I agree with andrei nz. Personally, when I compared WAV vs ALAC ripped files, I could hear no difference. Not sure about the correctness of cleeds comments w/respect to M4a from ALAC. ALAC compresses but is claimed to be lossless, as in "Apple LOSSLESS Audio Codec". Regardless of any theoretical advantage for one format vs the other, let your ears be the judge. Re-ripping would be a lot of work not to mention losing meta data with WAV.