Untangling the options re: onboard active/passive blend/vol

[Eddododo]

I'm working on a preamp for a build, and I'm stuck in a bit of a logic loop, or lack thereof.

The setup is 2 pickups, with active/passive switching.. the eq details don't matter for the conundrum itself. One of the preferred goals of the preamp circuit is the improved usable sweep of a balance pot or twin volumes with buffered mixing... but there is a conflict between a few main factors:

-passive 2 pickup circuits generally require pickup-to-wiper wiring for a 'backwards' volume pot.. this works okay, and it's the typical arrangement we are all used to with jazz basses and most non-switched 2-pickup basses. (It's also what blend pots are doing, so they are interchangeable)

-this 'backwards' volume wiring is sub optimal, with heavy loading and resistive noise introduced, compared to a typical wiper-to-output volume pot.

-The advantage of the ACTIVE mixing becomes a bit truncated by having to use the 'backwards' pots.

- I don't want extra knobs that don't need to be there... IE I want volume/blend to function for active and passive

So.. this was my initial draft. It would use a 4pdt to switch active/passive, conveniently found on S1 push pull switch pots. You'll see that when switched, a tone pot will be 'added' to the top pickup.. the tone KNOB would run a dual-gang of two tone pots... one side would be the master tone in passive, and the bottom pickup tone when active. While we still have the 'jazz bass' volumes, the ability to smoothly combine a spectrum of volume combinations will be enhanced by mixing them through buffers.





Now... I could use switches to reassign the pot lugs, but the best I came up with requires a 6pdt, or maybe a 5pdt... not impossible to find as switches, but certainly not available on a push-pull.. not the worst option, I suppose





There's also this option.. the same-color pots would be modded dual-gang pots (IE a Knob that turns a 250k and 25k locked together, one set for each pickup). This leaves each pickup with a single volume knob, but the performance is enhanced when it's active. The only cost is that I need 2 dedicated knobs for vol/vol, and cannot use stacked vol/vol, nor can I use blend/vol. Not the worst trade off, perhaps. Now this may look like I still have the 'backwards pot' problem, but the Op amp buffer alleviates the loading effect better, and the series resistance noise is reduced by the lower value pot.






So with all that, there are some solutions.. but each one seems to overshoot being 'elegant' by a step or two...
The other thing that comes to mind is while its true that the 'jazz bass volume' is flawed, I also cant help but wonder if its actually a problem worth solving, considering that its such an unbelievably common wiring scheme.. yes, the noise is a bit enhanced by the slight gain of an active circuit, but I'm just not certain its an issue..

[Eddododo]

I forgot to mention that a treble bleed is an option I'm considering as a means to counteract the muted highs from the unfavorable conditions set by the 'backwards' volume

[amptramp]

It sounds like you could benefit from a panning circuit.  Take the output of each buffer through a resistor to opposite sides of the panning pot.  Ground the slider.  Use two resistors to take the ends of the panning pot to one op amp set up as an inverting amplifier.  The inverting input is a virtual ground because output feedback is set by the current input and the voltage at the inverting input doesn't move.  Use a level control at the output of the inverting stage.

[Viktor Von Doom]

-this 'backwards' volume wiring is sub optimal, with heavy loading and resistive noise introduced, compared to a typical wiper-to-output volume pot.

Can you (or somebody else) explain what you mean by this?

I have a 2 pickup bass wired 'Jazz-style' as well as one with two pickups I am currently planning on changing to a Volume, Blend, Tone style (using the ungrounded M/N pot approach that I am sure you have seen at that "place where people Talk about Bass"). Am I missing something from the bigger picture here? Isn't this a fairly standard wiring practice?