Stereo and CD players

 

The record player and speakers

In the best hi-fi systems, the turntable is heavy and usually belt-driven to isolate it from the vibrations of the motor.

The stylus has a rounded tip and is usually made of synthetic sapphire or diamond. It is fitted into a pick-up head that also contains an electromechanical transducer, a device that converts the vibration of the stylus as it moves along the disc groove into electrical signals. The transducer is commonly magnetic - as the stylus travels around, it moves a magnet inside a wire coil and induces an electric current in the coil.

Two coils are used, a different one to sense the vibrations of each stereo track and produce current for the left-hand and right-hand output signals. These signals are replicas of those that operated the cutting stylus on the master disc.

The output signals coming from a pick-up are very weak, and have to be boosted in the electronic circuits of an amplifier. Some of these circuits control volume, tone and balance.

From the amplifier the boosted signals are fed to each of the loudspeakers, where an electromagnet vibrates a cone-shaped diaphragm to convert the signals back into sound waves. A simple speaker has a single cone, but speakers in hi-fi systems have two or three separate, different-sized cones because each size is best for reproducing a different range of sounds (or frequencies the higher the sound, the greater the vibration frequency).


Musical Technologies