Click the button at the bottom of the screen to reference the faceplate layout.

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  1. Introduction
  2. Controls and I/O
  3. Parameters
    1. RATIO
    2. II/III CV
1. Introduction

SYNC3 generates a trio of clock-synced oscillators (frequency synthesizers), each of which operate at an independent frequency ratio of the master clock frequency. It can gracefully sync to the frequency and phase of clocks as slow as a half-minute or as fast as 20kHz.

If you pull a blank at the phrase "frequency ratio", imagine patching a clock into a divider, then taking the output of the divider into a multiplier. The frequency of the output at the multiplier would have a "ratio relationship" with your initial clock. The "denominator" of the frequency ratio would be the divider amount, and the "numerator" would be the multiplier amount.

You find frequency ratios throughout music. 3/2 is a perfect fifth as well as the ratio of a quarter note triplet to a regular quarter note. 6/5 is a decent approximation of a minor third and a very strange polyrhythm. The harmonic spectrum of traditional waveforms is built around frequency multiplication.

Oscillator I has an independent output with a fixed level, while the other two are mixed together, each having an input controlling level (or accepting amplitude modulation). You can use the two outputs completely independently, or you can combine the oscillators with self-patching, giving you access to complex waveforms with a fundamentally harmonic or rhythmic character.

2. Controls and IO

If you haven't yet, take a glance at this introduction of Via's controls, IO, and user interface.


Each knob selects a frequency ratio for an oscillator as indicated on the silkscreen. The knob spans a range of 16 ratios as selected by the RATIO parameter.

A clockwise turn increases oscillator frequency.


By default, the CV offsets the ratio as selected by the corresponding knobs, with positive voltages increasing the oscillator frequency (like a clockwise turn of the knob) and negative voltages decreasing it (like a counterclockwise turn).

With no active CV, you can set an oscillator frequency to 1:1 by turning the knob to noon. When the knob as is at either extreme, the CV can be used to access 8 additional ratios rather than clamping.

See II/III CV for more information on the alternate phase modulation configuration.

Logic Input

SYNC is the main input on the module. It tracks the frequency and phase of the rising zero crossings of the input frequency, driving the internal oscillators. Using a simple waveform or pulse input will provide the smoothest output, but complex signals can create pleasant glitchiness as the oscillators try to keep up with an irregular clock.

When the S+H input is pulled high, the level controls and CV for oscillators II and III are sampled. They are passed when the input is low.


The oscillator I appears at the I output with a range of -5.3V to 5.3V.

The other two oscillators (II and III) are sent to the control inputs of the VCAs in the core Via circuit. As such, the level knobs and CV act as attenuverters for each operator, with the operator always unipolar. By mixing a fully on and fully inverted pair of operators, you can achieve a -5 - 5V output at OSC II+III output. You can control the levels with CV, but note that your control signal may bleed into the output. To achieve VCA-like control, patch the same envelope into both inputs and turn the 3 scale knob fully counterclockwise. Bleed will be minimized.

The R DELTA_TRIGGER output emits a pulse whenever one of the ratios has changed on a clock cycle. The pulse length is set by the clock input gate length.

The SUB output emits a square wave at half the frequency of the clock input (a suboctave square). It is well-suited for audio use as it is virtually free of time distortion (aliasing) through the audible range.

LED Display

The selected RATIO is represented by a color on the RGB triangle.

The top left LED is illuminated when the II and III level inputs are being sampled

The top right LED flashes with the pulse at the R DELTA_TRIGGER output.

The bottom left LED is on while the clock input is high.

The bottom right LED is on when the III CV is configured for phase modulation.

3. Parameters

The waveform of each oscillator can be set independently with the corresponding sensor. The options are:

  1. RAMP
  3. TRI


Musically related selections of ratios are arranged into "rows" that ascend in frequency with a clockwise turn of the knob or increase in control voltage. When the knob is set to noon and the CV is at ground, the oscillator frequency is a 1/1 match of the input clock.

When clocking SYNC at control rate, the ratios feel like different LFO speeds. At audio rate, simple ratios sound like overtones and complex ratios sound lke microtonal intervals.

The RATIO parameter allows you to select a row of ratios that is well suited to a particular use case. Each row is paired with a phase locking algorithm to further tailor the artifact created with a ratio or clock range. The choices are as follows:

  1. Rhythms - The chosen ratios create common rhythms with a half-note clock.
  2. Integers - The ratios are integer divisions of the input clock on the left side of the knob and multiplications on the right side.
  3. Octaves and Fifths - The ratios create octaves and fifths of the root pitch. This is ideal for creating arpeggios from sequenced tonal pitches at the clock input.
  4. Circle of Fifths - The ratios include an extension of the circle of fifths up and down from the root along with octaves of the root.
  5. Major Arp - Just-intoned approximations of a major arpeggio against the root.
  6. Minor Arp - Just-intoned approximations of a minor arpeggio against the root
  7. Microtonal - A selection of just-intoned pitches that balance dissonant and consonant intervals.
  8. Bohlen Pierce - The ratios are only comprised of odd numbers. Instant unsettling ambiance.


There are two possible mappings for the II CV and III CV inputs.

  1. Ratios - The CV inputs are mapped to the ratio selection for the respective oscillators as described in the CV section.
  2. Phase - II CV is mapped to the ratio selection for both oscillators II and III. III CV modulates the phase of both equally. Note that oscillator I is unaffected by the phase input.

Each of these options has highly compelling use cases. For example mode 1 (ratios) can be used to animate complex waveforms at the II+III output by modulating the two ratios with different sources. Mode 2 (phase) can produce highly sonorous audio rate modulation tones when the clock or the oscillator I output is patched into III CV (the phase modulation input).

The legending on the expander helps you remember which CV is assigned to which function, and the bottom right LED is lit when phase modulation is enabled.