Turntables

Turntable History

 

Fairchild Turntables Fairchild Tables

Grado Cartridge

In reproducing a phonograph record, the aim is to take out of the groove exactly the intelligence that was pressed into them. And the wiggles in the groove are meaningless in themselves. They have to induce exactly the right physical motion in a stylus before they make sense---which means that they must move under the stylus at the right speed and that the stylus itself must track the groove accurately, wigwagging as the wiggles demand. A turntable spins the grooves; a tone arm holds pickup and stylus in place. What we want from the turntable sounds simple, but it isn't. In the first place, there are three speeds: 78.26 rpm for the old-fashioned standard shellac records, 45 rpm for the little seven-inchers with the big center holes, and 331/3 rpm for long-playing discs. The speed must be exact in every case. If the turntable is slow, the pitch drops; if fast, the pitch rises.

Moreover, the speed must be exact at every instant of playing. A turntable that alternately slows down and speeds up will ruin musical enjoyment even though its average in each rotation is an exact 78.26, 45 or 33 1/3 rpm. The phenomenon produced is called "wow," a very expressive word denoting the alternating rise and fall of musical pitch which results from fluctuations in turntable speed. When these fluctuations are rapid, the term is "flutter."

HOW TURNTABLES WORK

The ordinary shaded-pole motor, which runs your electric drill or power saw, is no good for such precision work because any variation in the voltage of your house current will change its speed. Most turntables use a specially designed "induction" motor which is fairly stable in feed, though extreme changes in line voltage may disturb it (look for a tag stating its requirements: "95-130 volts" means disaster-proof). Even this isn't absolutely steady. The 60-cycle alternation of AC electric supply, however, is invariable (an electric clock practically never goes wrong), and thus a "synchronous" motor, which decides its speed by the frequency of alternating current, can keep a constant rpm unless a complete power failure occurs. It also eliminated the dangers of turntable rumble and extruded "hum." Getting this constant speed of the motor up to the turntable (in three different varieties) takes considerable ingenuity. Today's best and most expensive turntables use one of five methods to translate motor speed into turntable rotation.

Turntable Drive Mechanisms

On the Rek-O-Kut and the Garrard the power gets to the turntable by means of a "rim drive"; that is, the final agent is a bard-rubber drive wheel which locks into position between the motor's axle spindle and the inside rim of the turntable. This is the most common way of making a turntable spin. Usually the spindle, the upward-protruding end of the motor shaft, is cut in "steps" to three different diameters. The speed-control knob locks the wheel against one of the three steps. When the wheel locks against the part of the shaft with the greatest diameter, the turntable spins most swiftly, and so on. A conical or tapered spindle may be used to give continuously variable speed---anywhere from 15, say, to 100 revolutions per minute. There are several variations on this procedure. Rek-O-Kut, for example, locks wheels of different diameter against a one-size spindle; the new Weathers uses a ceramic disc instead of a rubber drive wheel, and attaches the disc directly to the motor shaft. The D & R applies to the drive wheel to the outer rather than the inner rim of the turntable. On the Scott the turntable drive is direct: that is, the drive shaft of the motor locks into one of three gears on another drive shaft, which in turn is geared to the center of the turntable. The Components Corporation uses a linen belt which fits directly onto the drive shaft (at one of three diameters) and then fits around the circumference of the turntable. The Fairchild runs the belt inside, to a cast-iron flywheel below the table. There are arguments for and against each of these methods. The Components Corporation gets the motor farthest from the turntable and the pickup, thus minimizing the danger of noise from the motor. For the same reason, though, it is rather bulky and unattractive, and requires the most elaborate mounting. Direct drive uses metal parts only and can thus be machined to the closest tolerances. It also lasts longest, at least in theory---but not necessarily in practice. And when something goes wrong, the repair may be expensive. Rim drive requires occasional replacement of the rubber-tired idler wheels and drive spindle-tops. It is, however, the easiest to repair.

Various Turntables

TONE ARMS

A turntable does not become a record player until you add a tone arm, which must be separately purchased and mounted. Like the custom turntable, the separate tone arm solves a multitude of problems. You will recall that the cutting stylus rides across the record on a bar from circumference to spindle, following a true radial path always at right angles to the line of motion of the groove. For accurate reproduction, the playback cartridge, too, should always point straight down the groove, so to speak. But we bold the playback stylus in a tone arm, which pivots, making a curved rather than a straight track across the record. In a really bad tone arm, the playback stylus will sometimes be off as much as 10 or 15 degrees. The message of the wiggles is distorted, and the record wears unevenly and more quickly, as does the stylus itself. This is known as "tracking error."

TRACKING ERROR

In the old days, before the deep thinkers got at this business, the solution to tracking error was simply to make the arm longer. A short arm tracks a small circle, presenting a more steeply curved arc as it crosses the record; a long arm makes a shallow arc with a closer resemblance to the desired straight line. Then it was discovered that curving the bead of a fairly short arm, by correct degree, would substantially reduce the average tracking error over the course of a whole record (Angling the pickup in a straight arm gives the same geometric effect).

