I love the LM386. It’s a complete amplifier in an 8 pin DIP chip! All that is needed to build an audio amp are a few external components most of which are decoupling capacitors. It is well suited to low power applications and runs just fine on a 9 volt battery or any voltage supply from 4-12 volts. It has a low quiescent current drain of only 4mA so it won’t kill a battery right away if you leave it on and idle. The gain is internally set to 20 but the addition of an external resistor and capacitor between pins 1 and 8 will increase the gain to any value from 20 to 200. An increase in bass frequency can be facilitated by adding a 10K resistor and .033 uf capacitor in series between pins 1 and 5.
The parts list for this build is pretty minimal:
1 – Enclosure of your choice
1 – LM386 Audio Amplifier 8 pin DIP
1 – 10 ohm resistor
1 – 10K potentiometer
1- 220 uf polarized capacitor
1 – 100 uf polarized capacitor
1- 10 uf polarized capacitor
1 – .01 uf ceramic capacitor
1 – .047uf ceramic capacitor
2 – 1/8″ mini audio jacks
2 – 1/4″ audio jacks
1- 9 volt battery clip
1 – 9 volt battery
1- small perforated circuit board
Some hookup wire
A speaker of your choice for output.
I suggest building the circuit on a bread board first. It’s much easier to troubleshoot and find errors and you can easily experiment with different components. You’ll also learn more as you can see what each component does by removing it or changing its value. You can leave the audio jacks off the output and install some small binding posts or just two wires with alligator clips on them for connection to an external speaker. You could also put the whole circuit in a larger enclosure and install the speaker for an all in one portable amp.
This amp can be used to amplify any low level audio signal like an mp3 player or even a guitar or bass as you’ll see in the video.
All of the parts required can be found at Radio Shack and shouldn’t cost more than $20. Have fun building your amp and keep on hackin!