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 over drive, 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 touch points 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 freak outs.
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.