An old serial-only audio matrix switch turned into a stereo preamp

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The poster's Denon receiver could not record from one tape loop to another, and they also have cassette decks, a reel-to-reel and a Sonos Connect. They found an old Précis DSP 18x18 audio matrix switch with no front panel controls, only a serial port, and set out to turn it into a configurable stereo preamp.

In about four days, working with Claude, they had full serial control of the switch, an API, auto-updating web interfaces over websockets, three web interfaces and setup screens. Each tape loop added gets its own record panel, and the main output has volume, tone and balance. It is web-only for now; the poster is considering physical controls.