Men of Hi-Fi--The Perfect FM Tuner (Jan. 1972)

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The following is a partial transcript of Harry Maynard's Men of Hi Fi program, which is now presented each week from 10:00 to 10:55 p.m. on New York City radio station WNYC-FM. Mr. Maynard, Contributing Editor of AUDIO, writer and hi-fi buff, had as his guests for this program Leonard Feldman, another Contributing Editor of AUDIO, and Dick Sequerer, designer of the Marantz 10B.

MAYNARD: Good evening, ladies and gentlemen. Tonight we're going to talk about the ideal FM tuner, and what such a tuner consists of. Dick, I understand that you're designing a tuner which will sell for $1500.00 and be the state of the art. What will be this tuner's fundamental components? When we last talked on this program, you mentioned some of this new tuner's virtues. But just how do you visualize it. I asked you last time whether or not it would be a digital tuner and you said let's leave that to the next program.

SEQUERER: Digital tuning, in and of itself, is just a way to readout the station that you are tuned to. Behind the digital tuning is an extremely stable type of tuning system, so that this is really what makes digital tuning valuable. It's not the numbers that you readout; it's just as easy to read a slide-rule dial, for instance. But you now, without spending a fortune for the type of ganged capacitors that were used, let's say, in the Marantz 10B, can make a device which is extremely stable and very long lived, with modern circuits, no mechanical or moving parts. And, of course, when you do away with moving parts, you make a device which is going to last longer, that's going to be more predictable, and essentially going to give better service. So, in terms of what I'm making now, I frankly will tell you that I haven't made up my mind as to whether to have a digital dial, slide rule dial, or even both.

MAYNARD: How would you vote for this, Len? We're talking about the ideal FM tuner, with cost no question.

FELDMAN: Yes, but it is after all a trade off. In other words, given the option of having a digital readout versus superior performance, I would forego the digits in favor of the performance, because, as Dick points out, you can read a slide rule dial and the stations do identify themselves, even if the dial is off a hairline. So, I'd rather see the money put into performance, rather than readout.

SEQUERER: I don't think I made myself very clear. Actually the digital dial concept, as it is considered by most lay people in the business, really is better performance. It's a more stable system, a more predictable system.

MAYNARD: Why, because it uses crystal controls?

SEQUERER: Yes, that's right.

FELDMAN: In that light, I would prefer it, for its other virtue, not for the fact that I'm getting a nixie tube readout.

SEQUERER: Len is exactly right. The readout is actually a derivative of what the thing is really doing.

MAYNARD: Now, Len, suppose you were talking to Dick and saying, "Here are some of the things I'd like to see, with no reference to cost?" What would you tell him you'd like to see.

FELDMAN: Well, we haven't yet discussed selectivity. I'd like to hear a little bit from Dick on this subject, because it's been a bugaboo with me.

MAYNARD: I have had other people on this program, who have claimed that too much emphasis has been put on sensitivity, too much money has been put into a tuner to give these great sensitivity readings, and it might be better to invest some of the money that has been put into achieving these great sensitivity readings into some other aspect of the tuner.

SEQUERER: If you look at sensitivity in the proper frame of reference, I think you can really understand its importance or unimportance. High fidelity or high quality broadcasting or music-listening type systems need signal-to-noise ratios of almost 60 dB. And that should be the real criterium of the sensitivity.

In other words, where the tuner really has a quieting and a rejection of all noise components and distortion components at the 60 dB level.

FELDMAN: That is why I've said that the IHF's standard is meaningless as it's presently 'written, because you don't know what happens after that 1.8 µV, as you go from there to 5 or 10 µV.

SEQUERER: Let me defend part of the standard, at least so that it can be better understood. All tuners have what is called a quieting slope or characteristic behavior beyond the point that the IHF has determined is the sensitivity measurement. Unfortunately, there are no tuners which are around that follow the ideal or the theoretical quieting curve, and therein lies the problem.

