Had several requests for on-board bass preamps and what better place to start than the original StingRay circuit? Simple 2 band-EQ with low current draw and should be small enough to tuck into the control cavity of whatever bass you're wanting to add it to. Other single opamps can be used, but the current draw may increase, draining your 9v battery quicker. For example a TL071 draws 10x the current of the LM4250. A good replacement would be the LT1351.