DIY Mono Amp for Headphone Jack LM386

A headphone amplifier increases the signal from an audio source for playback over a set of headphone speakers. Since headphones are placed directly over the ears, the amplification factor (or "gain") does not have to be very large to provide dramatic results.



One common means to construct a headphone amplifier is by using an audio-specific operational amplifier integrated circuit, such as the LM386 operational amplifier. An operational amplifier (or "op-amp" for short) is a small, prefabricated circuit that contains the electronic components that are necessary to produce a high-fidelity output signal.

• 1

  Cut seven lengths of wire. Strip half an inch of insulation from each wire end.

• 2
  Sample audio plug. The interface connections (from left to right) are the sleeve, ring and tip. mini jack image by fderib from Fotolia.com

  Solder one end of the first wire to the non-inverting input terminal (pin 3) on the op-amp. Solder the other end of this wire to the Tip terminal on the audio plug.

• 3

  Solder one end of the second wire to the Tip terminal on the audio jack. Solder the unoccupied end of this wire to the output lead (pin 5) on the op-amp.

• 4

  Solder one end of the third wire to the inverting input terminal (pin 2).

• 5

  Solder one end of the fourth wire to the "Vs" terminal (pin 6) on the op-amp. Solder one end of the fifth wire to the "GND" terminal (pin 4) on the op-amp.

• 6

  Solder one end of the sixth wire to the Sleeve terminal on the first audio plug. Solder one end of the seventh wire to the Sleeve terminal on the second audio plug.

• 7

  Twist together the free end of the fourth wire with the red wire from the battery connector. Solder this connection.

• 8
  The amplifier circuit will operate only if the battery is plugged in. nine volt battery image by JoLin from Fotolia.com

  Twist together the unoccupied ends of the third and fifth wires together. Twist together the unoccupied ends of the sixth and seventh wires together. Solder both twisted wire pairs together with the black wire from the battery connector. Plug the battery into the battery connector.

• 9

  Plug the first audio plug into the audio output device (such as a speaker or amplifier jack). Plug the second audio plug into the audio input device (such as a CD or MP3 player).