100 Grit

Schlappi Engineering 14HP
DISTORTION FILTER VCF VCA NOISE

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Touch-controlled transistor-ladder LPF, OTA VCA, and vintage-headphone-amp distortion with 8 brass touchpoints. Normalized feedback paths, x100 gain switch, and a secondary unstable distortion comparator turn it into a self-contained performance noise box.

Patch Ideas · 8

★ Touchpoint performance distortion
Drum loop → IN 1 @ 75% · FREQUENCY mid · GAIN 75% · x100 OFF · play the 4 right touchpoints with a thumb · adjacent input/output pairs create resistive patches in real time
▸ Show diagram
Patch diagramPatch diagram with 3 modules and 2 connections. Modules: 100 Grit, Drums, Output. Signals: 2 audio.100 GritDrumsOutputIN 1: 75%FREQUENCY: ~12 o'clockGAIN: 75%x100: OFFIN 1audioDISTaudioOutaudioInaudio11. play touchpoints liveaudio
Self-feedback noise box
No inputs · IN 1 at 25% · IN 2 at 25% · GAIN 60% · GAIN CV 60% · RES CV 25% · x100 ON · listen to DIST · play all 8 touchpoints for screeching chaos
▸ Show diagram
Patch diagramPatch diagram with 2 modules and 1 connection. Modules: 100 Grit, Output. Signals: 1 audio.100 GritOutputIN 1: 25%IN 2: 25%GAIN: 60%GAIN CV: 60%RES CV: 25%x100: ONDISTaudioInaudioaudio
Laser percussion FM
Kick trigger → envelope → FM 2 @ high attenuation · FM 1 unpatched (DIST normalled in for dynamic FM) · RES mid · GAIN 75% · filter pings into screaming laser tails
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 3 connections. Modules: 100 Grit, Envelope, Trigger, Output. Signals: 1 audio, 1 cv, 1 trigger.100 GritEnvelopeTriggerOutputRES: ~2 o'clockGAIN: 75%FM 1: up (DIST feedback normalled)FM 2cvDISTaudioTrigtrigOutcvOuttrigInaudioaudiocvtrigger
★ Self-oscillating sine voice
No input · RES full CW · V/Oct → FM 2 · GAIN CV from ADSR · 100 Grit sings as a ladder-sine voice with distortion character via x100
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 3 connections. Modules: 100 Grit, Sequencer, ADSR, Output. Signals: 1 audio, 1 cv, 1 pitch.100 GritSequencerADSROutputRES: full CWGAIN: 0x100: OFFFM 21v/octGAIN CVcvOUTaudioPitch1v/octOutcvInaudioaudiocvpitch
★ Dynamic audio-rate FM resonance
Synth pad → IN 1 · RES mid · RES CV up with unpatched RES CV (DIST normalled for audio-rate res mod) · screeching harmonics ride the pad's resonance
▸ Show diagram
Patch diagramPatch diagram with 3 modules and 2 connections. Modules: 100 Grit, Pad, Output. Signals: 2 audio.100 GritPadOutputIN 1: 50%RES: ~1 o'clockRES CV: 60% (DIST normalled)GAIN: 60%IN 1audioOUTaudioOutaudioInaudioaudio
x100 punch-in explosions
Bass sequence → IN 1 · normal filter settings · perform x100 (ON) momentary spring for punctuation distortion bursts during a riff · spring returns to clean
▸ Show diagram
Patch diagramPatch diagram with 3 modules and 2 connections. Modules: 100 Grit, Seq, Output. Signals: 2 audio.100 GritSeqOutputIN 1: 75%FREQUENCY: ~12 o'clockGAIN: 60%x100: momentary (ON) on accentsIN 1audioDISTaudioOutaudioInaudio11. live x100 punchesaudio
Cable-as-touchpoint ring mod
Patch cable tip from external LFO into GAIN CV touchpoint · brass ball receives the CV via resistive connection · gain modulates audio-rate for AM/ring-mod effects between inputs and touchpoints
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 3 connections. Modules: 100 Grit, LFO, Source, Output. Signals: 2 audio, 1 cv.100 GritLFOSourceOutputIN 1: 50%GAIN: 60%IN 1audioGAIN CVcvOUTaudioOutcvOutaudioInaudio11. via brass touchpointaudiocv
Dual-output splitter
Flip J10 jumper to direct-filter · OUT = clean filter, DIST = distorted · stereo send: clean L + dirty R · GAIN controls only the distorted side
▸ Show diagram
Patch diagramPatch diagram with 3 modules and 3 connections. Modules: 100 Grit, Source, Output. Signals: 3 audio.100 GritSourceOutputJ10 jumper: direct (filter tap)IN 1: 75%GAIN: ~2 o'clockIN 1audioOUTaudioDISTaudioOutaudioIn LaudioIn Raudio121. clean filtered2. distortedaudio

Behaviors

8 brass touchpoints finger, cable tip, alligator clip on touchpoint

Eight brass balls expose internal nodes as resistive patch points: DIST 2 OUT, GAIN CV, DIST 2 AMP PIN, RES CV, DIST 1 AMP PIN, FREQ CV, DIST OUT, GAIN CV. Inputs are adjacent to outputs so any two-point touch creates a connection. Bridge with fingers, cables, or conductive material for performance distortion.

