Modifiers and controllers

Modifiers and controllers

Some effect parameters can be modified through controllers. This means that the parameter value can be changed in real time by something called a controller. A little circle indicates that a parameter can be modified in such a way.

The Axe-Fx III, FM3 and FM9 support up to 24 modifiers per preset. The VP4 supports 16.

For example: a Wah pedal is established by assigning an expression pedal as a source in the modifier menu of the Control parameter in the Wah block.

Other examples:

• An expression pedal can act as a Whammy pedal by assigning the pedal to the Control parameter in the Pitch block.
• An external ON/OFF switch can engage or bypass an effect block by assigning it to the Bypass parameter of that block.

Modifiers are explained in depth in the Owner's Manuals.

There are different types of controllers (modifier sources):

• Internal Controllers
• External Controllers
• Manual Controllers
• Scene controllers
• Control Switches

On the Axe-Fx III, FM3 and FM9, the internal controllers are part of a block with four channels, just like a regular effect block.
On the VP4 it's also a block but without channels.

Internal controllers

Internal controllers generate or manipulate a signal in real time, without the need to use a device like a pedal or switch. It's the system that does the work, not you.

An internal controller is assigned to an effect parameter through the modifier menu, see above.

Each internal controller can be configured per preset. Some of the ambient blocks, such as the Multitap Delay block, also have specific internal controllers of their own. Like an envelope follower on the input, which allows creating swell effects.

See the Owner's Manuals for information about internal controllers.

LFO 

An LFO generates a signal as a familiar wave shape, or random signal. Each LFO generates two signals, A and B.

The "Astable" LFO type simulates an astable Op-amp Multivibrator, commonly found in effect pedals.

The "Shape" parameter controls the LFO shape for all types except Square and Random. High values approach a square wave while low values approach a triangle wave.

FRACTAL AUDIO QUOTES

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[1] You can start a sweep, ramp, etc. from a known value. When you stop the LFO it resets the function argument to zero. The output is then, for example, sin(0) = 0. The random type doesn't have a value associated with an argument of zero so it doesn't reset.

Sequencer 

The Sequencer generates a pattern by looping through 2-32 stages, similar to a synthesizer.

ADSR 

Similar to the Envelope follower, with ATTACK, DECAY, SUSTAIN and RELEASE parameters (thus ADSR).

Attack 

 The time it takes to go from silence to maximum level

Decay 

 The time it takes to drop from maximum level to the sustain level or silence

Sustain 

 The volume of a note while holding it

Release 

 The time it takes to drop from the sustain level to silence after being released

The "Type" control defaults to EXPONENTIAL. It's analog-style, where the ADSR has an exponential attack/decay. LINEAR selects a linear attack/decay.

FRACTAL AUDIO QUOTES

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[2] Set the ADSR Mode to SUSTAIN and it will sustain at the Sustain Level until the input falls below the Threshold.

Envelope Follower 

The Envelope Follower converts the input level to a signal, responding variably to playing dynamics. Play hard and the corresponding signal is loud. In comparison, the ADSR envelope generator always creates the same signal, but only triggers when you play hard enough (threshold).

Use the Envelope Follower to create an Auto Wah: attach Envelope to the Control parameter in the Wah block and hit the note hard for more effect, and soft for less effect.

Pitch detector 

The Pitch detector analyzes the pitch of your playing and puts out a low value for low notes and a high value for high notes.

Pitch blocks in the Axe-Fx III, FM9, FM3 and VP4 have dedicated pitch detectors of their own.

For more information, see these pages:

• Add gain to higher notes
• Use the sequencer to create a Slicer effect
• In Various presets & tricks Bakerman explains how to expand the use of ADSR, generate auto-wah effects and remove pick attack.

External controllers

External controllers are gateways between devices like expression pedals or external switches, and effect parameters. You rock the pedal or press the switch, and the corresponding data affects the parameter value and the sound.

External controllers are almost always used in conjunction with expression pedals and external switches, and MIDI. The Wah pedal described above is a good example.

The Axe-Fx III, FM3 and FM9 support 16 external controllers per preset. The VP4 supports 4.

Why assign use an external controller to a parameter when you can also assign a pedal or switch directly to that parameter?

Well, let's assume that you have 50 presets with a Wah, where your pedal is connected to PEDAL port 1 and assigned as such directly to the Wah's Control parameter in its modifier menu. If you need to swap that pedal to PEDAL port 2, you'd have to edit all 50 presets. Not if you had selected External Controller 1 as the source in the modifier menu. Because then you only would have had to change External Controller 1 to PEDAL 2.

Global assignments for External Controllers are set on the External Control page of the MIDI/Remote menu under SETUP.

Use a switch to turn an effect on/off

A common practice is to use an external switch to turn an effect on or off. The switch is assigned to an External Controller. And that External Controller acts as the modifier source for the effect's Bypass parameter. The side-effect is that you can no longer engage or bypass that effect manually otherwise. The On/Off state is determined by the external controller, exclusively.

What if the pedal is not connected

When a pedal is assigned to a parameter using an external controller, the system must know what to do if that pedal is not connected. That's what the INITIAL VALUE parameter is for, in SETUP > MIDI/Remote. I.e., to make sure that the signal is not muted if the pedal controlling the output volume is NOT connected, set the external controller's initial state vale to 100%. Important: Initial Value settings apply only to external controllers, not to pedals that are connected directly to the device.

