index.php?threads/blind-test-mesa-dual-rectifier-vs-mystery-modeler-update-results-revealed.2208367/post-31647001]
# "I have three Rectos: an old Single Rectifier, an old (Rev. G maybe) Dual Rectifier and a new Dual Rectifier. They all sound completely different. The old Dual is the best sounding of the bunch." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-9-cygnus-firmware-public-beta-6.171176/post-2062420]
# "The MV taper of the model is authentic so just like the real amp the power amp starts to clip very early. With the real amp there's audible feedback (as in it gets insanely loud) but with the model you don't get that and humans have this weird thing where they don't like knobs to deviate from noon. I've debated changing the taper or adding a pad between the preamp and power amp but, in the end, I decided to keep things authentic." [https://forum.fractalaudio.com/threads/simple-tip-for-recto-tones.174349/post-2114224]
# "You have to be very careful with the Master Volume. A Recto will start saturating the power amp in Modern mode at VERY low MV settings. Once the power amp starts clipping the tone will change. With digital products I often see people set the MV higher than they would on the real amp because there are no sonic repercussions (i.e., pissing off the wife/neighbors, knocking Grandma's urn off the mantel, etc.). If an emulation sounds darker or more midrangey than the real amp try turning down the MV. If it's a good emulation you should find a point (around 1-2) where you can hear the power amp start to saturate. Go up/down from there to get the desired power amp overdrive." [https://www.thegearpage.net/board/index.php?threads/why-are-rectifier-emulations-so-off.2341907/post-34347979]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-recto1-and-recto2-mesa-dual-rectifier-2-ch-and-3-ch.114701/ Yek's write-up]

==RECTO1 ORANGE NORMAL==

==RECTO1 RED==

==RECTO2 ORANGE MODERN (MESA Dual Rectifier, 3 channels)==

==RECTO2 ORANGE VINTAGE==

==RECTO2 RED MODERN==

==RECTO2 RED VINTAGE==

==REVV GEN GREEN 1 (REVV GENERATOR 120)==

Models:
* Green channel, least aggression (green)
* Green channel, tight saturation (blue)
* Green channel, fat saturation (red)
* Purple Gain channel, least aggression (green)
* Purple Gain channel, tight saturation (blue)
* Purple Gain channel, fat saturation (red)
* Red Gain channel, least saturation (green)
* Red Gain channel, tight saturation (blue)
* Red Gain channel, fat aggression (red)

[[Cabinet models list | Cab:]] Revv 4x12 (V30)

Gain, Bass, Mid, Treble, Level, Master, Presence, Depth. Options on Clean and Crunch channels: Wide / Drive / Bright. Options on Purple and Red channels: Aggression / Bright / Cut / Fat.

Power tubes: 6L6

# "Revv is a great amp. Sort of a Marshall/SLO vibe but more open. Really well designed and built." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-22-00-release.195047/post-2429051]
# "The Revv actually has an MV that makes sense. Instead of driving the power amp into oblivion at around 3, power amp overdrive doesn't start happening until you turn the knob up quite a bit." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-22-00-release.195047/post-2429139]

==REVV GEN GREEN 2==

==REVV GEN GREEN 3==

==REVV GEN PURPLE 1==

==REVV GEN PURPLE 2==

==REVV GEN PURPLE 3==

==REVV GEN RED 1==

==REVV GEN RED 2==

==REVV GEN RED 3==

==RUBY ROCKET (Paul Ruby Rocket)==

[[File:rocket.jpg|300px]]

Models:
* Bright switch ON
* Bright switch OFF

[[Cabinet models list | Cab:]] 1x12 (Alnico, G12M)

Volume, Bass, Treble, Cut, Bright switch

Power tubes: EL84

# "The Ruby Rocket is not the same as an actual Trainwreck Rocket. There are topology differences and the amps don't sound the same." [https://forum.fractalaudio.com/posts/1154295]
# "Ruby Rocket is based on a Paul Ruby Rocket which is based on a TW Rocket but with some notable differences." [https://forum.fractalaudio.com/threads/axe-fx-ii-firmware-18-00-public-beta.96198/page-30#post-1154336]
# "The Bright switch changes a coupling cap and the treble cap in the tone stack. This cuts the bass, shifts the midrange and lowers the gain slightly. That's why there are two separate models. Otherwise you would just engage the Bright switch under the Treble knob."
# "The Ruby Rocket has a bright switch but it's actually a channel select (selects the bright channel)."

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-ruby-rocket-paul-ruby-rocket.114725/ Yek's write-up]

==RUBY ROCKET BRIGHT==

==SV BASS 1 (Ampeg SVT bass amp)==

[[File:ampeg.jpg|300px]]

SVT models:
* SV Bass 1: Fractal Audio's model prior to the change in firmware Ares 2.05 and later
* SV Bass 2: channel one of a 1970 Ampeg SVT with 6550 power tubes and the midrange switch in position 3

Note: on the Axe-Fx II (firmware Ares) these models are reversed [https://forum.fractalaudio.com/threads/sv-bass-1-and-sv-bass-2-in-ares-1-03.149364]

[[Cabinet models list | Cab:]] SVT 8x10

Volume, Treble, Midrange, Bass, Master, Midrange switch, Ultra-Hi switch (= Bright), Ultra-Lo switch (not modeled)

Power tubes: 6550

Uses a James tonestack [https://forum.fractalaudio.com/threads/have-we-reached-the-end-of-new-amp-models-in-the-axe-3.184271/post-2482710]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-sv-bass-ampeg-svt.115282/ Yek's write-up]

==SV BASS 2==

==SHIVER CLEAN (Bogner Shiva 20th Anniversary)==

[[File:shiva.png|300px]]

Models:
* Clean channel
* Lead channel

[[Cabinet models list | Cab:]] Bogner 1x12 or 2x12 (Classic 80, V30)

Clean channel: Volume, Bass, Treble, Bright switch. Shared: Master, Presence, Excursion, Boost switch (not modeled)

Lead channel: Gain, Volume, Bass, Middle, Treble, Shift EQ (not modeled), Bright switch, Mode switch (not modeled). Shared: Master, Presence, Excursion, Boost switch (not modeled)

Power tubes: KT88

# "People think Bogners are dark but they really aren't. The reason they seem that way is the pot tapers. Most people assume knobs should be set somewhere around noon. If you do this on a Bogner it's like turning the treble way down on a Marshall. Close your eyes and adjust the tone controls with your ears. Don't be afraid to turn them way up or way down." [https://forum.fractalaudio.com/posts/1031334]
# "Human nature is to put the knobs near noon. We are reticent to deviate much from noon. Amp designers exploit this and use different tapers to change the sound of their amps WITH THE KNOBS AT NOON. A prime example are Bogner amps. Everyone says "Bogner amps are dark". No they aren't. But he uses a Log10A taper for the treble pot. It's a standard Marshall tone stack. Usually a linear taper pot is used for the treble. The treble knob at 5.0 (noon) on a Bogner is equivalent to the treble knob at 1.0 on a Marshall. People put the knob at 5.0 and go "wow, this amp is dark". No it isn't. If you turned the treble up to 8 or 9 it would sound a lot like a Plexi but humans are reticent to turn the knobs to extremes. Amp designers know this and exploit it to give their amps a "signature sound"." [https://forum.fractalaudio.com/posts/1047275]
# "The original Shiva models were based on a borrowed amp. We now have a 20th Anniversary Shiva (with KT88s) and the new models are based on that amp. We did notice that this amp has less gain than the one used originally but the model is faithful to the amp." [https://forum.fractalaudio.com/posts/1152978]
# "Bogner's are notoriously "slow" due to the low B+ voltage. Main reason I can't get along with them. You can try increasing the Variac." [https://forum.fractalaudio.com/threads/fast-pick-attack-amp.170370/post-2049711]
# "Most amps use a linear taper for the treble pot. Bogners use a log taper. So when the knob is at noon on a Bogner it's similar to 8 o'clock on most amps." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486/post-2067364]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-shiver-bogner-shiva-20th-ann.114764/ Yek's write-up]

==SHIVER LEAD==

==SOLO 100 CLEAN (Soldano SLO-100)==

[[File:slo.jpg|300px]]

