After upgrading to El Capitan I've lost the ability to adjust the volume of some of my connected speakers. Both the built in speakers in my display, connected through DisplayPort, and my DAC connected through USB. I do get sound out, I just can't adjust the volume under System Preferences -> Sound -> Output (it says "The selected device has no output control"). However I can adjust volume for internal speakers and also a Logitech USB headset. (That USB headset though, does not work reliable since the upgrade.) I've tried… …rebooting my MacBook Pro …resetting NVRAM …connect USB DAC directly to MacBook Pro …sudo killall coreaudiod …using Audio MIDI Setup …rebooting into safe mode but so far no success. I assume this has to do with El Capitan since it worked without issues in Yosemite yesterday, but I'm not sure. I know that similar kind of problems have occurred before with upgrades to Yosemite and even Lion. But I've also seen scattered reports of some audio issues in El Capitan, especially when connected through USB and HDMI. I've also seen reports saying this is how it is supposed to work but, that you should not have software output control on external sound cards like USB DACs. But since I've always been able to do this before I think it is a regression if it is done by design. Anyone else having the same issues?