Thanks for the Memories
Dear Sir:
I read with some surprise and delight your review of the MR-78 tuner which I designed (with the MR-77) while at the McIntosh Laboratory during the period from 1968 to 1974. The history of this tuner is a long and interesting story.
Things began back in the late 40s and early 50s when I lived under the shadow of Major Armstrong's old FM station in Alpine, N.J. I listened to it incessantly on an old Dumont TV set, and probably my love of music had its beginnings here.
After finishing high school and with my interest in FM strengthened by my interest in Armstrong's work, I began studies in Electrical Engineering at Manhattan College. By 1958 I began to become aware of the problems in FM reception and started to think about solutions.
--ABOVE: Harold Colt (in red shirt) and Dirk Roos of McIntosh listening to
WGXR, New York, on the MR-78 No. 3.
In graduate school I began to get some concrete ideas. Here the Rimo (phase linear) i.f. filter concept was born. Research work on this filter concept began during 1962-63, ending with a Master's thesis (The Rimo Filter) at the New Jersey Institute of Technology (then the Newark College of Engineering) in June, 1965. April, 1965 saw the world's first Rimo-filter FM tuner, a vacuum tube model which I still have.
Stereo IM distortion was the bane of all FM tuners at that time, and my discovery that most of this distortion came from the i.f. detector systems then in use was significant. Measurements on currently available tuners, using a two-tone close frequency method, disclosed values of stereo IM as high as 15 percent, even though he same tuners had 1 kHz harmonic distortion of 1 percent or less. No wonder FM sounded so fuzzy! In 1966 I began post-master's research and study at N.J.I.T. where I took another Master's degree in Computing Science, and used this knowledge later at McIntosh to develop their computer-designed Rimo filers for the MR-77 and 78.
During 1968 I got the idea for that device that was later to become McIntosh's linear phase discriminator (U.S. Patent 3,646,461), and a crude working model was built at home during the summer of '68.
McIntosh knew about my work (I mailed them a resume in 1964), and Sid Corderman, their chief engineer, was so persistent in his appeals to get me to come and work there that I finally gave in and went there in the Fall of 1968 as a senior design engineer.
During the winter of 68-69 I worked on the tuner model that was to become the MR-77, and we had a working model ready for demonstration by the following spring. It was clearly and easily better sounding than anything else in the lab. It measured less than 0.1 percent IM distortion, and most of that in the final audio stage. This was exciting-as then the highly regarded Marantz 10B had about 1 percent IM in the same test.
The MR-77 entered production in 1970, and I published a paper on it in the November 1970 IEEE BTR Transactions. This paper brought world-wide correspondence-I received letters from all five continents. We see today, in retrospect, the legacy of the MR 77-78 in the new crop of very fine Japanese tuners, such as the Sansui and Kenwood.
McIntosh had a favorite tuner test location at the home of Harold Colt in Farmington, Conn. Here, Mr. Colt had tried to receive WNYC 93.9, WQXR 96.3, and WNCN 104.3 from New York City, 90 miles away. All three of these stations are adjacent channel to three strong local stations.
WTIC 96.5 is just across the highway.
Colt owned a Marantz 10B which would just barely get WQXR, if you detuned it a little away from WTIC. It would not receive WNYC or WNCN well, as there were strong adjacent channel signals on both sides of the New York City stations.
Apparently all the FM engineers bring their best toys to Colt's, and he delights in showing them all how bad their tuners are. Almost all tuners degenerate into a mass of spurious signals and horrible distortion-as the helpless r.f. front end is pounded by the 10 or 15 quarter-volt signals from the Hartford transmitters surrounding Colt's home.
It is a great credit to Richard Sequerra's 10B that it worked at least tolerably well at Colt's. It was, and still is, a landmark design.
Well, into this mess I charged with my MR-77. It was a dismal failure.
Spurious rejection was O.K. and it sounded great, but it would not pull in the distant signals Colt wanted at all. He threw me out and said, "Come back with something that works." I'm not intimidated by failure. I was mad, but now bowed. On the long drive back to Binghamton I dreamed up the MR-78. I reported the failure to Sid Corderman and went into the lab to build the MR-78.
