bass electronics problems: it's too QUIET!

ok here's the deal. i've got an Ibanez SR405 (5 string soundgear) with active pickups. for some reason, the bass is QUIET. comparing it to my friend's ibanez w/ active pickups, my bass plays half as loud as the other bass with the EQ and volume settings on my bass amp at the same level.
this bass has ALWAYS been quiet (or at least, it has been for a long time). i want to fix this, because i'm starting to have to max out my amp to get heard at practice and shows, and i don't want to have to do this. so if you guys have got any ideas on where to start looking for problems, give me some suggestions. i can wire stff up and solder no problem, but i'm not sure where this problem might lie before i start randomly re-soldering things in my bass.
thanks a lot.
bass: ibanez SR405
amp: eden wt400