First post, so be kind.

I've got a 40GB PS3, connected via the optical output to a Yamaha HTR-5660 A/V receiver. HDMI cable is sending video to my TV. I've got the BD audio output settings configured for Bitstream. When I watch a BD (or legacy DVD), I get great-sounding Dolby Digital going to my A/V receiver, but I've got a problem with the (two) Dolby Digital 5.1 games I've tried so far (Tom Clancy's GRAW 2 demo and Beowulf): Although the A/V receiver reports that it's receiving DD 5.1 signals for all 5 channels plus the sub channel, I can hear nothing but low-frequency sounds: everything sound muffled, and as far as I can tell I might ONLY be hearing the subwoofer channel.

If I disable the 5.1-channel output in the Sound Settings for optical output, and leave it set for 2-channel LPCM only, I get the 2-channel LPCM on the receiver, and the receiver decodes the signals okay using Dolby PLII.

I'm not entirely sure what to think is happening. I suspect something with the receiver, because I *occasionally* (usually during commercials) hear similar-sounding output from my DirecTV channels. My wife likes to refer to it as the "Charlie Brown effect". Think of the teacher whose voice is played by a trombone.

I don't want to plunk down $$ for a new receiver, but I can distinguish a difference between the PLII sound and the DD5.1 sound (even when it's working properly).

Does anybody have experience with the same receiver or a similar setup? Any ideas for where to look for the problem?

Just in case anybody runs into something like this, I got it fixed last night. Problem was, receiver was set for B speakers (supports A and B speaker sets) while on Dolby Digital, for one particular input. Changed to A (where the speakers are plugged), and it works great now.