Always consult the Owners Manuals first

Presets and blocks

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Contents


Presets.png

Number of presets

Loading a preset

On the hardware or in the editor

Note to Axe-Fx II Mark I/II owners: due to space limitations in the Mark I/II BOOTROM, firmware Quantum 5.00 and later is not backwards compatible with presets created prior to firmware version 15.08. This limitation only exists for the Mark I/II. XL and XL+ still maintain backward compatibility.

You can load factory presets and presets from other users into your device. Presets have a .syx file extension. Presets are available on the user forum, Axe-Change and from other sources. If you use Fractal-Bot, a Fractal Audio editor or a MIDI librarian such as Snoize SysEx Librarian (Mac) or MIDI-OX (Windows): make a connection between your computer and the device, load the .syx file and send it to the device.

To load an external preset file in the editor, click Import, or drag and drop a file onto the editor.

The hardware is always ready to receive presets. If you upload a preset, the preset is not yet stored but kept in a buffer. If you want to keep it, save it in a preset slot. Preset files are also kept in bank files with the .syx file extension. You can use the editor to pick individual presets from a bank file.

"There are two possible destinations for a preset: the edit buffer or a defined preset number. The destination is encoded in the data. If it's not going to the edit buffer then the preset was harvested from a hard drive somehow. When you load a preset with Axe-Edit it sets the destination bytes. However if you use a librarian then the preset may go to the edit buffer or to a defined preset location depending upon the destination bytes. You can identify the preset destination from the data. If the seventh byte is 7F then it will go into the edit buffer, otherwise it will go into preset memory. For example: F0 00 01 74 03 77 7F 00 goes to the edit buffer whereas F0 00 01 74 03 77 01 02 will go to bank B preset 2 (patch 130)." source

MIDI Program Changes

Presets are divided in banks. To select a preset through MIDI, a MIDI Bank Select message and a Program Change must be transmitted. The Owner's Manual lists which MIDI Program Changes correspond with presets on the hardware. See MIDI.

From other hardware

Axe-Edit lets you transfer presets from an Axe-Fx II Mark I/II to a XL and XL+. But not the other way around. You can share individual effects blocks between Axe-Fx II models, AX8 and FX8 through the editor's Block Library.

FracTool lets you share presets between the various Axe-Fx II models and between Axe-Fx, AX8 and FX8, converting on the fly.

Another way to store preset settings is to export them into a CSV file which lists all parameter values. The editors offer this functionality.

(Yek) "When I transferred all my presets from the original Axe-Fx II to the XL, I kept a log of changed parameter values. These are the ones you may want to check before and after transfer:
  • COMP — TYPE and SUSTAIN and MIX and AUTO
  • PEQ — FREQ TYPE (bands 1 and 5), GAIN (all bands), LEVEL
  • GEQ — 16k slider, LEVEL
  • TREMOLO — LFO PHASE and START PHASE and WIDTH and TYPE
  • MIXER — BALANCE
  • CHORUS — LFO PHASE"
Walkthrough by Yek. Another conversion issue concerns effects that support X/Y:
"Any blocks that have X/Y on the XL but not on the Mark II will not import the bypass state as that is stored differently. You need to manually adjust the bypass state after import." source

AxeFxTutorials article about sharing blocks.

Forum discussion about using the hex command to recall presets and scenes.

Default scene

Read this.

More about scenes.

Factory presets

Read this: Factory presets.

Preset shows up empty

If a preset shows up empty, it was probably created with firmware that is more recent than loaded on your hardware. Update the firmware!

Preset size

In rare cases a preset can get too large (too many bytes). This is not the same as overloading the CPU. There's no warning or checking mechanism for this. If this happens, certain values won't get stored, or revert to zero upon recall. These are rare cases, which seem to occur mostly when the user uses a VERY large number of modifiers/controllers.

