I have to design a headphone 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 LM386 is a popular choice. 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 you would need to know the input audio signal voltage and when you 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
hyuna.

Well, you lost me way before your original problem despite having 2 courses in university on electrical and computer engineering, but I can barely remember anything from it.
You might be better off in a forum related to electrical or computer engineering for help with stuff like that.
I doubt you'll find any broadcasters here who would take the route and design a headphone amplifier from scratch themselves rather than taking one off the shelf.

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The two parts of the circuit are the same. Two inputs, controlled by 47K input, this should be a DC path from a double logarithmic potential to ground. The balance control is a single 47K linear potentiometer, adjusted in the center to prevent even the attenuation of the left and right input signals. If the balance control is moved to the left, the input track on the left has less resistance than the right track, the left channel is reduced more than the right, and vice versa.