Schlappi Engineering 100 Grit Touch-Controlled Distortion (Silver)

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.