Always consult the Owners Manuals and the FAQ first...

Drive block

From Axe-Fx II Wiki
Jump to: navigation, search

Contents

Drive block.PNG

Available on which products

  • Axe-Fx III: 4 blocks
  • Axe-Fx II: 2x blocks
  • AX8: 2 blocks
  • FX8: 2 blocks

X/Y and channels

  • Axe-Fx III: 4 channels
  • Axe-Fx II: X/Y
  • AX8: X/Y
  • FX8: X/Y

Yek's Guide to the Fractal Audio Drive models

Forum member Yek has written a guide (PDF) that covers all Drive models in detail. Click on the image below.

Yeks Drives Guide.png

Drive block modeling in the Axe-Fx III

The number of Drive blocks has been increased to 4 in the Axe-Fx III. With each Drive block containing 4 channels, that’s 16 (!) drives per preset.

Also, some of the Drives have been integrated into the Amp block as clean boosts (“Drive on 0") with adjustable level. Read this.

A Graphic EQ has been added.

"The drive block in the III uses a higher oversampling ratio and double-precision filters in some places compared to the II." source

Firmware Ares 3.02 (and later) for the Axe-Fx III:

This firmware introduced major improvements to modeling of drive pedals in the Axe-Fx III.

NOTE: These changes can result in significant changes in sound, gain and level. Tips and tricks for Drive blocks prior to firmware 3.02 may not apply anymore. Also, demos and tutorials may not represent the current tone anymore.

3.02 release notes:

"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."

Changes in 3.02:

  • Drive models based on op-amp and diode clipping topologies have been completely overhauled. This is referred to as FASPICE. This includes all types based on the Tube Screamer circuit. Parameters have been added which allow the user to select the type and quantity of diodes, for the positive and negative polarity. The models have been rematched to the original pedals. source
  • Also, the tone circuits of ALL drive types have been updated. source
  • The updated models require less CPU. This can save 1 to 2 percent per Drive block.
  • Additional models have been added.
  • A Dry Level parameter has been added.
  • The Basic page now shows the controls which the actual pedal provides. source

The changes do not apply to the drive types which are available as input boosts in the Amp block. source


About FASPICE:

"New Drive block algorithm (FASPICE) implemented and working." source
"The next firmware is getting a Drive block makeover. I've "cracked the code" on drive pedals and figured out a way to do a SPICE simulation in real time without using gobs of CPU. It's so simple I can't believe no one ever thought of it before but none of the papers even approach anything resembling the technique. This will bring "Ares" level modeling to the Drive block." source
"This algorithm applies to a particular set of circuits that incorporate diodes as a nonlinear component. SPICE modeling is particularly slow when modeling diodes due to convergence issues. However the diodes in drive pedals are used in such a way that there's a trick that can be employed to dramatically decrease the amount of CPU needed to simulate the circuit." source
"It normally takes a lot of CPU power to do a real-time simulation. The amp block uses an entire dedicated DSP. To do even a simple distortion pedal would normally require huge amounts of CPU. But I stumbled upon a simple trick that reduces it dramatically." source
(picture) "See the two diodes, D1 and D2? The type and quantity of these diodes (among other things that I can't reveal) affect the tone. D1 is the "negative" diode. It conducts when the voltage is negative. D2 is the "positive" diode. It conducts when the voltage is positive. In this schematic the diodes are listed as 1N34A but in the original Distortion+ they were actually 1N270. If you select the Plus Dist model and go to the last page in the UI you'll see the type of diode is 1N270. You can change the type and quantity which will change the distortion characteristics.

1N270 and 1N34A are Germanium diodes. They have a greater reverse saturation current (Is) and, hence, a lower forward voltage for a given current. This means they clip sooner. Silicon diodes, i.e. 1N4148, 1N916, etc. have a lower Is and a greater forward voltage. LEDs have yet a greater forward voltage (smaller Is).

