March 1971 Popular Electronics
Table of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
published October 1954 - April 1985. All copyrights are hereby acknowledged.
This installment of "Stereo Scene" was the 12th in a series run by Popular Electronics magazine in the early 1970s. As mentioned previously, stereo equipment was a big deal in the 1960s and 1970s. Amazingly - or maybe not amazingly - some of the issues of the day have persisted through today's audiophile community. One of the most fervently debated topic is whether audio power amplifiers that use vacuum tubes produce higher quality sound than do transistorized power amplifiers. The pro-tube argument holds that the physical flow of electrons and the ability of metal internal components to vibrate microscopically in response to signals imparts a quality to the output that rigid semiconductors cannot. Many attempts at designing circuits to artificially add such "quality" to transistorized amplifiers have been largely rejected by purists. Even the most modern microprocessor synthesized units often do not pass muster with the aforementioned listeners. I have not seen a published double-blind test to determine whether anyone can repeatedly discern between the two cases. It is hard to imagine there is anyone capable of telling the difference with today's equipment, but it probably was possible when less sophisticated methods were used.
Stereo Scene: Ten Hi-Fi Fallacies
Twelfth in a Monthly Series by J. Gordon Holt
Audiophiles are avid readers. Unfortunately, some of what they read is incorrect-and they misinterpret some that is correct. The result is that part of the generally accepted information about audio is actually misinformation. Here are ten of the most popular misconceptions about hi-fi.
1. Solid-state equipment is better than vacuum tubes.
The inherent superiority of solid state is such an article of faith with most consumers that the term helps to sell everything from food blenders to clothes driers. Solid-state electronics has three clear-cut advantages: the units can be much more compact, they use less electricity and generate less heat, and they do not have the limited lifespan of components using hot-cathode tubes. Outside of that, one can make just as good a case for tubes as for transistors and their relatives.
As noted in Fallacy No.2, sound from a source at the left must be reproduced through the right speaker in order to make it faithful to the way it was originally recorded.
In high-fidelity applications, the advantages of solid-state components are: elimination of the power amplifier's output transformer, potentially lower hum (because of the absence of the hot cathode), and usually better circuit stability due to the ease of obtaining an extremely wide bandwidth. In terms of sound, which is what most people have in mind when they cite the transistor's supposed superiority, there is no clear-cut difference. Generally, solid-state equipment produces cleaner, tighter bass than vacuum tubes can provide - mainly because it is possible to make solid-state power amplifiers with higher damping factors than can be achieved with tubes. But, it has not yet been possible to produce solid-state equipment, especially in the preamp section, that introduces as little audible distortion at high frequencies as you get in some of the very best tube-type components.
As far as durability is concerned, solid-state equipment has not yet completely lived up to its potential. Transistors do not go downhill gradually - as tubes do - but their rate of sudden failure is still higher than that of tubes. Again, this will doubtlessly be remedied; but as of now, the choice between tubes and solid-state components is more a matter of personal preference than one of clear-cut, objective superiority on either side.
2. If a musical instrument that is being reproduced through one stereo speaker is audible through the other, the reproducer has imperfect stereo separation.
This is true only for test and so-called demonstration records where it is clearly stated that only the left or right channel is supposed to be operating. Perfect stereo separation never occurs in nature or in live music because all sounds radiate in all directions from their source. A left-hand instrument's sound will reach the left-hand microphone first and will be loudest at that mike. But the sound continues to travel, get-ting weaker all the time, until it reaches the right-hand mike a fraction of a second later. Thus, the right-channel output from that left-hand instrument will be weaker and very slightly delayed in time, but it will be clearly audible. Were it not there at all, the reproduction of that instrument would be monophonic, from the left speaker only, and all of the sense of stereo spaciousness would be missing.
The reason a reproducing system should have the capability of total stereo separation is to prevent the left-hand sound (which is slightly ahead of the right-hand sound) from leaking through to the right channel and thus apparently narrowing the dimensional spread between the two channels. In fact, though, some stereo test records themselves have imperfect separation where they are supposed to be presenting exclusively left-or right-channel signals. Even the best test records do not have enough separation to leave one channel completely dead while the other is working. As long as the "silent" channel is significantly quieter than the functioning one, the system's overall stereo separation is probably adequate.
3. Since different people hear things differently, high fidelity is more a matter of personal taste than objective reality.
This old saw dies hard! Different people react to different aspects of a complex sound - some concentrate on bass clarity, others on brilliance or overall balance, and still others on high-end richness or detail. And each evaluates reproduced sound on the basis of how well it recreates those aspects of which he is critical. People's hearing acuities differ, also, some having response out to 20,000 Hz or beyond, while others are limited to 6000 Hz or below. But expose any group of people to exactly the same set of air vibrations as were present at a live concert, and their sonic perceptions and hearing limitations will react as though they were all hearing the original sounds.
4. A synchronous drive motor has better speed regulation that a non-synchronous one.
This is a half-truth. Since a synchronous motor is "coupled" to the frequency of the ac supply, its average speed over a given period of time is as accurate as that of an electric clock (which uses a synchronous motor). In order to stay exactly locked on to the ac cycles, though, a synchronous motor must be continually speeding up and slowing down ever so slightly and this reduces its instantaneous speed regulation. Either type of motor requires special design provisions to insure that its particular type of speed variation is held to an absolute minimum for the best reproduction.
