schlappi engineering


Regular price $260.00


Available in Silver or Black Please select Panel color when ordering


The 100 Grit is a touch-controlled distortion unit inspired by the output section of a vintage synthesizer. Sonically it can range from subtle tone shaping to complete sonic obliteration depending on the positions of the knobs and output chosen.

The 100 Grit consists of a low pass filter, VCA, and distortion section with 8 touch points, voltage control overdrive, resonance, and frequency, along with a plethora of feedback paths allowing it to operate as a hands-on performance instrument with or without any input.

The touchpoints enable touch-controlled resistive patching between the cv points (gain, frequency, and resonance), sensitive points in the distortion circuit, and different distortion outputs for a mix of touch-controlled audio rate modulation and crackle box-like noise freakouts.

The low pass filter is a 24dB self-oscillating transistor ladder type with a jumper selectable resonance compensation scheme allowing more bass and volume at higher resonance settings.

The VCA is an OTA based circuit, which when pushed past 75% will impart a soft distortion characteristic, turning a triangle wave into a sine before being finally driven into a square wave close to max. If the levels are kept lower it is a reasonably clean vintage-style output section.

The distortion circuit is driven by the VCA, allowing for a voltage controlled gain amount and goes from heavy to extreme, especially when the x100 gain switch is engaged or the various self-modulation/feedback paths are utilized. The circuit is loosely based on a headphone amplifier circuit cranked into instability and self-oscillation.

Each Audio and CV input is normalized to a different feedback path, allowing for wild, self-oscillating distortions and extensive tone control with no external CV applied, or full control from external sources.


  • 8 brass touchpoints

  • 2 inputs to transistor core low pass filter

  • Voltage control over frequency, resonance, and gain

  • OTA VCA with soft saturation characteristics

  • Distortion circuit based around a vintage headphone amplifier driven into instability

  • Three-position x100 gain switch with off, on, and momentary-on settings

  • Each input and cv input is normalled to a different feedback path (6 total)

  • Separate outputs for the VCA and distortion

  • Can operate as a vintage-voiced VCA and LPF or a screaming distortion and noise effect

  • All analog design

  • 14 HP

      HP SIZE: 14HP
      +12V 55mA, -12V 70mA

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