What is a stereo patch cable, you may be wondering? A stereo patch cable is for connecting two audio devices, to pass the signal from one device to the other. It can be used, for instance, to connect your mp3 player to your car's audio system, if your car comes equipped with a 3.5mm audio input jack. A patch cable can also be used to connect a digital audio player to a pocket headphone amplifier, to boost the signal output (which is what I made this one for). It could also be used to play audio from your phone through speakers or a stereo equipped with a 3.5mm stereo input jack.
Stereo patch cables can be purchased relatively inexpensively online, or sometimes at your local dollar store, but not with such a classic design, or at custom lengths. Plus it's a lot more fun to make it yourself!;-)
I purchased six stereo plugs online for less than $US5, a shoelace for $1, and I found the USB cable on the street. (People often throw away their old printers, and dispose of a perfectly good USB cable with it;-) With these materials, I made two patch cables; one about 6 inches and the other about 2 feet, for about $6 bucks, and I have two plugs leftover. Below you will see pictures from both cables, as the process is the same.
• USB cable (any type will do)
• Stereo 3.5mm plugs
• Heatshrink tubing (optional)
• Wire cutter
• Soldering iron and solder
• Hot glue gun
Step 1: Cut USB Plugs and Lace Cable
First cut off the plugs, from the USB cable. Then cut the tips off your shoelace. Depending on your shoelace, there may be a an internal lace that needs to be pulled out. And depending on the size of your cable and your lace, it may be helpful to put a small piece of heatshrink tubing over the tip of you cable, to make it easier to pass through the lace. (If you don't have heatshrink tubing, you can try a piece of tape, twisted tightly on the tip).
After you've passed the cable through the shoelace, you might want to heat the ends of the shoelace a bit with a lighter, to prevent fraying. Now strip back about an inch of the plastic shielding from the USB cable. then strip a shielding off each of the internal wires. (You can use a lighter to delicately burn off the shielding, by my experience is that using your teeth actually works best).
Once you've stripped the four wires, choose two to combine. It doesn't matter which wires, as long as you connect the same two at both ends. Twist the two wires together tightly, to effectively create a total of three wires. Later we'll connect the three wires to the left, right and ground terminals on the stereo plug.
Step 2: Tin Wire Tips
This will make it a lot easier to connect your cable to your plug, and also greatly reduce the chances of the wires touching inside the plug, and creating a short.
Step 3: Thread the Plug Parts
The plugs I used have three parts per plug that need to be laced onto the cable before attaching the plug. It's helpful to thread all these parts at the same time, before you attach plugs at either end. Thread them in the following order; plastic sheaf, spring, barrel, (and then the reverse order), barrel, spring, plastic sheaf. (See photo).
Step 4: Attach Plug
I found the following demonstration on YouTube very useful: DIY Mike iPod MP3 3.5 mini plug cable for aux input music
One important thing to keep in mind is that if any of the wires touch each other, or another terminal, you will have a short in your cable, and it won't work properly.
After you have the plug attached, now is a good time to test your cable.
Step 5: Hot Glue Wiring
Clean-up any excess glue, or stray threads of glue, and slide the plastic shield down over the shoe lace, and freshly glued wires. If it doesn't fit all the way, don't worry.
Almost finished... Now slide down the other parts of the plug - the spring and the barrel - and screw the plug into the barrel. Be careful not to loosen your connections in the process. If possible, try to rotate the barrel, and not the plug.
Step 6: Finished Product