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I've got a 2013 MBP-Retina with Cinema and Thunderbolt Displays (1x each). It used to be that the default audio output was one of the integrated audio devices in a display, and I could control the volume from the keyboard (or the slider) as usual. However, somehow the system has gotten into a state whereby the audio indicators change with the keyboard, but the actual output volume does not. I can change the output volume for a specific device from system settings, but the system volume controls seem not to affect it.

What's going on, and how do I get back to normal?

  • I have several bugs open with apple where the audio stays with the internal speaker even when a thunderbolt or miniDP monitor is connected. Have you checked the sound prefs to be sure the system output is going to the Cinema Display currently? – bmike Feb 11 '14 at 0:07
  • Yep, it's going there. I was able to get the levels set kinda in the middle, and then after a reboot the keyboard buttons seemed to set the overall system level, so I guess I can live with that. It just seems like the global volume control should always directly affect whatever the current device is. – Ben Collins Feb 11 '14 at 3:25
  • Aah - the system stores volume level(s) in NVRAM, so you might try clearing that and setting your preferred output levels. I could see you might have discovered a bug where the system reverts to internal levels after a reboot, not preserving (or perhaps preserving for too long) the settings for other sources? – bmike Feb 11 '14 at 14:41
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I had the same problem and was able to fix it by running this from the command line, which unloads the audio kernel:

sudo kextunload /System/Library/Extensions/AppleHDA.kext

When I load the kernel back up, as indicated in the link below, the problem comes back.

Also see "Restarting sound service?".

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