How to build a basic Fuzz Face clone from scratch and convert it into a "boutique" version with precise biasing, transistor switching and more.
There are many pedal kits out there, but simple things can be built from scratch, such as a retro-style fuzzy box that allows you to learn more about the circuit and modify it to optimize the tone and versatility. Fuzz Face's knowledge is flooded with snake oil, some devices sound mediocre or even scary, and there are also those mythical "golden" examples that sound incredible.
Happily, the knowledgeable replica manufacturer spent decades analyzing this relatively simple circuit and clearly understood the variables that distinguish the best from the others. Many people shared their findings well, which effectively eliminated the mystery of Fuzz Face in the process.
Here, I show you how to build a basic Fuzz Face from scratch, and explore how to make the circuit sound exactly as you require. I will also use switchable transistors and some other fine tuning functions to build a more advanced version.
Let us first distinguish two Fuzz Face eras. Arbiter Electronics Ltd has used NKT275 PNP germanium transistors to manufacture Fuzz Faces since 1966. NKT275 sounds good, but as we all know, the sound quality is not consistent and its performance depends on the ambient temperature. Arbiter merged with Dallas Electronics Ltd around 1968, and by the end of that year, Fuzz Faces was made with NPN silicon transistors.
PNP stands for positive/negative/positive, and NPN stands for negative/positive/negative. They don't want to understand the field of transistor manufacturing, but all adopt a "sandwich" structure. The middle (base) layer of the PNP transistor is negative, while the outer layers (emitter and collector) are positive. In the NPN transistor, the polarity is reversed. The base is positive, and both the emitter and collector are negative.
In addition to the acoustic difference between germanium and silicon, this is important. The PNP Fuzz Face circuit is not compatible with the power supply running modern pedals because the positive pole is grounded instead of the conventional negative pole. A PSU with an electronically isolated output may work, but it is not ideal. Many old and old Fuzz Face users quit their jobs and use batteries. For the sake of simplicity, I first use the Fuzz Face NPN silicon transistor that can be powered by a standard power supply.
If you think the price of old tubes is going crazy, try researching old transistors. This is especially true for the "Holy Grail" transistors used in classic treble boost, wah and fuzzy pedals. My advice is not to be too obsessed with everything, and to be cautious in buying expensive NOS transistors, and there is no guarantee that the seller will not leak and not have enough revenue.
The NPN silicon resistors used in Fuzz Faces include BC108C, BC109B, BC109C, BC183L and BC209C. You can find these parts online from component suppliers such as Rapidonline.com and cracklewoodelectronics.com-in fact, you may be able to get all the parts for the project from one of these two points of sale.
In order to fully analyze the germanium and silicon Fuzz Face circuit,
– There are some solid suggestions about transistors, and a very simple small circuit for testing transistor leakage and gain. I used it to test my transistor inventory and found some leaks. It is not uncommon and leaked should not be used. Fortunately, I did find some things that would not leak, and wrote their gain levels on the side of the case.
It is easy to find printed circuit boards for PNP and NPN Fuzz Face circuits, but they are not actually needed. This structure is very simple, it is easy to assemble on the labeling strip, and you can even make perforations or turrets yourself.
I first draw the circuit layout, which only requires a small board and eight drill holes. You can use fiberboard or epoxy glass board-something with copper on one side is fine, but you must first remove the copper layer by soaking the board in a PCB etchant solution. If you are a fan of DIY reproduction, you may already have an etchant solution (ferric chloride) because it can be used to artificially age nickel-plated guitar parts.
After cutting the board, mark the position of the hole and drill the hole with a 2mm drill bit, then install the component, and fold the lead wire back to fix it in the proper position for welding. I put all the solder joints on the back of the board and cut off the excess wires. This is not the most elegant construction method, but the circuit is actually point-to-point connected and very easy to implement.
Just make sure that the transistor wires are connected correctly. The base line will always be in the center, and the emitter line may be marked with a small label on the housing. Please refer to the provided wiring diagram and find the selected transistor online to confirm the connection.
There are drilling holes in my metal casing for controlling the tank, jack and on/off switch. I also used a 15mm nylon bracket and two screws to mount the board to the chassis. The input capacitor is connected between the board and the input jack, and the output capacitor connects the board output to the volume controller.
There is also a 20uF capacitor, I soldered it to the fuzzy controller's tap and both ends of the ground wire. Make all the switch connections and install the battery clip. The positive electrode is welded to the connection point of the 33K and 470R resistors, and the negative electrode is welded to the ring label of the input jack.
If you follow the diagram carefully and form a firm solder joint, the fluff box should work for the first time. Congratulations on your job well, but does this sound good? If you can, then you are lucky, and your work is done. If not? It is almost certain that this is bad luck, not bad construction.
My voice is obviously average. There is not much sustain, and the notes are eventually cut off instead of disappearing evenly, so it's like many old Fuzz Faces and some boutique clones. It sounds better, and I will do something about it.
