Thanks for your detailled explanation!
[...] Headphone out from the card to channel 1 and 2 on the mixer. [...] Channel 1/2/4 are on but all others are off.
[...] When I turn on Audio Monitoring I get the feedback. It's super loud. I unplugged the Mics from the mixer and unplugged the Logitech camera, but I get the feedback anyway.
There exactly is your loop: monitoring out to channels 1+2. They are on as you say. So they get into obs back again. Then, if and when you turn on the monitoring function, the loop is closed. Totally independent from further microphones, as you said.
You have to break that loop strongly. I assume that you looped out the xoner into the mixer for having playback of videos or something? Then there are two possibilites:
- Use another way to monitor, routed straight to headphones and nothing else.
- To surrender let the loopback into mixer 1+2 away. Route pc internal playbacks only via the obs audio mixer into the sending rail.
If you have to sound reinforce the playback into the room only, fade down channels 1+2 on the mainbus and use a prefader aux way to your p.a.
You could have that inverted: All that should be able to hear in the room/p.a. goes by mainbus to your speakers. Build up a (sub-)mix on one aux-way and route this mixers output into the xoner.