rodecaster pro ii

I'm trying to set up OBS to where my mic audio and my desktop audio are separate and I'm having issues where the desktop audio is coming up on my mic channel please help me out with this cuz I'm at a loss and I've been trying to figure this out on my own and searching other forms and whatnot and...

Nobody on youtube has a setup for this using Elgato 4K60 Mk2 Capture Card and then OBS to Stream on Twitch. I'm having problems from mic hiss, then no mic hiss but double sounds, just one problem solved only for another to appear... I'm hoping someone out there has theirs set up and can post...