04 WRX - no sound from head unit

[CW]

For no apparent reason, my head unit no longer has sound. It seems to
function properly in every other aspect but there is no sound at all.
When I turn on the car, I can hear a faint static blip from the right
front speaker but that's it.

Anyone every had this happen? It there some internal fuse or circuit
breaker on the outputs of the head unit?

Thanks,
Carleton