This past weekend I noticed the project had started getting a lot more views all of a sudden. Turned out the reason was [Brian Benchoff] had covered it on the Hackaday blog.
In the article comments I saw a couple of requests for a pdf / png version of the FATCAT circuit diagram.
After I opened it up in KiCad I noticed I'd made a silly error. I'd connected pin 1 of the patchbay to the wrong thing (It should really connect to ground).
The error has been fixed, and the circuit diagram has been updated to revision 1.1. There's now also a pdf of it in the files section.