Models:
* Normal channel in Clean mode
* Normal channel in Rhythm mode
* Overdrive channel

[[Cabinet models list| Cab:]] Soldano 4x12 (Eminence)

Gain, Bass, Middle, Treble, Master, Presence, Bright switch (Normal channel only), Depth (with Depth mod)

Power tubes: 6L6

# "The SLO-100 is the loudest amp I've ever used. It feels like there's a small nuclear explosion going off inside when ever you hit a power chord. It's a wicked amp but not something I would recommend for anything but large gigs. If you like the SLO-100 model you might want to try the Recto models too. It's not widely known but the Rectifier preamp is a derivative of the SLO-100. Some minor changes but the basic topology is identical."
# "I have a really good SLO-100. An original black faceplate version. Pristine condition. That amp was one of the primary amps used in the G2 modeling development. It was by studying that and a really nice JCM-800 that I finally figured out the secret to cathode follower." [https://forum.fractalaudio.com/posts/562187]
# "Mine doesn't have the depth mod but I used the values from the schematic I have and I believe the schematic is correct." [https://forum.fractalaudio.com/posts/830925]
# "SLOs are brittle at low volumes. When you crank them up it smooths out. The problems is at cranked volumes they can kill small animals."
# "The key to an SLO100 is to run the MV high so that the mids thicken up. Otherwise it's a shrill mess. In certain contexts with the right IR it can be a cool sound." [https://forum.fractalaudio.com/posts/1146118]
# "Note that the knobs on '5' on the Axe-Fx correspond to '6' on an SLO because they go to 11. 'Noon' on an SLO isn't actually the knobs at half-way. The range of the knobs is like 8:00 to 6:00 as opposed to 7:00 to 5:00. They're biased clockwise." [https://forum.fractalaudio.com/posts/1057829]
# "Another caveat when comparing amps: many times the knobs aren't "centered". IOW if you put the Treble knob at noon it isn't actually at 50%. You can see this by turning the knob all the way down and all the way up. It may not be symmetrical. This happens when the pots don't have a flat spot and/or the pot is rotated within the mounting hole. Or in the case of an SLO100 it is intentional. On an SLO100 all the way down is around 8:00 and all the way up is 6:00 so 50% is around 1:00 not noon." [https://forum.fractalaudio.com/posts/1158815]
# "Many people find SLOs too bright. The "Warren Haynes" mod is a popular mod to reduce the brightness."
# "Those amps are all designed to get their character from power amp distortion. If you don't push the power amp all you are hearing is the preamp which is voiced to be trebly. The power amp then compresses the highs and the sound gets fatter."
# "If you want that Recto crunch but not so flubby and fizzy try the SOLO models. They're much brighter so I turn the treble down quite a bit." [http://forum.fractalaudio.com/threads/ax8-v7-00-public-beta.125015/page-3#post-1487394]
# "SLO 100s are NOT smooth amps. They are nasty, aggressive things that you have to crank the MV." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-00-beta-3.148907/page-4#post-1764615]
# "A Recto is not a Mark series amp. Totally different preamp topology. A Recto preamp is very similar to a SLO100." [https://forum.fractalaudio.com/threads/the-greatest-digital-guitar-recording-of-all-time.154788/post-1841448]
# "The Rectifier preamp is almost identical to an SLO100." [https://forum.fractalaudio.com/threads/new-amp-models.159097/post-1901310]
# "They're pretty awesome amps but to sound great you have to crank 'em and they're ear-splitting loud." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-09.162488/post-1947441]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-solo-100-soldano-slo-100.114877/ Yek's write-up]

==SOLO 100 LEAD==

==SOLO 100 RHYTHM==

==SOLO 88 CLEAN (Soldano X88R preamp)==

[[image:x88r.jpg|300px]]

Models:
* Clean channel
* Rhythm channel
* Lead channel

Gain, Bass, Middle, Treble, Volume, Bright switch (Clean and Rhythm channels only)

Power tubes: same as SLO-100 model (6L6)

# "Solo 88 RHY is based on an X88R since the rhythm channel of an X99 is identical to an SLO-100. FWIW, I have two X88Rs and the model agrees with both."

[https://forum.fractalaudio.com/posts/718846/ Yek's write-up]

==SOLO 88 LEAD==

==SOLO 88 RHYTHM==

==SOLO 99 CLEAN (Soldano/Caswell X99 preamp)==

[[File:Cliff X88.jpg|300px]]

Models:
* Clean channel
* Lead channel, Bright OFF
* Lead channel, Bright ON

Gain, Bass, Middle, Treble, Volume, Bright switch

Power tubes: same as SLO-100 model (6L6)

# "The rhythm channel of an X99 is identical to a SLO 100." [https://forum.fractalaudio.com/posts/718846]
# "Power amp: same as SLO100." [https://forum.fractalaudio.com/posts/1250203]
# "The bright cap on the X99 Clean is not across the Drive pot. The exposed "Bright Cap" is across the Drive pot, the X99 clean channel does not have one." [https://forum.fractalaudio.com/threads/found-a-bug-soldano-x99-clean-bright-cap.28046/post-418468]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-solo-88-and-solo-x99-soldano-x88r-and-x99.114878/ Yek's write-up]

==SOLO 99 LEAD==

==SOLO 99 LEAD BRIGHT==

==SPAWN NITROUS 1 (Splawn Nitro)==

[[file:nitro.gif|300px]]

Models:
* Overdrive channel in OD-1 (Rhythm) mode
* Overdrive channel in OD-2 (Lead) mode

[[Cabinet models list| Cab:]] Splawn 4x12 (G12M, G12-65, V30)

Resonance, Presence, Bass, Middle, Treble, Master, Gain

Power tubes: KT88

# "Based on a Splawn Nitro with KT-88 power tubes."

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-spawn-nitrous-splawn-nitro.114911/ Yek's write-up]

==SPAWN NITROUS 2==

==SPAWN Q-ROD OD1-1 (Splawn Quickrod)==

[[File:quickrod.jpg|300px]]

Models:
* Overdrive channel, Rhythm mode, 1st gear ("Plexi")
* Overdrive channel, Rhythm mode, 2nd gear ("hot-rodded JCM 800")
* Overdrive channel, Rhythm mode, 3rd gear ("super hot-rodded 800")
* Overdrive channel, Lead mode, 1st gear
* Overdrive channel, Lead mode, 2nd gear
* Overdrive channel, Lead mode, 3rd gear

[[Cabinet models list | Cab:]] Splawn (G12M, G12-65, V30)

Presence, Bass, Middle, Treble, Volume, Gain, Mode

Power tubes: EL34

# "The reason Splawns sound weird is because the tone stack is plate driven. You lose the cathode follower compression and the high source resistance of the plate alters the tone stack frequency response. The plate driven tone stack in the Splawn reduces the highs considerably. You can see this is you run Tone Stack Calculator for the Marshall tone stack and increase the source resistance." [https://forum.fractalaudio.com/posts/1070559]
# "OD2 switches in a cathode bypass cap which increases the gain of that stage." [https://forum.fractalaudio.com/posts/1158818]
# "The Quick Rod is a bit odd in that the Drive pot is linear taper. Most amps use an audio taper pot. This means that at noon the amp is nearly at full gain. Not sure why they did it that way but it is what it is." [https://forum.fractalaudio.com/posts/1159425]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-spawn-rod-splawn-quickrod.114968/ Yek's write-up]

==SPAWN Q-ROD OD1-2==

==SPAWN Q-ROD OD1-3==

==SPAWN Q-ROD OD2-1==

==SPAWN Q-ROD OD2-2==

==SPAWN Q-ROD OD2-3==

==SUHR BADGER 18 (Suhr Badger 18)==

[[File:badger18.jpg‎|300px]] [[File:badger30.jpg‎|300px]]

Badger models:
* Badger 18
* Badger 30

[[Cabinet models list | Cab:]] Suhr 1x12 or 2x12 (V30, G12M)

Bass, Middle, Treble, Gain, Power (controls Power Scaling, not modeled), Drive (acts as Master with Power at 10)

Power tubes: EL84 (Badger 18), EL34 (Badger 30)

