As I had difficulty identifying repeatable differences after ReplayGaining the test files (btw - WAV? srsly? FLAC is just over half the size to download!), I fired up DeltaWave. Man, it sure didn't like C, I'm guessing that was from another run? The delta keeps fading in and out, suggesting some wow on part of the TT drive mechanism that obviously isn't repeatable. A and B matched up much better, with most differences >18 kHz as expected, and I think there's a slight difference in frequency response towards the low mids and bass.
So, not sure about C, but I guess some measurements of A and B would turn up the differences in frequency response that once EQ'd out, would eliminate the majority of remaining delta. If I can just EQ it, it's not a substantial difference, now is it?