The stylus of a vinyl record player is a chunk of diamond which, although very small, has a certain mass.
Mass, as we know from Newton's laws of motion, likes to stay in a constant state of stillness, or motion at a constant velocity. It takes a force to cause it to change velocity.
So where does the force come from to make the stylus change velocity, as it must to follow accurately the undulations of the groove?
The answer is from the walls of the groove. The walls of the groove provide the force that accelerates the stylus. There are two problems:
- If the groove attempts to accelerate the stylus very quickly, the vinyl material of which it is composed may be damaged
- Although the groove can accelerate the stylus in an upward direction (actually +/- 45 degrees for the two walls of the groove of a stereo record), only gravity can bring it back down again. If the stylus loses contact with the groove, mis-tracking occurs causing distortion, and the groove will probably be damaged when the stylus lands.
Control of acceleration is provided by an acceleration limiter, invented by Neumann, in the cutting lathe, which obviously affects the audio signal. The audible effect of the acceleration limiter is similar to that of a de-esser, though where the de-esser would be fine-tuned to vocal sibilance, the acceleration limiter is more of a brute force tool. The purpose of the acceleration limiter is to protect your stylus and your vinyl, and if a little hi-fi is lost in the process so be it.
Of course, such a sound can be an acquired taste. Word has it that when some old recordings by The Clash were re-mastered for CD, a TC Electronic processor was used to emulate the Neumann acceleration limiter, to get that authentic LP sound on CD.