[Solved] Speakers buzz / hum as soon as PC receives power

[TheTornado121]

Hello experts! I really need your help with this.

I recently custom build a new PC. Motherboard is an ASUS H170-PRO. The problem is that when I connect my speakers through the front or back audio jack there is a loud buzzing noise / hum. The interesting thing is that the sound is still there when the PC is shut down. When I unplug my power supply the hum is gone. When i plug it in it starts quiet and when I flick the switch on the back of the PC it gets loud.
My speakers are a Home Entertainment System from Sony (DAV-DZ280).

What I've tried:

- Software:
Messing around with drivers I found out that disabling the Realtek driver reduces the hum to the "quiet level" but I have no sound obviously.

- Hardware:
I tried different cables and connecting the speakers in the weirdest ways possible like interconnecting a monitor, my TV or an RCA adapter. Nothing worked. In whichever way the speaker receive an input, they hum.
Using the USB adapter of my Logitech G430 the hum goes to the "quiet level" which would be kind of tolerable but the sound quality is quite bad for whatever reason so that's no solution for me.
Also tried plugging the PC and speakers into the same wall outlet to maybe prevent a ground loop but no luck.

Interestingly enough when I connect my G430 with the audio jack, there is no hum so I assume it has to do something with the speakers and the power connections. I never had any problems with audio using my old laptop, my TV or various consoles. My mobile phone also works just fine.
I just realized that my speakers give off a quiet hum when I connect my TV but this is barely audible if you turn them up all the way so no problem here. Is there something up with my speakers? But like I said, never experienced any problems before.

Thank you for ANY help. I am really at the end of my knowledge on this one.

TheTornado121



FOLLOW UP: The Issue is resolved. It was indeed a ground loop as pointed out by americanaudiophile. Thank you very much.
The solution came to me when I disconnected all cables from my PC and found that when disconnecting the monitor, the hum disappears. I held together the monitor HDMI and the audio system's input cable and the hum came back. I then "ungrounded" the monitor and the hum was incredibly loud. I deducted that it must have to do something with the grounding and bought myself a ground breaker (this one, to be specific: https/www.amazon.de/FGA-35-Massetrennfilter-Entst%C3%B6rfilter-Klinke-Isolator/dp/B00BBE59WS/ref=sr_1_1?ie=UTF8&qid=1476566934&sr=8-1&keywords=klinke+filter). And the hum is gone, audio quality didn't degrade. I am very happy.

Thank you again,
TheTornado121

 

[americanaudiophile]

You may be getting a ground loop when the Sony system is connected to the PC. This is caused by having more than one ground connection between them. One is the audio cable connecting them. If you could use an optical connection between them this would break that connection. The other possible ground connection is the grounds on the power cords of the the Sony and PC. You could use a three to 2 AC adapter to break the ground on the Sony or try a different AC outlet for the Sony.
There are audio ground breakers that could go in between the PC and Sony.
http/web.mit.edu/~jhawk/tmp/p/EST016_Ground_Loops_handout.pdf
https/www.amazon.com/PAC-SNI-1-3-5-3-5-mm-Isolator/dp/B001EAQTRI?ie=UTF8&ref_=pd_bxgy_e_img_y

 

[TheTornado121]

You may be getting a ground loop when the Sony system is connected to the PC. This is caused by having more than one ground connection between them. One is the audio cable connecting them. If you could use an optical connection between them this would break that connection. The other possible ground connection is the grounds on the power cords of the the Sony and PC. You could use a three to 2 AC adapter to break the ground on the Sony or try a different AC outlet for the Sony.
There are audio ground breakers that could go in between the PC and Sony.
http/web.mit.edu/~jhawk/tmp/p/EST016_Ground_Loops_handout.pdf
https/www.amazon.com/PAC-SNI-1-3-5-3-5-mm-Isolator/dp/B001EAQTRI?ie=UTF8&ref_=pd_bxgy_e_img_y

Thank you for the quick answer.

Well there's something I just remembered which I left out in my original post. My Sony system uses a Europlug which is without any ground connection to begin with, only the PC uses a Schuko with ground. So there shouldn't be the possibility of a ground loop, should there?
I can't think of a software issue either because the problem is there when the PC is off. Maybe I still try a ground breaker if I get hold of one.