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Sound quality poor after upgrade

I recently let Software Update install iTunes 8.2. After installation, all my music sounds very bad. The audio is severely compressed and sounds like it's had a bandpass filter applied. (no highs, no lows) Additionally, the sample rate may have been affected, as there is a grainy quality to the audio as well. Finally, the overall volume is lower.

I can open an MP3 in Audacity or Quick Time and it sounds fine. When playing the EXACT SAME MP3 in iTunes, it sounds awful.

This is true regardless of the audio source; previews in the iTunes store, music in my Library or on my iPod or even playing an Audio CD back in iTunes will reproduce the effect.

This is also true regardless of the playback device. When listening through the computer speaker, plugging in headphones or speakers to the analog audio output, also when using my Harman Kardon USB Soundsticks and I even plugged my receiver into the toslink output to verify there was not an AD converter problem.

This is definitely an iTunes issue. The Equalizer settings have no bearing on the quality; turning it on and off does change the sound slightly and preamp settings on the equalizer do affect the output level. In Preferences -> Playback, all the checkboxes are cleared. (Crossfade, Sound Enhancer and Sound Check)

I've re-started the machine, zapped the PRAM, turned on/off the settings in the Playback portion in iTunes preferences and restarted iTunes countless times after adjusting those settings. NOTHING has any effect whatsoever.

Help! I'm to the point where I want to re-install iTunes, but to tell you the truth, I'm not really sure how to do that! (Can I just delete the app and get it from the iTunes store from my browser?)

Mac mini (Intel), Mac OS X (10.5.7), 1.83 GHz Intel Core 2 Duo with 2 GB of RAM

Posted on Jun 6, 2009 3:24 PM

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13 replies

Jun 7, 2009 6:32 AM in response to Brian Dieckman

It's getting worse now; When I started the computer this morning, NONE of the applications will play with the normal sound quality as before.

This is really annoying...

I'll go back through my output tests again, I guess.

Does anyone know how to "reinstall audio" on a Mac? Can you even do such a thing? In Unix there are half a dozen libraries that control this mess, it should be similar in OSX, right?

I'm at my wits end here; thank goodness my iPod still sounds fine.

-Deek

Jun 13, 2009 7:45 PM in response to Brian Dieckman

I had the same problem. I don't know what causes it, but I know what fixed it for me:

In your home folder, navigate to the Library > Preferences folder. Remove the following preferences:

com.apple.iTunes.eq.plist
com.apple.iTunes.plist
com.apple.iTunesHelper.plist

Next, go to your home folder's Library > Caches folder. Remove:

QCCompositionRepository-com.apple.iTunes.cache

If you're missing any of these, don't sweat it.

Now, go to your /Applications folder and remove the iTunes application.

You can hold onto your preferences files, but the iTunes app has to go to the trash.

Next, Launch ActivityMonitor. (it's in /Applications/Utilities). Filter the list of running processes for "iTunes". If you see the iTunes Helper, ask it to quit. Once there are no iTunes processes running, empty the trash.

Now, go to http://www.apple.com/itunes/download/ and download the iTunes installer and reinstall iTunes. When you start it up, your audio should be back normal. While your preferences are gone, your library and playlists should still be intact. If you saved your old preferences, you can try adding them back, but it's probably easier to just change your settings back to the way you had them.

I hope this works for you as well!

Jun 17, 2009 5:02 PM in response to booleanman

I followed those steps and still the same result. I'm completely fed up.

I've reinstalled Quick Time, iTunes, flashed PRAM, switched sources, switched output devices and nothing seems to make any difference at all.

I'm thinking this is an OS problem, not isolated to iTunes or Quicktime... I'm going to post my issue on the Mac mini forum.

Thanks for your help.

Aug 19, 2009 6:47 AM in response to Brian Dieckman

Same problem. First it started on the speakers in my 24" Cinema Display and then later in the speakers and headphone port in my MBP. For some reason Flash wont even play through the display speakers which is interesting. I tried reinstalling Flash & Safari and countless restarts and combinations of things plugged/unplugged. VERY annoying. This is across every single app by the way and sounds like an old radio.

Sound quality poor after upgrade

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