So it should be clear from the title that I have no idea what I'm doing, but I'll try and explain as best I can. When I listen to the output of my mixer, it sounds perfect, crystal clear. But when I plug the output of the mixer into my desktop's audio input line, there is a slight echo/reverb that comes up in audacity. I'm not sure if the problem is with Audacity or Windows, but it defidently is something on my PC's side. I've already deselected "Listen to this device" in the Recording menu in the Sound settings. Are there any other settings or things I should be looking at? Thanks.
So, I figured it out, pretty dumb mistake but it might help people down the line. The issue wasn't the recording, but the playback. I for some reason had a setting enabled in my Realtek Audio manager that had all of the output audio set to "Sewer Pipe", thus causing the echo. When I disabled that, it sounds fine. Cheers.