Chorus block

Available on which products

• Axe-Fx III: 2 blocks
• FM3: 2 blocks
• FM9: 2 blocks
• Axe-Fx II: 2 blocks
• FX8: 2 blocks
• AX8: 1 block

Channels or X/Y

• Axe-Fx III and FM3 and FM9: 4 channels
• Axe-Fx II: X/Y
• FX8: X/Y
• AX8: X/Y

About the Chorus block

Chorus is created by duplicating the signal and then modulating the pitch of that signal slightly. Slightly delaying the wet signal emphasizes the effect.

A flanger with zero feedback is very similar to a chorus.

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[1] Use the Chorus, which is the same thing as a flanger whose feedback is set to 0.

Chorus block diagram

Chorus types and effects

Types

1. Digital Mono
2. Digital Stereo
3. Analog Mono
4. Analog Stereo
5. Japan CE-2
6. Warm Stereo
7. 80's Style
8. Triangle Chorus
9. 8-Voice Stereo
10. Vintage Tape
11. Dimension 1
12. Dimension 2
13. Dimension 3
14. 4-Voice Analog
15. 8-Voice Analog
16. Stereo Tri-Chorus
17. Dual Chorus
18. Tape Chorus (added in firmware 23)

Boss CE-1

The Boss CE-1 is the pedal equivalent of the chorus in the Roland JC-120 amplifier.

See these for more information:

• Recreate the Boss CE-1 sound using a LFO-driven Flanger block
• Leon Todd dials in the CE-1 sound, based on the 'Japan CE-2' type in the Chorus block, and YouTube demo
• That Pedal Show: Dan's Broken Ensemble
• Admin M@'s CE-1
• The factory preset CE-1 CHORUS/VIBE also recreates the chorus and vibrato sounds of the CE-1.

Boss CE-2

This is the successor of the large grey CE-1. It was released in 1979, in the familiar Boss enclosure. It's a mono chorus.

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.

Triangle Chorus

Two voices with a triangle-shaped LFO.

Dimension D

Based on Roland's SDD-320 Dimension D. Original manual

The Chorus block provides three Dimension types: Dimension 1, 2 and 3. These correspond to the modes on the original device.

The Dimension C pedal was created by Boss to produce the Dimension D effect through a pedal. In 2018 Boss released its DC-2W Dimension C pedal, an update which is part of the Waza Craft Series. Video

According to Guitar World, SRV used the Dimension D to add thicken his solos and still keep the tone natural.

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[2] 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.

[3] 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:

1. Slow rate (0.25 Hz) and low depth.
2. Slow rate and normal depth.
3. Fast rate (0.5 Hz) and normal depth.
4. Fast rate and normal depth and "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.

Fractal Audio Blocks Guide about the Dimension Mode parameter:

• OFF: Dimension mode is not active.
• LOW: A neutral version with no tonal coloration.
• MED: Classic Dimension processing buttons 1-3. Set Rate to 0.25 - 0.50 Hz and Depth to taste.
• HIGH: Classic Dimension processing button 4. Rate and Depth as above.

For preset examples, search the Factory presets page for "dimension".

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, as well as the "Dimension 2" type: Analog Mono, Analog Stereo, Dimension 2, Dimension (and probably Japan CE-2).

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[4] Those types use “analog” delay lines. The delay lines are virtual bucket brigade devices with the delay time controlled by a virtual oscillator. That behavior is consistent with how they would work in the real world.

Vibrato

There's no dedicated Vibrato effect block or type.

You can create this effect by using a 100% wet Chorus (no dry signal). Select the Digital Mono chorus type. Keep everything at default, except: (source: Admin M@)

• Rate: as desired
• Depth: 50%
• Delay Time: 0.10
• Auto Depth: High
• Mix: 100
• Level: -6
• Stereo Spread: 0

Roland uses a Sine wave for its Vibrato effect. [5]

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[6] Vibrato is chorus with the mix at 100%. If you want vibrato on the delay trails only simply use the built-in LFO's in the delay block itself.

