http://www.duncanamps.com/tsc/index.html
Found this interactive tone stack calculator today and was wondering if some of the layouts could be used as a pedal. I think these are tonestacks for an amp, but I think it would be great as an EQ pedal. Is this possible?
Passive tonestacks like these are lossy, meaning they need to have a gain recovery stage after them. Also, many of them need to see a low impedance input. So you would need a buffer before and after most of these tonestacks.
You could easily use any of them with a buffer input and recovery stage as azrael indicated.
Check out the Tonemender (http://runoffgroove.com/tonemender.html) from Runoffgroove.