WAR OF THE WHIRLS

Although we have had digital recording in a number of formats for more than 15 years, it really didn't become the most highly regarded recording method until the launch of the Compact Disc. Since that time, there have been significant developments in digital recording which have brought CDs to their present state of technological refinement. Music reproduced on a state-of-the-art CD player can be stunning in its realism, when it involves a digitally mastered disc that has been recorded by a top-flight engineer using the best digital equipment available.

However, there still are members of the die-hard anti-digital brigade, people who loathe CD and digital recording. It must be remembered that their antipathy to digital recording predates the Compact Disc. For a number of years prior to CD, they were bemoaning the fact that vinyl phonograph records were increasingly being cut from digitally recorded masters. Those in this group who listened primarily to classical music were particularly distressed, because by then most new classical recordings were being digitally mastered.

When the first CD players and Compact Discs appeared on the market, the anti-digital types vehemently dismissed the whole CD concept as "inherently unmusical." While this blanket condemnation of CD was grossly over stated, obviously colored by a dislike of digital recording, I must point out that there were certain sonic artifacts and anomalies in the very earliest CD players and discs. Some CDs did in deed exhibit varying degrees of wiriness and stridency in passages for high strings, and audiophiles with acute ears did notice a slight distortion at very low levels. The stridency of these early CDs, some said, was a consequence of employing steep 90-dB "brick-wall" anti-aliasing filters, which generated high-frequency spuriae. By far the most common com plaint, however, was of acoustic "dryness" caused by an attenuation of hall ambience and truncation of reverberant decay. Some felt that the loss of ambience and reverberant decay, as well as the low-level distortion, were due to the lack of a dither signal in early digital recorders. Without the dither signal, these recorders could not resolve down to the least significant bit, hence the distortion and ambience anomalies.

It should be noted that even in the earliest CDs, the attenuation of reverberation did not frequently occur: At that stage of their development, most digital recorders did employ dither signals in their circuitry. In spite of this fact, the anti-digital forces regularly cited loss of ambience as one of their principal objections to the CD. Digital recordings from 1981 onwards almost certainly will have been made with a dither signal. Thus, any loss of ambience noted by "digiphobes" on current digitally recorded CDs is a figment of their imaginations.

There were other factors said to con tribute to the less-than-pleasant sound of some CDs, such as the type and deployment of microphones, distortion and noise originating in mixing con soles, and other diverse noise phenomena. Further, opponents of CD still persist in the notion that if a CD is made from an analog master, it is somehow degraded and does not sound as good as the same recording reproduced as a vinyl phonograph re cord. Well, there are reasons why the digiphobes may perceive a difference between the sound of an analog-mastered LP and an analog-mastered CD, but most certainly it is not a degradation of quality.

In most instances, the digiphobes base their opinion on comparing a vinyl LP and a CD of the same recording. Apart from the fact that an LP's quality will degrade the more it is played, the digiphobe fails to consider the limitations of the phonograph medium and the limitations of stylus cutting geometry. Don't get me wrong! In the hands of a cutting expert like Stan Ricker or Bob Ludwig, truly spectacular sounds have been engraved on a phonograph disc. But these worthy gentlemen would be the first to tell you that certain signals on a master tape cannot be cut onto a lacquer without some sort of technical compromises.

In the case of transferring analog recordings to CD, various record companies have different ideas of how this should be accomplished. Some will just go back to the cutting master for transfer to CD. Generally this cutting master has had considerable manipulation and processing in respect to equalization and possible dynamic compression, in order to accommodate it to the vinyl medium. If the original master was a 16- or 24-track re cording, you can imagine the incremental losses in the mix-down to the two-channel cutting master. Some conscientious companies will go to the expense and trouble of transferring the original multi-track recording to digital tape and then use it to prepare their CD masters. CDs made in this manner generally sound much better than the same recording on the digiphobe's vinyl disc. Other firms will simply re equalize the cutting master, and the resulting quality is quite variable.

Drawing on my own experiences with CD and digital recording, I do think that on a few CDs there was a perceptible loss of hall ambience. In fact, I still have several CDs that exhibit this particular anomaly. I also still own quite a few CDs which certainly have steely, strident first violins when played on an early CD machine. These same discs, when used in newer CD players, models which employ quadruple over sampling and a much more gentle filter slope, sound far less strident.

As to the digiphobes' allegations about CD degrading the sound of analog recordings, I recently conducted a most interesting experiment. I have a CD of Gustav Hoist's "The Planets," performed by a major symphony orchestra and conductor. I also have a 15-ips, Dolby A, open-reel copy of the analog master from which the CD was made. I played back the tape on an Ampex ATR100 and played the CD on a Sony CDP-705ESD and an Analogic player, both excellent units employing quadruple oversampling. Although I could not synchronize tape and CD playback exactly, it was close enough for a good NB comparison through the quick relay switching of a Rowland Re search Coherence One preamplifier. I found that the sound of the tape and that of the CD were virtually identical. There were no appreciable differences in frequency response, the full dynamic range of the tape was perfectly mirrored on the CD, and signal-to-noise ratio was well matched. Obviously, an analog master tape recording can be transferred to CD with total integrity of all sonic parameters.

I decided to make another comparison. This time, I used two recordings of Mendelssohn and Tchaikovsky violin concertos played by a famous virtuoso. The first was a one-to-one copy of a nine-year-old analog master (it too was a 15-ips open-reel tape, recorded with Dolby A NR); the second was a 1981 digital recording issued on CD in 1983. Once again, I played the CD on the Sony and Analogic machines and played the tape on the Ampex. The A/B comparison between analog and digital recordings was fascinating! Of course, the more recent digital recording confirmed the maturity of the artist, as well as an even more dazzling technique. The digital CD outperformed the analog tape in terms of signal-to-noise ratio and dynamic range. In addition, the CD was a generally cleaner, more well-defined recording, and bass response was more extended and more articulate. Both recordings were made by top-notch engineers, who achieved excellent balances between soloist and orchestra. Both engineers man aged to give their recordings a nice, warm ambience. Ah, but what about the string tone? In both cases, the solo violin was well focused; tonal smoothness was equally good. The first violins on the tape were smooth and clean, with a beguiling harmonic richness. The first violins on the CD were very articulate and open, with smooth, accurate intonation.

Did the tape sound more natural, closer to the music than the CD? It really comes down to a matter of taste. There are colorations on the tape which impart a certain mellowness to the overall sound, which many will equate with that much-abused term, musicality. The CD has a more sharply focused sound. I contend it is a more accurate sound and a more sonically exciting sound. Perhaps the best way to describe it is to say that the sound of the tape reminds me of Carnegie Hall, while the CD sound transports me to Avery Fisher Hall.

To wind things up (and offer a capsule curriculum vitae), I gently remind the digital nay-sayers that I have re corded stereo sound for 37 years on virtually every medium. Digital recording is the most transparent medium we have. Used intelligently, it will, in my opinion, give us our closest approach to the live musical experience.

(adapted from Audio magazine, July 1987; Bert Whyte)

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