Why is my Behringer XENYX 1222USB mixer hissing?

I use the Behringer Xenyx QX1222USB mixer with my Audio-Technica AT 2035, which is connected to a single socket on my PC.

Unfortunately, it is inexplicable to me why the mixer (rarely at first, but more and more often) emits such noise.

When the noise occurs, I don't hear it myself, only people about Discord, Teamspeak, Twitch.

I had the problem with a Behringer mixer before, but I had the problem there when I switched it on and it was immediately audible to myself. I then sent the mixer to the repair shop and even the manufacturer could not fix it there.

At least that's what the report said.

Then I bought the mixer that also generates the noise as described above.

I had called Musicstore once and described the problem. The technician on the phone then thought that the problem wasn't with the mixer and he'd never heard anything like it.

According to him, it should be on my PC.

I can hardly imagine that my PC should be the problem.

Actually, I think it's a defect again.

I hope someone here can help me. I would be very grateful.

But it could be the PC.

Especially when the mixer is operated from the same socket and is also very close to a PC.

A PC is a radio frequency device. Consider, such a CPU clocks with 2 or more GHz.

Such high frequencies like to scatter somewhere (eg mixer). It could also be that the phase position is not the same. That means you should put the plug in the mixer the other way around. All of these components could also be together.

So measures

1) Unplug the mixer

2) Use a different socket for the mixer, preferably in an adjoining room. (but do not use a long extension).

and you would have also fulfilled the 3rd point. Increase the distance between the PC and the mixer.

These measures are only used to find out the reason for the noise. If the noise is gone, you can try to "build back".

Is the mic on the mixer set too sensitive?

Pull ALL controls to zero. Master too. Then set the master to 50%. Test controller for controller. Always pull the tested one. NEVER turn the gain too far. The Midas amplifiers take that very badly. In principle, only pull up the controls you use