Feedback normalization leave input unpatched · turn up its attenuator

Each audio/CV input normalizes to a hidden internal feedback path. IN 1→DIST 2, IN 2→DIST, FM 1→DIST, RES CV→DIST, GAIN CV→POLE 2. Turning an input's attenuator becomes a feedback amount control — the module self-generates sound without any input cable.

x100 momentary (ON) spring position held

Momentary side of the gain switch springs back to OFF when released. Lets players punch in extreme distortion bursts without latching — transient-shaped chaos controlled by the switch.

DIST 2 secret comparator IN 1 attenuator turned up with no cable

DIST 2 is an unstable distortion amp that compares the VCA output with the DIST output. Not available at any jack — only reachable via normalization or the DIST 2 OUT touchpoint. Produces extreme square-wave chaos ideal for noise-box patches.

Self-oscillating sine source RES CW · no input · FREQUENCY swept

Ladder filter self-oscillates into a clean sine. Plays V/Oct via FM 2 as a filter-voice oscillator. Calibration trim RV3 sets the self-oscillation threshold.

J9 Input-to-Resonance jumper internal jumper J9

Default ON: preserves bass and prevents resonance volume loss (classic-synth style). Removed: resonance takes over the input, whistling character, self-oscillation overtakes the signal.

J10 Output Source jumper internal jumper J10

Default VCA: OUT is VCA-affected. Switched: OUT taken directly from filter output, bypassing the VCA so GAIN only controls DIST. Turns 100 Grit into two independent filter+distortion outs.

Noise-box mode no inputs · all attenuators ~25–60% · x100 ON · play touchpoints

With nothing patched, the normalizations form a self-oscillating feedback network. Playing two or more touchpoints simultaneously modulates the internal signal paths — screams, radio-pickup artifacts, and rhythmic squealing chaos.

Controls

Global IN 1 Input attenuator for IN 1 jack. Also sends DIST 2 comparator into filter when unpatched, creating extreme square-wave chaos as a noise source.
Overdrives 50–75% · normals DIST 2 feedback
Global IN 2 Input attenuator for IN 2 jack. Normals DIST output back into the mixer as an opposing resonance path when unpatched.
Normals DIST feedback
Global FREQUENCY Cutoff of the transistor-ladder 4-pole LPF. Large centre knob. Must be up to pass audio.
Sums with FM 1 + FM 2
Global FM 1 Attenuator for FM 1 CV input. When unpatched, normals DIST output into filter cutoff for dynamic audio-rate FM — laser/zap percussion.
Normals DIST feedback
Global FM 2 Attenuator for FM 2 CV input. Used for V/Oct tracking when patched.
1V/Oct tracking possible
Global RES Filter resonance bias. Self-oscillates when pushed; threshold set by internal RV3 trim.
Self-oscillating · sine when isolated
Global RES CV Attenuator for RES CV input. Unpatched, normals DIST output as audio-rate resonance modulation for screeches riding on the resonant peak.
Audio-rate modulation · normals DIST feedback
Global GAIN VCA gain. Also drives the distortion circuit harder. No sound without some initial gain.
Overdrives above ~75% · gates both OUT and DIST
Global GAIN CV Attenuator for GAIN CV input. Unpatched, normals filter POLE 2 (12dB output) into VCA CV for subtle harmonic-shift distortion.
5V = unity · normals POLE 2 feedback
Global x100 Switch Three-position gain multiplier. OFF = normal. ON = x100 always. (ON) = momentary spring x100 for extreme distortion bursts.
OFF / ON / (ON) momentary

I/O

IN · 6

  • IN 1
    Primary filter input. Mixed with IN 2 into the ladder filter.
    NORM → DIST 2 comparator output (square-wave chaos noise source)
  • IN 2
    Secondary filter input.
    NORM → DIST output (distorted resonance opposition path)
  • FM 1 CV
    Filter-frequency CV input.
    NORM → DIST output (dynamic FM from distortion signal)
  • FM 2 CV
    Filter-frequency CV input. Used for V/Oct tracking.
  • RES CV CV
    Resonance CV input. Audio-rate capable.
    NORM → DIST output (audio-rate resonance modulation)
  • GAIN CV 5V = unity CV
    VCA CV input. 5V = unity, more = gain above unity.
    NORM → POLE 2 (12dB filter tap) — harmonic-shift AM

OUT · 2

  • OUT ~10Vpp clean · up to ~22Vpp pushed AUDIO
    VCA output following the filter. Jumper J10 can re-route this to direct filter output (pre-VCA).
  • DIST ~12Vpp max (self-limiting) AUDIO
    Distortion-amp output after the VCA. Vintage headphone-amp circuit driven into instability. Self-limiting.