Apple Desktop Computer Sound Inputs, Sound Outputs, Built-in Microphone, External Sound Input

C H A P T E R 3

Devices and Ports

Sound Inputs

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

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

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

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

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

36Sound System