@edmaul69 Ugh, sorry about the typos. Power supply is definitely 5v 2.5a (included in my RP kit) I also tried another 5v 5a supply, and the USB connection on the breakout box which is 5v 1a and actually works fine (though I use the kit supply in the permanent installation).

If anything downstream of the PI is PCM rather than Bitstream, it causes problems, so if anyone finds this in a search, make sure that your TV and audio system are all set to Bitstream.