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Modifiers and controllers

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X/Y and channels

  • Axe-Fx III: 4 channels
  • Axe-Fx II: no
  • FX8: no
  • AX8: no

On the Axe-Fx II, AX8, and FX8, when a controller is assigned to a parameter, it always applies to the X and Y settings. It's not possible to have different modifier settings per X/Y.

"The architecture doesn't allow for this. source

The Axe-Fx III lets you assign a controller to a parameter and apply that either to a single channel or to all channels. This allows more flexible use of a modifier, especially across scenes.

Also, the Axe-Fx III allows multiple controller settings within a single preset, because the Control block has 4 channels.

What are modifiers and controllers

Modifiers and controllers are explained in depth in the Owner's Manual. They allow real-time control over parameters and therefore sound.

Controllers — Generate data which can change parameter values. For example: an expression pedal (an external controller) works with the Wah block, an external on/off switch (an external controller) turns an effect on/off or taps the tempo, an envelope follower (an internal controller) makes fade-ins possible.

External controllers — Gateway between the FAS device and another external hardware device such as a pedal, switch or MIDI device.

Internal controllers — Generate data within the FAS device, which in turn change parameter values. Envelope follower, LFO and ADSR are examples of internal controllers. Use the Control menu to adjust their settings, per preset.

Modifiers — Sit between the internal or external controller and the parameter which is being "controlled". So the chain goes: internal/external controller sends data, which is modified and then results in changes in sound.

Scene controllers — Read this: Scenes.

See the Owner's Manual for an example of assigning a modifier to the Wah block.

Differences between the Axe-Fx II and Axe-Fx III

In addition the differences noted above:

  • On the Axe-Fx II, a pedal, switch etc. always has to be attached to an external controller first, to be able to act as a modifier source. The Axe-Fx III allows a pedal, switch, etc. to be directly assigned as a modifier source.
  • The Axe-Fx III allows 16 external controllers, and 24 modifiers per preset.
  • The Axe-Fx III provides Control Switches, the Axe-Fx II does not.

Internal controllers

What do internal controllers do

Internal controllers generate control data without help of an external device.

The Axe-Fx III has the same internal controllers as the II. But each internal controller can have 4 different sets of settings per preset, because the Control block has 4 channels. Also, some of the "ambient" blocks in the Axe-Fx III have their own built-in envelope followers on the input, enabling swelling effects without having to use a controller.

Read the Owner's Manual for more information about internal controllers.

ADSR, Envelope Follower, LFO, Pitch, Sequencer


5 internal controllers generate control data without help of an external device:

LFO — generates control signals as familiar wave shapes or random signals. Each LFO outputs two signals, “A” and “B”.

Sequencer — generates control patterns by looping through 2–32 stages.

ADSR — “envelope generators” with ATTACK, DECAY, SUSTAIN and RELEASE parameters (thus “ADSR”).

Envelope Follower — converts input levels to control signals, responding variably to playing dynamics. In comparison, the ADSR envelope generator always creates the same control signal, but only triggers when you play hard enough. Use Envelope to create an Auto Wah: attach Envelpe to the Control parameter in the Wah block and hit the note hard for much effect, hit it soft for less effect.

Pitch detector — analyzes the pitch of your playing and outputs a low value for low notes and a high value for high notes.

Envelope and Pitch only detect signals at the front input of the Axe-Fx II and AX8, and Input 1 left rear (Axe-Fx II). The FX8 lets you adjust this for POST-only setups (Global menu). The Axe-Fx III has expanded possibilities and its Pitch block has its own detector.

More information

Tutorial video by Simeon

You can use the sequencer to emulate a "Slicer" effect.

Bakerman explains how to expand the use of ADSR, to generate autowah effects and removing pick attack

External controllers

An external controller lets you manipulate effect parameters with a pedal, switch, dial, etc. Examples; Wah pedal, Whammy pedal, changing the rate of an effect with a rotary dial, engaging the Hold function of a Reverb with an external switch.

Engaging and bypassing an effect through an external controller

You can attach a controller to an effect's Bypass (Mode) parameter. This will not change the bypass mode but it'll act as an On/Off switch for the effect block. Side-effect is you can no longer engage or bypass that effect manually by editing the preset. The On/Off state is determined by the external controller, exclusively.

The Axe-Fx III provides separate Bypass and Bypass Mode parameters.

Setting the state of a disconnected external controller (INIT VALUE)

Setting the initial state of an external controller is important to prevent issues when that controller is not connected. For example, you are using a controller (a pedal) to control the overall volume. To make sure that the output volume is 100% when the pedal is NOT connected, set the controller's initial state to 100% (MIDI > Initial Value).

Initial Value settings apply only to external controllers, not to pedals that are directly connected to the device.

The AX8 and FX8 detect when a pedal is not connected and set the controller's initial state at 100% automatically. The Init Ctrl value will be bypassed.

(FX8) "Pedals are always running. If nothing is plugged in there is a pull-up resistor that pulls the pedal value to 100%." source

List of MIDI CCs for external controllers

  • Axe-Fx III – Assignable in Setup > MIDI/Remote > External
  • Axe-Fx II – External controllers 1-12 correspond with MIDI CCs 16 - 27
  • AX8 – External controllers 1 - 4 are assigned to Pedal 1 - 4 by default
  • FX8 – External controllers 1 and 2 are assigned to Pedal 1 resp. Pedal 2 by default

Modifier menu


What does Auto-Engage do

The Auto-Engage modifier parameter allows engaging and bypassing effects automatically. Example: rocking an expression pedal will engage and bypass the Wah block automatically, like a optical Wah pedal.

