The goal of the vinyl turntable tonearm is to position the cartridge needle on the record track. Positioning involves moving the needle from the edge to the center of the vinyl plate, as well as providing the necessary angle between the needle and the vinyl plate.
The tonearm consists of a tube, a rotating mechanism, a clamping force regulator, a rolling force compensator and a mounting platform for the cartridge. As we have said, all the vinyl turntable components are very responsible, but the tonearm design is probably the most mechanically complicated.
The tonearm must move the head of the cartridge in such a way that it smoothes out the irregularities on the record's surface. The record has a large enough surface to be perfectly flat. If you look closely, you will find gentle waves on any of them. At reproduction, tonearms should move on these waves, without their own influence on the size of the pressure of a needle on walls of a sound groove. As you can see, this requirement requires that the tonearm be as light as possible. Unfortunately, by making it too light, we will immediately get a reduction in the dynamics of playback. The curves of the audio track that drive the pickup needle will drive the entire tonearm, and because it is the tonearm that is attached to the voice coil, the signal generated by the voice arm will be too weak. In other words, not only will the needle oscillate, but the whole tonearm oscillate, which is completely useless in terms of sound reproduction. So what happens? And it turns out that on the one hand, the tonearm should be light enough, and on the other - quite heavy enough. To meet these conflicting requirements must be very subtly to maintain the right balance. The slightest mismatch and that's it... You won't be a fan of vinyl sound after that.
In order to understand the mechanical characteristics of the tonearm, let's see what kind of interference it has with the record. To be more precise, this interference affects not only the tonearm but the entire oscillating system that it forms with the pickup head and its moving system.
On the one hand, it is affected by sources of low-frequency vibrations, such as the bending and eccentricity of the plate (when the hole does not exactly match its geometric center), vibrations caused by bearing rotation, and external vibrations from the floor or walls that are transmitted to the player. The frequency of these vibrations lies in the infrared frequency range (less than 8 Hz), and therefore the resonance frequency of the tone pickup vibrating system must be higher than this value. On the other hand, the needle of the cartridge transmits vibrations from the audio track of the recordings that try to rock the tonearm oscillator system with sound frequencies (i.e. from 20 Hz and above). This means that the resonance frequency of the tonearm oscillator system must be lower than the sound frequencies. Otherwise, the player will have a sharp drop in bass response. The art of a quality tonearm manufacturer is to ensure that their products have the correct resonance characteristics, i.e., that they have proper resonance frequencies lying in the area between the above values.
In addition to calculating the intrinsic resonance frequency of the tonearm, the manufacturer must also take care of the good damping properties of the tonearm tube itself. It must never transmit vibrations from the chassis to the moving cartridge system and must be rigid enough not to have any effect on sound reproduction.
The rolling force tends to turn the tonearm towards the center of the record. As a result of the rolling force, the needle of the cartridge experiences different pressures on the sides of the groove - stronger on the inner wall and less on the outer wall. As a result, the sound level, as well as its detail and processing in different channels, may differ. To prevent this from happening, the players are equipped with rolling force compensators (anti-skating), i.e. such devices that provide the force equal in size, but oppositely directed to the rolling force.
Among the main types of such devices can be called a weight suspended on the thread on the backside of the tonearm, spring anti-skating, where the reverse force is provided by springs, as well as magnetic, where it occurs through the interaction of two magnets.
Turntable tonearm system: It is obvious that the tonearm rotation in both horizontal and vertical planes should be completely free. The resistance to rotation in any of these planes will have an immediate impact on the correctness of reading the audio information from the track of the record, so the design of the rotary knot manufacturers pay very high attention.
The design of the unit is usually based on the use of large bearing sizes, the balls of which are made of extremely hard materials and carefully polished to avoid the slightest roughness that can affect the smooth and uniform rotation of the unit.