The dynamic range of the AP DVD-A is truly astounding and the fidelity is superb. You need to remember you are listening to a direct transfer from the original quad mix master tape. You can't really compare this to the polished commercial output of the SACD. Knocking one vs. the other in terms of tape hiss is an apples/oranges thing. It's not even worth mentioning.
Had the AP quad mix been used for the SACD you can bet it would have been cleaned up as well. What you're hearing from the DVD-A was not meant for public consumption. There is a DTS version of the AP mix floating around that was cleaned up for commercial release by DTS Entertainment. Rumour is it was just about to be released when the project was cancelled in favor of the SACD project. Anyway, the level of tape hiss on this version is comprable to what you find on the SACD. Overall, the DTS version sounds very good, but the fact that it is lossily compressed and has noise reduction applied obviously impacts the fidelity. I'll take the un-fucked with hi-rez direct transfer from the AP quad master tape any day.
That said, there are some tracks off the SACD that I do prefer to the AP mix. One of these days I would like to put together a disc containing my favorites from each, but it would be pretty tough to edit them together.
Check out this thread for a track-by-track rundown. When I wrote this I didn't have access to the AP DVD-A, but the comments about the mix differences are still relevant: http://www.quadraphonicquad.com/foru...read.php?t=980