How Does a Record Player Work?

How Does a Record Player Work?

The Theory

Edison phonograph

The first functioning record player, called a phonograph, was constructed by Thomas Edison in the late 19th century. Though his machine looked significantly different than modern record players, it operated on the same principal. Because all sound is vibration, Edison knew if he could record sound vibrations on a physical medium, the vibrations could be reproduced from the recording. In Edison's day, it was just as amazing to be able to record sound as it was to hear the playback. His first phonograph used grooves etched in tin foil to record his rendition of "Mary Had a Little Lamb"--the first sound recording.

The Application

A turntable consists of three main parts: the turntable, tonearm and stylus. The turntable in Edison's day was actually a metal cylinder. Today, it's a flat, rotating platter. Early turntables were belt driven, meaning a small motor would move a belt or a series of gears attached to the center of the turntable and cause it to rotate. While still in use in some turntables today, this method causes the turntable to start slow and speed up as the machinery approaches full speed, and also to slowly grind to a halt when stopped. Many turntables today are direct drive, meaning they are powered by electromagnets that can be turned off and on with a switch and start and stop very quickly.

The tonearm is fixed to the turntable and extends to the surface of the recording medium, usually a vinyl disc. For precision, the tonearm can be lowered or raised with a lever, but can also be manually placed. On the end of the tonearm is the stylus, the part that actually makes contact with the record and reproduces the sound recorded there. The friction created as the stylus passes over the grooves in the record recreates the sounds that etched the grooves.

The earliest styluses had crystal tips that generated an electrical charge when compressed. This charge was simply amplified to reproduce the recording audibly. Ceramic styluses replaced these in the 1950s, producing a smoother stereo sound and offering less resistance to the grooves, which meant less skipping. Today's styluses use a diamond tip connected to an electromagnetic coil, much like a guitar pickup. Movements of the stylus create a fluctuation in the electromagnetic field that induces an electric charge in the coil. When amplified, this charge is a reproduction of the original recording.

Making Records

The creation of a vinyl record is much like the playback process, except in reverse. Instead of passing a stylus over grooves to recreate a recording, an album cutter connected to an input source passes over a blank disc and etches the grooves into place. From this master copy, a metal stamp is made and copies are mass-produced.