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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.

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  • \$\begingroup\$ A quick search for something like "audio amplifier circuit" will give you tons of circuits and explanations. Because that's basically what you want, to amplify an audio signal. Whether that's in a (broken or not) docking station or not doesn't really matter. \$\endgroup\$ – user17592 Aug 3 '14 at 20:46
  • \$\begingroup\$ That seems obvious to me now but didn't at the time. Thanks very much! \$\endgroup\$ – cainy393 Aug 7 '14 at 23:29
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The LM386 is worth a little try: -

enter image description here

The above is a mono channel so you'll need to duplicate it for stereo. Note that the 0.05uF capacitor can be a 0.047uF (or 47nF) cap. The 10k pot will control volume and it needs to be a logarithmic type to get a realistic adjustment range. You can use a linear pot but you'll find that all the adjustment of volume is in the last quarter of the pot rotation.

I'm not sure what power supply you plan to use but running this amp from 9V (Vs) is typical and you'll get about 0.5 watts per channel into an 8 ohm speaker.

If you want something a bit more challenging there is this: -

enter image description here

And if you want more power there is this: -

enter image description here

Note that the TDA2030 can be used on its own to get 5watts to 10watts - look up the data sheet and give it a read.

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  • \$\begingroup\$ Thanks this is really helpful. In terms of power supply I was thinking of using mains actually, I was just gonna find an adapter laying around that seemed about right since I plan on charging the phone too at some point. The speakers I have are 1.5 Watt so the second one actually looks ideal but the first one looks a bit more friendly haha. \$\endgroup\$ – cainy393 Aug 3 '14 at 20:50

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