This new firmware has 16 diode SPICE models that I collected from various sources that you can play with. 1N914 are often substituted for 1N4148 and vice-versa but they are slightly different so I included both. The original Tube Screamer had 1S1588 which, to my ears, are much different (better) sounding than 1N914 which are used in the newer Tube Screamers." source

Wikipeda: "SPICE ("Simulation Program with Integrated Circuit Emphasis") is a general-purpose, open-source analog electronic circuit simulator. It is a program used in integrated circuit and board-level design to check the integrity of circuit designs and to predict circuit behavior."

"Models that show the diode type/qty use the new op-amp/diode algorithms. Otherwise they use the old algorithms. ALL models have had updates to the tone circuits." source

Drive blocks and CPU usage

The Drive models take up various amounts of CPU. The numbers are listed in Yek's Guide to the Fractal Audio Drive models (PDF).

CPU usage is amplitude dependent on the Axe-Fx II, AX8 and FX8. This means that CPU usage will change when you hit the strings (even with the Drive block in bypassed state). This does not apply to the Axe-Fx III.

Drive models in firmware Ares 3.02 for the Axe-Fx III require somewhat less CPU (1-2%) than before.

Drive types as input boosts in the Amp block

Some of the Drive models are available as input boosts in the Amp block. More information ...

How the virtual controls compare to the real pedals

  • If the original pedal has a single Tone knob, use the Tone control in the model for authentic results.
  • If the original pedal has active EQ controls (Bass / Mid / Treble), use the Bass/Middle/Treble controls in the model for authentic results.
  • If the original pedal has a Volume or Level knob, it is mapped to the Level control.
  • If the original pedal has a Drive or Gain knob, it is mapped to the Drive control.
"The Tone control works the same as the modeled pedal. The Bass, Mid and Treble controls are a generic EQ that can be used in addition to the Tone control to further shape the sound." source

In firmware Ares 3.02 and later for the Axe-Fx III, 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.

Fuzz, buffers and impedance

Forum member AustinBuddy recommends to set Input Impedance to 90K in presets with a fuzz as the first block. This doesn't apply to the AX8, because the AX8 has a fixed input impedance setting.

"The Fuzz in the Axe-Fx reacts as though there is a buffer in front of it (because there is). It's a limitation inherent to all modeling products. I modeled it using a nominal source resistance. I forget what I used for the source resistance but it was probably around 100K ohms. To really simulate it you would need a controller to simulate the changing output impedance of the guitar." source
"You can simulate the effect of a guitar into a Fuzz-Face using the Input-Z feature." source
"The problem is that the signal is buffered and there is no way to model the interaction of the pickups with the circuit." source
(firmware 4.00 for the Axe-Fx III) "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."

Tips and tricks

Tighten the tone with a Drive block or Input Boost Type

A Drive block before the Amp block, with minimal Gain, will tighten the low end of dirty amp tones. It allows turning down gain in the Amp block. This works well in particular with Tube Screamer-based Drive types.

Alternatively, use a "blocking" PEQ, copying High Cut and Low Cut values from a favorite Drive type. This will apply the same coloring as the drive, without the gain and CPU usage.

The Axe-Fx III also provides Input Boost types. See above.

Turning an Amp block into a Drive

Insert a second Amp block before the main Amp block, set its Supply SAG to zero ("p.a. off") to switch off power simulation, and you have a virtual preamp pedal. Set the main Amp block to a fairly clean tone for best results. Try with these models: Euro Blue/Red/Uber, Friedman, Dizzy, 5153.

More information:

Using the Pitch Detector to add gain to single notes

Attach Pitch (internal controller) to the Drive parameter and use Slope in the modifier menu to fine-tune. This adds gain to single notes when played high on the neck. source

Parameters

Parameters table

Parameter Axe-Fx III Axe-Fx II AX8, FX8
Type yes
Basic – Drive yes
Basic – Tone yes
Basic – Mix yes
Basic – Level yes
Basic – Low Cut, Hit Cut yes
Basic – Bass, Mid, Treble yes
Expert – Clip Type yes
Expert – Clip Hardness yes
Expert – Bias yes
Expert – Slew Limit yes
Expert – Mid Frequency yes
Expert – Bit Reduce yes
Expert – Sample Rate yes
EQ yes
Input Select yes
Dry Level yes
Diode Type, Quantity yes

Mix

Unlike other effect blocks, Mix at 0% in a Drive block is not equivalent to 100% dry signal ("True Bypass").

