Analog or Digital?

"Isn't Digital Always Best?"

The word "digital" is bandied about so much by today's marketing mavens that it has lost much of its meaning. Anytime our friends from Madison Avenue and the like want to emphasize the quality of virtually any type of electronic device, the word digital won't be far behind. "Oooh, Mr./Mrs. Customer - look over here - our new widget is DIGITAL - so you know it must be better!"

But is that really the case? Should you always use a digital connection? Can you? Let's review the good, bad and the ugly of digital and analog connections for video and audio.

Pocket Protector Stuff

First, let's get the physics-speak out of the way. In the end, we are analog beings - our eyes transform light into objects that our brains recognize, and our ears process physical sound waves as the things we hear.

Analog connections take these light and sound waves and transmit them as electrical signals. Digital connections also carry electrical signals, but what is sent over the wire (or the air in the case of wireless technologies) are little on's and off's - better known as "1's" and "0's", or "bits". These 1's and 0's are a representation of the analog waves that we see and hear. Perhaps easier understood: a string of 8 of these on/off's can also be used to represent a letter of the alphabet (this string is called a "byte").

There are trade-off's with both analog and digital signals. The problem with analog connections in a home audio or video system is that these connections are susceptible to interference of all kinds. While you may see an image or hear sound, it may not be perfect because of electrical "noise" that can spoil things. Think of ghosts on cable television channels, or static sounds in AM broadcasts and you'll know what we mean. Conversely, a real strength of digital transmissions is that it is truly either "on" or "off" - if you receive sound or a picture, it is exactly what was originally transmitted.

But, again, since a digital signal is just a representation of the original sound and light waves, the quality of that representation is critical. This is where gearhead terms like "sampling rates" and "compression algorithms" come into play - they refer to how close the digital signal is to the original. A great example: some audio purists to this day still insist that CD's never have captured the sonic "warmth" of their beloved vinyl record albums. That is because the sampling rate used is lower than some would like - an issue addressed by the industry with DVD-Audio and Super Audio CD (SACD).

Now, Back to the Real World

Why should you care about any of this? Because we are moving inexorably towards fully digital environments for audio and video. But we're not there yet, and this transitionary period presents many pitfalls. While it is always best to minimize the number of digital-to-analog conversions, and most/all of your media today is stored/delivered digitally (CD's, DVD's, satellite TV, some cable TV, etc.), assuming that digital is always the way to go can be a mistake - here's why.

Audio: We've Almost Arrived

The world of audio is much farther along due to the truly revolutionary impact the compact disc made over 20 years ago. The convenience and quality of CD's rendered vinyl albums and cassettes obsolete virtually overnight. In order to avoid an unnecessary digital-to-analog conversion, home audio gear soon appeared with digital connections - the trusty old RCA patch cords you used to hook up your turntable or cassette deck were no longer the way to connect your gear. Better to use digital connections and minimize the conversions.

That is indeed still the case today - in fact, a digital connection is required if you wish to hear the surround sound as the film or TV show director intended - soundtracks are encoded in Dolby Digital (and/or DTS) formats, and these are only transmitted over digital connections between your gear.

So just use digital connections and everything's fine - right? Uh - no. There are two important situations where an analog audio connection is still required. The first is for multizone audio systems - many of the systems we install allow one source to be heard in the 'main' zone, while something different can be heard in the 'second' zone. But most multizone receivers will not pass a digital audio signal to their second zone outputs - meaning both digital and analog connections must be used if you wish to hear sound in a second zone.

The other exception: DVD-Audio and SACD. Because of the never-ending paranoia of the big media companies, they've prohibited consumer electronics companies from using digital connections between DVD-A/SACD players and A/V receivers - meaning you need SIX analog connections (one each for the front left, center, and right channels, one each for the two surround channels, and one for the subwoofer), instead of a single digital connection that could carry it all. Perhaps this insanity is why DVD-Audio and SACD have essentially gone nowhere?

Every Picture Tells a Story?

Now onto where the digital action really is: video. By now you probably know that in order to view high definition TV (or DVD's at their best), you need a digital television. That's because HDTV is a digital medium - the path from the network, to your local network affiliate, to the cable or satellite company, and then to your set-top box is completely digital.

But for the first several years of HDTV and digital TV's, there were no digital connections on either the set-top box or TV; instead, component video (an analog connection) was what was used - the digital signal was converted to analog by your set-top box, sent as analog signals to your display, and then converted back to digital by the display. This worked (and works) fine - but it does introduce an unneeded digital-to-analog-to-digital conversion. So digital interface standards (DVI first, now HDMI) were created - these eliminate the digital-to-analog conversion. In theory, this should provide digital video nirvana - but of course, it doesn't.

Why? Because DVI and HDMI also provided a means by which the media companies could protect their cherished content from "Napsterization" - both DVI and HDMI include as part of their specifications copy protection schemes. While DVI and HDMI are "standards" , their implementations vary, and thus we often see incompatibilities that prevent you from seeing a picture at all. Not good - and while this will eventually sort itself out, for now, when we install systems, we still rely primarily upon component video connections.