CV/Gate explained: control voltage for synth players
1 V/octave, Hz/V, gate, trigger, S-trig: what a CV/Gate cable carries, the voltages to know and how to hook an analog synth up to a MIDI keyboard or a DAW.
On a modular, a semi-modular or a pre-MIDI analog synth, notes and modulation do not travel as digital messages but as electrical voltages. That is the idea behind CV/Gate: a control voltage (CV) says what to play, a gate says when and for how long. Understanding these two signals is enough to patch your first sound, connect a sequencer to a synth or drive an analog instrument from a DAW.
Control voltage: pitch and everything else
A CV cable carries a slowly changing DC voltage, and that voltage drives a parameter: the pitch of an oscillator (VCO), the cutoff of a filter (VCF), the level of an amplifier (VCA). The “VC” in those three acronyms stands for voltage controlled. An envelope or an LFO is nothing more than a voltage that changes over time.
The 1 V/octave standard
The most common standard, and the Eurorack one, is 1 V/octave: each extra volt raises the note by one octave, so a semitone is 1/12 of a volt, roughly 83 mV. As the Doepfer A-100 technical documentation points out, the voltage is relative: +1 V does not mean a specific note, the oscillator’s tuning sets the starting point.
The Hz/V exception
Some 1970s and 1980s synths, including the Korg MS-10 and MS-20 and several Yamaha CS-series models, follow a different rule: Hz/V, where frequency doubles when voltage doubles. Plugged straight into a 1 V/octave output, such a synth goes out of tune as soon as you move away from the starting note. You need a converter that supports this mode, or a dedicated conversion module.
Gate, trigger, clock: the timing signals
A gate is an on/off signal. While the key is held it stays high, typically at +5 V; on release it drops back to 0 V. It starts the attack stage of an envelope and decides when the release stage begins (see our ADSR envelope explainer).
- Gate: a pulse whose length matters, the length of the held note.
- Trigger: a very short pulse that only marks a moment (a drum hit, the start of an envelope).
- Clock: a steady stream of pulses that sets the tempo of a sequencer or arpeggiator.
On thresholds, Doepfer states that an input treats anything above about +3 V as “high” and anything below 1 V as “low”. A slowly rising waveform, such as a triangle LFO, is therefore a poor trigger source.
The S-trig trap
Vintage Moogs, and the Korg MS-20, do not use a positive voltage but an S-trig (short-circuit trigger): the note fires when the contact is shorted to ground. It is the logical opposite of a standard gate, known as V-trig. Feeding a Eurorack gate into an S-trig input makes notes fire on release: an S-trig to V-trig adapter, or a converter that offers both, solves it.
The voltage levels to know
Typical values in a Eurorack system, according to the Doepfer documentation:
| Signal | Typical range | Job |
|---|---|---|
| Audio | 10 V peak to peak (−5 V to +5 V) | the sound itself |
| LFO | −2.5 V to +2.5 V | cyclic modulation (vibrato, filter sweeps) |
| Envelope | 0 V to +8 V | the shape of the sound over time |
| Gate, trigger, clock | 0 V / +5 V (high above about +3 V) | triggering and tempo |
| Pitch CV | 1 V per octave | note pitch |
These levels are hotter than standard studio gear: a Eurorack output plugged into a mixer’s line input clips easily. And a converter whose pitch output tops out at 5 V only covers five octaves.
Connectors: 3.5 mm, 6.35 mm or banana plugs
Eurorack uses 3.5 mm mono jacks, linked with patch cables. Larger formats and many older synths use 6.35 mm (1/4 inch) jacks, while Buchla and Serge systems use banana plugs. An adapter cable is all it takes to cross formats, as long as the voltages are compatible. For the format itself, its rails and its power, see our Eurorack and first case guide.
Connecting a CV/Gate synth to MIDI or a DAW
Three options, depending on the gear you already own:
- A MIDI-to-CV converter, standalone or as a Eurorack module: it turns MIDI notes into pitch CV and gate, and often velocity, mod wheel or MIDI controllers into extra voltages. It is the simplest way to play a modular from a keyboard.
- A hardware sequencer with CV/Gate outputs: many recent sequencers and semi-modulars have them built in, no MIDI needed. The models we cover are in the sequencers and control section.
- A DC-coupled audio interface: its outputs pass a steady voltage, so a DAW can send CV the way it sends audio. Bitwig Studio has dedicated CV instruments built in, and Ableton Live does it with the Max for Live CV Tools pack. A standard AC-coupled interface filters out DC and will not work.
Before you buy: four checks
- Pitch standard: 1 V/octave or Hz/V, on both the synth and the converter.
- Trigger type: V-trig (positive gate) or S-trig.
- Voltage range: 0–5 V or 0–10 V on the pitch output, which sets how many octaves you can play.
- Number of outputs: one pitch/gate pair per voice, plus modulation outputs if you want to pass on velocity and controllers.
If you are new to synthesis and still torn between a modular and an all-in-one instrument, our first synth guide will help you decide. Our other hookup guides are in the setup and connectivity section.