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MUTRON BiPhase Clone 2


The Mutron Biphase is a legendary phasor pedal, designed by Mike Beigel along with Aaron Newman at Musitronics USA in about 1973-4..

For more infos, please visit the Musitronics official website at

The Mutron Biphase Biphase is a 1x12 stages or 2x6 stages optical phasor with 2 sweep generators ( LFOs) for square and triangle modulations. There is also a "pedal" CV input to control each phasor manualy like a filter.
The Vintage Mutron BiPhase page


Now here is the second generation of Bi-Phase clones ;)

Design notes

It is an upgraded version my first Biphase clone, more easy to reproduce with common parts available on the market ...

The main difference with vintages Bi-Phase is on led modulation drivers and LDR cells. The schematic has been optimised again on that point. Control CV of phasor is ranged (0,+5V) and 2 jack plugs provide independant inputs with attenuators. Bypass is optical too, same as in the vintage Biphase, but it is now possible to drive it like a true VCAwith a 0 to +5V CV range, to mix "phased" with "direct" signal instead of only switching On/Off. A "slow" vactrol LDR cell do the job, one per phasor ....

After a long brainstorming about "what kind of LFO?" , the solution retained is to stay glued to the vintage Bi-Phase concepts of a pair of simple independant sweep generators. Pulse and triangle modulation waveforms are available. LFO1 frequency is under CV control. Both sweep generators have Freq ( speed) and Depth potentiometers . There are 2 LFO outputs , a CV-Pedal input , all are assignable as you want. It is 100% analogic and optical !

It is possible to build it with common cheap parts and it sound good with "lo-fi" aops :-)

Here is a synoptic, of the structure of the clone ... Bypass VCA stages and PSU are not shown here. Green and Magenta arrows are CVs , blue for audio.


Electronic ...

The BiPhase Clone MKII is not a small module: to build a complete version it you need (and if my computations are exacts ) to solder 122 resistors, 17 OPAs, 22 semiconductors, 31 caps, 8 LDR cells, a handfull of pots, switches ,jacks and many other little things.... Density is rather high on the Phasor pcb ! Unless to say that , after the (successful) assembly of a complete BiPhase clone pcb you will know a little bit more of this mystic art :-)

For an obscure format reason the clone is composed of 2 pcbs. They can be used independantly.( ie: to build a dual biphase = quadriphase by stacking many phasor pcbs....). Wiring of each pcbs is very "open": it is possible to assemble an exact clone of the vintage Mutron Bi-Phase or to wire it as a deeply customised synth module with all i/o connected to jacks!

All potentiometers are soldered on pcbs and spacing studied to be compatible with Spectrol S149/249 series and Sfernice P11, or even cheaper Alps, RadioOhm, Piher carbon pots with axe of of 3.18 to 6mm. Well, i have designed a kind of "multiformat" pcb footprint fitting with many pots easy to find ... Vertical or horizontal single or multi turn trimmers can be mounted too.

Pcbs are designed to be screwed to a 5U MOTM front panel , fit with Larry Hendry's brackets and 1U rack 19" /150 . MTA connectors for +/-15V external power supply are implemented..

Here are pictures of the prototype you can hear at the end of the page. A bit ugly because of missing a front panel but work fine ! It will be mounted in a 1U 19" rack soon now . This assembly is just for trials needs and the show ! Transformer is oversized , a much smaller can be used...


Also named "phasors pcb" . It contain two 6 stages optical Phasors +2 quiet bypass VCAs ( optical again :-) . Fully independant CV controls for "phase" modulations and Bypass optical VCAs... Here are 2 ideas of wiring for this pcb, many other configurations are possible as you can imagine...

100% modular ...
Rack 19" or 1/2 modular



# MCV2-B
It contain two independant Sweep Generators ( LFOs) , the pedal controler and an optional +/-15V psu to feed the whole clone. It is here because of rack 19" assembly ...



Front Panel

An idea of front panel in 19" rack is at the top of page. Bypass control inputs can be wired many different ways . Even compatibility with vintage Bi-Phase pedal switch is possible, with the same DIN plug... So here is a design idea for a MOTM style front panel, it is a "virtual" draw... Many others wirings are possible. Clic on pictures to enlarge.

(suggestion de presentation)

Sound Samples

In samples bellow the sound source is a modular synth: VCO+VCF+VCA go inside a Biphase clone prototype fitted with TL072 and Vactrols dual cells... Phasing stages are modulated by LFO shapes ( triangle and pulse) or manualy using a CV-ADSR module in sustain mode ( act as a linear CV source between 0 and 7V ).

For this last sample a CD player is used as source and all opamps are good old 1458...
Modulations are internal sweep generators...

"Inside clones growing chambers..." (mp3-stereo)


BiPhase Clone 2 pcbs + Construction Manual
are available on order



Last update 10/2007

© Marc BAREILLE 2003,2007