Modular Glossary

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Modular synthesis comes with a lot of jargon. This glossary explains the words you'll meet in manuals, build guides, forums and on our own pages, in plain language. Click a letter to jump.

New to modular? Start with Getting Started with Modular Synthesizers, then come back here whenever you hit a word you don't know.

1–5

1U
A thin extra row for small utility modules. There are two incompatible 1U formats (Intellijel and Pulp Logic tiles). See Building a Eurorack Case.
1V/octave
The pitch standard in Eurorack: one volt more control voltage makes the oscillator play one octave higher. A good VCO "tracks" this accurately over several octaves.
3U
The height of a Eurorack module: 128.5 mm. All Eurorack modules are 3U high; only the width (HP) differs.
5U
A larger modular format (Moog-style, also called MU or Dotcom), with modules about 22 cm high. Not compatible with Eurorack.

A

ADSR
Attack, Decay, Sustain, Release: the four stages of the classic envelope.
Attenuator
A knob that turns a signal down, from full level to zero. Used to set how much a CV modulates something.
Attenuverter
An attenuator that can also invert the signal: the middle position is zero, turning left gives an upside-down signal.
Audio rate
A signal fast enough to hear (roughly 20 Hz to 20 kHz). Modulating at audio rate gives FM-like, metallic sounds.

B

Banana jack
The 4 mm connectors used by Buchla and Serge-style systems instead of 3.5 mm jacks.
Bipolar
A signal that goes both above and below 0V, for example an LFO from −5V to +5V. Compare unipolar.
BOM
Bill of Materials: the parts list of a DIY project. See BOM: The Bill of Materials.
Box header
The shrouded power connector on a module or bus board, with a notch so the cable only fits one way. We sell 10-pin and 16-pin versions.
Buchla / West Coast
A style of synthesis named after Don Buchla: complex oscillators, wavefolding and low-pass gates instead of the classic oscillator-filter-amp chain. Compare East Coast.
Bus board
The board in your case that distributes power to all modules. See our bus boards and Powering Your Case.

C

Clock
A steady stream of pulses that keeps sequencers, drum modules and delays in time.
Clock divider
A module that turns one clock into slower ones: every 2nd, 3rd, 4th pulse and so on.
Comparator
A circuit that outputs a gate when an input goes above a set level. Turns any CV into rhythm.
CV (control voltage)
A voltage that controls something: pitch, filter cutoff, volume, speed. The core idea of modular synthesis. See Patching Techniques.

D

DAC
Digital-to-analog converter: turns numbers from a microcontroller into a CV or audio signal.
Decoupling capacitor
A small capacitor (usually 100 nF) next to the power pins of each chip, to keep its supply clean. See Electronic Components Explained.
DIY kit
A module you build yourself from a PCB, panel and parts. See Your First DIY Module Build.

E

East Coast
Classic subtractive synthesis in the style of Moog: a bright oscillator through a filter and an amplifier.
Envelope (EG)
A CV shape triggered by a gate, used to shape the volume or brightness of each note over time. The most common is the ADSR.
Eurorack
The most popular modular format, started by Doepfer in 1996: 3U high, width in HP, 3.5 mm jacks, ±12V power. See Modular Synth Companies.
Expander
An extra module that adds features to another module, connected with a small cable behind the panel.
Exponential converter (expo)
The circuit inside an analog VCO that turns 1V/octave into the right frequency. Usually built with a matched transistor pair.

F

Filter (VCF)
Removes part of the sound's frequencies. A low-pass filter makes a sound darker; with resonance it gets a sharp, whistling peak.
Firmware
The software inside a digital module. See Flashing Firmware: STM32 and AVR.
Footprint
The pads and holes on a PCB for one part. See SMD parts: sizes and footprints.

G

Gate
An on/off signal, usually 0V or 5–10V, that stays high as long as a key is held. Compare trigger.
GND (ground)
The 0V reference that all voltages are measured against. See Powering Your Case.

H

HP
Horizontal Pitch: the width unit of Eurorack, 5.08 mm. A 10 HP module is about 5 cm wide; cases are often 84 or 104 HP wide. Our Eurorack rails come in several HP sizes.

