If I understand JoBoy correctly, the issue is not so much getting a WAV or AIFF file in the end, but to start with one. If you have to convert a lossy file format to an 'uncompressed' one, you have not recreated the data lost in compression, and conceivably produced a file even farther removed from the original. It's another question entirely whether a properly chosen lossy file format can do the job as well as an uncompressed file.
