A friend of mine just got some 5 string Bartolini pickups (not sure exactly which ones), with an NTMB 918F, which has a stacked volume, stacked bass and trebble, and a stacked mid I believe. Here is the problem. It has EXTREMELY low output. I mean, crank my 400w amp and barely getting anything low. If I plug a set of headphones directly into the bass, I can hear it, and turning all of the knobs makes a difference in the tone. It isn't the amp because my bass works fine through it. Anyone have any ideas for this low output? We tried re soldering, making sure there were no shorts (as best we could), and did everything we could, turned the boost up on the pre-amp. Any help is greatly appreciated.