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My PC has a 3.5mm analog audio output for headphones or speaker. As such, there's no noise and the sound quality is good.

After adding an audio splitter, I plug my headphone into one of the 3.5 mm jack and that works well, as before.

When I plug in a 3.5 mm connection cable, plugs at both ends, (Bose brand), and plug it into my other PC's audio input,there's "static" [sic] noise all the time. It's like there is some sort of electrical static noise. But on the 3.5mm output of the other PC, if I just wear the headphones there, it's all clear again. ONLY the input is like this.

I have an HDMI recording device that can be added to OBS to capture a console's screen for example, but also to listen to said device's audio. However, if I listen to that in OBS, there is noise. So noise is present when using the digital HDMI signal.

Where is the noise coming from?! I've tried filtering it with Speex filter in OBS for example, but it's far from a solution. It's just a dirty workaround.

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    This sounds like interference. I would buy a clip-on choke/ferrite bead to reduce the amount of interference. amazon.co.uk/ferrite-beads/s?k=ferrite+beads
    – spikey_richie
    Commented Jul 15, 2022 at 11:42
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    You need to check the pin-out of the splitter & compare it to the headphones [which probably matches] & the 'cable' [which probably doesn't]. You cannot just jam a TS or TRS jack into something that needs a TRRS. You just short it out. Even if the pinout is OK, you probably have horribly mis-matched impedances, if not also a ground-loop. Might be best to describe what you're actually trying to achieve rather than about what you think you should do to achieve it. That becomes an XY Problem
    – Tetsujin
    Commented Jul 15, 2022 at 11:46
  • @Tetsujin This is just 2 regular home PCs with modern motherboards, and sound chips. The splitter is a simple (but good brand) splitter, and the cable is a normal Bose 3.5mm jack-jack one. The Bose Jack goes into Audio In on the second PC and that's it. The distance is like 3M. So like there is nothing fancy, no pro audio tech, no converters, nothing. Just a simple audio output from PC1 -> PC2 input. And there is a static. Why.
    – Apache
    Commented Jul 15, 2022 at 12:36
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    5 lines of 'explanation' yet you have failed to investigate point one of my comment. There is no such thing as a "regular" PC or "regular" cable. There are at least 4 major standards of 3.5mm "jack", & at least 3 voltage/impedance standards, none of which are cross-compatible.
    – Tetsujin
    Commented Jul 15, 2022 at 13:37

1 Answer 1

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You're connecting two devices plugged into the AC mains with another cable, which creates a ground loop. Since you weren't specific in the description of the noise, likely that's the cause: a 50- or 60 Hz hum.

To prove that, run one of the PC's so it's not plugged into the mains, nor into an external display, nor any other device plugged into an AC socket. You can use a laptop to test, or run the PC, sans display, from a UPS for a short time. If the noise goes away, it's a ground loop issue.

There are many ways to eliminate that issue, such as using a common AC mains source, installing an isolation transformer, etc.

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    "Ground Loops" seem to have achieved almost mythical, pseudo-religious status. They are really not all that common & are rarely the cause of hum in a modern system. I've been an audio engineer for about 40 years & have still to find a real one in a working situation. [I tend to use isolating 1:1 transformers anyway for my own live situations, but even when engineering for others have not come across this in any practical situation.
    – Tetsujin
    Commented Jul 15, 2022 at 18:27
  • @Tetsujin, In my experience, even powered speakers have introduced hum, perhaps due to a low-quality wall-wart. Reversing the supply in the outlet fixed it. Could be that in your country, safety standards are more rigid, or wiring runs shorter.
    – DrMoishe Pippik
    Commented Jul 15, 2022 at 19:59
  • Wall-warts introduce 'hum', or actually switch-mode power supplies induce all kinds of stray RFI, plus the infamous 'buzzing' feeling when you touch a conductive surface. This is not 'ground loop'. It is something else entirely.
    – Tetsujin
    Commented Jul 15, 2022 at 20:01
  • @Tetsujin, you have missed the point that reversing the plug eliminated the hum. It could have been due to capacitive pickup in the PS, which was bypassed to ground by reversing the plug, but the net solution is the same.
    – DrMoishe Pippik
    Commented Jul 15, 2022 at 20:10
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    Reversing polarity on AC should make no practical difference… it's AC. A lot of EU [not UK] plugs have no inherent polarity on their plugs at all, there's no way to even tell which way up they "should" go. The only difference in result by doing this could be in how well neutral is bonded - which becomes an electrical concern outside my field of expertise.
    – Tetsujin
    Commented Jul 17, 2022 at 13:04

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