Thu, 2012-05-24 21:56 — walker
Donor: Helt
Vinyl records and turntables utilized analog technology to record and play back audio. Sound was encoded as variations within the tracks of a phonograph record, and needles sensed these variations. Early records rotated at 78 RPM but fast speeds limited the length of a sound recording. Thus, slower speeds (33 1/3 and 45 RPM) evolved to allow a balance between sound quality and the possible length of a recording.
Sony's PS-LX150 Turntable, manufactured about 1995, illustrates the state-of-the-art recording possible at the time.
- Since motors are subject to vibration and speed fluctuations, a belt drive connected to motor to the turntable. The turntable was relatively heavy, so its momentum would mitigate many variations in speed from the motor.
- Since a phonograph worked by a stylus rubbing against the tracks in a record, both the phonograph record and the stylus were subject to wear, and wear caused sound quality to deteriorate over time. Thus, turntables used a counterbalanced tone arm, so that the stylus could track the analog signals with minimal pressure. Also, a diamond stylus was preferred as having the longest life.
- Sideways pressure on a needle and any warping of records could cause distortions in sound. The PS-LX150 uses a long, straight tonearm to minimize these effects.
- Dust could add to wear, so top-end phonograph players came with a dust cover.
Source: Personal experience of Prof. Henry Walker
