As you pore over this website — or check out the sites sponsored by audio/video manufacturers — you will see a veritable alphabet soup of technical acronyms and jargon: CD, SACD, DSD, DVD, DVD-A, DAT, MP3, ADC, and DAC, to name but a few. Some of these will be familiar (by now everyone has heard of CD and DVD), some will be less so — others may sound technically intimidating. Don't be put off. Learn a few easy-to-understand terms and all of this hardware, software, and (most importantly) home entertainment fun will start to seem simple.

The single item that seems to cause the most confusion is the DAC — aka the digital-to-analog converter. The fact is, your home is probably filled with 'em and you never even pay them a thought.

First things first: Storing audio and video digitally
To understand what a DAC does, we first have to look at how digital storage works. In the early days of audio — back when the record was king — music was stored in the grooves on the disc itself. Because the grooves were a physical representation of the recorded soundwaves, the record was considered an analog format (based on "analogous," or "showing a likeness"). These days digital storage is all around us — everything, from the DTV signal you receive from a satellite, to your CD recordings and DVD films, is recorded and stored as a series of ones and zeroes.

Most music and video starts out analog. Before it is converted to a digital signal, it must pass through an analog-to-digital converter. This device cuts the sound frequencies into a series of phenomenally small "slices." The more slices, the greater the detail — CDs chop each second into 44,100 slices (this is called a 44.1kHz sampling rate, meaning that each second of music is "sampled" — sliced — 44,100 times). The original soundwave is now represented by a series of thin "cross-sections" that line up in the same order — if we were able to examine them closely, they would look like a jagged version of the original flowing wave. (The greater the number of samples, the less jagged the approximation.)

A higher sampling rate, like the one displayed in the righthand image, lets a digital signal contain far more detail, resulting in more accurate, natural reproduction of the original sound.

Since music and video signals also contain information concerning how loud or soft they should be, you need to do more than just reproduce the frequencies, however. You need to capture the volume changes of each individual sound within the music. This information is contained in a figure known as the word length. Just as with the sampling rate, the higher the word length, the more precise the reproduction of the original signal's loudness at any given moment. It's like using a yardstick — if you measure using the thirty-six 1" markings, you get only an approximate value, but if you use the two hundred and eight-eight 1/8" markings, you'll get a much more precise measurement.

The word length of a CD, for example, is 16 bits — thus a CD has a 44.1kHz sampling rate and a 16-bit word length (16-bit/44.1kHz for short). Video DVDs store soundtrack data at 16-bits/48kHz and DVD-Audio can store data at either 24-bits/96kHz, with 5.1-channels of sound, or 24-bits/192kHz, with stereo sound.

Got digital info? Enter the DAC
Digital audio and video information can be stored on a disc (CD or DVD), broadcast (satellite radio or DTV), or stored on your hard drive (MP3). However, we humans cannot hear ones and zeroes, no matter what the word length, so in order for us to utilize digital information we must convert it back to the analog domain. That's where a DAC (digital-to-analog converter, remember?) comes in.

Almost all digital devices have DACs built in. As far as audio DACs go, your CD player has one. So does your DVD player (although many people send the digital audio signal from their DVD player straight to their A/V receiver, which also has one or more DACs). Your satellite radio receiver certainly has a DAC and so does your DTV receiver. For that matter, so does your MP3 player, or you couldn't listen to it with headphones. (And when you've got digital audio and video signals, your components use separate DACs for video conversion.)

Amazing how a little bit goes a long way! A receiver's D/A converter is a small, hard-to-find chip buried deep within the component's "guts."

Not every DAC is the same quality, of course. Some higher quality components include built-in DACs made by companies respected for their D/A converter expertise (for example, Burr-Brown, Analog Devices, or Crystal Semiconductor). A well-made, high-quality DAC can convert tiny voltages with greater precision, to reveal more of the subtle nuances and soundstage details that can bring audio to life.

There are separate DAC components, as well. These are mostly aimed at professional audio folks, such as recording engineers and musicians, and audiophiles — folks who don't hesitate to pay high prices for incremental improvements in sound quality. Not all components allow you to transmit digital signal to outside converters, though — the digitally-encoded DSD signals on SACD discs must be converted to analog signals within the SACD player, for instance (but that's another story). Most consumers, however, find the DACs that are included in their audio/video components completely satisfactory. So, if you appreciate better sound quality (and who doesn't!), the next time you're checking out digital audio or video gear be DAC-savvy.