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How to Make a Homemade 20 Watt Audio Amp

Amplifiers are electronic circuits that increase the voltage and current levels of an AC signal. Circuits that will be used for audio amplification must faithfully reproduce the signal; otherwise, when the signal is reconverted into an audio wave, unwanted sound distortion will appear. One way to produce a high-fidelity signal is by using a Class-AB amplifier circuit. Two 15-amp transistors can be used in this circuit to create a maximum output level of 20 amps.

Things You'll Need

Electrical wire
Electrical pliers
Electronic solder
Soldering iron
Audio plug
2 100-microfarad polarized capacitors
TIP3055 NPN transistor
TIP2955 PNP transistor
2 1N4007 diodes
2 1-kiloohm resistors
6-inch round speaker
4 Solder-type ring terminals
2 Machine screws
2 Machine nuts
12-volt lead-acid battery with L-type terminals

Instructions

- 1
  Cut seven pieces of wire, with each piece being six-inches long. Strip 1/2 inch of insulation from the ends of each wire segment.
- 2
  Place one end of the first wire on the audio plug's tip terminal. Melt a small drop of solder to join the wire to the terminal. Use the tip of the soldering iron to smooth out any lumps in the soldered joint. Use this technique to solder one end of the second wire to the sleeve terminal on the audio plug.
- 3
  Twist the negative leads from both capacitors together with the loose end of the first wire. Solder this electrical joint.
- 4
  Twist together the positive lead from the first capacitor, the anode lead from the first diode and one of the leads from the first resistor, and then solder this twisted wire joint to the base lead on the NPN transistor.
- 5
  Twist together the positive lead from the second capacitor, the cathode lead from the second diode and one of the leads from the second resistor, and then solder this twisted wire joint to the base lead on the PNP transistor.
- 6
  Twist together the cathode lead from the first diode with the anode lead from the second diode. Solder this electrical joint.
- 7
  Twist together one end of the third wire with the emitter leads from both transistors, and then solder this electrical joint. Solder the loose end of the third wire to one of the electrical terminals on the speaker.
- 8
  Twist together one end of the fourth wire with the free lead from the first resistor, and then solder this wire pair to the collector lead on the NPN transistor. Place a ring terminal over the loose end of the fourth wire and solder the terminal to the wire.
- 9
  Twist together one end of the fifth wire with the unoccupied end of the second resistor, and then solder the electrical joint. Place a ring terminal over the loose end of the fifth wire and solder the wire to the terminal.
- 10
  Solder one end of the sixth wire to the remaining speaker electrical terminal. Place a ring terminal over the loose end of the sixth wire and solder the wire to the terminal.
- 11
  Twist one end of the seventh wire to the collector lead on the PNP transistor, and then solder this connection. Place a ring terminal over the loose end of the seventh wire and solder the terminal to the wire.
- 12
  Place a ring terminal over the loose end of the second wire and solder the terminal to the wire.
- 13
  Place the ring terminals connected to the second, fifth, sixth and seventh wires over the shaft of the first machine screw. Insert this machine screw into the negative battery terminal and screw on the first machine nut so that it holds the screw and the ring terminals snugly to the battery terminal.
- 14
  Place the ring terminal connected to the fourth wire over the shaft of the second machine screw. Insert this screw into the positive battery terminal and screw on the second machine nut so that it holds the screw and the ring terminal snugly to the battery terminal.

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