blu -ray audio

I am using my high-end 2 channel system for movies, and prefer classic films with their original mono or 2 channel mix when available. Most blu-rays offer a selection of 5.1 or 7.1 dolby tru hd or dts master audio, as well as the original mono or stereo/dolby surround mix. Am I correct that these alternate mixes are not lossless, and if so, is the lossy quality better than the same mix in the dvd?   Any comments would be greatly appreciated.
Er, no.

AFAIK, all formats in BluRay, except HD or Master are potentially lossy.

The DVD and BluRay format allow the producers a great deal of latitude in audio and video compression. Dolby Digital (5.1) was the original lossy and not particularly well thought out format. DTS was not lossy, and had a better thought-out bass integration. It gets very geeky. :)

Some of this early DVD stuff is a direct result of what was happening with motion picture audio. Dolby Digital (5.1) was made to be squeezed in the optical film, alongside analog tracks, with limited physical space and resolution of the readers, not to mention interference from dust occluding the film and reader. DVD's with DD take the same lossy data.

DTS was higher resolution because all they put on the film was a time stamp. The actual film audio was read off of separate CD's using especially built readers.

So for DVD, DTS is always your better option. With BluRay, the data available is much better so I expect HD and Master audio to be equivalent.

Having said all of that, not sure what you'd like. I just heard The Longest Day, which was produced long before even Dolby Surround, remastered in 5.1 and it wasn't bad.

Thank you.  Really just looking for the best sound quality preferably in the original mix.  I'm using a computer for my audio/video and to be honest bly-rays are a PIA and I'm satisfied with the video quality of upscaled dvds (actually in some instances I prefer it).  I do want lossless if possible but  I was under the impression that ALL dolby digital in dvds was lossy - not just 5.1.  Do I understand you correctly that all dts in dvds as well as dd mono and stereo tracks are lossless?  I wouldn't be surprised because to my ears those mixes sound as good as blu-rays - I do agree with you that the dd 5.1 do not sound good. thanks