Always consult the Owners Manuals first

Modifiers and internal+external controllers

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Available on which Fractal Audio products

X/Y and channels

When a controller is assigned to a parameter, it always applies to the X and Y settings, and all channels (Axe-Fx III). It's not possible to have different modifier settings per X/Y or channel.

"The architecture doesn't allow for this. source

On the Axe-Fx III, it is possible to have 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.

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

ADSR, Envelope Follower, LFO, Pitch, Sequencer (internal controllers)


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

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

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.

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.

Internal controllers in the Axe-Fx III: 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.

Axe-Fx II versus Axe-Fx III

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.

Modifier parameters


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

You can make Auto-Engage operate on a change of position or speed. "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.

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-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:

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. Discussion.

Bakerman: "Damping on the mix modifier can help with that. Around 200 ms would probably be a good starting point. It will still go to 100% mix very quickly, then once it's on you can spend a half-second or so at 0-5% while mix remains at 100%." source

PC RST: resetting the parameter when switching presets

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. The PC RST setting 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 determines how long it takes to move the parameter between values. It's 1000 ms at most in the Axe-Fx II, AX8 and FX8.

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

Update Rate

This 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.

Adjusting a modifier curve

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

Useful settings, courtesy of M@:

Engaging and bypassing effects through external controllers

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.

CPU usage

Attaching controllers to parameters will increase 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 slightly.

List of MIDI CCs for external controllers

Modifiers and Global Blocks

Modifier parameters and controller assignments are not saved with Global Blocks (Axe-Fx II only).

Use Recall Effect (not on Axe-Fx III) to copy controller and modifier settings between presets, or use the editor.

Setting the state of a disconnected external controller

Setting the initial state of an external controller is important 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% (I/O > MIDI > Init Ctrl Val).

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

Monitoring which effects are being modified

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

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.

Using controllers and modifiers in a DAW

Read this.


Unable to type Min/Max modifier values in Axe-Edit (Axe-Fx II), AX8-Edit and FX8-Edit

The software editors for the Axe-Fx II, AX8 and FX8 do not allow typing values in the Min/Max fields in a modifier menu, for technical reasons.

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