STO

Make Noise 8HP
OSCILLATOR VCO

Verified sheet

The facts on this sheet have been cross-checked against the sources below.

Sources
Suggest a correction

Compact analog VCO. Triangle core with Sine, Variable Shape and Sub outputs. Linear FM, hard SYNC and gateable Sub-Oscillator. Designed as melodic counterpart to the DPO.

Patch Ideas · 7

★ Sub-Timbral melodic voice
Variable Shape → MMG/filter AC in · SUB → MMG DC in · STO FREQ ~12:00 · slow log LFO from MATHS → SHAPE CV, SHAPE knob ~60% · sequencer pitch → 1V/Oct · gate-triggered expo envelope → filter cutoff · rich sine + sub + animated harmonics under envelope control — the classic STO voice.
▸ Show diagram
Patch diagramPatch diagram with 6 modules and 6 connections. Modules: STO, Sequencer, CH 4, Filter, Envelope, Output. Signals: 3 audio, 2 cv, 1 pitch.STOSequencerCH 4FilterEnvelopeOutputFREQ: ~12:00SHAPE: ~60% (as attenuator)1V/Oct1v/octShape CVcvSineaudioSUBaudioPitch1v/octOUTcvAC InaudioDC InaudioCutoffcvOutaudioOutcvInaudio11. slow log LFOaudiocvpitch
Analog bass drum
Sine → Optomix CH 1 signal in · gate → STO Linear FM In AND Optomix CH 1 STRIKE · LIN ~12:00 · FREQ ~9:00 · Optomix DAMP and CONTROL full CCW · monitor Optomix CH 1 out · short FM burst on each gate gives analog kick. Modulate LIN amount or add Expo FM from another VCO for kick variants.
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 4 connections. Modules: STO, Gate Source, CH 1, Output. Signals: 2 audio, 2 gate.STOGate SourceCH 1OutputFREQ: ~9:00LIN: ~12:00LINgateSineaudioGategateStrikegateSignal InaudioOutaudioInaudio11. kickaudiogate
Transposition / superimposition
Main sequence → 1V/Oct · second sequence (odd clock division of master) → EXPO · the two sequences add for variable transposition. Alternatively derive transposer from main sequence via S&H for structural variation · or tune a square LFO to ±1V for double-octave leaps.
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 3 connections. Modules: STO, Sequencer A, Sequencer B, Output. Signals: 1 audio, 2 pitch.STOSequencer ASequencer BOutputFREQ: to taste1V/Oct1v/octEXPO1v/octVariable SHAPEaudioPitch1v/octPitch1v/octInaudio11. added — transposes mainaudiopitch
Dual SYNC (split Sub from main)
Audio-rate square → S-Gate · different audio-rate square → SYNC · Sub pseudo-syncs to S-Gate source while Sine/Shape hard-sync to the SYNC source · gives two related-but-independent harmonic layers from one STO. Try DPO VCO A saw into S-Gate and VCO B square into SYNC with Follow engaged.
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 4 connections. Modules: STO, VCO A, VCO B, Mixer. Signals: 4 audio.STOVCO AVCO BMixerFREQ: higher than sync sourcesS-GateaudioSYNCaudioVariable SHAPEaudioSUBaudioSquareaudioSquareaudioInaudio121. pseudo-syncs Sub2. hard-syncs Sine/Shapeaudio
Key-tracking Variable Shape
Mult 1V/Oct pitch CV to SHAPE CV In · Variable Shape → output · higher pitches get more harmonic content, mimicking filter key-tracking without a filter · pair with sequencer for a bright top-end that scales with pitch.
▸ Show diagram
Patch diagramPatch diagram with 4 modules and 4 connections. Modules: STO, Sequencer, Mult, Output. Signals: 1 audio, 1 cv, 2 pitch.STOSequencerMultOutputSHAPE: ~50% (sets depth)1V/Oct1v/octShape CVcvVariable SHAPEaudioPitch1v/octIn1v/octOut 11v/octOut 2cvInaudio11. key-tracked harmonicsaudiocvpitch
★ Bassline with gated Sub
Slow square LFO (or cycling MATHS EOC) → S-Gate AND → sequencer clock · sequencer pitch → 1V/Oct · monitor SUB only · Sub turns on/off per clock step creating a note-like pulse without a VCA · adjust LFO pulse width (or MATHS Rise/Fall) to change note length.
▸ Show diagram
Patch diagramPatch diagram with 5 modules and 5 connections. Modules: STO, LFO, Mult, Sequencer, Output. Signals: 1 audio, 1 pitch, 1 gate, 2 clock.STOLFOMultSequencerOutputFREQ: bass rangeSHAPE: irrelevantS-Gategate1V/Oct1v/octSUBaudioSquareclkInclkOut 1clkOut 2gateClkclkPitch1v/octInaudio11. gates Sub per stepaudiopitchgateclock
★ Dynamic Expo FM pings
Sine from another VCO → Optomix CH 1 · Optomix CH 1 out → STO EXPO · gate → Optomix STRIKE · Optomix CONTROL full CCW · each gate opens a short FM burst into EXPO · STO frequency disassembles for percussion accents that decay naturally with vactrol damping.
▸ Show diagram
Patch diagramPatch diagram with 5 modules and 4 connections. Modules: STO, VCO, CH 1, Gate Source, Output. Signals: 2 audio, 1 cv, 1 gate.STOVCOCH 1Gate SourceOutputFREQ: high registerEXPOcvVariable SHAPEaudioSineaudioInaudioStrikegateOutcvGategateInaudio121. dynamic FM2. percussive blipaudiocvgate

