Schlappi Engineering — Three Body

Manual PDF

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Below is a condensed "cheat sheet" reference for the Schlappi Engineering Three Body oscillator module, including jack/knob/voltage details and an operator's quick-start guide.

Three Body Cheat Sheet

Overview

Triple digital oscillator for phase and FM synthesis.
Flexible normalization between oscillators for complex stereo, drone, and FM patches.
Switchable mode/state per oscillator for FREE (classic VCO/LFO) or RATIO (FM/phase/carrier).

Jack Reference

Jack	Type	Voltage Range	Function	Notes
V/OCT (per osc)	In	-8V to +8V	Linear pitch, best tracking -5V to +5V	Tracks 1V/oct (+RATIO in ratio mode)
FM	In	-8V to +8V	Frequency modulation (Expo/Lin)	Will clip above 16Vpp (bipolar), 8V (uni)
PHASE	In	-8V to +8V	Phase modulation	Always active, state independent
FM/PHASE INDEX	In	0V to +10V	Index VCA CV (mod amount)	Unipolar, will clip below 0V/above 10V
SYNC	In	~0.7V threshold	Hard sync or ratio tracking	Rising edge triggers sync/tracking
TRANSPOSE	In	-8V to +8V	Global pitch offset	No effect in ratio mode
SINE	Out	-5V to +5V	Sine wave	Always available
COSINE	Out	-5V to +5V	Cosine wave (center osc only)	90° ahead of sine (nominal, not under PM)
TRIANGLE	Out	-5V to +5V	Triangle wave
SAW	Out	-5V to +5V	Saw wave
COSAW	Out	-5V to +5V	Cosine saw (center osc only)	90° ahead of saw
SQUARE	Out	-5V to +5V	Square wave

All outputs are bipolar, DC-coupled, ~10V peak-to-peak.

Control Summary

Knobs (per oscillator unless noted)

COARSE/MULT – Coarse pitch / Ratio Multiplier
FINE/DIV – Fine pitch / Ratio Divider
FM INDEX – FM depth (outer oscillators)
PHASE CV – Phase modulation depth (outer oscillators)
PHASE INDEX 1/2 – Phase mod index depth (center oscillator, two separate inputs)
FM CV – FM modulation depth (center oscillator)

Jacks (per oscillator)

See Jack Reference above

Switches (per oscillator)

FREE / RATIO
FREE: Classic VCO/LFO mode (expo/linear FM & standard pitch)
RATIO: Tracks center or external via ratio (FM/phase in ratio domain)
LIN / EXP / PH (PHASE)
FM/Phase mode: Linear, Exponential, or Phase
HIGH/MULT / LOW/DIV
Range or multiply/divide for ratio/carrier frequency
(Center has additional phase index controls)

Mode Summary

Mode	Description
Free Expo	LFO/VCO with exponential FM
Free Lin	LFO/VCO with linear FM
Ratio Phase	Tracking (FM/PM) with phase mod and CV over mult/div
Ratio Lin	Tracking with linear FM and CV over mult/div

Indicators/LEDs

Three large LEDs: Show sine output (blue=pos, red=neg, purple=audio rate)
Four small LEDs: Show index VCA modulation activity

Voltage Ranges (Summary)

V/OCT, PHASE, FM inputs: -8V to +8V accepted; best tracking -5V to +5V
INDEX / PHASE INDEX inputs: 0V to +10V unipolar (envelopes, will clip below/above)
SYNC in: ~0.7V rising edge triggers sync/tracking
Outputs: -5V to +5V typical, up to ~12Vpp on some systems

Basic Patching Tips

Default Stereo FM: Use center oscillator as modulator, outer oscillators as ratios/carriers.
Phase Modulation: Center oscillator can receive phase mod from both outer oscillators, patched or normalized.
Cross Modulation: Patch outer phase or FM ins to opposite outs for wild textures.
Ratio Tracking: Outer oscillators in RATIO track to center osc, creating classic DX-style FM when modulating index/depth.
SYNC: Feed external clock/signal to SYNC for hard sync (FREE) or ratio tracking (RATIO).

Internal Normalization

Input	Normalized From
Center PHASE (1/2)	Outer oscillators' SINE outs
Outer FM (L/R)	Center SINE / COSINE out
Outer PHASE (L<->R)	Opposite SINE out
Outer RATIO SYNC	Tracks center if nothing patched

Power Draw

+12V: 95mA
-12V: 50mA
Inrush: 200mA on +12V at power up

Back Panel Header Functions

Name	Function
Expander	Unused (future)
PLL Mode	On = Phase lock for external tracking (useful for LFO/oscilloscope)
Ext. Filter	Switches noise filtering for OSC1,3 PHASE & OSC2 FM (Low/High)
Sq. Phase	Remove phase mod from square out for pure/sub recovery
Phase Dir	Same direction for all outs (preserves phase relationship)

Calibration

All units pre-calibrated; calibrate only if necessary (unlikely).
Use back-panel buttons, 0V and 4V source, follow manual.

Quick Reference -- Basic Patch Ideas

Unmodulated Ratio FM: Center FREE/HIGH, right RATIO, mult/div to tune harmonics.
Classic PM: Center SINE/COSINE outs, phase index up, cross modulate outers for rich stereo.
Dub Bass: Seq clock into left SYNC in ratio mode, mod input to left RATIO, monitor center out.
Rhythmic Creaks: Center FREE, LOW; outer RATIO or FREE, lots of phase index and cross mod.

More Info

Schlappi Engineering - Three Body Page

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