iPhone stereo audio recording

Q: I was thrilled to read in your recent wrap-up of iPhone OS 3.0 features that “certain stereo recording accessories can be attached” to trigger stereo recording mode in the iPhone and iPod touch with the 3.0 OS. I am a musician and for years I have been recording rehearsals onto a fairly archaic digital minidisc player with a decent, powered Sony stereo microphone. Based on your article, I thought I would try attaching my microphone to my iPhone via the 1/8” miniplug and using Voice Memo for recordings. Unfortunately the microphone wasn’t even recognized by the Voice Memo app. The iPhone instead stubbornly used its built-in mic.

Is there a particular type of microphone that connects not via the headset/speaker/microphone miniplug, but via the plug on the bottom of the phone? If not, may I ask what equipment you used that worked as you described?

– Eric

A: The headphone port on the iPhone and second-generation iPod touch is specifically wired for a headset-based microphone, and will not accept other types of audio input. Essentially, it is a three-connector plug, with the first two connections used for the left and right audio channels and the third connection used for a monaural audio input, such as from the microphone on the earphones included with the iPod touch or iPhone itself.

To enable stereo recording on the iPhone and iPod touch in iPhone OS 3.0, you must use an external audio recording accessory that connects to the Dock Connector on the bottom of the device. These accessories have been available for some time for use with traditional click wheel iPod models, beginning with the fifth-generation iPod. Until iPhone OS 3.0, however, none of these devices were supported for audio recording on the iPhone or iPod touch, as these did not include a built-in recording application.

With the release of iPhone OS 3.0 and the included Voice Memo application, most of these accessories are now supported, although there still appear to be some inconsistencies as to which ones work and how well these work. These problems are likely related to bugs in OS 3.0 that will hopefully be remedied in a future update. However, even older devices which were made for the original fifth-generation iPod, such as the Belkin TuneTalk Stereo, seem to work more or less as expected with the iPhone and iPod touch. You can find a list of iPod audio recording accessories in our Audio Recorder Reviews.

One last important point of note: Even in stereo mode, the audio recordings made by the built-in Voice Memo app are encoded as 128kbps AAC files.