Just do not buy a Jayco Precept. I got mine brand new 29 UR 3 weeks ago and it is the worst thing that ever happened to me. Besides all the issues below it drives like crap.
Campingworld and Jayco are not really willing to fix any of the 18 points list that i gave them.
Leaking slide,molded matress, molded wood and carpets, hide a way cabinet that came out in right turns hidding my daughters leg, missing shade in rear, radio not working, overhead bunk bed loose, driver seat armrest broken, and and and, does not stop. Outside mirror folding in at 55mph, cameras not working .Not eaven the main lock is working. No one is able to get a new lock. It's on backorder like almost everything, they say. Since 3 weeks. And i wanted to go on a 2 months trip last week. Now staying at home and repairing everything by mayself. Jayco sucks. Campingworld sucks.
And lf course the "Hum" that you mentioned is not nice, as bad as whole electrical cabinett looks like. Full of garbage, parts, screws even tools.