Distorted Audio Coming from Speakers and Line-Out

Discussion in 'iMac' started by desktopia, Mar 4, 2015.

  1. desktopia macrumors newbie

    Joined:
    Mar 4, 2015
    #1
    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.
     
  2. strukt macrumors member

    strukt

    Joined:
    Aug 8, 2012
    Location:
    Norway
    #2
    Strange, but if the startup chime is okay the actual audio hardware should be working fine.

    Are you absolutely sure this is no software problem?

    What i you boot from an USB install disk, connect to Wifi and open up safari. Go to youtube or something. See if that sounds okay...
     
  3. desktopia thread starter macrumors newbie

    Joined:
    Mar 4, 2015
    #3
    No, I am not sure. I just booted Linux off a USB drive, and audio worked just fine. Odd that it works fine with Linux off USB but not Mavericks.

    Newest thought is the CPU I upgraded to and Mac OS X just won't play nice for some reason.

    Thanks for responding!
     
  4. DeltaMac macrumors 604

    DeltaMac

    Joined:
    Jul 30, 2003
    Location:
    Delaware
    #4
    Both of your clips are damaged, and play very distorted. You get about .5 second of audio, then .5 is ~off, then .5 second audio, then off, etc. If you are using THOSE clips to decide about your hardware, then that will be really frustrating.
    If that's all you have, and all your audio files are damaged in this same way, then you need to try some that you KNOW are good - I think youtube should be a great help for that.

    So, as already mentioned, try youtube
     
  5. desktopia thread starter macrumors newbie

    Joined:
    Mar 4, 2015
    #5
    Those are recordings of what my audio sounds like when playing YouTube clips. Obviously those are not the original clips, because neither Stars and Stripes forever not middle C sound like that.
     
  6. DeltaMac macrumors 604

    DeltaMac

    Joined:
    Jul 30, 2003
    Location:
    Delaware
    #6
    I REALLY do try to avoid posting dumb responses, but I definitely did on that one :D .
    It would help if I would both read, and understand your first post.

    If you have a non-Apple CPU now, then the hardware test may not run (I don't know) - but, ignoring that, have you tried your hardware test?

    Another choice is to test with Apple Service Diagnostic. You need the version 3S123 for your Early 2008 iMac. If the CPU is not an original upgrade, then same remarks as the hardware test - it may not run without errors because of the changed CPU - but may be worth trying. Finding the download (for Apple Service Diagnostic 3S123) is up to you, as Apple only gives those to authorized service shops.
     
  7. desktopia thread starter macrumors newbie

    Joined:
    Mar 4, 2015
    #7
    Haha no worries. AHD ran sans errors and I haven't been able to find ASD. The CPU is actually pulled from a 24" iMac— it's the 2.8 GHz model instead of the 2.4 originally installed. I'm going to try swapping the original CPU back in.
     
  8. desktopia thread starter macrumors newbie

    Joined:
    Mar 4, 2015
    #8
    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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