Mix looks fine. All 6 levels at 100%, nothing on input shows in the VU when input is playing. Used the assembly youtube video (frame by frame) to check capacitor orientation, they’re all aligned to the correct polarity. Attached is a high res photo of the input area of the DAC after I spent this evening de-soldering, removing, reseating, and reflowing the connections for the input jacks.
Another odd thing I just found: while there is still nothing when using arecord, when using aplay to play the blank file I’ve just recorded, if my source is still putting out sound, I can hear it (quietly) through my headphones. BUT the playback only lasts 15 seconds (as long as I recorded). To clarify, this 15 second chunk is definitely live sound, and the wav file is definitely empty.
Is there some audio firmware somewhere on my Pi4 that could be messed up?