Many users are displeased with the apparent difference in sound quality after upgrading to iTunes 10 on their Macs. A growing thread in the Apple Support Discussions forums sheds light on the issue that seems to be affecting many Mac users' listening experience.
ASD forum user Adrian Whitfield posted:
"After upgrading to iTunes 10, I noticed when playing music from my library that the audio quality is significantly lower than previously with iTunes 9.x. The audio quality sounds muffled and distorted.
I found this thread in the Windows section, but wondered if other Mac users were experiencing the problem as well.
I ended up downgrading back to iTunes 9.x and the problem was resolved. Any ideas?"
Sound issues can be caused by any number of things. As ASD forum user Jason L notes, third-party plug-ins may be the culprit. Whenever iTunes is updated, developers have to play catch-up with their software. This can lead to all sorts of issues. Users can wait to upgrade iTunes until their favorite add-ons are updated, or disable them before upgrading iTunes and install the new versions as they're made available.
Users should also check the preamp setting on the iTunes equalizer. In the iTunes menu bar, click Window > Equalizer. Be sure the preamp slider is in the middle of the track.
"iTunes 10.1 narrows the stereo image and sounds canny.
All hints followed but no improvement. Easily identifiable on a pro meter.
Dragging an mp3 out of iTunes into the Finder and playing thru QT reveals that the Mp3 itself is fine. But the iTunes playback quality of the same file is definitely not. Both AIFs and Mp3s suffer from this detoriation."
If the MP3 file is the issue, try checking out the frequency range settings in the Audio MIDI Setup application as suggested by ASD user micih:
"Open Apples AudioMidi-Application and check frequency and bit rate for your interfaces' output! In my case the frequency range was set to 8000kHz for the sound sticks, put it back to 44.1kHz and Tatatataaaa: crisp sound again! (you may have to restart iTunes to have it respect this setting)."
This is a fix that has been working for some, and maybe all:
(adapted from a post by "FSD" from a thread on Gearslutz that is discussing this topic:
- Close iTunes
- In system Preferences, change the sound output from your external interface to Line out
- Open iTunes and start to play some music
- While iTunes is playing, change the Line Out back to your external interface
You may well have to do this each time you launch iTunes - I don't know yet.
Link for thread: http://www.gearslutz.com/board/music-computers/549883-itunes-10-1-ruined-playback-sound-totally-3.html
Right now, the core issue does not appear to be fixed. Apple has no official documentation on this specific issue, though it is likely an issue that would be fixed in updates.