Buchla 281 Classic Reissue Quad Function Generator

Buchla's Classic Reissue of the West Coast classic Quad Function Generator Model 281.

The reissue of the 281 module has undergone a redesign by Roman Filippov (Black Corporation) and features four function generators arranged in pairs (A-B/C-D). They can either be operated connected to produce more complex output voltages or independently.

A switch can be used to select Transient (AD envelope), Sustained (ASR envelope), and Cyclic (A-D cycle loop/LFO) modes.

When a pulse is received, the output voltage of a generator ramps up to 10V, while the speed is determined by the sum of the applied control voltage and the setting of the Attack Time control. In Sustained mode, the duration of the pulse determines the length of the sustain.

If the function generator is not in Sustained mode or the input pulse ends, the output voltage ramps down to OV. The speed depends on the sum of the decay voltage and the position of the decay control.

At the end of the decay segment a transient pulse appears, which resets the A-D cycle/LFO when in cycling mode. The attack and decay times have a control range of .001 to 10 seconds.

In quadrature mode, the function generators A-B and C-D work in pairs and are shifted in their function by 90 degrees to each other. The second function generator is triggered only after the first one has finished its attack.

The OR-combiner at the bottom of the module mixes the signals from A-B and C-D respectively and crossfades between them. This function can provide exciting results in quadrature mode, because of the time shift and and the possibility to adjust the level, more complex envelopes (similar to an ADSR) are possible.