Doepfer published the A-100 specs for free and Eurorack became the synth standard

In the mid-1990s, modular synthesizers were museum pieces: the classic Moog and Buchla systems were huge, expensive, and long out of production, and digital synths dominated the market. After the success of his MS-404 monosynth, Dieter Doepfer saw a chance to 'raise the modular synth from the dead' and designed the A-100 system — its first modules little more than MS-404 circuits repackaged — in a compact 3U rack format based on cheap standard Eurocard frames.

The decisive move was openness. Doepfer published the complete technical and mechanical details of the A-100: module heights and widths, the bus board and ±12V power supply, and the signal standards (1V/octave pitch CV, gate levels, 10Vpp audio). Anyone could download the specs and manufacture compatible modules with no license fee, no approval process, and no permission from Doepfer.

Small manufacturers adopted the format in waves. Doepfer told Ableton in 2015 that there were already 'a hundred manufacturers with a thousand modules,' and the scene has only grown since. Two decades after launch the format — now simply called Eurorack — dominates modular synthesis, with Doepfer's own modules still selling as the ecosystem's standard building blocks.

publish the spec so cloning beats competing

A free, complete spec removed every barrier to entry, so hundreds of tiny makers could join without negotiating with Doepfer.

The small, cheap 3U format lowered costs for both builders and buyers compared with vintage full-size modulars.

Interoperability made each new module more valuable: exotic third-party modules still needed Doepfer's standard utility modules to work.

Doepfer never had to defend a proprietary format — cloners strengthened the standard instead of fragmenting it.

Publish your format's spec so completely that building for it is easier than competing with it; an open spec turns potential rivals into ecosystem partners.

Eurorack grew into the dominant modular format worldwide, with hundreds of manufacturers and thousands of modules; by the 2010s even established synth brands like Moog, Dave Smith and Waldorf released Eurorack-compatible products. Doepfer's A-100 line remains in production decades later, and Dieter Doepfer is known as the 'founding father of Eurorack.'