This is a simple (maybe) instructable on how to make an audio amplifier using a LM386 audio amplifier chip. The cup helps with the sound ;p.

Just found this. Check it out, looks decent

Step 1: The Parts

I'll say this right now: Special thanks to josepino.com. This website has the greatest instructions and the easiest-to-read circuit diagrams

You will need:

-100k Potentiometer
-.1 micro farad capacitor
-220 micro farad capacitor
-10 micro farad capacitor --only necessary for the 200k boost loop
-LM386 microchip (or whatever it's called)
-Solder
-Soldering Iron
-small circuit board
-headphone jack
-speaker --http://www.josepino.com/circuits/index.php?howto-speaker.jpc--make your own

Optional
-plastic cup

Note: I added a breadboard that I drew up from the circuit diagram, so if someone wanted to double-check it that would be nice

Step 2: Liberating the Audio Jack

Cut the wire a couple inches away from the jack (you want a little room to play with it. I didn't do that)
Strip the wire
Strip the insulated wires, making sure that you don't strip them so far that the stripped part touches the non-insulated wire
EDIT: Don't twist the two (formerly) insulated wires together, it might hurt sound quality.
Those (formerly) insulated wires are the positive and the noninsulated are the ground.

Check out my instructable on headphone repair for more about headphone wires.

Step 3: Place Everything on the Board

Put everything on the board. This step helps you use the smallest amount of circuit board possible, which results in a smaller amplifier.
Here's how I set up mine

Step 4: Make All the Connections Underneath

Just follow the circuit diagram. Make sure you read all the comments on the pictures in this step--it'll help a lot.

Step 5: Double-Check All Connections and Finish

Double-Check all connections for short circuits and bad connections. Then, once everything is in place, test it out. To improve the sound a bit, cut the bottom out of a plastic cup and place it over the speaker.