I decided that I would also re-rip the albums that I had previously ripped from duplicate cassettes, since that should improve the sound quality. At one time I couldn't tell the difference between a cassette and an LP, but now I can. The vinyl rips are brighter, punchier, the cassettes are sort of squishy. I don't know how else to describe it. And this goes for commercially produced cassettes as well, most of which (in my collection) don't sound as good as my old duplicate tapes.
I just did an evaluation of my recent rip of Tales of Mystery and Imagination, the first Alan Parsons Project album. It was almost perfect except for a bad pop/skip on "The Fall of the House of Usher." So I went back and listened to that track from my tape rip, and it was perfect. Since that record hasn't been played since I made that recording all those years ago, the damage to the vinyl that caused the skip must have somehow happened in storage. My entire record collection has been moved a few times in the past 20+ years, so I must conclude that some speck of dirt got into there somehow during a move and caused a tiny scratch in the vinyl. I don't know how else that could have happened.
So in this case, I'll have to keep the tape-rip version for that track, even though it is noticeably different. Well, it's noticeable if I'm paying attention.
P.S. The high-res (like 256 kbps and up that I download from Amazon) mp3s also sound different, even brighter and punchier than vinyl, and also sort of brittle. The ones saved at 128 kpbs sound just about identical to vinyl. Or maybe I'm imagining the whole thing.