Passive treble boost

[snailspacejase]

This is not a pedal question but it's in the signal chain so I don't feel too bad for asking 
So I've got a p-90 in the neck position and a humbucker at the bridge. If I eq the rig to sound good for the p-90 the bucker sounds deadly bright. Vice versa and the p-90 sounds too dark. I was wondering if there is a passive circuit I could put in the guitar that would boost the treble of the p-90 without the need for an active circuit/battery and without sacrificing the p-90's output level. I'm not keen on subtracting treble from the bucker to  drop down to the p-90's level if you know what I mean.
Any thoughts much appreciated.

[rullywowr]

The nature of a "boost" is to add energy to particular frequencies.  Since you can't get something from nothing, a boost inherently needs some sort of power source.  You could cut some of the bass frequencies at the expense of output.

An active EQ would solve most of your issues, and unfortunately would require a battery.  You could wire it into your guitar's control cavity.  You could also have a EQ pedal on your board which you would kick in.

The issue is that you are using two different types of pickups which have different frequency characteristics (which gives versatility, I know).  The easiest solution would be to get two humbuckers or two P-90s... 

[midwayfair]

Presumably this is a guitar without two tone knobs?

You can hardwire a treble bypass to the humbucker alone, or a treble cut to the P90 alone. It wouldn't be adjustable once you soldered, but you also wouldn't need another knob. Just use the wiring scheme for a typical gibson, but ignore the tone pot and use a much smaller tone cap.

[davent]

I've used this setup to roll off bass from the neck pickup in a two pickup guitar, cuts bass but doesn't boost treble, one capacitor.

[snailspacejase]

Thanks for the replies.
hmmmm I'll have to do some experimenting. 

[slimtriggers]

Maybe you could change the pot to 1meg and use a parallel resistor with the humbucker to lower it to 500k.  Assuming it's currently 500k, of course.  That way your neck p'up would "see" 1meg and your bridge would "see" 500k.  That would keep the tone of your bridge and possibly brighten up the neck position. I haven't really thought through how to wire it, though.