I've done a lot of debugging the past few days. First, the buzzing in my case seems to be caused/triggered by GPU (graphics) load rather than CPU load. I've tried running syntethic benchmarks and even keeping the CPU at 100% for a while results in no noise. Open a game however (or even scrolling in Chrome sometimes) and as soon as the load on the GPU goes above the idle 20% it starts buzzing.
Having used the old chopstick and paper roll to figure out the location of the noise it was clear that one of the chips under the VRM heatsink was buzzing. Given that this is all very confusing I've asked Amazon to send me a replacement, which they did and I got yesterday. So I moved everything to the new motherboard. There's still buzzing going on. Even more confusing, the buzzing on the new motherboard is coming from behind the OLED panel. I've since built the system a few times in each of the motherboards (still have the old one) and on the old one the buzzing is way worse and 100% coming from the VRM and on the new one whilst quieter it is still audible very clearly even when playing with sound on but it is coming from behind the OLED. Same cause/trigger, GPU load, not CPU one.
Even more confused I tried swapping around everything I had. The buzzing happens both inside and outside the case, so it isn't a grounding issue. I am 100% it is not the AIO pump causing the noise as that's on a very distinct frequency. I've tried using both straight to PSU connections and cable mod ones and there was no difference. Tried using a different PSU, the original one is a 750W EVGA and the new one I tried is an 850W NZXT. I've tried switching GPUs, the original one is a 2080ti and tried replacing it with a 1080 which only changed the frequency of the buzzing not the intensity of it. During this last part of the swap I've noticed something else, even in games, the buzzing isn't on a constant frequency although it is as loud throughout, the frequency seems to be FPS dependent. I've even tried using the lower PCI-E port on the mother board, same kind of buzzing can be heard from behind the OLED screen.
I've had AIO systems for the past 10 years, I know what a pump and coil whine sound like and this is neither. This to me sounds like a bad/overloaded/shorted capacitor, the sound is very electrical buzz like and not at all similar to coil whine which is on a higher frequency. I've tried taking a sound recording of it but it doesn't really come up on the mic (maybe I just have very good hearing?!). If someone could explain to me why the motherboard (which doesn't even have iGFX support) buzzes dependent on FPS although the GPU draws power from the PSU, I'd highly appreciate it, might provide me with further leads to investigate.
