Pi-Phase mk2 dual phase shifter (Mutron Biphase clone)

The Pi-Phase mk2 is an accurate reproduction of the original Mu-Tron Bi-Phase dual phase-shifter, but in a more compact format much more suited to pedal-boards / live use.
Note - ceased production as of January 2018. Mutron USA sell the "Biphase" which is an Pi-Phase mk2 with different cosmetics.

Prophecysound mk2 Piphase pricing 
Piphase - for sales outside Australia 599.00 AUD; ex GST currency conversion
Piphase - within Australia pricing 658.90 AUD; inc GST currency conversion
extra mods    
Phase centre control (one per each phase section) (not currently available) currency conversion
For any extra information email Mike.
Note - shipping is extra, we'll contact you with information specific to your location. Example shipping costs (all tracked and insured) are:
  • USA - AUD83.5
  • UK - AUD102.5
  • France - AUD102.5
  • Germany - AUD102.5
  • HK - AUD74.4

Power supply requirements

Current Pi-Phase mkII (manufactured after October 2016)

These Pi-Phases require 9V or 12VDC, minimum 300ma current, negative centre power supply (not included).

'Old' Pi-Phase mkII (manufactured prior to October 2016)

These Pi-Phases require an external AC power supply providing approximately 15VAC (not DC, AC!) with minimum 500ma and a 2.1mm barrel plug.

If you are unsure about the power requirements for your Pi-Phase mkII, contact us for more information.

Pi-Phase mkII dimensions - 50mm (~2") high, 188mm (7.4") wide and 122mm (4.8") deep.

Prophecysound Pi-Phase mk2 overview

The Mu-Tron Bi-Phase is a dual phase-shifter invented and marketed by Musictronics USA in the 70s. It has become well-known and well-loved for it's 'classic' warm and deep sound, as well as the flexibility of it's control and audio-processing capabilities. The Prophecysound Pi-Phase mk2 seeks to accurately reproduce the sound and control layout of the original unit. Design goals for this reproduction of the Bi-Phase were:

  1. to match, as closely as possible, the sound of the original
  2. to maintain the same or a very similar control layout
  3. to package the pedal in a size and format that would allow it to be used live
  4. to dispense with the need for a special controller pedal for switching channels on/off, or for controlling pedal sweep

The Pi-Phase mk2 is all-analog and parts-accurate to the original, as much as is possible. To our ears, and the ears of many previous customers, the Pi-Phase mk2 sounds like the real-deal. How much like it? Original Bi-Phases are pretty old, and some units suffer from parts drift, lack of maintenance, and lack of calibration; each 'well-gigged' Bi-Phase can easily sound different to the next. With the Pi-Phase mk2 we give you 'factory fresh' dual-phaser experience.

The control layout was condensed to fit the targeted pedal format, while still providing a clear and understandable way of operating the unit. The original architecture of the dual LFOs / dual phase shifters has accurately been retained. As per the original, a manual isn't really even needed to explain how the unit works, or what the possibilities are. The resultant format - a pedal 50mm (~2") high, 188mm (7.4") wide and 122mm (4.8") deep - can readily be accommodated on most pedal-boards. The Pi-Phase mk2 is powder-coated and the labels are made out of industrial-strength polycarbonate for looks that will resist the worst live gigs have to offer.

No special extra foot-switch is necessary to operate the Pi-Phase mk2; true-bypass foot-switching for each individual phase channel is built into the pedal. An expression pedal may be connected to the CV PEDAL socket at the rear of the Pi-Phase mk2; the pot in the expression pedal should be connected across the sleeve and ring terminals of a stereo cable, with the wiper connected to the tip. We recommend an expression pedal that incorporates a 10k linear pot (e.g. Boss EV-5, EV-7) for optimal performance. Alternatively, you can connect an external CV signal in the range of 0-5V for controlling the Pi-Phase mk2 from a modular synth or modulation source. Either method - expression pedal or CV - allows controlling of LFO speeds and / or manual sweep of the phase sections.

Each pedal comes with reproductions of the original unit's program cards, including a new preset of Prophecysound design, and some blank program cards to record your own settings. A printed manual, with quick-start and detailed information on the pedal, is also supplied. A PDF of this manual is available for download at the bottom of this page.

