"I understand that MP3 removes what all but very-very
young ears Hrz can detect+."
If that's the conclusion you've come to, you may want to re-evaluate your system. Most people find it fairly easy to tell the difference.
"Part of MP3 is a compressed file., And if not been removed
Then I want to decode it. Like you and everyone does with
there DAC. Up-sampling. That is if you play digital music..
"
Buy the looks of it, I'm not sure you fully understand what's going on here. MP-3 is lossy compression. Once you make the conversion, you can't get the information back and reconstruct the original format. When you "upsample" an MP-3 file to WAV, nothing is done to change the sound quality. It's more of a trick used to make the MP-3 file compatible with WAV. The MP-3 is made to look like a bigger, uncompressed file in order to get it to play, and nothing more. If you don't believe me, its easy enough to test. Take a Redbook CD and rip it to MP-3 files. Then take the MP-3 files you just made, and burn them to a to a CD-R set up to make a Redbook compatible audio CD. Then listen to both CD's.