In this Instructable I will walk you through how to design and create a perfectly usable aux cable for any mp3 device, which in my case ill be installing into my car. If you are looking to install an aux cable into your car, FIRST pull your radio out and make sure there is an "aux Input" in the back of you radio. in many cases you will need RCA jacks to a 3.5 mm headphone jack. some newer cars may have a female headphone input and you will need 2 male headphone ports soldered together. I will explain how to do both of these fairly simple solder jobs.
Step 1: Materials List
1) Two cables with your desired size headphone jack or RCA cable
2) Wire Strippers
3a) soldering iron (solder obviously)
3b) Wire nuts if you are not experienced with a soldering iron.
Step 2: Stripping All of the Wires
Snip off as little wire as possible to accommodate errors, strip all of the wires and separate them individually, you want about an 8th inch of exposed wire. to make soldering or wire nutting the wires together, you should twist the bare wire between your pointer finger and your thumb.
Step 3: Identifying Different Wires
1) Salvaged headphone, there will be two smaller wires within a larger wire. the two small wires are your left and right wires the larger wire is you ground. the ground wire is what makes your sound come out clearly and crisp.
2) RCA, when you cut open the RCA there will the a smaller wire inside a larger wire. the smaller wire is the sound wire depending the if it was the R,C,or A. the larger wire is you ground, which is responsible for how clear your music will play.
Step 4: Setting Up to Solder
You want to try to keep the left and the rights separate and all the grounds must be connected. to properly solder and to ensure a good connection, twist the wires together with your thumb and pointer finger.
Step 5: Soldering
apply a small amount of solder the exposed sections of wires, don't forget about the ground wires.
Step 6: Cleanup and Test
now wrap the soldered wires with electrical tape (AFTER THEY'RE GIVEN TIME TO COOL.) plug in the cable and start playing your favorite songs