Nobtwidler is, as he should be, considering his job, absolutely right. The original multitrack master has a stereo master that is EQ'd for the end product. Because vinyl can't cope with the full frequency range, the music is compressed at each end, the high frequency to stop 'ringing' that could overheat the cutting head on the lathe used to cut the metal stampers and the low frequency to avoid large transients that could cause the stylus to jump tracks, or for a groove to run into the next, causing the same to happen. That's why, as nobtwidler says, early cd's sound thin, because the full dynamic range wasn't on the stereo master. Even worse, the metal masters sent to different pressing plants could get damaged, so a new one would be cut from a stereo safety master sent to the mastering company, so you then have pressings made from a master tape that's a copy of a copy, and that would often be used to master cd's as well. I've got old vinyl where one side was pressed from metalwork mastered by Bob Ludwig at Masterdisk in the US, but the other by Stirlingsound in the UK, and you can hear the difference in quality caused by using a tape copy for the second side with a high end turntable, like my old Logic DM101/Zeta/Audiotechnica MC. This is what makes me laugh about idiots complaining about MP3's not being as good as vinyl because of the compression, when vinyl was produced by compressed, or EQ'd tapes. If you play a variety of tracks ripped at 320Kb from a variety of albums of different ages, through a really good pair of in-ear 'phones, like Shure's, Denons or Ultimate Ears, (my favourites), you can clearly hear differences in the quality of the original mastering, and I'm afraid that the Led Zeppelin Re-Masters are bloody awful, Jimmy Page should have been locked out of the studio. The remasters of the Stones albums like Sticky Fingers are stunning, and some of Free's early stuff was remastered and put out as The Free Story, before they fell out, and those tracks are marvelous. There's a Buddy Holly album, ‘From The Original Master Tapes’, which is breathtakingly wonderful, considering the tapes are fifty-odd years old. The Beatles re-masters are the first time they have been touched since they were first released, so the original cd's would have been compromised by incorrectly EQ'd stereo master tapes. I'm not a sound engineer, btw, but I used to sell hi-fi, and I used to read HiFi News and Record Reviews back in the early eighties, and a writer on there, Ken Kessler, used to go into a lot of detail about how albums were mastered, and what to look for in the runout grooves regarding the ID of the mastering lab who cut the stampers, which I paid obsessive attention to when buying vinyl. Don't work with cd's, sadly.