I found and solved an issue with a crackling/buzzing sound coming through speakers/headsets that's related to using the middle PCIe x16 lane for your GPU. 

If your GPU is more than a single slot in width it will cover the Sound Blaster Audio capacitors which in turn creates a loud 'buzzing' sound depending on the power draw of the GPU. I spent the better part of month trying to figure out the cause, until finally adjusting the max GPU draw and seeing that it affected the level of interference I was getting through anything connected to either headphone jack. I moved the GPU to the upper most slot and the buzzing stopped.

Hopefully this helps anyone who has this issue.