LMNC could have used MOTM or one of the other larger formats, but chose to create something new. He was building his own modules and had access to 20 cm wide sheet aluminum for panels, so chose that as the height. Staying metric, he made the widths multiples of 5 cm. He liked 1/4" patch cords better than 3.5 mm so used 1/4" jacks. For ease of interoperability with Eurorack and adaptation of Eurorack circuit designs, he kept Eurorack’s electrical standards, more or less. Eurorack power voltages are ±12 V and +5 V, connected via 16-conductor ribbon cables to 16-pin headers, or one can use 10-conductor cables and 10-pin headers to get only ±12 V. In modern Eurorack module design 10-pin headers and non-use of the 5 V rail is nearly ubiquitous. In Kosmo only the 10-pin power header option is specified — there is no 5 V rail. Aside from that, Kosmo uses the same supply voltages and compatible signal voltages and widths as Eurorack.

Essentially Kosmo is just jumbo-size Eurorack.

Part of a case containing a row of Kosmo modules on the top and another on the bottom, with a row of Eurorack modules above the bottom. Between that and the top Kosmo row is a full-width jumbler panel.

Kosmo (top and bottom) and Eurorack (lower middle) modules

Kosmo continues to be largely a DIY (Do It Yourself) format, and if you are doing it yourself you can choose to vary or disregard standards chosen by other people, but for the most part Kosmo builders adhere to these choices. (At least one builds his Kosmo modules with 3.5 mm jacks, though. His synth, his rules.) There are more detailed specifications shown here , though compliance with some of them varies.

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