LM386 Stereo Amplifier

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The magic surrounding the LM386 is mostly because of how common it is, how easy to use it is and the cost. I purchased a bulk package of these IC's off of eBay some time ago. They have made their way into a few radio and audio projects, and I will have no issue using them all in future projects.

I recently built a small arcade machine around a Raspberry Pi computer, and I needed a solution for providing the audio component. This was not the easiest way to get sound into the cabinet, but I feel it took the customization up, and added a component showing that I could handle DIY electronics too, and I don't need everything to be "plug and play".

 While most of the parts I already had available to me, I feel that sourcing the parts from the fine vendors in China over eBay drove the cost of this project down. I would be surprised if the cost of this board was greater than 5 bucks. The most expensive part of this project was buying the actual speakers, which I found at the local surplus store at a reasonable price.

Q: I thought the LM386 IC was only capable of handling one signal, stereo is two signals?
A: True, this is why we used two chips to produce the desired results!

 

Q: How do you get two separate signals going to two different chips to amplify at the same level?
A: With a dual potentiometer! (In this project I selected a dual 10K potentiometer with a logarithmic taper).


Q: Can I drive my giant speakers with this?
A: Nope, think headphones and small projects (~1/2 watt per channel).

Q: Why don't I just buy an audio module off of eBay instead of building my own?
A: You're only learning how to buy stuff, build something on your own and learn.

In this project I knew I would be stealing power from the 5V rail on the Raspberry Pi. For your information: LM386 IC would like to see 4-12VDC, except for the LM386N-4, which likes to see 5-18VDC. (It's common to see LM386 Projects supplied from 9V batteries).

Another consideration: depending on the project, you may wish to use a small value capacitor (Think 0.01uF or 0.001uF) to remove the DC component of an audio signal, this was necessary for my FM radio project: TEA5767 FM RADIO W/ ARDUINO.

It's up to you how you make the connections!
I ended up hacking a 3.5mm extension cable in half to get a male audio adapter for my circuit (I simply soldered the wires directly to my perf. board. I used screw terminals to hook up some small stranded wires as the speaker wire running to the speakers.

The only really unique aspect about this project is the linear taper dual potentiometer. If you google the datasheet for the LM386 you will see several different configurations, and some may be more well suited to your project than what I'm using. I decided to use the configuration with the lowest part count.

****Use bypass caps to reduce noise and clean up the audio****
(See schematic)

 *You don't need to use electrolytic capacitors, I just used what I had - replace 220uF with a poly type if available.

I added the bypass caps after I built the board, I would use space more effectively if I repeated this project.

There you have it, a cheap and easy stereo amplifier for small projects!