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Sound Cards

Video Cards

Sound Cards


Video Cards
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Computers are becoming more and more important as multimedia entertainment stations daily. They are moving move from the office into the living room to replace stereo systems, video players, karaoke machines, and even televisions.

These new ways of using the computer require specialized components such as video cards and sound cards. Even though most motherboards have built-in sound capabilities, adding an extra sound card can give you access to more audio features.

Digital Audio

Because all information in the computer is digital, sound must also be in a digital format. At some point in the chain, however, the digital audio must be converted to analog before we can hear it.

We are accustomed to digital audio because of the popularity of CDs, but prior to the introduction of CDs in the 1980s, almost all audio was analog. Analog is a continuous representation of sound. Digital audio attempts to reconstruct the analog signal as closely as possible, but no matter what the conversion is, there is still audio information missing in a digital signal.

The audio CD standard is 44.1 kHz at 16 bits. This means that the analog signal is broken up into the individual steps. There are 44,100 steps per second and each step can be represented with a number up to 16 bits (65,536). Other standards for digital audio include DVD (96 kHz at 16 bits) and DVD audio (192 kHz at 24 bits).

Motherboard - Part 1
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Before digital audio can be heard, it must be converted into an analog signal with a DAC (Digital Audio Converter). The quality of DACs varies greatly and is one of the major factors in determining the cost of a particular sound card.

Types of Audio Cards

The built-in sound processor on your motherboard uses a standard called AC 97. This standard provides support for DVD (96 kHz, 16 bits, six channels). The AC 97 spec does not guarantee quality -- built-in connections are usually fairly noisy and are not suitable for high-fidelity applications.

To get better sound and more features, you will need to install a third-party audio card in one of the PCI slots of your motherboard. You will need to determine your exact needs before yo decide on the type of card that you buy. If you simply wish to watch DVDs, you will probably be satisfied with the built-in, no-frills card. If you wish to record music, or attach a microphone to your computer, you will probably need a more advanced card.

If you are a musician or video editor interested in sound recording applications, you may need a professional quality sound card capable of multi-track recording.

Building Your Own Computer - Part 7
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What to Look For

Sound cards have published specifications, which give you a good idea of its quality. An important number to look for is the signal-to-noise ratio (S/N). It compares the audio signal with the background noise. The higher the S/N ratio the better the quality. The signal to noise ratio is expressed in decibels (db) and should be at least 90db. Professional cards are often rated at more than 100db.

The number of channels the sound card supports is also important. Surround sound cards are available in 5.1, 6.1 or 7.1 configurations. The .1 of these numbers indicates the subwoofer channel. This channel is used for low-frequency sounds and the first number tells you how many satellite speakers can be placed around the listening area.

If you're interested in using your computer to record sound, you also need to look at the number of inputs the sound card has. Standard inputs are one stereo pair, but cards designed for recording studios may have as many as 10 inputs.


The prices of audio cards are a good indication of their quality. Basic cards are available at $10 but the sound quality on them is quite poor. You'll find that decent quality cards start at about $50 and it is possible to pay around $400 for a professional sound card.


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