A few times in the past I've tried to use "supported devices" with my Mac and newest version of Lync via USB. This didn't work since you still needed to register the devices independently through the device itself (Polycom CX600, Snom 821, etc.) instead of through Lync like you can with the PC version... (that's another sad story of Microsoft's software claims!)

To get to the root of this issue, now that I no longer use any USB connected devices with Lync, I cannot get the software to STOP adjusting my system's audio levels upon incoming calls. I currently use a standalone phone device for phone calls. The software still shows a "Custom Device" attached and the only selection under "Audio Device Settings" and there's no way to de-select it or turn it off. 

Any ideas?

Hi,

Please restart the PC or uninstall and install the Lync client to check the issue again.

I have done both of these. Neither work. I've also tried to manually remove files scattered around the OS by this app, even going so far as to create another OSX user profile and identifying which files were created or modified. I don't want to have to re-create my user profile to get the app to start functioning correctly.

Are you running Skype by chance? It has a similar behavior.

The following links my point you in the right direction:

http://www.mac-forums.com/forums/os-x-operating-system/236819-macbook-air-how-disable-osxs-auto-switching-volume-when-using-headphone-jack.html

https://www.bartbusschots.ie/s/2007/12/01/stop-skype-messing-with-your-volume-behind-your-back/