I figured a rather strange way to remove temporarily the crackles from the sound when playing iTunes and other stuff and using an AMD processor on my ECS mobo, it is a a780gm-a, with a IDT sound chip, it says it is a SigmaTel 92HD206X, vendor id 0x83847645 subsys 0x10192816 revision 0x100402, it reads 00:14.2 Audio device : ATI Technologies Inc SBx00 Azalia (Intel HDA) [1002:4383] trough lspci -nn, it just might work for other as well, here is how it works:
1.- open Terminal.app
2.- type "yes > /dev/null" w/o quotes and hit enter
3.- open iTunes/Youtube/other media/games and test
funny huh? idle cpu gets crackles and busy cpu doesn't ... really weird.