"A preset in the III is four times the size of a preset in the II. One preset easily does the work of four or more." source

Preset switching speed and audio gaps

"With any device that features flexible routing you have to mute, switch then unmute. This takes time. The reason is that if you don't do this then you'll end up with sound from one of the blocks that may have moved to a different position possible causing a loud pop or other artifact. For example, if you have a simple amp->cab->delay preset then you switch to a preset that has delay->amp->cab the sound from the delay will get amplified during the switch so you have to mute everything, wait for the signals to decay, rearrange the blocks, then unmute. Products with a fixed routing can switch faster since they don't have to worry about rearranging blocks. The Axe-Fx amp modeling is also far more intricate and complex than other products and this requires muting the amp modeling for a short time to allow the bias points to settle." source
"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." source
(Axe-Fx II) "Dropout is only 20-30 ms. If you are experiencing more than that then your MIDI controller is not programmed properly." source
"Channels can be thought of as a preset for an individual block. For example, you can think of the Delay block as being a stand-alone delay pedal (or rackmount processor) with four presets. Scenes store the bypass state and channel for each block. By using scenes and channels you can use a single preset for an entire song, an entire set or even the entire show. Since the routing doesn't need to change things switch fast and smooth. When switching presets the processor has to assume the routing might have changed and therefore has to clear all the buffers, mute the audio, etc. which takes time and interrupts the audio." source

Preset-Cab bundle

A Preset-Cab bundle is a single file containing the preset and one or more user cabs. You can save a bundle in Axe-Edit or AX8-Edit and load it into Axe-Edit or AX8-Edit using the Import button.

Do not not share IRs which are protected by an EULA, license, copyright etc.

Moving and swapping a preset

You can move a preset by using Store > Swap on the hardware (not on Axe-Fx III). Or use the software editor's Preset Manager.

Deleting all presets

The Utility menus on the hardware let you delete all presets at once. Be careful!

Printing a preset or user cabs list

In the software editor, select Tools > Export as Text > Preset List.

Exporting the values of all parameters of a preset

In the software editor, select Export Preset as CSV.

When executing this command, the editor writes a file to disk that contains a list of the parameter values of every block in the current preset. It’s a CSV file which means: Comma Separated Values. That’s a basic common database format that can be read or imported by any text editor, spreadsheet and database application.

(Re)naming a preset

Axe-Fx III: covered in Section 5 of the Owner's Manual.

Axe-Fx II:

FX8 and AX8:

When renaming a preset in the software editor, make sure to press ENTER in the name field, before saving the preset.

Preset levels

Setting levels and avoiding clipping

Controls:

There are Systemwide level controls as well:

When the red “Out1 Clip” LED blinks, the signal in the digital domain is too hot (loud). Severe clipping will cause digital audio distortion (crackle) which you want to avoid. This kind of clipping is not related to amp distortion. This digital distortion doesn't occur immediately when the Clip LED light, there's still some headroom left.

Important:

You can reduce the digital signal level in any block by turning down its Level. Recommended are the Amp block's Level and Output block's Level controls. The Axe-Fx III lets you monitor block levels.

If your unit's output is clipping heavily during a gig, you don't need to adjust the preset. Just enter the Global EQ and turn down Gain to solve this temporarily. Use the OUT knob on the front panel to compensate for loss of volume.

A front panel LED meter bridge provides instant visual status for the inputs and outputs. There also are meters in the GUI. The red LEDs on the front panel come on at -1 dBFS which is different than on previous hardware.

"Brief excursions into clipping may not light the clip LED long enough to be noticeable but can be audible. There is a hard limiter prior to D/A conversion that prevents wrap-around but if your preset is too hot you can hit that limiter which will sound nasty. As a rule of thumb, a preset shouldn't clip regardless of the pickups used. If you plug in a hotter guitar and the output clips, then your amp block output level is too high."

Leveling presets (VU meters)

You probably want to match the (output) levels of all your presets. If you want to do this by ear, don't do it at low volume level and don't use headphones. The reason: you may think that your high-gain preset needs to be turned down compared to your clean preset. But when playing live, that high-gain preset is compressed (has no peaks) while the clean is tone is very dynamic. Really, the only proved way to match levels by ear is to do this at gig level, and preferable with the band playing or using a backing track.

Another approach: measure and match preset levels using the VU meters. These show the relative loudness of the preset. To vied the VU meters:

Axe-Fx III: zoom out from the layout grid.

