So I picked up this older model OBP-1 preamp thinking I had three different basses for which I was considering a preamp upgrade and surely I could fit it into one of them. I decided on dropping it into my Fernandes APB-100 fretless five, which is about the best bass that no one's ever heard of. Sounds great, but I'd been thinking I'd like a little more oomph from the low end boost. Enter Aguilar. So...copious notes were written before removal of the existing preamp since I've learned from experience that the phrase 'Oh, I'll remember where that goes' is probably the most dangerous phrase in the decidedly brief history of preamp wiring. Took out the existing pre and started putting the Aggie into place. Got it all wired up and...nothing...touching the volume knob resulted in a lovely buzz, and I could actually boost the bass and treble on that same buzz (which at least let me know I'd followed the diagram right as far as wiring the preamp), but it was still just a buzz...not particularly useful. Back down to the basement and the soldering pencil. Hours later I've resoldered wires to the jack in about ten different combinations and removed the blend pot from the circuit, wiring one of the two pickups directly to the volume pot and leaving the other one unwired completely just to simplify the circuit and make sure the jack is properly wired. Eventually I I get things to wear I can hear a very faint tone out of my bass...great...the jack is wired...time to put the blend back in and add the second pickup. Only when I wire it all together, I get nothing but more noise. So I unwire the blend pot and the pickup again and go back to the single pickup/volume pot combo and it works again....very faintly, but it works. And then it hits me. Just to check my theory I swap out the stock pickup for a seymour duncan I have lying around and out comes clear, full tone. A quick look at my original preamp notes confirms my theory: The pickups are active. The battery powers both the preamp and the pickups, so when I yanked the stock pre and wired in the aggie, power was cut to the pickups. With this stunning realization, I went to bed. It was about 4:30am and the birds were starting to chirp and that sound always reminds me of all-nighters in college were if you were still up when the birds were out it meant you a) only had a few more hours to finish that paper and b) were going to be one tired hombre for the rest of the day. So...I realized today that I might be able to wire an additional battery to power the pickups. I used to have a set of active SDs that I never installed because I was unfamiliar with how to properly wire the active pickups into my existing preamp circuit, but when I consulted the diagram on the Duncan site, I got a good idea of how I can make all this work. All this because I just *had* to put that Aggie preamp in something... So yeah, I'm tired, but, as Dexter says, it was a good day for science. Stay tuned for chapter two once I put operation add-a-battery into practice. J.