Polykit Spring Reverb Driver

There were a few questions about my Spring Reverb Driver so I decided to create a public thread to have it all in one place.

It is a pretty simple module in Kosmo format which is capable of driving reverb tanks from 8ohms to 600ohms input impedance. It has a dry-wet and a resonance control. PCB and panel are the same so components stick out.

You need to adjust some resistor values according to your reverb tanks input impedance. The input coil must not be grounded to the tanks casing in order to make it work.

You can find the Kicad schematics, layout and gerber files at GitHub - polykit/kosmo-spring-reverb-driver: Schematics and PCB layout for a spring reverb driver in Kosmo modular format

This is a first version on the pictures. There were some flaws which are fixed in the actual version in the repository.

There is also a short demo here:


@JUXTAPOZ74 here you can see the actual wiring of the sockets, ground comes from the panel itself.

1 Like

Are those inverted terminals on the potentiometers? I guess I mean reverse orientation.

I bended the terminals on the pots in the inverse direction if that’s what you mean.

1 Like

I am not sure if I understand the “input not grounded” part. I have a BELTON B SN2EB2E/T tank and I checkd this document. So, I translated the code to
small, new, 2 springs, input impedance 600ohm, output impedance 2250ohm, medium decay, no outer channel, with tray.

There is this table:

And for some of the other letters it says if the input is (should be?) grounded (A,B,C,D) but for my tank it says: “E: 10’’ Leads, No Outer Channel” what does that mean?

1 Like

I have no idea but you can test with a multimeter if it’s grounded to the casing.

1 Like

And if it is, then I should not connect that ground to the one on the pcb?

No, you need to rewire the input coil so it’s not grounded anymore