Axe-Fx II: Utility menu.

AX8: page to the right.

These readouts can be used to help set preset levels to the same apparent volume. For convenience the level of the Amp blocks can be set from this page.

"ITU-R is a standard for loudness measurement. Broadcasters use it to monitor the apparent loudness of program material and comply with regulations, i.e. making sure commercials aren't louder than the programming. The measurement includes a simple head model and hearing perception model to give a fairly accurate indication of relative volume." source Be aware that the VU meter is offset by 20 dB, so when the meter reads 0 it’s actually -20 dB. This means that the "0" mark does not indicate clipping. This allows for sufficient headroom. When playing you'll see the meters bounce around. The meters give you a general idea of the loudness of the current preset, to get you in the ballpark. Try strumming the strings in a consistent way. Adjust the Amp level(s), aiming for an average level around 0 dB."

A third method:

  1. Select a preset with a really clean amp. Why? As Jay Mitchell explains: "Clean presets have the greatest crest factor (ratio of peak to average energy) and will therefore cause digital clipping at lower average levels (which determine your perception of volume) than gainier presets. For that reason, it is important to reference the levels of all other presets to that of the cleanest one set so that it never causes the (device) to clip with the Level control set to maximum. Once you have set this level you then need to set other presets to match it. Otherwise, your cleaner presets will either clip or be much softer than the others."
  2. Disable all effect blocks (especially compressors) except Amp and Cabinet.
  3. If you use a boost in the preset, enable it.
  4. Select your loudest pickup and hit the strings hard.
  5. Turn down Amp Level until the clip LED doesn't light anymore.
  6. Turn the level down another 8 dB. This creates sufficient headroom for unforeseen circumstances.
  7. This is now your reference level for all presets.
  8. If this method causes volume loss, compensate by turning up the overall volume level on the front panel or on your amplifier.

Section 7 of the Axe-Fx III Owner's Manual discusses setting preset levels.

Use VOL INC and VOL DEC to adjust and store the preset level while playing

Volume Inc(rement) and Volume Dec(rement) present a convenient way to adjust preset levels on the fly (without manual editing). These commands let you adjust the preset level in small steps while playing. Adjustments are saved automatically.

To make this work, assign these commands to switches on your foot controller, using their MIDI CCs. The MFC-101 has dedicated commands for this purpose.

Notes:

Note that other unsaved changes to the preset will get saved too, when VOL INC or VOL DEC is triggered.

Boosting the output level temporarily

Methods to boost the signal level, i.e. for leads:

Preset guidelines

Here's a checklist to verify your presets' consistency:

Iii grid.jpg

Effects list

Read this: Effects list.

The Axe-Fx II and III Owners Manuals also contain a block inventory with short descriptions.

Block levels

Block meters on the Axe-Fx III

The Axe-Fx III features meters which display the level of each effect block.

Iii grid meters.jpg

Global/Effects Mix and Global Reverb Mix

The Effects Mix parameter in the Global menu lets you control the overall wetness of effect blocks that have a Global Mix parameter. There's a separate global parameter for reverb: Reverb Mix. Note that Reverb is also affected by the Effects Mix parameter.

The global parameters simply multiply the mix value in the presets.

"Global Reverb and Effects Mix are relative. If set to 0% the mix is set by the preset. If set to, say, -10% the mix would be 10% less than the preset mix.” source

Note that adjusting this control may not have the desired effect when the Reverb block is placed in a parallel row with its Mix parameter set to 100%.

Routing

Entering and leaving the grid

Series and parallel routing

You can put effect blocks in series (in a single row) or parallel.

Axe-Fx III: extensive routing possibilities, using the 6x14 grid.

Axe-Fx II and AX8: extensive routing possibilities, using the 4x12 grid.

FX8: a single row and the possibility to place an effect in parallel with another effect. You can adjust the placement of effect blocks in the preset configuration (Config page). Examples are provided in the FX8 manual. The first PRE and first POST effect are always series.

