I could use some help dialing in my FDeck at shows. I've played a few shows now with my FDeck and I am having feedback with only F#. It's very weird. And it happens during indoor and outdoor gigs, using an amp or going direct. My setup is a shen sb300 with a full circle going into a BBE active direct box. I've tried to set the FDeck at each end and right at noon but it still seems to howl at each setting. Any help on this would be appreciated.