# "The Badgers were MIMIC'd with power scaling at full. The knobs are a bit confusing on a Badger. The knob closest to the input jack is labeled "Gain". It is equivalent to the Drive knob in the Axe. The knob labeled Drive is the Master Volume." [https://forum.fractalaudio.com/posts/830810]
# "The controls on the Badger are a bit confusing. Master Volume is labeled Drive. You have the Drive at 10 which means your power amp is at full blast. This can make the bass muddy. Turn the Drive down." [https://www.thegearpage.net/board/index.php?threads/i-have-to-say-im-a-little-upset.2205478/post-31553496]
# "IMO the designs are poor because... wait for it... they exhibit a papery buzz. The problem with most cathode biased Class A amps is, 1: they aren't really Class A (more like hot Class AB) and 2: They go into Class B operation when they are overdriven. The cathode capacitor charges up and the bias point shifts dramatically. This causes lots of crossover distortion (papery buzz). It's worse on lower notes because lower notes have more energy and charge the cap more. The is probably the reason Leo Fender switched to fixed bias amps with negative feedback. Fixed bias is just that, the bias point is fixed so the amp doesn't shift into Class B operation when overdriven (not as much anyways, depends on the bias circuit, grid stoppers, etc.). Negative feedback linearizes the amp and reduces the crossover distortion (at the expense of gain). That's why the buzzing went away when you increased negative feedback. Crossover distortion is a unique sound. For cleaner sounds it tends to be objectionable. For overdriven sounds some find it desirable. EVH ostensibly liked his amps biased cold to get some crossover distortion. There are even some amps that have circuits to intentionally generate crossover distortion. Some distortion pedals also do this. Lowering the Cathode Resistance reduces the crossover distortion as it keeps the amp in Class A operation longer but the tubes run hotter and don't last as long. This is not a problem with our virtual amps though. I forget the actual values but I'm pretty certain if you look at the Cathode Resistance value for those amps it's pretty high. This means the amps are biased somewhat cold to begin with and shift to very cold as soon as overdriven. One reason I like the AC-20 is that it runs the tubes hotter and exhibits less crossover distortion. The worst amp in this regard is the Badger 18. The cathode resistors are very large and the amp shifts into Class B operation early causing a spitty, buzzy distortion quality. This amp, however, is liked by many so that just goes to show that some people like that. It's like fuzz pedals. Some people like that spitty sound. I personally don't like it. Then there's shared vs. split cathode. If you look at the schematics on the web the Maz-38 is shared cathode. I could never get the model to sound exactly like our reference amp. Finally I traced the entire circuit and our particular amp is a split cathode. As soon as I changed the model to split cathode it was spot on. This is not exposed to the user though (there's a hidden shared/split switch)." [https://forum.fractalaudio.com/threads/papery-buzz-under-some-models.149193/page-2#post-1772639]
# "The Badger doesn't have a Bright switch." [https://forum.fractalaudio.com/threads/fixed-next-rel-wild-rumbling-chirping-artifacts-switching-between-presets.154544/post-1837842]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-suhr-badger-18-and-30.115086 Yek's write-up]

==SUHR BADGER 30 (Suhr Badger 30)==

==SUPER VERB NORMAL (1964 Fender Super Reverb, AB763)==

[[file:superreverb.jpg‎|300px]]

Models:
* Normal channel
* Vibrato channel

[[Cabinet models list | Cab:]] Fender 4x10 (C10R, C10Q, P10R)

Volume, Bass, Middle (Vibrato channel only), Treble, Bright switch, Reverb (not modeled), Vibrato (not modeled)

Power tubes: 6L6

# "I modeled the Super with V1 pulled as most people pull V1 so the amp has more grunt. Turn down the MV to make it cleaner."
# "The Super Reverb model is based on the amp with V1 removed (which is a common mod). This increases the level into the power amp by about a factor of two." [https://forum.fractalaudio.com/threads/xl-units-quantum-6-fw-austin-buddy-raw-amp-bank-part-i-feedback.123065/#post-1464566]
# "The Super Reverb model is "Diaz Modded". IOW, I pulled V1. This gives the amp a lot more gain so it's not surprising you're getting breakup at around 1.5. You can un-mod the model by turning down the MV Trim to around 0.5." [https://forum.fractalaudio.com/posts/851580]
# "A Pro Reverb is basically identical to a Super Reverb except for the speakers (and faceplate)." [https://forum.fractalaudio.com/posts/933261] And: "The Blackface Pro Reverb, model AA165, was virtually identical to the AB763 Super Reverb except for the speakers and tone stacks. If you use the Super Verb model and set the Tone Stack type to Blackface you'll basically have a Pro Reverb. Set the Mid control fairly high to emulate the fixed 6.8K mid resistor. I'd say around 7 or 8." [https://forum.fractalaudio.com/posts/1079578]
# (blackface) "Not a huge change with the Silverfaced versions. They're a little cleaner and brighter but the topology is the same. Some minor circuit changes here and there. Same transformers. The biggest change, IMO, was changing the PI resistors to 47K which gives you a little less gain in the PI." [https://forum.fractalaudio.com/posts/1252495]
# "The Super Reverb is really just a 50W version of a Twin Reverb with different speakers." [https://forum.fractalaudio.com/threads/wanted-amps-to-model.56753/page-4#post-713267]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-super-verb-64-blackface-fender-super-reverb-ab763.115124 Yek's write-up]

==SUPER VERB VIBRATO==

==SUPERTWEED (custom model)==

[[File:Logo small.png]]

Custom Fractal Audio model

Power tubes: 6L6

# "Original." [https://forum.fractalaudio.com/threads/supertweed.172803/post-2088909]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-supertweed-custom-model.115143/ Yek's write-up]

==SUPREMO TREM (Supro 1964T)==

[[File:supro.png|300px]]

Model:
* single model

[[Cabinet models list | Cab:]] Supro 2x12

Volume, Tone

Power tubes: 6973

# "They're simple amps with minimal tone shaping." [https://forum.fractalaudio.com/threads/time-for-another-supro.154552/post-1838288]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-supremo-trem-supro-1964t.115232/ Yek's write-up]

==TEXAS STAR CLEAN (MESA Lone Star Classic)==

[[file:lonestar.png|300px]]

Models:
* Clean channel
* Lead channel

[[Cabinet models list | Cab:]] Mesa 2x12 (C90)

Drive, Gain, Treble, Mid, Bass, Presence, Master, Voicing (not modeled)

Power tubes: 6L6

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-tx-star-mesa-lone-star.115405/ Yek's write-up]

==TEXAS STAR LEAD==

==THORDENDAL MODERN (custom model of MESA Dual Rectifier)==

[[file:meshuggah.jpg|300px]]

Models:
* Modern mode
* Vintage mode

Power tubes: 6L6

Notes: see Recto

# "The old Recto models weren't terribly accurate. When G3 came out the models were accurate but Fredrik contacted me and said something like "ahhhhh, I loved the old Recto model". So I took the old Recto models and made them "Thordendal" models." [http://forum.fractalaudio.com/threads/thordendal-modern-vs-recto-1-modern-red.91645/#post-1269530]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-thordendal-pre-g3-recto-models.115326/ Yek's write-up]

==THORDENDAL VINTAGE==

==TREMOLO LUX (blackface Fender Tremolux, AA763)==

[[File:tremolux.jpg|300px]]

Models:
* Normal channel
* Vibrato channel

[[Cabinet models list | Cab:]] Fender 2x10

Vibrato channel: Volume, Bright switch, Treble, Bass, Tremolo controls

Power tubes: 6L6

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-tremolo-lux-fender-blackface-tremolux-aa763.115354/ Yek's write-up]

==TRIPLE CREST 2 (MESA Triple Crown TC-100)==

[[file:triplecrown.jpg|300px]]

Models:
* Low gain channel
* High gain channel

Gain, Treble, Mid, Bass, Normal / Tight switch, Presence, Reverb (not modeled), Master, attenuator (not modeled)

