HYBRID SACD stereo or multichannel.

"Hybrid" refers to the fact that the disc has two layers, one reflects light at the wavelength of a CD player laser, and the other at the wavelength of a SACD player. Of course, the CD layer, which you can select, is 2-channel. On the SACD layer, there is both a stereo, and a multichannel recording, which the user selects.

DVD-A are multichannel, but can also be played in stereo. In this case the player does the mixdown as the disc is played instead of the recording engineer doing it when the disc is produced. I think this is a better approach because no data space on the disc is wasted by a duplicate recording, and details of the mixdown can be selected by the user so as to give a different sonic perspective: on stage with the performers, or out in the hall.

Metralla....I am curious WHY you are put off by the DVD-A method for stereo playback of multichannel discs. It seems to me that the flexible DVD-A protocol is far superior to the locked-in-concrete rules that Sony has laid down for SACD.

Metralla...Thanks for explaining your reasoning. As I understand it (and info is scarce) the mixdown coefficients used by a DVD-A player in creating the stereo program are selected by the recording engineer and encoded on the disc. So the recording engineer is still in the loop. Of course, almost all recordings, CD, SACD, and DVD-A, are mixed down from a dozzen or more tracks, so one more mixdown can't be all that bad.

Audiobugged...Sure they can. They have just two channels, with the sound intended for the rear out-of-phase between channels. When a quad record is played back through the intended decoder, out-of-phase signal is attenuated for the front speakers, and in-phase signal is attenuated for the rears. If you play the record without a decoder, the out-of-phase signal will come from the front speakers, but because it is out-of-phase it will not image, but will have a difuse and directionless quality. This is not bad.