Well,actually my passive pups have a preamp with them.
Pups don't need to be active to have a preamp in the bass.You can think as preamp is a little amp in the bass.Just like big amps,they have their own sound.Depending on the model,they can be 2-3 band.Bass-treb.-mid.There are different variations.
Active pups means,the pups need a battery,without the battery,no sound comes off your bass.
Just do a search,you'll find lots of info.
