Reference

Jitter is not what digital sound quality induces in the listener; rather it is the instability in the clock signal that controls exactly when the analog waveform is sampled in the original A/D conversion, or when the digital word input into a DAC results in an analog voltage being produced at the chip's output. "So what?" is the response of digital advocates, "As long as a digital one is recognized as a one and a digital zero as a zero, then how can there be any difference in sound?" goes their argument, normally culminating in a fervently expressed "Bits is bits!"

Tweaks have acquired a bad reputation in certain sectors of the audio world, probably with some justification. Warming the cartridge to exactly the right temperature, suspending cables from the ceiling (but not with cotton string; it sounds grainy and dry), stroking CD cases with a "magic" brush, drinking "polarized" (or is it de-polarized?) water before a listening session---gimme a break!

In "Music and Fractals" in the November 1990 issue, I discuss how digital audio's quantization of amplitude information in what was originally a continuous waveform represents a fundamental difference between analog and digital representations of music. In a letter published in the English magazine Hi-Fi Review in January 1990, John Lambshead conjectured that naturally originating sounds were pseudo-fractal in character; that is, their waveforms have a wealth of fine detail, and that detail itself has an even finer-structured wealth of fine detail, and so on, until the crinkliness of the waveform is finally enveloped in the analog noise that accompanies every sound we hear.

"The large peak at 16kHz reported by Stereophile...was nowhere in evidence...The most probable explanation of this discrepancy is that the [Waveform supertweeter's] very light ribbon depends on the air load for damping, and that load is much smaller in the thin air up there at 7000' in Santa Fe than at altitudes where less lightheaded and scientifically more accountable reviewers dwell." Thus spake Peter Aczel (footnote 1), erstwhile loudspeaker designer and Editor/Publisher of the reincarnated The Audio Critic, a publication that advertises itself as having "unusual credibility among the top professionals in audio."

The promise of "perfect sound forever," successfully foisted on an unwitting public by the Compact Disc's promoters, at first seemed to put an end to the audiophile's inexorable need to tweak a playback system's front end at the point of information retrieval. Several factors contributed to the demise of tweaking during the period when CD players began replacing turntables as the primary front-end signal source. First, the binary nature (ones and zeros) of digital audio would apparently preclude variations in playback sound quality due to imperfections in the recording medium. Second, if CD's sound was indeed "perfect," how could digital tweaking improve on perfection? Finally, CD players and discs presented an enigma to audiophiles accustomed to the more easily understood concept of a stylus wiggling in a phonograph groove. These conditions created a climate in which it was assumed that nothing in the optical and mechanical systems of a CD player could affect digital playback's musicality.

The end of two audiophiles' friendship:

Wouldn't you just know it. As soon as I decide on a formal regime of measurements to accompany Stereophile's loudspeaker reviews—see Vol.12 No.10, October 1989, p.166—along comes some hot new technology that changes everything. Robert Harley reported in last month's "Industry Update" column how impressed he and I were with the new MLSSA measurement system from DRA Laboratories.