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.
One detail that trips up newcomers is the orientation of the ribbon cable. The red stripe marks the -12V edge of the connector and must line up with the matching marking on both the module and the bus board. Plugging a module in backwards can damage it, so it is worth checking twice before you power on a freshly built row. Modern modules increasingly use keyed 16-pin connectors that make this harder to get wrong, but plenty of older and boutique modules still rely on you reading the stripe.
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.
How to choose your first modules
The temptation when starting out is to buy whatever looks exciting, but a small system that can actually make a complete sound will teach you far more than a pile of mismatched modules. A classic starting voice covers four jobs: a sound source, a way to shape its tone, a way to shape its volume over time, and a way to control pitch and rhythm. In practice that means an oscillator, a filter, an envelope feeding a VCA, and a sequencer or keyboard.
When weighing up specific modules, work through a few questions in order:
- What job does it do in my patch? Every module should fill a clear role. If you cannot describe how it connects to the rest of your system, you are not ready to buy it yet.
- How much space and power does it need? Note the HP width and the current draw on each rail before you commit, then check it against your case budget so you do not run out of room or amps halfway through.
- Is it deep or is it a one-trick module? Utilities such as mults, attenuators, mixers and offsets are unglamorous but get used in almost every patch. Beginners tend to under-buy these and over-buy big feature modules.
- Does it play nicely with what I own? Check that levels and signal types match — some modules expect audio-level signals, others CV, and a little attenuation often bridges the gap.
If you would rather ease in before committing to a fully patchable case, a semi-modular like the Moog Mother-32 is Eurorack-compatible and works standalone too, which lets you learn the workflow with a known-good signal path. For a planned approach, read how to start a Eurorack system and our list of essential Eurorack modules.
Common beginner mistakes
A few patterns come up again and again, and avoiding them will save you money and frustration:
- Ignoring the power budget. Adding modules until the supply browns out causes tuning drift, glitches and crashes that are hard to diagnose. Tally your current draw and leave headroom from the start.
- Skipping utilities. Without enough mults, attenuators and mixers, you will quickly find you cannot route or scale signals the way a patch needs, no matter how nice your oscillators are.
- Buying the biggest case first. A large empty case is expensive to fill and easy to over-commit to. Many people are happier starting with a small skiff and growing once they know their own taste.
- Chasing complex modules too early. A deep, menu-driven module can be powerful, but learning the fundamentals on simple, knob-per-function modules builds the intuition that makes the complex ones useful later.
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.
How much does a starter Eurorack system cost?
There is no fixed figure, because it depends entirely on the modules and case you choose, but the cost adds up faster than most people expect once you include the case, power, patch cables and a complete signal path. The most budget-friendly route is usually a small case plus a semi-modular or a handful of multi-function modules, then expanding gradually as your needs become clear rather than buying a large system all at once.