Parallel routing is a common method in traditional analog rigs to avoid loss of tone. However, there's no need to use parallel routing to prevent loss of tone quality when using Fractal Audio gear. Parallel routing makes it possibe to have, i.e., independent delay and reverb paths. Or you can use it to put effects after a specific effect only, not affecting the main signal. Also, on the Axe-Fx II, III and AX8 it allows you to put more effects in a preset, overcoming the limit of columns.

You don’t want to place "100% wet” effects in a parallel path, such as Tremolo or Compressor, because dry signal will still be going through the main path and affect the effect.

More information: discussion, discussion, discussion.

When running an effect in series, using its Mix parameter (if available) may affect the level of the dry level too. This is not the case with effects in a parallel row, when Mix is set to 100% (fully "wet") and using Level or Input Gain to dial in the desired effects level. So: when using effects in parallel, always set Mix at 100%, and use Level to dial in the desired amount of effect. With effects featuring an Input Gain parameter, keep Level at 0 dB and use Input Gain to dial in the desired amount of effect. Also, setting Mix at 100% avoids creating "double" direct signal paths, which result in undesirable increase of volume.

If an effect is placed in parallel, bypassing that effect may pass "direct" signal, which, when merged with the main signal, may increase the overall signal level. To prevent this, select a suitable Bypass Mode: Mute Out or Mute In. Do not use Mix 0% / Thru Mute FX In / Mute FX Out.

The FX8 automates all this, using "smart" controls. Mix, Level and Bypass are automatically adjusted when moving an effect from series to parallel, and vice versa.

Bakerman: "Decibels use a logarithmic scale. You need to double the voltage (paths of identical signal) to see a ~6 dB increase. 1 to 2 is doubling. 2 to 4 is doubling. 2 to 3 (voltage gain of 1.5) is only a ~3.5 dB increase." source
"Don't think in terms of dB. Assume you are putting 1V in (for convenience). If you add two rows you get 2V out. That's a 6 dB increase. If you add three rows you get 3V out. That's a 9.5 dB increase. If you add four rows you get 4V. That's 12 dB." source

More information.

GM Arts: "Here's a bit of trivia to cover the comments we often see along the lines of: when I combine two blocks in parallel into a single block, it gets louder... The two signals sum, so it's necessary to reduce the output levels of the two blocks so they combine without volume boost. For an equal mix, each block must be set to -6dB. What's not so apparent is what levels to use for unequal mixes, so here they are. This applies to combining two blocks that each have the same level into a single block without volume change." source -6dB    -6dB
-5.5dB  -6.6dB
-5dB    -7.2dB
-4.5dB  -7.9dB
-4dB    -8.7dB
-3.5dB  -9.6dB
-3dB    -10.7dB
-2.5dB  -12dB
-2dB    -13.7dB
-1.5dB  -16dB
-1dB    -19.3dB
-0.5dB  -25dB

Scott Peterson shows how to build a parallel path.

Leon Todd's tutorial.

PRE and POST routing

Owner's manuals:

"Sonically speaking, the main reason to care about PRE vs. POST is that a given effect will sound different when placed BEFORE or AFTER your amp’s preamp—the place where distortion occurs. How does this difference sound? If you’ve ever switched the sequence of traditional DRIVE and WAH pedals, you’ve heard an excellent example. In the case of wah before overdrive, the resonant filter of the wah “excites” the overdrive in a cool way while still retaining a natural overall tone. When the wah follows distortion, you might hear a more dramatic filtered sweep—with heavy distortion it can get almost synth-like—which might be considered less “classic.” It’s not surprising then that Wah would traditionally be a run as a “PRE” effect between guitar and amp. The amp’s distortion follows the wah effect. Many other effects fall in this same category. A different example is found in overdrive with reverb and delay. In the natural world, reverb and echo occur because of open spaces around your guitar amp – like a club or concert hall. These effects would therefore NOT be heard before a distorted amp, but after it. Recording studios often add these kinds of effects at the console—after the mic has picked up the distorted sound from the guitar amp. If you wanted to simulate this natural sounding reverb or delay these effects would likely be run “POST.” This is not to say that delay or reverb before distortion is a “no-no.” Many “legendary” tones came from echo units in front of an amp—but this effect is very different from “POST” delay—not only tonally, but also in terms of dynamics. The good news is that the FX8 allows you to experiment easily and find what combinations of pre- and post-effects work best for you. Creativity begins where tradition ends."

