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High pitch squeal related to Firewire audio device after 10.6.2 audio patch

So the recent Mac Pro audio update 1.0 (applied on 10.6.2) has reduced my CPU temperature with audio playback (Presonus Firebox Firewire audio interface) and that is great. Also haven't had any machine crashes (grey screens) recently which is also great.
The problem is that when the Firebox is plugged into the firewire port of the Mac Pro there is a constant high pitched whistle of slightly oscillating frequency. If I unplug the Firebox the whistle goes away in a few seconds.

After prolonged use in a quiet room (the kind of room you need for audio recording / mixing work!) the noise is enough to drive me crazy.

I read a post on another forum with other people having the same problem. Can anyone comment here on seeing the same thing? Is there any known work around or fix for this?

When the CPU is under heavy load (e.g. H.264 compression etc.) the noise subsides only to return when there is normal load (i.e. half a dozen apps running).

Help!
Thanks

Mac Pro Early 2009 Quad, Presonus Firebox, Firewire, 24" LED Cinema, Mac OS X (10.6.2), Mac Pro Audio Update 1.0

Posted on Feb 16, 2010 8:23 PM

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46 replies

Feb 22, 2010 2:18 PM in response to matt79_M

I'm having the same issue - resolvable by unplugging my audio interface from the firewire. Which, obviously, isn't a workable solution...

It's very uncomfortable - I use my mac professionally, and at the moment I can't spend more than a few minutes in the room at a time because of this unpleasant high-frequency sound. Is there any way of finding out whether apple are getting this fixed as a priority?

Feb 22, 2010 4:54 PM in response to meridiandevv

So I was able to back out the update using "Kext Helper b7" and the original IOPlatformPluginFamily.kext and AppleHDA.kext files from a backup before applying the update. It's pretty easy - just drop the two files onto Kext Helper, hit "go" and then reboot.
My ears are no longer in constant pain and I can actually use the Mac Pro again albeit running quite hotter than before.
This is not a fix Apple. The problem looks unrelated to a specific device based on the posts in this thread. Please issue a usable fix for the Mac Pro Audio performance issue.

High pitch squeal related to Firewire audio device after 10.6.2 audio patch

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