"The models let clean through even with the mix at 100%. It depends on the diodes though as to how much clean is mixed. Our models are based on the most common versions." source
"The mix control in the Drive block controls the ratio of clean to dirty in the distortion stage. It's not the same as the standard mix control in the other effects." source

The Mix control operates prior to any tone control. This lets you mix some dry in with the distorted signal but still maintain overall tone control.

Some players like to turn down the effects’s Mix level (80% or lower) to increase transparancy and decrease buzziness.

Note that Mix is different from the Dry Level parameter in diode/opamp-based drive types (see below).

Sample Rate Deduction

Use Sample Rate Reduction to intentionally allow aliasing, for creative effects.

Bit Reduction

Use Bit Reduction to intentionally lower the resolution of the signal, for creative effects.

Slew Rate

This probably refers to how fast the circuit can swing its output. If the signal to be amplified is too fast, the circuit will not be able to perform properly, only amplifying signals below the slew rate limit. Poor slew rate results in high frequencies not passing through the amplifier, and thereby limiting or muting high harmonics.

The Pro Co RAT is known for its poor slew rate, because of the LM308 op-amp being used. Read this.

Explanation of Slew Rate in Wikipedia:

  • "In electronic musical instruments, slew circuitry or software-generated slew functions are used deliberately to provide a portamento (also called glide or lag) feature, where an initial digital value or analog control voltage is slowly transitioned to a new value over a period of time (see interpolation)."
  • Also: "Slew-induced distortion (SID or slew-rate induced distortion) is caused when an amplifier or transducer is required to change output (or displacement), i.e. slew rate, faster than it is able to do so without error. At such times any other signals may suffer considerable gain distortion, leading to intermodulation distortion. Transient intermodulation distortion may involve some degree of SID and/or distortion due to peak compression."

Explanation of Slew-induced distortion in Wikipedia:

  • "Slew-induced distortion (SID or slew-rate induced distortion) is caused when an amplifier or transducer is required to change output (or displacement), i.e. slew rate, faster than it is able to do so without error. At such times any other signals may suffer considerable gain distortion, leading to intermodulation distortion.[1] Transient intermodulation distortion may involve some degree of SID and/or distortion due to peak compression."

EQ

The 10-band Graphic EQ was added in firmware Ares 1.16 for the Axe-Fx III.

The EQ is reset when changing the Drive type.

Dry Level

Even with Mix at 100%, clean level can pass through diodes. The Dry Level parameter in diode/opamp-based drive types (in firmware Ares 3.02 and later for the Axe-Fx III) determines the amount of clean level that passes through the diodes.

Release notes Ares 3.02 for the Axe-Fx III:

"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."

Pictures of the modeled pedals

Gallery of modeled pedals, by MDProd.

Other drives and devices

Drive models

BB Pre (based on: Xotic BB preamp)

BB.png

An overdrive with a preamp stage. "BB" is an abbreviation of "Bluesbreaker".

Bender Fuzz (based on: Sola Sound/Vox Tone Bender)

TB.png

The fuzz that Jimmy Page used to record Whole Lotta Love.

Bit Crusher (custom model)

This custom model warms up a sound or deliberately degrades a signal, using bit reduction or sample rate.

Blackglass B7K (based on: Darkglass Microtubes B7K)

Analog bass preamp, famous for its overdrive and transparency.

Blues OD (based on: Marshall Bluesbreaker (Mk1)

Produces the mildly overdriven valve sound of the 2x12 Marshall combo amp as used by Eric Clapton in John Mayall’s Bluesbreakers.

Esoteric ACB (based on: Xotic AC Booster)

AC.png

Thick, light-to-medium overdrive ("Almost Clean").

Esoteric RCB (based on: Xotic RC Booster v1)

RC.png

"Real Clean" transparent boost pedal with gain and EQ controls.

Eternal Love (based on: Lovepedal Eternity)

LP.png

Clean boost, overdrive and treble booster.

FAS Boost (custom model)

A custom model, designed to boost vintage amps like a Plexi.

