This module is a little fuzzy. Bears are fuzzy. My favorite bear is Fozzie the Bear. Fozzie sounds like fuzzy. Fozzie likes to tell bad jokes and celebrate his bad jokes with his trademark saying “Wocka wocka wocka”.

And that’s why this module is called Wocka.

Borrowing heavily from a circuit attributed to the mysterious “R. Lockhart Jr.”, this diode/transistor-based fuzz distortion is a wave destroyer.

Gain ostensibly controls the amplification of the effect in the wet mix, but doesn’t quite achieve that effect. Instead, it fades from a lightweight version of the effect; through a nasally, formant filter-y distortion; and into a classic high-gain distortion.

Mix blends from completely dry signal to completely wet.

Capping all of this off is CV input over the amount of distortion*, using a novel implementation of voltage control that I might have made up**.

* Fixed voltage (+12v) is normalled to the CV input, so when nothing is plugged in, the distortion is at 100%. CV controls distortion amount (0v = 0%; 12v = 100%).

**Almost assuredly not, but I’ve never seen this trick used anywhere else. Of course, that might be because it’s a really bad idea to design a circuit this way and I’ve designed something that will burn out/blow up/render me sterile.

Schematic

Schematics are provided as-is. Never trust that any schematic on the internet is foolproof. Test your build in isolation before introducing it to the rest of your modules.

BOM

• Capacitors
  • 220pf (1) C2
  • 0.1uf (1) C3
  • 1uf (1) C1
• Resistors
  • 1k (2) R6, R7
  • 10k (4) R2, R4, R5, R10k1
  • 500k (1) R3
  • 5M (1) R1
• Potentiometers
  • 10K (1) RV1
  • 100K (2) RV2, RV3
• Transistors
  • MPSA18 (1) Q1
  • 2N3906 (1) Q2
  • 2N3904 (1) Q3
• Diodes
  • Germanium diodes, such as 1n270 (2) D1, D2
• ICs
  • TL072 (1) U1
• Audio jacks (2) J1, J3
• Switching audio jack e.g., Thonkiconn (1) J2

Demo

Clangorous demo