In the October 1994 Stereophile (Vol.17 No.10, p.39), I discussed my experiences with the DTS audio data-reduction code/decode switch box, which, briefly, is a two-channel box that makes use of the algorithm DTS has proposed for their version of discrete multichannel sound for laserdiscs.
Back in the spring of 1990, Stereophile introduced its first Test CD, featuring a mixture of test signals and musical tracks recorded by the magazine's editors and writers. Even as we were working on that first disc, however, we had plans to produce a second disc which would expand on the usefulness of the first and feature a more varied selection of music. The result was our Test CD 2, released in May 1992.
Anyone who's ever looked for it knows how rare audio-friendly living space is. Perhaps someday an enterprising developer will build Audiophile Acres---a whole subdivision of audio houses or soundproofed condos that'll meet these needs---then stand by while hordes of long-suffering audiophiles stampede the sales office, frantically waving down-payments in their sweaty hands.
If you read much promotional literature for recently introduced high-quality equipment, you'll notice a common theme emerging: balanced connection. Balanced inputs and outputs are becoming a must for any audio equipment that has any claim to quality. The word itself has promotional value, suggesting moral superiority over the long-established "unbalanced" connection (for the purpose of this discussion, I will call this "normal"). What's my problem with this? Simply this: The High End could be paying dangerous, costly lip service to the received wisdom that balanced operation is the goal for an audio system.
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.
That was the question asked by a reader who was perfectly happy with his CD-based system. He was using the gain control provided by the variable output of his CD player and was apparently in no need of phono playback or greater flexibility. He asked us to answer this question, ignoring for the moment the obvious functions of switching, volume and tone control, and phono preamplification. With those hardly trivial qualifiers—and bearing in mind the high output available from many of today's line sources, CD players in particular—do you really need the added expense and complexity of a preamplifier?
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.
Not that long ago, digital audio was considered perfect if all the bits could be stored and retrieved without data errors. If the data coming off the disc were the same as what went on the disc, how could there be a sound-quality difference with the same digital/analog converter? This "bits is bits" mentality scoffs at sonic differences between CD transports, digital interfaces, and CD tweaks. Because none of these products or devices affects the pattern of ones and zeros recovered from the disc, any differences must be purely in the listener's imagination. After all, they argued, a copy of a computer program runs just as well as the original.
Until recently, all problems in digital audio systems were blamed on either the analog/digital converters (ADCs) used in mastering or the digital/analog converters (DACs) needed for playback (footnote 1). As the performance of both ADCs and DACs improved, however, a previously unrecognized mechanism for distortion was unmasked: jitter. As we shall see, jitter—or, more correctly, word-clock jitter—can be a significant limitation in the technical and sonic performance of digital audio systems (footnote 2).
Subjective audio is the evaluation of reproduced sound quality by ear. It is based on the novel idea that, since audio equipment is made to be listened to, what it sounds like is more important than how it measures. This was a natural outgrowth of the 1950s high-fidelity "revolution," which spawned the notion that a component, and an audio system as a whole, should reproduce what is fed into it, without adding anything to it or subtracting anything from it.
What is the angular separation of your loudspeakers as viewed from your favorite chair? Whatever your answer, it's wrong. Of course I don't mean that it's a factually incorrect answer, just that any single value of subtended angle cannot be ideal for all recordings.
Though we sometimes take for granted that the basic "language" of our measurements is clear to all of our readers, letters to the editor tell us that this is not the case. Periodically, then, we will attempt to explain exactly what our measurements are and what they purport to show. Though those with technical training may find our explanations a bit simplistic, they're aimed at the reader who lacks such experience.
I recently scoured my shelves and came up with the following list of must-read books for stereophiles, all of which are in print and should be available from specialist bookshops or from the suppliers mentioned in the text. Books marked with an asterisk (*), though too technical for the general reader, will be found rewarding by those who have a good grasp of mathematics and who want to delve deep. Reading the books in the first "general" section of the list will enable readers to understand just about everything that appears in Stereophile, but all the books listed contain between their covers untold treasures.