Building a Fuzz module
As with the Wah circuit, I downloaded several circuits from the Internet and after breadboarding and testing severals with the guitar I settled on building the " Big Muff " and the " Fuzz Face " which I describe in the following .
The Big Muff
Construction is straight forward except for the choice of transistors , notice the diodes polarities . The signal is first applied to throught R1 , C1, and pre-amplified by Q1 then fed to RV1 which is adjusted for the amount of sustain to the next two very high gain amplifier circuits Q2 and Q3 which combined with the diodes in the feed back circuitry distort the signal . The resulting fuzzed signal is then fed to the tone circuit control then on to the final stage of amplification Q4 , volume output is adjusted with RV3.
A simple by-pass circuit is shown but a true by-pass can be added as previously described.
You may apply the power is several ways , S1 can be a small SPST switch or a switch attached to the Volume control RV3 or as part of the input jacks switching on the NEGATIVE side of the supply line.
An LED indicator can be used connected in series with 1K to 4.7K seristor across the circuit power supply or incorporated in the by-pass as shown in Switching circuit C .
Note - The following parts are missing on the list
C10 = .1uf and C14 = 100uF/ 20v
RV1,RV2,RV3 = 100K
Again if you are going to use only the fuzz system on its own you may want to install the true by-pass circuit as described in the WAH module .
All transistors are NPN types,all the transistors suggested that I have tested for used gaves the same peformance without the need to adjust the bias resistances . The transistor cases are TO92 plastic types .
The Fuzz Face
The Fuzz Face circuit shown is a highly modified circuit of the original to provide exact tailoring to the taste of the user with the use of on board miniature potentiometers .
Adjustment of the on board potentiometers is not critical to the circuit and provides for a wide range of tonal output and once adjustments has been made it is suggested that they be sealed to maintain the desired configuation.
You will notice that PNP transistors are used , as with the original Fuzz Face germanium type transistors are used for the apparent soft fuzz these transistors produced. I still had in my junk box many old germanium type from old portable radio vintage early 1970s and I used two 2SB175 which I assume are no longer available but any similar small signal germanium will do as well as silicon PNP.
You may want to use NPN types and that is allright but ensure that supply and capacitors polarity is reversed ,actually all of the same NPN transistors used for the Big Muff can be used for the Fuzz Face , you may also have to adjust R2 ( 33K) bias for best result.
RV2 , RV3 and RV4 are PC type miniature potentiometers while RV1 and RV5 are your external controls. Choice of by-pass switching is yours as described .
For a combined Wah and Fuzz guitar effect unit , the switching layout described on the next page shows how it is done .
WAH FUZZ SWITCHING SUSTAIN ATTACK/DECAY VIBRATO/TREMOLO