I've looked through the forums, and I wasn't able to find anything that covered this issue. If I overlooked something, I do apologize, but this issue is getting pretty frustrating. At any rate here's my system:

ASUS Maximus Extreme (with SoundMAX II HD Audio)
Intel Core 2 Quad Q6600 Kentsfield
Corsair DDR3 1333 (4GB)
EVGA 512 8800GTS 256MB DDR3 PCI-Express
Vista Ultimate (32-bit)

My issue is this: whether I'm listening to music or gaming there's constant crackling and popping in the audio. I've tried two different sound cards and the issue sticks around. I've updated all drivers and/or BIOS for all of my hardware too. Now it seems that the first PCI-e slot, PCI slot and PCI-E 16x are on the same bus because they all share the same IRQ. I thought that may be the problem, but I tried putting the audio card in the other PCI-e slot and it still goes rice crispy on me. I thought that you could manually assign IRQs, but after doing some research I found that's not the case in Vista. Anyway I'm hoping someone else has had the same problem, and has fixed it as this is becoming increasingly frustrating. Thanks for all the anticipated help!!

I have a similar problem with intermittant crackling on the sound on all sources. Seems to have no relation to anything else that I am doing on the pc and I spend most of my life on it.

ASUS maximus extreme with soundmax 7.1 hd audio
Intel core 2 quad QX9650
OCZ ddr3 (2GB)
8800GT
Ageia physx
Hauppage hvr1300
Vista home premium