Hi I've bought a Z5 some weeks ago and I'm wondering what preamp is in this bass. I've opened the back cover but I can't see who's the producer, it only has writen "G & B co." Does anyone know what is this? I like the sound, but I have a spare bart XTMB-918f that was the pre from my Tobias Growler which was replaced by a OBP3 and I'm thinking about install the bart into the Z5...?? Sorry for so many questions in one time. Hope to hear your opinions.