The Cynare drum simulator is one of 3 CGS drum simulators from Ken Stone. It generates a single drum sound that can be adjusted to sound like a cymbal, hi-hat, snare drum, electronic drum, or numerous other percussive sounds.

It is a complete dedicated synthesizer in its own right, including six oscillators, a noise source, a mixer, an envelope generator, a VCF and a VCA.

How to use this module

There are two inputs for controlling the envelope of the generated sound. The first is Decay. Attack is preset at the fastest rate possible, the decay controlling the fall off rate of the envelope. This decay is also affected by the Damper control, which operates in parallel with the Decay. A gate input into the Sustain jack disables the damper, thus allowing two different rates of decay to be set depending on the input to the sustain jack. Note: if the damper decay rate is set to minimum, and the sustain input is below about 2V, the envelope will be set at minimum, with the decay control having very little effect, so if you do not wish to use the sustain input, the damper decay rate should be turned to maximum.

If a square wave or similar gate waveform is connected to both the sustain and trigger inputs, the fall-off of the envelope will be affected by the decay control while the gate signal remains high, the damper kicking in as soon as the gate falls low. This allows for easy implementation of open/closed hi-hat sounds etc

A little on how it works

TL072 "A" processes the incoming trigger and sustain signals. The trigger is converted to a short pulse, while the sustain input becomes a gate signal. The trigger pulse will charge the 2u2 envelope capacitor. The capacitor will then discharge through the decay pot, and if the sustain gate signal is low, thought the damper pot as well.

The resultant envelope is passed through a voltage divider and LED to drive pin 5 of the LM13700 which forms the heart of the VCA. The envelope is also passed through a processor that allows it to be scaled, and inverted, giving a range of positive and negative going envelopes to drive the VCF.

There are two noise generators, a conventional reverse biased emitter-base junction, and a "shimmer" generator consisting of six independent oscillators with their outputs "ring" modulated via the exclusive OR gates, and mixed.

A pot allows the ratio of noise to shimmer to be adjusted. A filtered version of the trigger pulse is used to generate an impact sound, and this is mixed with the output of the shimmer/noise section.

The filter section is directly taken from the Steiner VCF.

All of these sections form a small dedicated synthesizer, when wired in the appropriate order.