Power tubes: EL34

# “The actual amp’s “Tight” switch engages a built-in Tube Screamer circuit which can be replicated using a Drive block or the Amp block’s internal Boost feature.” [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-04.159140/post-1901363]
# "The clean channel is like every other Mesa clean channel: a Blackface Fender copy." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-05.159156/post-1901965]
# "The clean channel uses the same built-in tube screamer as the other channels. There's a single fixed tube screamer circuit at the input of the amp. It can be switched in via relays which are controlled by the channel switches." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-12-05.159156/post-1904010]
# "A Mesa Triple Crown has a built-in Tube Screamer set clean on the input." [https://www.thegearpage.net/board/index.php?threads/looks-like-fractal-devices-are-getting-a-new-modeling-update-cygnus.2224849/post-32213988]
# "The Triple Crest models are based off a Mesa Triple Crown which is "derived from" a Fender Tonemaster." [https://forum.fractalaudio.com/threads/triple-crown-info.174892/post-2121012]

==TRIPLE CREST 3==

==TUBE PRE (generic tube preamp model)==

[[file:Logo small.png]]

Custom Fractal Audio model of a generic tube preamp

Power tubes: 5881 (power amp disabled)

# "The Vintage tone stack is a passive EQ model but it has a flat response when the controls are at noon. If you want "active" EQ you need to set the type to Active." [https://forum.fractalaudio.com/threads/is-it-possible-to-bypass-the-preamp.70487/page-2#post-865226]
# "If you only need power amp modeling, for example when using an external pre-amp through the Axe-Fx, use the Tube Pre model. It uses the Vintage tonestack which is flat when the tone controls are at noon."
# "The "Vintage" tone stack is flat. The Tube Pre model uses the Vintage tone stack." [https://forum.fractalaudio.com/threads/is-it-possible-to-bypass-the-preamp.70487/#post-865192]
# (firmware Ares 14.00) "The Tube Pre model has been changed so that the power amp is off by default."

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-tube-pre.115357/ Yek's write-up]

==TWO STONE J35 (Two-Rock Jet 35)==

[[file:jet35.jpg‎|300px]]

Models:
* Lead mode, Preamp Bypass (PAB) OFF
* Lead mode, Preamp Bypass ON (tone controls bypassed)

[[Cabinet models list | Cab:]] Two Stone 2x12 (G12-65)

Treble, Mid, Bass, Gain, Master, Lead Gain, Pull Bright. No Presence on the original amp, but the model has a Presence control

Power tubes: 6L6

# "It's very smooth but there's this unique chirp or something that I've never heard in an amp before. When you hit the note there's this blast of high end that rapidly decays so it has an almost vocal quality. The frequency shaping is very different than most other amps." [https://forum.fractalaudio.com/posts/745084]
# "The Two Rock is the most unique amp I've ever modeled. Almost like a violin but with this really cool chirp on the pick attack." [https://forum.fractalaudio.com/posts/747921]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-two-stone-j35-two-rock-jet-35.115377/ Yek's write-up]

==TWO STONE J35 PAB==

==USA BASS 400 1 (MESA Bass 400 bass amp)==

[[file:mesabass400.jpg|300px]]

Models:
* Bass Shift OFF
* Bass Shift ON

[[Cabinet models list | Cab:]] Mesa bass speaker cabinet

Bass, Middle, Treble, Pull Bright, Bass Shift, Treble Shift (not modeled), 7-band GEQ, Master, Volume

Power tubes: 6550

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-usa-bass-400-mesa-bass-400.115439/ Yek's write-up]

==USA BASS 400 2==

==USA MK IIC+ (MESA/Boogie Mark IIC+)==

[[file:iic+.jpg|300px]]

IIC+ models:
* Lead Master with Pull Bright engaged
* Lead Master with Pull Bright off
* Lead Master with Pull Deep engaged
* Lead Master with Pull Deep off

[[Cabinet models list | Cab:]] Mesa 1x12 (C90, EVM)

Volume (pull: Bright), Treble (pull: Shift = Fat), Bass (pull: Shift, not modeled), Middle, Presence, Master rhythm (pull: Deep), Lead Drive and Master Lead (pull: Bright)

Power tubes: 6L6

# "The mode in the Mark V is based on the later SimulClass version." [https://forum.fractalaudio.com/posts/910018]
# "If you want the sound of the non-SimulClass version set Triode 1 Plate Freq to 1350 Hz." [https://forum.fractalaudio.com/posts/910386]
# "The Pull Bright on the Volume knob is the classic "Bright Cap" which engages a capacitor across the potentiometer. This is already modeled in the Axe-Fx via the Bright Switch. The Pull Bright on the Lead Master knob engages a 0.22uF cap on the cathode of the last triode in the overdrive circuit. As there is no switch for this in the Axe-Fx it requires a separate model. Cathode caps are very common in tube amps. If the value is large the stage has more gain and the response is relatively flat. If the value is small the stage has more gain at higher frequencies. Amp designers use cathode caps to shape the frequency response. Caps in the range of 0.1 to 1.0 uF are commonly used to reduce bass response. A cathode cap works by decreasing the amount of negative feedback through shunting higher frequencies to ground. This reduced negative feedback increases the gain (and reduces linearity). FWIW the Axe-Fx is the only modeler of which I'm aware that actually models triodes using a feedback technique. Other modelers use static waveshapers. The Axe-Fx triode models incorporate feedback so if there is a virtual cathode cap the stage is less linear in addition to having more gain." [https://forum.fractalaudio.com/posts/1186462]
# "The IIC+ does not have a gain boost and doesn't need one. There is plenty of gain. The Pull Deep switch engages a large cathode cap on the final triode stage. With Pull Deep off there is actually a shelving response into the power amp (bass is reduced)."
# (to emulate Pull Shift on the Bass) "Put a Tilt EQ before the amp block with a frequency of 320 Hz and a gain of -3 dB. Set the Level to +3 dB." [https://forum.fractalaudio.com/posts/1202633]
# "I have a Mark IIC+, a Mark IV, a Mark V and a Triaxis. They're all completely different. Mesa always says things like "sounds the same as a IIC+" but the circuits are different and, probably most important, the knob tapers are completely different." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-2-00-public-beta-numero-tres.109852/page-6#post-1315609]
# "The key to a good Boogie sound, IMO, is the Fat Switch. This is the treble Pull Shift on the IIC+ and the Pull Fat on the Mark IV. Mesa knew this and the Lead 2 modes on the Triaxis all had the treble shift engaged by default."
# "I always used the Fat switch with the real amp." (IIC+) [http://forum.fractalaudio.com/threads/mark-iic-amp-model-issues.121463/page-2#post-1446683]
# "On a Mark IV (at least on our reference amp) all three controls have a Log10A taper. On a Mark V the tapers are different so you get more midrange and treble for the same settings. Channel 3 on a Mark V is virtually identical to the Mark IV Lead channel except for the pot tapers." [https://forum.fractalaudio.com/threads/question-about-the-mark-series-graphic-eq-modeling.149223/post-1771767]
# "The IIC++ amp model is the same as the IIC+ with different tapers." [https://forum.fractalaudio.com/threads/question-about-the-mark-series-graphic-eq-modeling.149223/post-1770773]
# "The tone stack on a Boogie is pre-distortion. As you increase gain you want less bass into the distortion stages so the idea is you turn the bass down. In later versions of the Boogies (TriAxis for example) they changed the taper so that noon was equivalent to 1 on earlier models because people are reticent to move controls very far from noon for some weird reason." [https://forum.fractalaudio.com/threads/highly-compressed-sound-on-high-gain-amps.169132/post-2032825]
# "I begrudgingly dragged the amp out of storage today (as it weighs a metric ton) and repeated the measurements and did some A/B tests. As expected the models are extremely accurate. That being said it is a bear to dial in. Here are some tips:
#* The old version of the model incorrectly referenced the Mark IV tone stack. These tone stacks are identical except for the taper of the mid pot. The IIC+ has a linear pot and the Mark IV has a Log10 pot. I had it backwards in my earlier comments. My guess is that Mesa found that turning the midrange down sounds best (and it does) so they changed the pot taper to do this automatically since noon on a Log10 pot is equal to a 1.0 on a linear pot.
#* Commensurate with (1) I found myself turning the midrange down as well as the bass and turning the treble up.
#* I think the default Master Volume value is a bit high so you may want to turn that down. I've reduced the default for Quantum 2.03.
#* Turn the bright switch on. Every bit of information I've found says that people typically used the Pull Bright on the Volume knob. This is equivalent to the Bright switch under the Treble control on the model. I always turn it on and I've set it on by default for Q2.03.
#* USE THE EQ. The tone stack is pre-distortion which is atypical for a high-gain amp. Tone stacks are almost always post-distortion. Since the tone stack is pre-distortion you need to do your post distortion tone shaping using the EQ. The tone controls set the feel and the distortion texture, the EQ shapes the final tone. I like to do a gentle V-curve.
#* These were my settings for a killer high-gain tone: Model: USA IIC+ / Input Drive: 8.1 / Overdrive: 9-10 / Bass: 1.0 / Midrange: 1.8 / Treble: 8.9 / Presence: 4.5 / MV: 4.0 / Level: -20 dB / Bright Switch ON / 80 Hz: 4.8 / 240 Hz: 2.6 / 750 Hz: -4.5 / 2200: -0.2 / 6600: 0." [http://forum.fractalaudio.com/threads/mark-iic-tips.112378]
# "Treble Shift on the Tone page of USA IIC+ models is an alias of the “Fat” control found on the Preamp page and performs the same function." (firmware 22)

