iTunes AirPlay to AppleTV works perfectly; System Preferences audio output to AppleTV jitters horribly? Interesting one here, I have an iMac 2011 and a MBP 13" Retina 2013, the iMac works fine every which way, both are connected at 5GHz to my router, both running Mavericks.

My MBP will jitter and pop horribly when outputting audio to my AppleTV.  Audio output is fine when using Display Mirroring.  Audio is also perfect when initiating AirPlay from iTunes... unless I afterwards enable AirPlay from System Preferences in which case the popping starts again.

It can't be the router because my iMac doesn't have a problem with it.
It can't be the AppleTV because of the above reason.
It can't be the MBP because iTunes doesn't have an issue and when Display Mirroring is on it's fine.
What the heck is it then?

Can anyone think how I can output audio from the comfort of my couch to my AppleTV without having display mirroring on and without enduring horrendous bouts of skin-curling pops?
The problem stopped occurring since updating OSX last night to 10.9.2.

In the fix lists is one ominous line:
"Fixes an issue that may cause audio distortion on certain Macs"

Here is the support link for reference:
http://support.apple.com/kb/HT6114