iTunes ruins my audio

You are not alone. There are 2 threads on a similar problem with iTunes 5.0 that were posted earlier after version 5.0 came out. I'm going to provide the links for reference:
MacGallant, "iTunes 5 playback glitches" #10, 04:23pm Sep 13, 2005 CDT
MacGallant, "Anyone Else Experiencing iTunes 5 'Popping'?" #3, 11:20am Sep 12, 2005 CDT

These "pop" noises have plagued my .wave files too! They are the recordings of meetings, lectures, concerts, etc. The latest 5.0.1 version doesn't help, either. Someone please help!

Whenever I hear that music quality sounds degraded in iTunes but just fine in QuickTime, I think of the iTunes preference file. If you can play the same music files through iTunes from a different user account and the music sounds fine, then the preference file truly becomes a suspect.

With iTunes closed, go to the Library folder in your user folder, open Preferences and look for the
i com.apple.iTunes.plist
file. Drag it to the Desktop (you can Trash it later, if this fix works). Start up iTunes, and it will build a new preferences file with default preference choices. You may have to reset some of your preferences, but your existing music library will not be affected at all. Play music, and hopefully the sound quality will be restored to normal.

Please report back if this helps your situation.

I have noticed my sound quality has turned "lo-fi" with the new iTunes. I can trash my pref file as described above, yet it returns to lo-fi quickly after, not quite a sharp decline in quality, but gradual. I can play a song in quicktime and it sounds punchy and crisp, but I cannot get the same from iTunes. This is strange.

Odder still--it isn't just iTunes 5.0, I still use 4.8, and this problem just came on yesterday or today. Suddenly went lo-fi, whether headphones or AirTunes. Quicktime plays them fine. I trashed the pref file as described above, and now it works fine (for the moment).

In the last few days I've upgraded my I-Pod software and added Palm Desktop software. Don't know if that has anything to do with it.

I am having the same experience: When I playback from a tape recorder and record into my iMac G5 using the internal microphone and saving as a AIFF audio file the results are clear when playing back with Quicktime. However the quality is awful (hiss/popping/static/ when imported and played back in iTunes 5.0.1. Previous recordings using this procedure stored in iTunes sound great but not with 5.0.1. Recording of lectures and importing to my G5 and into iTunes and then into my iPod is important to me. Any assistance will be appreciated by another user or Apple when they come available.

Thanks a lot for your suggestion. It worked for me.

Audio quality turned really bad in iTunes, but was just fine with Quicktime.
I followed your instructions to build a new preference file and the sound quality is now back to normal (hoping it will stay that way).

I am going back to 4.7, as I didn't have any problem until 5.

What is happening on my end is that Version 5, both in Mac and Windows, erroneously plays AIFF files with 8-bit sample sizes, blurring the sound and throwing in a lot of static. MP3 files encoded from these 8-bit files in Version 5 also are overrun with static. These files are those I previously recorded using my old G3's built in AV card and Sound Studio, and they have never shown any problem playing before, and they still play perfectly from the iPod out of its speakers, but not while connected and playing through iTunes 5.

The problem for me seems limited to uncompressed files with 8-bit sample sizes. Files I've recorded using my G4 and a USB input with 16-bit sample size do just fine. I haven't yet attempted to use Quicktime or Sound Studio to resample the 8-bits to 16-bit and see if iTunes 5 plays those resamples OK.

On my work machine which is Windows, I just uninstalled iTunes 5 and used a 4.7.1 installer I kept, and my 8-bit AIFFs just sprang back to life.

If this problem exists in both Mac and Windows versions of iTunes 5, then I think it goes deeper than a preference file problem. I have no idea what change to the algorithm would necessitate abandoning 8-bit sample sizes, but that seems to have been done.

ITunes 6 has fixed my problem!

I installed iTunes 6, hoping that my music would stop becoming staticky. No such luck. I have tried: other players (no problem), converting files to AAC (useless), importing a CD with iT6 (no help). Through a process of elimination, the problem is iTunes. Previous versions were fine. Any suggestions?

I've experienced the same problem. I've noticed that not all of my music has picked up static, only the ones that were "encoded" by previous versions of BOTH itunes (4.7.1) and Quicktime (6.5.2), AND that I recently recorded on CD's ... wierd! Anyway, I'm updating the ones that are this way and haven't yet been affected. Go to menu ... "Advanced" ... "Convert selection to ..." Hopefully, this will update things. I'm afraid the ones already with static are "toast," and will need to be replaced.

Al