I

IC socket
A holder for a chip, so you can swap it without desoldering. See our IC sockets.
IDC connector
The connector on a ribbon cable that cuts into the wires when pressed shut. See Make Your Own Eurorack Power Cables.

J

Jack
The 3.5 mm socket on a module where you plug in patch cables. The DIY standard is the WQP518MA.

L

LFO
Low Frequency Oscillator: a slow oscillator used for modulation, like vibrato or a slowly opening filter.
Low-pass gate (LPG)
A combined filter and amplifier, often built with vactrols, that gives a natural, plucked sound when pinged.

M

Mixer
Combines several signals into one, audio or CV.
Modulation
Changing a parameter over time with a CV: the movement that makes a patch come alive.
Mult (multiple)
Copies one signal to several outputs. Passive mults are fine for CV and gates; for 1V/octave pitch a buffered mult is more accurate.

N

Normalling
A hidden default connection inside a module that works until you plug in a cable. For example: the second VCA input listens to the first one when nothing is plugged in.

O

Offset
A fixed voltage added to a signal, to shift it up or down.
Op-amp
The workhorse chip of analog synths (for example the TL072). See Electronic Components Explained.
Oscillator
Makes a repeating waveform: sine, triangle, saw or square. See VCO and LFO.

P

Patch
A set of connections between modules, and the sound it makes. See Patching Techniques.
Patch cable
A short cable with 3.5 mm plugs on both ends. We sell straight and right-angled ones.
Pinging
Sending a short trigger into a resonant filter or low-pass gate so it rings like a struck drum or bell.
Power cable
The flat ribbon cable between a module and the bus board. See Make Your Own Eurorack Power Cables.

Q

Quantizer
Rounds a CV to the nearest note of a chosen scale, so random voltages become melodies.

R

Rails
Two meanings: the metal mounting rails that modules screw into, and the power rails (+12V, −12V and +5V) on the bus board.
Ribbon cable
Flat multi-wire cable, used for Eurorack power cables. See our DIY ribbon cables.

S

Sample & Hold (S&H)
Takes a snapshot of a voltage on each trigger and holds it. With noise as input you get the classic random stepped sound.
Self-patching
Patching a module's output back into its own input, often for wild results.
Sequencer
Plays a series of CVs and gates in time with a clock: the melody or rhythm of your patch.
Skiff
A shallow, portable case, often one row. Not every module is shallow enough to fit. See Building a Eurorack Case.
Slew limiter
Smooths jumps in a CV into slides: portamento (glide) on a melody, or a smoother random signal.
SMD
Surface-mount device: tiny parts soldered onto pads on the surface of the PCB. Compare through-hole.

T

Thonkiconn
Popular nickname for the small 3.5 mm PCB jacks used in DIY Eurorack, after the shop Thonk. Today's original part is the QingPu WQP518MA.
Threaded strips
Strips with M3 threads that slide into the rails, so you can screw modules in anywhere. See threaded strips and sliding nuts.
Through-hole
Parts with legs that go through holes in the PCB. Easier to solder by hand than SMD.
Trigger
A very short pulse that starts something: an envelope, a drum sound, a sequencer step. Compare gate.
Trimmer
A small potentiometer on the PCB, set once with a screwdriver for calibration. See our trim pots.

U

Unipolar
A signal that only goes from 0V up (for example 0–8V). Compare bipolar.
Utility module
A small helper module: mults, attenuators, mixers, offsets, logic. Not exciting on its own, but you can never have enough.

V

Vactrol
An LED and a light-dependent resistor in one sealed package, giving smooth, natural responses in low-pass gates and compressors.
VCA
Voltage-Controlled Amplifier: sets the volume of a signal with a CV, usually from an envelope.
VCF
Voltage-Controlled Filter. See filter.
VCO
Voltage-Controlled Oscillator: the sound source whose pitch follows 1V/octave.
VCV Rack
Free software that simulates a Eurorack system on your computer. See VCV Rack: Free Virtual Modular.

W

Wavefolder
Folds the peaks of a waveform back on themselves, adding bright harmonics. A key part of West Coast sound.
West Coast
See Buchla / West Coast.

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