PORTABLE DIGITAL
I have recently been making digital tape recordings for which all of the digital equipment, plus microphones, were contained in three medium-sized tote bags, which my wife Ruth and I carried to the recording location. This "have digital, will travel" equipment consists of the new Sony PCM-F1 digital processor and SL-2000 Betapak portable VCR and associated power supplies, described in my April 1982 column in Audio and Len Feldman's review in the March 1982 issue.
I am not, however, implying that this lightweight Sony digital equipment, despite its truly excellent performance, can fully supplant professional digital recording equipment. Editing problems alone would preclude the F1 from professional use; more on this point a bit later. But for sheer high quality sound, the Sony F1 is remarkably close to the performance of professional digital recording equipment.
Recording with the F1 is a fairly simple affair. For one thing, the F1 is completely compatible with either the Beta or VHS VCR formats. The companion Beta SL-2000 portable VCR unit works quite well, with the advantage of touch-type motion controls and a digital display tape timer. Its ability to operate on a built-in rechargeable nickel cadmium battery means that with the F1, which can be similarly battery powered, you can make digital recordings outdoors.
Any of the larger Beta format recorders can be used with the F1, with the proviso that no videotape thinner than L-500 be used. An L-500 videocassette will afford two hours of continuous recording in the Beta Two mode.
The thinner L-750, while perfectly-suitable for normal video recording, is too prone to dropouts in digital recording, though BASF has just introduced a pure chromium dioxide L-750 videotape which may cope with the problem. BASF claims an extremely low noise level as well as smoother surfaces for better head drum contact.
Speaking of dropouts, in many hours of recording with the F1, I encountered just one of these pesky digital glitches. That is quite remarkable, although I will admit that I used the high-grade versions of Sony, Maxell, BASF and Fuji videocassettes, which helps to reduce the dropouts. I used both the JVC 6700 and the new JVC 7650 VHS video recorders with the F1 with complete success. In this case, since T-120 VHS cassettes have the same thickness of tape as the shorter T-90, T-60, etc., the caution here is that standard play, not extended play, must be used to record. With T-120 cassettes, this also affords two hours of continuous recording. Of course, if money is no object, the F1 can be used with U-Matic video recorders using 3/4-inch tape, but this limits you to one hour of continuous recording.
The record metering system on the F1 is quite helpful, having a peak-hold mode so that maximum levels can easily be determined. A further aid in maintaining correct levels is a rectangular, frosted or opaque area on the meter face. If maximum peaks are kept within that area, low distortion recordings are virtually assured. One absolute dictum in recording with the F1: You must not exceed 0 dB or the result is horrific clipping. Unlike analog recording practice, where levels of +3 and more are commonly reached (mostly in an effort to improve signal-to-noise ratios), even a slight excursion into + 1 dB drastically increases distortion. If you should reach +3 dB, third-harmonic distortion of 10% is the unhappy result! In my recording with the F1, if I kept my maximum recording peaks at -5 dB all was well, with dramatically low, totally inaudible levels of distortion. As you may know, digital recording has the peculiarity that distortion decreases as levels approach 0 dB, but conversely, increases at very low levels. Some people criticize digital recording for this, claiming that at-50 and-60 dB, they can hear this distortion. Since most digital recorders have third-harmonic distortion figures of about 0.2 to 0.3% at 1 kHz at 50 dB, I and other recording engineers who have made digital recordings tend to be skeptical about these assertions. If you go way down to 70 dB, third-harmonic distortion at 1 kHz may reach 2.5 to 3.0%. This seems alarming until you realize that 3% harmonic distortion is considered the tolerable upper limit in analog recording.
The F1 has low-impedance, unbalanced phone plug mike inputs. This can be a problem in running long mike lines; such a setup is susceptible to r.f. pickup. The headphone amplifier has a maximum output of 775 mV which, with medium efficiency headphones, is usually sufficient. However, when monitoring with headphones during a concert, and circumstances dictate that you must be in the hall (rather than an anteroom), the level of the live music masks the sound from the headphones. Incidentally, only the input can be monitored, there being no playback head available for off-tape monitoring. Of course, playback of the recorded tape through the headphones is possible. Thus, more headphone output on the F1 would be desirable, as would balanced mike inputs with XLR connectors. As it stands, an input console or mixer with balanced XLR inputs can be used, and its output connected to the line input jacks on the rear panel of the F1. This permits long mike lines and clears up r.f.i., but at the possible expense of signal-to-noise ratio and general sonic purity.
