[DIY] Jack Orman's Mini Booster, with my own mods

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
These values are taken from the very inspiring article from Runoffgroove on their Fetzer Valve. The main idea is to mimic the input stage of an amp that uses a 12AX7 tube.

  • 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!