PRE and POST routing in the FX8

Read the manual. It has diagrams. There are 3 supported ways:

PRE and POST chains depend on the way the FX8 is connected and is configured on the preset's CFG page. The PRE/POST effects configuration per preset is indicated at the top of the screen.

"The paradigm for the FX-8 is that if you put the typical effects in the "Post" section then the level out of the Post section is the same as the level in. Therefore your effects loop is running at unity gain and the volume won't change if you bypass all the effects." source

Effects before or after the Cab block

Read this: Cab block and IRs.

More routing tools

Mono and stereo signal

Read this: Mono and stereo.

Edit parameters

Resetting an effect block

Axe-Fx III: press the Reset soft button. This resets the current channel only.

Axe-Fx II: click BYPASS twice (not EFF.BYPASS) or press-and-hold it.

FX8: click ENTER twice.

AX8: click SHIFT, then press EDIT twice.

Or use the software editor to initialize the block.

More information about defaulting the parameters in an Amp block.

Recall Effect

"Recall Effect" lets you copy the parameters of an effect block from another preset into the current preset. The Axe-Fx II, FX8 and AX8. have this feature, the Axe-Fx III does not.

Axe-Fx II: on the Recall screen, press PAGE RIGHT to get to the Recall Effect page.

AX8/FX8: set one of your function switches to SINGLE PRESET/BANK, press the switch, press PAGE.

Follow the instructions in the manual to load a preset. Once the "RECALL" page is visible, press the <PAGE> button. This will take you to the "EFFECT" screen. From here you can load any effect block to your current preset from any other preset on the unit

Recalling an effect:

If the recalled block settings don't match the ones in the block from which they were copied (source preset), there's an issue with the preset version. To solve this, save the source preset (this will update it to the latest specs), then perform the recall operation again.

To recall internal controller values only, such as Envelope or LFO, scroll to Control when using Recall Effect (not on Axe-Fx III).

Using Global blocks on the Axe-Fx II is another way to use parameter values in multiple presets. Global Blocks do not include modifier settings.

Changing a parameter in multiple presets

Bypass Mode

Owner's manual:

The settings are explained through diagrams in the Owner's Manual:

Bypass modes.png

(Axe-Fx II) "A bypassed block does nothing more than copy the input to the output. Any perceived changes in sound are just that, perceived." source

The Bypass Mode parameter on the Axe-Fx II, AX8 and FX8 can be attached to a controller. The controller will then control the block's state: engaged or bypassed. You can also use the I/O menu to switch the effect through the corresponding INIT VALUE parameter. The Axe-Fx III provides a dedicated Bypass parameter for this purpose.

The engaged/bypass state of an effect block can be different per scene (when not connected to a controller). See Scenes.

When putting blocks in parallel rows, it's important to set Mix, Level and Bypass correctly. The FX8 features "smart" Level, Mix and Bypass controls. These are automatically adjusted when moving an effect from series to parallel or vice versa.

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.

Bypassing a block does NOT lower CPU usage. CPU usage only decreases when removing the block from the grid.

Mix

The Mix parameter determines the amount of "wet" signal in a block. At "100" the signal is totally wet. This is usually used with effects such as Tremolo and Compressor. At "0" the signal stays completely dry (no effect), with the exception of the Drive block.

Mix at 50% results in both wet and dry being at -6 db in comparison to their maximum output levels (except Delay because of the "Delay Mix Law"). Compensate by adjusting Level.

(M@) "When turning up Mix in a block, the dry signal decreases. The table below shows wet/dry dB levels at various settings for blocks like Reverb, Pitch, etc. which do NOT use a constant power algorithm (like DRIVE). The Delay also uses a different method. In a rig where unity gain matters, these numbers are used to know how much to adjust Level for a given Mix setting."

