Physics of the Turntable

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Have you ever wondered how a record player works? Probably not. After all, who still listens to records? Surprisingly enough, turntables are making a come back. With the recent surge of interest in hip hop music, popular attention has been turned towards the turntable, used by DJs to provide beats, loops and scratching for virtually all of today's hip hop groups. The inner workings of the turntable may seem complex at first but after reading this paper it should become clear that, like all things, the record player works on basic principals of physics. In fact, the turntable is remarkable in that the basic physical principles behind it are quite simple. Some of these will be explored here. Please enjoy your visit. How a record player works is quite simple. A motor is somehow connected to a solid disc so that the disc is rotated at a constant speed. On top of the rotating disc (platter), The record is placed on top, with a slip mat in between. The slip mat can serve two functions. In the past to hold the record in place so that it would not rotate independently of the platter. Now, however, the slip mat serves a much different function. Instead of holding the record in place, the slip mat is now used to reduce the friction between the spinning platter and the record. This way a DJ can scratch (manually move the record, usually at high speeds) the record while the platter continues to spin underneath. Once the record is rotating, a stylus glides along the grooves and picks up the vibrations, these are then converted into audible sound. There are many different models of turntables still being manufactured. Of those being sold, it is possible to divide them into two separate categories based upon their motor system. Virtually all record players being manufactured today have either belt drive or direct drive motors. For the reasons discussed below, direct drives are accepted as the industry standard for professional DJs and turntabilists. Belt Drive - There are two advantages to the belt drive design. The motor in a belt driven turntable is set away from the platter by means of a continuous belt loop. This minimizes vibration to the platter and thus needle skipping. Also, belt drive models tend to be much cheaper than their direct drive counter parts. These advantages, however, do not balance the many short falls of the belt drive design.

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