Music Thing Spring Reverb

I took a look at Sam’s spring reverb module when it came out, but decided I wanted something less crunchy. So I did this Kosmo adaptation of the Music Thing Modular driver (Mk II).

(Once again the 3D printed front panel is a stand-in until I get an FR4 one fabbed.)

There’s only few very minor circuit tweaks. As with the original it can, and in my build it does, include the Belton Accutronics “brick” as an alternative to the spring tank. It incorporates the Music Thing expansion module, which consists only of a pot to mix between tank and brick, and a pair of phono jacks on the front panel parallel to the ones on the PCB. (I didn’t bother mounting those on this temporary panel.)

I’m using this with an Accutronics 4EB2C1B tank. The behavior’s VERY sensitive to the trim pot, there’s a small window between basically dead and out of control where it’s all good.

Schematics, layout, Gerbers, and documentation may be found at:


Nice work, can we get a sound demo?

Haven’t recorded anything yet but since it’s the same as the Eurorack version here’s DivKid’s demo of that:


I put the fabbed panel and knobs on:

Extra boards and panels are for sale on Tindie:

(Discovered just as I was about to put the “To” panel jack on, I’d given it a ground connection on the panel. Oops. Two nylon washers and we’re good…)


Say if someone with the v1.0 did forget to put a nylon washer around the ‘to’ socket and they couldn’t hear any output afterwards, could that be the cause? Could a chip be fried?

I don’t really know, but I’d guess not? More likely some other assembly problem, I’d think.

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Turns out I was missing two components, don’t know how I missed them, looked over the board 100 times

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