A passive preamp is basically only a switch for source, with an attenuator*. (a volume control*)
An active preamplifier has the above plus a amplification stage.
A few passive preamps have a hard time properly driving some amplifiers,,, seems the sound becomes "thin". This is due to a poor impedence match.
Active preamps almost never have this problem. An active preamp can, however, sound grainier if not well made.
My Acdom 700 has a switch to allow either type of use. I prefer the passive usually, but a few recordings sound better, (ie: fuller bodied) in active mode.
(My amp is a Forte' 4a)