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Instructables user richfiddler11 writes:

My car stereo has only one ‘Aux’ input, but I have several gadgets that I like to hear on a trip without swapping cables: MP3 Player, talking GPS, Blackberry, XM player, Kindle, etc.

I couldn’t find a commercial solution, so I came up with this little passive audio mixer that takes 1/8″ headphone outputs from up to four devices and safely mixes the signals into one line that can feed a car stereo Aux input, powered speaker or any other amplifier that can take 1/8″ stereo output.

Becky Stern

Becky Stern is head of wearable electronics at Adafruit Industries. Her personal site:



  1. John Park says:

    This brings back memories of when I was a kid my best friend’s dad built one of these in a Band-Aid box (the original cheap project case, grandfather to the mint tin!). It was actually a 1/4″ headphone splitter and had awesome Dymo labeling on it.

  2. mhenstell says:

    There’s no such thing as 1/8″! It’s 3.5mm!