Here is a quick mod for my Mini-Booster pedal, to add a switch for fattening the sound.
Basically, the circuit uses LEDs to drop the voltage from the power supply going to the Mini-Booster. Instead of 9v powering the booster, the pair of LEDs will drop the power to about 5.4v (if using typical red LEDs).
Less voltage = less headroom, and the circuit will clip with smaller signals. The boost is still basically clean but the lower headroom adds a bit of grit to the sound for mo’ phat boostin’.
No other changes are required to make this work with the circuit. Current draw is low and well within the limitations on the LEDs. The switch can be any common SPDT with a center-off position.
I actually prefer to use blue or white LEDs with this circuit because of their slightly higher forward voltage, which gives the switch settings a bit more impact.
The switch position as shown in the drawing is equivalent to the original unmodified Mini-Booster; both LEDs are being bypassed. The center-off position is the fatter sound with both LEDs dropping the power supply voltage. When the switch is to the bottom, you get a slightly subdued version since one of the LEDs is bypassed and only one is dropping the power supply.
This same circuit will work with the AMZ Mosfet Booster also. Enjoy!