Audio Hardware and Sound Cards

With the increase of multimedia applications for PCs, many systems now feature integrated audio hardware. Sound cards with greater 3D audio performance and more options remain popular upgrades. Sound cards can be used for the following tasks :

• Digital conversion of prerecorded audio

• Playback of CD-ROM or Web-based audio content

• Recording of sounds or speech

• Voice control and dictation

• Text-to-speech (computer "reads" text)

Sound cards and systems with integrated audio have distinctive internal and external features, as you will see in the following sections.

External Features

Systems with integrated audio have two or three jacks for speakers , microphone, and headset or auxiliary output. Some also feature a 15-pin game port (see Figure 8.24). The game port can also be converted to a MIDI port (used for connecting to a MIDI synthesizer) with an optional adapter.

Figure 8.24. Game port and audio jacks on the rear of a typical ATX system with integrated audio. Similar connectors can be found on most sound cards.

Low-end sound cards typically have similar connectors. More advanced sound cards as well as better-integrated audio solutions also feature digital output through the S/PDIF connector, and some also integrate IEEE-1394a ports for direct connection to digital media sources such as DV camcorders (see Figure 8.25).

Figure 8.25. The Hercules Digifire 71 is a typical high-end sound card with both digital and analog speaker outputs and IEEE-1394a ports. Photo courtesy Hercules.

Internal Sound Card Features

All sound cards have at least one four-wire internal jack to enable music CDs to be played through the sound card's speakers. Most recent models also feature a two-wire digital audio jack for pure digital CD playback and for fast conversion of digital CD audio into compressed audio files such as MP3 or WMA (a process called ripping ). Most motherboards with integrated audio have the analog jack, and some also have a digital jack. Figure 8.26 provides a typical example.

Figure 8.26. Analog (left) and digital (right) connections between optical drives and a typical sound card. The TAD jack on the sound card can be used to connect a modem with a telephone answering device (TAD) feature, and the AUX_IN jack enables a second optical drive to be connected to the sound card with a four-wire analog audio cable.

tip

Most recent sound cards and motherboards use the PC99 color -coding standards for built-in and add-on ports. Although most port types have distinctive shapes and sizes, analog audio jacks are all the same size ! Use this guide to keep from plugging stuff into the wrong jacks:

Port	Color Coding
Audio line in	Lt. blue
Audio line out	Lime
Microphone	Pink
MIDI/Game port	Gold
Speaker out/Subwoofer	Orange
Right-to-left speaker	Brown

Get the full story for all port types along with color samples at http://www.pcdesguide.org/documents/pc99icons.htm.

Sound cards that feature FM synthesis for MIDI files might also have a connector for a wavetable daughtercard. Some very old ISA sound cards might also feature proprietary or IDE CD-ROM data cable connectors.

Types of Sound Hardware

Sound cards can be installed into the expansion slots of a computer (ISA or PCI), or the equivalent sound circuits can be integrated into the motherboard. Both slot-mounted and integrated sound circuits will be referred to as sound cards in this section, except as noted.

Sound cards differ in their capability to handle different forms of audio content. All sound cards can play back digitized sound, but they differ in the quality of sound they can record and play back and in how they play MIDI musical scores:

• 8-bit sound cards cannot record or play back high-quality sound, but are long obsolete and rare. These old sound cards use only a single-edge connector for the 8-bit portion of the ISA slot.

• 16-bit or better sound cards can record and play back high-quality sound (44 kilohertz [KHz] or higher sampling rate). These cards are 16-bit ISA on older systems or PCI (32-bit) on newer systems.

• FM synthesis cards must create artificial versions of musical instruments to play MIDI scores. MIDI scores played on this type of sound card have poor musical quality.

• Wavetable cards use actual samples from real musical instruments to play MIDI scores. Some older cards used onboard modules to store audio samples, but most recent cards use system memory for this purpose.

Most recent sound cards use wavetable synthesis.

Physical Installation and Replacement

Sound cards that use jumper blocks for configuration should be set before installation into the system. However, most recent sound cards are configured with software or by Windows 95/98/2000/XP's Plug and Play technology.

Because the sound quality of sound cards can be affected by interference, the best results are obtained if you can install the sound card into a slot that is one slot away from other cards and as far away from the power supply as possible.

Follow this basic procedure to install a sound card:

1. If the system already has onboard sound, disable it to prevent conflicts. Typically, you'll need to restart the system and take a quick trip through the system BIOS setup screens. On some systems, there's only one setting along the lines of Integrated Sound or Integrated Audio to disable. Others might require you to disable several settings, such as in the example in Figure 8.27. Save the changes in the system BIOS and restart the computer.

