To go along with a 6 string build I am [slowly] working on, I have also been thinking about a new on-board preamp design. Unlike conventional preamps, this one focuses on preserving the natural tone of the pickups while using multiple pickup wiring combinations to provide tonal variety rather than tone controls. It is entirely digitally controlled, and thus programmable, but uses an entirely analog signal path. The idea came from the problems I have with most existing basses, both active and passive: Limited to 2 or 3 pickups Too many controls and switches with too few good combinations Inconsistent pot tapers Level variations across different pickup combinations Tone variation and high frequency loss due to coil loading, especially for increasing numbers of pickups Poor S/N ratio due to low signal level and unbalanced cabling Noisy electronics Scratchy pots Complex wiring Dead batteries The natural tone preamp attempts to solve those problems by implementing these features: Support for up to 4 pickups with up to 6 coils total Minimalist controls with a single master volume and single rotary preset selector Any combination of split/series/parallel humbucker coils with separate phase and pickup levels per pickup for every preset Programmable pot taper Level normalization across all presets so there is no change in volume when switching presets Dedicated buffer amp for each pickup for true no-load sound for all combinations Ultra low noise op amps Line level output for high S/N ratio Balanced output option for reduced EMI 100% digital potentiometer signal path for "scratch-less" operation Clean control wiring with 2 - single gang potentiometers and 4 total connections required Phantom power option for battery free operation Surface mount is unavoidable with this amount of silicon but the relatively low component count and nothing with a pitch less than the standard SOIC at 1.27 mm and 1208 size packages should make it manageable to solder. Unfortunately this also means I need to finish a PCB design and get it fab'd before I can see if it even works. As such this is still in pre-prototype phase but the design I have includes: 1 - ATmega328P microcontroller (BYOB for this part, ex: Arduino Pro Mini) 1 - AD5206 hex digital potentiometer 3 - MAX395 8-channel SPST analog switches 3 - OPA1692 dual op-amps 2 - single gang linear potentiometers (almost any common value will work) A handful of passive components The digital controls will use an off-the-shelf Arduino, which allows nearly complete separation of the analog and digital sections and also prevents having to solder even more tiny components. The remaining analog and power components will be on another board and the two boards linked with about half a dozen wires. I have not completely decided on the pickup switching options. One option not possible in the current implementation is reverse phase for series connected humbucker coils. The entire pickup can be reversed, and the two coils can be phase reversed when wired in parallel, just not when in series. Anyone particularly like out of phase series humbucker coils? Having never designed a preamp before it is safe to say I am in way over my head. However, I learned to use KiCad to do this project so at least I have a schematic to share: Click to zoom. Even then it is an eye chart! I am interested in feedback on the design and component selection and also if a project this crazy has appeal to anyone besides me. If there is enough interest I wouldn't mind publishing an open source design so anyone can build their own. Don't hold your breath though, as having this finished is still a long way out.