Baxendale EQ

Hello everyone,
wasn't really sure where to put this as there wasn't an outboardy kinda bit, but basically i'm building an EQ for a JFET pre-amp (based loosely on the Albert Kreuzer one). The whole things going to be for bass guitar, at the moment i'm using the circuit i've attached, but instead of TL082, a TL072 and instead of the 500k pot i'm using a 100k pot.

my problem is the centre frequency of the treble is too low and attenuates far too much also i would like to move the centre frequency of the bass up and increase the gain on it slightly.

the gain factors aren't really an important issue but the bandwidth and Fc are. Can anyone tell my how to figure out what values i need to change to alter the Fc's. i know i want to use 1/2pi*f*C, just not sure where the R is for the treble.

any help would be greatly appreciated!
thanks in advance

ps- hello diyaudio forums :D
 

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