hier ein kurzer bericht von user "ddp", den ich sehr interessant fand und der alles zusammenfasst:
"Posts: 2 - From: San Francisco - Re: New Powerbook Audio Stutter /
Looping / Echo problem
Posted: 06.01.2006 20:37 in response to: purepeter
I've also been experiencing this issue since day one on a new 15" Powerbook 1.67 (Double-Layer SD). For the record, this is the fifth Powerbook I've run OS X on and I did not have this problem on a 1.5Ghz 15" I upgraded from. I initially transfered everything using Migration Assistant, however I've subsequently re-initialized my disk and re-installed from scratch, moving my user data by hand (i.e., completely avoiding Migration Assistant). I did ultimately restore /Library/Preferences from back-up, so it's still possible a corrupt/stale system preference file could be a contributing factor, but I have my doubts. I did not experience the audio problem before restoring my user data, however I could not authoritatively state that the problem was not present. There's just a limit to how long I can last without my environment.
Regardless, I tried deleting my com.apple.audio.* preference files and determined that that's not effective. The newly created file differed insignificantly from the previous version and the stutter still occurs.
I tried resetting my NVRAM ('reset nvram', 'reset all') in Open Firmware and the stutter still occurs.
It occurs ever three or four hours when I'm listening to something via iTunes and I've also heard it while using only Bias Peak LE 4. It occurs regardless of whether I'm listening via the built-in speakers or via headphones.
Interestingly, I've had it happen while I was recording something in Peak. The input was analog in via the microphone jack through to disc, with hardware and software monitoring enabled. I heard the stutter on headphones while recording, but it was not present in the recorded track on disc when subsequently played back. So the bug seems clearly on the output side of Core Audio.
I don't see an obvious way for me to determine whether it's software or hardware, but as a software engineer with extensive OS, driver, and hardware experience, it's way more likely to be a software bug than hardware IMHO. But I can't rule out the hardware. My previous Powerbook, which doesn't exhibit this problem, uses a Texas Instrument TAS3004. This one lists a Crystal Semiconductor CS84xx and a Burr Brown PCM3052. So clearly there's new drivers and new hardware in play.
I take Apple's somewhat cryptic Tech Note #302978 as an acknowledgment of the problem. If it's software, I'm sure they'll fix it ASAP. After all, there have to be quite a few folks in Apple Engineering who listen to music through their shiny new Powerbooks and they can't be very pleased with what they're hearing. I do think we deserve a little more useful information though. I'm personally tired of being told by Apple Tech Support, literally, that maybe it's my headphones and could I please try another pair..."
Powerbook 15" (Double-Layer SD) Mac OS X (10.4.3) "