Guitar Fuzz/Distortion

Guitar enthusiasts and novices may be discouraged by the prices of professional Fuzz and processors. This is an inexpensive method of converting your old pre-amp into guitar fuzz, requiring only three inexpensive components. I spent a total of less than 1$ US on this piece.

Pre-amplifiers are technically known as 'Voltage Amplifiers'. The fuzz unit described below distorts part of the sinusoidal to produce the infamous harmonics of 'Rock Guitarists'.

Step 1:

Open your old pre-amp and try to locate the voltage amplifier 'Transistor'. This is quite simple; just follow the path of input signal (music) until it leads to a first stage transistor.

Step 2:

Your analysis of the circuit continues and you need to determine the number of amplification stages. This could vary between 1 and 4.

Step 3:

Determine the amplification stage that provides a 1V p-p signal output; this is mostly the last stage of the Pre-amp. It is advisable to work on the fuzz section at this stage so that we can accommodate a variety of input impedances.

Step 4:

Determine the base of this transistor. Simply touch on this section with a small screwdriver to hear the reproduction of sound on the speaker. The base provides the louder level of noise.

Step 5:

Analyze the circuit designed around this base. It usually consists of an input feed through a capacitor. It most probably is driven by a resistor-voltage divider pair. Try to determine the ratio of division of Upper resistor (connected to positive voltage polarity) and the lower one. This approximates the cut-off point.

Example: if Voltage is 9V, Upper resistor is 2K ohms and lower is 1K ohm. Then the ratio indicates a base voltage of 3 V. This is important to know to what extent you can drive a fuzz without burning out any of the components.

Step 6:

A diode consists of two connector ends. One end is called the 'N Junction', distinguished by a 'marking/dot'. The opposite end is called the 'P Junction'.

The 'P' type and 'N' type are common classifications for semiconductors. They denote the primary carriers (i.e N-type electrons and P type holes).

After identifying the P and N ends, connect the 'P- end' of the diode to the base of the transistor terminal and the N junction to a 100 K ohm potentiometer control. The wiper of the potentiometer is connected to a 220 ohm protector resistor.

The typical values of the components required are

  • IN4001 diode or equivalent
  • 100K Potentiometer
  • 220 ohms resistor (can be identified by the colour coding Red Red Brown)
Step 7:

Then root this resistor end of the circuit to ground (negative polarity of power supply).

Step 8:

Plug in your guitar and play....tune the pot to vary Fuzz effect.

The above circuit works by 'chopping off' the positive swing of the input sinusoidal. The extent to which this 'chopping off' occurs is governed by the setting of the potentiometer. This can be varied from a light fuzz to heavy metal distortion.