Schlappi Engineering — 100 Grit
Schlappi Engineering 100 Grit Manual (PDF)
(Manual also available via Schlappi Engineering website)
Schlappi Engineering 100 Grit Cheat Sheet
Module Overview
- Analog filter-based distortion/VCA with touch points for chaotic interaction.
- Based on a transistor ladder low-pass filter, OTA VCA, and distortion circuit.
- 8 Touch Points for “circuit bending”-like performance.
Panel Controls & Functions
Knobs
- IN 1 / IN 2: Audio input gain for each input.
- FREQUENCY (large center knob): Filter cutoff frequency.
- FM 1 / FM 2 (with CV pots under each): Control cutoff via external CV.
- RES: Filter resonance.
- RES CV (with CV pot under RES): External CV to resonance.
- GAIN: Output/VCA gain and distortion amount.
- GAIN CV (with CV pot under GAIN): External CV to gain stage.
Switches
- Gain x100: Massive distortion/feedback switch.
Input, Output, & Touch Point Reference
Audio Inputs
| Jack |
Voltage Range |
Notes |
| IN 1 |
±12V (24Vpp) |
Main audio in (mixes to filter). |
| IN 2 |
±12V (24Vpp) |
Second audio in (mixes to filter). |
CV Inputs
| Jack |
Voltage Range |
Function |
Normalling/CV Action |
| FM 1 |
±12V |
Filter cutoff CV (sums w/ FM 2). |
Norm: DIST (distortion output FM). |
| FM 2 |
±12V |
Filter cutoff CV (V/Oct okay for tracking). |
- |
| RES CV |
±12V |
Resonance CV. |
Norm: DIST (audio-rate resonance mod). |
| GAIN CV |
±12V |
VCA gain and distortion depth. |
Norm: POLE 2 (second filter pole out FM). |
- Unity gain at 5V for GAIN and RES CV. Higher voltage = more gain.
Audio Outputs
| Jack |
Voltage Range |
Source |
| OUT |
up to ±11V |
Post-filter, pre-distortion (VCA/clean). |
| DIST |
~±6V |
Distortion circuit output. |
Touch Points
- Eight brass balls (shown in touch point map).
- Each is a direct circuit node for “patching” with fingers, cables, clips, or conductive objects.
- Used for chaotic control and feedback.
Touch Point Functions (Clockwise from top left)
Left Set:
- DIST 2 OUT – Second distortion circuit out (audio).
- GAIN CV – VCA gain CV node.
- DIST 2 AMP PIN – Dist 2 amp core (capactive/feedback).
- RES CV – Resonance CV node.
Right Set:
- DIST 1 AMP PIN – Dist 1 amp core.
- FREQ CV – Filter cutoff CV node.
- DIST OUT – Main distortion out.
- GAIN CV – Same as left.
Headers (Jumpers)
- J9: Input to Resonance – ON by default. Removes “bass drop” at high resonance. Remove for classic, whistling, self-oscillation style resonance.
- J10: Output Source – Default right two pins (“VCA” output, OUT is post-VCA). Move to left pins for filter direct output.
Calibration
- RV3: Resonance Amplitude – Sets self-oscillation threshold.
- RV4/RV8: Symmetry – Factory adjusted; do not touch.
Typical Patch Setups
VCF/VCA
- Audio In via IN 1, monitor OUT.
- GAIN above 75%: heavy distortion.
- ADD Env to GAIN CV for VCA.
- V/Oct to FM 2 = pitch tracking.
Distortion
- Monitor DIST output.
- GAIN and GAIN CV = distortion level.
- Use RES CV for unique feedback sounds.
Noise Box
- No input; monitor DIST out.
- All knobs ~25-60% up.
- Play touch points for chaotic noise.
Extra Notes
- All CV/audio inputs: Protected to ±12V (rails).
- Touch Points: Safe to bridge/patch, always current-limited.
Voltage Reference
- Nominal input signals: ±5V (10Vpp), but up to ±12V is fine.
- OUT: up to ±11V, rails possible with hot input/gain.
- DIST: Up to ~±6V (clipped/limited by circuit).
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