If the source is 2 channel audio, will your MacIntosh add a center channel? Does this issue occur on movie channels? PPV? Is the source 5.1 or 2 or 2.1?
If the source is 2 channel audio the Mac will add a center channel depending on which input mode I select. The only time I do not select to use a center channel is for listening to stereo music, such as Sirius/XM or CDs; in those cases I select the stereo input mode.
The problem occurs only when using the Dish receiver's optical audio output and it occurs with both a Dolby Digital signal and a Dolby Pro Logic signal. The problem is intermittent (meaning the problem varies from TV channel to TV channel) and could occur on any channel -- regular and movie channels. The problem always occurs immediately when first locking in to a TV channel. In other words, after the TV channel is locked in the sound will immediately be okay or not. The sound will not change after the initial TV channel change. (Was that confusing?)
For example, if I tune into the local ABC HD, I sometimes do not get center channel sound. If I tune into local non-HD ABC then I sometimes not get sound from any of the speakers. If I go out of that problem channel and then return to it the sound may be fine. That's what I mean by intermittent.
Interestingly, I lose the center channel sound only on HD channels and I lose all sound only on non-HD channels.
If I use only the Dish receiver's analog audio output (RCA left/right) then there is no problem; however, it would be in Dolby Pro Logic and not Dolby Digitial. The problem occurs only when using the Dish receiver's optical audio out. I know for certain that my optical cables are good.
Note that the problem never occurs when using a DVD source or the 501 Dish receiver.
Whew! Catch all that?