Some time ago, I bought an Epiphone Thunderbird Pro bass. I love the look of this bass, kind of a mix of the Gibson Thunderbird and the Aria Pro II basses from the 80s.

There were a few things I didn't like about it though - first of all, the pickguard was a bit ugly, so I replaced it with one lasercut from leopardwood.

Even after changing the pickguard, I wasn't crazy about the sound. It's an active bass, meaning that it has a battery and a pre-amp on-board to shape the sound. Sensing a fun project, I designed a small, cheap pre-amp to replace the existing one. Like all of my electronic designs, the pre-amp is open-source with a permissive license. You can see more details on github.

The design is heavily based on the first version of the pre-amp included in the Music Man Stingray, a design overseen by Leo Fender. The first version of the StingRay pre-amp has only two controls, Bass and Treble (really, what else do you need?).

My version is quite close to that original Music Man design in frequency response, but uses modern components for lower power consumption. In tests, my pre-amp uses about 1.5 milliamps, giving approximately 400 hours of play time with a normal nine volt battery.

If you're interested in seeing lots of graphs of the response, all settings of interest are on the project's github page, including simulations and real-world tests. My favorite setting is both bass and treble boosted, giving a "scooped" frequency response:

The build process was identical to my last few electronics projects, with boards printed by the still-awesome OSH Park, and then built by me using laser-cut stencils and a toaster oven. Here's a few pictures of the completed board in the bass:

Installing the pre-amp was fairly easy, but I did have to wrap the entire board in electrical tape to prevent it from rubbing against the conductive walls of the electronics chamber and causing noise.