Really useful mods for the all-time classic, the Tone Bender MKII Professional. Mods add more volume and a trimmer for accurate biasing the germs among other things…
From Fuzzcentral:
Here is my modified version of the ToneBender MKII Professional, the MindBender.
I decided to use NPN Germanium transistors for mine so that I’ll be able to use a negative ground arrangement, which allows
use of modern power supplies. You can use 2N388A, SK3861, AC127, and a few other part numbers. I made a few more changes
to the circuit to enhance it’s overall performance:
- First off, I added a 1M pulldown resistor to the input of the
circuit, which will prevent “pops” when using true bypass switching. - The second change that I made was to replace the 100K resistor on the collector of Q2 with a 47K resistor. This helps
tighten up the sound a bit, making it less “farty”, and it helps to increase sustain. - Third, I changed the 470-ohm resistor that’s in series with the
output capacitor with a 1K2 resistor. This helps to boost the output
of the pedal so that I don’t have to crank up the volume control so
much. - Fourth, I changed the 1KB “attack” pot to 2KB. This change
doesn’t really have any effect on the tone of the pedal, but it does
help
to prevent Q3 from becoming saturated. - The Fifth change was to replace the 8K2 resistor on the emitter of
Q3 with a 20K trimpot so that the collector voltage of Q3 can be
adjusted to exactly 4.5V-5V. - The sixth and final change that I made to the circuit is the
addition of a 1N4001 reverse polarity protection diode. This isn’t
necessary
but it helps to protect the circuit components in case the power
supply is accidentally reversed or if the battery is
touched to the battery snap backwards.
Here’s the Mojoed layout. 21 colums, so you’ll fit this nicely in B-box and you still have big axial caps on board.
