New development... today, while playing my new baby and I noticed something undesirable. There was something just not 100% right with the tone. Having owned several and played tons of bisonic equipped equipped basses, I know the harmonic richness of these pickups... for some reason though, with the tone all the way "open" on 10, there was still a kind of muddiness (especially apparent when fretting anything past 7th fret on the low E) and what my ears perceived to be a overall dip in the upper mids. First I tried swapping out the E string for a different one, thinking that maybe it was a flaw like a crimp of the inner core wire or a break in the winding somewhere (which I've had once or twice with certain flatwound strings in the past). Problem persisted though with a different E string. So then I thought, worst case scenario, some part of the pickup is starting to go or there is some kind of dead resonance/frequency issue inherent to some piece of wood in the construction of the neck or center-block. But perhaps it was just a faulty connection or component in the wiring? So I pulled out the guts and took a closer look... Boom! Culprit identified. Opposite outside lugs of the tone pot each had capacitors connected to the ground! Where you would expect the normal tone cap to be, there were two .022 mfd caps; no problem there since that adds up to a pretty standard tone capacitor value. On the other side however, there was a single .022 cap running to the tone-suck switch, but in such a way that it was leeching those very missing mid frequencies even when the tone-suck switch was in the off position!!! I simply disconnected that capacitor and the entire tone-suck circuit, leaving only the bisonic, volume, tone, and output jack... revealing that magical, signature bisonic harmonic richness that I have come to covet and love. Long story short, if you have a bass with the dreadful tone-suck circuit, disconnect that thing-a-ma-bob! It's evil and stands between you and the full force and ultimate gooey goodness of the bisonic pickup!
I wonder if this was part of the reason why I always preferred the tone my 1966 SFB-I with the middle/bridge position bisonic and no tone-suck, to all of the neck position SFB-I's I had played (because I don't think I have ever played a neck-pickup SFB-I without the tone-suck switch... until now!