Is there such a thing as a passive(no batteries or wall wart, please)preamp or at the very least an impedance matching device? I have a radio shack piezo-equipped DB that sounds decent- thanks to Jeff Sahs of Sacramento- but I would like not to need to worry about a battery crapping out mid-song. I'm aware some amps sound good w/a preamp before the bass, but that's not in the budget, so I'm trying to make it sound good through a Hartke Kickback 12. Any suggestions would be highly appreciated. Thanks.