@Alan. It seems I was wrong.
There is a 'matching' audio in socket, detailed
here.
Apple says:
Optical digital audio input is S/PDIF format and uses a standard Toslink cable with a Toslink mini-plug adapter, accepting up to 24-bit stereo and 44.1-96kHz sampling rate.
Comments
I wonder if an Apple player/control app of some kind would be more likely to do TV volume without the use of an audiophile app.
It could all be run headless, with the little apple ir remote.