HDMI buzzing issue with gaming PC

I've recently setup a home theater / gaming pc for use with a projector in my living room. Everything is great, but there is an irritating buzzing sound coming through speakers when trying to play a game on my pc. The connection goes as follows:


PC (asus Z87-PRO) > Marantz SR6008 receiver > projector


I was originally sending both audio and video through hdmi from the pc to the receiver. In trying to narrow down the problem, I switched to audio out through the optical spdif. Even with hdmi as only a video source, there was still buzzing. I then sent the video through hdmi directly from the PC to the projector. The only direct connection to the receiver was the optical cable. I thought the problem was solved, but it turns out the buzzing was just now at a lower volume. Removing the optical cable didn't fix that either (zero connections between the receiver and anything else), which seemed crazy. The only way to remove the buzzing altogether was to plug my pc and projector (also tried with a monitor) into different outlets than the receiver. When power for each device was coming from different outlets, I tried the hdmi connection through the receiver again, and the buzzing returned.


It seems to me like the buzzing is originating from my pc, but only appears in conjunction with my receiver. When I'm idle in windows, there is no buzzing. This only occurs when I doing something cpu intensive. It doesn't really occur during video playback, but there is some slight crackling/buzzing when launching programs and transitioning between things. To start the buzzing I would just load up Far cry 3 and sit at the starting menu. Because of this I believe it's directly linked to my graphics card or power supply. I have done a few searches and seen people with similar problems and it always seems to be a grounding issue, but nothing exactly specific to my issue (which I need, because I am currently ignorant). Would someone with more knowledge than myself mind helping me out? It would be greatly appreciated. THANKS