Rock Throbster

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Rock Throbster is, primarily, a tremolo effect. But it’s also a lot more. Internal LFO, with selectable square and triangle waveforms, provides the backbone for classic tremolo sounds. Push the LFO up into the audio range to achieve audio-rate AM effects. CV control over the rate and an external modulation input provide additional modulation effects and flexibility.

The real fun comes from the resonant distortion. Start subtle with softly clipping overdrive, or crank it up to harsh, obliterating distortion. The resonance knob adds resonant peaks at lower distortion levels, mimicking wah-type filter sounds. At higher distortion levels, the resonance knob acts as a tone control, effecting the brightness of the distortion.

Schematic

As with any schematic found on the internet, exercise caution when building. Test the build before plugging it into your case. If you find mistakes in the schematic, or you have recommendations for improving the design, feel free to contact us and let us know.

Download Rock Throbster v1 PDFDownload

BOM

  • Capacitors
    • 4.7nf (2) C1, C2
    • 47nf (1) C4
    • 0.68uf (1) C3
  • Resistors
    • 1k (6) R3, R5, R7, R8, R12, R13
    • 47k (1) R4
    • 51k (1) R9
    • 56k (1) R10
    • 100k(4) R1, R2, R6, R11
  • Potentiometers
    • 100k (3) RV1, RV2, RV3
    • 1M (1) RV4
  • Transistors
    • 2N7000 (1) Q1
  • ICs
    • TL072 (1) U2
    • TL074 (1) U1
  • Diodes
    • 1N4148 (3) D1, D3, D4
  • LEDs (2) D2, D5
  • Audio jacks (4) J1, J3, J4, J5
  • Switching audio jacks (1) J2
  • SPDT switch (1) SW1
  • Vactrol (1) U3

Demos

Demo of the clean out: Starting with triangle, then square waves and finishing with CV over the rate
Demo of the distorted out: Sweeping from soft clip to full distortion, then sweeping the resonance. Various tweaking of the distortion and resonance while moving between square and triangle modulation.
Demo of external modulation and distortion: Patching a slow-ish LFO into the External Mod jack to focus more on the resonant distortion. Patched through reverb, delay and panning modules for effect.
Demo of slow tremolo stuttering: Using a slow and off-beat square wave to introduce syncopation and stuttering to a sequence. Patched through reverb, delay and panning modules for effect.
Demo of audio-rate external modulation: Sequenced sine wave patched to the input, sample & hold patched into the pitch CV of a second oscillator, sine of the second oscillator patched through a VCA with a very short envelope, output of the VCA patched into the External Mod jack. Clean Out patched through reverb, delay and panning modules for effect.