They aren't..my (possibly incorrect) assumption is that at least ADD processing might have minimized the tape hiss and background noise. When I did a "collectors' classics" show on CJRT in the 80s and 90s, I had to make an unofficial arrangement with engineering to get them to shut off the limiters immediately before airing my show, or surface noise and crap would have been overwhelming. The particular CD I mentioned may be eminently listenable on most systems but not on a radio station which is aiming to put out a signal as loud as everything else on the dial. A couple of years ago the Buffalo station had similar problems any time it put on a Mercury Living Presence reissue or a
Sony reissue of any old Ormandy recordings. I don't notice this now but I don't know whether they improved their signal or acquired better transferred CDs.