+1WRT the K-series electronics package, here's what I have to offer.
The preamp in these basses is really just there to help against signal loss with long cable runs, with the added ability of a treble boost setting.
The bass and treble controls are both passive cut only controls. So both full on is "flat"
Some approach this by turning the B/T controls all the way down, and then gradually adding them in. Some do the opposite.
Another approach, is to dial it back on the volume control, instead of diming it like most people.
Setting both B/T at the halfway point can give you a nice midway point to work from.
I've said it before, and I'll say it again.
These basses are best approached as a passive bass.
I run L2500's passive and gradually add bass and treble to taste.