MIX SETTING / WET LEVEL / DRY LEVEL / WET/DRY DIFF
0 / -∞ / 0.00 / -∞
5 / -26.02 / -0.45 / 25.58
10 / -20.00 / -0.92 / 19.08
15 / -16.48 / -1.41 / 15.07
20 / -13.98 / -1.94 / 12.04
25 / -12.04 / -2.50 / 9.54
30 / -10.46 / -3.10 / 7.36
35 / -9.12 / -3.74 / 5.38
40 / -7.96 / -4.44 / 3.52
45 / -6.94 / -5.19 / 1.74
50 / -6.02 / -6.02 / 0.00
55 / -5.19 / -6.94 / 1.74
60 / -4.44 / -7.96 / 3.52
65 / -3.74 / -9.12 / 5.38
70 / -3.10 / -10.46 / 7.36
75 / -2.50 / -12.04 / 9.54
80 / -1.94 / -13.98 / 12.04
85 / -1.41 / -16.48 / 15.07
90 / -0.92 / -20.00 / 9.08
95 / -0.45 / -26.02 / 25.58
100 / 0.00 / -∞ / ∞

The formula for an exact calculator is:

Channels and X/Y switching

Controllers and modifiers

Read this: Modifiers and internal+external controllers.

List of controllable effect parameters in the AX8.

Spillover

Read this: Spillover.

CPU load

About CPU usage

A preset uses CPU (CPU is used here as a synonym to DSP). The amount depends on the number of blocks, effect settings, controllers, overhead and more. You can check the current CPU usage percentage on the hardware and in the software editor.

Due to the power of the different processors in the hardware, the Axe-Fx II has more CPU available in presets than the AX8 and FX8. The Axe-Fx III has much more CPU available than the Axe-Fx II.

Important: bypassing a block on the grid does NOT lower CPU usage.

Explanation why there is a CPU limit.

Even an empty preset requires CPU power, depending on things such as the input noise gate settings and overhead.

“CPU usage number represents the amount of CPU dedicated to audio processing in real-time. We chose to display the actual limitation, rather than scale the number.” source

CPU usage is also covered in the Owners Manuals.

When playing through the Axe-Fx II, AX8 and FX8, CPU usage goes up and down. This is not the case with the Axe-Fx III.

"Also on II the CPU usage increases when you play whereas on the III it more or less stays constant." source

What happens when the CPU limit is approached

At about 90% on the AX8, FX8, Axe-Fx II and III, you'll approach the CPU limit of your processor. You may notice the GUI becoming slow at that point. That's because the audio signal always gets priority, above the GUI refresh rate.

When the presets requires too much CPU, audio starts too crackle and a warning message may appear. The GUI may prevent you from adding blocks at this point.

“The audio processing is the highest priority thread. When there is time left the GUI thread is run. If CPU usage is high there simply isn't enough time to run the GUI at the normal refresh rate so the thread reduces the refresh rate.”
“The CPU simply monitors the time between frame interrupts and if it predicts it doesn't have enough cycles left to process the next effect in the grid it aborts and flashes a warning." source
"Audio processing is the highest priority. Once you exceed 90% that remaining CPU is divided up between the display, expression pedals, MIDI, etc., etc. Something has to give." source
"The audio will always switch quickly. The display may take a while to switch since the audio processing takes priority. If CPU usage is high the display will take a little while to update." source
"The LCD is low priority. If CPU usage is high then the screen refresh rate drops because priority is given to the audio threads." source

More information by AxeFxTutorials.

CPU usage on FX8 and AX8

The AX8 and FX8 allow you to put blocks into the grid that will push utilization above 88% (when not playing). When taking overhead into account, the real CPU ceiling is 90% (sustained).

When CPU usage gets above 90%, the FX8 and AX8 will automatically disable blocks. The firmware will look for effects which are the biggest offenders, starting with the last edited one. If disabling the last edited one does not reduce the load enough, big offenders are next. Usually the Reverb block (especially when set to High Quality) is the first to go. Switching Reverb to Normal Quality may help to regain CPU power.

When an effect is automatically disabled, audio passes through as if it were a shunt. If it’s a block that is placed in a parallel row, this can cause a signal level issue.

