Got a request for the BB Preamp, but not the current version. The earlier version uses a dual-gang pot for the Level control and apparently more bass response. Like many of Xotic's offerings the BB owes a lot to the classic Tube Screamer. Schematic can be found here.
This is a library of perfboard and single-sided PCB effect layouts for guitar and bass. I'm not an electrical engineer by any stretch of the imagination, just a DIY'er who likes drawing layouts. It is meant for the hobbyist (so commercial use of any of these layout is not allowed without permission) and as a way to give back to the online DIY community.