MAYNARD: This would be a very rapid drop-off.

SEQUERER: It's a drop-off, right. Now, this ideal quieting curve, if it were followed along its theoretical performance by all tuners, then the sensitivity figure would be valid at any point, whether it's the IHF or anything else you wanted. However, as Len properly points out, these curves do not follow the ideal because of vagaries and inadequacies in conventional designs.

Therefore, a more meaningful number for the actual listener would be the point at which the quieting had reached 55 or 65 dB. And I'm using that broad a spread on purpose. This includes all hum, noise, and distortion components.

This would then be the point at which you have a usable signal, and that's what we're talking about, a usable signal for high fidelity.

MAYNARD: Well, now, what are you going to put into the tuner? I assume that this is going to be the very latest in design, the state of the art. What's going to be in it that no other tuner's going to have?

SEQUERER: It's going to have a multi-pole Butterworth-type filter, similar to the one that was in the Marantz IOB, but more elaborate. Very frankly, we compromised with the Marantz 10B, and it's strictly a question of money.

MAYNARD: That tuner sold for about $700.00.

SEQUERER: It was $750.00 and it turns out that we probably could have sold it for more, but we did compromise.

MAYNARD: I remember a funny story.

I was standing next to Saul Marantz at a hi-fi show once and a man came up to him and said, "Mr. Marantz, I just bought one of your tuners for $750.00." And Saul turned around to him and said, "And that was less then it cost us to make it."

SEQUERER: Well, that's not altogether true, but it depends on when he bought it. If he bought one of the very first, I would suggest that it was true. It was a very expensive undertaking for a small company. We did learn a great deal in the process. It doesn't seem that anyone else picked up where we left off.

MAYNARD: What have we learned since the Marantz 10B was designed?

SEQUERER: I don't think we've learned anything, but I'm prejudiced.

MAYNARD: If you're going to go beyond the Marantz 10B, how do you do it?

SEQUERER: We're going to lower the distortion by a slug, as we say in the business. You can't lower the distortion at mid-band over the 10B, because that was probably close to theoretical but you can lower it at 15KHz. We're going to improve the 15 KHz separation. We're going to improve the selectivity. And we're going to make probably the largest improvement in the AM rejection. We're looking for something that can reject 80 percent AM.

MAYNARD: Would you agree that this is a step in the right direction, Len?

FELDMAN: Absolutely!

MAYNARD: What kind of a standard figure are you hoping to achieve in this AM rejection area, as compared with the way it's given now?

SEQUERER: Well, this becomes complicated because now we have to talk about how to measure it, and how to generate AM that is similar to the envelope modulation of multipath.

MAYNARD: Would you explain envelope modulation to our listeners?

SEQUERER: Everyone is familiar with the situation of listening to FM and having a plane fly over and getting flutter.

This flutter is amplitude modulation, fundamentally, of the FM signal, that is, of the wanted signal by the unwanted signal. This is called envelope modulation.

MAYNARD: Len, would you sum this up for our listeners?

FELDMAN: What Dick is saying is that the signal which started out as all FM becomes, in fact, a partly AM signal. That's oversimplifying, but what you want is pure FM and what you're given is-unfortunately-a combination of FM and AM modulation, which leads to the distortion products we've been talking about.

SEQUERER: Let me say one other thing, for the more technically minded in the audience. All of the information necessary to FM is contained in what we call the zero axis crossings. Everything else is extraneous. If I add to this AM, and the set still cannot process the AM, I have not affected a thing.

Unfortunately, if the set will demodulate the AM components, they add to the information that was on the zero axis and form serious distortion. And to put this more practical terms, these components are all audible. The tuner we are envisioning will sound better to the average listener because of its significantly better AM rejection.

MAYNARD: Just the way the Marantz 10B sounded better, although on some laboratory specs, sensitivity figures for example, the 10B was not extraordinary, was it?

SEQUERER: Those specs were no better than anybody else's.

