Bad processing noise coming through speakers

[AdamKenshin]

Hey all, recently I built myself a new PC. I never had this problem with my old one, but now when my speakers are plugged in, I get a lot of noise associated with the processing units inside the computer. For instance, any cpu usage, i get some mild electronic noise with an on/off characteristic that seems in line with demand put on the cpu. The noise from the GPU is especially bad; if I load up a game, it becomes unbearable.

However, if I have my headphones plugged in, the noise is almost non-existent. If I turn up the volume on my headphone amp, then I can hear it, but at normal levels it imperceptible.

I'm currently running an i3-6100, on a Gigabyte z170-HD3. PSU is a Corsair modular unit (forget exact model). I've tried both onboard sound, and using my older PCI-E Soundblaster card. Both are exactly the same.

The sound is running out from the PC in to a headphone amp - I've got the speakers (Behringer Truths) and headphones (Beyerdynamic DT 990 Pro) running from the amp. Again, I had this exact same setup with my last PC (and I was using the SB card).

I've tried turning all the C states off in the BIOS, which made it bearable, but anything that uses the GPU makes it awful. I've got a Thor line filter coming soon..... so hopefully that will work. But if not - any ideas what the hell is happening?

(oh, and no wireless mouse or KB)

 

[AdamKenshin]

After seeing some of the other issues on here that were similar, I went out and bought a ground loop isolator. Even though the bloke at the electronics shop said it wouldn't work, it completely fixed my problem. Now there's 0 processing noise coming through the speaker.