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Synapse Resonant Drive

Based On
Systech Overdrive
Effect Type
Resonant filter fuzz
Build Difficulty
Project Summary
A rare fuzz pedal that combines hard-clipping distortion with an extreme resonant filter that lends a vocal “stuck wah” quality.
Synapse Resonant Drive printed circuit board

Printed Circuit Board

What's included?
PCB only. Build instructions and parts list can be viewed or downloaded from this page.


In stock

Complete Kit

Not yet available.
Kits are developed based on interest, so if you’d like to see one for this project, let us know.
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Project overview

The Synapse Resonant Drive is based on the Systech Overdrive, a fuzz pedal released in the early 1970s before the idea of “overdrive” had become distinct from “distortion” and “fuzz”.

Today, Systech’s most well-known circuit is the Harmonic Energizer (available from Aion FX as the Parsec), which is similar in its frequency-sweepable filter but lacks any of its own clipping. The Harmonic Energizer was most notably used by Frank Zappa.

It’s not known whether the Overdrive was derived from the Harmonic Energizer or the other way around—but either way, they’re similar in concept, and the Overdrive is very unique among drive pedals. It doesn’t have the Zappa association, but it’s interesting enough that it’s worth your time.

The resonant filter can be tuned from 133 Hz to 900 Hz, but unlike a wah, its Q is very sharp, and it has a definite “tuned” quality that can either complement the notes being played or collide in a dissonant way.

There is no way to disable the filter or reduce its gain, so it’s definitely not an always-on tone stap;e, but very useful as a quirky effect to get some spaced-out filter tones are hard to come by in such a small package.

The Synapse is a straight clone of the Systech Overdrive with no changes except changing Systech’s standard polarity protection for a simple Schottky diode as in other Aion FX projects.