I seem to be having this little issue with one of my basses just now! The bass is a Spector REX2000/5 with 18v upgrade. The issue is that the E and B strings are fine and boomy, but there is a significant drop in volume when I play the A,D or G strings. I changed the batteries in the bass, and this has helped a bit. I still have to:- - check my 18v mod and make sure that it is sound - check the distance between pickup and strings - although this has never been altered since the factory and has been fine up until now. I recently had the bass setup by a tech that has done this job on the same bass before. It has a new set of strings on it - could it be the strings?? I've never had issues with Rotosound before (swing 66s 45-130). Maybe now is my first time. Anything else that anyone can suggest other than check your soldering, and maybe change strings??? By the way, it has EMG Hz pickups and an EMG BTS pre-amp. I was using it with a planet waves cable, and it's going into an Ashdown EB130 combo. ALso in the signal path were Boss TU-2 tuner, Boss BF-3 Flanger, Boss CEB-3 chorus and a Sansamp BDDI. OH, the output cable back into the amp was a Klotz cable and I do have a few patch cables. I took the Sansamp out of the loop - didn't affect anything. Any suggestions welcomed!