Buchla Model 285t Frequency Shifter

The Frequency Shifter receives and external audio at its “signal” input then shifts it with either its internal oscillator “INT” or with an external oscillator at the “ref.” input. There is a switch to choose either INT or ref. The INT oscillator frequency goes from 0 to 1kc. The resulting shifts are present at the “difference” and “sums” outputs. There are two identical outputs for each of these.

The Balanced Modulator receives an audio signal at the “signal” input. This can be thought of as the carrier while the “ref.” input receives a different audio signal (the modulator). The “ring” double output is a pure ring modulation determined by the incoming signal and ref. The bottom MODULATION section applies to the “variable” double output. The knob manually sweeps from zero (the pure incoming “signal”) through amplitude modulation ending in pure ring modulation. When this knob is set fully CW to “ring” it is the same signal as the “ring” outputs.

The 285t Frequency Shifter is an interesting module for processing audio samples or live voice input via a microphone through the 207t Mixer/Preamplifier module. The "sum" and "difference" outputs from the 285t can then be routed to the 292t Quad Lopass Gate, creating dynamic tone shaping. By further splitting the processed signals into the left and right channels, this setup allows for a rich stereophonic effect.