A versatile foldback distortion module for my DIY modular synthesiser.

This module distorts the shape of an incoming signal, by “folding back” the peaks that go over/under a threshold voltage back the other direction.

The threshold voltage can be set with a panel control, and additionally supplied as a control voltage, for even more interesting effects.

Depth of foldback, as well as symmetry can be set. It’s a fun creativity tool to apply on both audio and modulation signals.

Work Involved

  • Circuit design and simulation; conceptually mainly using Falstad CircuitJS and further using LTSpice.
  • Schematic capture (KiCad)
  • PCB design, split into two stacked boards (KiCad)
  • Panel design (Inkscape)
  • PCB Assembly, panel assembly

Additional Images

Side view:

Rear view:

Boards de-stacked:

All design files, including some variations of the Falstad simulation, can be found on GitHub: Distortion module