Behaviors

Linear FM tracking limit LIN knob past 80%

Linear FM bus overdrives past 80% of LIN attenuator travel and the STO stops tracking 1V/Oct accurately. Keep LIN below 80% for pitched FM, push past for chaotic timbres that abandon pitch.

Gateable Sub-Oscillator gate → S-Gate

Sub output is ON only while S-Gate is high. Rising edge resets Sub. Gives Sub an independent rhythmic layer from Sine/Shape — patch a clock or rhythm gate here for a percussive sub-octave. Narrow audio signals at S-Gate produce sync-like harmonics only in Sub.

Variable Shape morphing SHAPE knob or SHAPE CV In

Ripples both even and odd harmonics while always preserving fundamental. 0%: pure sine. 100%: glitched triangle. Best driven by slow modulation (logarithmic envelopes, smooth random). SHAPE knob auto-converts from value to attenuator when SHAPE CV In is patched.

Hard SYNC on triangle core audio-rate signal → SYNC

STO core restarts on each rising edge of the external VCO. Base frequency locks to external VCO; harmonics emerge when STO frequency is higher than master. Sweep the STO FREQ via EXPO to animate SYNC harmonics. Best with master at 100Hz or higher.

Expo FM via EXPO input audio-rate signal → EXPO

No onboard attenuator — insert a VCA for dynamic/voltage-controlled index. Exponential FM is deeper than Linear but breaks 1V/Oct tracking. Use for percussion or chaos, not pitched leads.

Sub as sub-harmonic layer monitor SUB directly or mix with Sine/Shape

Sub is stepped rectangular, one octave down, tracking all pitch/FM/SYNC inputs. Combining SUB + Variable Shape (at an MMG or Optomix audio mixer) produces the thick melodic voice STO is designed for.

Controls

Global FREQ (Coarse) Coarse tuning knob. Large grey knob.
9 octave range · 8Hz – 4kHz
Global Fine Tune Small trim knob beside FREQ.
±2.5 semitones
FM LIN Unipolar attenuator for Linear FM input.
0% – 100% · overdrives above 80% (tracking fails)
Variable Shape SHAPE Ripples even and odd harmonics while preserving fundamental. Acts as attenuator when SHAPE CV In is patched.
0%: Sine · 100%: glitched triangle
Calibration 1V/Oct Scale Trimmer Internal trimmer. Calibration use only.
factory set

I/O

IN · 6

  • EXPO bipolar · 10V range CV
    Exponential frequency CV. No attenuator — patch a VCA inline for dynamic control.
  • 1V/Oct bipolar · optimal ±5V CV
    Pitch CV input. No attenuator.
  • LIN (FM) 10V range · AC coupled
    AC-coupled Linear FM input. Level set by LIN knob.
  • SYNC ~10Vpp audio rate AUDIO
    Hard sync. Resets oscillator core on rising edge of external VCO. Any 10Vpp audio-rate signal works.
  • SHAPE CV 0V to +8V unipolar CV
    Direct-coupled CV for Variable Shape. SHAPE knob becomes its attenuator when patched.
  • S-Gate >1V gate GATE
    Turns Sub-Oscillator ON at gate high, OFF at gate low. Resets Sub on rising edge. Narrow audio signals can pseudo-sync Sub only.

OUT · 3

  • Variable SHAPE 10Vpp bipolar
    Triangle-core-derived output shaped by SHAPE. Carries FM/SYNC harmonics most aggressively.
  • SUB 12Vpp GATE
    Stepped rectangular sub-oscillator. One octave below Sine/Shape. Affected by EXPO, LIN FM and 1V/Oct; gated by S-Gate.
  • Sine 10Vpp bipolar
    Sine wave derived from triangle core (same shaper circuit as DPO). Low harmonics — ideal FM carrier.