The F1 has a resolution switch on the rear panel, with one position being the EIAJ Consumer Digital Standard of 14-bit quantization with 44.056-kHz sampling rate. Uniquely, in the con sumer digital processors thus far on the market, the other switch position is for 16-bit recording at the same sampling rate. These switches operate only in the recording mode. On playback, the F1 automatically switches to 14 or 16 bits, depending on how the tape was encoded. I used both the 14 and 16-bit modes in my recordings, and they both sounded equally impressive. I used 16 bit more often, probably because Sony claims the 16 bit mode is "compatible with their professional 16-bit recorders." With the kind cooperation of Seymour Solomon, President of Vanguard Records in NYC, I was invited to bring the F1 to their big Masonic Temple studio to record a special program by the talented New York Quintet. Jeff Zaraya, the helpful Chief Engineer of Vanguard, made a standard analog recording of the group while I recorded them digitally on the F1. The first recording was a rather tongue-in-cheek version of the Bach Sixth Brandenburg Concerto, which included double bass and marimba! Then came a piece de occasion, specially composed by one of the Quintet musicians to explore the dynamic range capabilities of the F1. This was written in a sort of "quasi-Japanese" style wherein, from a dead silent background, you begin to notice the breathy sound of a flute becoming apparent at the very threshold of hearing. At a slightly higher level, the double bass, played arco, is heard from the right. Suddenly, perhaps 70 to 80 dB up the dynamic scale, comes a tremendous crash of a tam-tam, followed by bass drum, tympani, and cymbals. Silence again, more low and medium level sounds from flute, clarinet, double-bass, marimba, and outbursts from the huge percussion battery.
Wish the F1 and the SL-2000 Betapak, I recorded with Vanguard's mike setup, and then used a coincident pair of Beyer M130N figure-of-eight dynamic ribbon microphones in the classic Blumlein configuration. The Beyer ribbons have a particularly smooth top end and ultra-fast transient response.
In the Blumlein pattern they afforded precise instrumental imaging and localization along with a splendid presentation of depth. The playback through the F1 revealed a sound that was utterly clean, with razor-sharp attacks, great dynamic range, and an awesomely total lack of noise. The musicians of the Quintet were enthralled with the sound quality, commenting particularly favorably on the preservation of harmonic detail and the fabulous signal-to-noise ratio.
Next recording with the F1 was of the Washington Bach Orchestra at the Kennedy Center in Washington, D.C. This time Schoeps figure-of-eight mikes were used, also in Blumlein fashion. Results were again outstanding with particularly lovely string sounds and nary a trace of stridency in the Haydn Seventh Symphony. An aria, from Handel's rarely performed opera "Agrippina," featured much florid vocal ornamentation, which was totally articulate and tonally superb in the F1 digital recording.
The prestigious Berklee School in Boston, which enjoys the support and encouragement of the likes of Woody Herman and other jazz greats, holds an annual contest to select the "best high school big band on the Eastern seaboard." They recently held a big band bash with five bands, including the exciting Potsdam College Jazz Ensemble, and I was invited to record the event with the Sony F1. I once again opted for the Beyer ribbon mikes in the Blumlein pattern. This might seem an odd choice for a big band, but as they were arrayed in concert fashion on the stage, it worked very well, with good localization along with plenty of punch and sharp attacks--a very exciting group captured very accurately.
I hope I have whetted your appetite for digital recording with the versatile Sony PCM-F1. I hear voices protesting, "Hey Bert, the idea of digital sound is great, but I can't make my own live recordings, so what about software?" The answer comes from that ever-pioneering company Mobile Fidelity. Gary Giorgi, the Chief Engineer, is very high on the F1 and has decided to issue prerecorded digital cassettes of a number of his productions-in both Beta and VHS formats.
He has sent me preproduction samples, including "Dark Side of the Moon" and Solti conducting the London Philharmonic in Holst's "The Planets." While it is quite true that these were analog masters, a one-to-one digital copy of the original master is quite a sonic thrill. Both productions were reproduced with awesome sonority and clarity, with the quiet sections of "The Planets" singularly free of noise. This idea holds great promise.
As you can see, I'm most impressed with the Sony PCM-F1 and for what it offers, $1,900 seems a reasonable price.
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(adapted from Audio magazine, Aug. 1982; Bert Whyte )
Also see:
Digital Techniques in Sound Reproduction-- Part I (April 1980)
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