General speaking the active and passive inputs on an amp are related to the level of signal they can handle. Passive output basses are not going to have a 'hot' signal, whereas an active preamp could. So, a passive amp input is geared for a lower signal and more gain, an active input will cope with a higher level signal (which might otherwise overload the passive input).
Also, there could be a difference in impedence. A passive bass generally will have an output impedence of 10k, but an active preamp might have a lower impedence (the Sadowsky is 1k whereas EMG stick to 10k even though it's active and most line drivers will be 600ohms). Worth checking the specs on your amp to see if the inputs have different impedences. So long as the output impedence of the bass is less than the input impedence on your amp you're ok, so 1k into 10k is good. The other way around is bad and will act as a filter, so output 10k impedence into input 1k is not a good idea.
Most amps and pedals will have a high impedence, say 1Mohms, to make sure everything going in will be below that.