When you record on a vinyl disc, the sound is transferred into a recording needle. The needle scratches grooves in the disc. The sound manipulates the scratching into different wave forms. So when you run a stylus (or playing needle) through the grooves , it reverses the process and vibrates the needle. A preamp picks up the vibration. The vibration that it picks up is the song scratched into the disc.
Vinyl records are records that are made of polyvinyl chloride (PVC), and are thus called vinyl records, or simply vinyl. Some common types of vinyl records are LP (long-playing) records, 16 rpm records (16's) and 45 rpm records (45's). The other two commonly used records are 33 1/3 rpm records (33's), and 78 rpm records (78's). Their rotational speeds are measured in revolutions per minute or rpm. A normal commercial disc has two concentric spiral grooves. These are located on either side of the disc. It is from these two spiral grooves, which run from the outer edge of the disc towards its centre, that the sound is produced. Both sides of the disc have started carrying the spiral groove since the late 1910's.
Before the late 1910's, vinyl records had a spiral groove only on one side of the disc. The record is played by rotating the disc clockwise. The rotational speed should be kept constant, and the stylus or needle should be placed in the groove. This positioning of the stylus and maintaining a constant speed of rotations makes it easier for the stylus to convert into an electric signal (or magnetic cartridge). The signal is then sent to loudspeakers through an amplifier.
