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.
