can i connect a pre amp to a active speakers

As opposed to what...a mixer? I don't know why a pre-amp would negatively affect sound quality. You just have to look at the input sensitivity of the speakers. It's no different than using a pre-amp to drive an amp, which then powers passive speakers.

Normally, that is the way it is done.

A good preamp should have very little effect on the sound, and allow control of the system from one point.