Here is the schematic of Jack Orman's acclaimed Mini Booster (www.muzique.com). This booster is extremely powerful (maybe too much) and adds a bit of nice grit to the sound. I had to modify it to get the sound, and the frequency response I was looking for. I turned it into a "treble boost" favoured by Brian May (Queen) or David Gilmour (Pink Floyd).
To do this, simply :- replace C1 with a 33k resistor
- increase the value of C5 to 220 pF
- Increase the value of R5, to lower the global gain which is very high, to 10k or even 22k
- Place a 1nF capacitor in parallel with R5
- Better still: solder sockets -which I did- in order to play with these two values to obtain the sound you like best!
These two elements will transform the booster into a treble boost. This is particularly pleasant on guitars with clean humbuckers. The notes are defined, as clear as drops of water.
With overdrive/distortion, the sound gets clearer and more defined. To reduce the attack and get a mellower sound, simply play the guitar's tone knob.
It's all good!