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Good evening fellow electro experts,

please bear with me. My knowledge about circuits is somewhat basic.

I've recently set up an audio chain from the speaker/mic combi jack of my notebook to the line-in jack of my PC. This way, I got the notebook sound on the headset connected to the PC.

The setup was working fine until I decided to plug an monitor to the notebook (in addition to the integrated one). Unfortunately, I hear an annoying electrical noise/interference whenever hold the HDMI cable of the monitor to any port of my notebook. Not just the HDMI port either, any port.

According to my research, I might have created a ground loop but I've no idea how to fix it.

The overall setup is like this:

One outlet, one outlet strip (kind of hanging from the desk atm), PC (under desk), Notebook (on desk), PC monitor (on desk), notebook monitor (wall mounted) and a simple ethernet switch (under desk) are connected to the outlet strip. In addition to that, notebook and PC are both cable connected to the switch. Notebook audio jack / PC line-in jack are connected with a male-to-male 3.5mm cable.

Unplugging the notebook from the outlet strip and from the switch didn't make any difference.

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closed as unclear what you're asking by uint128_t, Voltage Spike, Lior Bilia, DoxyLover, Dmitry Grigoryev May 2 '18 at 11:50

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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What you need is a ground loop isoloator. I had the same problem on my TV PC for years, and this fixed it.

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A high frequency current takes the path of least impedance, and the path of least impedance happens to be out of your audio jack. Use ferrite chokes (inductors) to block these high frequency signals. It's really impossible from your account to know what the source is, but you could try experimenting by using cables with built-in chokes such as the one shown below.

enter image description here

Or you could use one of these on your audio cable.

enter image description here

If the source is inside of your laptop (which is entirely possible, it happens in mine) then nothing will help.

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