October, 1977
Ampersand
19
Quick, Watson
The ( Phono )
Needle
There's a time-encrusted cliche to the effect
that the best things in life come in small
packages, with diamonds offered as proof. In
that case, the cartridge with its diamond
stylus ensconced on the end of the tonearm of
your record player comes right within this
category.
Of all the components in a high-fidelity
system, the cartridge is the most neglected,
the least understood. This is a strange situa
tion, since the kind of music supplied by your
hi fi depends directly and most often on the
phono cartridge. Phono records represent
our prime music source, taking precedence
over tape and broadcasts, so overlooking the
cartridge is a sound tactical error.
The cartridge is just one member of a
strange family called transducers, devices
that change one form of energy to another.
This makes the cartridge first cousin to a
storage battery, a steam generator, a
loudspeaker, a microphone and a solar cell.
In following the grooves cut into your
phono record, a diamond stylus (your grand
father called it a needle) can wiggle back and
forth as much as 20,000 or more times per
second. This mechanical belly dance moves a
tiny cantilever to which is attached a coil, a
magnet or a small bit of iron, depending on
the design of the cartridge. The coil, magnet
or iron, in motion produced by the movement
of the stylus, helps produce a tiny electrical
voltage which corresponds in every respect
(or which should do so) to the undulations in
the record grooves. This voltage is then fed
into a pre-amplifier where it is strengthened,
then into a power amplifier where it is given
heavy doses of current, strong enough to
operate your stereo speakers.
All of this sounds simple enough, and it is.
Up to now the cartridge and its stylus isju'st a
device for generating a voltage. It is when we
start making other demands on it that we
encounter some problems.
We want the cartridge to develop enough
voltage so it will be strong enough to drive the
pre-amplifier to which it is connected. Car
tridge voltage output should be large enough
to eliminate the need for a pre pre-amplifier
or a special cartridge output transformer.
We don't want the cartridge to develop
electrical noise. We want to be able to replace
the stylus easily and quickly when it becomes
worn, as it inevitably will. We want the stylus
assembly to be able to move easily, to be
quickly responsive to the faintest modula
tions cut into the record grooves, yet we do
not want the stylus to vibrate of its own ac
cord. We want the cartridge to supply relatively
equal signal outputs for both stereo channels.
And we don't want the signal from one stereo
channel drifting over to the other.
In short, what we want the cartridge to do
is to recapture for us as much of the original
sound as possible out of the record grooves,
without adding to, modifying, or distorting
that sound. We want the cartridge to respond
to all frequencies without favoritism, starting
at about 20 Hz, or lower, and extending to 20
kHz, or higher.
This isn't a complete list, but it is indica
tive of our demands. Quite often these
present conflicting requirements.
A cartridge with a coil at one end of the
cantilever is, quite obviously, called a
moving-coil cartridge. If it has a tiny magnet
affixed there instead it is called a moving
magnet cartridge, but that's as far as seman
tic logic will take us, for if it has a bit of iron in
place of the coil or magnet it is called a vari
able reluctance type. Of these three, the most
popular, the most widely used is the moving
magnet. Serious audiophiles have expressed
a preference for moving coil cartridges,
claiming superior sound output, but until
recently such cartridges have been accom
panied by any number ofdisadvantages. One
of these has been low audio signal voltage
output, so low that such cartridges have re
quired either an accompanying step-up
transformer or a pre pre-amplifier. Also, with
a typical moving coil cartridge, replacement
of the stylus could not be done by the user.
Installing a new stylus meant returning the
cartridge to the original manufacturer.
These problems have been overcome in the
Satin line of moving coil cartridges. No out
put transformer or pre pre-amplilicr is re
quired since the cartridge has sufficient out
put so it can be connected directly to the
magnetic phono input of any high quality
preamp. In the Satin cartridge the stylus as
sembly is attached to the cartridge by mag
netic force and so stylus replacement isjust as
easy, if not more so, than in the usual moving
magnet type.
One of the ways of getting higher voltage
output in the moving coil cartridge is to use
more turns or wire in the moving coil. Satin
has achieved this with an extremely thin
aluminum ribbon measuring 10 microns x
100 microns. There are two such coils, one for
the left sound channel, the other for the right.
All cartridges require damping of the
movement of the cantilever to avoid un
wanted cartridge resonance. Ordinarily,
rubber is used. It is quick and convenient,
but natural rubber is a vegetable product and
even when made with anti-oxidants gradu
ally loses its flexibility and becomes stiff.
The damping system in the Satin car
tridges consists of a lubricant and an elec
tromagnetic force that damps in proportion
to the speed of movement of the cantilever.
With rubber-type damping material the
w hole system sometimes fails to respond to
very small vibrations superimposed on a
larger w ave of vibration, especially when the
small vibration is below a certain level. With
the Satin damping system the cartridge never
misses the smallest signal oscillation in the
record groove.
The Satin Model M-18 carries a nationally
advertised retail value of $155.00. Satin has
available a free booklet entitled "The Car
tridge Handbook: What You Should Know
Before You Buy a Cartridge." You can get a
copy by writing to Osawa & Co. (USA),
Dept. CN, 521 Fifth Avenue, New York,
N.Y. 10017.
Every time you position the stylus of a
cartridge into record grooves you are present
at the accouchement of sound. But if that
sound is to be strong and healthy and beauti
ful, the tool of parturition the cartridge in
this case must be electrically and mechan
ically competent.
After all, that's where your sound begins.
Martin Clifford
Mr. Clifford, whose column will be a
regular feature in Ampersand, is an
authority on stereo equipment.
Q)ii '
Try) 0
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