The CGS737 is an unusual kind of mixer. It takes two input voltages - a base control voltage [BASE CV], and a modulating control voltage [SPREAD], and creates the sum and differences of them.

These different voltages are

1. the base voltage, offset in a positive direction by the modulating voltage, and
2. the base voltage, offset in a negative direction by the modulating voltage.

A series of equal taps between these two points results in outputs that always maintain the base control voltage at its full amplitude, mixed with a differing amount of the modulating voltage.

Some ideas on how to use this module: Feed a 1V/octave signal into the [BASE CV], and a modulation signal such as from an envelope generator, LFO, sequencer etc., into the [SPREAD] modulation input. Connect the outputs, starting with the [BASE CV] unmodulated output, and working both up and down, to a series of VCOs.

While the [SPREAD] input remains at zero, all of the VCOs will track. As the modulation voltage increases, the VCOs connected to the modulated outputs will shift in frequency away from the base, at an amount proportional to its position from the center output. For example, a small modulation voltage will de-tune the oscillators slightly, fattening the sound. A modulation CV of 5 volts will set each output 1 volt apart, setting the oscillators an octave apart.

The [ODD/EVEN] switch is used to remove the [BASE CV] "straight through" point from the voltage divider, giving an even spread of outputs (no null point) as distinct from an odd spread of outputs. Needless to say, the [BASE CV] output continues to operate as normal, but the difference between it and the taps immediately above it and below it will only be half that of the difference between any other pair of taps.

An envelope generator connected to the [SPREAD] modulation input creates an interesting effect. It can, of course, be used with audio frequency signals too, and may prove interesting when driving a cluster of wave multipliers or similar. Two audio signals fed to it can produce some interesting stereo effects.

Note: The sum and differences produced by this module are voltage differences, NOT frequency differences. It is NOT a ring modulator

Build Guide