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Barraccus Author

Level 1

6 points

USB Audio Problems Late 2013 iMac - Clicking / Popping / Dropouts

I am having audio clicking and popping issues with a brand new late model 2013 iMac and a USB 2.0 multi-channel audio recording interface. Here is what I have learned so far:

Clicking and popping is occurring in both directions - playback and recording. I am not having any issues with internal audio, so this was easy to verify.

The same issue appears in many threads in Apple Support Communities and in various recording/pro audio forums, so this seems to be a common issue.

The issue is independent of the audio interface that is used. (I am using a brand new Focusrite Scarlett 18i20 that I purchased specifically to use with my new iMac, but the forums report the same issues for a variety of other interfaces and audio devices.)

Five potential root causes are mentioned in the various forums:

1) USB 3.0 compatibility issues - poor backward compatibility or other issues

2) Fusion Drive activity - artifacts caused by drive "swapping"

3) OS X version - newer versions may be worse than old versions

4) App Nap - ?

5) Driver issues

Potential short-term solutions include:

1) Change driver - The "Class Compliant Mode" app (that I downloaded from the link on the Focusrite website) improved the issue for me, but clicking and popping occurs every few seconds instead of constantly.

2) Exchange the Fusion Drive for a conventional 7200 RMP hard drive - Forums report that this does not fix the issue.

3) Install older version of OS - Forums report that this does not fix the issue.

4) Disable App Nap - Forums report that this does not fix the issue.

5) Belkin Thunderbolt express dock - Forums report that a Thunderbolt hub with USB gives excellent results, but the only one I am aware of is the Belkin one which is ~$300. (I will not pay $300 to fix thousands of dollars of new equipment that should not need to be fixed!!!)

6) Apple Care's advice was an SMC reset (essentially a reboot), which clearly did not work. The person that I talked to was not aware of this being a known issue.

I am at a point where I need to decide whether or not to get a refund for this iMac since my primary reason for getting this new computer was recording. So...can anyone help to answer these questions:

Has Apple acknowleged this issue? If so, has Apple committed to fixing this issue via a software upgrade or have they admitted that this is a hardware limitation that is not fixable?

Has anyone found a free or inexpensive workaround (i.e. not the $300 Belkin dock) that completely elimiates this issue?

iMac, OS X Mountain Lion (10.8.5)

Posted on Nov 30, 2013 8:38 AM

98 replies

jalfred

Level 1

0 points

Apr 9, 2015 10:22 AM in response to Alric

+1 with Retina iMac. But I have 512GB Flash Storage not a Fusion drive. Audio Engine D1 connected w USB.

jbauer

Level 1

6 points

Apr 9, 2015 10:30 AM in response to jalfred

Hi jalfred,

I called Audioengine and they suggested that I change my settings in the Audio MIDI Setup app - I changed to 48000.0 Hz and 2ch-24bit Integer, and I think my problems have been solved. Let me know if this helps you!

- Jon

jalfred

Level 1

0 points

Apr 9, 2015 10:40 AM in response to jbauer

Thanks Jon. I just switched to the old optical cable that I had with the addition of a mini adapter. Seemed to solve as well. I also went in and changed the midi set up. So far so good. Before the switch, anytime an email or message would come through, music would static and mute for a second.

On my old Mac Pro, I just dealt with the click between tracks. Wonder if the midi switch would have solved that.

-john

Alric

Level 1

85 points

Apr 9, 2015 11:23 AM in response to jbauer

This did it for me (so far)! Thanks Jon!

Jul 4, 2015 6:29 PM in response to jbauer

MacBook 2011 Early Spring checking in here. It worked perfect for me. Been suffering the clicks and pops which were super annoying. I'm set up to 96/24

bisigulo

Level 1

0 points

Dec 3, 2015 9:58 AM in response to jbauer

Imac 27 i7 3TB Fusion drive with Focusrite Scarlett 18i8 and Yosemite. I had huge digital distortion after 3 minutes of audio playback. Today I tried to remove GenericUSBXHCI.kext from system -> Library -> extensions.

Reboot and ... it's work great!!! 🙂

But... what is GenericUSBXHCI.kext?

grynch

Level 1

8 points

Feb 19, 2016 7:37 AM in response to Barraccus

I exchanged my iMac with a fusion drive for an HDD iMac - the issue persists - so it's not just the fusion drives. Brand new iMac, 1 tb HDD - audio dropouts with anything going through my Roland Studio Capture. The Roland works great on my MBP. Latest Roland drivers for El Capitan - new USB cable, cranked the buffer settings on the Roland - still getting "pop" sounds due to dropouts.

I cannot believe Apple will not acknowledge this.

Sep 27, 2016 8:16 PM in response to Barraccus

Ive been dealing with pretty much the identical issue for about roughly a year now on a "mid-2011" 27" iMac. Ive gone through 3 different audio interfaces initially assuming they were the fault, but now its clear to me that the computer is blame finally. Not happy it about it to say the least considering this thing set me back 2k and is my only computer solely purchased for graphics and audio recording. I will get small loud transient pops while listening to music in iTunes or via the internet, as well as in recording software. It completely distracts from the audio content being played and is not good for my monitors either. SMC resets never solved the issue, or switching to different USB ports, etc. Doesnt make a difference. I can also change to a higher res and bit rate to no avail. Still get the popping regardless.

The strange thing however? I never encounter this issue while listening through the iMacs built in speakers. Only when I interface a thunderbolt, FW, or USB interface.... which Ive tried all 3 of. The only one that seems to not have any issues is my ancient MOTU Ultralite MK1 through a FW 800>400 adapter plugged in the back of my iMac. But Thunderbolt and USB interfaces all suffer from this issue and its highly annoying. For a while now, Ive almost come to the conclusion that the peripherals on the back of the iMac may be defective or something related to that part of the computer.

Its honestly baffling, and Ive still yet to find a solid solution.

USB Audio Problems Late 2013 iMac - Clicking / Popping / Dropouts