Accepting that some Fuzz Faces is "magic" in a way, while others sound mediocre as fuzzy logic. No decent amplifier manufacturer will simply invest in a pair of power tubes and hope to achieve the best. Instead, they will check the voltage and measure the bias settings to make sure they are working as required. They can even adjust the bias within safe parameters to achieve specific overload characteristics, enhance headroom or optimize dynamic response.
Transistors are no different in this respect, and those "magic" Fuzz Faces are those transistors, which happen to be non-leakage and are perfectly biased by reserve resistors. The people at Arbiter didn't choose transistors carefully and biased them toward the ears, which is why they vary so much.
Instead of 33K and 8K2 resistors, I put in several 20K adjustment potentiometers. Solder the tap to one of the outer legs and it will become a variable resistor. If you have a multimeter, you can preset it to a specified value.
It is another great Fuzz Face resource. You will find all the recommended voltages in all important positions of the circuit, but you don’t have to worry too much about the voltage that matches the pedal. The best way to set up any Fuzz Face is to use ears. When playing, adjust one trimmer at a time to hear the sound changes.
In one extreme case, you will hear fierce fluff, with little or no sustain, and no gating effect. I prefer to set my tone to be smooth and have a long or even attenuated tone. It’s also worth mentioning that the guitar is turned down one or two levels to see how the skew setting affects the sharper Hendrix sounds that roll back.
This is interesting because if you listen carefully and take some time, you should be able to turn a normal fuzzbox into a fantastic box. After all the adjustments, it may be enough for you, but there are some interesting other mods to consider.
Despite his recent controversy,
Some effective adjustments have been made to the Fuzz Face concept. My favorite is a 50K potentiometer, which is connected as a variable resistor between the input socket and the 2.2uF input capacitor.
According to guitar electronics expert RG Keen, it "increases the apparent source impedance of the pickup." The electronic description is a bit complicated, but the mod adds clarity and provides a more useful and progressive response to the guitar's volume control. The sheer blur is somewhat lost, but still more than enough, and the attenuation is smoother. The bass becomes tighter and the definition is better. If you lower the volume of the guitar to about 7 or 8, and then gradually exit the bias control, you can hear where it reaches its best effect, and you can improve clarity without losing too much circumference.
Although many people like their fat and subtle flavor, some players criticized Fuzz Faces for excessive bass, which sounds a little dull. This can become muddy and give the circuit a dull sound quality-especially guitars equipped with humbucker.
Replacing the 2.2uF input capacitor with a smaller value capacitor will prevent the lowest frequency from reaching the first transistor. The smaller you go, the less bass will penetrate.
Experiment with different values to get the best bass response for your guitar and amplifier-I recommend 0.47uF or even 0.22uF as a reasonable starting point. Using low-value capacitors means you can try film covers instead of electrolytic capacitors, which may bring color benefits.
You can make this bass roll-off as a permanent feature or a switchable option. To make it switchable, please install a smaller capacitor instead of 2.2uF, and then connect a larger capacitor in parallel with the switch to the smaller capacitor to establish and disconnect the connection. Combine 0.22uF and a switchable 2uF capacitor, you will get 2.22uF.
Although germanium transistors are associated with a positively grounded PNP fuzzy plane, you can also use NPN germanium transistors. They will plug directly into the circuit without changing the power supply or battery connection. I am using a pair of AC176 transistors and they are very cheap compared to "classic" PNP germanium fuzzy transistors.
Replacing silicon with germanium will require more trim pot adjustments. Arbiter also uses a 330R resistor in the germanium circuit instead of a 470R resistor, but changing it to 330R is not necessary.
Using the 3PDT toggle switch, the fuzzy box can be operated on two types of transistors. You can also combine silicon in the first stage with germanium in the second stage, and vice versa. Or, switch between different types of silicon transistors-it's all up to you.
For this, I made a larger circuit board and used my favorite turret for soldering-it had to be bigger to accommodate four trimmers. I installed the toggle switch between the fuzzy control and the level control to provide protection, and connected it to the circuit board.
Since all four transistors are biased towards the ears, silicon sounds brighter, tougher, more aggressive, and lasts longer. When you exit the guitar volume, the germanium sounds warmer, the gain is lower, and the tone is sweeter. The combination of silicon and germanium is also very good. Provides different blur textures and compression characteristics.
The transistor switch version of this pedal requires more work, but it is worth the effort. The AC176 transistor is the star of this exhibition for me, so I plan to try some alternative silicon transistors in the future. Think of it as exchanging tubes in an amp.
I will be the first to admit that this pedal lacks visual appeal, but it is indeed similar to the boutique fuzzy box inside, and it sounds a lot like it. Please feel free to draw your own conclusions when I decide on the surface treatment, graphics and luxurious vintage knobs. Happy welding, don't burn your fingers.
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