A friend of mine loves to sing. I saw a weekend project on Makezine a while back that I thought would be fitting for her.
Songs are typically mixed with a center, right, and left track. This device allows you to force the left and right channels to use each other as ground, thus canceling the center track via destructive interference. By flipping the switch, you can either enable or disable this behavior, letting my friend enable or disable a song’s vocals easily.
Built at Boilermake 2015 with a little bit of janky 3-way soldering plus a careful handheld dremel job to drill holes.