JPP, Thanks for the quick reply. I guess I need to experiment. My HDMI sources are a Motorola PVR, an Oppo 105 (also doubles as a stereo analog source) and a legacy Toshiba HD DVD player. I gather the 750, like the 600, will not decode DSD, meaning I should continue to set my Oppo to output PCM only?
You don't need to do anything; HDMI connections automatically negotiate and select compatible formats. As the AVR750 won't accept DSD, the Oppo won't try to send it and will automatically fall back to sending PCM.
It's actually quite difficult to get an Oppo to output DSD!