The PastFX Rotary Phaser is a compact phaser pedal that recreates the Maxon PH-350 Rotary Phaser, a multi-stage photo coupler phaser from Maxon's Vintage Series. PastFX describes it as "a faithful reincarnation of the revered multi-stage Photo Coupler Maxon PH-350 Rotary Phaser," built into a smaller pedalboard format with a few additions the original never had1. Where the Maxon original offered 4, 6 and 10 stage phasing, the PastFX version adds an 8 stage option, a square wave LFO setting and an LED that shows the modulation rate12.
The pedal is no longer in regular production: a November 2024 Guitar Pedal X survey of PastFX's modulation range listed the Rotary Phaser among the maker's discontinued or on-hiatus pedals, at a price of $2103.
A multi-stage phaser modeled on the Maxon PH-350
The PastFX version keeps that structure and extends it. Four stage counts are available, 4, 6, 8 and 10, selected by the Mode switch and shown by an adjacent LED indicator, with the 10 stage setting delivering the maximum amount of photo coupler phasing2. The 8 stage option is not found on the original1.
Two further additions set it apart from the Maxon unit:
- A Waveform Selector that chooses between triangle or square LFO waveforms; the square wave option is not found on the original2.
- A red LED that visually indicates the LFO rate, also not found on the original1.
PastFX credits Scruffie for assistance in the project1.
The controls
The control set follows the original PH-350's speed, depth, feedback and mode layout41, with the additions noted above.
| Control | What it does |
|---|---|
| Speed | Controls the modulation rate12 |
| Depth | Controls the intensity of the modulation2 |
| Feedback | Both positive (clockwise) and negative (counterclockwise) feedback; minimum at 12 o'clock2 |
| Mode switch | Selects the number of phase stages: 4, 6, 8 or 102 |
| Waveform Selector | Chooses triangle or square LFO waveform2 |
The feedback control deserves a note. Like the original on which it is based, it can produce squeals and chirps from the runaway oscillation of the feedback loop, which PastFX states is normal behavior for the circuit1.
Squeals and chirps from the Feedback knob at high settings are a characteristic of the circuit, not a fault. PastFX describes this as normal, matching the original Maxon PH-3501.
Stereo outputs and power
The routing is faithful to the original unit, with a single input and two outputs2. The original PH-350 worked the same way: one input jack and two output jacks (A and B) to achieve a stereo effect when used with two amps, with the phaser effect coming out of the A jack and the dry signal out of the B jack. With a single amp, the pedal sent a mix of both dry and effected signals through the A jack5.
The PastFX version adds an internal Mono/Stereo selector switch1:
- Mono (default): Output B combines the dry and modulated signals for single-amp use; Output A always produces a dry signal1.
- Stereo: The internal slide switch cuts the dry signal from Output B, so the dry signal exits only from Output A and the wet, modulated signal exits from Output B2.
Power comes from a standard 9V DC negative tip, Boss style supply only, with a current draw of approximately 45mA1. The pedal uses true bypass switching, unlike the original Maxon PH-350, whose metal footswitch was mechanical and not true bypass15.
What reviewers said
Writing for Guitar Pedal X in November 2024, Stefan Karlsson surveyed PastFX's modulation range and found the Rotary Phaser had its own character among the maker's three phasers3:
"Actually a really lovely fluttery phaser - and somewhat distinct from the two others in this range."
That same survey listed the pedal at $210 and marked it as on hiatus or discontinued3. Delicious Audio added the Rotary Phaser to its article on the best phaser pedals when covering the release in March 20232.
Where it sits in the PastFX range
Videos
Leon Todd
Tri Pedal Reviews
The Pedal Picassos
Questions
What is the PastFX Rotary Phaser based on?
It is a recreation of the Maxon PH-350 Rotary Phaser, a multi-stage photo coupler phaser from Maxon's Vintage Series. PastFX describes it as a faithful reincarnation of that circuit, adding an 8 stage mode, a square wave LFO option and an LFO rate LED that the original did not have.
Does the PastFX Rotary Phaser have stereo outputs?
Yes. It has a single input and two outputs, with an internal Mono/Stereo selector switch. In mono, Output B combines the dry and modulated signals. In stereo, the dry signal exits Output A and the wet, modulated signal exits Output B, for use with two amps.
Why does the feedback control squeal on the PastFX Rotary Phaser?
The feedback control covers both positive and negative feedback, and at high settings it can produce squeals and chirps from runaway oscillation of the feedback loop. PastFX states this is normal and behaves the same way as the original Maxon PH-350 on which the pedal is based.
What power supply does the PastFX Rotary Phaser use?
It runs on standard 9V DC with a negative tip, Boss style connector only, with a current draw of approximately 45mA. PastFX states the pedal has been optimized for this supply, so a center positive adapter is not suitable.
Is the PastFX Rotary Phaser discontinued?
As of a November 2024 Guitar Pedal X survey of PastFX's modulation range, the Rotary Phaser was listed among the maker's discontinued or on-hiatus pedals, priced at $210. It is not part of the current active lineup.
Is the PastFX Rotary Phaser true bypass?
Yes, PastFX specifies true bypass switching. This differs from the original Maxon PH-350, which used a mechanical footswitch that was not true bypass.
Sources (5)
- Rotary Phaser, pastfx.com, 2026
- New Pedal: PastFX Rotary Phaser, Delicious Audio, 2023-03-13
- Guitar Pedal X, Guitar Pedal X, 2024-11-14
- Maxon VS Effects 70's tones, 21st-century quality, Vintage Guitar Magazine, 2002-02
- Maxon PH350 Rotary Phaser, Better Guitar (republished on maxonfx.com by Godlyke, Inc.), 2004
