The A+ Certification & PC Repair Handbook (Charles River Media Networking/Security)

A sound card can act as an input or output device. It combines all the technology needed to convert audio signals to digital, and digital signals to audio, through the use of Digital-to-Analog Converters (DACs) and Analog-to-Digital Converters (ADCs).

A sound card can be integrated into the motherboard, or it can be an expansion card that is connected to the motherboard through a PCI or ISA expansion slot. As is the case with every peripheral device attached to the motherboard, a sound card requires the use of system resources, such as an IRQ, a DMA channel, and an I/O address. PCI sound cards are fairly easy to install. If the system has a plug-and-play operating system and BIOS, you just install the card into an open PCI slot and the BIOS takes care of the system resources and configuration for you. The majority of ISA sound cards on the market are preconfigured with a set of onboard jumpers that specify the use of IRQ 5. This can cause an IRQ conflict if you already have an LPT2 (a second printer port) or another device, such as a NIC, already configured to use IRQ 5. Some sound cards use special software drivers that are installed into system files, such as DOS’s AUTOEXEC.BAT and CONFIG.SYS. These system files run when the computer is started and tell the operating system to recognize that there are sound-related devices attached to the computer.

Most sounds cards are connected to a CD-ROM by a wire known as a CD audio cable that comes standard with a CD-ROM device. This allows the sound card to act as an input device between your CD-ROM and the computer system. If you are using your CD-ROM as a music device and there is no sound coming from your PC speaker or attached sound system speakers, you should verify that the wire is connected between the sound card and the CD-ROM.

Sound cards are a combination of components that allow audio to be manipulated and transferred in and out of a computer system. Some of the important components that make up a sound card are these:

• An ADC, which is a circuit used to convert infinite analog wave signals in the form of human voice, music, or camera, to digital signals (0s and 1s) that can be understood, manipulated, and stored by a computer system.

• A DAC is a circuit used to convert stored digital data back to infinite analog wave signals that are outputted to audio devices, such as a microphone or speakers.

• Analog inputs are sound cards designed with input jacks that accept low-level voltage input from devices such as musical instruments, CD players, and microphones.

• Analog outputs are designed to support sound card output to speakers. There are normally two analog outputs found on a sound card. For novices, this is where you plug in your PC speakers.

• A MIDI/game port is a sound card port that provides support for a joystick (external game device attachment). It also provides support for musical instruments and synthesizers. The MIDI/game port is often mistaken for a video card connector on the back of a computer. It is possible that on the core exam you will see a graphic of a sound card, and you may be asked to identify the joystick/MIDI port or speaker output jacks.

• Many newer sound cards have a synthesizer chip built onto the sound card. This chip is used to support external MIDI devices and uses a technology known as wave-table synthesis.