Stereo Turntables ~ CLASSIC HI-FI EQUIPMENT

Stereo Turntables

The turntable unit.

All turntables works more or less the same way. They consist of a plate that rotates the disk,and a pickup arm with a capsule that receives instructions from disk and converts them into electrical signals.

The plate.

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 r.p.m (revolutions per 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.