This is an electronic device that plugs into an iPod, iPad, or iPhone. It can be used to monitor and record a musical instrument at the same time. Imagine you are jamming on an electric guitar and you want to record it with some simple software on your iPhone. Now imagine you want to actually hear your own guitar while recording it. If there were an input and an output on the iPhone, then this would be no problem. However, they only put a single audio plug on the thing. This adapter makes it possible to listen to the signal on the way in.

  • prototyped initial designs using breadboard
  • created separate prototype in cable form factor
  • circuit board diagram using Cadsoft EAGLE
  • final design uses through-hole soldering on project board

The schematic and a circuit diagram, ready for etching, is below. Aside from some connectors (whatever works for you; I chose RCA) the only component needed is a resistor. Try something like 10k ohms and you should be good to go.

This article was originally written June 1, 2013.