Mix at 100% is not an absolute requirement. As documented in Presenting the Boss CE-1..., the Vibrato mode of the venerable Boss CE-1 depends on a variable Mix setting.

See Wikipedia's Vibrato unit page for more information.

Tri-Chorus

The Tri-Chorus is a very lush chorus that was very popular among studio players in the 80s and 90s. The original devices have been discontinued, but there are a few replicas. It uses 3 different LFOs with phase relationships 120 degrees apart (less warble, more smooth and shimmery).

AX8, FX8 and Axe-Fx II 

Use the Chorus and/or Quad Chorus for the Axe-Fx II only effects, combined with Pitch Detune.

See "Another Tri-Chorus thread" in the forum for more information.

Axe-Fx III and FM3 and FM9 

The Chorus block has an authentic Tri-Chorus algorithm, based on a Dytronics Songbird TSC-1380.

See the forum's "Which tri chorus was used for modeling? as its not clear" for more information.

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[7] It's just chorus. You can't do it with the II. It's a unique algorithm and there's no way to adjust the chorus block to get the same results. The III has a separate tri-chorus algorithm.

Videos:

• Dytronics Tri Stereo Chorus
• Pete Thorn demos the Fulltone TERC
• Demonstration by Camilo Velandia

Dual Chorus

This type has independent LFOs for the left and right delay lines. The delay lines are BBD emulations.

Not available on the Axe-Fx II, AX8 and FX8.

Using other blocks to create a chorus

The Multitap Delay block in firmware Ares and later can create lush multi-voice chorus effects.

In firmware 17.01 several types were added, based on the TC 1210 Stereo Chorus/Flanger, Yamaha UD-Stump etc.

The Pitch block and Plex Delay block also can create a multi-voice detuning effect.

Leon Todd replicated the Intellifex Style 8 Voice Chorus using the Multitap Delay.

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[8] Just use the flanger with zero feedback and modulate MANUAL. In some cases, the Flanger is now a better chorus than the chorus!

[9] Use the Chorus, which is the same thing as a flanger whose feedback is set to 0.

Arion chorus

You can recreate the Arion SCH-1 chorus sound with the Flanger.

See Marco Fanton's "How to create the famous ARION STEREO CHORUS" video for information too.

Position of the Chorus block on the grid

You can put the Chorus block either before (PRE) or after (POST) the Amp block.

PRE — The block operates as a pedal on a traditional pedalboard

POST — The block takes the role of a studio/rack effect

Mono or stereo chorus

A stereo Chorus block before the Amp block will be summed to mono, so make sure it is set to mono (LFO Phase: 0) to prevent phase cancellation issues.

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 completely cancel and you'll hear no chorus at all.

For more information read Phase cancellation.

Parameters

Voices

Blocks Guide:

Whenever the number of voices is set to more than two, the LFO type will change 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.

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[10] The Chorus block has up to 8 voices.

A single chorus voice, i.e. for a Vibrato effect, can be obtained by setting LFO Phase to 0.

LFO Type

From the Blocks Guide:

Whenever the number of voices is set to more than two, the LFO type will change 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.

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Roland uses a Triangle wave LFO for its Chorus effect, and a Sine wave LFO for its Vibrato effect. [11]

Stereo Spread

Values beyond +/-100% increase the apparent image beyond the stereo field.

Chorus vs Detune

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[12] Chorus is a varying pitch shift. The pitch slowly changes between flat and sharp. Detune is a constant pitch shift.

Tips, tricks and troubleshooting

Factory presets

The Chorus block is showcased in many factory presets. Search the Factory presets page for "chorus".

More information about chorus

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

Also see:

• Wikipedia: Chorus
• Premier Guitar: Behind the Bucket Brigade
• About waveforms in Chorus