Mad Bean Pedals Mangler, Quick Start Manual

5 

Overview 

2017 Changes:

 Reworked the layout for centralized I/O pads. Added pull-down resistor option back to the circuit. Small 

changes in the power section. 

Either you love fuzz, or hate fuzz. There is no in-between. Fuzz for life! That said, the Mangler is ½ classic Fuzz Face and 
2/3

rd

 other stuff. I double-checked my math on that and it’s solid. 

The 2017 edition of the

 Mangler

 includes a voltage inverter on the PCB. You can use your standard center-tip negative 9v 

power supply to power this positive ground effect without having to use a Road Rage board or other trickery. This takes 
out all the guess work for newer builders who have not dealt with positive ground effects before: everything is hooked up 
and wired like a normal negative ground effect! 

If you have never purchased PNP germanium transistors before, you can find several variations and offerings at 

http://smallbear-electronics.mybigcommerce.com/

. These transistors are tested for gain and leakage beforehand. 

Smallbear also provides resistor values to properly bias the pair of transistors you purchase. Please feel free to use those 
values instead of the ones listed in the BOM of the Mangler. The tabs on the silk screen of the Mangler

PCB indicated the 

emitter of 

Q1 

and 

Q2

. 

Calibration 

To bias the Mangler, touch the black lead from your DMM to the

 TP

 pad under the 

Bias 

trimmer on the PCB and the red 

lead to any ground point on the circuit. Adjust the trimmer until your DMM reads approximately -4.5v. It does not have to 
be EXACTLY -4.5v…but keep it pretty close. One mod: try setting the bias voltage closer to -3.5v or even -3v. This 
typically squashes the fuzz down even further for super-compressed violin-like fuzz (a la Eric Johnson). It may not work 
with every transistor pair, though.