Hi, I have a very frustrating problem on my 2013 Mac Pro - since upgrading to the Yosemite beta (latest version) changing a sound output device in the preferences pane does nothing, one time I boot up and everything is coming out of the built in speaker, another time it may come out of the line out but switching between the two or selecting a USB audio device does not route the Mac's audio out to that device, changing a selection does nothing. It's hit and miss where the audio output is routed to. I have posted messages in the 10.10 forum asking if anyone else is experiencing this and got no reply so presumably it's an issue with the Mac Pro and Yosemite? If anyone else is experiencing this problem can you please post a reply - thanks