Static Burst playing through USB Audio Interface

[jazzer15]

I have a late 2009 i7 27 inch iMac currently running Mavericks 10.9.5. The problem I am outlining below is not exclusive to Mavericks as it has been a problem that I have not been able to solve since before upgrading.

I have a pair of Klipsch computer speakers with a subwoofer that I have connected to a Mackie Onyx Blackjack audio interface that is in turn connected to my iMac via USB. The computer speakers have a 1/8 inch jack and I have used a "y" converter with 2 quarter inch plugs that go into the input of the audio interface. Sometimes, but not always (and frequently enough to be very annoying), when I begin playback of audio through, for example, iTunes or Garageband, or if a notification sound is made, I will get a burst of static noise. With music, this will usually last a couple of seconds or so and then correct and start playing properly.

When I use the computer's internal speakers or if I plug the computer speakers directly into the iMac headphone jack there is no problem. I have swapped out the "y" cable without any effect. Has anyone heard of a similar issue or have any ideas what the cause could be?

 

[BrianBaughn]

I've seen this sort of thing before but don't remember a fix.

Mackie's site doesn't say that device is compatible with Mavericks but that doesn't mean it won't work properly.

Have you tried to trace the origin of the issue? Such as:

Do headphones plugged into the Mackie do the same thing? Does changing the power outlets that the various devices are plugged into make a difference? Tried "Ground floats" on the various devices?

 

[jazzer15]

Brian,

Thanks for your reply. Although the Mackie site doesn't say that the device is compatible with Mavericks, you are right that it should work properly. I spoke with someone at Mackie to confirm and they said they have used the device with Mavericks without any problem although it may not technically be supported.

Yes, same issue with headphones. What is a "ground float" ? Haven't tried that because I don't know what it is ;-)

 

[BrianBaughn]

Brian,

Yes, same issue with headphones. What is a "ground float" ? Haven't tried that because I don't know what it is ;-)

I think that's my hillbilly term for one of these.

I had a noise issue with some powered monitors and those fixed it. Worth a shot.

In the meantime, have you tried different settings in your "Audio Midi Setup"? Sample rate may be the only thing you can change. Also, have you tried unplugging and replugging the Mackie's USB (turn off your speakers before doing that) to see if that has an effect?

 

[jazzer15]

I think that's my hillbilly term for one of these.

I had a noise issue with some powered monitors and those fixed it. Worth a shot.

In the meantime, have you tried different settings in your "Audio Midi Setup"? Sample rate may be the only thing you can change. Also, have you tried unplugging and replugging the Mackie's USB (turn off your speakers before doing that) to see if that has an effect?

Ah. I can try those, but doubt it will be much help. This isn't a typical hum or static noise issue. It is actually a loud burst of white noise that only lasts briefly when I hit play on software and only occurs sometimes. This has been an ongoing issue for a very long time. I have unplugged the Mackie's USB, gone through operating system upgrades and reinstalls, done various computer resets, etc.

I will try playing around with some of the settings again. Thanks again.

 

[JustMartin]

A number of people were complaining about this some time back. Far as I recall it seemed to be a Mavericks bug connected with usb audio. Complaints seem to have stopped with Yosemite. So, might be worth doing a search of the forums and/or an upgrade.

 

[jazzer15]

A number of people were complaining about this some time back. Far as I recall it seemed to be a Mavericks bug connected with usb audio. Complaints seem to have stopped with Yosemite. So, might be worth doing a search of the forums and/or an upgrade.

Well, I upgraded to Yosemite yesterday. Things looked good for a short while, but unfortunately I'm still getting the intemittent bursts of white noise at the beginning of playback. It happens just frequently enough to be a big pain, but no so often that it is completely unusable. I didn't do a clean install, but i had done that with Mavericks previously and it didn't help. Going to play around with settings and, if I can, find another computer to hook the Mackie up to just to make sure it isn't hardware related.

 

[jazzer15]

I have now had my assumption verified. I hooked the audio interface up to an old laptop running Windows XP and there is no problem. So it's not the interface. And I have fooled around with the few settings available on the Mac with no luck. Now I need to find another Mac to try so I can figure out whether it is peculiar to my iMac or if it is consistent among Macs in general.

I thought avoiding these weird issues is the reason people buy Macs instead of Windows machines?

 

[BrianBaughn]

It does seem like there's something wrong with you Mac. If you discover that the device works well with a different Mac I'm thinking it would be difficult to pinpoint the problem.

If this noise is being generated by the initialization of audio there might be a stupid sort of workaround (you may have already tried it). If you have an audio app such as the free "Audacity" open it and create a new file by generating some silence. Start playing the audio file and then click the pause button. In this way, you have engaged the Mac's audio and it remains engaged even though the file is paused. Leave Audacity running like that in the background and use another audio application to see if the noise problem still exists.

 

[boast]

Based on my Linux experience, it sounds like the mac is putting the usb port or the device to sleep. And as it wakes up to play the sound you get the static noise.