I wanted to use an external microphone with my iPhone, so I could record audio from an event. Unfortunately, there aren't any cables that give you a real microphone input jack. Fortunately, I was able to find an unexpected solution: the Mini A/V cable that came with my digital camera!
On one end, it has the three standard RCA plugs found on the front of every TV. On the other end, it's got a four-conductor mini plug that's the same as the iPhone's headphone jack. Just plug the cable into the iPhone's headphone jack, and use the RCA jacks like this:
- White/Black: Audio out (L)
- Yellow: Audio Out (R)
- Red: Mic level input
Now, with the right adapters, you can use professional microphones with your iPhone, or feed it audio from a PC or mixing board! Just remember to add a line level attenuator before you do that, because line level will be
waaaay too loud. This comes in very handy with audio recording apps.
Unfortunately, the input is only mono, but it sure beats the internal mic.