Introduction: Audio Amplifier

Picture of 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

Picture of 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

Picture of 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

Picture of 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

Picture of 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.


Max Cordell7 (author)2016-05-10

Works great thx

Einstein Jr (author)2014-09-23

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

NateTite (author)Einstein Jr2014-12-28

are you still looking for a transistor version of this??

Einstein Jr (author)2014-09-23

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

Einstein Jr (author)2014-09-23

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

Bulantuy (author)2012-10-19

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

uncle frogy (author)2012-03-18

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

WakeUpWolfgang (author)2011-12-29

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?

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.

nodoubtman (author)2011-11-15

the sound is too noisy i cannot understand anything :(
please help me!


jablome (author)2011-11-09

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

depotdevoid (author)2011-10-31

Hey killersquirrel, I used a stripped down version of this circuit in my Human Dalek costume this year!  Thanks for the instructable!

mak24 (author)2011-10-24

the circuit is too noisy...

carik (author)2009-07-18

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

mak24 (author)carik2011-10-22

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

mak24 (author)2011-10-22

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

n0ukf (author)2010-02-06

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

David97 (author)n0ukf2011-09-23

He should put a un-marked version of shhematics

knektek (author)2010-07-16

All of this wattage business is very misleading. It doesnt mean that the higher the wattage the more the quality of the sound. You need to 'tweak' the system so that you can produce the best sounds.

killersquirel11 (author)knektek2010-07-18

Wattage is more or less equivalent to volume. I never made the claim that it would improve the quality. How would you recommend 'tweaking' the system?

knektek (author)killersquirel112010-07-18

By tweaking the system, I mean by copying the circuit onto a breadboard and instead of the caps and the resistors use variable caps and potentiometers. With those experiment and see what combo makes the best sounds, use the combo on the circuit board.

knektek (author)2010-07-14

for more gain, use a resistor in series after the cathode of the cap. A 1.2K resistor would go great!

rodeljames (author)2010-03-15

can this amplify on a computer speaker??
if not what device should i usefor this amplifier...
can you also teach me how to connect the audio plug..because i cannot understand the instructions...

thank you

emedina94 (author)2009-11-23

 will this amplify a guitar or bass. i need a portable amp

Yes this would work, however it would be so quiet that it wouldn't be practical for a guitar/bass amp (the very minimum I would go for a guitar/bass amp would be probably 15/20W, but keep in mind that if its battery powered then that means 15-20 amp-hours per hour of play time you want).  This will probably not even reach 1W.

Jodex (author)killersquirel112010-01-30

Well, the watts don't always really tell the real power of the amp. I have a Roland Microcube and it's two watts and you can get very loud sound out of it.

killersquirel11 (author)Jodex2010-01-30

Well it matters for bass.  Tweeters can get really loud on few watts, but if you wanted a bass amp you need a lot of power.

Jodex (author)killersquirel112010-01-30

Yeah.... Microcube is not the best bass amplifier, but really great with guitar! Enough bass.

killersquirel11 (author)Jodex2010-01-30

  hmm I just thought of something.. wattage has almost a 1:1 correlation with audience size.. the microcube @ ~2W is good for practice/playing for a few people.  A ~250W amp is good for a garage band playing for up to ~200-300 people.  ~100 is decent for a bar with ~40-120 people in it

Here's some links to various amp circuits that might help
10 W transistor
100-150W transistor
20W LM1875
56W LM3875
2x68W LM3886
the LM**** ones are going to be somewhat similar to this tutorial.

here's another one...

There's hundreds of these circuits on the web and with a little googling (just google: audio amp circuit) you can unearth many, many more than what I have listed above.

knoxarama (author)2009-11-03

Would an LM393 chip work?

looking at the datasheet, probably not, and if it would work, probably not with this schematic.  The LM386 is an audio amp chip, but the LM393 is used more for, as far as I understand, amplifying clock signals and other things like that.

pancho del rancho (author)2009-09-28

okay so u connect ground from the mp3 line im using to the battery then to the speaker

praveer (author)2009-08-17

Hey, awesome instructables. But I have a question. I am using an 8 ohm speaker, and have all the parts right, except for that last capacitor, (220 uf) which i replaced with a 470 uf; but the lm386 gets kind of hot, if I give it a 'greater that 6 v' input, allthough when I supply it with 4.5 volts, it gets slightly hot. I am casing this, and don't want to burn out the audio op-amp, so I would really appreciate it if you could help! Thanks! (And I read somewhere, but didn't understand, that the gain or impedence or load must match...i didn't understand)

un0 (author)2009-08-06

Is R1 control the amount of power going to the speaker (volume control)? and can you place a 10K potentiometer (variable resistor) between the capacitor and pin 8/1 for controllable gain?

toxicgasleak (author)2009-08-03

I have it all wired on a breadboard but the sound quality sucks. does anyone have any tips on improving the sound?

pancho del rancho (author)2009-07-31

um is there some sort of filter

if you mean a high pass or low pass filter then no if you mean a filter capacitor then yes

huh im new like to clear the music cuz i hear sometimes that once is on the copper board the quality goes down im new like a said so yea help da news

rkr (author)2009-07-01

I made this circuit... it didn't work that well at first, but I experimented around and got it to amplify much more. If anyone cares to know, it will work better if you solder the signal wire and the middle lead of the pot together, then tie those to (a separate, and I stress SEPARATE) ground. You can try it if you don't mind not having a volume control on the board.

anerudhan (author)2008-06-18

we could also use the LM380 IC ...... it has output power of 2.5 watts..... and also built in heat sink.......... ;)

hackerlife (author)anerudhan2009-06-19

Would the schematics for that be the same as this? Cuz if you ask me, 2.5 watts sounds like the way to go

hackerlife (author)2009-06-15

Hey man, I really gotta thank you for puttin' this up, I've been looking for a way to amp up some speakers for a while now! (I want to wire up my backpack... lol) So I can pretty much get everything I need at, oh, say, like a RadioShack, right? I don't know much 'bout circuitry, and a few of this parts seem a little specific... Like the LM386 chip... What the heck is that?!! Thanks again though

hackerlife (author)hackerlife2009-06-15

Also, step two is a little confusing for me... I want to try to make this for two speakers, am I better off just making two of these? I'm also probably going to just cut out the whole volume thingy... I don't really need that lol

If you're going to use two speakers then I would probably recommend getting a more powerful amp like

If you want two channels you'd either have to find a two channel audio amplifier circuit on google or build two of these

If you choose to go the two channel route then you shouldn't twist the two insulated wires together as one is for the left and one is for the right

Just remember... With enough googling you can learn anything

Ok, so, in the original plans, it said that you can build it to have 20x or 200x output (or something like that... it's 1 in the morning, and this is totally off memory) I suppose the 200x output is either not enough, or if it is, it is really low quality, and scratchy? As in too much gain...? So there's no way for me to just split the output wires in two and attach two speakers? That probably sounds really dumb, but I'm pretty new to circuitry. Thanks for all the help!

I was able to find the LM386 chip at my local radioshack, and mine's selection is fairly limited. Heres some more circuits if you can't find that part

cool, thanks!

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