In reply to:
I too lose Rx when the audio panel is unpowered; at least until I partially unplug my headset from the connector in the armrest console. Something to do with polarity on the headset plug?
Quite possible if you have a Mono headset - but I doubt you do. Next most likely - check the Mono/Stereo switch, if you have one. It should be set to Stereo. If set to Mono it’s possible to get the symptom you have.
It’s not really “polarity”, but channel reversal - on many Cirrus airplanes, the right/left channels were wired swapped, so a mono headset may get nothing in the emergency bypass mode. This is easily corrected but most regard it as not worth a trip to the avionics shop; quite low-cost to fix in conjunction with other avionics work, though.