Appendix D Audio Card
Compaq Personal Computers
Original - February 1998
D-2
D.2 FUNCTIONAL DESCRIPTION
A block diagram of the audio card is shown in Figure D-2. The architecture is based on the
ES1869 audio controller, which provides the ADC, DAC, FM synthesis, 3D spatializer and
mixing functions. Output volume is affected by software. The software volume control uses 6-bit
resolution providing 64 levels. Card configuration is automatically provided by an on-board
Plug ‘n Play (PnP) EEPROM. Internal connections are provided for CD-ROM and system
speaker connections.
Four analog interfaces are provided to connect to external audio devices and are discussed in the
following paragraphs.
Line In
- This input uses a three-conductor (stereo) mini-jack for connecting left and right
channel line-level signals (20-K ohm impedance). A typical connection would be to a tuner’s
Line Out or Record Out jacks, or to a tape deck’s Line Out or Playback Output jacks. A less
optimum but acceptable connection would be to the headphone output of the tape deck or CD
player.
Line Out
- This output uses a three-conductor (stereo) mini-jack for connecting left and right
channel line-level signals (20-K ohm impedance). A typical connection would be to a tape
recorder’s Line In or Record In jacks or to an amplifier’s Line In jacks.
Mic In
- This input uses a three-conductor (stereo) mini-jack that is specifically designed for
connecting a condenser microphone with an impedance of 1-K ohms. This is the default
recording input after a system reset.
Headphone Out
- This output uses a three-conductor (stereo) mini-jack for connecting a pair of
stereo headphones with a minimum impedance of 16 ohms. This jack can also be used to connect
a pair of powered speakers (i.e., the type designed to be used with portable radio/cassette/CD
players). Using this connector defeats (mutes) the internal speaker and Line Out signals.
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