100m-ish VCO Driver

Keyboard CV Processor

The VCO driver allows modulation, glide and octave switching to be easily applied to multiple VCOs.

It is heavily based on the circuits from the Roland system 100m 180 and 181 keyboard controllers.

Features:
- 1 V/octave CV input
- Master tuning control – approx. +/- ½ octave (range can be customised).
- Switchable glide. If no jack is inserted into the “On” socket, the glide is always “on”. If a jack is inserted, approximately +1.2V will turn the glide on, anything less turns the glide off.
- Two modulation CV inputs with level controls
- +/- one octave switch
- Output with built in buffered mult.
- CV Trigger extractor, with gate input.
o The trigger extractor generates a 2mS +12V pulse whenever there is a step change to the 1V/Oct input.
Experiments indicate it will actually sense sharp step changes down to about 25mV (i.e. about 1/3rd of a semitone at 1V/Octave). The trigger pulse length and the sensitivity are easily customised.
o The “Gate” input adds a trigger at the start of each Gate pulse. Plugging a gate signal into the Gate socket generates a trigger pulse on the leading edge of the gate signal, even if the CV doesn’t change.
- Can act as Doepfer bus master, or use Doepfer bus signals for default CV and Gate inputs.

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