I'm currently building a passive pre-amp circuit for my fretless Fender Jazz. I've already upgraded the pickups to a set of Norstrand NP4 P/Js. The controls will have a master volume, pickup blend control, and tone control. The pre-amp I'm replacing had a varitone that allowed me to choose the value of the capacitor in the tone circuit. I would like to install a toggle switch to choose between the .047 mfd cap and another value cap. Any suggestions out there for what value I should choose for the second cap?