MIDI

External Controllers can be controlled through MIDI. On the Axe-Fx III, FM, FM9 and VP4, the MIDI CCs are assignable in SETUP.

Manual controls

On the Axe-Fx III, FM9 and FM3, 5 manual controllers are available in the Controllers block and/or Performance Pages.

They can be used as modifier sources for real-time manipulation of parameters from the front panel, without needing external devices.

Control Switches

This applies to:

• FM3, FM9 and FC controllers
• AX8

The VP4 doesn't support Control Switches.

Instead of an internal or external controller, a virtual Control Switch (CS) can act as a modifier source. The CS itself is controlled through an onboard switch or switch on an FC controller (latching or momentary).

The Axe-Fx 3, FM3 and FM9 have 6 Control Switches (CS). The AX8 The AX8 has two Control Switches.

Groups

Control Switches can be made part of a mutually exclusive group. This means that engaging one will bypass the others.

Control Switches and Scenes

The state of a CS is stored per scene: On, Off, or Last. Last, which is the default, leaves the switch state unchanged when you change to a scene with this setting. The per scene settings can be accessed from the CS PER SCENE page in the Controllers block.

MIDI

The Control Switches also let you transmit MIDI at will by pressing the switch when using an FC-6, FC-12, FM3 or FM9. This doesn't depend on a preset change or scene change. Up to four MIDI commands (PC or CC) can be transmitted. Read MIDI for more information.

Control Switches are documented in the Owners Manuals for the FC controllers and FM3, FM9, and AX8.

Modifier parameters

The modifier operates between the data from the internal or external controller and the effect parameter. The modifier menu provides several options to manipulate the signal.

Auto-Engage

What does Auto-Engage do

The Auto-Engage modifier parameter allows engaging and bypassing effects automatically. Example: rocking an expression pedal will engage a Wah block automatically without having to press a switch first, like an optical Wah pedal.

Configure Auto-Engage

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

The Speed options engage the effect when the controller changes more than 5% in any 20 ms interval.

The Position 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.

FRACTAL AUDIO QUOTES

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[3] The on value is 5% higher than the off value. This is by design. It's called hysteresis and it's a common technique used in many "bang-bang" controllers, i.e. thermostats. This is to prevent chatter at the threshold.

Firmware 27.xx for the Axe-Fx III (and corresponding firmware for the FM3 and FM9) added activity sensing to directly connected pedals, FC pedals and external controllers. This stops Auto-Engage from engaging an effect if the pedal/controller is not connected. This prevents, for example, a Wah being engaged if Auto-Engage is on but no pedal is connected.

Forum member Bakerman:

Both auto-engage types need to go into the off zone (determined by Off Value) to disengage. Position/speed really only changes the conditions to engage the block. "Speed" type requires a certain rate of change instead of simply reaching some value.

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

Use Auto-Engage with 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 set to ON.

Alternatives to Auto-Engage

Auto-engaging an effect may cause an hickup in the audio when engaging the effect, for example when using the Pitch block to create a Whammy effect. 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 the heel-down position and switch to 100% processed sound when moving the pedal while retaining the expression pedal's regular functionality. This only works with effects where the heel-down position sounds like the unmodified direct tone and that have a Mix parameter. This rules out the Wah block.

Another alternative: use the approach shown in the DEVY TOWNSEND factory preset, where the hiccup when engaging is avoided using a Volume block.

PC RST (Program Change Reset)

This modifier 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).

For example, you have an expression pedal assigned to a Level parameter. You set the pedal halfway 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.

FRACTAL AUDIO QUOTES

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[4] […] 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

The Damping modifier parameter determines how long it takes to move the parameter between values.

Damping provides separate Attack (up) and Release (down) parameters. This means that damping up and down can be set at different times.

Options:

• Exponential damping (default: classic damping style where the modifier value has an exponential attack/decay
• Linear attack/decay

Update rate

This modifier parameter 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.

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.

Turning up the Scale will ensure that the Control value reaches maximum even if the pedal doesn't. [5]

FRACTAL AUDIO QUOTES

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Create a Whammy effect, 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

Create a Log taper in a modifier menu: set "Mid" in the modifier menu to 20%. Adjust the Slope to avoid the dead zone

Dual source modifiers

The Axe-Fx III allows two sources per modifier (dual source modifiers).

This is not supported on the FM3, FM9 and VP4.

Modifiers and channels

Current firmware for the amp modelers lets you assign a controller to a parameter and apply that either to a single channel or to all channels of the effect block in the modifier menu. This allows flexible use of a modifier, especially across scenes. Note that you can only select "single" once, meaning that you can NOT assign a separate controller to each of the four channels.

The Control block itself has 4 channels on the Axe-Fx 3, FM3 and FM9.

On the VP4, a modifier always applies to all channels of the block.

CPU usage

Using modifiers 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.

Tips, tricks and troubleshooting

Factory presets

Search the Factory presets page for controller to see examples of usage of an external and internal controllers.

See which parameters use a modifier

To see if and which controllers are used in a preset, go to the Controllers block 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.

Global blocks

Modifier settings and controller assignments are not saved with Global blocks.

Using controllers and modifiers in a DAW

Forum thread

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

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