Noise in headphones, what to do?

My headphones always hiss a little in the background when I play Minecraft, record with OBS with the hardware or open the browser.

I have a Sound Blaster Audigy 5 / rx as a sound card.

The strange thing is that I can only use two of the connections on the sound card

My PC is pretty new too, so 2 months old

Then your sound card is most likely broken.

Try it somewhere else. Then you know it's the card - or the listener.

Sometimes this is related to the dirt in the headphone slot.

Ok, look

Is probably due to the computer.
The KHs reflect what you send into them.

The listeners are not!

But when I plug it into the standard Realtek socket, everything works wonderfully

This is due to the different processing of the signal