This is a padded protective carrying case for your mp3 player that also converts the headphone jack to quarter inch, can act as a boom box at the flip of a switch, and disguises your mp3 player as an early nineties tape player or similar low theft item.
The original motivation behind this project was to make a convenient converter to a quarter inch headphone jack so that I could hook up my thirty year old David Clark aviator headphones. I also wanted a protective case, both to keep my mp3 player from getting hurt, and to hide the fact that it was an mp3 player. I found the plastic Barbie case at a thrift store for less than a dollar. Its size inspired my that I could also build in speakers, making it double as a small boom box. This is not a very difficult project, the only necessary skills are soldering and drilling/cutting the case. Most of the parts I used I scavenged from other items, old electronics, or picked up at the store for only a couple of dollars.
Step 1: Gathering proper supplies
Most of the materials that you will need to make this are fairly easy to find, or inexpensive to purchase. First off you will need an mp3 player or other music source (you could use this same set up for a CD or tape player, or even a laptop). You then need to find and choose a case. I suggest just searching your house, the thrift store, the neighbors trash, anywhere. Plastic is easy to work with, but any material that you are able to drill through will work. Next is an 1/8th inch stereo plug and cord, like the end of normal pair of headphones. I recommend a plug with a 90 degree bend, because it will fit inside the case better, and puts less stress on the plug and cord. I just cut mine from an old cheap pair of headphones, and you could even butcher those iconic white earbuds. Speakers can be taken from anywhere, or bought if you can not find suitable ones. Mine are from the insides of laptops and desktops. I like the computer speakers because they do not need much power to run. The switch is the next important piece, and you will probable need to buy this. You will need a DPDT switch, which stands for double pin, double throw. This means that the switch has two positions, and that each of these positions makes two connections. For our purposes, that means that the stereo left and right signals come in the middle two pins, and either connect to the headphone jack or the speakers. I included in my Barbie Box a quarter inch panel mount jack, because my headphones have a quarter inch plug. If your headphones have the standard 1/8th inch plug, you can get an 1/8th inch panel mount jack. If your speakers are not magnetically shielded, you will need to put some sort of shielding between them and the mp3 player. IF YOU DO NOT IT CAN DAMAGE THE MP3 PLAYER'S HARD DRIVE AND PERMANENTLY RUIN IT. The speakers that I used were shielded, so I didn't need any shielding, but I have included a picture of shielding from a hard drive I was going to use if needed. A good way to test this is to see if ferrous metal (steel) sticks to the back of the speaker.