Pensa J-4 custom bass guitar electronic buzz/ground loop buzz

[jcalo]

I just purchased the Pensa J-4 custom bass guitar and I'm experiencing an irritating buzz in some of the establishments that I've played. It doesn't seem to like buildings with old wiring and/or dimmer swithes and florescent lighting. I've gone through a number of solutions that I thought would take care of the buzz such as the Furman conditioner however continue to be stumped by this ground loop buzz. Keep in mind that the bass does experince positive outcome in some rooms that I've played. Does anyone have a solution to this dilemma, I love this bass guitar.