Originally Posted by the wako kid
the idea is that you can change from a passive bass to an active bass without having the settings tweaked way high(for passive) and blowing up your amp.
This isn't totally correct, and adds to the confusion per the OP"s post.
WAY back in the day, the early active circuits, for the most part, had a hire output than the older passive models (i.e., the Fender type basses at the time with no preamps). So, they uses 'active' and 'passive' as shorthand for 'high output and low output basses.
This is in NO way the case these days. Many active preamps have internal volume controls, and many more are voiced so their output is about the same with the ciruit in (active) and bypassed (passive). Unfortunately, the 'acrive/passive' labels have carried through on some amps (although many now use a -15db pad indication).
To the OP, there is rarely a need to use the 'active' input regardless of what type of instrument you have. The only time that the active input or pad switch is usefull is if you have massively aggressive technique, or a very hot bass (active or passive) that results in a distorted sound at the input stage of the amp, even when you turn the gain down.
So, to the post above, there is no systematic difference in output these days between basses with and without preamps (due to the more modern preamp output levels described above, and also due to some REALLY hot pickups that put out a very strong signal). Also, you will do no harm to an amp by overdriving the input stage, and with a tube preamp, for many, that is exactly what they want to do, to get the growl and grind.