After a few months activity I finished the first model-the "Kluge." MR-78 number zero (like Bruckner I dared not give this thing a number) was a real bomb-two old MR-71s and an MR-77 all hooked in series.
I brought this mess to Colt's, and after he recovered from his laughing fit-imagine a pile of chrome chassis, tubes, wires, and transistor PC boards stuck out in all directions with loose cables dangling all over-we hooked it up. Picture his surprise, and mine too, when this contraption pulled in clear signals from WNYC, WQXR, and WNCN. We were dancing all over his listening room like excited kids. Nick Perfito of the Stereo Shop in Hartford was also present, looking and listening in utter disbelief. We all went out to dinner to celebrate, and then went back to McIntosh to attempt to cram all of this stuff into one chassis.
During 1971 and 1972 I made many trips to Colt's refining prototype after prototype until the MR-78 worked as well as the laws of physics allowed.
Actually the MR-78 suffered a little due to the laws of commonsense economics. My prototype had 100 dB adjacent-channel selectivity instead of 55 dB, and much lower distortion in super-narrow, but the 100 dB filter was too expensive. It also had, in one version, a complex TTL discrete PLL stereo decoder which gave better separation --50 dB up to 15 kHz-and lower distortion 0.02 percent--but it was too complex and expensive. It also had a dynamic stereo filter (patent pending) which operated on a noisy FM stereo signal in a manner similar to the operation of the Burwen noise reduction system on a noisy record. These ideas were incorporated into a later super digital tuner prototype not considered for production.
I left McIntosh at the end of 1973 when my tuner work was finished.
Richard Modafferi Vestal, N.Y.
Audio Specs & Measurement
Dear Sir:
Although we were flattered and generally pleased at the treatment accorded our Technics SA-5760 stereo receiver in your January, 1977, issue of Audio ("Battle of the Titans"), the report did leave us with some questions and reservations. Although our doubts may not be serious, they do involve problems that are of concern to your readers, as well as to us as manufacturers. For one thing, some oversights and misunderstandings in the review, however inadvertent, are subject to reader misinterpretation. For another thing, the report re-awakened certain long standing doubts concerning the entire matter of "specsmanship" and the approach to equipment evaluation, its philosophy, and the continuing problem of reaching subjective/objective conclusions of genuine value. Let's begin with one of the simpler points.
-------Audio, Jan. '77
Published vs. measured specifications: There is no industry-wide standard, official or unofficial, from which a manufacturer can determine his base point for publishing specifications. At one extreme, he could publish the very best figures optimized in the laboratory prototype but never actually achieved in any production sample. At the other extreme, he could follow the very conservative practice of publishing specifications below worst case production samples, thus guaranteeing that every purchaser will obtain performance better than he buys. Obviously the latter suffers a disadvantage in a direct comparison against the former.
Fortunately both manufacturers involved in your two receiver evaluation are reputable enough to frown upon bending the truth in the first mentioned manner. However, we think you would have served your readers better by printing actually measured readings in chart form as you did published specifications, which dominate the second spread of the article. The actual readings to which you refer do indeed appear scattered throughout the article, but they lose their perspective and impact when presented in this diffuse way.
Expanded vs. normal scaling: Here is another illustration of the fact that the style of data presentation can have at least as much impact as the basic data itself. When relatively small differences are presented graphically, they tend to vanish altogether with normal scaling. There is thus a temptation to use expanded scaling to make the differences obvious. Unfortunately, this can have the converse effect of exaggerating their significance. In the case of two of the three distortion charts shown (Figs. 5 and 6), this has tended to work to the disadvantage of the SA-5760, whereas normal scaling was used in other graphs we would have preferred to see in expanded form! This may seem like nitpicking, but a simple solution could have avoided the problem. For resolving such dilemmas in the future, may we suggest that two graphs be shown, one with normal and one with expanded scaling? That should keep the matter in perspective. (Editor's Note: Figs. 5 and 6 presented measured performance of the two receiver's amplifier sections, while the other graph of distortion, Fig. 4, showed mono THD vs. frequency for the tuner sections. E.P.)
