I noticed the same issue with my jb3 taping from the sbd. The meters seemed within the boundary but there was some distortion in vocals...damn meters. It can be hard to tell if your pushing them on the njb3.
Elana, how about locations between the md recordings and your njb3 recordings?
I've brickwalled before with my at853's, but once i switched to phantom power i've never had any issues. Mics running hot (like my soundprofessional at's vs my audix mics) and that sort of thing may add to it too...
My mv-100's auto gain of 20db with my at's works just fine, but with my audix it goes to shit. I brickwalled at a faint show and after that at a club show where they distorted once again with the mv-100! I gave up and picked up a MP-2, but i haven't had the opportunity to really pair it up with the audix mics.
My vote goes to upgrading those mics to phantom power.