'I think it's the preamp. I would love to have jazz bass pickups in my Sterling too because I think the high end is just really hard to tame. I even thought about putting a P bass pickup in front of the MM pickup just for fun, but I know that would kill any resale value.
I have not come across anyone that has put different style PUPs in a Sterling, but I would love to hear the results on something like that! My Sterling had excellent wood, high quality bridge, tuners, and the neck finish was satin-smooth! Awesome feeling bass at least!
I started laughing when I went back and read the plagent dude's advice to "Just turn the treble down, select the middle coil position and turn the bass up"
Wow! Why didn't I think of that!
But seriously, I tried every which way but loose to make this thing sound the way I wanted...and the closest I was able to get was when I put flats on it....
here is a video with my Sterling taken about 10 years ago: (This is with flats, and though the quality of the vid sucks and we were just fooling around, you can still probably hear how bright that sucker was!)