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-usa-iic-mesa-boogie-mark-iic.115442/ Yek's write-up]

==USA MK IIC+ BRIGHT==

==USA MK IIC+ DEEP==

==USA MK IIC+ DEEP BRIGHT==

==USA MK IIC++ (custom model of MESA/Boogie IIC+)==

[[File:Logo small.png]]

Formerly: METALLICA USA IIC++

This is not a model of Hetfield's own "crunchberries" amp, nor a model of a IIC+ with the IIC++ mod. It's the IIC+ model with different tapers. This was requested by Metallica's engineers after the main IIC+ models were updated, and it's part of Metallica's live sound.

Notes: see USA IIC+

# (from Metallica engineers) "This model is part of our live sound. This amp was removed when the new MKII models were added and firmware updated. I asked if it could be ported for Q3 as I was having a difficult time migrating to the updated firmware and retaining our earlier work." [https://forum.fractalaudio.com/threads/metallica-amp.115857/page-2#post-1384750]
# "The IIC++ amp model is the same as the IIC+ with different tapers." [https://forum.fractalaudio.com/threads/question-about-the-mark-series-graphic-eq-modeling.149223/post-1770773]

==USA JP IIC+ Green (MESA/Boogie JP-2C)==

[[File:Jp2c.jpg|300px]]

JP-2C models:
* Green: channel 1
* Red: channel 3
* Red: channel 3, Shred mode
* Yellow: channel 2
* Yellow: channel 2, Shred mode

Channel 1 (Mark IIC+ Clean): Gain, Master, Presence, Treble, Mid, Bass, Mid/Boost switch, graphic EQ, reverb (not modeled)

Channel 2 (Mark IIC+ Gain/Shred): (Pull) Gain, Master, (Pull) Presence, Treble, Mid, Bass, graphic EQ (not modeled), Shred mode switch

Channel 3 (Mark IIC+ Gain/Shred): (Pull) Gain, Master, (Pull) Presence, Treble, Mid, Bass, graphic EQ (not modeled), Shred mode switch

Power tubes: 6L6

# "The JP amp has a fixed input gain control. The "Gain" control on the amp is actually an Overdrive control. If you use Authentic controls there is no Input Gain on "Gain"." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-03.149363/page-3#post-1772020]
# "Presence Shift is Presence pull. Tone stack effectively has fat switch on." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-05.149428/page-10#post-1775746]
# (difference between the "JP Green" and "USA Clean") "JP has less gain and a much larger midrange potentiometer." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-06.149775/page-2#post-1777979]
# "JP himself gave the models his stamp of approval." [http://forum.fractalaudio.com/threads/i-am-confused-about-the-jp2c.153540/post-1826396]
# "JP (Green) has less gain (than USA Clean) and a much larger midrange potentiometer." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-06.149775/post-1777979]
# "Those are great amps. The particular amp used for the models was John Petrucci's personal recording amp. I didn't want to give it back and offered to buy it from him but he wouldn't sell it." [https://www.thegearpage.net/board/index.php?threads/fractal-fm3-reviews-tones-questions.2124913/post-31011638]
# "It's not that the Graphic EQ isn't the same, the TAPERS are not the same. On the real amp the controls do virtually nothing until you get near the ends of the range. If you move a slider to, say, 3/4 of its range it does almost nothing. If you were to set the model's slider to the same position you would get significantly more boost. I didn't model the nonlinear slider behavior because IMO it's a design flaw. Graphic EQs should have a nice, linear-in-dB response. Otherwise the graphic EQ is very accurate. The frequency and Q behavior is spot-on. If you have pulled the presence knob on the amp you have to activate the Presence Shift on the model. Otherwise they will sound VERY different. Presence shift gives a much more focused sound. I always use the Presence Shift. You can't compare the amp with a switch engaged to the model without the equivalent switch engaged. Of course it will sound different. The tapers of the other controls should be very close including the Presence and Master Volume. (...) JP himself was very impressed with the model and the model was matched to his PERSONAL head that he sent me." [https://forum.fractalaudio.com/threads/real-jp2c-vs-axe-fx-3-sim-comparison.168942/post-2029916]</blockquote>
# "I thought that Shred mode is the same as the Red mode on the Triaxis which is just a treble boost on the output when, in fact, it's a clean boost on the input similar to a Tube Screamer but without the treble rolloff." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486/post-2067465]
# (about the fixed internal gain) "Yellow is 2.9. Red is 5.7." [https://forum.fractalaudio.com/threads/axe-fx-iii-16-00-beta-11-cygnus-firmware-public-beta-8.171486/post-2067603]
# "JP2C doesn't have a depth knob. If a knob isn't present in the Authentic menu then it may not do anything in the Ideal menu." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-release-version-16-01-beta-1-public-beta.172736/post-2088439]
# "USA JP models have a fixed Input Drive so when switching to the models the Input Drive is reset to the default value. The Input Drive knob is not visible in the Authentic menu." [https://forum.fractalaudio.com/threads/bug-presence-not-working-at-the-usa-lead-models-triaxis-16-1-b.172777/post-2088655]
# "A JP IIC+ is not a Mark IV. They sound different. The biggest difference is in the behavior of the Presence Shift. With the Presence Shift on the JP IIC+ will be very similar to the Mark IV with its Presence Shift on. With the Presence Shifts off they are very different sounding." [https://forum.fractalaudio.com/threads/jp-ii-c-red-sounds-muffled-compared-to-mk-iv-mid-gain-in-fw-21-00-with-audio-and-preset.191858/post-2385695]
# "All these amps have the same basic circuit with minor differences. The only unique thing I've encountered in all my tests is the function of the Presence Shift pull on the JP2C. It's different than the pull shift on the other Mark amps." [https://forum.fractalaudio.com/threads/mesa-mark-iic-mark-iic-mark-vii-the-jp2c-mark-iic.192824/post-2398526]

==USA JP IIC+ Red==

==USA JP IIC+ Red Shred==

==USA JP IIC+ Yellow==

==USA JP IIC+ Yellow Shred==

==USA MK IV LEAD / RHYTHM (MESA/Boogie Mark IV)==

[[file:markiv.jpg|300px]]

Mark IV models:
* Rhythm 1 channel (previously: USA Clean model)
* Rhythm 2 channel
* Lead channel, Voicing: Harmonics, Pull Bright: engaged
* Lead channel, Voicing: Mid Gain, Pull Bright: engaged
* Lead channel, Voicing: Harmonics, Pull Bright: off
* Lead channel, Voicing: Mid Gain, Pull Bright: off

[[Cabinet models list | Cab:]] Mesa 1x12 (C90, V30)

Gain, Lead Drive, Treble, Bass, Mid, Presence, Master, graphic EQ, Pentode/Triode switch, Class-A/Simul-Class switch, Voicing switch (Mid Gain / Harmonics), Variac

