I've got a late 2013 27" iMac running the latest OS X (Mavericks 10.9.1). When recording audio through a USB device (I've tried both a USB headset and a USB Mixer (Alesis iO2 + condenser mic) I sometimes get a very crackling recording. I've tried the same hardware on my 2011 Macbook Pro, running Snow Leopard, and it seems to work fine. A Google search is leading me to believe this is related to late 2013 Macs (specifically, those running fusion drives) and USB recording devices, but I can't quite see why this would be.

Has anyone experienced this issue before? The problem also seems to be quite random - I have had clear recordings as well as crackled ones, without changing any settings or unplugging anything. The only other thing I can think of is that the length of recording might be having an impact, but so far my tests have all been well under 1 minute.

Any suggestions welcome.

1 Answer 1


What software are you using? Have you tried increasing your overall Buffer Size and decreasing your Sample Rate? Also, are any hard drive intensive tasks running on your iMac simultaneously?

Edited to add.

  • I'm using QuickTime player to record my screen with a voice over, but I've also experienced the problem with Camtasia. I've tried changing the sample rate (although, I couldn't find an option anywhere to modify the buffer) but no luck. This is strangely looking like a problem relating to late 2013 iMacs with Fusion Drives: discussions.apple.com/message/24003292#24003292 Commented Feb 17, 2014 at 15:10
  • Hmm, seems so. Another test to perform is to try and just record audio in Garageband and see if you have any issues. Screen grabbing can be a taxing process and any frame drops would result in audio glitches. Seems a possible solution is to split your fusion drive into 2 drives, and reinstall the OS. Try Garageband first though.
    – elburzs
    Commented Feb 17, 2014 at 22:23

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