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OPTO3.5: PCB/panel set for passive optocoupler VCA/low-pass gate module (4HP)


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.



Same deal, but with Alpha pots for added niceness ...

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. There's no power cable required as this is a fully passive module

BOM and schematic can be found here:

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