Audio Routes

Available Input Routes

1. The built-in microphone of the original iPhone appears to be routed through a speech-processing codec, which limits the sample rate to 8 kHz and significantly degrades the frequency response.
2. Using a dock connector input with the original (1st generation) iPod touch appears to require that something be plugged into the headphone jack, unless the dock connector device also supports audio output (like the Macally iVoice Pro, which, ironically, is one of the few devices that is narrow enough to allow you to plug your headphones into the bottom of the iPod).

Available Output Routes

1. Even when using the dock connector for input, if the receiver or built-in speaker is the current output device on the original iPhone, the sample rate will be limited to 8 kHz (for input and output).

The effects of switching on Prefer Speaker Output, in the I/O Device Options screen, are described below:

• iPod touch (1G)
  The original iPod touch has no built-in speaker, so this option has no effect.
• iPhone (original)
  On the original iPhone, if this option is switched on, the built-in speaker will be used for audio output, even if headphones are connected. However, if a headset (with a mic) is connected to the headset jack, it will override the speaker output preference (audio output will go to the headphones of the headset).
• iPhone 3G and iPod touch (2G)
  On these newer devices, switching this option on will cause the built-in speaker to be used for audio output, regardless of what other audio connectors or accessories are attached to the device.