So I have an old iPhone speaker dock that broke after I plugged in the wrong cable and fried the microchips on the circuit board. From it however I salvaged the dock connector itself and a couple speakers. I've wired these together on a proto-board to get the iPhone to recognize that it is docked and play music out of the two speakers. Obviously however the iPhone only outputs audio at a level to play through headphones so it is very quiet. I would like to build a small circuit to amplify this sound with an external power source and I may also get it to charge the phone too eventually. I don't have any idea about handling analogue audio though. I have used OP Amps before in basic projects at school to amplify an LDR but that's all. Could someone please point me in the right direction in terms of which IC to use for this project and how to connect it up?
Presumably all the circuitry that came with the docking station did all this but its fried and looks way over-complicated for what I want to do. Also it would be nice to use a variable resistor to change the volume too at some point.
Thanks in advance.