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Sample and Hold
The Sample and Hold module produces stepped output signals by sampling the instantaneous value
of any signal at its input. The stepped levels it produces are useful for controlling oscillator and filter
frequencies and occasionally VCA gain. Any signal whatsoever may be sampled.
The default input is from the Noise Generator
❶, so that the step sequence is random. When the
signal being sampled is random noise, the output voltages are correspondingly unpredictable. An
infinite variety of cyclical output patterns may be obtained, on the other hand, by sampling a periodic
waveform. Different ratios of the sampling frequencies to the frequency of the waveform being sampled
create different melodic patterns (if the output level is controlling a VCO).
The Sample and Hold circuit
❷ has a signal input (the waveform to be sampled), a trigger input,
and an output giving the result of the sampling operation. The trigger input is defaulted from the
internal clock, but any square or pulse wave, or the keyboard gate or trigger signals, will work.
The level control
❸ attenuates the input signal before it is fed to the Sample and Hold circuit. The rate
control ❹ actually belongs to the internal clock; when that is disconnected from the Sample and Hold
circuit, the rate control has no effect on the operation of the Sample and Hold circuit.
Internal Clock and Electronic Switch
The rate control ❶ actually belongs to the Internal Clock. When the Internal Clock is disconnected from the
Sample and Hold circuit, the rate control has no effect on the operation of the Sample and Hold circuit.
The Internal Clock is a manually controlled low-frequency square-wave oscillator. It is the default trigger
source for the Sample and Hold device. It is also hardwired as the clock source for the Electronic Switch.
Under MIDI control, the Internal Clock may be synchronized to incoming MIDI Beat Clocks.
The Electronic Switch
❷ has two connections on one side and one on the other, as indicated by the panel
graphics. For clarity, let’s call these three jacks A-1, A-2, and B. The switch alternates between connecting
A-1 to B, and A-2 to B. It doesn’t matter which side is the signal source and which is the destination;
the switch works the same regardless. The switching rate is governed by the Internal Clock. This is a
permanent feature of the switch.