Audio Amplifier





Introduction: Audio Amplifier

This is a simple (maybe) instructable on how to make an audio amplifier using a LM386 audio amplifier chip. The cup helps with the sound ;p.

Just found this.  Check it out, looks decent

Step 1: The Parts

I'll say this right now: Special thanks to This website has the greatest instructions and the easiest-to-read circuit diagrams

You will need:

-100k Potentiometer
-.1 micro farad capacitor
-220 micro farad capacitor
-10 micro farad capacitor --only necessary for the 200k boost loop
-LM386 microchip (or whatever it's called)
-Soldering Iron
-small circuit board
-headphone jack
-speaker -- your own

-plastic cup

Note: I added a breadboard that I drew up from the circuit diagram, so if someone wanted to double-check it that would be nice

Step 2: Liberating the Audio Jack

Cut the wire a couple inches away from the jack (you want a little room to play with it. I didn't do that)
Strip the wire
Strip the insulated wires, making sure that you don't strip them so far that the stripped part touches the non-insulated wire
EDIT:   Don't twist the two (formerly) insulated wires together, it might hurt sound quality.
Those (formerly) insulated wires are the positive and the noninsulated are the ground.

Check out my instructable on headphone repair for more about headphone wires.

Step 3: Place Everything on the Board

Put everything on the board. This step helps you use the smallest amount of circuit board possible, which results in a smaller amplifier.
Here's how I set up mine

Step 4: Make All the Connections Underneath

Just follow the circuit diagram. Make sure you read all the comments on the pictures in this step--it'll help a lot.

Step 5: Double-Check All Connections and Finish

Double-Check all connections for short circuits and bad connections. Then, once everything is in place, test it out. To improve the sound a bit, cut the bottom out of a plastic cup and place it over the speaker.



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    112 Discussions

    Do you knoweth of an amplifier circuit that only useth transistors but still pertaineth effectivity?

    1 reply

    Do you knoweth of an amplifier circuit that only useth transistors but still pertaineth effectivity?

    Do you knoweth of an amplifier circuit that only useth transistors but still pertaineth effectivity?

    i build this in a past few days but my amp wont work properly i mean it sound but in very weak and distorted sound i don't put 10 uf cap in pin 1 and 8 in my country lm386 it's don't look lm386 in radio shack i live in south east Asia ,Philipine

    can anyone help me to figure it out the problem

    sorry if this is a bother but while amps are rated in watts we do not hear watts we hear in a scale rated in dB's. Watts alone are not enough what really determines the volume and the quality of the sound we hear is the speaker, the driver. All speakers are different you can get a lot more volume (dBs) from a more efficient speaker given in the SPL number of the speakers specs. xx db @ 1W/1m the higher the number the more efficient, the louder given the same amount of power (watts) supplied a SPL number of 99 dB 1W/1m will be louder and more efficient than one with SPL 90 dB 1W/1m.
    when selecting speakers look at the SPL number and the power handling (watts), match and balance them to the amp intended. hard to do when using preassemble speaker cabs. though when watts is generally all you are given.
    I like the cup! I used a cutoff water bottle for a similar effect. ;-)
    uncle frogy

    i am trying this but I am having a hard time on my beadboard only thing that is different is i am using LM358N would it work using it?

    2 replies

    It's going to need a different schematic. The 358N is a dual op-amp design, so you need to follow the schematic entitled "AC Coupled Inverting Amplifier" on page 17 of the datasheet:

    Note that to use both op-amps in this chip, you'll need to buy twice the quantities of all of the resistors, capacitors, and potentiometers that are shown in the schematic.  The Av term stands for gain.  The potentiometer isn't shown in that schematic.  You can use the 100K potentiometer just like in this instructable.

    I was just wondering I knew it could be used and it is all I have. I will go to jameco and buy the LM386 and the mpf102 for another project.

    i built the circuit on a breadboard, but instead of hooking it to a speaker i hooked it to a female headphone jack. it worked perfectly, but when i built it on the circuitboard theres no bass at all

    i also made this circuit. first on a "bread board" by following the "bread board" diagram and then made the circuit on a circuit board which i had made following the circuit diagram. and it is sort of working but with extremely bad sound quality whereas it worked very well on the "bread board". i have recently noticed that on the circuit diagram the 7th pin/ leg of the chip isn't attached to anything whereas on the "bread board" diagram it is the 6th leg that is not attached to anything. is this the reason why my circuit board is not working? please get back to me

    1 reply

    your power source or Vcc as we call it should be connected to the sixth pin of the LM386 IC but on the bred board it is shown on pin7, just change the ports..

    and little bit more info:
    pin 7 is for bypass any high voltage between 4 to 18 volts will cause the output to be a bypassed one that is there wud be no amplification , you will het the same low power output you received from the mp3 player or you phone or whatever your source of signal was

    correct me if im wrong but shoudnt pin 7 be left alone...
    its for bypass
    you should have com\nnected the power port to pin 6 on the right hand side..

    well you know that coz your speakers worked butthe schematics on the bread board are somewhat wrong

    Why is the schematic so tiny? It's hard to see once it's cluttered with the yellow boxes.

    1 reply