Hi, I just had that problem with a new build though. This is what I found to fix it, setting the cpu performance setting to power save (instead of standard or performance) I don't know if this would help you or not.
(From my thread) "I was trying different settings with ASRock A tuning (asrock motherboard utility) and found the standard setting gave me drop outs, performance setting instantly killed the audio engine and power saving setting everything is working. I ran the audio tutorial file through 2 times without a dropout. Soundcloud, youtube and Itunes are playing without dropouts."
I7-4770, Asrock Z87 extreme4, 32g Gskillram, Samsung 840 120g SSD, Asus 210 silent video card, LG GH24 dvd reader /burner, Coolermaster M2 620w bronze PS, Coolermaster 120m CPU cooler, Fractal design R2 case, WD 1tb hdd WD1002FAEX. Windows 8.1
Roland VR-09, Roland GAIA, Novation Impulse 25, Alesis QX25, Arturia Minibrute, NovationBass Station II. SONAR PRO