The
turntable unit.
All turntables work more or less the same way. They consist of a platter
that rotates the disk, and a pickup arm with a capsule that receives
instructions from disk and converts them into electrical signals.
The platter.
The turntable is to circulate and rotates to a pre-established velocity
moved by an electric motor. For disks of
L.P (Long Play) and for some maxisingles of 7 inches, has to rotate to 33⅓ (Revolutions for minute). For the majority of the disks of 7 inches
goes something more fast, 45 r. p. m.
The motor system is it more important of the turntable. Unless function silently and without no variation
of velocity, the sound will not be seen affected. A noisy motor, for example, will produce an
bother murmur ("rumble"). In
certain models of turntable, an electric motor of high velocity prompts the
platform by means of a band of rubber and the corresponding pulleys. More recently has been introduced the plates
of transmission direct, in which the axis of the motor connects directly with
the plate.
The tone arm.
The function of the tone arm is held in position while the needle is
offset by the disc. At the same time it must apply a tangential force correct.
This force depends on the type and quality of the arm. It can be adjusted with
a counterweight situated in an extreme of the arm. The arm also has been
designed to minimize the "slant" or natural tendency to move toward
the center of the disc.
The pickups are usually supported arms at one point and they have form of
"S" or "J". This type has a degree of "path
error" because the record does not disclose on a straight path, as did
head to burn the disc. At the present this turntables are available with arms
straight route describing a straight line on the disk.
The cartridge.
The first gramophone and plates turntables were equipped with cartridge
of crystal or ceramics. They have been
substituted for mobile types of magnet, magnet-induced/ mobile iron and coil mobile. All these generators of sign depend on the
relative movement among a magnet and a length of coil. The mobile type of magnet has a pair of coils
fixed. A small magnet mounted in the
extreme of the needle is moved responding to the vibrations of the same one and
creates in the coils a current fluctuating.
In the type of coil mobile, the magnet is fixed and the coils are placed
in the extreme of the needle.
The needle.
The needle, is united to the phono head or capsule. It has the tip of sapphire or diamond and
form hemispheric, although at present the elliptic form (biradial) is doing
popular. The width of the tip impedes it
to touch the fund of the furrow in the disk, but maintains it in contact with the
walls.
1)
Stereo Turntable Onkyo PX-55F. 1983.
2)Technics
Stereo Turntable System SL-1600. 1977.
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