by Gary Burchett
The last thing I need is another Fuzz Face.
But, there is voodoo in the combination of 2 pots, 4 resistors, three caps and two transistors.
There are many who have rightfully touted the positive aspects of the Fuzz Face's sound and "feel." Like anything else, there is room for improvement. There are a few negative points that I want to address for my personal Fuzz Face pedal.
- I hate RF interference. It gives me flashbacks of the Air Force Base scene from "This Is Spinal Tap." I want to eliminate or decrease the opportunity for RF to creep into the circuit. A simple 1k resistor on the input of the circuit does this well without much impact on the sound.
- I can't use a stock Fuzz Face in a band setting. The stock setup has too much bass, which overpowers the bass player, singer, drums, and most of the audience. I want to keep the rubbery stock feel of the circuit, but narrow the sound down somewhat so it will fit in the mix of my band. A smaller input cap of 220n does this well. This eliminates some of the excessive bass which apparently only elephants can hear. A smaller output cap of 3n3 was used on the original Vox Tone Bender. I used a 2n7 because it was available. This greatly tightens the low end and fits well with a band. The looser Fuzz Face sound is also nice, so I used a DPDT switch to toggle between the two output caps.
- I want to use positive polarity supply and stable transistors. This means NPN and probably silicon construction. I opted for 2N3053 transistors, inspired by Jack Orman's YAFF article. They are low gain, silicon and look cool in their TO-39 metal cases. The unknowing may mistake them for Germanium and think I am hip and trendy. I chose to bias the transistors by adjusting the value of the resistance on the emitter of the second transistor. This was inspired by Gus Smalley. It turns out, biasing on the emitter side has an interesting effect on the sound. I'll leave it to you to find out for yourself. I feel it makes the circuit feel a little more lively and seems to have spectacular note bloom and decay properties. I used a fixed resistor in place of the Fuzz pot, since I always dime it. I like to vary the sound with my guitar's volume pot. I also lowered the feedback resistor from 100k to 47k. This is another Gus trick, which reclaims some clarity and note detail without losing the characteristic sound of the circuit.
- My wife complains the sound of a Fuzz Face is like "nails on a chalkboard" compared to other circuits I regularly use. (Thanks, Trish.) I have to admit, sometimes the high end of a Fuzz Face type can be a little jagged. If you look at the circuit, it's no wonder why! There is nothing contouring the high frequencies, at least within the human range of hearing. I stuck a 47pF cap in parallel with the supply resistor to the first transistor and added a 120pF cap from the second transistor's collector to base. These eliminate the super-high frequencies without killing the sound. The 47p really hasn't much effect to the tone, but reduces a good bit of hissing. The 120p may need adjusted to your taste. This shapes the highs a bit and removes some of the harsher sounds. Making it a little smaller will add some highs back in, making it larger will round of the sound more.
- Stock Fuzz Faces don't tend to have a lot of output power. I upped the stock 330/470 Ohm resistor to 1k5 prior to setting bias. This sends a little more output to the volume pot.
This circuit works well for me. I have better flexibility over the sound and it meets all of my goals listed above. I encourage you to experiment with the Fuzz Face and try tweaking some of the parts you never tried before.
Now, if I could just make a box that auto-corrects bad notes in realtime...
Thanks to Jack Orman, Gus Smalley, RG Keen, B Tremblay, my bandmates, and my wife and daughter for the ideas, suggestions, complaints, etc. Also big thanks to the forum members for freely sharing ideas. Rock on, brothers and sisters.
Listen to it!
Pablo De Luca (aka Gringo) contributed a PCB layout for the Tantalus Project (PDF, 154k)