Optothing v3.0

optocoupler VCA/filter/sound-mangler

BE AWARE! This is a deliberately lo-fi module - if you want crystal clear sound reproduction, fidelity or whatever then you won't find it here. The module relies on the properties of a photo-transistor to generally dirty up any signal coming passing through it; think of it as kind-of like a low-pass gate with built in distortion and a few other properties too.


In the beginning there was the OptoThing - it was an interesting piece of kit in that it sometimes behaved a bit like a VCA, or maybe a filter, or maybe somewhere in between. It was a classic example (I think) of how something with a relatively low parts count could do weird and wacky things to your sound.

Things have moved on a bit since then - the OptoThing hasn't been available for a while and I figured that it was about time for a revamp, so here it is. Not a lot has changed, really, except that the new version of the module packs two optocoupler gates into a 4HP module - double your opto, double your thing. Operation is the same - give it a CV, and input and an output and twiddle the pot until you get a response that you like.

The two CV inputs are normalled together, so any CV presented to the top half of the module will also appear in the bottom half unless there's something plugged into the lower CV jack.

Use it as a 'ghetto' VCA with an envelope-type waveform or use swept voltages to create bizarre, filter-like effects. Whilst the opportunities aren't quite endless, there are still quite a few of 'em.

Panels are made from laser-cut and engraved, 3mm, opaque black perspex - also provided are suitable mounting screws (M3x10). There's no power cable as this is a fully passive module


  • Module does not draw current
  • 12 mm deep

Available as an assembled Module and as a DIY project.

This Module is currently available.

$32 Price in €
4 HP FilterVCA
submitted Dec 1st 2018, 18:21 by dTRASHCANb

Buy Online

These merchants probably sell this module. Huh?


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