Function f(x) Parallax Tremolo & Phaser Pedal


Here's what Function f(x) says about the Parallax Tremolo & Phaser Pedal:

The Parallax is a modulation mashup consisting of an optical op-amp-based tremolo with an OTA-based 5-stage phaser bolted on to the front end. The tremolo can be transparently subtle or very deep, and allows for triangle and square waveshapes that can be blended together for a full spectrum of sound shaping.

The phaser front-end can be toggled on/off via a dedicated footswitch and is capable of very slow and subtle filter effects up through watery phase-shifting madness. Think of it as a flexible tremolo with a phaser riding shotgun.

Both tremolo and phaser have independent low-frequency oscillators with dedicated controls, allowing for a dizzying array of overlapping modulation tones.  We recommend trying a medium tremolo speed combined with a slow phaser speed; when the waveform peaks align, the result is really out of this world (in our opinion).

For the Circuit Nerds

We believe the overall circuit to be novel, although it is possible that somebody somewhere has made something substantially similar. We doubt it, but you never know.  However, credit is due to the old Maestro Phase Shifter, which we updated with modern components and modified for inclusion in this pedal. Our take on this classic has 5 phase stages: 4 are “swept” OTA stages with an additional “fixed” op-amp-based phase stage.

The tremolo anchor circuit is a very clean and straightforward implementation drawing from a variety of historical optical tremolo circuits and then uniquely adapted to play well with a phaser. We used a sealed vactrol (the optical element) to maximize consistency in sound from unit to unit.


  • P.Fdbk – (Phaser Feedback) This controls the amount of wet phaser signal that is fed back into the phaser’s input. More feedback = more intense phase tones.
  • P.Rate – (Phaser Rate) This controls the rate (or speed) of the phaser’s LFO.
  • T.Rate – (Tremolo Rate) This controls the rate (or speed) of the tremolo’s LFO.
  • T.Shape – (Tremolo Waveshape) This controls the waveshape of the tremolo’s LFO. Fully counterclockwise is a triangle wave, while fully clockwise is a (pseudo) square wave. In between these extremes is a mix of the two waveshapes.
  • T.Depth – (Tremolo Depth) This controls the tremolo’s LFO depth.


  • Optical Tremolo + Phaser in one box
  • Independent LFO controls for each modulation effect
  • Overall output Level control to match bypass volume level
  • Soft touch (true) bypass
  • Top mounted jacks
  • Laser-etched artwork
  • 9v DC operation (industry standard)
  • ~35mA current draw
  • Enclosure size: 4.7″ x 3.7″ x 1.4″ (12cm x 9.4cm x 3.6cm
  • Weight: 13.5 oz (385 g)
  • As with all Function f(x) pedals, the Parallax Tremolo + Phaser features a soft-touch, relay-based true bypass switching system.
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