Specifications
CHAPTER 3
I/O Features
Sound 31
records sound from several sources: a microphone connected to the sound input jack, the
video input module, or a compact disc in the CD-ROM player. With each sound input
source, sound playthrough can be enabled or disabled.
Sound Output 3
The Macintosh Performa 6400 computer has one built-in speaker/subwoofer and two
sound output jacks, one on the front and one on the back. Both output jacks are
connected to the sound amplifier; the jack on the front is intended for ease of access
when connected to a pair of headphones. Inserting a plug into either jack disconnects the
internal speakers. The rear jack is intended for use with external speakers, and it is
muted when headphones are plugged into the front jack. (Options in the Monitors and
Sound control panel can be used to determine the interaction between the sound input
and output devices.)
Sound output is controlled by the O’Hare IC. The AWACS IC provides the stereo sound
output to both the internal speakers and the sound output jacks.
Sound Input 3
The Macintosh Performa 6400 computer has a stereo sound input jack on the back for
connecting an external microphone or other sound source. The sound input jack accepts
a standard 1/8-inch stereophonic phone plug (two signals plus ground).
The sound input jack accepts either the Apple PlainTalk line-level microphone or a pair
of line-level signals.
Note
The Apple PlainTalk microphone requires power from the main
computer, which it obtains by way of an extra-long, 4-conductor plug
that makes contact with a 5-volt pin inside the sound input jack. ◆
IMPORTANT
The microphone for the Macintosh LC and LC II does not work with the
Macintosh Performa 6400 computer; it requires the line-level signal
provided by the Apple PlainTalk microphone. ▲
Sound from an external source, such as a TV, VCR, or VTR, can also be input through the
right and left channel sound input jacks on the optional video-in module.
Sound Input Specifications 3
The sound input jack has the following electrical characteristics:
■ input impedance: 15k ohms
■ maximum input level: 1.06 V RMS