Is your internal Mac volume all the way up? System Prefs>Sound>Output E.

yes it is,and when i A/B my session with CD's they are the same level. But ifi make a stereo interleaved 44.1/16bit copy, and a/b two songs in I tunes there is a substantial difference

Sounds like a simple reference level difference -- why don't you tell us exactly what you're doing when you're comparing levels (not in iTunes). Rail