Based on your log
18:56:56 T:4584415232 DEBUG: CCoreAudioAEHALOSX::Initialize: No suitable AC3 output format found. Attempting DD-Wav.
The amp TV doesn't announce AC3 capability properly and the dd-wav fallback seems broken. Not much i can tell you - but yeah coreaudio is giving us issues all over the place and there are always setups which don't work. (but for defense there are also some setups which work ok ).
Can't you shuffle around a bit so that your mac goes via hdmi to the amp? Would be interesting if this would work then.