Question Buzzing through active monitors - help

[squidmasteroftheuniverse]

I've been encountering a buzzing sound through my monitors when using my PC, but it worsens when gaming. It sounds like a combination of ground loop, and RF interference. I'm getting my audio via a USB interface, with a set of active monitors plugged into that. I don't get this problem with my wireless headphones or onboard sound.

I've tried changing the following;

• Different USB interface
• Different active monitors
• Different speaker cables
• Different USB cable (from interface to PC)
• Different plug for power strip
• Different power strip
• Different IEC cable (PC)
• Plugged PC/Monitors/interface into different wall outlets

I'm running out of ideas. One very strange thing is that when I unplug my PC with the speakers/interface on, the speakers emit a loud, low, prolonged booming sound. It then goes away when I plug the PC IEC cable into a power outlet.

I'm guessing it could be my PC's PSU, which would explain why it gets worse when my GPU gets working. Has anyone else got any ideas?

 

[squidmasteroftheuniverse]

Just an update - my monitors (Behringer Studio 50USB) don't make any unwanted sound when they're plugged in via USB (with, to be fair, the interface unplugged). Also I don't get any unwanted sound through headphones plugged into the audio interface. So I think it must be bad cables (even though I've used a couple of different ones). I'll order some high-quality balanced TRS cables I think.

 

[ElectrO_90]

Ground Loop isolators maybe better on that equipment than the one you are using.