CHAPTER 3
Devices and Ports
36 Sound System
Sound Inputs 3
The sound system accepts inputs from three possible sources:
■ built-in microphone
■ external stereo sound input jack
■ sound from internal CD player
Built-in Microphone 3
The sound signal from the built-in microphone goes through a dedicated
preamplifier that raises its signal level to the nominal level of the codec circuits
in the Burgundy IC.
External Sound Input 3
The external sound input jack is a 3.5-mm mini phone jack located in the I/O
bay on the right side of the computer. The sound input jack accepts line-level
stereo signals or an Apple PlainTalk microphone. It also accepts a stereo
miniplug-to-RCA cable adapter for connecting stereo equipment to the
computer.
The sound input jack has the following electrical characteristics:
■ input impedance: nominal 3300 ohms
■ maximum level: nominal 1 V rms (2.8 V peak-to-peak)
Sound Outputs 3
The sound system sends computer-generated sounds to the built-in speakers,
the sound output jack, and the headphone jacks. The sound system provides
user-selectable SRS
®
3D stereo enhancement.
Internal Speakers 3
The computer has two internal speakers. The computer turns off the sound
signals to the internal speakers under the following conditions:
■ when headphones are plugged into either headphone jack
■ when a plug is inserted into the sound output jack
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