LM 386 Audio Amplifier Project

The LM 386 is an inexpensive audio amplifier chip which is available in almost any electronics retail shop.  The big advantage with this amplifier chip is that you don't need alot of parts to get it up and running and although there are a lot of substitutes for this kind of amplifier it still remains the hobbyist's audio chip amp.

The datasheet for the LM 386 can be found here: www.nari.ee.ethz.ch/wireless/education/PPS/PPS02/doc/LM386.pdf

Anyway, if you google "LM 386 audio amplifier projects" you will realise that many people have built this amplifier before and infact its not that easy to get it working in the beginning itself. 

It can start making a lot of buzzing and hissing which can confuse you and make you abandon this chip amp.  LM 386 itself is hated by many (yea lol) but heres my completed version of the LM 386 chip amp.

I mounted the whole thing on a bare piece of perfboard that I had.  If you are wondering what the "M" symbol is for well its just a shiny motorola cover that I had so I glued it onto the switch.  I tested it and it works fine no buzzing or hissing no issues with my build and thats why I wanted to share this build with you people.  

Here is the schematic of my build and I have to admit that I had to go through alot of troubleshooting before getting the LM 386 to work properly hence my final design.

I forgot to mention that this amplifier can put out about 1 Watt RMS into an 8 ohm load (refer to datasheet for more details).  Its quite loud but don't expect it to rattle your windows.  Its rather more suited for battery powered applications like making portable audio devices and so forth.

As you can see in the schematic, my overall design doesn't differ much from what is mentioned in the datasheet of the LM 386, however I have added a coupled of features like input decoupling capacitor C5, I also added C6 and C7 which form an effective power supply filtering circuit.  R1 is a 10 K potentiometer and also resistor R3 and capacitor C8 form a feedback loop that help reduce noise further. The idea behind using C8 and R3 is not mine I just saw it on the web I can't remember where exactly. The rest of the schematic is lifted off straight from the LM 386 datasheet.

Make sure you use a speaker of impedence 8 ohm or higher to avoid killing the little audio amplifier.

PARTS LIST:

Don't use the LM 386 with a higher voltage than the parts you have can take eg. If you intend to use the   LM 386 at lets say 12V well don't buy any parts rated at under 12V (thats logical  but still need to mention)

Capacitors 

C1                                       220  uF (Electrolytic)

C2                                       10    uF (Electrolytic)

C3                                       10    uF (Electrolytic)

C4                                       0.05 uF (ceramic) - - - - If you can't get the exact value get one close to it

C5                                       0.1   uF (ceramic)

C6                                       0.1   uF (ceramic)

C7                                       100 uF (Electrolytic)

Resistors

R1                                       10 K potentiometer

R2                                       10 Ohm resistor

R3                                       10 K resistor

Speaker  - - 8 ohms or higher