I looked this up just to see what it was... Just so we're all on the same page, do the images below detail what you're asking about?
Two Standard Tone Pots
Single Dual-Concentric Tone Pot
This one is for ChrisK...
I'm not the wiring guru around here, but I'm certain others will chime in soon.
I'd be interested to know about the feasibility of this one as well.
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I ran a simulation to confirm my suspicions on this. With the values specified, there's a pretty sever scoop in the area around 1KHz. It also reduces the resonant peak that normally shows up around 4K pretty drastically. I'd expect this would not be acceptable. We might be able to futz with the cap values to get it to behave better, but...
...the reason you see these in amplifiers is that there's a general volume loss that looks to be greater than 6db. Doesn't sound like much, but it means you'll get about half the volume out of your axe, even with both controls at max.
This circuit is cut-only (i.e. loss-only). It gives the impression of boost as well as cut when used with active gain stages since the gain "forgives" a lot of cut.
Keep in mind that the Fender tone stack (called such since the sections are "stacked" upon each other and hence interacting and overriding - the middle tone section especially) is in actuality a subset of this structure and fairly wanting (i.e. crappy) in real effect. It was used since vacuum tubes were to expensive to use as active gain/tone stages (and few had thought big thoughts at the time).
While the Baxandall structure is indeed clever, it is not preferred over active tone control stages such as I showed here, which wrap active gain in the form of negative feedback around the tone shaping ( newey) components. The advantage of this is that little or no noise is amplified by the active circuitry, which certainly IS an artifact of the Baxandall structure.
As I had posted in the "Brian May Trilogy" some time back, "I did develop a much easier way of doing this a few years back (2002). A$$uming that the phase switches are separate from the combo switches, it takes three SPDT center off switches, a GAL (a ultra-low standby current/input threshold activated CMOS Generic Array Logic IC), 8 SPST analog switches, a few resistors, an optional OPAMP buffer, a voltage regulator, and oh yeah, a 9 volt battery. I'd also included active tone controls.
Note that I'd also included CMOS switching of phase and humbucker splitting. BTW, it's only easier since you use a PCB to do the wiring, program the GAL to do the switching logic, and use active stuff to save a whole bunch of money. This can be done for about $20 to $30 in volume."