I continue to be amazed by the poor documentation Pioneer provides about how to get surround sound working with sources other than DVD, DVD-A, and SACD discs.
The manual suggests that you leave the stereo/surround sound setting on Auto, and the system will select the correct one based on the original source material. I took this to mean that when I piped the stereo signal from my TV through the receiver, it would automatically detect surround sound broadcasts and select the Dolby Pro Logic II decoding.
But of course, nothing of the thing happened. Instead, it seems that the appropriate solution is to select the Pro Logic II setting for the TV source and leave it there, hoping that when presented with a non–surround sound source, it won’t muddy the waters too much.