Connect How To: Stereo Adapter, 1/4″ or 1/8″ Plug to two RCA plugs
This adapter works well with connecting a headphone output with a line input or recording input. There are even some stereo speakers that have RCA type input jacks.
As you can see, I have illustrated the right wire as being red and the left wire as being white. The wires aren’t typically those colors, but the casings usually are, and those colors are standard on all the stereo equipment that I’ve ever seen.
Although this diagram illustrates how to wire a 1/4″ stereo plug, it’s the same diagram for a 1/8″ (3.5mm), only smaller.