   Figure 8.27. A BIOS setup screen from a typical system with onboard audio. You can leave the game port enabled on this system if you need it and the new sound card doesn't have one.

   

2. If the system has a built-in sound card, open the System Properties sheet's Device Manager and remove references to the sound card (see Figure 8.28). Then, shut down the system and remove the card after you disconnect the cables.

   Figure 8.28. A sound card's resources might be listed under multiple headings, as seen here: The ENSONIQ AudioPCI, ENSONIQ AudioPCI Legacy Device (for Sound Blaster emulation), and Gameport Joystick are all part of a single sound card.

   

   tip

   

   As you disconnect cables from the old card, mark them if they are not color coded or if the colors of the new card's jacks don't match the colors used on the original cables.

3. Install the new card in an empty slot. If you are upgrading to a better PCI sound card, you can use the same slot. If you are replacing an ISA with a PCI card, you need to use a PCI slot.

4. Connect optical drives to the jacks on the inside of the card. Most optical drives include the four-wire audio cable illustrated in Figure 8.26, but you might need to buy a two-wire audio cable from an electronics or computer store if you prefer all-digital sound.

5. Connect speakers and microphone to the jacks on the rear of the card.

6. Restart the system and install drivers as needed. You might need the Windows CD (or determine where the .CAB archive files for Windows drivers are located) to install support for some sound card features.

Default Sound Card Hardware Configuration

The default configuration of sound cards differs depending on whether the sound card will be used for MS-DOS programs or for Windows programs. A Plug and Play sound card running under Windows will use any available resources. However, if the card will be used for MS-DOS programs, the card needs to emulate the Creative Labs Sound Blaster Plus or Sound Blaster 16 and use the same settings these cards used.

To perform Sound Blaster (SB) emulation, some older sound cards used a special four-wire PC/PCI cable that attached to the motherboard. However, most recent sound cards include a special program that must be run before an MS-DOS program requiring sound can be used in Windows 9x. Windows XP provides built-in SB support for MS-DOS and older Windows programs.

Note also that third-party sound cards might use two sets of settings: a native set and an SB-compatible set. These sound cards thus consume even more hardware resources than those shown in Table 8.8.

If you need to manually configure a sound card to use the same settings as a Sound Blaster card, use the settings shown in Table 8.8. Note that PCI sound cards emulate DMA settings and can share IRQs, but any ISA sound cards you might still encounter use actual DMA channels and non-shareable IRQs that can conflict with other ISA or PCI devices.

The configuration listed in Table 8.8 is based on the defaults used by the Creative Labs Sound Blaster AWE64 Gold card. Most other brands of sound cards use similar settings.

Table 8.8. Standard and Optional Hardware Settings for Creative Labs Sound Blaster AWE64 Gold (Options for Some Settings in Parentheses)

Feature	IRQ	DMA 8-Bit	DMA 16-Bit	Starting I/O Port Address
Audio	5 (2,7,10)	1 (0,3)	5 (6,7)	220h (240h, 260h, 280h)
FM synthesis	N/A	N/A	N/A	388h
Joystick port	N/A	N/A	N/A	200h
MPU-401 (MIDI) standard	N/A	N/A	N/A	330h (300h)
Wave synthesis (select one)	N/A	N/A	N/A	6x0, Ax0, Ex0 (x=0-9,a-f)

This card uses one IRQ, two DMA, and up to five different I/O port addresses.

With some cards, you can use the Windows Device Manager to select some "stripped-down" configurations that omit certain features.

Because sound cards are resource hungry, the sound card should be the first add-on card installed in any system.

As Table 8.8 indicates, sound cards have multiple hardware devices onboard. Figure 8.28 shows that the Windows Device Manager displays each hardware component in a sound card as a separate device.

Sound cards used with MS-DOS (or with the MS-DOS mode of Windows 9x) need

• The appropriate sound card driver to be installed in Config.sys .

• A SET statement in Autoexec.bat indicating card type and settings. In Figure 8.29, an actual SET statement used with a wavetable Sound Blaster card is listed, along with a key.

  Figure 8.29. A SET BLASTER statement used with a typical wavetable-equipped Sound Blaster sound card (AWE32). The legend is listed below the SET BLASTER statement.

  

Some third-party ISA sound cards use two different SET statements (one for native mode, and one for SB-compatible mode). These cards might use even more resources than those shown in Figure 8.29.