Solder Stereo Mini Plugs

There are plenty of reasons why you might want a custom length or custom-connected cable with one of these plugs on it (or sockets, for that matter - an "inline socket").When you look at the round part, a stereo plug is divided into three sections. The largest section is "common," and the other two sections are left and right (the tip is left).On the back of the plug, there are three connectors. The two stubby ones go to the left and right, and the long one (often with a cable crimp built in - a sleeve) is common.

Steps

  1. Strip the two insulated wires and twist the shielding into a third "wire." The two insulated wires are for left and right. The third, twisted one (made from the shield) is for common. Note, you will need some insulation on the left and right wires. If you strip them for their full length, they are likely to touch each other and the common wire, causing a short circuit. 2 or 3 mm of stripped wire will be plenty.
  2. Slip the case over the wire.
  3. Tin the wire with solder (heat it up and coat it). If you aren't familiar with soldering procedures, look for an online guide.
  4. Slightly scratch the connectors on the back of the plug so that the solder will go on easier This way, they are super clean, and the solder will flow on nicely. Also tin these, but only where you plan to connect the cable.
  5. Join the common, then join the left and right. Note which conductor on the jack is connected to the tip and ensure the left channel wire is attached to this one. If the wires are color coded red and white, the left would be the white wire.
  6. Put some tape around each connection to insulate them. Only use a tiny bit, or the cover won't go on.
  7. Screw it all together. You did slip the case over the wire first, didn't you?
  8. Test the finished product to ensure that each of the three sections on the front of the plug have not somehow become connected to another section by a short circuit. All three sections should not be connected to any other section - even if you wobble the back of the plug around (as will happen during use). Check that the wires are connected properly. A multimeter with a buzzer is ideal for this, or you can use a homemade one with a light.



Tips

  • The left channel is usually the tip of the jack. The right channel is usually the next segment down on the jack.
  • To add strain relief mix up 2-minute epoxy and drizzle around the interior of the jack wires. Rotate it and coat the various parts and then screw the jacket or cover into place. If the epoxy is very thin it might leak out so set the plug to dry with the tip facing down. This will prevent you being able to reuse or repair the plug so be sure it works before you do this but it's a great way to add some custom strain relief.
  • You might expect four wires to be needed for stereo (+ and - left and right), but for low power applications, you can join the negative wires together (making them "common"). Some cars are wired this way (all the negatives are connected to the body of the car), and if you install a higher power CD player or a similar device, you have to rewire all the speakers with new two core (figure 8) cable.
  • You can test your connections using an ohmmeter and measuring resistance. If you get a reading while touching the left or right and ground (the lowest portion of the plug) then you have a problem.
  • To make it strong, you should use the crimp bit to clamp over the full outer area of the cable (not too firmly, or it will break the insulation inside the cable). Make sure that the twisted shielding is soldered on short, so it pulls first (because it is usually quite strong) and leave it at that. The left and right wires are quite fragile.
  • The reason we need shielded cable for headphone plugs is that interference is a bigger problem with the low power the cable will transmit.
  • To strip the outer insulation off the cable bend it at the point you wish to strip by 135 degrees or more then touch a sharp blade on the wire where it is stretched (the outside of the bend) but don't push hard enough to cut through to the copper. The insulation should (kind of) tear away and cut should (again kind of) run a bit to either side. Work your way around then firmly pull the insulation off the end - any fine sections of outer insulation will break off.
  • Drill a hole in a piece of wood, and stick the plug into it as a holder while you solder.
    • Plan all of the wire lengths inside the plug carefully, so that it all lays flat. Otherwise, you won't be able to screw the case on.

Warnings

  • Do not use the plug if you even think it has a short circuit. It could kill expensive equipment. If you use the plug and it does not work, remove it instantly.
  • Apply heat sparingly (use good technique). An overheated plug can melt and short circuit.
  • You can also cause a total short circuit by overheating the braiding/shielding. It will melt everything inside the cable and cause a short circuit there.

Things You'll Need

  • Cable with two insulated cores plus a metal shielding braid around them both (order "two core shielded" as a general rule, but check).
  • Plug.
  • Sandpaper or file.
  • Solder and iron.

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