/Sounds/ like we have the same issue. (Roughly)
I'm using a 5600x and a 6950 XT, Win10.
I've noticed if I have a game running in the background (with sound on,) and I scroll through the Win10 Facebook app, or if I'm using YouTube, and make the controls appear on the video by mousing over it, I notice this CONSIDERABLE stutter.
Not only does the sound hiccup, (which is annoying,) but it feels like the video processing might as well. Causing maybe just a micro-stutter in the video output. (Video output as in, what's displaying on my monitor.)
I'm not pushing my 6950 XT all that hard, my game in the background is running at 60 FPS, and I only have a 60hz monitor.
Reinstalling drivers, over and over, even audio ones, have not proved successful.
I even increased my minimum core clock on my card which proved helpful ONCE. Then after a restart it hasn't performed the same way since.
I did notice though, that I uninstalled my AMD audio drivers and got the basic Win10 ones, with the increase of minimum clock speed, and that's what worked. It looks like I have AMD audio drivers again, so this could be the issue.
I'll retry my findings and get back to you.
EDIT: Yeah basic Win10 audio drivers didn't do anything.