PastFX Rotary Phaser

The PastFX Rotary Phaser is a recreation of the multi-stage Photo Coupler Maxon PH-350 Rotary Phaser by an Australian company that makes it clear from its very name what its focus is: revisiting classic pedal designs from the past.

However, the folks at PastFX rarely, if ever, resist the temptation to add extra features to these revered circuits, and that’s also the case for the Rotary Phaser, which adds an 8-stage option on top of the three ones offered by the original (4, 6 and 10 stages), and a Square LFO next to the Triangular of the vintage unit.

There’s also a red LED that visualizes the speed of the modulation rate, while the routing is faithful to the original unit with a single Input and two Outputs, with A always sending out the dry signal and B configurable via an internal switch to be either 50/50 dry/wet or 100% wet.

A peculiar feature of this pedal is that it incorporates both positive and negative feedback, which means that with the Feedback knob at 12 o’clock you get the minimum amount of feedback.

We added the PastFX Rotary Phaser to our article about the best phaser pedals.

PastFX Rotary Phaser, Builder’s Notes

PastFx Rotary Phaser is a faithful reincarnation of the revered multi-stage Photo Coupler Maxon PH-350 Rotary Phaser.

The PastFx Rotary Phaser is competitively priced and now incorporates additional features in a smaller pedalboard size format.

  • Like the original on which it is based, the feedback control can produce squeals and chirps from the runaway oscillation of the feedback. This is normal and it is advised to reduce the amplifiers volume prior to setting the feedback control to maximum CW or CCW.
  • Mode – This switch allows the user to select the number of phase stages of the effect.The PastFx Rotary Phaser has an additional 8 stage phasing option which is not found on the original.There are 4 different stage modes available indicated by number and adjacent led indicator 4,6,8,10, with 10 stage having the maximum amount of photo coupler phasing. Red LED LFO rate visually indicates the modulation rate (This is not found on the original)
  • Waveform Selector choose between Triangle or Square lfo waveform. (square wave option is not found on the original)
    The pedal has been optimised to operate off standard 9V DC Neg tip “Boss style” power only. Please avoid cheap switchmode power supplies!
  • Output B is for mono use, where the dry and modulated signals are combined. Output A will always produce a dry signal. By selecting the internal Stereo slide switch, the dry signal will be cut from the Output B jack. This will result in the Dry signal only exiting fromOutput A, and the Wet only modulated signal exiting from Output B
  • Speed – controls the modulation rate.
  • Depth – controls the Intensity of the modulation.
  • Feedback – The Rotary Phaser incorporates both positive (CW) and negative (CCW) feedback. At 12 o’clock position feedback is at its minimum.


  • True Bypass / stereo outputs (Internal Mono / Stereo Selector switch – Mono summed or Stereo Wet /Dry )
  • Current draw approx 45mA.
  • Compact 1590B Industry standard size