RU2841486C1 - Electric turntable support disc damper - Google Patents

Abstract

FIELD: acoustics.

SUBSTANCE: damper of electric turntable support disc is proposed, made of at least two layers. Sound propagation speed in the layers differs by not less than 10 %, wherein the thickness of each layer is in range of 0.1 to 2.5 mm. At that, one layer is made of copper, and second one is made of aluminium, one layer is made of copper, and second is made of molybdenum, one layer is made of copper, and second is made of stainless steel, one layer is made of copper, and second is made of concrete, one layer is made of aluminium, and second is made of glass. Adhesive or glue layer is applied on the surface of one of the layers.

EFFECT: efficient suppression of sound wave energy by an excited pickup needle.

9 cl, 1 tbl

Description

The invention relates to the field of devices for damping resonance of sound waves in audio equipment, namely to dampers of the support disk of record players, damping the resonant vibrations of this support disk.

A turntable for vinyl or other gramophone records is one of the devices used to reproduce sound from an information carrier - a gramophone record. During playback, when the pickup moves along the surface of the gramophone record track, vibrations occur in the audio frequency band of 16-20,000 Hz (sound wave). The sound wave is transmitted inside the support disk, where vibrations occur that were not in the useful (original) signal, which are added to it, distorting the frequency response of the useful signal. Returning back, the changed sound wave affects the pickup head, and then through it to the entire signal playback and amplification path. As a result, unwanted overtones and / or parasitic vibrations are amplified along with the useful signal, which leads to the appearance of a "ringing" at the output of the audio path when playing a phonogram and other defects in the sound signal perceived by the listener (undesirable overtones, parasitic vibrations). There are various technical solutions to solve this problem.

The prior art discloses a record player disc (patent CA1145267A, filed 03.03.1981, published 26.04.1983), comprising a core with a central hole, as well as flat upper and lower surfaces. Both the upper and lower surfaces have concentric aligned inner and outer annular recesses. A soft viscoelastomer material suitable for damping microvibrations is attached to the upper inner and lower outer annular recesses. The upper annular mat matches the size of the record label when the record is coaxial with the record player disc. A hard inert viscoelastomer material is attached to the lower inner annular recess and the upper outer annular recess, which dissipates and dampens vibrations.

The disadvantages of this technical solution include the relatively low efficiency of damping the resonant sound wave. The above device is aimed at solving the problem of support table resonance by damping vibration due to the absorption of vibration energy in the viscous-elastomeric material. The disadvantages of this solution also include the lack of a material specifically selected for such purposes.

The SL-1200G direct-drive turntable (https://www.technics.com/kz/products/grand-class/sl1200g-series/sl-1200g.html, accessed 23.07.2024) is known to include a three-layer support platter. The bottom layer of the support platter is made of ADC12 aluminum alloy. The middle layer is made of styrene-butadiene rubber, and the top layer is made of brass.

The disadvantages of this technical solution include the inability to improve the characteristics of another player, except for the Technics SL-1200G, since the three-layer support disk is installed on the player during its manufacture. Another disadvantage of the above device is the complexity of its manufacture, due to the need for precision turning of the layers of the support disk.

Also known is a metal disc for the turntable support platter (https://highend-sound.com/produkter/vinyl-tilbehoer-1000vis/plademaatte/pure-sound-tenuto-gunmetal-plademaatte/, accessed 23.07.2024), made of solid metal with a large mass (2.2 kg) and a thickness of 5 mm.

This technical solution has a relatively large thickness, which causes a number of disadvantages, namely: the complexity of its manufacture and the impossibility of using it on various types of players. The complexity and high cost of production is due to the need to use a large amount of material and precise equipment for precision surface treatment, which is due to the impossibility of evenly pressing such a disc with a mat to the support disc due to its large thickness and rigidity. In addition, the disc height of 5 mm makes it necessary to adjust the tonearm height, which is not possible on all players and requires special skills.

The closest analogue is a sandwich of metal foam (compound) for eliminating and absorbing unwanted noise (e.g. impact noise) on high-quality turntables (patent application DE102017002732A1, filed 21.03.2017, published 18.10.2018). The device comprises a bearing, a rotating platform mandrel for holding the bearing and the plate, a first layer of metal foam with a thickness of 5 mm +/- 3 mm, a density of 0.35 to 0.45 g / cm ³ and a pore thickness of fine to medium, a layer of either an aluminum sheet with a thickness of 0.5 mm to 2-3 mm, or rubber (e.g. latex), or silicone, or cork, or wood, or sobottan, or acrylic, the next layer of metal foam with a density of 0.3 to 0.45 g / cm ³ and a pore size of fine to medium, which acts as the main layer, then another layer of aluminum sheet, the same as the top one, and a lower layer of metal foam, the same as the first layer of metal foam.

The disadvantage of these solutions is the large thickness of the turntable support disc (from 5 to 30 mm) and the need to reconfigure the height of the tonearm due to the thickness of this disc. In addition, the problem is the occurrence of resonant frequencies in the electric record player, which worsen the quality of playback, while the devices used for this are thick (from 5 to 30 mm), therefore, when installing such a device on an existing player, it will be necessary to reconfigure the position of the tonearm, or such devices are an integral part of a specific player, which does not improve the characteristics of the user's existing player, so the closest analogue does not have universality.

The technical problem is the need to develop an effective damper for the turntable platter that is free from the above-mentioned disadvantages.

The technical result consists in the effective damping of the energy of the sound wave excited by the needle of the sound pickup in the support disk and returned back to the sound pickup at the resonance frequencies (the main and its modes) of the support disk for various types of record players with a smaller thickness and weight.

