Surprisingly, the design of the record has not changed much since it was invented in the mid-19th century. Naturally, the materials from which they are made have also changed, and the technology of making and recording master discs, but the very idea behind the gramophone recording remained unchanged.
This idea is generally simple, but at the same time not quite trivial. To record a master disk, i.e. a disk from which copies are subsequently made, a chisel is used, which, under the influence of sound, makes oscillatory movements and cuts a winding groove on a rotating disk made of amorphous material. This technology has not undergone significant changes since its invention, only the principles of propulsion of the pick have changed. If in the beginning the cutter was driven by a membrane, which was forced to oscillate directly by sound waves reinforced by a horn, then later, with the advent of electrodynamic converters, the mechanical membrane was replaced by a voice coil, the anchor of which was connected to the cutter.
Initially, while no single recording standard had yet been developed, each manufacturer installed its own, resulting in different rotation speeds of the recorded recordings as well as different types of modulation of the recorded audio tracks. Track modulation is a form of track modulation that contains information about the recorded sound. Modulation can be transverse, in which the recorder's cutter oscillates in the plate's rotation plane (the depth of the audio track remains constant), as well as deep, in which the cutter oscillates perpendicularly to the plate's rotation plane and cuts on it the soundtrack shape, but with a variable depth. When playing a gramophone plate, the process of its recording is reversed. The needle of the player, following the sound groove, repeats the complex oscillations of the recording tool and is connected to the converter of mechanical oscillations in the sound (initially mechanical, and then electrodynamic) allows generating sound.
In the course of the development of the recording industry, deep modulation of the soundtracks has proven to be inefficient and uncomfortable, and all manufacturers have opted for the transverse modulation option.
In the late '50s of the last century, a very serious event occurred in the technology of recording gramophone records - the emergence of stereo recording. When recording a mono signal, the process described above, the recorder's cutter is driven by a single electromechanical converter and cuts a modulated groove of constant depth on the plate's surface, with the edges of the same shape. The stereo recording still uses one incisor, but it is moved by two transducers mounted at right angles to each other and 45 degrees to the record surface. Two independent transducers cause the pick to vibrate, reacting independently to the sound signals to be recorded in the right and left channels. Under their influence, the cutter makes a complex oscillatory motion, modulating the cut groove not only in the transverse direction but also in-depth. As a result, the right wall of the cut groove turns out to be modulated by the signal of one channel, and the left wall - by the signal of another channel.
The form of the modulated groove at stereo recording differs from the monophonic one. In particular, its walls are not parallel to each other but have different shapes. As you can see, the stereo record of the gramophone record is not completely independent for both channels, because the incisor is only one, and when playing both channels are read by the same needle, which is located when moving along the audio track in contact with both walls and making complex oscillatory movements, containing information about the sound vibrations in both channels. There is nothing to say that adequate transmission of such a complex signal is not a trivial task and requires the highest precision of all mechanical and electrical parts and components of the player.
Vinyl players are more sensitive than any other audio equipment to the slightest inaccuracy in installation and adjustment, require complete protection against external and internal vibrations and are very demanding on the quality of the carrier itself - i.e. vinyl disk. That's why the storage and maintenance of gramophone plates are very demanding. The microscopic dimensions of the soundtrack and, accordingly, the subtle movements of the pickup needle result in the fact that even small scratches on the surface of the disc or the smallest dust particles become sources of interference and noise during playback, leading to parasitic movements of the pickup needle, i.e. such movements, which are caused not by the modulation of the soundtrack, but by external factors. The voice coil does not distinguish between useful and parasitic vibrations, so if the latter lie in the audio frequencies, they will be carefully converted into an electric signal and transmitted to the amplifier for reproduction by loudspeakers in the form of noise.