i think modding it to passive requires creating a switch to bypass the preamp and to allow for the pickup to run through the pickup switch into the volume pot or it requires you to change the preamp into a passive one. definitely dont do the latter, i think. i think the difference between passive and active basses comes down to headroom and what you're able to do with tone knobs with a compressed signal, if you like a volume knob on a passive bass up all the way, its hard to do that on an active as the output is higher and the detail is even greater in terms of what comes through with sound. Honestly id reccomend dialing back on the volume a bunch and raising the pickups slightly. that way you can get more detail in sound with lower volumes.
the sterling is going to be a ceramic pickup that has a series/parallel switch. in series that is going to sound very bright and loud. also ceramic pickups are known for being brighter, it may actually also just be how the pickup on the sterling sounds. that doesnt mean you cant get warm sounds out of it without modding it, but it means you have to sort of not take the road to those sounds that you would with for example a p bass.
