If it were me, I'd just plug into the Aux In 1/4 inch input on the back of the unit (upper left area). I've read that this bypasses some other controls, notably the mute, but presumably your mixer has a mute button as well.
Here's a link to the SA330x manual
https://www.fishman.com/wp-content/u...User-Guide.pdf
Here's a link to a chat about this very subject--hopefully I'm linking to the second page where they bring up the SA330X as opposed to its predecessor.
https://www.acousticguitarforum.com/...=212336&page=2
Good luck!