Rhythm 1 channel: Pull Bright

Rhythm 2 channel: Pull Fat, Presence Shift

Lead channel: Pull Bright, Pull Fat, Presence Shift

Power tubes: 6L6

# "The MK V is basically a compendium of previous Mesa amps. There may be minor differences in tone due to circuit layout but nothing a few tweaks to the EQ can't fix." [https://forum.fractalaudio.com/posts/573437]
# “A Mark V is a greatest hits of the Mark IV and IIC+. You already have all those models.” [https://forum.fractalaudio.com/threads/wish-list-new-amps.137944/post-1991426]
# "Having owned multiple Mark IV's, multiple Triaxis's and a variety of other Boogie products, I can tell that the Mark series in general are a bitch to dial in. Once you figure them out though they are great amps. IMO, the key to a MKIV is to use the TMB to get the feel and the EQ to get the tone."
# "If it isn't Mid Gain then it's Harmonics." [https://forum.fractalaudio.com/posts/1165578]
# "The Depth knob is inactive on that amp model. The real amp doesn't have one either." [https://forum.fractalaudio.com/posts/1205835]
# "Fat and Presence shift work as the real amp." [https://forum.fractalaudio.com/posts/1246666]
# "USA Clean is based on the MKIV." [http://forum.fractalaudio.com/threads/mesa-iic-clean-channel.106851/#post-1280186]
# "With the presence control at noon it's roughly neutral. Turn it down and you are actually boosting bass and reducing treble." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-1-03-firmware-release.106931/page-12#post-1282192]
# "I have a Mark IIC+, a Mark IV, a Mark V and a Triaxis. They're all completely different. Mesa always says things like "sounds the same as a IIC+" but the circuits are different and, probably most important, the knob tapers are completely different." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-2-00-public-beta-numero-tres.109852/page-6#post-1315609]
# "The key to a good Boogie sound, IMO, is the Fat Switch. This is the treble Pull Shift on the IIC+ and the Pull Fat on the Mark IV. Mesa knew this and the Lead 2 modes on the Triaxis all had the treble shift engaged by default."
# "There isn't any way to run the virtual power tubes in triode mode... but you can change the Power Tube Type to "300B" which is a triode. When you run a pentode (or beam tetrode) in triode mode you connect the screen to the anode which effectively defeats the screen. This lowers the output impedance of the plate significantly which, in turn, lowers the output impedance of the amp itself making the voltage output less dependent on the speaker impedance. Using the 300B tube type should get you pretty close." [http://forum.fractalaudio.com/threads/mesa-mark-iv-pentode-triode-switch.122527/#post-1458293]
# (about the GEQ) "The range of the sliders is the same as the amp. The taper is not. The amp is much more abrupt since it uses linear taper (should use 'S'-taper)." [https://forum.fractalaudio.com/threads/question-about-the-mark-series-graphic-eq-modeling.149223/post-1769764]
# (about the difference between the "JP Green" and "USA Clean") "JP has less gain and a much larger midrange potentiometer." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-5-06.149775/page-2#post-1777979]
# (simulate Class-A mode) "Turn Power Tube Grid Bias all the way up." [https://forum.fractalaudio.com/threads/mesa-mk-4-class-a-possible.154438/post-1836241]
# "The tone stack on a Boogie is pre-distortion. As you increase gain you want less bass into the distortion stages so the idea is you turn the bass down. In later versions of the Boogies (TriAxis for example) they changed the taper so that noon was equivalent to 1 on earlier models because people are reticent to move controls very far from noon for some weird reason." [https://forum.fractalaudio.com/threads/highly-compressed-sound-on-high-gain-amps.169132/post-2032825]
# "A JP IIC+ is not a Mark IV. They sound different. The biggest difference is in the behavior of the Presence Shift. With the Presence Shift on the JP IIC+ will be very similar to the Mark IV with its Presence Shift on. With the Presence Shifts off they are very different sounding." [https://forum.fractalaudio.com/threads/jp-ii-c-red-sounds-muffled-compared-to-mk-iv-mid-gain-in-fw-21-00-with-audio-and-preset.191858/post-2385695]
# "Mark V is the same thing as a Mark IV w/ a few extra features. They sound virtually identical." [https://forum.fractalaudio.com/threads/axe-fx-firmware-version-21-02.191637/post-2382608]
# "The amp uses linear taper sliders. The ideal taper for this type of circuit is S-taper. S-taper will give you approximately linear-in-dB. The Axe-Fx III is precisely linear-in-dB." [https://forum.fractalaudio.com/threads/mark-series-eq.191595/post-2389621]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-usa-clean-lead-rhythm-mesa-boogie-mark-iv.115440/ Yek's write-up]

==USA MK IV LEAD BRIGHT==

==USA MK IV LEAD MID GAIN==

==USA MK IV LEAD MID GAIN BRIGHT==

==USA MK V GREEN==

==USA PRE CLEAN (MESA TriAxis preamp)==

[[file:triaxis.png|300px]]

Triaxis models:
* Rhythm Green
* Lead 1 Red (TX-4 board)
* Lead 2 Green
* Lead 2 Red
* Lead 2 Yellow

Drive, Lead Drive, Treble, Middle, Bass, Presence (preamp, on Lead 2 models), Dynamic Voice EQ (not modeled)

Power tubes: same as USA Lead model (6L6)

# "I used a Triaxis for, shoot, I dunno, over a decade before designing the Axe-Fx. I have two of them. So I'd say I'm pretty familiar with the tones. To my ears (and my measurement equipment), the Axe-Fx models are spot-on."
# "I can nail the sound of my Triaxis now by setting it (Bright) around 9:00 - 10:00." [https://forum.fractalaudio.com/posts/1001906] And: "10 on the Triaxis would be 0 dB on the Bright parameter. Anything below 10 is equivalent to less than noon on the Bright parameter. The "Presence" control on a Triaxis is always a hi cut, it never boosts. The Bright parameter is not an exact match to the Triaxis Presence control though. It is a fixed shelving filter. The Triaxis Presence control is passive so the center frequency changes with the amount of cut. It also changes the load on the plate which distorts the frequency response a bit too. The Presence parameter should be set to 5.00, which is neutral (see the manual for details)."
# "I have a Mark IIC+, a Mark IV, a Mark V and a Triaxis. They're all completely different. Mesa always says things like "sounds the same as a IIC+" but the circuits are different and, probably most important, the knob tapers are completely different." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-2-00-public-beta-numero-tres.109852/page-6#post-1315609]
# "The key to a good Boogie sound, IMO, is the Fat Switch. This is the treble Pull Shift on the IIC+ and the Pull Fat on the Mark IV. Mesa knew this and the Lead 2 modes on the Triaxis all had the treble shift engaged by default."
# "Mesa claims it's based on the IIC+ but it's different. The bright cap is different, the mid resistor is much greater, the source impedance of the drive "pot" is different, etc., etc, etc." [http://forum.fractalaudio.com/threads/three-hours-with-the-usa-pre-ld2-yellow.111624/#post-1335224]
# (firmware Quantum 7) "The USA Pre models now all use a MarkIV power amp model. The 2:90 power amp is basically the same as a MarkIV and does have a presence shift but it's accessed through a jack on the back (Voicing)." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-00-firmware-release.124944/page-15#post-1487194]
# "I gigged with a Triaxis for years. I never put Dynamic Voice above 1.0. Despite it's name, DV is just an EQ. It's the 5-band graphic EQ from the mark series with the potentiometers replaced by LDRs. It's really just a bunch of EQ presets and it interpolates between them as you increase the value." [http://forum.fractalaudio.com/threads/triaxis-model-live-use.147163/#post-1740122]
# "I have two of them. Both with the Lead 1 Red board." [https://forum.fractalaudio.com/threads/the-triaxis-is-spot-on.151673/post-1804830]
# "On our reference Triaxis (both of them) the Presence control doesn't do anything for the Clean and LD1 modes. The model's Presence knob is therefore the Power Amp Presence." [https://forum.fractalaudio.com/threads/triaxis-usa-pre-models-inconsistencies-in-controls.156431/post-1862912]
# "That's how our reference amps work. They are the later models with the TX4 board (different LD2 Red). When using the LD1 modes the Presence control doesn't do anything and is as if the control were at 10." [https://forum.fractalaudio.com/threads/triaxis-usa-pre-models-inconsistencies-in-controls.156431/post-1865080]
# "The tone stack on a Boogie is pre-distortion. As you increase gain you want less bass into the distortion stages so the idea is you turn the bass down. In later versions of the Boogies (TriAxis for example) they changed the taper so that noon was equivalent to 1 on earlier models because people are reticent to move controls very far from noon for some weird reason." [https://forum.fractalaudio.com/threads/highly-compressed-sound-on-high-gain-amps.169132/post-2032825]
# "Based on the Lead 1 Red mode of a Mesa Triaxis preamp with the TX-4 board."
# In "Cygnus" amp modeling firmware the Lead models have an authentic Preamp Presence control (not in the Lead 1 model).
# "I gigged a Triaxis for years and I would have the knobs pretty much at noon (5.0). The Triaxis is a Mark IV preamp under the hood but with very different tapers on the "pots". I.e., with BMT at 5.0 on the Triaxis the MKIV would be something like 1.0, 6.0, 6.0. I'm just going by memory here but the point being that the bass control on the Triaxis doesn't need to be turned way down like you would on a Mark series." [https://forum.fractalaudio.com/threads/bad-experience-with-choptones-i-need-a-2nd-opinion-watch-screenshots-plz.191948/post-2386734]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-usa-pre3-mesa-boogie-triaxis.115478/ Yek's write-up]

