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
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
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.
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."
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.
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
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.
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
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)
- Click here
to see the cartridge history page.