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Audio amplifier circuit

  1. Nov 27, 2011 #1
    hi all,

    i want to design the following circuit. The circuit should listen to the audio and amplify the audio. could somebody provide me the circuit or help to design the circuit like which components shall i take for the audio input, the speakers what i have to select and additional things.

    thanks in advance,

  2. jcsd
  3. Nov 27, 2011 #2
    What do you mean by "Listen"!!!?
  4. Nov 27, 2011 #3


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    You could have a look at this site to see how it is usually done.


    Where integrated circuits have been used, you would have to check what is usually stocked by your local supplier of electronic parts. Some ICs will be difficult to find, even on Internet.

    For a low powered amplifier, the LM386 integrated circuit is usually easy to find and does a good job.
    Here is a circuit using one:
    You may not need the LM741 preamp.

    Here is another LM386 circuit:

    That circuit came from this page which has several other amplifiers:
    Last edited: Nov 27, 2011
  5. Nov 27, 2011 #4

    Listen i mean to say a microphone as the input and the connecting circuit which would amplify this small signal to a large volume signal. i think i am mixing a lot of terms. finally the summary of my project is like what ever you speak (audio signal) should be taken by a microphone and amplify it many times so that it can be audible to some distance say in another room or like that. i hope you understood.

    thanks and regards,
    Last edited by a moderator: Nov 28, 2011
  6. Nov 27, 2011 #5
    Hi vk6kro,

    thank you very much for the reply, the circuits are really helpful. Now my only doubt is in the circuit diagram i think the terminal you have shown a circle with a black dot is the input terminal where i need to connect a microphone. if possible can you suggest what type of microphones i can use? iam very much new to audio amplifiers. This clarification would enable me to build the circuit practically and see the output.

    thanks in advance,

    Last edited by a moderator: Nov 28, 2011
  7. Nov 28, 2011 #6
    Are you going to build the circuit?

    You can use any mic that you can get easily. The 356 is gain adjustable. The only thing I am concern is the 10K volume control right at the input. I would use a 50K minimum to avoid loading down the mic.
  8. Nov 28, 2011 #7


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    Science Advisor

    There is only one type of microphone available now. It is called an electret microphone.

    These are quite good, but they need a power supply. You just take power from the amplifier +ve voltage via a 4.7K resistor.
    The metal case of the microphone is grounded and the 4.7K resistor goes to the other wire of the microphone.
    You take the output at this junction.

    The LM386 shown in the diagram above is set for maximum gain of about 200. You can get less by putting a resistor in series with the capacitor between pins 1 and 8.

    Even at full gain, the microphone probably won't drive the amplifier to full output, but it will be quite loud enough.
  9. Nov 28, 2011 #8
    Yeah iam planning to build the circuit. i am not sure if i will be successful, but i will give it a try.

    thanks and regards,
  10. Jul 7, 2012 #9
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