Friday, April 7, 2017

LM386 amplifier circuit schematic diagram complete 99.9% noise removal from ground loop

For those who are new to the LM386 IC may stumbled to a point facing all sort of noise related problem when using it to make an amplifier circuit just like me. It can be very challenging to avoid the sensitive noise and in fact the ground signal from our body contact also can cause significant distortion to the sound output of the circuit. You can try this just by putting your hand or touching one of the circuit component that is not grounded - the distortion noise is very obvious.

There are many videos on YouTube from some experience and experts showing how to avoid the ground loop noise from the Lm386 circuit by correctly connecting all the ground connection. Indeed this has very significant improvement that we should take note how to connect the ground to avoid noise.

However this solution is not enough to completely remove the ground noise - and when you put your ears close to the speaker you can still significant listen to the screeching / crackling noise in the output even if there is no sound to amplify. Indeed it is very annoying and frustrating for some at least to me. Especially earphone / headphone the noise is very obvious since it is placed right on the ears - the noise is not very pleasant to hear.

So after making some research i discovered the perfect solution to avoid the ground noise. And two of this component place at the input and the output would ultimately remove the noise. When there is no sound to amplify there is 100% clean no noise at all completely quiet. The two component are a mini transformer place at the input (step down mode) and a coupled inductor place at the output.

The circuit schematic is look like this. Now for the first time you can use the LM386 circuit to make a mini earphone / headphone amplifier without worrying about the distorted crackling and screeching noise. This is for real 100% working circuit as per prototype shown in the video!!

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