In some audio situations it is necessary to convert a stereo source to mono. In the event that you have a stereo source and mono receiver, you may need to have an adaptor to connect the two. While such adaptors can be purchased cheaply, one can easily be constructed with a few simple steps.
Plug in the soldering iron and place it on a non-flammable surface, preferably a metal stand so the hot end will not touch the work surface. Cut the cable to your desired length and strip the ends to expose the wires. Strip about an inch off of the exposed wires on both sides. If the wire is shielded, twist the shield to make another connecting wire.
Place the soldering iron underneath wire and flux on top of the wire until the flux melts. Coat the end of the twisted wire with flux to keep it together. Do the same to the stripped wire to ensure a good connection. Unscrew the end of plugs to expose the connectors. The plugs may be male or female, depending on the need.
Slip the end of the stereo plug over the cable with the screw end facing the end you intend to attach the plug to. Place either wire into either connector. (Because you are converting stereo to mono, it is not important which wire goes where.) Place the soldering iron on wire and connector. Put flux next to, but not quite touching, the soldering iron on top of wire and hold it until it melts over wire onto the connector. Repeat this with the other wire and connector on the same side. Screw the end back onto plug, ensuring it does not touch the connections and they don‘t touch each other. If it does touch, simply wrap the connections in electrical tape.
Slip the end of the mono plug over the other end of cable with the screw end facing out. Twist both wires together and place them on the connector linked to the end of plug. It may be necessary to test which connector is right by plugging in the stereo end to a music source and mono end to a receiver with a speaker or headphones. Unplug the mono end and solder, in the same fashion as described previously, to whichever connector produced a sound in the tests. Screw the end back onto plug, using electrical tape if necessary.
Connect one end of the adaptor to an audio source and the other to a receiver. Turn the volume up to an audible level so you can hear the audio and make sure the adaptor cable works. If not functioning properly, take the ends back off and make sure connections are soldered correctly and not touching each other or the cover.