More reading of the manual reveals that in another place it says DD/DTS are broadcast on optical as well as HDMI! So, it needed a thorough investigation.
Who would have thought that one dumb setting in the Sony BD player would remove the information the amp needs to decode the signals?
BD Audio MIX Setting:On
I turned it off, but why was it on? On is the factory default setting!
There are a few other settings I am not sure about:
Audio (HDMI):Auto
Alternative PCM, default Auto. No mention of optical out.
Dolby Digital/DTS:Bitstream
Alternative is Downmix PCM. Default is Bitstream.
DTS Neo 6 output from HDMI:Off
Alternatives are Cinema or Music. Default is off. I assume this is for 2 channel sources, as I already have Neo 6 on my amp if I need it. Also, again, we have that wretched phrase from HDMI! What about optical?
Audio DRC:Auto
Alternatives on/off. Default auto. Something about Set the sound effect when playing a BD or DVD. Are they talking about Dynamic Range Compression? I can do that in the amp.
Downmix:Surround
Whether to apply Dolby Surround to the output signal. Alternative is Stereo. But who would downmix to surround? It doesn't make sense! The factory default is Stereo. Are they talking about Dolby Pro Logic by any chance? But then, in what sense is that a downmix?