MAYNARD: Why did the Marantz 10B sound better as it seems to me it often did?

SEQUERER: For one thing, the selectivity and the shape of the i.f. passband as it was achieved then, was probably better than anything else that had been done before. It led, for one thing, to a phase linearity over the i.f. system, which was important for mono and particularly for stereo.

MAYNARD: And this is going to be terribly important for matrixing systems, where you have a lot of out-of-phase information, isn't it?

SEQUERER: It could enter the picture, yes, providing that matrixing in fact does become the system of FM four-channel broadcasting.

MAYNARD: At least we know-you and I and a lot of so-called experts-have agreed that for at least the next three or four years, if we're going to get four-channel via FM radio without any change in FCC regulations, we're going to have to listen to it via some matrixing system. Dick, what are you going to do about four-channel? I hope you're going to have a design whereby, no matter what system is adopted, Dorren or whatever, one would slip in a simple IC and there won't be any obsolescence in this $1500 "ideal" tuner. Is that correct?

SEQUERER: This is correct. I certainly hope that we're not going to have any obsolescence in this tuner.

MAYNARD: This doesn't constitute any problems, do you feel, Len?

FELDMAN: No more than the problem we faced when stereo was just around the corner and everybody was providing detector outputs or building in a facility for plug-in modules.

SEQUERER: More than that, I think if the system is truly phase linear in terms of its FM capability, and it has the low distortion, and the low AM response, and the great stability that we're talking about, it can process anything over the allocated band. And that's the whole key.

There are many tuners on the market which will not be able to precess anything.

MAYNARD: Would you agree with that, Len?

FELDMAN: Yes. I have just one question.

I'm sure you're familiar, Dick, with the Dorren proposal and that it may involve extension of modulation out to perhaps 100 KHz. What will happen with your tuner?

SEQUERER: Basically in my design work, I do not measure harmonic distortion with de-emphasis in the system. I make a system which will indeed go to 100 KHz, in terms of its audio modulation.

MAYNARD: Dick, will you sum up the basic points about your $1500 "ideal" tuner?

SEQUERER: I think the most important thing is that this tuner will be ultra-stable. It is an instrument, and it will give many, many years of predictable performance. That's about all you can say.

MAYNARD: Entirely solid state?

SEQUERER: Mostly integrated circuits.

FELDMAN: What is the projected timetable, Dick?

SEQUERER: I am estimating deliveries of these tuners to selected people, since this is a very limited production thing-sort of a hand-crafted Rolls Royce, if you will-sometime in March.

MAYNARD: I certainly want to be on the list to receive one of these tuners. What do you feel the market is?

SEQUERER: Well, I think there is a market.

FELDMAN: I agree. In fact, we were talking about this earlier. I believe that with a superior product such as this, that if anything Dick is going to find that his edition is too limited, because once the word gets out that such a product exists, I have the feeling that he'll have to increase his production plans.

MAYNARD: What about the market from FM radio stations? Do you see that?

FELDMAN: There's a natural market right now, even before you talk about the consumer.

MAYNARD: Well, the Marantz 10B is selling right now-there's no depreciation on 10B-you have to pay $750 right now to get one.

SEQUERER: They don't make them anymore.

MAYNARD: Right; that's what I'm pointing out.

SEQUERER: I think that you'd be hard pressed to find one. I know I was when I had to get one recently.

MAYNARD: Dick, I want to thank you for giving us some of the very interesting history of the Marantz l0B and for telling us something about your new design. Len, thank you too, for being on the program and for your always interesting comments on FM tuners and broadcasting. Good night.

=============

(Audio magazine, Jan. 1972)

Also see:

How to evaluate FM stereo tuner performance (Jan. 1972)

New Specs for the New Tuners (Jan. 1973)

AM Stereo: An FCC Fiasco (July 1982)

FM Fidelity: Is The Promise Lost? (March 1985)

The Problem with FM (March 1985)

The New Receivers (Jan. 1973)

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