Specsmanship vs. realistic performance: In "New Tests for Preamplifiers" in your February issue, Tomlinson Holman has some very perceptive things to say about the what, why, and how of equipment testing that pertain broadly to all sound-reproducing equipment, not just preamplifiers. He speaks of "audible differences among designs that had nearly identical measurements on conventional tests" although he acknowledges a role for conventional electrical testing as the "...easiest to replicate and communicate since the hardware produces numbers.... Of course, such measurements form the basis of published specifications and test reports." But he reminds us that "ultimately the object of all measurement must be considered to be the assessment of the subjective quality of the device under test...the usual test signals employed do not adequately represent the demands of program material...." His remarks are particularly relevant with respect to conventional approaches to FM circuit evaluation.
Many of us put the cart before the horse, sanctifying certain specifications to the point that, in the hands of some engineers, audible performance is actually sacrificed for the sake of a handsome looking number. For example, such parameters as sensitivity, selectivity, and the rejection of unwanted signals can be numerically improved at the expense of bandwidth, which will have effects that are audible though less than laudable. But what is high fidelity about, after all? Most of our electrical tests use steady-state, single-frequency signals.
This is true of THD testing, and even of swept response testing, in which a single frequency is applied at a time.
The use of two frequencies at the same time in IM testing is about as bold as most evaluators get.
True musical waveforms are complex, constantly-changing clusters of many different frequencies occurring simultaneously, with intricate patterns based on their phase and amplitude relationships. Thus, we at Technics have chosen to use the square wave, which is, after all, a cluster of a large number of related but distinct frequencies with very specific amplitude and phase relationships, to depict overall musical performance of the FM section of the SA-5760. Offhand, we can remember no other FM receiver or separate tuner for which this stringent test is recommended. We invite it.
Another practical matter that is completely overwhelmed by conventional, uninspired "specsmanship" is that of overmodulation at the FM transmitter. It is a notorious fact that, at any given moment, a large percentage of FM broadcasters are modulating beyond the FCC-defined limits for the sake of putting out a "fatter" signal to a larger listening audience. On conventionally designed receiver and tuner circuits, nothing is done about this, and the result is distortion. But something can be done about it, like using a wideband detector to reproduce such over-modulated signals cleanly, as is the case of the SA-5760. In the SA-5760, we make no apologies for the commendable performance levels we have achieved with respect to such pro forma specifications as those relating to sensitivity, selectivity or unwanted-signal rejection.
But, rather than force the receiver to do electrically what a reasonably good antenna can do better without compromising waveform-reproduction integrity, we have opted for the best and purest sound we can get. Remember when that's what high fidelity was all about? Regrettably there is no room in the test procedures used by Audio's evaluators for acknowledging such meaningful achievements.
--Sid Silver, Merchandising Coordinator, Technics by Panasonic Secaucus, N.J.
Automatic Distortion
Dear Sir:
In response to Mr. Bert Whyte's "Behind the Scenes" column in the January, 1977, issue of Audio, I would like to suggest some answers.
I must agree there are a lot of bad records being produced in this country. I believe we can attribute a great deal of this to automation. I am not saying automation cannot produce a good product, but its basic meaning is fast production which becomes some sort of a disease and does compromise quality.
As for the terminology "concrete," today our materials are much better than 15 or 20 years ago. Twenty years ago we had three basic materials, virgin vinyl, extended vinyl, and filled vinyl. To the best of my knowledge, the great majority of plants are now using only virgin vinyl materials.
With due respect to record company engineers who claim that shrink wrapping warps records, I wonder if they have overlooked the fact that many of the protective jackets are now being made of cheaper board, which has a tendency to bow when shrink-wrapped. When you combine this with the fact that many jackets are bowed or warped to start with, you have two strikes against getting a flat record.
I have never heard the terms "symphonic" or "pop" cycles used, nor have any of our customers. A rock record (so-called pop cycle) can be a 33-minute side and have just as many moulding problems as a classical record (so-called symphonic cycle) which has a 21-minute side.
