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How Digital Audio Connections Work

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Hooking up a DVD or CD player for optimal sound requires the use of a digital audio connection. In this article, Michael Miller describes the different types of digital audio connections, and shows which are best for various uses.
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Analog audio is so last century. All of our 21st century audio and video equipment decodes digital audio, which provides better sound than the old analog formats. But to hear all the glorious fidelity of a digital audio soundtrack, you can't connect your CD or DVD player to your receiver via the traditional right-and-left RCA audio connections—instead, you have to make a digital audio connection. Read on to learn more.

Understanding Digital Audio

The first home digital audio medium was the compact disc, introduced in the early 1980s. Unlike older analog media (such as the vinyl record or the cassette tape), music on a CD is encoded via a series of 1s and 0s—digital bits. The more bits in a recording (that is, the higher the bit rate), the more accurate the sound.

One of the great things about digital recordings is that they don't deteriorate. Remember how those old LPs would start to hiss and crackle after several playings? Not so with digital media. The music on a CD sounds exactly the same after a thousand playings as it did when first out of the jewel case.

The digital bits on a CD or DVD are read by a laser in your CD or DVD player, and then have to be fed to the amplifier in your audio/video receiver. Most CD players include a digital-to-analog converter (DAC), which does just what the name implies—it converts the digital signal to an analog signal. This analog signal is then fed through the traditional right/left RCA-jack audio connections through a right/left audio cable to the right/left audio input of your A/V receiver. The receiver then amplifies the signal, which is what you hear through your speakers.

Better sound can be had, however, if the original digital audio is kept digital throughout more of the process. To that end, most DVD players (and some high-end CD players) feature digital audio outputs. Connect a digital audio cable to the DVD player's digital audio output jacks, feed it into the digital audio input jacks on your A/V receiver, and you have a completely digital transmission path. The decoding of the digital signal now takes place inside your A/V receiver, typically via the built-in surround sound decoder. (You see, the digital audio on a DVD consists of more than two channels; DVDs can hold up to 5.1 channels of information, which is what you need to listen to surround sound movies.)

So if you have a digital audio output on your CD or DVD player (or satellite receiver or cable box), you should use it; the sound will be noticeably cleaner, with a wider frequency response. But what kinds of digital audio connections are available—and which should you use?

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