Electronics HOW TO

How to make an audio amp?

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An audio power amplifier device amplifies the signals received by low power electronics, for example a CB radio. Moreover, it used by professional musicians to amplify the sound of guitars. Any device that works towards having or transmitting voice audio signals always has an audio amplifier fit inside them. They are fit into voice recognition systems as well. It also makes those frequencies hearable that a normal ear cannot hear, basically the ones that are below 20 hertz. The only problem is that an audio amplifier is very expensive and might not come under your budget. Not many people know this, but you can make an audio amplifier inside your house with the required tools.

Tools required in making an audio amplifier:

These are some very basic tools that can be found in any local electronics store. They are not expensive and will require only a few bucks.

  • LM386 semiconductor
  • 10 ohm resistor
  • 100 and 220 micro farad capacitor
  • 5 kilo ohm and 100 ohm variable resistor
  • 0.01 and 0.047 capacitor
  • 9 voltage battery
  • 9 voltage battery clip
  • Extra wires
  • 3.5 mm stereo jack male and female
  • A doted board or a project board

What is LM386?

LM386 is a chip with low voltage that acts as an audio amplifier. It is best suited for battery powered devices, including all the amplifiers e.g. a guitar amplifier. It has an 8 dual in line package that can give output wattage of 0.25 to 1, solely depending on the model being used. There are three basic models of a LM386, namely:-

  1. LM389N-1.

It has minimum voltage of 4 volts and maximum voltage of 12 volts. The minimum output power is 250wm and the highest output power is 250mw.

  1. LM386N-3

It has minimum voltage of 4 volts and the maximum voltage of 12 volts. The minimum output power is 500mv and the maximum output power is 700mv.

  1. LM386N-4

It has minimum voltage of 5 volts and the maximum voltage of 18 volts. The minimum output power is 700mv and the maximum output power is 1000mv.

First of all take your LM386 (IC) chip and place it in the middle of the project board. If you carefully read what is written on the chip, you will realize that there are certain pin numbers starting from 1 and they increase as you move anticlockwise. Take the extra wire and connect the third pin with the fourth pin. After this take your 0.01 capacitor and join one of its pin with the INNPUT and join the other one with the second pin on the chip. The 5 k ohm resistor will have three pins A,B and C. the first pin of IC will be joined with pin A or the variable resistor, and then join pin A with pin C. connect the pin B and eighth pin of the chip. This will become the gain.

Now take the 100 micro farad capacitor and join its positive side with the sixth pin on the chip. The negative side should be joined with the fourth pin on the chip, also known as the GND. Then take the 10 ohm register and join its one side with fifth pin of the chip, and join the other side with the 0.047 capacitor. Then again join the second pin of the capacitor with the GND pin. After this join the positive

side of the 220micro farad with the fifth pin of the chip and the negative side will be joined with the point marked A in a 100 ohm resistor. Join the pin B of the variable resistor with the GND, and this will become the volume controller.

The next step is to join the positive pin of the 3.5mm stereo jack male with the third side of the 100 ohm resistor and the female jack will connected with the fourth pin of the chip (GND). Then join the negative side of the male jack with the 0.01 capacitor and then join the GND of male jack with the fourth pin of the chip. Lastly, you will be joining the 9 voltage battery. Connect the positive aide of the battery with the sixth pin on the chip and connect the negative side with the fourth pin of the chip. After you are done with making the audio amp, it is time to test it. Join the male jack with the mp3 players and the female jack with the speakers. The volume and gain can be adjusted according to your need. This will only work on one speaker and the tools can be changed for increased bass.

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