but you need to play the same song as a WAV to be sure.

No, because we need to test against the actual files for errors first. If he's getting rip errors, those will show up in different places in the WAV. Besides, a poor encoder wouldn't distort the way he describes. He might hear some subtle compression artifacts, but not genuine distortion like that.

The correct first step is to listen to the MP3s in question on a PC and see if the MP3 files contain the distortion. Comparing to a WAV would be a much later step, after we've ruled out the more likely issues.

Hey, I wonder...

Anyone out there know anything about MMJB?

Here's a question. Does it have a fall-back option where, if it can't digitally rip the disc data, it will instead sample the analog L+R CD audio output? Maybe that's the way he's ripping his CDs and he doesn't know it? That might cause a distorted file.