The microJammer is a small, amplified iPod speaker. since it uses the iPod's battery for power, the speaker's size is very, very small; less than an inch in any direction. It uses a common 2 transistor amplifier circuit, and uses the headphone jack as the signal input. It is by no means a micro sized boom box, but the volume is comparable to an iPod touch's internal speaker, with the sound being a little more bassy and clearer. Seeing as it relies on the ipod's internal battery, the iPod's battery life is cut down drasticly, so this is not intended to be used all day. But for sharing music with others on the go, this cant be beat!
Step 1: Parts and Pieces
NPN Transistor- 2N3904 or BC548
PNP Transistor- 2N3906 or BC327
10 uF capacitor
4.7k ohm resistor
1M ohm resistor
As for the driver, the smaller the better- to a point. You dont want to use a driver from earbuds, or a super cheap driver. Drivers from over-ear headphones are great, as well as speakers form portable DVD players. I got mine from one of those. They are Panasonic brand and actually have very good sound. A good way to tell what kind of driver would be best is by what it was from- if you find a driver used by something that plays audio, it would probably be a safe bet for this application.
Other parts that are needed include:
1/8 inch headphone plug (from old headphones)
A word about the ipod connector- I recommend vandalising a USB cable for the connector, but DO NOT use a new cable. The new one has contacts in the connector only for the USB functions- USB power +/-, and signal +/-. The older connectors have all of the contacts in the connector in place, including the one we need to power the speaker.
And as for the enclosure- Anything small will work. I was originally going to use an altoids tin, but it was too big. (what does that say about the size of this thing?) So next I tried a Tic-Tac container, which as difficult to cut a hole for the speaker, so it was scrapped. I then came across the top part from an old flashlight, which was the exzct diameter of the driver I was using, so i chose that. If you end up using something mad of metal like I did (in my case anodized aluminum) make sure that the amp does not accidentally short circuit against the side of the enclosure.