Behind the Scenes (Aug. 1977)

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The annual Los Angeles convention of the Audio Engineering Society is always held early in May and has become one of the "rites of spring" for the audio engineering fraternity. This year, the 57th convention of the AES took on added significance, since it coincided with the 100th anniversary of Thomas Edison's invention of the phonograph and also the 100th anniversary of Emile Berliner's invention of the microphone.

Thus, it was most fitting that the underlying theme of the 57th AES convention was "100 years of sound recording and reproduction," and a number of special events were scheduled in honor of the occasion. The indefatigable Jack Mullin was on hand with his Audio Museum. First shown several years ago, this fascinating display of historical artifacts and memorabilia of audio recording and reproducing equipment has been considerably augmented. In addition to the working model of the seminal Magnetophon, there was the lathe used to cut the 16-in. discs for the Vitaphone sound movies, plus one of the earliest optical sound on film projectors.

From the consumer side of audio was an absolutely massive RCA Orthophonic phono console, circa 1927, which was in working order and featured an automatic changer which played both sides of the record, intermixed 10and 12-in. records, and boasted a 12-ft. folded horn! With magnificent cabinetry, this monster sold for $1000, and that was a lot of bread in 1927. In honor of the Edison centennial and through the good offices of Mr. Oliver Berliner, grandson of Emile Berliner, the Smithsonian Institute loaned the original models of a number of pieces of historical audio equipment. Perhaps the most fascinating was the Berliner Microphone according to the publicity release it was constructed on March 4, 1877, and used a toy drum to demonstrate the "loose contact" principle now employed by all telephones throughout the world. This was the first practical demonstration showing that electrodes need not touch to pass current. (Electrodes in this "drum" microphone have a thin air-gap separation.) Another item was the original Alexander Graham Bell "liquid" telephone through which he uttered the immortal words ... "Mr. Watson, come here, I want you" ... on March 10, 1876. Barney Pisha, Audio's resident phono cartridge expert, and I were with Jack Mullin and Oliver Berliner before the official opening of the Audio Museum, and we actually spoke into the Berliner microphone and registered a response on a VTVM!


---Photo: Copyright Stanton Magnetics

In addition to the historical equipment display, another feature of the Edison centennial was a series of talks entitled "Our Audio Heritage." Oliver Berliner, grandson of the inventor of the microphone and the disc record, talked about the early days of the record business. Rex Isom, President of the Audio Engineering Society, spoke about milestones in the history of sound recording; audio pioneer John Hilliard reviewed electro-acoustics in the years up to 1945, and Marvin Camras, one of the major contributors to the science of magnetic recording, summarized the pioneering work done in this field during the 1940 decade. Jack Mullin spoke about the professional acceptance of magnetic tape recording beginning with Bing Crosby using it for his radio show in 1947, and how he eagerly awaited the arrival of Ampex recorders Serial Number 1 and 2, and how 78 rpm records (!) were cut from tape masters. Finally, Harold Lindsey, who along with Alexander M. Poniateff put Ampex into the tape recorder business, summed up 30 years of progress since the pioneering Model 200.

Exhibits

Having duly acknowledged our "roots," let us move on to what was new and significant at the 57th AES convention. As usual, the major exhibit areas were crammed with the tools of the audio trade. It is now clearly obvious that the big mixing consoles have become so complicated that automated mixdown facilities are becoming a necessity rather than a luxury option. There were so many portable mixing consoles displayed, one wonders where all this remote location recording is going on.

Digital delay systems are fast becoming a "must" for many studios, and their cost is coming down as evidenced in new models from Lexicon and Eventide. At the risk of bringing imprecations on my head, I must note that many of the items at the show were updates and evolutionary refinements of existing models. This was true of most tape machines and test equipment. Of course, there were new items, some from unexpected sources. For example, Crown International, where they were lamenting the phasing out of their tape recorder manufacturing, had a prototype of a real-time analyzer, intended for use with their new EQ-2 equalizer, which is expected to sell for less than $3000. And speaking of real-time analyzers other than the CRT screen type, !vie is now in production of their clever hand-held unit which uses LEDs. Another of this breed, somewhat larger, but still a portable unit, is that made by White Laboratories, while yet another was demonstrated by Bob Thurmond during his paper.

As is becoming more apparent every year, many of the new items of interest are on demonstration in the sound rooms on the main and the 4th and 5th floors. UREI President Bill Putnam, one of the greatest recording engineers in this country, along with inventor Ed Long, demonstrated their new studio monitor speaker which utilizes Mr. Long's "time align" technique. As you no doubt know, a number of speakers are on the market which have their drive units physically "staggered" or arrayed so that they all lie in a common acoustic plane, thereby avoiding distortion due to time delay. Mr. Long has managed to accomplish this electronically in the crossover network of the UREI speaker.

Switching back and forth between the conventional network and the "time align" network revealed a dramatic difference in sound quality, especially noticeable with male speech. The "time align" sound was very smooth and articulate, whereas the other sounded quite colored, almost as if there were a boost in the mid-frequencies.

