Schlappi Engineering — Angle Grinder

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Using Schlappi Engineering Angle Grinder For Eurorack Sound Design

Angle Grinder is a uniquely flexible quadrature oscillator and state variable filter with deep modulation possibilities. Its SPIN (oscillator/filter core) and GRIND (nonlinear waveshaper/comparator) sections enable a wealth of wild sonic territory. Here are creative modulation approaches to craft distorted percussion, gnarly basslines, and atmospheric pads.

Core Modulation Possibilities

1. FM1 / FM2 Inputs

• FM1: Switchable between linear and exponential FM via jumper. Deep, audio-rate modulation here creates classic metallic or chaotic timbres.
• FM2: Exponential FM, great for aggressive pitch bends and bass growls.

2. GRIND Sliders & CVs

• Control the amplitude of phase-compared square waves subtracted from the input, allowing dynamic waveform mangling.
• CV (0–5V) modulates grind amount per phase; envelope or sequencer control here is key for percussive and bass movement.

3. GRIND → SPIN / Damping

• The GRIND → SPIN knob controls feedback from the waveshaper to the oscillator, morphing the overall behavior between pure oscillation and wild filter feedback.
• Modulating this parameter by CV (using a VCA + LFO/envelope) adds evolving distortion and self-oscillation artifacts.

4. Inject and External Input

• INJECT bypasses GRIND and can soft-sync the core, used with gates or audio for phase resets and extra punch.
• Regular INPUT takes in audio or CV to be wrangled by the GRIND comparators; try feeding percussion hits, FM modulator oscillators, or drones.

Creative Sound Design Techniques

A. Distorted Percussive Sounds

1. Patch
2. Leave Angle Grinder in LOW or HIGH range—try LOW for snappy modulation.
3. Patch gate, drum trigger, or envelope generator to one or more GRIND CV inputs to create shape/pulse-dependent distortion.
4. Use a drum sound or noise burst into INPUT (or INJECT for sharper sync).

5. Turn GRIND → SPIN knob up for feedback-driven distortion.

6. Modulate

7. GRIND sliders: Sequence or envelope-modulate individual sliders for evolving timbre with each drum hit.
8. FM1/2 Inputs: Patch percussion sound, audio-rate LFO, or random stepped CV to FM1 or FM2 for pitch artifacts; use exponential FM for wilder chaos.

9. Damping: Modulate with slow LFO for rhythmic shifting from tight hits to dirty resonance.

10. Result:

11. You'll get squelchy, blown-out, bitcrushed percussive timbres—great for glitch, techno, and hard electro!

B. Dubstep/Drum & Bass Basses

1. Patch
2. Set Angle Grinder as main VCO: Use V/OCT for pitch sequencing.
3. Crank GRIND → SPIN for aggressive feedback mixing.
4. Mult out 0° or 180° output to your main audio, and another phase output to modulate a filter or VCA downstream for stereo movement.

5. Mult envelope or LFO to both GRIND CV and FM2 for dynamic growl and movement.

6. Modulate

7. Send fast envelopes or wobbly LFOs to FM2 for pitch sweeps and growls.
8. Use clocked ramp or stepped random to GRIND slider CVs for formant-like bass movement.

9. Patch accent gates or kicks to INJECT for rhythmically resetting/syncing the oscillator — creates sync’d bass punches.

10. Result:

11. Brutal, vowel-like or metallic basses loaded with movement (think classic "talking" bass).
12. Explode low-end with subharmonics by mixing both sine and GRIND outs.

C. Haunting Atmospheric Pads

1. Patch
2. Set Angle Grinder to LOW range for LFO-speed quadrature outputs (modulate VCAs/panners downstream for enveloping stereo effects).
3. Patch drones or reverb-washed signals into INPUT; keep GRIND sliders low for subtle effect, or up for lo-fi color.

4. Use slow, unipolar LFOs on GRIND CVs to gently morph the waveshape.

5. Modulate

6. FM1 (linear), with slow LFO/attenuated noise or even recorded sample waveform for organic drift and detune.
7. GRIND → SPIN: Slowly move manually or with a slow envelope to sweep between pure, filtered, and feedback-warped tones.

8. Damping: Animate with footsteps, envelope, or random for evolving resonance and shimmer.

9. Result:

10. Four drifting, phase-shifted outputs (all phase-locked) allow for lush quadraphonic or moving stereo textures.
11. GRIND section adds brittle, spectral edges and eerie harmonic motion.

Bonus Tips

• Use ALL PASS (phase shifted output) for unique layering and phasing effects.
• Feedback external audio (resample) through INPUT or INJECT for abrasive, self-modifying noise textures.
• The unlimited output headroom (up to 22Vpp!) lets you overdrive mixers and VCAs downstream for bonus saturation.

For more patching inspiration, check out the Angle Grinder PDF Manual.

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