Eurorack is a format for modular synthesisers. It was designed by Dieter Doepfer for his A-100, first released in 1995, as a cheaper variation of the Eurocard format used by the rather more obscure Elektor Formant.
Physically, Eurorack modules are 3U (133.4 mm) high, and multiples of 1 HP (horizontal pitch — 5.08 mm) across. Almost all are multiples of 2 HP (10.16 mm). An 84 HP subrack fits neatly into a 19" rack.
In contrast to Eurocard requiring all PCBs to be elongated to a consistent depth, Eurorack allows shallower and cheaper PCBs of varying depths by using cables to connect them. Arguably Doepfer's only fault here was the omission of keyed headers (little bits of plastic that go around the bus's connectors, with a notch on only one side, lining up with small plastic protrusions on the corresponding modules' connectors), as many users would rather pay a little extra to guarantee they don't accidentally plug a module's connector in upside down, permanently breaking it.
Eurorack carries CV and gate signals on its bus, likely influenced by the Roland System-100M.
Within a few years, the Eurorack format was adopted by Analogue Systems and Analogue Solutions over in the UK. It surely helped that it was compact, relatively affordable, and let you repurpose factory-built Eurocard subracks and front panels.
In 2004, Doepfer published the A-100's specifications on the Web, allowing other companies to much more easily embrace the format. Also around this time, the shop Analogue Haven started importing and selling Eurorack format modules in California.
It seems that free access to the specification, and in the case of the US, a single shop selling different companies' compatible modules, was just what everyone needed. By 2006, Analogue Haven was selling imported Eurorack modules by Doepfer and Analogue Solutions alongside local ones by Bananalogue, Livewire Electronics, and Plan B.
Many musicians and engineers formed small companies to make a handful of Eurorack modules each. This culminated in a niche yet global cottage industry, catering to experimental musicians worldwide, until the recession of the 2020s. At its height, Eurorack was even used by Moog and Roland, coming full circle.
The 3HE-Format I used for the front plates and frames was an industrial standard in those days. I came across it all the time when I was working on my physics thesis. I used the format with the early VMS and re-activated it with the A-100 modular. But although the frame remained the same, I changed the interior concept. In the A-100, I replaced those ridiculously expensive bus boards and inflexible circuit board sizes used by the industry with a less expensive and more flexible bus / circuit board system. That allows the circuit board size to vary from module to module. You don't have to use — and pay for — full-size circuit boards all the time, just when you really need them.
— Dieter Doepfer, 2013
- "A Visit to the Musikmesse in Frankfurt" Stefan Gruhl, Analogue Heaven, Mar 1995
- "More About the Musikmesse" Stefan Gruhl, Analogue Heaven, Mar 1995
- "Doepfer A-100 Review *** Part One" Sean Coppinger, Analogue Heaven, Dec 1995
- "Dieter Doepfer — Creator of the A-100 Modular System" Theo Bloderer, Oct 2013
- "Mod-U-Like" Chris Carter, Sound On Sound, Jun 1998
- "Drums & Wires" Gordon Reid, Sound On Sound, Sep 1999
- "A-100 DIY Page" Nov 2004
- "What Do We Sell?" 2006
- "Bananalogue" 2005
- "Livewire Electronics" 2006
- "Welcome to Electro-Acoustic Research" Nov 2006
19 inch rack: Eurorack