Hi, One of my basses has a custom 18v (only) preamp that Bill Bartolini made for me in the early 90's. I'm not sure if it was ever a production unit. The other bass has an off-the-shelf Bartolini 9v/18v preamp he gave me. At lower frequencies, differences in sound between them are huge. I'd like to find something current that can equal the custom preamp. I also have a custom Jim Williams onboard preamp in an EUB that I'd love to find a replacement for - it sounds great but is a real battery eater and a liability! Here's what I need in the preamp: true +V/-V rail design no DC blocking capacitor in output path -- can pump DC directly to amp! I sent a request to the Bartolini company and am waiting for a reply but it's been at least 20 years since I looked for preamps so I would expect there to be other options out there.