What Is Eurorack?

Eurorack is the most popular format for modular synthesizers — a shared standard for the physical size, connectors and power of synth modules so that gear from different brands fits and works together in one case. Originated by Doepfer in the mid-1990s, it has grown into an ecosystem of hundreds of makers, from Make Noise and Mutable Instruments to Intellijel, 4ms and Behringer.

If you are asking what is Eurorack, think of it as the LEGO standard of modular synths: a set of agreed dimensions that lets you mix and match modules into a custom instrument.

What makes a module “Eurorack”

Eurorack defines three practical things so that modules are interchangeable:

• Height (3U): modules are a standard panel height, roughly 128.5 mm, often called 3U. This is why a tiny utility and a big oscillator line up neatly in the same row.
• Width (HP): width is measured in HP (horizontal pitch). One HP is about 5.08 mm. A skinny module might be 4HP; a large one might be 20HP or more. HP is how you budget space in a case.
• Power connector: modules connect to a power bus with a 10-pin or 16-pin ribbon cable carrying standard voltages.

Because these are fixed, a Make Noise oscillator and a Doepfer filter can sit side by side and patch together with the same cables.

Signals: audio and CV at the same level

Eurorack uses 3.5 mm (1/8″) patch cables, and crucially it treats audio and control voltage the same way electrically. That means you can patch an oscillator into a filter (audio) or an LFO into that filter’s cutoff (control voltage) using identical cables. Pitch typically follows a 1 volt per octave standard, and timing is handled by gate and trigger signals. If that is new to you, our guides on CV and gate and VCO, VCF and VCA explain the signal types behind every patch.

Power: the part beginners overlook

Every Eurorack module needs power delivered over that ribbon cable, usually +12V, -12V and sometimes +5V rails. Your case provides this through a power supply and one or more bus boards. Two numbers matter: how much current (in milliamps) your modules draw on each rail, and how much your supply can deliver. Always leave headroom rather than running a supply at its limit. We cover this in depth in our guide to Eurorack power supplies.

Cases and rows

A Eurorack case is a powered enclosure measured in HP of width and rows of height. A small skiff might hold a single row of 60–84HP; larger cases stack multiple rows. Case makers such as Tiptop, Intellijel and Doepfer build enclosures with power already integrated, which is the simplest path for a first system. Our roundup of the best Eurorack cases walks through sizing and what to look for.

Why Eurorack became the standard

Several factors made Eurorack dominate over larger formats like 5U:

• Compact size means more functionality per case and lower shipping and material costs.
• An open standard let small builders enter, so innovation and variety exploded.
• Cross-brand compatibility means you are never locked into one company’s ecosystem.

The trade-off is that smaller knobs and dense panels can feel fiddly compared with a full-size 5U system, but most people accept that for the sheer range of available modules.

Getting started with Eurorack

You do not need a giant rig to begin. A modest case, a power supply, an oscillator, a filter, an envelope, a VCA and a way to sequence or play notes will make music. For a planned approach, read how to start a Eurorack system and our list of essential Eurorack modules. If you would rather ease in, a semi-modular like the Moog Mother-32 is Eurorack-compatible and works standalone too.

Frequently asked questions

Is Eurorack the same as modular?

Not exactly. Modular is the broad concept of building a synth from separate modules. Eurorack is one specific modular format — by far the most popular today — that standardises size, cables and power. Other formats like 5U and Buchla-style systems also exist.

Can I mix brands in one Eurorack case?

Yes, that is the whole point. Any module built to the Eurorack standard fits the same case and patches with the same 3.5 mm cables, so you can combine Make Noise, Mutable Instruments, Intellijel, Doepfer and others freely, as long as your power supply has enough headroom.

Do I need to know electronics to use Eurorack?

No. You patch with cables and turn knobs — no soldering or circuit knowledge required to play. You only need to understand power budgeting (current per rail) when planning a case, which is straightforward arithmetic.