So here's my problem... I have a Fender Jazz with Dimarzio Model J pickups, 500K pots. It's strung with D'Addario 45-100 Chromes. What I'm hearing is a gritty slightly distorted edge to the notes, and it's most apparent on low F on the E string and C on the A string. I had my tech go through the wiring on the bass and he says it's textbook perfect...no bad solder joints, no scratchy pots, etc. He did say the Model J's are quite hot and he lowered them down as far as they would go. That reduced the "grind" I'm hearing, but didn't eliminate it. I love the tone of the bass and when the music is loud I can't hear this problem, but when it's quiet I can and it drives me nuts. I can give amp info, but I've now tried this bass with 4 or 5 different rigs and the sound is essentially the same so I don't think it's an amp thing. Could different strings solve this?