Question Gigabyte Z390 Gaming X making an electric buzz sound

Oct 1, 2019
This problem has been puzzling me for over a week, and I have finally given up trying to solve it by myself.

I recently built myself a PC (full specs at the end of the post). Everything seemed to be working correctly, so I went ahead and installed Windows 10. As soon as I connected my headphones to the audio out, I noticed some weird interferences. Shortly after, I realized that a weird electrical buzz was coming from inside my PC. The sound was directly correlated with the interferences, as such I concluded that it is the cause. Now, what could be making that sound? Here's everything I've concluded up until now.

About the source of the audio interferences:
The electrical buzz is somewhere near the IO shield. I suspect this is the reason why there are interferences in the mobo audio out. Furthermore, if I connect my headphones to the case audio out (which is far away from the IO shield), there are NO interferences to be heard. As an additional —maybe even fun— bit of information, if I connect a cable from the mobo audio out to the case audio in, I DO get interferences in the case audio out. It's as if they get transferred through the cable.

About the source of the electrical buzz:
As stated, it seems to be coming from the area near the IO shield. There are several components there:
  • Case fans and CPU fan: these are NOT causing the buzz, since I disconnected them, and the buzz was still there
  • The CPU: I can't exactly pinpoint if the sound is coming from it with 100% certainty, but it doesn't appear to be the case
  • Some components of the mobo itself near the CPU: this is my current hypothesis
What does NOT make the mobo buzz:
  • Booting into the BIOS
  • Booting into an Ubuntu 18 live USB
However, it does buzz when booting into a Windows installation USB, and when booting into Windows, of course. This makes me think that it must be Windows doing something with the hardware to cause the buzz. To discard any rogue driver issue, I tried booting into safe mode. The buzz was still there. I honestly am not sure what to make out of this, other than concluding that my hardware can definitely function without buzzing, under certain conditions.

What makes the mobo buzz HARDER:
  • Increasing CPU usage
  • Moving the mouse around (might be related to CPU usage)
The amount of buzz seems to be directly correlated with the CPU usage. In fact, setting the power management plan to High Performance makes the buzz way worse than on Balanced. Here is a recording of the interferences caused by the buzz. The first ~9 seconds are with "Minimum processor state" set to 5%. Then, I set it to 100% and put it back to 5% after several seconds.

Now, I've thought that maybe it is a power issue. However, I've got no known good PSU to test my build against. In fact, I've got no replacement component for anything to test if it is the culprit. Given this, and given that an Ubuntu 18 actually does not make my machine buzz, and neither does booting into the BIOS, I'm trying really hard to solve this without replacing any component, since it seems definitely possible.

Here are my full PC specs:

Further info which might be useful:
  • I connected the 8-pin power connector to the CPU. I left the 4-pin not connected, given that my PSU doesn't provide a 4-pin CPU cable.
  • I did check that there are no loose connections
  • Temperatures look pretty okay to me, CPU is staying around 35~40ºC
  • Enabling or disabling XMP in the BIOS has no effect on the buzzing
  • I have also tried to fiddle around with the CPU settings in the BIOS, especially the C-State options, to no avail. I am not very savvy when it comes to this, however.
I think that's all for now. Any input will be greatly appreciated! I have some more ideas, but it feels like I'm just doing random things hoping something will work...