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Information about the FM3 may be incomplete or wrong, it's being worked on.

Phaser block

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Revision as of 12:20, 25 January 2020 by Yek (talk | contribs) (Phaser types and effects)
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Phaser block.png

Available on which products

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

Channels or X/Y switching

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

Flanger algorithm

Firmware release notes for Axe-Fx III firmware Ares 12:

  1. "The Frequency parameter on the Basic page has been replaced by a "Manual" knob. It functions similar to the Flanger’s Manual control. To manually control the phasing set Depth to zero. The sensitivity of the Manual control is inversely proportional to Depth and the Manual control is disabled when Depth is at maximum.
  2. The Depth control mixes the LFO and Manual controls. When Depth is at minimum the phase shifter frequency is controlled entirely by Manual. When Depth is at maximum the frequency is controlled solely by the LFO.
  3. There are now separate Minimum Frequency and Maximum Frequency parameters. These set the minimum and maximum frequency when the Depth is at maximum and Manual is at minimum. These are updated when the type is changed.
  4. There are four "VCR Types” (Voltage Controlled Resistor). LINEAR is a simple linear mapping of LFO voltage to frequency. EXPONENTIAL gives an exponential response which can be more "musical" because the notches will move more linearly with the logarithm of frequency. JFET simulates the response of a Junction Field Effect Transistor when used as a variable resistor (as is commonly done in phaser pedals). PHOTOCELL simulates the response of a CdS photocell.
  5. The "Exponent" parameter controls the exponent for the EXPONENTIAL type. A value of 1.0 is "ideal" and results in the notches sweeping linearly with log(frequency). Higher values cause the frequency to dwell at higher frequencies and then decrease rapidly towards the lower frequencies. Lower values cause the frequency to dwell at lower frequencies.
  6. The VCR Bias parameter controls the bias point of the virtual VCR. A value of zero biases the VCR optimally. Negative values result in the VCR entering cutoff (infinite resistance).
  7. When using the PHOTOCELL VCR Type the attack and release times of the photocell can be configured using the Photocell Attack and Photocell Release parameters. Typical photocells used in phasers have an attack time of 5 ms and a release time of 35 ms but there is a bit of variation between photocell types. Shorter release times result in a “lumpier” response.
  8. The Feedback Point parameter now allows setting the feedback to any point in the phase shifter chain. A value of ‘0’ indicates prior to the beginning of the phase shifter chain. A value of ‘1’ indicates into the first stage and so on. Both positive and negative values of feedback are allowed. When adding feedback experiment with the Mix value. Increasing the Mix can achieve rich, hybrid vibrato/phase sounds.
  9. Up to 12 phase shift stages are allowed in multiples of two stages. As the number of stages is increased more notches occur in the spectrum. Experiment with the Minimum and Maximum Frequency values to move the notches in the spectrum.
  10. Most of the models are configured for mono operation with the LFO Phase set to 0.0. This is suitable for use before an Amp block. Placing the Phaser block after the Amp and Cab blocks allows for stereo phasing. Use the LFO Phase parameter to vary the phase of the right channel LFO in relation to the left.
  11. The Barberpole algorithm has also been completely reworked yielding more convincing “infinite phasing”.
  12. NOTE: Due to the comprehensive nature of the changes any existing presets will have the Phaser block reset to default values for the selected type. This can change the sound of existing presets that use the Phaser block and those presets should be auditioned and adjusted accordingly.

Phaser types and effects

Script and Block

These types are based on the MXR Phase 90 and Phase 45, Script and Block versions.

The "Phase 45" type uses subtle two-stage phasing, while the "Phase 90" type uses more pronounced four-stage phasing.

The "Script" type has a more subdued sound with higher headroom and greater clarity. The "Block" type is more modern and relies on internal feedback to create light harmonic distortion and give the effect a more accentuated swoosh.

EVH's phaser and flanger settings


The Uni-Vibe effect is available as a special mode of the Phaser block. Engage the Vibe mode (or select one of the Vibe types).

It's based on the Fulltone Deja-Vibe. source 1, source 2

More settings (before firmware Ares 12):

Put the effect before the Amp block.

"You need it before the amp if you want the bump." source
"It's so hard to make a good UniVibe clone. You gotta get the photocells just right. If they're too slow it won't be lumpy and drippy enough. Too fast and it will thump. Use anything but a photocell and it just sounds terrible." source

Connect a pedal or switch to the Rate parameter to control speed.

More information:

Barber Pole

Like the "Shepard tone", this type creates the illusion of a never-ending upwards cycle. Works best when placed at the end of the chain.


Set the Phaser to 6 stages to emulate a Mutron Bi-Phase.

There's a specific model in firmware Ares 12 and later.

"For the double-phaser of the original, set it to 12-stage with LFO Phase at 0." source

Step Phaser

To simulate a stepped phaser, set Depth to 0, attach Frequency Start to the Sequencer, set Min and Max and adjust the Sequencer faders.

Mono or stereo Phaser

Phaser defaults to mono to prevent phase problems when used before an Amp block.

To make it stereo, change the LFO Phase setting and place it after Drive, Amp and Cab.

Thump when engaging the Phaser

Engaging some effects, like Wah or Phaser, can cause a "thump" in the sound. This may be caused by impedance switching. To solve this, change Input Impedance from "Auto" to "1M". The above doesn't apply to Fractal Audio processors with a fixed (not adjustable) input impedance. Read this: Input impedance


Parameters table

Parameter Axe-Fx III / FM3 Axe-Fx II AX8 / FX8
Type yes
Rate yes
Tempo yes
Depth yes
Feedback yes
Start Frequency yes
Phaser Mode yes
Order yes
Frequency Span yes
LFO Type yes
LFO Phase yes
LFO Quantize yes
Bulb Bias yes
Feedback Tap yes
Tone yes
LFO Reset on Bypass yes
Barberpole — Sweep Direction yes
Barberpole — Filter Q yes


"Phasers cause notches in the spectrum which can reduce the apparent volume. It depends on the frequency content. Overdriven sounds have more content and will be affected more. The Level knob allows you to compensate for this." source


Increase the Order parameter to simulate phasers such as the EHX Small Stone and Mu-tron Bi-Phase.

Feedback Tap

"There is no feedback on a Script 90." source

LFO Bypass Reset

If LFO Bypass Reset is set to anything other than Off, LFO will be reset to the selected phase whenever the block is bypassed. This allows synchronizing the sweep to the engagement of the effect.

Start Frequency

"Another fun phaser trick is to set DEPTH to 0 and assign the Frequency Start to an expression pedal." source