==USA PRE LD1 RED (TX-4 board)==

==USA PRE LD2 GREEN==

==USA PRE LD2 RED==

==USA PRE LD2 YELLOW==

==USA MK IV RHYTHM 1==

==USA MK IV RHYTHM 2==

==USA SUB BLUES (MESA Subway Blues)==

[[file:subwayblues.png|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Mesa 1x10 (Eminence Black Shadow), DynaCab available

Volume, Bass, Mid, Treble, FAT switch, Reverb (not modeled)

Power tubes: EL84

# "The Subway Blues model was completely redone. It will likely sound different than before." [https://forum.fractalaudio.com/threads/bug-mesa-subway-blues-very-different-in-ares-15-01-vs-cygnus-16-00.172363/post-2082472]
# "The reference amp is the later, single input version. The Fat switch replicates the amp's Fat switch." [https://forum.fractalaudio.com/threads/bug-mesa-subway-blues-very-different-in-ares-15-01-vs-cygnus-16-00.172363/post-2088907]

[http://forum.fractalaudio.com/threads/usa-sub-blues-mesa-boogie-subway-blues.115479/ Yek's write-up]

==VIBRA-KING (custom Fender Vibro-King)==

[[file:vibro-king.jpg|300px]]

Models:
* Fat switch ON
* Fat switch OFF

Volume, Treble, Bass, Middle, Fat switch, Tremolo, Reverb (not modeled)

[[Cabinet models list | Cab:]] Fender 3x10

Power tubes: 6L6

# "The model is based on the custom version which has higher plate voltages which causes more overdrive on the power tubes."

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-vibra-king-custom-fender-vibro-king.115485/ Yek's write-up]

==VIBRA-KING FAT==

==VIBRATO LUX (1962/1963 brownface Fender Vibrolux, 6G11)==

[[file:vibrolux.jpg|300px]]

Model:
* Bright channel (Normal channel: Bright OFF)

[[Cabinet models list | Cab:]] Fender 2x10 or 1x12

Vibrato channel: Volume, Bass, Treble, Vibrato (not modeled)

Power tubes: 6L6

# "Early Dire Straits tone is a Vibrolux (Vibrato Lux model). The Vibrato Lux model is based on the same model and year amp used on the eponymous album. There's a cab in there too." [https://forum.fractalaudio.com/posts/1111550]
# "It's a Vibrolux. That IR is from my personal 1962 Vibrolux. This is the amp used on Dire Straits eponymous album." [https://forum.fractalaudio.com/threads/vibrolux-g3-with-the-new-ir-is-just-ridiculous.97866/#post-1174387]
# "It's a Brownface." [https://forum.fractalaudio.com/threads/brownface-deluxe-or-closest-thing-to-it.80014/#post-973252]
# "Our reference amp is the same model Mark Knopfler used on the Dire Straits eponymous album. Match made in heaven with a Strat." [https://forum.fractalaudio.com/threads/definitely-a-problem.173700/post-2103923]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-vibrato-lux-fender-vibrolux-6g11.115713/ Yek's write-up]

==VIBRATO VERB (Fender Vibroverb)==

[[image:vibroverb.jpg|300px]]

Vibroverb models:
* Vibrato Verb: old model ported from the Axe-Fx Ultra
* Vibrato Verb AA: based on Cliff’s own 1964 blackface Vibroverb with AA763 circuit
* Vibrato Verb AB: based on AB763 circuit
* Vibrato Verb Custom: based on Custom Reissue

[[Cabinet models list | Cab:]] Fender 1x15 (Jensen C15N, JBL D130, Eminence)

Volume, Bass, Treble, Bright switch, Reverb (not modeled), Tremolo

Power tubes: 6L6

# "The Transformer Matching value for the CS model is based on the output transformer in the actual amp. Legend has it that SRV used a Bassman transformer which would lead to significant overmatching. To replicate this increase Xfrmr Match to around 1.8."
# "Some different component values in the AA vs. AB." [https://forum.fractalaudio.com/threads/vibrato-verb-models-explained.192318/post-2391593]
# "The 1x15 Vibroverb is a D130." [https://forum.fractalaudio.com/threads/what-dyna-cab-models-would-you-like-to-see-added.193380/post-2404043]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-vibrato-verb-fender-vibroverb.115734/ Yek's write-up]

==VIBRATO VERB AA (1964 blackface Fender Vibroverb, AA763)==

==VIBRATO VERB AB (Fender Vibroverb, AB763)==

==VIBRATO VERB CUSTOM (Fender Vibroverb Custom Reissue)==

==WRECKER EXPRESS (Trainwreck Express)==

[[file:trainwreck.jpg|300px]]

Models:
* Wrecker Express: Bright switch on original amp in center or top position
* Wrecker Express Bright: Bright switch on original amp in bottom (brightest) position

[[Cabinet models list | Cab:]] Marshall 4x12 (G12-M25)

Power tubes: EL34

Volume, Bass, Mid, Treble, Presence, three-position Bright switch (center: off, top: clarity and sparkle, bottom: jangly highs)

