I just finished my second build everything is working, except for my speakers making short scratchy noises every 4-6 seconds. I have an Gigabyte 990fx-ud3 rev. 1.2 with onboard audio, I just downloaded the latest driver so that isn't the problem. I can only think of two options now. 1. Interference from other devices though I think that is unlikely as there's no scratchy sounds when the speakers are running idle. 2. onboard audio does not get enough power/information or something.. not quite sure but I notice a slight fps drop in games when the scratchy noise appears..
I have an amd fx 8120 (not overclocked)
8gb of corsair vengeance 1600mhz ram
a XFX 7850 along with a pro series 650w psu
1 tb seagate barracuda hdd