Simple Audio Amplifier - DIY

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Introduction: Simple Audio Amplifier - DIY

About: Sam Technology Professional is an independent educational organization teaching, developing & Inventing Electronics Projects. More at: http://samtechpro.blogspot.com & http://youtube.com/samtechpro

Welcome to "Sam Technology Professionals" again..!!

This is a cool audio amplifier and it is easy to build. Only few components are required. It is based on IC LM386 and you know what i just love this IC as it is useful for several kinds of projects.

I suggest you to use thick wires because that can prevent the distortion in output signal. If you are creating it on PCB then you need to make the tracks wide.

So here is the picture where you can see that how it looks like when i added an 220v AC to 9v DC bridge rectifier.
You can also use a 9v Battery for it.

Here i attached the picture of speakers that i used with it for testing and it worked well on these speakers too.

Step 1: Components:

As i mentioned that only few components are required to build this beautiful amplifier. So here is the list.

* IC - LM 386 or C386
* Capacitor 100nf
* Capacitor 0.047uF = 47nF (473 is the code)
* Capacitor 330uf at 16v (You can also use 220uf or other that's your choice)
* Capacitor 100uf at 35v
* Resistance 10 Ohm [ 0.25Watt ]
* 9v Battery or a 9v DC power jack (female jack)

If you think that its hard to find any of above component then you can get them from e-bay because its much cheap radioshack store.
And if a component is hard to get for any other reason then you can comment here i'll tell you its alternative or i may refer you to contact "Sam Technology Professionals" to get the component free at home.

So have a look of its schematic

Step 2: Circuit Diagram:

Here is its schematics and i hope that every thing is clear in it. But if you have any question you are free to ask me here. I promise to give your every question's answer.

Control the output gain with 10k Potentiometer (I will prefer an audio pot not linear pot - but you can use linear too)

You can see that 1-8 points of the IC isn't connected. You can connect them with each other by putting a capacitor.

Want to change the sound..??? Remove the capacitor 100nf from 7th pin of IC and from GND. Then put the capacitor 10uf between 1st pin and 8th pin. Then  observe the output gain. You can change the value of the capacitor 10uf to set the type of output.

Start Constructing It. I believe that you can do it easily.

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    31 Discussions

    I would like to build a pair of these as headset amps. The headsets are 32 ohms, designed to connect to a computer earphone output (so they are low power, probably under 1/4 watt). I'd like to take line level as an input to the amp. Will this amp overdrive these headphones? How would I change the circuit to handle the lower power output? If I build two of these to provide stereo amplification, can they share C3 (100uf cap)? Can they share C4 (100nf cap) or does each LM386 need its own?

    1 reply

    They can only share c4. And yes this amp can overdrive headphones and create distortion. There are couple of ways for using it with headphones like limit input with a big resistor like 47K. This resistor will be at input of the chip 386. Otherwise you can take a look at this article which shows how you convert any amplifier output to headphones output.
    https://samtechpro.blogspot.com/2014/03/how-to-use-speaker-output-for.html

    what if i had two speakers should i make another amplyfier or connect those + - to the other speaker

    1 reply

    Yes if you need to make a stereo amplifier then there must be another amplifier for that channel and speaker with the common ground of this amplifier.

    Hello Sam!

    This is my first scheme and my questions are probably silly, but I would be grateful if you could answer them.

    1)If I have 2 speakers, i need to build a separate amplifier for each one?

    2)About the "Input" part of the scheme: where does a ground wire of my audio cable go? It should be connected to the ground of the circuit?

    3)Polarities aren't specified for some capacitors (C4, C2 and C5)

    4)Triangle at the bottom of the scheme means grounding? Can I go without it?

    Thanks in advance!

    4 replies

    Yes you can build separate amp for the other speaker.
    The ground wire is the common wire. You assemble the circuit board and connect all grounds together. And as you know that it is working on the battery (which generally means) singal supply. So here the ground common point will be considered as the -ve of your battery. And so the input has ground too which is a common point in audio signal. For example if you are using a 3.5mm stereo jack then you may know that it has three points on its pin jack. The tip of it is 1st channel say right and the center one is left so the remaining one is ground what you can connect with this amp's ground terminal.

    Thank you very much, it cleared things for me. But I have a problem now - I just tested the amplifier - for a short period of time i heard hum from the speaker and then silence. I looked at components and noticed that 330 uf capacitor is blown. I powered amplifier via 220v AC to 9v DC adapter. I checked connection of the amplifier components and all seems to be right. Just a faulty capacitor? Maybe i should use 220 uf?

    Yes a 330uf if blown can cause the hum but many times the hum comes from the mains as you mentioned that you are using an adapter for that. To prevent this put another capacitor of big value like 1000-4700uf between pin6 and ground. This will kill the main hum. And also check out my latest post that contains simple and good modification of this circuit will provide you cleanest sound possible.

    3) The polarities are not given for the non-polarized capacitors. because the capacitors you're talking about are ceramic type and they don't have that polarity they can be connected in any direction.

    4) Yes triangular symbol is a general symbol of common ground.

    Why does the component list say 473 pf? it is not included in the schematic. Am i missing something here?

    3 replies

    i think 0.047uF is the capacitor you're talking about. And the exact value is 0.047uF and 473 is the code of the capacitor in the ceremic shape.

    Hi sam, Thanks for the quick reply.

    I noticed my mistake an have bought the correct capacitors now!

    Thanks

    The 47nf in the schematic is 0.047uF and 473 is the code of the capacitor

    Sure it will work on 8ohm speakers too. I used it on two 8ohm speakers for years

    What wattage would you suggest for 4ohm, 8ohm and 16ohm speakers? Do you know the output power?

    In parallel or series? Because that would represent either 4 or 16 ohms.

    But yeah, this amp's small amount of power handling should not be very sensitive to impedance mismatching.

    i used two lm386 amp circuit to built a stereo amp and used a stereo pot. i used two 8 ohm speakers for each.