Product Feature

You’re Going To Need A Bigger Pedalboard...


Our celebration of the almighty Mu-tron Bi-Phase. Here you'll find a potted history and other useful information including links to resources such as schematics, user manual and settings sheets.

We may have a Bi-phase available for sale.

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In 1972 Aaron Newman and Mike Beigel set up Musitronics in a converted chicken coop in Rosemont, New Jersey to produce electronic effects.

Their first product, created by Beigel from elements of his early synthesizer design, was the groundbreaking Mu-tron III envelope filter which was famously-used and endorsed by Stevie Wonder. They sent Stevie a Mu-tron III and he contacted them to say he’d recorded a track with his Clavinet and the Mu-tron III called ‘Higher Ground’.


Spurred on by the success of the Mu-tron III and ditching an early BBD flanger idea, Musitronics moved on to phasers with the Mu-tron Phasor, which utilised opamps insteads of the more usual (at the time) FETs.

In 1974 Musitronics released the Mu-tron Bi-Phase: an enormous dual six-stage phaser ‘pedal’ including - for the first time on a phaser - rotary feedback control pots.

The design of the Bi-Phase once again bucked contemporary thinking with its somewhat outmoded lamp/photocell circuit (as employed in Shin-ei’s late sixties Univibe circuit). Beigel and Newman chose a photocell circuit for its wide dynamic range, but initially the results were too good, from an audio perspective. FET based phasers had a nonlinearity that produced pleasing results musically; the early Bi-Phase design was too clean and unexciting. This led Beigel to try inserting a feedback option into the phase shift loop thereby emphasising peaks where cancellation wasn’t occurring: a eureka moment that created the distinctive clean, yet ‘chewy’ Bi-Phase sound.


The Bi-Phase has plenty of control features, both internal and external (see the user manual for more technical info and specifications), including the ability to control the sweep using the optional Opti-Pot optical foot pedal for wah-style monster phasing. The two independent sweep generators can be used singly or coupled with a choice of sine or square waves. Compared to other phaser pedals of the era such as the MXR Phase 90 and the Electro Harmonix Small Stone – both compact one pot compact units – the Bi-Phase is a complex behemoth. Like its legendary contemporaries, it sounded fabulous and distinctive, and its place in the pantheon of great guitar pedals was assured. However, its flexibility and myriad features, combined with exceptional sonic performance, meant it was destined to be far more than just a guitar pedal, earning the Bi-Phase a place in the rarefied realm of studio classics.


The Phasor II followed on from the Bi-Phase and became Musitronics’ most popular product. It employed the same low noise photocell circuitry and was effectively half a Bi-Phase but with less control options. If you seek clean yet fulsome phasing at a lower price point (and footprint) to the Bi-Phase, the Phasor II is well worth a look.

Lee ‘Scratch’ Perry famously employed one in his Black Ark Studio, and legion dub producers have followed suit.

Place a Bi-Phase across drums or hi hats (and/or guitar/keys) and you have one of the most distinctive components of the sound of dub; pair it with a Roland RE-201 and a rudimentary mixing desk and you’re away. 


In 2015 producer Daniel Boyle reunited the 78 year-old Scratch with the Bi-Phase, highlighting the monstrously-proportioned blue phaser’s impeccable dub credentials once more.

He sent us the photos you see here from the recording of the album ‘Back On The Controls’ (scroll down for a track on YouTube).


One more... It does not get any cooler than this:

Daniel Boyle’s Bi-phase signed by Lee.

From reggae to rock:

In 1993 the Bi-Phase was the effect at the heart of The Smashing Pumpkins’ seminal “Siamese Dream” album (hear it above in “Rocket”). According to Butch Vig in the documentary “Vieuphoria“: “This is one of the secrets to our secret sound. This is the Mutron Biphase. We run everything through it – everything. It’s fabulous.”


It remains to this day an absolute studio essential and a pinnacle of audio (and aesthetic) design: as relevant and useable as ever. Far more than just a vintage character effect, the Bi-Phase continues to feature in recordings and performances across a wide range of musical genres: from pop to reggae; rock to electronica.

I’ve had one in my studio for over two decades and for me it’s one of the top three must-have phaser pedals (this from someone who ‘must have’ a great many phasers); the Opti-Pot pedal adds a satisfying extra element of effective realtime user control without sacrificing the use of a hand and is highly recommended, if you can find one. Mike Beigel is one of the great pioneers of electronic circuit design and his creations have inspired many great artists to create their seminal recordings. From Stevie Wonder to the Grateful Dead, Lee Perry to the Smashing Pumpkins, how much poorer would our musical landscape be without his wondrous and colourful chunky silver boxes?






More Than You Ever Wanted To Know About Phasors by Fred Ridder & Michael Beigel



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