Analog vs Digital: Home-Brew Science at the Edge of the Art

Publisher’s note: The following article, from the early days of Compact Disc, is presented with no claim for absoluteness. (In fact, just as we go to press in the spring of 1986, we received a manuscript from Philip Greenspun, Product Review Editor of Computer Music Journal (Cambridge, MA), who had precisely the opposite result when comparing CD to analog versions of the same recording, though it was unclear that his test procedures were as thorough as in the tests by these authors, footnote 1.) The tests described are neither single- nor double-blind, and the author’s decision to forego conversation while listening to the same products does not by any means guarantee lack of mutual influence—especially because their musical tastes are so well known to each other. Moreover, repeating the test with different phono equipment, a different CD player, and a different replica of the master tape would likely yield somewhat different results.

Nevertheless, I think the basic conclusion is sound: good CD reproduction is remarkably close to a fairly good version of master tape sound; there’s a good chance that it’s more accurate than what you’ll get from the average cartridge, tonearm, and turntable.

J.Gordon Holt plans to do some solid investigatory work at record companies on the West Coast, hoping to hear just what degradations occur when going from analog (and digital) master tape to record, CD, and analog copy. His results should prove fascinating.—Larry Archibald

It’s a rainy Saturday afternoon, and you’re in your favorite record store. Windham Hill has just released a new George Winston performance on both LP and CD. Which do you buy?

As music lovers and committed audiophiles, we’ve been wrestling with this conflict for more than two years. Considering the hype from the CD promoters, as well as the obvious vested interests of the detractors, it’s difficult to know what to believe. We finally decided that the only way to resolve this dilemma for ourselves was to devise a listening test stringent enough to determine the absolute quality of digital versus analog disc reproduction.

The improved second- and third-generation CD players on the market also made us feel the time was right to determine whether digital reproduction is good enough for the most critical audiophile. We wanted to use equipment with resolving power at or near the state of the art. The method we describe for these evaluations does not require special test equipment and can be reproduced by anyone.

The Premise of the Listening Test
Because we were aware of the vagaries of subjective evaluations, we sought some reference standard to which we could compare the accuracy of CDs, and analog records (ARs). In our previous comparisons of performance-matched ARs and CDs, we had discerned significant differences. The problem with these tests was our inability to know what the original master tape sounded like. We reasoned that an analog copy of the original master tape could be used as a control to judge the faithfulness of either CD or analog record playback to the original recording (footnote 2). According to the digital critics, even though a first-generation analog copy of an original analog master tape might suffer some degradation, it should be free of presumed digital artifacts. It should therefore sound more like the AR than the CD, at least in terms of timbral balance, harmonic structure, ambience and placement of instruments, thus giving our test a mild pro-analog bias.

With Nakamichi’s recent release of high-quality real-time cassette copies of master tapes, we felt the appropriate software was now available for conducting direct comparisons between the highest quality analog recordings and their tape and CD counterparts.

The Equipment
Test System One was located in the familiar listening room of one of the authors of this article. The analog record playback system consisted of the original Rock turntable, a Triplanar tonearm, the Goldmund record clamp, and the latest Monster Cable Alpha Two cartridge (footnote 3). Overhang, azimuth, and VTA/SRA were carefully adjusted. Final characteristics of the setup were measured with an Ortofon TC3000 test computer. The cartridge/arm combination displayed only a slightly rising high frequency response of 1dB (left channel) to 2.5dB (right channel) at 15kHz, going up to 2.5–3.2dB, respectively, at 20kHz. Vertical resonance was undetectable; horizontal resonance measured 8dB at 8Hz.

The speaker system used for most of the testing was the full-range ribbon speaker from Apogee Acoustics, biamplified with two Mark Levinson ML-9 amplifiers. The preamplifier was the Mark Levinson ML-7, fitted with L3A moving-coil phono boards. A Nakamichi Dragon cassette recorder was used because of its special ability to correct automatically for azimuth and phase errors in prerecorded cassettes.

The compact disc player was the Meridian MCD, chosen for its sonic superiority over other players on the market at the time of these tests. Mogami Neglex 2497-06 was used exclusively throughout the system for shielded interconnects. The speaker cables were Kimber Kable 8PRVS.

All of the listening tests were repeated on Test System Two in the listening room of the other author. This system was composed of Goldmund speakers, Rowland Research custom-made electronics, and an Oracle Delphi turntable (with Mod Squad power supply) fitted with a Lustre GST-801 tonearm and Panasonic Model 451C strain gauge cartridge. The Meridian MCD and Nakamichi Dragon were used as before.

Randall Research wires were used, slightly superior to the Mogami 2498-06 used elsewhere in the system. The notable characteristics of this system are two: First, because of its essentially line-level output, a strain-gauge cartridge eliminates the need for any low-level preamplification stage. This should result in an increase in clarity—or reduced electronic veiling—compared with the sound produced by a moving coil cartridge. Second, the Goldmund speakers, because of their sound dispersion pattern (combined with judicious use of Sonex to damp primary reflections), permitted a better assessment of imaging compared with System One.

Footnote 1: Charles E. Zeilig, whose PHD is in physiology, left medical research three years ago to pursue his hobby. Since then he has been an audio consultant at Listen Up, Inc. in Denver, Colorado. Listen Up sells the Nakamichi Dragon cassette deck, Apogee speakers, Goldmund speakers, Monster Cable Alpha 2 cartridge, and Mark Levinson electronics mentioned in the article. Jay L. Clawson, an engineering manager for Rockwell International, has been an avid audiophile for 15 years.

Footnote 2: In reality, this statement is based on the assumption that the cassette copying and playback process involves less degradation than either analog record or CD playback. This assumption could be tested by comparing the cassette to the master tape.—Larry Archibald

Footnote 3: The Rock turntable was used because it had demonstrated to us its superiority over a number of other high-end turntables in image focus and detailing.