2 channel SACD vs Multichannel SACD players...

Where did that guy come from. Must be an alien.

Anyway, I just got a Panasonic SA-XR10 receiver (digital multichannel) and it also talks about the downmix feature.

There is absolutely no technical reason why playback of the SACD 2 channel program should be better or worse than the 5 channel one. Of course the 2 channel mix might be more to your liking than the multichannel mix, but that is a function of the disc, not the player.

Some confusion may result from the DVD-A 2-channel capability, where the stereo mixdown is done by the player using information provided on the disc by the recording engineer.

Distortion...A two-channel program does not exist on a DVD-A, but instructions to the player regarding how to mix down the multichannel program into stereo are there. The DVD-A approach and the SACD approach accomplish the same thing in different ways. The DVD-A way doesn't use up as much data space on the disc, (for a complete 2-channel program) but requires a mixdown capability in the player.

Hardware for the three extra channels of a multichannel player cost almost nothing.

Bonger...You use the word "mode" which indicates to me that you are configuring your player for stereo playback, and the player is doing the final mixdown. (Remember all recordings these days are mixdowns from dozens of tracks on the master. Stereo is the most mixed of all, except for mono if there are any). SCAD does have a separate area of the disc where the complete program is duplicated in stereo format, and this area is selected in a manner that resembles choice of the stereo DVD-A format, so it is easy to think that they both select a stereo program on the disc.

That said, the DVD-A protocol is very flexible, and I guess it would be possible to put a duplicate program on the disc a la SACD, but if so you have a very unique disc. DVD-A allows for 192 KHz sampling (instead of 96KHz) when the program is only stereo, but I have not seen any discs that are actually made in this way.

I do have some discs that are recorded on both sides, with a 2-channel Dolby program playable on DVD-V players on the backside.

Arafel...Interesting...Exactly how can you be sure that it is a 2-channel program on the disc, and not the player realtime downmix which DVD-A provides? Is the program 196KHz sampling? Can you provide more details about the Emmylou disc: Label, etc. so I can look into this.

Soundhd...The downmix mode of player operation is described in the player owner's manual. I have used Panasonic, Pioneer, and Denon DVD-A players and they all did it. The producer of the disc can lock out this downmix feature by info on the disc, but I have not seen any like that.

Also, I heard somewhere that the gain coefficients for the downmix process are not fixed by the player design, but are provided to the player from the disc.

DVD-A discs do not have more than one layer. On SACD the SACD stereo program is on the same layer as the Multichannel program, but on a different area of the disc. The CD-readable program is on the second layer of a SACD disc.