sto

Make Noise STO

Compact analog VCO built for melody and sub-timbral depth

8 HP Eurorack module

The STO (Sub-Timbral Oscillator) is a compact 100% analog voltage controlled oscillator built around a triangle core, producing Sine, Variable Shape, and Sub-Oscillator outputs. It is designed for melody, bass, and harmonically rich textures through Hard Sync, Linear FM, and a unique Variable Shape circuit that ripples even and odd harmonics while always maintaining a strong fundamental. Its musical character is warm and melodic, sitting in contrast to more complex oscillators, making it ideal for basslines, lead sequences, and rich timbral voices.

Features

  • 100% analog triangle core VCO
  • Sine waveform output (10Vpp) shaped from triangle core using same circuit as DPO
  • Variable Shape waveform output (10Vpp) derived from Sine, ripples even and odd harmonics while maintaining strong fundamental
  • Sub-Oscillator output (12Vpp) one octave below main frequency, rectangular shape derived from comparator
  • S-Gate input resets and toggles Sub-Oscillator on and off independently from other outputs
  • Hard Sync input resets oscillator core, compatible with approximately any 10Vpp audio rate signal
  • Linear FM input (AC coupled, 10V range) with unipolar attenuator
  • Exponential FM possible via Expo CV input (no built-in attenuator)
  • 1V/Octave input for standard pitch tracking from sequencer, keyboard, or MIDI-CV
  • Expo CV input for additional CV control, transposition, or exponential FM
  • Variable Shape CV input (direct coupled, unipolar 0V to +8V) with panel control acting as attenuator when CV is patched
  • Coarse Tune spanning 9 octave range (8Hz to 4kHz)

Controls & Jacks (20)

  • Sub-Oscillator Output— Stepped rectangular waveform output one octave below the main oscillator. Approximately 12Vpp, bi-polar.
  • Variable Shape Waveform Output— Primary audio output with variable harmonic content. Morphs from sine to glitched triangle via the Variable Shape knob. 10Vpp, bi-polar.
  • Sine Waveform Output— Pure sine wave output derived from the triangle core. Minimal harmonic content, ideal for reinforcing fundamentals or clean FM patches. 10Vp
  • Saw Output— Sawtooth waveform output derived from the triangle core. 10Vpp, bi-polar.
  • Coarse Tune panel control— Sets the base frequency of the oscillator across a 9-octave range, from approximately 8Hz to 4kHz.
  • Fine Tune panel control— Fine pitch adjustment within +/- 2.5 semitones of the Coarse Tune setting. Use for precise tuning against other oscillators.
  • Scale Trimmer— Internal calibration trimmer for adjusting 1V/Oct tracking accuracy. Factory-set; do not adjust during performance.
  • SIN— Selects the sine waveform variant for the Variable Shape output circuit.
  • Linear FM Level— Uni-polar attenuator for the Linear FM input signal.
  • Linear FM Input— AC-coupled linear frequency modulation input. Accepts audio-rate signals with a 10V range.
  • SHAPE— CV input for external control of the Variable Shape waveshaping circuit. Unipolar, 0V to +8V range.
  • Variable Shape— Controls the harmonic content by rippling even and odd harmonics. Works as a standard panel control when nothing is patched to the Variable
  • Sync Input— Resets the oscillator core for hard synchronization. Accepts just about any 10Vpp audio-rate signal.
  • Shape CV— Hard sync input. Resets the oscillator core on each incoming cycle, forcing STO to lock to the external signal period. Accepts ~10Vpp audio-
  • Variable Shape CV Input— Direct-coupled unipolar control signal input for Variable Shape modulation. Range 0V to +8V.
  • S-Gate Input— Sub-Oscillator gate input. Turns the Sub-Oscillator ON at gate high and OFF at gate low.
  • Expo Input— Exponential frequency control input for pitch modulation, transposition, or exponential FM. Bi-polar, 10V range.
  • 1V/Oct Input— 1 volt-per-octave pitch tracking input for sequencers, keyboards, or MIDI-CV converters. Bi-polar, +/-5V range.
  • S-Gate Output— Sub-Oscillator gate input. Turns the Sub-Oscillator ON at gate high and OFF at gate low.
  • FM2 Input— Secondary frequency modulation input. Accepts audio-rate or CV signals for additional FM layering.

How-To Guides

  • The Sub Timbral Voice
  • Analog Bass Drum
  • Transposition and Superimposition
  • Dual Sync
  • Key Tracking Harmonics
  • Rhythmic Bassline via S-Gate
  • Exponential FM Percussion
  • Sync Harmonic Sweep
  • Linear FM Overdrive Texture
  • Sine Fundamental Reinforcement

Explore the interactive STO panel on BleepDex — tap any control to learn what it does.

8c571ce