A 3.5mm stereo jack is a multifunctional jack used to connect stereo headsets to items such as iPods, MP3 players and cell phones. It may also be used to connect speaker systems to computers and laptops.
The pin of a 3.5mm stereo jack has three separate insulated sections: ground, left audio and right audio. Its small size makes wiring a 3.5mm stereo jack more intricate than larger jacks; however, providing you have the correct tools and a steady hand, the task can be completed fairly quickly.
Buy a 3.5mm stereo jack. Choose a jack with an outer cover you can unscrew and has small screws inside to attach the wires. The size of the jack makes soldering difficult as it's easy to get solder in the wrong places.
Strip about half an inch of protective plastic from your stereo cable. Use a small sharp knife and gently cut around the protective plastic, making sure you don't cut into the internal wires. If you do, cut the cable cleanly and start over.
Check the four wires to ensure you have not cut into them. Two are exposed, and the other two are covered in coloured plastic. The colours are usually red and black.
Twist the two exposed wires together leaving you with three. Carefully strip about a quarter-inch of plastic from the two coloured wires.
Unscrew the cover from your 3.5mm stereo jack. Thread the wires through the 3.5mm stereo jack, ensuring the threaded end faces toward the end of the wire. The main part of the jack has three very small screws. The top screw is the "ground"; the other two are for the left and right audio connections.
Unscrew each screw slightly using a small electrical Phillips head screwdriver. Loosen just enough to be able to insert the wires between the screw and the fixing. Don't unscrew too far because if the screw falls out, you will have difficulty finding it.
Attach the completely exposed wires that you previously twisted together under the top screw head, then tighten the screw. Check to ensure a tight fit.
Repeat the process for the two remaining coloured wires. It does not matter which colour you attach to each screw, though sometimes there may be a small "+" or "-" on the screw. If this is the case, attach the red wire to the screw marked "+" and the other to the screw marked "-".
Screw the cover onto the body of the jack and plug your 3.5mm stereo jack into your music player.