Devices {changer} {turntable}| {record player} can play one record at a time or automatically play a stack of records.
speeds
Records can turn at 16 2/3, 33 1/3, 45, or 78 revolutions per minute (rpm), to match speed at which master disc was cut.
needle
Needle holder {cartridge, record} is at one arm end, and needle rests in record groove. Pivot is on other arm {tonearm} end, for balance. Needles can be steel, sapphire, or diamond. Needle vibrates in groove and generates an electric signal.
Crystal or ceramic cartridges make electric signals by piezoelectric effect. Magnetic cartridges make electric signals by a magnet moving in a wire coil.
amplification
Wires carry signal to a device {preamplifier}, which reconverts signal to proper high and low frequency strength {equalization}, not needed for ceramic cartridges. Preamplifier has knobs to control loudness {volume control}, high frequencies {treble control}, low frequencies {bass control}, and loudness between two stereo speakers {balance, speaker}.
speaker
Amplifiers increase signal power and send signals to a solenoid connected to a paper cone {speaker, audio} {loudspeaker}. Speakers are typically the least-accurate music-system part, so they are the most-important part.
sound
Electrical-signal shape can change {sound, distortion}. High fidelity limits total distortion to less than 15%.
Sound-frequency range has a loudness range {frequency response}. Loudness is in decibels. A three-decibel difference doubles loudness. Humans can detect a one- decibel difference.
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7-Machine-Kinds-Electromechanical
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Date Modified: 2022.0224