Well, like an idiot, I plugged a new battery into my 55-01 backwards, and smoked the preamp. I brought it to my local bass tech, who could not find the MK-1 preamp as a standard Bartolini part, so he called Lakland. Turns out I am not the only person who has burned up his preamp in this manner (didn't think I was...), and Lakland is sending him a new preamp circuit for free. Hopefully nothing else was damaged, we'll see when the part comes in. I just wanted to share this story. - E.