Sample and Hold modules (S&H) are sometimes overlooked, but they can be very versatile devices. Continue reading to find out how a module with only two inputs, one output and no knobs can drastically expand your modulation capabilities.
The function of a sample and hold circuit is partially revealed by the name. Patch a dynamic voltage source into its signal input and then patch a gate or trigger source into its gate input. Now each time you send a trigger the current voltage amount will be read, also known as sampled, and then held, or stored. The stored voltage is then sent out of the output until the next gate input is received and the stored voltage is replaced by the new sample.
If you were to patch an LFO’s sine wave output into the S&H’s signal input and sent a trigger into the trigger input, the output would correspond to the state of the LFO- if it was high then the held voltage would be high, if it was low then the held voltage would be low. But what if you send a regular stream of gate messages into the trigger input, such as from a fast square wave LFO or clock? The output will be a stair stepped, quantized version of the original LFO.
You can then use that stair stepped sine to modulate the pitch of a VCO, the cutoff of a filter, or nearly any other modulation CV input.
For even more fun, patch out of a white noise generator into the signal input of the sample and hold module. If you keep the same steady gate signal patched into the gate input then you will now be getting regular steps of random voltage. It’s a very fun effect for a retro analog sound. Noise is so often the input for sample and hold circuits that often there will be a noise generator built into the S&H module. I recommend running the output through a slew processor to give a glide, or portamento, between each step. In the photo below you’ll see the noise signal on top and on the bottom is the stepped output of a sample and hold Eurorack module by EMW from Brazil.
A sample and hold module can also be used as a sample reducer audio effect. Run any audio through the S&H signal input and then run a VCO’s square wave output into the gate input. As you slow the VCO’s frequency you will hear an increased amount of sample reduction effect to your audio signal.
Can you think of any more uses for sample and hold? There’re a lot more possibilities out there!