FAS LED-Drive (custom model)

This custom model simulates LED clipping.

FET Boost (custom model)

Gentle and smooth clipping with tone controls.

FET Preamp (custom model)

Similar to the Boss FA-1 Fet Preamp, a favorite pedal of The Edge (U2).

Face Fuzz (based on: Dallas Arbiter Fuzz Face)

FF.png

The fuzz that Jimi Hendrix used.

Fat Rat (based on: modded Pro Co Rat)

RAT.png

Fuller and smoother sound than the standard Rat (see Rat Distortion).

Full OD (based on: Fulltone Full-Drive 2)

FD.png

Thicker overdrive than a Tube Screamer.

Hard Fuzz (custom model)

Hard-clipping, 60s-style fuzz.

Heartpedal 11 (based on: Lovepedal OD11/Amp Eleven)

Tone of an overdriven tube amp.

Jam Ray (based on: Vemuram Jan Ray)

Boost/overdrive with a lot of headroom, recreating the tone of blackface Fender amps from the '60s.

M-Zone Distortion (based on: BOSS MT-2 Metal Zone)

MZ.png

Get crushing metal tones from a clean amp, love it or hate it,

Master Fuzz (based on: Gibson Maestro Fuzz-Tone FZ-1A)

MFT.png

The original fuzz, as used by Keith Richards in Satisfaction.

Micro Boost (based on: MXR Micro Amp)

Famous clean boost from the '80s.

Mid Boost (custom model)

A custom model that boosts the middle frequencies.

Octave Distortion (based on: Tycobrahe Octavia)

TO.png

Octave-up fuzz, used by Jimi Hendrix.

Pi Fuzz (based on: Electro-Harmonix Big Muff Pi Triangle)

BMP.png

The well-known saturated fuzz.

Plus Distortion (based on: MXR Distortion +)

DIST+.png

Designed to get more distortion from an already overdriven amp.

Rat Distortion (based on: Pro Co RAT)

RAT.png

The famous black box.

Ruckus Ge (based on: Suhr Riot)

Based on Suhr's modern high-gain pedal, specific voicing

Ruckus LED (based on: Suhr Riot)

Based on Suhr's modern high-gain pedal, specific voicing.

SDD Preamp (based on: preamp in Korg SDD-3000)

Preamp in Korg's rackmount SDD-3000 digital delay, used by The Edge.

Shimmer Drive (custom model)

Custom model, designed to boost models of vintage amps (Plexi, Vox).

Shred Distortion (based on: Marshall Shred Master)

MSM.png

Marshall's version of a distortion for shredders.

Super OD (based on: BOSS SD-1 Super OverDrive)

BSO.png

The competitor to the Tube Screamer.

T808 Mod (based on: modded Ibanez TS9 Tube Screamer)

TS9.png

Modded Tube Screamer: more bass, more gain, more transparency.

T808 OD (based on: Ibanez TS9 Tube Screamer)

TS9.png

TS9DX in TS9 mode.

Tape Distortion (custom model)

TDST.png

Custom model that simulates the clipping of an overdriven reel-to-reel Ampex tape deck.

Timothy 1 (based on: Timmy overdrive by Paul Cochrane)

Transparent boost/overdrive pedal (blue), with the internal switch set to symmetrical clipping.

Timothy 2 (based on: Timmy overdrive by Paul Cochrane)

Transparent boost/overdrive pedal (blue), with the internal switch set to asymmetrical clipping.

Tone of Kings (based on: King of Tone by Analog Man)

Improved and sought-after variant on Marshall's Bluesbreaker pedal.

Treble Boost (based on: treble booster circuit)

TRB.png

Silicon-based treble booster.

Tube Drv 3-knob (based on: 3-knob Tube Driver)

TD-3.png

Pedal with a 12AX7 tube inside, version with 3 knobs.

Tube Drv 4-knob (based on: 4-knob Tube Driver)

TD-4.png

Pedal with a 12AX7 tube inside, version with 4 knobs.

Zen Master (based on: Hermida/Lovepedal Zendrive)

ZEN.png

Dumble-in-a-box.