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 utilized opamps instead 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 emphasizing 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 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.
Input Impedance: 300k ohms minimum, unbalanced
Output Impedance: 600 ohms, unbalanced
Insertion Loss: Less than 1db
Frequency Response (Bypass): 20Hz – 20kHz ± 2db
Signal Handling Capability
Each Phasor, no feedback, 4V RMS minimum
Both Phasors (in series), 50% feedback, 2V RMS minimum
Both Phasors (in series), 100% feedback, 1V RMS minimum
Phasing Rate: Sweep Generators .1Hz-18Hz • AC Power Requirements: 115V AC, 60Hz, 15 watts
Dimensions: 13¾” w. X 10¾” d. X 4¼” h
Weight (less footswitch and foot pedal): 7¾ pounds