William Z. Johnson of Audio Research: High Definition Page 2
Johnson: I have said that on more than one occasion. Every measurement that we're aware of falls into the realm of what we call repetitive, or static, measurement. In the real world, the simplest musical signal has component signals 1/10000 the size of some of the other signals present, and at many, many frequencies at once. It simply defies the abilities of static circuitry measurement.
Harley: Have you found areas of technical performance that correlate with certain sonic qualities?
Johnson: Our engineering team has found some correlations. As you probably know, we have half a dozen engineers at Audio Research. All of them are reasonably skilled listening people as well. They will pursue a given thing—harmonic distortion or whatever—and as they make improvements in these areas, they hear the difference.
Now, I have a slightly different philosophy that is part of what I call "the gnat and the camel" principle: Let's say we reduce the harmonic distortion content by a factor of two, and that it helps the sound a little bit. It may sound a tiny bit better. Certainly it will if we haven't upset the dynamic stability of the circuitry. But what if we have a camel charging around in this circuitry that really ought to be excised? We weeded out a couple of gnats, and we've left a camel marching on through.
What we really need to do is address the behavior of electronic circuitry under dynamic conditions and not worry whether it has 0.001% distortion or 0.002%. That really isn't the issue. You're talking one part in ten thousand. I don't think anyone has ever built an electronic device that was that good under dynamic conditions.
Harley: Do you remember the first time you heard a solid-state amplifier?
Johnson: Yes. It was back in the late '50s, as I recall. I think it was a brand called Brown or Browning. It was atrocious. It was so bad, I couldn't believe it. And it didn't measure very well either, by the way, but it sounded really, really awful. [laughs]
Harley: Virtually everyone today recognizes how bad the first solid-state amplifiers sounded. Given that they sounded worse than tubed amplifiers, why did every audio company—Fisher, Marantz, McIntosh, Scott—abandon tubes in favor of transistors?
Johnson: I suppose the primary reason would have been serviceability, or lack of service requirements. Back in those days we had hundreds and hundreds of types of vacuum tubes, many of which were really pretty marginal devices.
One thing that Audio Research has never done over the years is involve ourselves with esoteric types of vacuum tubes. We have stuck with very, very common audio types: 6550s, KT88s, 6L6es, 12AX7s, 6FQ7s.
Harley: Does that mean Audio Research isn't going to make single-ended amplifiers with a 300B direct-heated triode?
Johnson: Right. We're not going to do that, no matter what the glories of a 300B might be. The cost of them is prohibitive, and the availability is not great—although I understand that Richardson is actually making the tubes. But that isn't for us. We'll stick with our premium-grade 6550s.
Harley: There seems to be a kind of fashion in amplifiers—certain designs suddenly become popular for a while.
Johnson: They come and go with regularity. Unfortunately, most of those products are built by very, very small companies who, no matter how well-intentioned they may be, find it very difficult to really support the product once it's out there. Which I think is a valid consideration for a person spending the kind of money that audio products cost today.
Harley: What are the prospects for continued availability of high-quality tubes?
Johnson: I think they're good. Last June the Russians started delivering premium-grade 6550s as well as several other audio types. And I don't know this for sure, but I'm assuming it's conversion of their military capability to civilian use. I believe that it's reasonably common knowledge that their vacuum-tube technology was well ahead of ours. They evidently believe that vacuum tubes are impervious to high doses of radiation, which evidently some semiconductors are not. So, from what I'm told, their aircraft communications equipment was designed to still work during a nuclear blitz.
Harley: I've heard that MiG fighters still have tubes in their avionics.
Johnson: I wouldn't doubt it. At any rate, whatever the reason, the new Russian tubes are excellent. With the Chinese 6550s and KT88s, we had a high percentage of tubes that would arc and not last the several thousand hours they ought to; but these tubes are excellent and just don't arc. They sound better as well.
Harley: Is this the same factory—Sovtek—that makes the excellent 6922?
Johnson: As far as I know, it is. But we don't deal directly with the factory. We deal with an importer. So it's hard to know exactly what goes on.
They also make tubes like the 5AR4, the GZ34 rectifier tube. Some audiophiles believe you shouldn't even use semiconductors in the power supply. And of course, ultimately, they are right. If the cost is absolutely no object, that would be the way to do it.
Harley: Audio Research has always used extensive power supplies. How important is the power supply to good sound?
Johnson: Its importance simply can't be stressed enough. No matter how good the audio circuitry is, no matter how well-balanced, no matter how dynamically stable it's capable of being, if you don't have rock-solid power supplies that are totally decoupled one from another, you've done it all in vain. You probably have noticed, Bob, that the sophistication of our power supplies has increased over the years, whereas the audio circuity has really not changed that much. Indeed, it's actually become simpler.
Harley: It's easy to think of the voltage rails just sitting there outside the signal path.
Johnson: It's not true, though, is it?
Harley: That's right. Because the power supply is tied to the plate, anything that happens to the power supply happens to the audio signal.
Johnson: The power supply is actually in series with the audio signal, whether we like it or not.
Several things are involved here. One would be, obviously, its stability—stability to present a very low impedance and maintain whatever voltage it's supposed to, regardless of the instantaneous current demands. Then the other would be the coloration of that circuitry. In other words, what does that processing do to the voltage that's supplied on a dynamic basis? I don't think we have all the answers on that yet. I think that there's a great deal more to be learned.
Harley: When digital audio first appeared, it seemed to be a step forward, providing apparently better measured performance and greater convenience, when musically it was a step back—although now that digital's been widely available for ten years, it seems to be getting quite a bit better. Do you see a parallel between the introduction of digital audio ten years ago with the introduction of transistor amplifiers in the 1960s?
Johnson: Actually, it seems to me that almost everything we've ever done in audio has initially been a step backward. You're probably too young to remember when stereo came along. The initial stereo cartridges were terrible, and we despaired of good sound. This was back in the '50s. But that, of course, changed, and today we have some utterly remarkable cartridges and arms.
Technology has gone way beyond anything we could have possibly dreamed of 40 years ago. I think that's certainly true of solid-state amplifiers, and it's certainly been true of digital storage and retrieval for audio. Ten years ago my opinion of digital was, as you know, pretty low. Today, it's very hopeful. I'm really hopeful that high-end audio won't have to disappear from the scene because of the lack of source material. I have reason to hope, and believe, that the day will come when digital will be, if not as good as ultimate analog, certainly better than analog in the past.
Harley: I know that the company philosophy of Audio Research is to use the best device for a particular application...
Johnson: Regardless of what it is. We're not married to vacuum tubes, if that's what you're saying. Absolutely right.
Harley: It seems as though Audio Research started out committed to vacuum tubes, then there was a shift toward solid-state. And now all the reference products...
Johnson: ...are vacuum-tube again.