Hello,
New to vMix but not production software in general. My client has a house audio system. The goal is/was to bring in a remote guest and have them questioned by a host while broadcasting the video through a house projector and the audio back through there system. I took their "audio out" to my ProFX6 USB mixer. Added that as a source in vMix. Added my vMix Call, but needed a way to get the audio from the vMix call back out through the same system I was getting their audio in. I tried taking the "Headphone Out" audio and running that back through their system but the vMix call was getting a bad echo then. It seems like I am missing some sort of mix minus. Any help or advice would be appreciated. Thanks!

make sure the output from the house audio being sent to vMix doesnt include the callers audio also.. if there is an AUX send on the house audio system you could connect that output to your ProFX6 and then only assign the interviewers mic to that AUX.. so the main outputs has both the interviewer and caller but the AUX only has the interviewer (which is being sent to vMix). this way the callers audio isnt being routed back to them from the house system..