# "The secret to a Trainwreck is the output transformer. The impedance ratio is about twice that of other amps. I.e. typical 50W Marshall has a primary impedance of about 3200 ohms. A Trainwreck is about 6500 ohms. The causes the power tubes to clip much sooner." [https://forum.fractalaudio.com/posts/1116254]
# "Real Trainwrecks are very spitty amps. This is because the last stage heavily overdrives the phase inverter. 7.02 is faithful to the actual amps whereas previous firmwares were more idealized. As was indicated in the release notes you can dial out this behavior by decreasing the PI Bias Shift. If you set it to zero it will be like 6.xx." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-02-firmware-release.125625/page-17#post-1498318]
# [https://forum.fractalaudio.com/threads/trainwreck-express-tweaks.154796/post-1841547 Cliff's Tech Note]: "A real Trainwreck Express is a fizzy, spitty amp. Some people like this. The same people who like fuzz pedals and that quasi-half-wave rectified sound. Personally I like more clarity. The reason the Express is like this is primarily due to the last triode stage before the phase inverter (PI). This stage is biased very cold and drives the PI very hard due to the lack of any limiting resistor (grid stopper) between the triode and PI. The lack of a grid stopper resistor and large coupling capacitor create significant bias excursion (blocking distortion). It appears the designer attempted to minimize the bias excursion by biasing the triode cold which limits its positive excursion and therefore limits the PI grid conduction. Despite the cold bias point the PI grid is still heavily overdriven resulting in massive blocking distortion. The Axe-Fx allows you to reduce the amount of block distortion via the PI Bias Excursion parameter. Simply turn this down and the spittiness will go away. You can then also rebias the triode via the Preamp Bias parameter. Values closer to zero result in a more symmetric waveform." (...) "Turn PI Bias Excursion to 0. Set Preamp Bias to -0.15 or so. [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841487]"
# "The reason they clean up when you back off the volume is because the OT is so overmatched. It's about twice the optimum value." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841485]
# "The real amp is a nasty thing. Very spitty as one would expect given the lack of a grid stopper resistor between the last triode stage and the PI." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841549]
# "Got out the reference amp and it sounds the same. For all the hoopla surrounding Trainwrecks they're actually pretty bad designs. Tons of blocking distortion in the PI. If you don't want all that blocking distortion turn down PI Bias Excursion." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/page-4#post-1841474]
# "Turning down PI Bias Excursion yields the ultimate Trainwreck. Sounds much better than the real amp. I also adjusted the Preamp Bias so it wasn't so off-center." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/page-4#post-1841480]
# "The only difference (between the two Express models) is the Bright Cap. An Express (at least mine) has a three-position switch: Off, 100 pF, 500 pF. The amp block only supports Off and On and I figured people wouldn't know the fine details so a separate model seemed the easiest solution. Of course you can vary the Bright Cap but you'd have to know that the real amp has two caps, etc." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-version-10-01.154923/post-1843572]
# "That amp exhibits a lot of blocking distortion (in the phase inverter) due to its design. You can reduce this via either the PI Bias Excursion or Master Bias Excursion parameters. Another option is to use the FAS Express model which puts some resistors between the last triode stage and the PI to reduce the bias excursion." [https://forum.fractalaudio.com/threads/blocking-distortion-found-in-trainwreck-express.182895/post-2247268]
# "I got out my Trainwreck Express and compared it to the model last night and it's spot-on. Nasty, spitty, Neil Young-esque blocking distortion and all." [https://forum.fractalaudio.com/threads/blocking-distortion-found-in-trainwreck-express.182895/post-2247538]
# "That's what amps do. You don't hear it through a guitar cab typically but using close-mic'd IRs it's more noticeable. You can reduce it by turning on the Plate Suppressor diodes. Trainwrecks have plate suppressor diodes for just this reason." [https://forum.fractalaudio.com/threads/note-decay-crackle-sizzle-noise.193575/post-2407689]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-wrecker-express-trainwreck-express.115740/ Yek's write-up]

==WRECKER EXPRESS BRIGHT==

==WRECKER LIVERPOOL (Trainwreck Liverpool)==

[[file:trainwreck.jpg|300px]]

Models:
* Liverpool: Bright switch on original amp in center or top position
* Liverpool Bright: Bright switch on original amp in bottom (brightest) position

[[Cabinet models list | Cab:]] Marshall 4x12 (G12-M25)

Volume, Bass, Mid, Treble, Presence, three-position Bright switch (center: off, top: clarity and sparkle, bottom: jangly highs)

Power tubes: EL84

# "The secret to a Trainwreck is the output transformer. The impedance ratio is about twice that of other amps. I.e. typical 50W Marshall has a primary impedance of about 3200 ohms. A Trainwreck is about 6500 ohms. The causes the power tubes to clip much sooner." [https://forum.fractalaudio.com/posts/1116254]
# "Just because a power amp is "Class A" doesn't mean it can't have negative feedback. True that the majority do not but this particular amp has quite a bit of NF." [http://forum.fractalaudio.com/threads/wrecker-liverpool-neg-feedback-bug.116224/#post-1389082]
# "Uses a Vox-style phase inverter." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-00-public-beta.123082/page-7#post-1464730]
# "Real Trainwrecks are very spitty amps. This is because the last stage heavily overdrives the phase inverter. 7.02 is faithful to the actual amps whereas previous firmwares were more idealized. As was indicated in the release notes you can dial out this behavior by decreasing the PI Bias Shift. If you set it to zero it will be like 6.xx." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-02-firmware-release.125625/page-17#post-1498318]
# [https://forum.fractalaudio.com/threads/trainwreck-express-tweaks.154796/post-1841547 Cliff's Tech Note]: "A real Trainwreck Express is a fizzy, spitty amp. Some people like this. The same people who like fuzz pedals and that quasi-half-wave rectified sound. Personally I like more clarity. The reason the Express is like this is primarily due to the last triode stage before the phase inverter (PI). This stage is biased very cold and drives the PI very hard due to the lack of any limiting resistor (grid stopper) between the triode and PI. The lack of a grid stopper resistor and large coupling capacitor create significant bias excursion (blocking distortion). It appears the designer attempted to minimize the bias excursion by biasing the triode cold which limits its positive excursion and therefore limits the PI grid conduction. Despite the cold bias point the PI grid is still heavily overdriven resulting in massive blocking distortion. The Axe-Fx allows you to reduce the amount of block distortion via the PI Bias Excursion parameter. Simply turn this down and the spittiness will go away. You can then also rebias the triode via the Preamp Bias parameter. Values closer to zero result in a more symmetric waveform." (...) "Turn PI Bias Excursion to 0. Set Preamp Bias to -0.15 or so. [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841487]"
# (about the Tech Note) "Applies to the Liverpool because the preamp is almost identical to the Express." [https://forum.fractalaudio.com/threads/trainwreck-express-tweaks.154796/post-1842967]
# "The reason they clean up when you back off the volume is because the OT is so overmatched. It's about twice the optimum value." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841485]
# "Turning down PI Bias Excursion yields the ultimate Trainwreck. Sounds much better than the real amp. I also adjusted the Preamp Bias so it wasn't so off-center." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/page-4#post-1841480]
# "That's what amps do. You don't hear it through a guitar cab typically but using close-mic'd IRs it's more noticeable. You can reduce it by turning on the Plate Suppressor diodes. Trainwrecks have plate suppressor diodes for just this reason." [https://forum.fractalaudio.com/threads/note-decay-crackle-sizzle-noise.193575/post-2407689]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-wrecker-liverpool-trainwreck-liverpool.115741/ Yek's write-up]

==WRECKER LIVERPOOL BRIGHT==

==WRECKER ROCKET (Trainwreck Rocket)==

[[file:trainwreck.jpg|300px]]

Model:
* Single channel

[[Cabinet models list | Cab:]] Marshall 4x12 (G12-M25)

Volume, Treble, Bass, Cut

Power tubes: EL84

# "The secret to a Trainwreck is the output transformer. The impedance ratio is about twice that of other amps. I.e. typical 50W Marshall has a primary impedance of about 3200 ohms. A Trainwreck is about 6500 ohms. The causes the power tubes to clip much sooner." [https://forum.fractalaudio.com/posts/1116254]
# "The Rocket has a different preamp (than the Express) with the tone stack before the PI. This reduces the signal level substantially and lessens the amount of blocking distortion." [https://forum.fractalaudio.com/threads/trainwreck-express-tweaks.154796/post-1842967]
# "The reason they clean up when you back off the volume is because the OT is so overmatched. It's about twice the optimum value." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/post-1841485]
# "Real Trainwrecks are very spitty amps. This is because the last stage heavily overdrives the phase inverter. 7.02 is faithful to the actual amps whereas previous firmwares were more idealized. As was indicated in the release notes you can dial out this behavior by decreasing the PI Bias Shift. If you set it to zero it will be like 6.xx." [http://forum.fractalaudio.com/threads/axe-fx-ii-quantum-rev-7-02-firmware-release.125625/page-17#post-1498318]
# "Turning down PI Bias Excursion yields the ultimate Trainwreck. Sounds much better than the real amp. I also adjusted the Preamp Bias so it wasn't so off-center." [https://forum.fractalaudio.com/threads/axe-fx-iii-firmware-10-00-public-beta-2.154782/page-4#post-1841480]
# "That's what amps do. You don't hear it through a guitar cab typically but using close-mic'd IRs it's more noticeable. You can reduce it by turning on the Plate Suppressor diodes. Trainwrecks have plate suppressor diodes for just this reason." [https://forum.fractalaudio.com/threads/note-decay-crackle-sizzle-noise.193575/post-2407689]

[http://forum.fractalaudio.com/threads/fractal-audio-amp-models-wrecker-rocket-trainwreck-rocket.114726/ Yek's write-up]

[[category:Axe-Fx2]]
[[category:Axe-Fx3]]
[[category:FM3]]
[[category:FM9]]
[[category:AX8]]
[[category:Sounds]]
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