Fairchild Tables
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.
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.
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.
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.
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.
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.
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.
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)
