This probably seems like a stupid question, but I've never tried changing anything on a bass other than the bridge. I got a passive bass thinking I missed the passive sound but...I want another active bass So I stripped all the parts off & was wondering what do I need to put in it to make it active? Active pickups, battery cavity. Do I need an on board preamp? If so, can anybody recommend a decently priced one that is available on gear websites & that sort of thing?