Mac Pro Special Report: Audio problems: Line out settings, distortion

CNET staff

Sept. 2, 2009 12:02 a.m. PT

4 min read

Internal vs. external speaker confusion Some users are reporting an issue where the Mac Pro forgets to which device it should send audio output -- in other words, if the user specifies external speaker output, the system will still use the internal speaker after restarting.

MacFixIt reader Desmond Foulger writes:

"Has anyone noticed that the Mac Pro, doesn't remember where the sound should come from? I have my power speakers connected to the line-out socket on the back but when starting up, the tinny startup tone comes from the internal speakers. It looks at line out after startup but surely it should remember this before starting up? I could take the sound from the loudspeaker socket from the front - but that's so untidy."

Another reader writes:

"I've got the same issue as reported on your site today regarding sound output and the Mac Pro not 'remembering' where it should send audio output. Like the reader who reported the problem, I've got a set of powered speakers connected to the sound output jack in the rear of my Mac Pro. Upon startup in the morning, however, the startup tone comes from the very tinny internal speaker. It then reverts to the powered speakers afterwards. Not a big problem by any means, but this was not an issue with my previous G4/400. It would be nice, however, if Apple fixes this in a future OS update."

Readers have also reported other erratic behavior with line out settings, including a change in settings under different applications, i.e. one application will play audio through the externally connected speakers, while another application will play audio through the built-in speaker.

One reader writes:

"Until late last week, I'd noticed the same tendency of the Sound prefs pane to not retain Internal versus Line Out settings. I'm not a frequent restarter, so I hadn't experienced it more than a couple of times.

"Then, the settings started to vary between applications. For example, iTunes still plays through my powered 2.1 system, but Real Player output gets sent to the internal speaker. To make matters worse, the maximum volume of the internal speaker seems to have dropped by 20db or so. I can barely hear Real Player and, because I set Sound to pipe alerts through the internal, my system beeps as well.'

"I went through my Library folders and deleted some audio and QuickTime related prefs and property lists, and I did a clean install of the latest Real Player -- but no change."

Meanwhile, another MacFixIt reader reports that applications running under Rosetta cannot use external speakers on his Mac Pro. He writes:

"I've found that PPC apps only send their sound to the internal speaker where intel (UB) apps will work with the external speaker port."

Audio distortion MacFixIt reader Russell Low reports the development of distortion from the line out jack on the back of the Mac Pro, a problem remedied by using the headphone jack on the front.

Russell writes:

"After 4 weeks, my Mac Pro has suddenly developed a horrible distortion from the audio line-out jack on the back of the machine. The distortion appears even at low volume levels from any source, including iTunes, the web, and even the internal alert sounds. Thankfully the headphone jack on the front of the unit is still distortion-free, so I've connected my external speakers there for the time being. The internal speaker seems to be OK as well. This is obviously an electrical issue and perhaps a unique circumstance, but it still needs to be repaired. I'm not looking forward to lugging my heavy Mac Pro down to the local Apple Store and being without it for a while, as it's been an otherwise fantastic machine."

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