http://www.rz.uni-frankfurt.de/~pesch/#mp3dc

I swear by this: Direct Cut, but you have to take it a step at a time: It does a lot of things but, as has been said it is hard to understand. It will do what is being asked in this thread.

I got the settings wrong recording a radio programme from my soundcard and, re-setting the gain level on this package got the volume down to match my MP3's, amazingly it also seemed to remove the distortion