Burhans Timbre

A timbre generator, a CV pattern generator or sequencer and a controllable pseudo-random noise generator, after ideas in an AES article by Ralph W. Burhans (Pseudo-Noise Timbre Generators, 1972), which describes the circuit as a kind of digital tone wheel. Six stages of shift registers: each switch takes its stage's Q, nothing (centre is off) or not-Q, and its knob sets the voltage that stage adds to OUT, so OUT is the sum of the active stages; not a six-step sequencer, as most settings make more than one stage active at once. The switches give extremely long patterns; the signal input changes and randomises them on the fly, and a gate output fed back into it makes shorter loops. Each stage has its gate output and its number lit from behind the panel. As a timbre generator the clock usually runs much higher than the signal, adding harmonics to sine waves or stepping in and out of pseudo-random noise; swapping them round is just as valid.

Key features

• CLK, SIGNAL and RST in; OUT, the sum of the active stages
• Six stages: a Q / OFF / not-Q switch, a level knob, a gate output and a number lit from behind each
• 8 HP; Nonlinearcircuits publishes no current draw, depth or assembled price (it sells the DIY PCB and panel), and ModularGrid lists none