The Red Book audio format used by CDs isn't improved upon by either SACD or DVD-A formats, it turns out. Extensive double-blind listening tests conducted by E. Brad Meyer and David R. Moran have shown that the old 16-bit, 44.1-kHz standard does not degrade the sound quality of either of the newer formats. The study, which took over a year to conduct, showed that the stereo analog output from a high-end SACD/DVD-A player showed no audible change when subjected to additional processing down to Red Book format. Now before you have a van Gogh-style freakout and cut off your audiophile-approved golden ears, that isn't to say that the DVD-A and SACD discs didn't sound better than the same title on CD. Give credit to the higher production values given to the SACD and DVD-A releases, though, not the formats themselves.
[Image courtesy PerfectSoundForever