Locally made for the highest quality

This pedal is manufactured and assembled here in Adelaide, South Australia. We believe in working with people we can meet and discuss our requirements with face-to-face, and in utilising local companies to stimulate the economy. Most importantly, our local manufacturers have many years of experience, and we trust them to help us produce products that are second-to-none in terms of quality and reliability.

Special note!

Prophecysound claims no association with Mu-Tron / Musitronics / Mike Beigel or Aaron Newman. The Pi-Phase mk2 is a, if you like, fan-based tribute to the original unit, and addresses a long-standing technical challenge and curiosity.

What are people saying about the Pi-Phase mk2?

Some feedback from current users of the Pi-Phase mk2:
"I have used the pedal on about four songs off my new album and have decided to actually replay some bass parts on songs already mixed just to be able to use the effect of the MK2 instead of some other phasers I already printed to tape with. I absolutely love this pedal and will make sure I have one for the road as well for my studio. There is no longer a need to risk taking my vintage phaser on the road as this truly is the best replacement pedal for any vintage phaser pedal I have yet to hear and I have heard them all.
- Paris Toon (award-winning, billboard charting lyricist, producer and musical enigma behind the collective Mothers Favorite Child), USA
The device is very well built and looks great and sturdy... I used a T-rex phaser pedal before, which didn't sound bad, but the difference is really phenomenal. I think the Pi-Phase sound is absolutely unique, it sounds much warmer and has an almost liquid texture to it... the Pi-Phase sounds great and has an enormous scope of sonic possibilities...
- SM, Belgium
The pedal sounds really amazing. On guitars sound EQ do not need to be change, sound gets full and phasing combinations are very impressive, calibration is perfect. Square phasing are great on those, with just a little fuzz or OD it seriously rocks. On the Rhodes, this is simply pure heaven, beautiful...To me this pedal is a pure magic box....
- AP, France
I love it! Its by far the best phaser I've ever played.

What does it sound like?

Samples recorded, mixed and mastered by Mic Nix Productions (Adelaide, South Australia)
Guitar - Mike Nikou
Bass, keys - Mike Both

How do I get one?

June 2015 - Pi-Phase mk2s are available for purchase now. For more information email Mike.

Related FAQs

An expression pedal with an internal linear 10k pot is recommended, some examples of which are:

  • Dunlop DV3 volume / expression pedal
  • Boss EV5/EV7 expression pedal

Unfortunately it's not practical to stock the appropriate AC power supply for each country, and even if this was possible then shipping the power supply with the pedal would add significantly to the cost because of the extra weight. You will need to source your own power supply if you purchase either of these pedals.

We believe that the Pi-Phase mk2 is as close a reproduction of the original pedal as it's possible to achieve in the modern day. By reference to the original schematics, and with knowledge draw from ownership and use of two Bi-Phases (and a Mu-Tron Phasor II), it was possible to design a more compact version of the original. It was decided to incorporate the foot-switching directly into the pedal itself so the Pi-Phase mk2 would be usable on it's own with no need for external devices / pedal-pedal switches.
The Pi-Phase mk2, like the original, features all-analog LFOs and audio sections, and through-hole components for the critical parts (the LED and LDR coupling section). 1% tolerance metal film resistors were used instead of the original carbon types so as to reduce noise. The +/-15V internal power supply design was retained, as this is a big part of the high-headroom / clean sound.
A great deal of experimentation was done with the optical phasing section, so as to match as closely as possible the response and sound of the original pedal. Anecdotal comments from users of the Pi-phase mk2 comparing their pedal to an original Bi-Phase range from '95% of the way there' to 'identical in sound and function'. Allowing for sentimentality and considering the price and availability of the Pi-Phase mk2, this is a result we are pleased with.


Yes - in fact there are 10 trim-pots that allow various parameters to be adjusted. However, it is highly recommended that you don't go adjusting these trim-pots without guidance! Doing so without knowing what you are doing can mess with the calibration of your pedal.


The Piphase mk2 requires a 16VAC (that's AC, *not* DC!) power supply with a 2.1mm barrel plug connector. We recommend the Peavey 16.5VAC / 1100ma power supply, Peavey part number 70900660, or the current item is here.

Please be sure to use the correct AC power supply with your Piphase mk2, as connecting the incorrect power supply will damage your pedal and void your warranty!

Recommended power supplies for different regions 
region retailer link to power supply
Australia Altronics Powertran 12VAC power supply
Europe Thomann Peavey 15VAC power supply
Japan Soundhouse AC 16V 1A power supply