Stereo to Mono Audio Cable

I recently needed a cable where I can plug a stereo outputting device on one end and a mono output on the other so I looked online and for sure I was able to find one but I couldn’t wait for couple of weeks in order to get it. Instead I researched their construction and decided to make one.

The source for the components were this headphones that I got on one of my earlier airplane trips, where I got them for use during the flight and we were allowed to keep them. The interesting thing about the headphones is that their connector consists of two 3.5mm jacks, one mono and one stereo, where the mono jack can be folded so they can also be used on a regular device.

After opening the connector I removed the wires from both of them and grabbed two 1 kOhm resistors to be used as an audio mixer. The resistors are connected to both signal pads on the stereo jack and then they are connected together to give the output mono signal.

By hooking them through a resistor, we prevent shorting both of the input signals and we prevent damage to any of the equipment we connect them to.

For the cable in between I used the same cable that was on the headphones where I now used both of the signal wires inside as one, carrying the mono signal. One of the wires is attached to the midpoint of the resistors on the stereo side while the other side is connected directly to the signal pin on the mono connector. The other wire connects both of the shield pins on the connectors.

To protect the connections and to make the cable more durable, I’ve used this 5 minute epoxy repair moldable glue where I’ve first mixed a small batch and wrapped it around both of the connectors. This not only fixed the wires in place, but it also made some nice gripping points for handling the connection of the cable.

As you can see in the video above, the cable worked perfectly and provided a decent quality sound as well. Not bad for something that was basically free.

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