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.
Step 2: How to Wire the Barbie Box
I have included a wiring diagram of how to properly connect this pile of parts. What I suggest doing is temporarily connecting all the parts together by twisting or taping for trouble shooting. One important thing to check is to make sure all of the left, right, and return signals are not crossed. When I was doing this I used a song with a distinct left and right side, in my case people talking who were panned either entirely left or right. When you split and strip the 1/8th inch headphone cord, you will find either three or four wires. Red is right, left will be white or black, and the remaining, usually uninsulated wire, is the signal return. This signal return will either be one or two wires, but in the end they connect to the same point. After you have all the wiring working, you can trim the wires to length and solder all the connections. I recommend using shrink tubing to both organize wires and cover any exposed portions of the wire. Just remember to put the tubing over the wire BEFORE SOLDERING.
Step 3: Fitting Inside the Case
After you have all of the wiring figured out, the next step is to fit it all into your case. You will be drilling a large hole for the headphone jack, many small holes to act as the speaker grills, and cutting a slot for the switch. Try and arrange the parts as level as possible, so that when the case is closed, there is no place where there is excessive pressure. If any of the components, such as the switch or the speakers, have screw mounts, I suggest using them. Other parts and be glued into place, but be sure to use a powerful glue, and at the same time do not let any get on the cone of a speaker.
Step 4: Final Touches
After you have installed all of the components into the case, the final step is to add padding. I chose to use pink soft packing foam, both on the inside cover and below the mp3 player. Once this is in place you can give your new case a test run. Hook up your headphones and give a listen, then flip it over to boom box mode. I found that with my case, it works best to turn the volume up high or all the way on boom box. Also, because the speakers draw more than headphones, I find that my battery life is only 4-5 hours as a boom box on full charge, but I still find this more convenient than separately powered speakers. As an added bonus, if you used plastic for your case, you can get the creepy possessed Barbie effect when the back light is on and you close the case in the dark. You now have a sturdy case for you mp3 player that can blast music into your retro headphones, out built in speakers, and does it all while looking like an old tape player.