How to configure Auto-Engage

You can make Auto-Engage kick in depending the pedal's position, or the speed with which you rock it. "Position" depends on the OFF VAL setting.

"Added speed (SPD) vs. position (POS) options to Modifier Auto-Engage parameters. The SPD options engage the effect when the controller changes more than 5% in any 20 ms interval (as before). The POS options engage the effect when the controller value is 5% greater than or less than the Off Value (depending upon whether the Off Value is less than or greater than 50% respectively). For example, setting the Auto-Engage to SLOW SPD will bypass the effect when the controller value is less than, say, 5% (default). To engage the effect the controller (foot pedal) must be moved more than 5% in a 20 ms interval. This requires that the pedal be moved somewhat rapidly and prevents the effect from engaging erroneously if the pedal droops. Setting the Auto-Engage to SPD POS will bypass the effect in the same manner but the effect will engage when the controller exceeds 10% (5% + 5%) regardless of the rate of change."

To turn an expression pedal into a virtual "toe switch": set OFF VAL to around 90% and Auto-Engage to Medium or Slow.

Auto-Engage and scenes

When switching scenes while the effect is still engaged, the effect will also be engaged in the new scene. In other words, an Auto-Engaged effect survives scene switching, even with Scene Revert ON.

Auto-Engage and software editor

Auto-engaging an effect in the Axe-Fx II, AX8 and FX8 will not be visible in the editor for technical reasons. In other words, the block won't be un-bypassed visually. To see the actual state of the block, refresh the editor.

Alternative to Auto-Engage

Auto-engaging an effect can cause an hickup in the audio when engaging the effect, such as a simulated Whammy. To avoid this, use modifier settings like these instead of Auto-Engage:

  • Auto-engage = off
  • Min = 100
  • Max = 0
  • Start = 60
  • Mid = 0
  • End = 49,8
  • Slope = 100
  • Scale = 10
  • Offset = -100.

These settings pass the unmodified signal at heel-down position and switch to 100% processed sound when moving the pedal, while retaining the expression pedal's regular functionality. Note that this only works with effects where the heel-down position sounds like the unmodified direct tone and which have a Mix parameter. This rules out the Wah block. Forum discussion

PC RST (Program Change Reset)

This parameter determines whether a modified parameter will be reset to its stored value when switching presets, or stay at its current value ("survive" preset switching).

Example: you have an expression pedal assigned to a Level parameter. You set the pedal half-way and then switch presets. PC RST determines whether the new preset maintains the pedal position and sets Level accordingly, or sets Level at the stored value of the preset, regardless of the pedal's position. If it's ON, the stored value will be used, until the pedal is moved.

"The new value must be 5% different than the previous value, otherwise whatever value the pedal is at, will immediately override the "PC RST" value. The idea is that the parameter is set to a value when you recall the patch. You then have to move your pedal a bit (5%) to regain control of the parameter. This is done for two reasons:
  1. Many MIDI controllers send the state of their expression pedals along with the PC message. If the behavior weren't as described, the stored parameter value wouldn't stick.
  2. Many MIDI controllers have "noisy" expression pedals where the value tends to bounce around a little. This prevents the stored value from being lost."

Damping and Attack/Release

Damping determines how long it takes to move the parameter between values. The Axe-Fx II, AX8 and FX8 allow a maximum damping time of 1000 ms.

The Axe-Fx III replaces Damping with separate Attack (up) and Release (down) parameters. This means that damping up and down can be set at different times. Also, the maximum damping time has been expanded.

Update rate (Axe-Fx III only)

This selects the rate at which the modifier updates the target parameter. For most applications a slow rate is sufficient. That's always the case with external controllers.

Under some circumstances a slow or medium rate combined with an internal controller may cause “zipper noise”. Increasing the rate will reduce the noise. Note: higher update rates increase background CPU usage and should only be used when absolutely necessary.

Modifier curves

Read the Owner's Manual for more information and diagrams.

SCALE — Applies “gain” to the modifier curve, allowing the user to create steeper or shallower curves (vertical). Use this to optimize your pedal.

OFFSET — Allows shifting the curve up or down the Y-axis.

SLOPE — Introduces an "S"-shaped curve.

M@'s tips:

  • Simulate a Whammy, reaching an octave at toe-down, with extra "play" at the top: Pitch CONTROL; SCALE 1.089; OFFSET 10.0.
  • Make the Auto-Engage "bump" disppear (true bypass at heel-down): Pitch MIX; Start 40; Mid 100; End 55; Slope 0; Scale 10; Offset 100.
  • Make a modifier go straight from MIN to MAX at toe-down: START 0; MID 0; MAX 60; SLOPE 0; SCALE 10; OFFSET -100.
  • Simulate a Log taper in a modifier menu: set "Mid" in the modifier menu to 20%. Adjust Slope to avoid the dead zone.

Modifiers and Global Blocks

Modifier menu parameters and controller assignments are not saved with Global Blocks.

Use Recall Effect (Axe-Fx III: n/a) to copy controller and modifier settings between presets, or use the editor.

Controllers and CPU usage

Attaching controllers to parameters increases CPU usage slightly. For example, when you move a pedal which is assigned to a parameter, it'll send control data which will increase CPU usage temporarily.

List of modified parameters

To see if and which controllers are used in a preset, go to I/O > Control menu and scroll to the last tab page.

You can do the same in the software editor. Press Enter after selecting a controller on the Mods page to open its Modifier menu (except for "CONTROL" modifiers). Exit or Control will return from a modifier menu to the Mods menu.

Controllers and modifiers in a DAW

Read this.


Unable to type Min/Max modifier values in the software editor

The software editors do not allow typing values in the Min/Max fields within a modifier menu, for technical reasons. Use the mouse instead.