Named after the Mighty Krillin’s unstoppable sawblade of doom, the Destructo Disc is a sawtooth oscillator gone mad. Two waveshapers and an array of 555-based saw-width modulators transform a basic sawtooth waveform into a vast array of aggro sounds.

Three tunable width modulators create three permutations of the same wave. When mixed with each other, and with the original signal, all four waves modulate one another, occasionally reinforcing or phase-cancelling one another. A width bias knob adjusts the saw-width of all three modulated signals.

Underneath, and on top of, these modulators are two waveshapers. Waveshaper 1 mangles the sawtooth wave before it is modulated, with optional CV control on the depth. Waveshaper 2 mangles the mix of the modulated signals from the 555 array.

The Destructo Disc borrows heavily from Mortiz Klein’s Shapes VCO and Forrest M. Mims III’s frequency divider. Q1 and Q2 should be mounted so that the flat sides are touching one another. For best results, use thermal tape or thermal paste between the touching sides of the transistors. Adjust trim pots on RV5 to set the saw width of each 555 array. The trim pot at RV4 is for calibrating the oscillator.

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
    • 2.2nf (1) C4
    • 10nf (3) C2
    • 47nf (3) C1
    • 1uf (5) C5, C6, C7, C8, C9
    • 10uf (1) C3
  • Resistors
    • 1.5k (3) R4, R8, R9
    • 2k (2) R15, R19
    • 10k (7) R11, R18, R21, R25, R26, R27, R28
    • 20k (2) R20, R23
    • 47k (1) R16
    • 100k (7) R1, R2, R3, R5, R7, R14, R17
    • 200k (4) R12, R13, R22, R24
    • 1M (2) R6, R10
  • Potentiometers
    • 1k (1) RV4
    • 10k (2) RV7, RV8
    • 100k (3) RV1, RV2, RV6
    • 1k Multiturn Trim (1) RV4
    • 1M Trim (3) RV5
  • Transistors
    • BC548 (1) Q2
    • BC558 (1) Q1
  • ICs
    • 555 (3) U1
    • TL074 (2) U4, U6
    • TL072 (1) U5
    • TL071 (1) U2
    • 40106 (1) U3
  • 10k thermistor (3) TH1, TH2, TH3
  • Audio jacks (3) 1v/o Input, CV, Output

Demo

Long demo of the Destructo Disc, starting with a sweep of the width bias with both Waveshapers at 0; then Waveshaper 1 is faded in followed by another sweep of the width bias; then Waveshaper 2 is faded in followed by another sweep of the width bias; then some playing around with various LFOs and envelopes in the Waveshaper CV.

Patching Ideas

Plug some control voltage into the 1v/o jack and enjoy the carnage.