Audio Amplifier Circuit problem

[Brando83]

Hi, in my first post- need help or advice for designing audio amplifier circuit.

I have to design an audio amplifier circuit. We are told the impedance of the headphones and the minimum voltage they require and also the voltage source. After researching I have found that the LM386N-4 is a popular choice. (According to a datasheet of LM386N-4 - http://www.icrfq.com/part/2377557-LM386N_4.html ). I've seen many circuit diagrams but what I don't understand is how to pick the voltage gain needed for the amplifier.

I originally thought that need to know the input audio signal voltage and when I multiplied that by the gain that would need to give the minimum voltage required by the headphones, but it appears that what matters is the current which I don't get.

And are you able to design such a circuit without knowing about the audio input signal? If you do need to know about it what is it you need to know about it and why?

I would greatly appreciate any help as I am very lost.
Thanks in advance and sorry for my bad English.

[NickS]

It really depends what your input is going to be
http://www.ovnilab.com/articles/linelevel.shtml
http://www.sengpielaudio.com/calculator-gainloss.htm
Have you calculated what your output voltage swing needs to be to drive the headphones?

[Brando83]

Hello Nicks,

Thanks a lot, for your reply and sharing a valuable information to me. It might be helpful for me. I had bookmarked this information for my future.
No, I didn't calculate the output voltage but as my research maybe it would be 9V. Let you know my update very soon.

Kind Regards