As some of you know I have a background in performing, recording, mixing, and mastering classical music for over thirty years. I recently took some of my masters which are 192K 24 bit and used Apple's Mastered for iTunes tools to create compressed AACs from them. Among the tools is a plugin that lets you AB your original file to the compressed AAC right in your digital audio workstation. I was able to get quality so close to the original that I nor several other people that I trust could reliably distinguish between the two. Subsequently, I have purchased a few tracks from iTunes and made sure to look for the Mastered for iTunes logo. I have been extremely impressed! The bottom line for me is the largest factor in the sound quality of a file or even a vinyl record for that matter is the mastering. Often times a particular medium sounds better than another because the mastering for each was done at a different time by a different person. If you are interested in reading the white paper for mastering for iTunes here is a link: https://images.apple.com/itunes/mastered-for-itunes/docs/mastered_for_itunes.pdf
