Introduction: Simplest HQ Audio Amplifier
This is an updated version i 'm using this schematic from my BLOG post in 2013 when i designed a LM386 audio Amplifier and found that a bit noisy. So, after spending sometime i figured out that why the noise was coming. The biggest issue i founded was the 10Ohm resistor and 0.047uF capacitor between pin 5 and ground of the IC. I tested several values and found 0.1uF (code 104) very useful in bypassing the unwanted signals. So, here in the schematic you can see that we're using a 1K resistor at the input. I already explained about it in my BLOG in 2013 with a lot of details. Nothing very special they're acting as a passive mixer for the left and right channel input.
I think that the sound is clean enough to have fun. It could be your best portable audio tool. For more details about the circuit you can visit my old post. Below i pasted the text from blog post.
Firstly, lets discuss the input. So, in the previous circuit we used potentiometer and here i am using two 1K resistor parallel? No, they're not parallel. They are the left and right channels for input. This is due to many persons asked me about "how to use it to listen stereo?" and so, i simply added a mixer circuit at input using 1K resistor (yes its simple and cheap method to do so, however there are also several other ways). Now you can listen to the good to both channels of stereo audio but not like stereo effect. Shorting the left and right channel is not suitable and recommended method. Just use this method which can be called a passive audio mixer in order to mix both of the channel of incoming audio. However you won't be having a stereo output as there is just a one speaker and just one input at IC lm386 pin 3 (But you can use two amp-circuits for that). But i think that it is just fine if you're about to listen to the audio just for fun. So, in the above given schematic you can still add a stereo potentiometer if you want. A value of 10K would be fine will provide you good range of setting the input gain.
I saw many people use a 10uF capacitor between gain pins 1 and 8 of IC386, i don't recommend that because i experimented on it resulted in blown chips and one time it caught fire on the breadboard which caused my beautiful and expensive breadboard look horrible. The amp chip was draining alot of current than expected in order to increase the gain however i didn't have a low current power supply so it got blown. Anyways;
Circuit on vero-board can be more compact as follow:
Step 1: Assembling Amplifier on Vero Board
Keep the wires that you use to create connection between IC pins and other components as shortest possible. This would prevent unwanted noise from surroundings or any electric device near it. Or maybe it caught the radio frequency sometime.
8 pin DIP socket
Capacitor 100nF ceremic Capacitor (Code for which is 104)
2pcs 100uF - 16v
2pcs 1K resistors 0.25W
To build a good amplifier never salvage capacitors. Use new one with accurate values mentioned. In order to make it sound clean forever use a metal project enclosure box and never forget to connect the amplifier circuit's ground wire to it. Good Luck.! And Have a wonderful project. (Y)
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