Adding passive tone control

[Hector]

Hi all. I'm on a kick to improve the sound/feel of my basses on my own, and get a little know-how in bass setup and maintenance on the way. The set up side has gone well, but I'm now looking at the electronics.

I play a Fender Reggie Hamilton Standard (not the custom shop model), It's dead useful, lots of options from the passive/active switch, and serves very well as my workhorse bass. Strung up with TI jazz flats and it sounds great. Recently though, I've been frustrated at the lack of passive tone control - I really want to use this bass to provide a classic passive P sound with both the tone open and closed. I have other basses that cover more modern sounds, I'm after a classic vibe here (getting a lot of gigs that require that sort of sound at the moment).

The controls as it stands are:

Volume/Blend in passive mode
Volume/Blend/Bass(Treble stacked)/Mid in active mode

I was wondering if anyone could advise about how I could mod these electronics to include a passive tone knob? The custom shop version of this bass has the same controls, with the slight change that the Mid knob is stacked with a passive tone control - maybe I could mod my Mid knob in the same manner?

My basic requirements are:

active/passive capability
pickup blend in both modes (which rules out a J-Retro as a drop-in alternative to the current stock pre - no passive blend)
master tone control - want to be able to pan over the P pickup alone and use the tone knob like a 'proper' P bass.


Any advice really appreciated - I have a bit of patience, willingness to improve current state of near-total ignorance, and a solder gun

[MoonBassAlpha]

U-retro has blend in passive mode

[iiipopes]

To those who would say why not just roll off the the active treble, the Precision passive circuit doesn't just cut the treble. It also changes the resonant frequency peak in rather a sweep mode, that really cannot be emulated by an active circuit.

Question: is the Precision pickup in the bass a standard Precision pickup that could be used in any other P-bass on its own passive circuit? If so, you may be able to wire a a standard tone control pot and cap off the side of the hot lead of the pickup going into the preamp so that it does its thing before the signal is processed, possibly emulating the passive Precision tone characteristic without having to go to a full active/passive switch.

I say that, because I have an Ibby SRA305. It has EMG Hz passives in a standard configuration before going to an EMG EXB, (which Ibby calls a "Phat II") and I can do the tone rolloff on my tone knob upstream of the EXB to get that characteristic tone without it being affected by the active control downstream between the pickup wiring and output jack.