What's the best audio setting for DVDs in "digital stereo&quo

[medjuck]

My 5.1 receiver has a control button for switching the "effect" off and on. What it does is switch off the sound to the center and rear speakers. If the effect is set to off and the source is in 5.1. all signals will be distributed to the main speakers (and the subwoofer). If you play a cd, the effect is automaticly off though if you turn it on the sound will come through all 5 speakers in what seems to be an artificial surround effect.

I've recently gotten a couple of DVDs that seem to be in stereo. One is "AudioSlave in Cuba" which has no

indication of the correct sound system on the box, label or DVD menu-- despite giving a huge credit to a couple fo guys for the sound mix. The other is the new and by me highly recommended "Duke Ellington" which contains 2 tv programs produced by Ralph Gleason in 1965: "Love You madly" and the gorgeous

"A Concert of Sacred Music at Grace Catherdral".

The Ellington disc has an audio setting in the menue that allows you to listen to it in mono or digital stereo. On the box it says "mono" or "Dolby Digital Stereo" but then adds to the latter ""(extrapolated)"--and what the hell does that mean?

Anyway the Audio Slave is in stereo and the Ellington seems to me to be in mono no matter which setting I pick from the menu. My question is: given a mono or stereo mix on a DVD should I set my receiver to effect on or off. I've tried both and am not happy with either. I don't have this problem with cds. They sound best with effect off though sometimes I leave it on just to fill the room with sound.

Edited November 25, 2005 by medjuck