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

Yeah, I used it to extract a 7Mb MP2 file encoded at 128k JS from the middle of a 140Mb MP2 file encoded at 80k mono (my DAB digital radio can switch encodings in the middle of a stream, which many decoders cannot cope with).