I recently upgraded from Symphony 2+ to a RNS-e unit. Installation went very smooth and unit functions great however I noticed that when all power is off (key off and out) I can still turn on the unit and despite turning the unit off l, I can hear a very faint hum from all the speakers with my ear up next to them. I noticed it when washing the car and wiping out the door sills.

Is this normal? My primary concern is that I will come out to a dead battery one day. I already had to charge my battery once after about 30 min of setting up all the menus with the car off (my fault)