As I reported on the 55th AES convention in New York, digital recording continues to advance. The first technical papers at this 57th convention were on digital recording, and they were very well attended. Up on the 4th floor Dr. Tom Stockham and Dick Warnock of Soundstream were demonstrating their digital recorder. This was a far better demonstration of the capabilities of their recorder than we heard in New York.

The sampling rate has been increased and the full 16-bit system is in use. In a recording of some percussion music, the sound quality was really fantastic ... super sharp transient response, ultra clean, with modulation noise blissfully absent, not a smidgen of distortion, and on a cymbal roll that began at bare audibility and increased to triple fortissimo, the 90-dB dynamic range available with this system was very apparent. Needless to say, this also afforded a recording with a dead silent background.

Mitsubishi was also showing a digital recorder, in their case a stereo PCM unit, using quarter-inch tape at a speed of 15 ips. A stationary head is used, and necessary bandwidth and bit density are achieved by encoding the audio signal in PCM and allocating the signal to nine tracks in parallel.

The sound of this recorder was quite clean and quiet, but perhaps because of the music and/or the speakers that were being used, it just did not sound as impressive as the Soundstream recorder. On the other hand, at the projected price of $10,000, it is far less expensive than the Soundstream machine.

In the dbx suite, they were demonstrating their noise reduction units and the new 3BX dynamic range expander. I mistakenly reported in a recent column that this was a single-pass noise reduction unit. It is a three band dynamic range expander, and while of course there is some noise reduction with this type of device, that is not its main function. We will report on this unit before long.

Stamper Stylus

One of the real surprises at this convention was the introduction by Stanton of a new stylus system, Model 681BPS which can perform the remarkable function of the playback of metal record stampers and matrices.

The stamper is a negative, and as you can see from the accompanying photograph, the stylus is a sort of "saddlebag" affair which straddles the ridge made by the groove. To play back, there must be a special turntable which rotates counterclockwise to the normal direction. All this is in aid of being able to check the plating quality of a stamper before records are produced, and if slight defects are noted, there are methods of physically correcting these defects. I should add that actual playback of the stamper was impressive, with a very clean top end, and really excellent transient response, probably due to non deformation of the metal, as compared to the vinyl of the standard recording. Stanton also introduced a new professional calibration standard cartridge, the 881S that uses their new Stereohedron stylus, samarium cobalt magnets, and a new suspension system.

In spite of the sad estate of quadraphonic sound, development work continues, probably in anticipation of what will happen when the FCC finally makes a decision on the choice of system for broadcasting. Thus, it was that JVC introduced a new demodulator that has what they call PTL ... Phase Tracking Loop. This is said to give better S/N ratio, wider frequency range, and improved tolerance to worn records in CD-4 recording. What I heard was impressive, and I was told that the system could be reasonably adapted to chip form if the need arose. In the CBS room, the long-awaited Tate SQ chips from National SemiConductor finally made their appearance. A claim of 35-40 dB of separation is made for this matrix system, and I must say it certainly did a good job, with none of the "speaker jumping" that characterizes most of the logic system decoders. One could stand well off to the side with this Tate system decoder and still get positional information from each of the speakers. Sansui has not made any changes recently in their Variomatrix QS decoders, but say there are many more records now becoming available in QS. They were showing an integrated amplifier of a new type, with particular emphasis on phase linearity. It should be on demonstration at the CES. Pioneer was driving their brute Spec 15L monitor speaker (200 watts) with their new M-22 Class-A amplifier. Although only 30 watts per channel, such is the efficiency of the speaker, that it was achieving very clean high power outputs.

Of all the technical papers presented, that by C.K. Hunyar of Phono press, Inc., on various problems of record pressing, was perhaps the most controversial and was even shocking to some. He went into such areas as non-fill and warping, talked about the possibilities of such new record plastics as polystyrene and polypropylene.

Finally he talked about record storage and ... of all things ... condemned the time-honored practice of storing records vertically! He stated that due to "cold flow," records stored in this manner get "out of round" and eventually cause problems. Well! Two other highly important papers were presented by John Hoge and Don Keele, who detailed the application of the Thiele/Small speaker system analysis to horn type systems. Previously, this sort of analysis had only been applied to closed and vented boxes, and it was for his contribution in this area that Dick Small was awarded the Publication Award at this year's Banquet.

"Slewing Induced Distortion and its Effect on Audio Amplifier Performance" was the title of a paper given by Craig Todd, of Dolby Labs, for coauthors Walter Jung and Mark Stevens.

This has been a highly controversial subject over the past couple of years, to say the least, and this paper presents detailed listening and measurement studies of many different op amps. The authors end up by giving us a criterion for negligible slew rate distortion in audio circuits "the circuit, including all possible loading conditions, should possess a slew rate of 0.5 VAS (minimum) to 1 V/┬ÁS (conservative) per peak output volt ... if the slew rate is symmetrical and the input stage has a smooth transfer characteristic." One thing you must say for Mr. Jung and his colleagues, no matter where you stand on this question, they take a hard-nosed, "let's go into the lab and measure" approach.

The banquet speaker, quite appropriately, was Les Paul, that old master of multi-track recording and originator of the overdubbing process. His reminiscing and telling of anecdotes had the capacity audience fascinated.

(Source: Audio magazine, Aug. 1977, Bert Whyte)

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