Future Tense: Digital Versus Analog

Maximum PC Staff

The column before last, I wrote about vinyl records and how amazing the technology for analog sound really is—because you’re fighting the obstinacy of the physical universe throughout the whole signal path.

During the seventies and well into the eighties, I invested quite a bit of time and money into my own sound system and I remember fondly playing with all kinds of electronic devices designed to remove clicks and pops, minimize tape hiss, expand musical peaks for more dynamic impact, and even add an extra octave of bass at the bottom.  I also added an equalizer to compensate for sonic peaks and valleys in my living room.

Bob Carver’s Sonic Hologram did a kind of electronic signal-cancelling, so you wouldn’t hear the left speaker at your right ear, nor the right speaker at your left ear.  That was a pretty astonishing effect, which has since evolved into all kinds of digital ‘spatializer’ enhancements.  You could also add two speakers at the back of your listening room to extract out-of-phase information from the stereo signal and give yourself a quadraphonic experience.

A lot of the various equalizers and signal-processors were extraordinary devices for the time, genuinely pushing the envelope of sonic manipulation and enhancement.  And remember, all of this was done in the analog domain.  Occasionally, I still see some of these devices showing up as techno-props on crime-investigation TV episodes where some nerdy-genius forensic expert is magically extracting a remarkably clear audio signal from an overwhelming hash of noise.  (If only….)

But when all of this magic worked, when everything was tuned in excellence, the room simply disappeared.  The sound came from a richly-textured concert hall, or a darkened jazz club, or the vast spaces of a stadium.  So I have a high degree of respect for what analog sound is capable of.

Last time, I wrote about how Sony and Philips designed the CD as a replacement for the vinyl record.  The technology of the compact disc was designed to meet and surpass all of the then-existing standards for high-fidelity sound:  an absolutely flat frequency response from 20hz to 20khz, a dynamic range of 95db, and an immunity to all sorts of distortion that plagued the analog signal path:  wow and flutter, rumble, tape hiss, tracking error, tracking force error, pinch effect, intermodulation distortion, and crosstalk.  Where a vinyl recording could provide only 35db of separation between the two channels, the separation in a CD was absolute.  There was no cross-channel interference at all.  Essentially, they removed the laws of physics from the signal path.

To make a digital recording you sample the sound source 44,056 times a second and record the amplitude as a 16-bit number—a value between 0 and 65,355.  On playback, you use a DAC (a digital-analog-converter) to reconstruct the sound wave.  Digital sound advocates explained that the system didn’t actually record the sound wave, it recorded all the instructions necessary to recreate the sound waves.

A lot of audio purists were skeptical.  After all, the analog groove carved into a vinyl surface was the sound wave.  How could a string of numbers contain all the same warmth and romance?  To some of these folks, digital sound was the same as chopping up a filet mignon.  Yes, you could put it all back together, but now it would just be hamburger.

So there was a lot of testing.  On the lab bench, the digital audio signals were indistinguishable from the source material.  Sine waves were accurately reproduced, so were complex wave patterns.  In double-blind listening tests, some of the best audiophiles in the world could not consistently tell the difference between the same source material presented in both analog and digital.

Some people used those tests to argue that this proved that digital recording was not superior to analog recording.  Others argued that these double-blind tests proved that analog was equal to digital.  (I’ll leave it as an exercise for the student to find the flaws in both of those arguments.

Okay, look—a lot of analog recordings have been very good.  Some have been excellent.  Analog has given us a proud legacy that deserves to be honored and preserved.  Analog sound took us through most of the twentieth century and gave us Gershwin, Stravinsky, Copland, Billie Holiday, Edith Piaf, John Coltrane, Buddy Holly, The Beatles, Jimi Hendrix, ELO, and even Rick Astley.  (You have just been virtually rick-rolled.)

Today, most sound reproduction is digital because it provides a clinically accurate signal path.  Digital recording has a superior dynamic range and is immune to wow, flutter, rumble, pinch effect, tracking error, and various other distortions introduced by the physics of the playback system.  Plus, the digital signal can be manipulated and processed in ways that are simply impossible in the analog realm.  (But that’s a different conversation.)

The real problem with digital sound is not that it is inferior to analog, but that it is superior.  It is clinically accurate.  It reveals everything.  (Just like an HDTV reveals every pore and wrinkle in a newscaster.  All the stuff you really don’t want to see close up.)

If the recording engineer has used the wrong kind of microphones or placed them badly, you’ll hear it.  If the mixer gives too much emphasis to the bass or the treble, you’ll hear the sound as boomy or harsh.  And if the producer comes in and insists that the sound be compressed so that it’s “louder”—well, right there, he’s just destroyed the best part of the digital signal.

Analog has (at best) only 55-60db of s/n ratio.  A CD has 95db.  This allows for the full dynamic range of music to be accurately recorded—everything from soft whispers to booming cannon shots.  (If your amplifiers and speakers can handle it.)

But some listeners are apparently so conditioned by the limitations of their car radios that they hear that accurate dynamic range as too loud and too soft, they want all sounds at the same volume.  So some producers have had their engineers compress the sounds, sometimes even worse than you will find on a vinyl disk, so that the recording is all of one volume—ie. “louder.”  The result, however, is a near-total loss of impact, especially in things like drum beats and cymbals and the occasional cannon or gunshot.

Digital recording has given producers enormous freedom to manipulate the signal in a wide variety of ways.  Not all of that “freedom” has been used wisely.  As with any new technology, there’s a learning curve—there are experiments, successes, failures, stumbles, and discoveries.  As any technology matures, the industry has to learn how to use it effectively.  It takes time.

A lot of the criticisms of various digital recordings in the past have been valid criticisms—a few early CDs sounded harsh because the producers used source tapes already RIAA-equalized for vinyl.  Oops.  And Jethro Tull’s Aqualung was legendary for its overall sonic awfulness, because the source tape was the wrong one.

But blaming the bitstream is the wrong place to look.

The real responsibility lies with those who are still, even today, learning how to use digital sound effectively.  Sound recording is one of those technical arts that requires insight as well as craftsmanship.  Because listening is a subjective experience, the sound engineer needs to know both the limits and the strengths of his tools and how to use them most effectively.

But after everything else has been said, I always come back to something Virginia Heinlein once said,  “Hi-fi is about listening to sound.  I want to listen to music.”

Her words were a profound reminder.  It didn’t end my audiophile enthusiasm, but it certainly shifted my perspective. It’s the music, stupid.  We’re supposed to enjoy it.


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