Always consult the Owners Manuals first

Chorus block

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Chorus block.PNG

Available on which Fractal Audio products

  • Axe-Fx III: 2x.
  • Axe-Fx II: 2x.
  • FX8: 2x.
  • AX8: 1x.

X/Y and channels

  • Axe-Fx III: 4 channels.
  • Axe-Fx II: yes.
  • FX8: yes.
  • AX8: yes.

Position of the Chorus block

It's a matter of personal preference where to put the Chorus block: before ("pedal") or after ("rack") the Amp block. When placed before the Amp, make sure the Chorus is set to mono (LFO Phase is 0).

Chorus voices

Selecting more than 2 voices is useful only when LFO Phase is not zero. source

Owner's Manual: "Whenever the number of voices is set to more than two, the LFO type will be changed automatically to “SINE.” If the number of voices is greater than two and the LFO type is changed to something other than “SINE,” the number of voices will be reset to two."
(Axe-Fx III) "The Chorus block has up to 8 voices." source

Parameters table

Parameter Axe-Fx III Axe-Fx II AX8, FX8
Type yes yes yes
Number of voices yes yes yes
Rate yes yes yes
Depth yes yes yes
Tempo yes yes yes
Delay Time yes yes yes
Mix yes yes yes
Low Cut, High Cut yes yes yes
LFO Phase yes yes yes
LFO Type yes yes yes
Auto Depth yes yes yes
Phase Reverse yes yes yes
Drive yes yes yes
Width yes yes yes
LFO2 Rate, Depth yes yes yes
Stereo Spread yes yes yes
Dimension Mode yes yes yes

Specific chorus types and effects

Vintage Tape

This type uses the tape delay algorithm from the Delay block. It sums the left and right block inputs into mono, so use caution as stereo cancellation may occur.

Dimension D

Based on Roland's SDD-320 Dimension D.

Original Dimension D manual.

"The Dimension Mode parameter turns on "Dimension Processing". This can be turned on in any type. However I highly recommend using the Dimension Type as it sets the correct base algorithm, LFO type, delay time, phase, etc., etc. as well as turning on the Dimension Processing. The Dimension D is really just a typical chorus. At the output, however, some special processing occurs that gives that unique sound. Turning Dimension Mode to one of the three settings engages the various aspects of that processing." source
"A Dimension D is a fairly typical chorus with some added analog processing on the outputs. The analog processing has a "normal" mode and a "boost" mode. The unit itself has four switches. These switches set the rate and the depth as well as turn on the boost mode. The switches do the following: Slow rate (0.25 Hz), low depth. Slow rate, normal depth. Fast rate (0.5 Hz), normal depth. Fast rate, normal depth, "boost" on. The depth is actually reduced in modes 3 and 4 to compensate for the higher rate. In the Axe-Fx this is done automatically when Auto Depth is on. Therefore I've indicated the depth as "normal" in modes 3 and 4 as the amount of pitch shift is roughly the same as mode 2. There is also an EQ that is present in all the modes on the dry signal. The LFO is a triangle wave and is 180 degrees out of phase between channels. The Dimension Mode parameter has three settings: Low, Medium and High. Low: Dry EQ off, boost off. Med: Dry EQ on, boost off. High: Dry EQ on, boost on. The Low setting has no equivalent on an actual Dimension D since the dry EQ is always active. The Dimension Type sets the LFO type, phase, Auto Depth, Hi Cut, etc., etc. and sets the Dimension Mode to Medium. With the appropriate settings of Rate and Depth you can duplicate modes 1, 2 & 3 on the actual Dimension D. To duplicate mode 4 you simply set the Dimension Mode to High. The Rates are given above. I've found a Depth of around 25% to be a good starting point. Increase or decrease to taste. The Type does NOT preset the Rate or Depth." source
"Dimension 1 is the same as previous firmware and is "digital". Dimension 2 (firmware 17 and later) uses the new BBD algorithm." source

BBD algorithm

This uses an algorithm which is based on the BBD algorithm from the Flanger block. All the “Analog” chorus types use this algorithm.


There's no dedicated Vibrato effect in the Axe-Fx and AX8. You can create this effect by using a 100% wet chorus.

A classic "VB" pedal vibrato effect typically uses a TRIANGLE waveform for the LFO, but the classic "CE" vibrato uses SQUARE.

(forum member Scarr) "The rumour is just the Boss VB-2 was a CE-2 without the dry signal mixed in (and pedal ramp on depth). A switch to disable the dry signal is a popular CE-2 mod."

Yek's settings for a vintage Vibrato (source):

  • Chorus type: Japan CE-2
  • Rate: 4.294
  • Tempo: none
  • LFO: Sine (try Triangle for a more spiky sound)
  • LFO Phase: 0
  • Depth: 50
  • Delay Time: 10.00
  • Voices: 2
  • Width: 0
  • Auto Depth: High
  • Phase Reverse: None
  • LFO2 Rate: 0.050
  • LFO2 Depth: 0
  • Spread: 0
  • Mix: 100
  • Low Cut: 20.00
  • High Cut: 8000
  • Drive: 3.33.



The Tri-Chorus is a very lush chorus that was very popular among studio players in the 80s and 90s. It's a very lush chorus. The original devices have been discontinued. There are a lot of replicas.

AX8, FX8 and Axe-Fx II: this sound can be approached using the Chorus and/or Quad Chorus effects, combined with Pitch Detune. Tips. More tips.

Axe-Fx III: the Chorus block provides a very authentic Tri-Chorus emulation, based on a Dytronics Songbird TSC-1380. source source source


Avoiding phase cancellation and comb filtering

Some chorus types (such as 80s and Triangle) invert the wet sound on one side. If you're collapsing the signal to mono after the Chorus block, the wet side will cancel and you'll hear no chorus at all.

More information about phase cancellation.

More information

The Chorus block is explained in the Owner's Manual.