With most modern audio panels, when they fail, you still have a connection
to the mic and headset jacks on the #1 COM. You can test this by simply
turning the audio panel "off" and seeing if the #1 COM works.

There's an emergency switch. It turns out I had forgotten about it
and, yes, I should've been a bit more familiar with all the avionics -
who ever thinks an audio panel has any real complexity?? It doesn't,
but there is a thing or two to know.

If I'd have been in the air for any *significant* time, though, I'm
pretty confident I'd have figured it out.

Switching it "off" does *not* result in COM1 pass-thru. It was off -
dead - the whole time.