User customizable Steiner-Parker filter


Scrat is an aggressive sounding multimode Steiner-Parker filter with a twist: You can change the resonance flavour by plugging in components like diodes, capacitors or resistors (even LEDs and/or light-dependent resistors) directly to the front panel. A set of preset cartridges is also available, which gives you instant access to a variety of filter sounds. You could even make your own. Or go all in and connect some jumper wires to a breadboard for pretty much endless possibilities.

The 2-pole filter (12 dB/octave) supports both high-pass and low-pass mode. Even without external components or cartridges, the resonance behaviour can be changed in various ways via switches on the front panel. Both resonance and cutoff can be fully CV controlled, and the cutoff CV sensitivity can be adjusted as well.

The module contains an adjustable pre-filter drive circuit, which pairs very well with the Steiner-Parker design.

Scrat is available from July 2022 as a full DIY kit from retailers. It's a relatively easy build to complete, with a low component count and no SMD or other tricky parts. A set of 4 preset cards called Nuts (Acorn, Almond, Cashew and Pecan) is also available.

If you're interested in a prebuilt module, feel free to reach out by email.

The schematic (link in sidebar) is open-source.

scrat-angled scrat-back scrat-closeup scrat-nuts