I'm using the right and left audio outputs out of the DVD, but I think the audio can come out either in stereo or Dolby Pro Logic (not the 5.1 surround which is digital.) I looked up Dolby Pro Logic in wikipedia:
and it says:
"Dolby Surround/Pro Logic is based on basic Matrix technology. When a Dolby Surround soundtrack is created, four channels of sound are matrix-encoded into an ordinary stereo (two channel) sound track by using phase shift techniques. A Pro Logic decoder/processor "unfolds" the sound into the original 4.0 surroundleft and right, center, and a single limited frequency-range mono rear channelwhile systems lacking the decoder play back the audio as standard Stereo."
So what I think is happening is that the A/V receiver is decoding the Pro Logic in surround mode and playing it in stereo with the surround off.
I'll look to see if there is an option on my DVD player to always output a stereo signal (versus Dolby Pro Logic), but I don't remember one. I think it just outputs whatever audio format you are choosing on the DVD. The DVD in question has only two English tracks: a 5.1 surround sound and a two channel stereo with the Director's comments. When I choose the 5.1 surround sound, I think the Dolby Pro Logic signal is coming out.
So if the Wikipedia page is correct, a 2-channel receiver without a decoder will play back a Pro Logic signal in standard stereo. Does this make sense and can anybody verify this? I guess I'd like to know how the Matrix encoding is working to convince myself that it is not affecting the fidelity of the 2 channel signal.