Note about the Pitch block: the Pitch block in the AX8 and FX8 is very sensitive to CPU load, far before the CPU limit is reached. So try to keep CPU usage low (below 60 - 70%) when using pitch effects.

Tip: when building presets, always add the most CPU-hungry effects first.

"If I am reading these posts correctly, it sounds as though folks seem to think that an effects CPU usage is a static thing. That is, if I use a compressor in my preset it uses X% of the CPU. This is not actually how it works. CPU usage fluctuates as you use the device. That is, depending on what an effect is doing, or how it is configured, the CPU usage will vary dynamically. The AX8 monitors and manages the CPU usage. This is done for two reasons: (1) If CPU load gets too high, then the audio is effected (2) If CPU load gets too high, the front panel (footswitches primarily) is adversely effected. The performance of preset, scenes, effect bypass, etc. starts to become effected. A lot of development time has been put into reducing these effects, but it is impossible to eliminate them entirely. Rather than just allow the AX8 to behave in an undesirable fashion, the unit manages the CPU load by disabling effects. The biggest offenders are disabled first in an effort to reduce the number of disabled effects. This typically means the REVERB block is the first effect disabled. The trick is to build your presets in a manner in which this does not happen when you are playing live. In other words, test your presets out and give yourself some head room for last minute changes whenever possible." source
"Lots of different parameters, controllers, etc. can cause variation in your CPU utilization. Also, playing your guitar will bump your CPU as well. So, if you are looking at the utilization while your input is quiet, then you should plan on a 2% - 3% increase when you start playing. The cutoff for CPU is 90%. This cutoff prevents audio glitches, and provides enough CPU for low priority activities." source

CPU usage increases with USB (Axe-Fx III: n/a)

Connecting via USB will increase CPU utilization. This is by design. If a preset uses much CPU, you may run into CPU overload problems when connecting the hardware to a computer through USB. source and source

This does not apply to the Axe-Fx III because USB is handled by a dedicated USB processor.

"There's a bunch of stuff running behind the scenes. The control block is always running, the pitch detector for the pitch blocks is always running, the display is being updated, etc." source

CPU usage per block and effect type

CPU usage chart (AX8), by RoxXxtar.

How to decrease CPU usage

Waveforms

Waveform.png

Look up the explanation of waveforms and graphs in the Owner's Manual and Wikipedia.

Crossfading sounds

There are several ways to accomplish this.

Use the Multiplexer in the Axe-Fx III.

Use the Sequencer internal controller. (source: Bakerman):

  1. Set it to something like 16 steps, Rate just over 1 Hz, Values increasing in steps of 10% and have it sit at 100% for the last 6 steps.
  2. Place a volume block in each signal chain and assign Seq to turn chain B up and chain A down.
  3. Use several hundreds of milliseconds of damping.
  4. Assign one switch to Sequencer Run control and a second switch to bypass both volume blocks. You'll want them engaged before/during the crossfade.
  5. Use Mute Bypass mode for the Vol block in chain A, Thru Bypass mode for the one in chain B.

Now you can be playing sound A, hit switch 1 and get the 8-9 second crossfade, then hit switch 2 within the next 4-5 seconds before the sequencer restarts. If you wait too long you'll hear it fade back quickly to A (then B gradually again) but whenever you hit it you'll hear sound B regardless of what the sequencer's doing. After that you can always stop the sequencer and switch back to sound A; it will just be instant instead of a crossfade.

Use Scene controllers. Use a damping value of several hundreds of milliseconds.

Use a pedal to crossfade between two AMP blocks:

  1. Assign the Level parameter of one AMP block to an external controller.
  2. Do the same with the other AMP block, using the opposite curve (or reversed Min/Max values) and using the same external controller.
  3. Assign the external controller to a pedal.

More tips about crossfading.

Comparing sounds

Troubleshooting

No sound

Help, I have no sound.

Corrupt preset at startup

A corrupt preset can cause startups problems. To circumvent this:

Axe-Fx III: hold HOME on startup. The Axe-Fx III will boot with an empty initialized preset in location 000.

Axe-Fx II: press and hold RECALL on startup.

AX8/FX8: press ENTER when the splash screen is displayed.

Then delete the preset using the editor.

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