5. The better the reproducing system, the worse it makes a worn record sound.
Tape has built-in distortion that disc does not, but tracking distortion due to a poor cartridge can make a disc sound pretty bad.
Manufacturers of second-rate equipment have used this argument for years to explain why their stuff makes surface noise and record breakup so shatteringly offensive, but 'tain't so! Top-notch equipment will reproduce such distortion with embarrassing clarity-making the distortion quite audible. But the more the electrical distortion in the reproducer - the more peaky or tipped-up its high-end response-the more it exaggerates these problems.
Disc surface noise, reproduced through a low-distortion, resonance-free system, sounds rather like raindrops on pavement. Record breakup sounds like an overlay of fuzz. Both are audible, but neither is intolerable. If they are, it is a sign of a poor system rather than a good one.
6. The more power an amplifier has, the better it is.
There is a grain of truth to this, but there is no necessary relation between power and sound quality. It is generally true that low-power amplifiers are not designed to such high standards with regard to distortion as are high-power units. It is also generally true that low-power amplifiers have lower damping factors. Low distortion and a high damping factor make most loudspeakers sound better. But there have been exceptions, and these low-power amplifiers - as long as they are not driven to their overload point - have sounded as good as, if not better than, some very high-power units.
When considering power, it is also necessary to remember that a 1-dB change in volume is barely perceptible, while doubling the amount of available power from an amplifier will account for only a 3-dB increase in maximum available loudness. Thus, a change from 60 to 120 watts per channel actually represents a very small increment of volume capability. The major difference in sound between competing amplifiers is a result of their distortion at output levels of less than 1 watt-a specification that is rarely published, possibly because it provides a valid basis for comparison.
7. The human ear cannot perceive less than such-and-so amount of distortion (or phase shift or frequency response deviation or flutter or what have you).
Statements like this should be interpreted as meaning "My ears cannot perceive less than .... " An untrained listener can sit happily in a shower of "dreadful-fi" and not perceive anything except perhaps a vague feeling of discontent followed by a headache. Some highly critical listeners have shown their ability to detect, in reproduced music, frequency response variations as small as half a dB and distortion levels that were literally too microscopic to measure on currently available equipment. Thus, any flat statement to the effect that this or that is the smallest amount of anything that the ear can perceive must be viewed as highly suspect - if not altogether irrelevant.
8. Consistently dependable FM reception is possible only within line-of-sight distance from the transmitting tower.
This was proven mathematically several times before commercial FM transmissions showed that they did reflect from some atmospheric layer boundaries almost as readily as does AM.
9. Music sounds better on tape.
This subject was discussed in detail in this column not too long ago, but it is still a persistent hi-fi fallacy. In fact, more fidelity is lost through tape duplicating, particularly at high speeds, than is lost when cutting a disc.
And there are typically two more tape-copying steps involved in producing a commercial 4-track tape than in producing the discing master tape. But whereas a commercial tape is inherently worse than a disc to start with, the quality of disc playback is directly related to the quality of the cartridge used to play it back. Tracking distortion from a mediocre cartridge sounds worse than the distortion built into a commercial tape. With a top-notch cartridge, however, the disc can be very nearly as clean as the tape, and then the disc's superiority in terms of transient response, noise, and electrical distortion becomes evident. The only time music sounds undeniably best on tape is when it's from the original master tape, which we cannot, unfortunately, buy at the corner hi-fi shop.
10. Professional audio equipment is the standard by which home equipment is judged.
Manufacturers who toss the word "professional" around in describing their home hi-fi equipment would do well to examine the implications they are making, because in terms of performance specifications. professional equipment is generally inferior to home-type equipment. Disc reproduction, with its attendant tracking-distortion tendencies, puts much more stringent standards on its operation than is done for the professional recording engineers' equipment. Some audiophile tape recorders have responses that extend out to 20,000 Hz at 7 1/2 ips; professional machines will rarely make it to 15,000 at that speed (since they are designed primarily for 15 ips). Most audiophile amplifiers produce less than 0.2% distortion at operating levels below overload; professional disc-cutting amplifiers often generate 0.5 to 1.0% distortion at equivalent levels. Many audiophile speaker systems are good to 35 Hz at the bottom and beyond 15,000 at the top (within 3 dB over most of the range); the typical recording studio monitor speaker cuts off at 50 Hz or higher and 12,000 Hz or lower and the response in between may deviate by as much as 6 dB either way. Equalization accuracy for professional equipment is rarely better than ±1 dB; but it is within ±0.5 dB in some audiophile preamps. Professional turntables and tape machines are considered to be excellent if their wow and flutter is below 0.15%; audiophile units aim for, and often achieve, figures below 0.1%. The main points of superiority in professional equipment are ruggedness and ease of servicing and maintenance-which don't usually show when the shopper is comparing prices of professional and audiophile lines.
Posted June 26, 2019