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I've been working on my early-2008 iMac of late, replacing the HD with and SSD, and upgrading the CPU to 2.8 GhZ. The SSD and new CPU seem to be working fine, except after I finished I ended up with this weird audio problem: ALL audio is distorted. I've shared a couple of links to demonstrate:

Clip of Middle C

Stars and Stripes Forever

This happens both through speakers and audio out. I cannot seem to find the source of the problem. I've tried the following:

  • Replaced the audio board
  • Replaced the audio board / logic board flex cable
  • Replaced the logic board
  • Booted off an external HD
  • Downgraded to Mavericks
  • Reset the PRAM
  • Reset the SMU
  • Terminated CoreAudio

NOTHING seems to work. The audio just keeps coming through like it does above. My only thought is maybe my power supply is shorting out and messing with the audio, but I don't want to pony up for a new component until I have a better idea.

Does anyone have any ideas?

Note: This only happens after I boot. The startup chime is not affected.

  • I'd try something off the USB port; headphones, 'sound 'card' etc - eliminate the internal hardware. Those clips sound almost like the output device has such low latency that the machine can't keep up - it's not strictly 'distorted' it's 'not got enough time to keep playing' – Tetsujin Mar 4 '15 at 20:54
  • Thanks. I wish I had a USB audio device to try this with, but it's a good idea. I agree with your characterization of the sound seeming like a latency issue. – desktopia Mar 5 '15 at 23:03
  • Did you try a hardware test? Without additional expense, the only other thing I can think to try is put back the old CPU. – Tetsujin Mar 6 '15 at 6:58
  • I did try a hardware test. As usual AHT was useless. I just booted into Ubuntu and the audio played just fine. Just to double check, I booted into Mavericks via eHD and it still didn't work. – desktopia Mar 8 '15 at 22:17
  • I did try a hardware test. As usual AHT was useless. I just booted into Ubuntu and the audio played just fine. Just to double check, I booted into Mavericks via eHD and it still didn't work. My latest guess is that the new CPU and Mac OS X just don't play nice, so replacing the old CPU will be my next move. Thanks for the help so far. – desktopia Mar 8 '15 at 22:17
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So I swapped the original CPU back in and everything works fine. Oddly, audio in Ubuntu worked just fine with the original processor, but not in Mac OS X 10.10. Thanks for your help, Tetsujin.

  • I had a feeling that might just be the answer – Tetsujin Mar 11 '15 at 19:04

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