Distorted Audio from Speakers and Line-Out

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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.
 
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2011 27" iMac, 1TB(partitioned) SSD, 20GB, OS X 10.11.6 El Capitan
What happens with a Safe Boot??

But that doesn't sound like any software problems. :(
 
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It seems that sound/audio can be one one of the Apple things that doesn't get loaded with a Safe Boot.

So if everything worked properly before the "upgrades" you did, I'd suspect that something got messed up or you have some sort of hardware conflict. But you sure did a number of different mods and replacements to make things almost too confusing the track down.

Or maybe you did some of the replacements to get the sound working, I don't know, but you now have a bit of a mess I'd guess, and maybe start over or… whatever…
 
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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 responses, everyone.
 
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It seems that Apple's Yosemite Mac OS X 10.10.x often marches and keeps in step to a different drummer for a lot of things and for many users. But you'll have to admit you were doing some pretty non-Apple supported swaps and replacements!! :eek: :Oops:
 
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Oh sure, no blame on Apple here. It's just odd that A) the same hardware combination worked for Ubuntu even though B) it's a chip from another iMac and C) the only issue it produced was an audio distortion.
 
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2011 27" iMac, 1TB(partitioned) SSD, 20GB, OS X 10.11.6 El Capitan
Oh sure, no blame on Apple here. It's just odd that A) the same hardware combination worked for Ubuntu even though B) it's a chip from another iMac and C) the only issue it produced was an audio distortion.


Re-read my post. And you should notice I did put some of the blame on Apple. :(
 

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