Wesleyp :
I Have tried the furmark test with the headphones plugged in and its still present
Ok, that's good, we can definitively remove the PSU and in fact any power issues from the list.
Unfortunately, that makes mobo issues a bit more likely. Here's a few steps you can try to see if they help, try one, test, and then move on if it didn't help.
1)First go to
http://www.gigabyte.com/products/product-page.aspx?pid=4968#dl and install the realtek, and then after the creative drivers (after uninstalling both) and see if that helps.
2)After that, shut down the PC, unplug it from the wall, and then hold down the power button for ~30s. Plug back in and then turn it on an test.
3) Reseat the HD Audio header and make sure that it's as far from any other cables as possible
4) Try checking the op-amp for damage, and if you have a spare (some were sold with multiple op-amps to allow for different listening styles), try another op-amp. Just be very careful because they are sensitive to static