iTunes 12.1 - Pop and static when playing music

I've just upgraded to the latest version of iTunes (12.1.0.71) for Windows -- the first proper 64-bit edition of the software for Windows -- and now all my music has pops and clicks and other static when playing.

I have an extremely well-specced machine.

• Intel Core i7


• NVIDIA GeForce GTX 760


• 16GB RAM


• Windows 8.1 64-bit

Latest drivers. I even ensured I reset my machine after the installation. It happens with all music files, from MP3 to AAC.

What's going on? Every other music player on my system plays the same files perfectly fine.