Q: USB Audio on 27" Cinema Display doesn't work on 27" iMac

I have your exact setup, and I must say it's awesome. I'm not sure it could get any better than having two 27" screens.

I use a pair of external speakers, so I didn't notice this problem. I decided to try it just because I saw your question, and it definitely doesn't work. As soon as I click on "display audio" it goes right back to the "internal speakers" option.

Now if you disconnect your headphones or external speakers from the headphone jack of the iMac, it will start to work. It's probably a bug that will get fixed in a software update later on.

thanks for posting that. I've had the same issue in the past. unplugging the headphones will enable enabling the usb audio

however, it's unfortunate that multiple speakers can't be used. i.e. my line out, my headphones, AND the usb audio for the LED display series... hrm

thanks!
Ben

I had this problem with USB SoundSticks. Here is your solution:

Delete the com.apple.soundpref.plist from the *MAIN LIBRARY>PREFERENCES* - (not the users library PREFERENCE folder).

Again, in the same *MAIN LIBRARY>PREFERENCES* folder, go into the AUDIO folder and delete com.apple.audio.DeviceSettings.plist and com.apple.audio.SystemSettings.plist

Reselect the sound device you want as your default in the Sound Preference Pane.

Restart your computer.

And PRESTO!!!! works like a dream.

Same issue here, except via a laptop instead of an iMac. Brand new LED 27" Cinema display on a MacBook Pro. Plugged in, shows the "Display Audio," selecting it works. Plugging in headphones switches back to the headphones automatically, but unplugging them leaves the output on "Internal Speakers," rather than reverting back to "Display Audio."

Tried the fix put forward by @reichea, with no joy.

There's a lengthy thread about this exact problem (currently 11 pages long) here: <http://discussions.apple.com/thread.jspa?threadID=2611014>.

In short, though, as of 2010-12-06, Apple has provided no solution.

The easiest temporary workaround is to unplug the display from the electrical outlet and plug it back in. For most people, this “solves” the problem for anywhere from a few hours to a week or two.

Thanks for the tip.

Would not have occurred to me to unplug the headphones to enable Display Audio over USB.