Some food for thought... the Westminster Lab series played on today's sophisticated equipment might not prove to be the great listening experience one assumes.
In the so-called "good old days" we did not have groove guard which introduces a lot of problems...swishes, thumps, and worst of all skipping and skidding. One of the reasons for some of the quieter European pressings is the fact that many of their pressings are non-groove guard, eliminating stress at the lead-in and run-in of the record which is caused by the groove guard. A noisy beginning on any record will always leave a bad taste in anyone's ear.
Pressing plants are a part, but only a part of the problem. To make a well pressed record requires good control of many complex procedures: cutting, plating, labels, sleeves, jackets, vinyl, molding, wrapping, packing, and shipping.
--Frank P. Gaudenzi, Plant Manager Windsor Records, Inc., Paterson, N.J.
Record Degradation
Dear Sir:
I am writing concerning Bert Whyte's "Behind the Scenes" in the January issue of Audio as he talks about the bad pieces of plastic on the shelves of record stores. I say, "Good article!!" Keep on mentioning the bad quality of records. From my own experience about eight out of ten records on the market are either warped, or snap, crackle, and pop when I play them. The money they want for these records is ridiculous.
You can own a $5,000 component system and it's not worth a dime if the disc is all warped and cracked up.
Why have good equipment? At times I'm tempted to sell my system for a good price. Maybe, someday there will be a turntable or device that will tone down the bad records so they don't sound like breakfast cereal...Snap! Crackle! and Pop!
Robert H. Lacher, Pittsburgh, Pa.
Sounds Remembered
Dear Sir:
After reading the March, 1977, issue of Audio I was greatly enthralled with the story by John Hilliard on "Movie Sound Reproduction." This was wonderful reading for me because during those very times I was involved in sound movies. First, it was the electrical reproduction of recordings, instead of the orchestra and piano player in the pit.
My home town of Schoharie, N.Y., had since 1916 put on free open air movies for 15 nights, one each week from Memorial Day to Labor Day.
They were held on the Main Street in front of the courthouse, and thousands would come to town on these Thursday evenings, bring their own chairs, or if they had an "open-top" automobile...head that towards the curb facing the screen and sit in "luxury" to watch the silent movies. This continued each year and soon "talkies" came into being.
Was Schoharie's famous open-air drive-in theater now doomed? No, it wasn't! I am proud to have had the opportunity to develop what has been classed as the world's first open-air talking picture theater. Right at the moment I cannot give you the exact dates, as several years ago I lost all my photos, newspaper stories, and accompanying dates in a fire. However, it was in the early 1930s. "Motion Picture Herald" carried a story on it as did their supplement, "Better Theatres." I purchased a sound head from Karl Weber, of the Weber Machine Corp. of Rochester, N.Y., and installed it on a Powers 6A projector, built an amplifier, and hooked up a couple of speakers. I had been in the sound business since 1927, so this was just up my alley. We had open-air talkies! A few years later when "Motion Picture Herald" ran a story on the opening of the Camden, N.J., open air theatre which they tried to claim was the first, a lot of fanfare was given to it. A letter to this trade publication reminded them of the previous article which they had published a few years earlier, and so we regained our fame as having the first open-air talkies.
I didn't mean to ramble on so, but Mr. Hilliard's story was so great that I couldn't help but write to you and express my appreciation for the story which brought back many fond memories of those days "when the screen began to talk."
And many thanks for a fine publication like Audio Magazine.
Edward Scribner, Schoharie, N.Y.
Microphone Test Addenda
Dear Sir: I hasten to add credit where it is due to my article "The Compleat Microphone Evaluation" which appeared in the April, 1977, issue of Audio.
I wrote the description of the precision spherical sound source from memory. At that time I asked John Volkmann of RCA Laboratories for more information on the source. It took some time for him to locate this information and obtain company approval to send it to me. Alas, it arrived too late to stop the presses. I would like to thank him for his efforts.
I find that Volkmann, as department supervisor in 1948, worked with Witchey in the development of the source. This credit should be added to the article.
Jon Sank, Contributing Editor, Haddonfield, N.J.
(Source: Audio magazine, May 1977; )
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