Question Humming/buzzing noise from onboard audio when nothing is played

[klenk]

I recently built a new PC and there's a humming/buzzing noise from the speakers connected to the onboard audio jack. It sounds like when you're touching the 3.5mm audio jack from the speakers, but much, much quieter. The noise is quite faint but loud enough to annoy me. It doesn't change if I increase the volume via software, but it does gets louder if I increase the volume with the volume knob on the speakers. (So not OS related?)

The noise stops when I'm playing audio. When I stop playing audio, everything is ok for a few seconds and then the noise is back. (My uneducated guess would be that the audio chip is going to sleep, leaving the speakers with no signal, so the pick up faint garbage from somewhere. Does that make sense?)

I'm using a 3.5mm audio jack splitter to send audio to my PC speakers and my stereo. If I remove the splitter and only plug in the speakers or stereo, the noise goes away. So obviously the splitter is the cause, right? Well, no, because this same setup (same splitter, same speakers, same stereo) has been working flawlessly for many years with my previous PC.

I'm wondering if this is related to the motherboard not being grounded? The motherboard doesn't seem to have a GND pin, or at least it's not labeled. On top of that, the case doesn't seem to have a ground connection either. Is this normal for modern PCs?

Here's the pin layout for the front connectors from the motherboard manual:

I don't think this is OS related, but I'm running Linux, so there are no drivers I could reinstall.

I've updated to the latest (non-beta) UEFI with no success.

Any help would be much appreciated.

---

CPU: AMD 5600G
CPU cooler: Alpenföhn Ben Nevis Advanced
Motherboard: ASRock A520M Pro4
Ram: Corsair DIMM 16 GB DDR43200 (2x 8 GB) Dual-Kit
SSD/HDD: Crucial P3 SSD 500 GB, M.2 NVMe
GPU: None
PSU: be quiet! Pure Power 12M 550W
Chassis: Fractal Design Define 7
OS: Debian testing
Monitor: Iiyama ProLite XB3270QS-B5

 

[Ralston18]

Key words "has been working flawlessly for many years..."

If possible swap in another known working (no humming/buzzing) splitter.

Just as a matter of elimination.

Those splitters are made as cheaply as possible and they can fail.

 

[klenk]

Some of those splitters cost pennies and others cost 10 bucks. I think this one did cost 14 bucks when I bought it years ago.

I just tried one of the cheap ones I still have kicking around and now I remember why I spent so much on such a simple part: There is no real connection. With everything plugged in, you have to twist it and poke it until the very loud buzzing and crackling becomes bearable, and then you can never move or breathe again or it will start again.

I don't have another expensive splitter and I don't think the one I have is broken. It would be an extremely weird coincidence that it would break exactly when I buy a new PC. Also, a faulty splitter doesn't explain why the noise goes away every time there's a signal on the wire and then come back 3 seconds after the signal goes away.

 

[Ralston18]

There may be "more to the story".

TS, TRS, TRRS

Take a close look at all audio plugs and ports.

https://www.cablechick.com.au/blog/understanding-trrs-and-audio-jacks/

Also make a sketch showing the new PC and all connected devices, cables, power sources, etc.

Look for any "loops".

FYI also:

Ground loop

You can easily find other similar links.

 

[klenk]

The splitter and all connectors that go in are TRS, I think. They all have 3 contacts.

That Groud loop link confirms my suspicion that it's a grounding issue. Since my case doesn't provide a GND cable, I'm wondering if I could just make one? The ground pin on the motherboard should be the lower rightmost pin to the right of the reset pins, right? Can I just connect that to anywhere on the case? Is it possible I could damage something if I try this?

 

[Ralston18]

I would be very leery of "just make one". Yes you could damage something(S).

The case should be grounded via the PSU.

FYI (just for general reference purposes....)

https://superuser.com/questions/183...rough-the-motherboard-standoffs-in-a-wooden-p

You can easily find other similar links regarding grounding, etc...

Do you have a multi-meter and know how to use it? Or know someone who does?

Did you use only the cables that came with the PSU?

https://www.lifewire.com/atx-24-pin-12v-power-supply-pinout-2624578

https://www.lifewire.com/how-to-manually-test-a-power-supply-with-a-multimeter-2626158

Two initial suggestions:

1) Refer to the motheboard manual that you linked and Section 2.6 to double check all connectors and cables. Ensure that they are correctly installed and fully and firmly in place. Inspect for signs of damage.

Read the entire manual again and pay close attention to all fine print, warnings, or other provided reference sources.

You should also refer to the case documentation.

From the motherboard manual:

"The front panel design may differ by chassis. A front panel module mainly consists of power
button, reset button, power LED, hard drive activity LED, speaker and etc. When connect-
ing your chassis front panel module to this header, make sure the wire assignments and the
pin assignments are matched correctly."

2) Manually test the PSU. Ensure that all voltages are correct and within the provided tolerances.

The objective being to find/identify the problem. There should be no need to create a ground of your making.

Premise being some error of omission or commission with respect to the new build.

 

[klenk]

OK, so the motherboard should also be gorunded to the case via the PSU connection, right? I remember GND connectors on my last build that came together with the front panel connectors. It was a single pin somewhere around the power, reset, etc pins. But that was many years ago. Maybe I misremember.

I might be able to get hold of a multimeter, and with that tutorial you linked, I should be able to test things. This is probably going to take some time, though.

I'll also check all connections again. I was really thorough and triple-checked everything multiple times already, but one more time can't hurt. One thing I was not sure about is the polarity of the connections. There are no + or - signs in the manual, on the board or the plugs on the cables. The internet says polarity for power, reset and power LED doesn't matter. Is that correct?

Thank you very much for your help. I really appreciate it.