Although many hi-fi authorities will still insist on the long arm (which requires a very large installation space), a recent tracking-error test came up with the tiny Ferranti arm as the most accurate tracker in the business. The new Garrard arm may be adjusted to any desired length from 10 to 16 inches, which allows complete flexibility of installation. New ideas include arms which simply hang over the disc; a pickup bug (similar to the bug which holds the cutting stylus) running over the record; and the B-J, a British import, which is really two arms attached to a single pickup and swinging separately so that the pickup is always aligned with the groove.

Various Turntables

TRACKING WEIGHT

The vertical pressure of the playback stylus on the record will be a key factor in both stylus and record wear, and the various tone arms employ various ways to get the right "tracking weight." Some use springs at the rear end of the arm. In others the nonbusiness end will extend some distance beyond the pivot, counterbalancing the weight of the rest of the arm and the pickup. This means bigger installation space. The GE Baton arm features a head,attached to the arm itself by a swivel. Most pickups are made to respond best at a tracking weight of four to eight grams, but the pickups themselves are not all the same weight. The viscous-damped Gray 108-C adjusts any pickup to four or six grams of vertical pressure. The GE balancing bar is calibrated and has a moving screw, giving a choice of tracking weights. Both the spring and the counterbalanced arms often have some mechanism by which the tracking weight of the stylus can be increased or decreased. But none of these measurements will do you much good unless you know the actual weight of the pickup you are using and the weight of the pickup for which this particular arm was designed. You can measure the final vertical pressure of any arm and pickup on any one of a dozen gauges---preferably the Audak ($4), which is most accurate because it is a balance, with replaceable weights, and has no springs. But even an accurate measurement (which should be made, with all arms) does not tell you what will happen on warped records.

Tonearm Tracking

TONEARMS FOR WARPED RECORDS

If many of your records are warped, certain precautions are indicated. In general, the lower the mass of the arm-and-cartridge assembly which has to take the jouncing from a warped disc, the better the results. The GE Baton arm, the Pickering, the Garrard, the Shure and the Weathers arms are engineered to operate well on a warped disc.

Various Tonearms

Various Tonearms

MATCHING ARM TO PICKUP

The functioning of the pickup, however, is more important than the perfection of the arm. Most pickups operate best in arms made by the same manufacturer. In some cases no other arm will do. The Ferranti, Leak, Shure and Weathers pickups will hardly work at all in another maker's arm. With the GE and Fairchild pickups you have a choice of arms, because these are the most popular in the business and every arm is more or less prepared to bold them. The Rek-O-Kut arm is designed to hold almost any pickup.

MANUAL PLAYERS

The cheapest recommended turntable and the cheapest separate arm will cost you, between them, about $80. For half this money you can buy the German-made Miraphon record player, with an excellent four-pole motor, a solid turntable and a very decent arm. It will not track quite so well as the separate arms, and the turntable is not so well weighted for the avoidance of wow and flutter. But you'll have to be pretty good to catch the difference, and the price is definitely right.

CHANGERS

If you have a large quantity of 78-rpm or 45-rpm records, you will probably want a record changer. Getting up to change records every four to six minutes is unquestionably a nuisance, and it diminishes the pleasure of a phonograph. Since the argument for high fidelity is an increase in pleasure, there is no practical sense to the purist argument which rules out the record changer from all high-fidelity installations.

There may be no practical sense to it, but there are sound theoretical reasons behind it, which can be summarized. The motor of a turntable has one job, turning the table. The motor of a changer must also work, through intricate gears, to lift and move a tone arm out of harm's way and to push records one on top of the other. It does its basic job less efficiently because it has too many other things to do. The tone arm of a separate installation merely holds the stylus on the groove, and swings in as the record plays. The tone arm of a record changer must also trip a mechanism which starts the changing cycle. As it leans against this switch, toward the end of the record, it drags the stylus against the outside edge of the grooves, distorting the eventual sound and (more serious) wearing out the shorter grooves.

Miraphon and Lenco Turntables

Since record changers do not have heavily weighted turntables, they lack the flywheel effect which makes for constant speed on precision instruments. The turntables are rarely a full 12 inches in diameter. This means that the vinylite record sags slightly as the stylus plays its outer area-and the stylus wears more heavily against the outside of the groove. Pickups are made to perform most accurately when the stylus is directly perpendicular to the flat record. A tone arm can be adjusted to hold the stylus in this position if there is to be exactly one record on the turntable. A changer, however, plays stacks of records, and the tone arm will bold the stylus perpendicular to only one of the records. The stack problem has other aspects, too. It increases the weight of the turntable which the motor is turning, and the turntable is likely to run slow as the stack builds up. Moreover, it never did a record any good to be dropped, and then to be gripped in the grooves of another record.

Miracord, Garrard and Thorens Turntables

Nevertheless, except in the very best systems (which will pick up the changer's characteristic low-frequency rumble) the record changer is an adequate way of playing records. Those with an all-LP collection will not want it (the man who is too lazy to change records every 25 minutes is too lazy to live), but others are likely to find that its convenience outweighs its defects. Many hi-fi families own both a changer and a precision turntable the former to accompany Madame's housework; the latter for more serious listening.

Record changers come in all varieties. The ultra-fancy kind, which turns records over, has not been made for hi-fi use-it takes a special and pretty poor cartridge. But the Thorens, Garrard, Miracord, Glaser-Steers, Collaro and Webcor (in descending order of price) are eminently hi-fi goods.

(Excerpts from the book Hi-Fi All-New 1958 Edition)

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