I have a passive MIM 40string jazz bass and I want to upgrade these pickups. At the moment the passive barts seem like the best choice but I would love to get active pickups. Due to my limited knowlegdge of bass electronics, I'm not sure how to go about doing this. I understand they use a 9V battery but where would that go in the bass? WOuld a tech install a battery comparment in the back, or would it be underneath the pickgaurd. Do I need a preamp, more knobs? So if someone could give me a complete list of things i need to purchase or what i need to do to go about upgrading this bass that would rock. Also, what are some good active pickups that fit in the standard jazz bass configuration.