Turntable Essay

The word turntable is the modern term used to describe what is known as the phonograph, gramophone, or record player. The first turntable was invented by Thomas Edison in 1877. It was the first device used for recording and playing back sounds. Modern turntables have the same fundamental components as their ancestors, albeit slightly more sophisticated in design. This paper covers the fundamental technical aspects of modern turntables.

A modern turntable basically works like this: A platter (on which the record sits) is spun by a drive system. The drive system spins the record at specific revolutions per minute (RPM). A pickup system in the form of a stylus and cartridge converts the audio on the record into an electrical signal. A tracking

An electrical voltage is created when pressure is applied to the crystal. In a piezo electric pickup system, the stylus is attached to the crystal, which protrudes from the end of the cartridge. The pressure applied to the crystal comes from the motion of the stylus as it tracks the grooves cut in the record. In other words, as the stylus moves along the grooves of the record, there is a slight wobbling, bumping movement which causes pressure of different magnitudes to be applied to the crystal. This pressure generates electrical voltage, which then, through the design of the cartridge, creates an electrical signal to start flowing through the system. This signal then flows through some wires in the turntable and on to an amplifier. Piezo electric pickup systems are usually fairly robust, and since the electrical voltage that is produced is proportional to the applied pressure, these systems yield a good level of signal, and require only a small amount of amplification compared to magnetic pickup

The pickup system is connected to one end of the tone arm. Therefore, one of the most important functions of the tracking system is to apply a tracking force between the pickup system and the grooves of a record. Depending on the type of pickup system, the tracking force will be large or small. For a piezo-electric pickup system, the tracking force is relatively high because of the weight of the crystal. However, magnetic tracking systems are much lighter and need significantly less tracking force.

The counter weight attaches to the opposite end of the tone arm and acts to balance the weight of the pickup system. The counter weight is adjustable, which is a necessary feature in order to balance the tone arm so that just the right tracking force is applied. The tone arm needs to be relatively light so that it does not create sideways drag on the record as the grooves spiral inward. This is where the anti-skating device comes into play. This device attempts to offset the small, inward force applied to the record, so that the stylus itself is left with no net force on it in the horizontal direction.