řeší se to i na diskuzním foru apple:
I compared listening to an MP3 file via Finder's QuickLook versus iTunes 9.1 (79) and found a SIGNIFICANT difference in sound quality. The iTunes output through the exact same output/headphones is obviously being reprocessed and is a lower quality than the actual music file (MP3 @ 256kbps).
It's clearly not the same quality audio coming out of iTunes as the Finder/original file when playing the exact same MP3 file. It is oh so slightly muffled and there are so many ways it isn't as clear or crisp yet midrange vocals seem intact, sounds like 96kbps from a 256kbps source MP3 file.
http://discussions.apple.com/thread.jsp ... ID=2391767
mně se zdá zvuk hudby jakoby zastřený a ztlumený, myslela jsem že mám špatně nastavený ekvalizér...