Q: external usb microphone not working with FaceTime and mac mini with os x Yosemite

I filed an official developer bug complaint on this issue about a year ago maybe.  I got a notice back saying it's a known bug.  Great.  Still not fixed.

Apple will not make it a priority unless they hear from the public that it's a priority.  You can give your feedback at the link below.

Maybe I suggest that EVERYONE who posts after this, include the link and the need for the public to have their voices heard.  My post will get buried soon enough.

http://www.apple.com/feedback/macosx.html

its fixed in El Capitan beta

https://www.youtube.com/watch?v=V3FnpaWQJO0

Are you still using the Livechat LX-6000 on your Mac? I just recently got it (today) and can't get it to work at all. At first I noticed my Mac recognised the specific headset and had some driver for it but after unplugging it once it only shows up as a generic USB Mic / Speaker.

This helped me.  What I can't figure out is why it used to work and now it doesn't.  I didn't do anything different.