Reference

Editor's Note: In the 21st Century, lossy audio data compression, in the form of MP3 and AAC files, Dolby Digital and DTS-encoded soundtracks, and YouTube and Spotify streaming, is ubiquitous. But audiophiles were first exposed to the subject a quarter-century ago, when Philips launched its ill-fated DCC cassette format. What follows is Stereophile's complete coverage on both DCC and its PASC lossy-compression encoding from our April 1991 issue.—John Atkinson

Virtually all of the active components in your system—DACs, preamplifiers, power amplifiers—work by modulating the DC output of their power supplies with an AC music signal. Surely, then, the more perfect your household AC is, the more perfect your audio system's output will be. Analogies abound—to dirty water used in distilling good whiskey, to inferior thread used to weave fine fabrics—and all amount to the same thing: you can't make a silk purse out of a sow's ear.

On a number of occasions we have commented on the effects of an amplifier's output impedance on a system's performance. A high output impedance—such as is found in many tube amplifiers—will interact with the loudspeaker's impedance in a way which directly affects the combination's frequency response. The Cary CAD-805, for example, has a lower output impedance than most tube amplifiers, and should be less prone to such interaction. Some months back—before the CAD-805 arrived—I investigated this phenomenon in conjunction with measurements for a forthcoming review of the Melos 400 monoblock amplifier. Since the Melos 400 also had a relatively low output impedance for a tube amplifier (at 0.43 ohms at low and mid frequencies, rising to 1.2 ohms at 20kHz, from its 8 ohm tap), I took that opportunity to run some frequency-response measurements using an actual loudspeaker as the load for the amplifier.

In the world of digital audio, jitter has been a focus of audiophile attention for well over a decade. It is blamed for many of the sonic ills of which CD and other digital media have been accused. But here's a puzzle: The major source of frequency intermodulation distortion in audio systems—the loudspeaker—has largely escaped such withering inquiry. Why?

One of the challenges I faced in optimizing the performance of the Thiel CS7.2 loudspeakers that I reviewed in February 2000 was controlling and tuning their interaction with my listening room. Intuition, experience, trial and error—all came into play, as did several of the procedures and calculations covered by Jonathan Scull in his "Fine Tunes" column.

High-end audiophiles are space freaks---we relish the warmth and spaciousness of a fine, old performing hall almost as much as we do the music recorded in it. But my attendance at a series of orchestral concerts held last summer brought home to me---as never before---the sad fact that our search for the ultimate soundstage is doomed to failure: we're trying to reproduce three-dimensional space from a two-dimensional system, and it simply can't be done.