I've been having some issues eradicating interference from my computer audio setup. As of now, I'm using my desktop computer and a 30" CCFL-backlit computer monitor to play games and perform other tasks. For audio, I have a Fiio E07K connected to the desktop via USB, which I have then connected to a sound mixer via an RCA - 3.5mm connection. The mixer then provides a signal to 2 KRK Rokit 5s over short XLR cables. All these devices are connected to the same power strip, which is in turn connected to a grounded UPS.
The problem I've been experiencing is actually twofold. Firstly, I found that whenever my monitor was turned on and the backlight was on, I could hear a ton of interference/hum through the speakers, regardless of the output level of the computer. I ended up marginalizing this problem by removing the ground pin from the monitor's power cable (which had the most profound effect) and the second thing I did was increase the E07K's volume output to max and its gain to +12dB. At this point in time, I cannot determine a difference between when the monitor is on and off.
My second problem is slightly more troublesome, and I'm not really sure how to fix it. Whenever I'm doing something GPU-intensive and the graphics card has ramped up in its utilization or power consumption, I can hear interference that is almost definitely caused by the graphics card. I get different styles of interference based on the scene the GPU is rendering in the video game, I can hear interference when I move my mouse cursor around on screen, and when the GPU is being utilized at 100% by Folding@Home or a mining program, I get a constant hum from the speakers.
I've been considering getting a ground-loop isolator for ~$13 from Amazon so I could isolate those channels coming from the DAC, but I don't know if that would help. Does anybody have any suggestions for me on what I could try or what I could buy? It's really frustrating to not be able to listen to audio without a great deal of interference, and I'd love be able to fix it!