Audio Subsystem; Functional Analysis - HP Compaq d330 DT Technical Reference Manual

Chapter 5 Input/Output Interfaces
5.8

AUDIO SUBSYSTEM

The systems covered in this guide come configured with one of two types of audio support:
♦
Desktop/configurable minitower audio subsystem
♦
Small form factor audio subsystem

5.8.1 FUNCTIONAL ANALYSIS

A block diagram of the audio subsystem is shown in Figure 5-11. These systems use the AC'97
Audio Controller of the 82801 component to access and control an Analog Devices AD1981B
Audio Codec, which provides the analog-to-digital (ADC) and digital-to-analog (DAC)
conversions as well as mixing and equalizer functions. All control functions such as volume,
audio source selection, and sampling rate are controlled through software over the PCI bus
through the AC97 Audio Controller of the 82801 ICH component. Control data and digital audio
streams (record and playback) are transferred between the Audio Controller and the Audio Codec
over the AC97 Link Bus.
The codec mono analog output is applied to a mono 3-watt amplifier that drives the internal 8-
ohm speaker. Plugging headphones into the Headphone jack results in an active Spkr Mute signal
used by the codec to ,silence the internal speaker
The analog interfaces allowing connection to external audio devices include:
Mic In - This input uses a three-conductor (stereo) mini-jack that is specifically designed for
connection of a condenser microphone with an impedance of 10-K ohms. This is the default
recording input after a system reset. On systems with both a front and rear microphone jack either
jack is available for use (but not simultaneously).
Line In - This input uses a three-conductor (stereo) mini-jack that is specifically designed for
connection of a high-impedance (10k-ohm) audio source such as a tape deck.
Headphones Out - This input uses a three-conductor (stereo) mini-jack that is designed for
connecting a set of 16-ohm (nom.) stereo headphones or powered speakers. Plugging into the
Headphones jack mutes the signal to the internal speaker and the Line Out jack as well.
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 (Record In) jacks, an amplifier's Line In jacks, or to powered speakers that
contain amplifiers.
5-28 hp compaq d330 and d530 Series of Personal Computers
Featuring the Intel Pentium 4 Processor
First Edition – June 2003