Those of you who keep up with the various new processing items that are available commercially will recognize the Bi-Phase which is manufactured by Musitronics of Rosemont, New Jersey. This is one of the more elaborate of the hundreds of phasors which have been put on the market over the past two or three years. It features two independent phasors which can be run in series or parallel, and swept with your choice of waveforms. Despite the physical size and array of front panel controls, this unit is easy to modify so you can tap into the internal sweep oscillators or feed your own sweep signal into the phase shift line. There are even two unused holes in the rear panel of the Bi-Phase which are the perfect size for mounting the 1/4" jacks required for the interface!

Mu-tron has a voltage producing photocell pedal as an optional accessory that can be plugged into the footswitch jack (5 pin DIN type connector). It puts out 0-5 volts peak-to-peak, and it will provide higher center sweep (if the Bi-Phase's switches are so set) or more rapid LFO oscillation (see owners manual for getting these effects) as voltage is increased. The trick is to take advantage of the fact that the DIN plug on back has both a voltage send and receive terminal for that pedal, and tap off that control voltage input and wire it to a jack instead.

The reason you can't just "plug in" to that DIN jack is because both of the footswitches provided stock with the Bi-Phase must be plugged in and "on" (so the LED's are "on") for the phasor to operate. So leave the DIN jack alone, you'll still need it.

Before beginning the modification, remember that altering a unit such as this will most always void your warranty from the manufacturer. If that's OK with you, then here we go. Internal access is made by removing the 3 phillips head screws in the front lip of the case, the 4 screws on the top (front panel), and the 4 screws on the rear panel. The green wire in the DIN plug is the control voltage input for the phasor. One can verify this by experimentation if you wish to double check it. Solder a wire to this DIN jack terminal, and connect the other end to the "hot" connection on a 1/4" phone jack. Mount the phone jack in one of the available rear panel holes. This jack will be grounded by virtue of the fact that the case is already at ground. Thus, no ground wire will need to be connected to the jack unless you wish. In this case, the power supply is in a separate section, and is not far from the rear panel. A good solid grounding point can be found there.

The next step involves taking a jumper off a trace that has the LFO signal on it, and running it to the second interface jack. If you look at the front of the panel you will notice the "shape" switches that choose a sine or square wave for modulating the phase shift lines. The Bi-Phase should now be turned over, and the rear of the case should be facing you. The circuit board pads which connect to the three rocker switches are easily visible as three groups of SIX pads each. The switch pad which is in the middle of the LEFT row of three for the center set of switch pads is the specific pad which we will be using. (See drawing) Connect a wire from this point to the "hot" connection of your second 1/4" interface jack. The modification is complete.

A wild effect is to have an ADSR control the rate of Bi-Phase sweep speed. Also, try a quick attack and decay controlling the phasor's center setting. The Bi-Phase's LFO gives you a beautiful sine wave for modifying flangers, vibrato, or filter sweeps. The square wave can be used to trigger sequencers, envelope generators, trill VCOs and bunches more. I've had a blast with one of these interfaced to my PAiA system, and I bet you will too!

The first jack you installed is the Sweep Control Voltage Input. The second jack is the Internal Sweep Oscillator Output.