Price - Stock No 415


This low cost amplifier provides modest amplification from a headphone jack.






  1. Check  the  P.C.Board  for  damage to tracks.  Any breaks can be soldered over.  Check with a multimeter or electronic circuit tester.
  2. Identify the three resistors, see Resistors.
  3. Insert the resistors and solder in place - see Soldering Technique.
  4. Insert the IC socket taking care to orientate the locating dot.  Solder in place.
  5. The 6 PCB pins can be inserted and soldered.
  6. Identify the two greencap capacitors, locate their positions and solder, see Capacitors.
  7. Care needs to be taken ensure the electrolytic capacitors are inserted with the correct polarity.  Note the values and polarity of the capacitors and solder in place. 
  8. The switch can now be soldered to it's PCB pins.
  9. The battery holder is inserted from the copper side of the pcb and needs to be stood off the board to allow access for the soldering iron.  Care should be taken to ensure excess solder does not short circuit the PCB - solder in place.
  10. Cut the figure 8 wire into two suitable lengths.  The ends of the wire needs to be stripped to bare the copper wire.
  11. Tin the bare ends of the wire - refer Tinning wire.
  12. Attach the speaker with one length of fig. 8 wire - note the polarity.
  13. Attach the headphone jack with the other length of fig. 8 wire.  The tip of the jack is positive.
  14. Adjust the legs of the LM386 to match the socket width.
  15. Insert the IC with the locating dot as shown in the placement diagram.

Operation and Testing

  1. Insert a 9V battery. 
  2. Connect an audio source to the input jack and turn the switch on.
  3. Use the volume control on the audio source to adjust the output volume.

Technology Notes

View the Datasheet for the LM386.

Trouble shooting

Troubleshooting,  if necessary will involve careful checking of locations and polarity of components, in particular the LM386, 1he 100uF and 470uF capacitors.  Re-solder all joints and check to make  sure you have  not  bridged across  between  any  two adjacent component legs.  The end  of  a  broken  hacksaw  blade  sharpened  on  an  emery wheel is a good tool for cleaning between soldered joints.


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