Step 5: Give it a try
Point the laser beam at the photodiode, hit play on the iPod, and listen to any and all noises comming from the amp. Play with the iPod volume and potentiometer positions until music can be heard clearly and without distortion on the recieving side. Then turn up the reciever gain as nessisary.
Try mounting the laser on a tripod and sending music a longer distance. I recently was able to hear Starway to Heaven clearly at a beam distance of a half mile. This was done over a small lake, with an assistant in a canue with a pizza box to help with the aiming.