Troubleshooting Audio Interference (Buzz/Hum/Static)

I'm planning out the next iteration of my home studio, and one thing I really want to fix is the humming/buzzing that are constantly on my Kali speakers. I've tried different outlets/areas of my place and it's not an issue with the actual speakers or my interface, so I assume it has something to do with the grounding or some kind of electrical interference. However, I do notice that the buzzing gets worse when the graphics card of my PC is being utilized - such as when I'm playing most games. Sometimes it goes away, sometimes it stays. So I guess I'm not sure if it's the electrical circuit its on, or if its an issue with the power supply or something, but its always done this. Is anyone familiar with or know which kind of ground loop isolator or power conditioner I could use to maintain a clear and quiet audio feed without any electrical interference or grounding issues? I'm not terribly familiar with how all of it works or where to start looking, so any help or advice is greatly appreciated.


I purchased a used tube preamp over a year ago from a reputable seller, assuming he performed detailed listening of which he later admitted he did not. It would've been a consignment sale for him! I tore my whole system apart chasing a high level distortion in right channel, it was the preamp as I suspected all along but had to be confirmed. He paid for the repair. You could have something like that going on that your not be aware of. 

I just went though this on my system. For mine, the noise was generated by the video card. I have a usb from the computer to a RME adi-2 dac. I tried ferrite beads everywhere, but no significant improvement. I had it in my mind that the video cables were transmitting this noise, so I got shielded ones.

No point in telling everything I tried. The happy ending came when I remembered that the dac has a toslink/optical socket. I hooked up the optical cable, configured the computer to send sound to the spdif output, and the noise was completely eliminated.

I believe what is happening is that the inside of the computer is filled with the emi emitted by the video card, and it rides on the usb cable to the DAC. I think the dac should have done a better job of rejecting emi, but it is what it is...

I have ordered a gadget that claims to isolate away emi on a usb cable, so I will see how that goes. Thing about the spdif link is that this uses the clock on the computer rather than the clock on the dac, so it may be subject to jitter or clock inaccuracies. It sounds ok to me as is, but that question is floating around.
I wish I had known that the emi was in the usb wires from the computer, as I have had this issue for years over other devices, but only with the rme device did it get loud enough for me to go after it in with my full attention.

I received the gadget today, a SZSEVSIOT usb power blocker, to  the tune of $65 before tax. It did the job--using it today has eliminated all of the video card noise--just as silent as the toslink. Wish I had one years ago...