I recently had my Mustang PJ bass upgraded with the DiMarzio DP126 set and I love the difference except for one thing.. When I play the A string around the 10th fret, the volume seems to drop out. It's weird because if I slide up to the note and let it sustain, it sounds fine, but if I pluck the note from that fret, the volume is almost completely gone comparatively. I can hear a big difference in volume between that note and any other note I play at the same time while holding that note. The other notes keep their volume while that particular G sounds quiet. I read a little bit about pickups being out of phase, but I found it strange that this only happens for this particular note and maybe slightly above or below that frequency. Is this normal? How could I go about fixing it? Also, I notice that it seems more pronounced when I combine the P and J pickups. The PJ combo used to be my favorite, but now I stick to the P solo'ed because it gives me less problems and seems a lot thicker by comparison. With the original pickups, I used to love the PJ combo sound. It was thick and warm, but now it maybe sounds a bit thin if my memory serves me well. Side note: Not sure if this matters at all, but I don't have a bass amp yet. I just use a Vox Amplug and iRig 2 with my iPhone and I use iPhone wired headphones or bigger closed ear phones. Thanks in advance for any suggestions or information on this.