I'm running ubuntu studio 20.04, and I'm trying to use a 4 channel USB mixer as input and use the headphone jack on the laptop to monitor output (post processing from a few or applications like guitarix). I've also installed the kxstudio suite with jackd2, Carla, etc.
The problem is, no matter how I route the connections, I have one of three results;
No sound from headphones on laptop but obviously sound on headphone jack at the mixer, unprocessed
Sound comes from mix of unprocessed and post using headphone jack on mixer but post has horrible feedback, at which when turned down has bad artifacts (robotic crackle), no output from laptop headphones
Processed around from laptop Jack, but with feedback and artifacts
Is there a way to clean up that signal so it's not feeding back? I've tried different combinations of connections, to no avail. Ideas?
Ideally, I want to be able to plug a first into the mixer, send it thru a daw like reaper,process the sound and have the results come out of the laptop Jack.