The technical result is achieved in that in the damper of the supporting disk of a record player, made of at least two layers, according to the invention, the speed of sound propagation in the layers differs by no less than 10%.

In the most preferred embodiment of the invention, the speed of sound propagation in the layers differs by at least 20%.

The following options for performing layers are also possible (indicating the speed of sound propagation, longitudinal wave, in m/s and the difference between the values of this parameter in layers in %):

- copper (5010 m/s) and aluminum (6420 m/s), 28%;

- copper (5010 m/s) and molybdenum (6250 m/s), 25%;

- copper (5010 m/s) and stainless steel (5790 m/s), 16%;

- copper (5010 m/s) and concrete (3700 m/s), 35%;

- aluminum (6420 m/s) and glass (4800 m/s), 33%.

In some cases, it is possible that one surface of one of the layers has a sticky or adhesive layer applied to it to provide better adhesion to the backing disc.

The proposed invention is a universal damper for a turntable of small thickness and weight, which can be installed on any turntable and effectively dampens the energy of a resonant sound wave that occurs when the needle of a pickup moves along the track of a gramophone record, and as a consequence, reduces overtones in the audio frequency range, and improves the quality of reproduction.

The damper of the turntable support disc is made of at least two flat layers of different materials, wherein the materials of the layers are selected in such a way that the speed of sound propagation in the layers differs by at least 10%. In the preferred embodiment of the invention, the speed of sound propagation in the layers differs by at least 20%, the thickness of the layers is selected in the range from 0.1 mm to 2.5 mm. The layers can be fastened together, for example, using glue or in another way. The following combinations of materials are possible:

- Copper (5010 m/s) and aluminum (6420 m/s), 28%.

- Copper (5010 m/s) and molybdenum (6250 m/s), 25%.

- Copper (5010 m/s) and stainless steel (5790 m/s), 16%.

- Copper (5010 m/s) and concrete (3700 m/s), 35%.

- Aluminum (6420 m/s) and glass (4800 m/s), 33%.

Other combinations of materials are also possible within the framework of the claimed invention. Also, in the preferred embodiment, a sticky or adhesive layer is applied to one surface of one of the layers for better fixation on the support disk, while the layers are rigidly fastened together. In the most preferred embodiment, the damper is made in the form of a disk with a diameter of 12 inches, which corresponds to the standard format of LP records. In this case, the diameter can be selected for a specific player, if it has a larger or smaller support disk. In all embodiments of the invention, there is a hole for the spindle in the center of the damper.

The claimed device operates as follows.

The damper of the turntable platter is installed between the gasket (mat) and the turntable platter, with the turntable spindle (the axis of rotation of the record) located in the corresponding hole of the device. Then, when playing a sound signal from a gramophone record, due to the difference in the speed of sound propagation in the materials of the layers of the damper of the turntable platter, the damper dampens the vibrations induced by the pickup needle, which arise in the platter and are added to the original signal, distorting its frequency response. Damping of these vibrations occurs due to the divergence of the peaks of sound waves in each layer due to the difference in the speed of sound propagation in the layers, since when adding up the amplitudes of sound waves propagating in the layers, the amplitude of the resulting wave is weakened. Thus, the damper of the turntable platter, touching the platter over its entire surface, does not allow it to "ring". Moreover, the disturbance spot that spreads from the pickup when using the Platter Damper is effectively damped twice:

1) when the wave goes from the pickup to the platter, meeting on the way with the damper of the platter of the turntable;

2) when the remaining part of the vibrational energy returns to the pickup through the damper.

In addition, as stated earlier, the “ringing” from previous disturbances of the support disk is damped at all points of contact of the support disk with the Support Disk Damper.

The claimed invention is illustrated by an example.

In order to study the efficiency of damping the energy of the sound wave excited by the pickup needle in the platter and returned back to the pickup at the resonance frequencies of the platter for different types of turntables with a smaller thickness and weight, tests were carried out on different versions of the device, as well as a prototype device (according to patent application DE102017002732A1) on two turntables: Elac Miracord 80 and Dual CS 626. More detailed data on the samples is given in the table.

Table - data of test samples:

Item No. Composition of layers Speed of sound propagation, m/s Difference in sound propagation speed in layers 1 and 2, % Sample thickness, mm 1 layer 2 layer 1 layer 2 layer 1 copper aluminum 5010 6420 28 0.4 2 copper molybdenum 5010 6250 25 0.2 3 copper stainless steel 5010 5790 16 0.6 4 aluminum glass 6420 4800 34 1.0 5 aluminum stainless steel 6420 5790 10 0.6 6 aluminum molybdenum 6420 6250 3 0.2 7 copper glass 5010 4800 4 1.0

Sample 8, which corresponds to the prototype device, also participated in the tests.

During the tests, a focus group of five people assessed the sound, including the presence of “ringing” and other defects in the sound signal (overtones, distortions), as well as the quality of the sound signal according to a number of subjective parameters (volume, clarity, transparency, timbre) when installing each sample on the two aforementioned players.

Two minutes were allocated for listening to each sample (one minute on each player). Afterwards, the focus group participants rated each sample on a five-point scale. The average results were as follows: sample 1 – 4.7 points, sample 2 – 4.8 points, sample 3 – 4.2 points, sample 4 – 4.1 points, sample 5 – 4.0 points, sample 6 – 3.6 points, sample 7 – 3.5 points. Sample 8 received an average rating of 3.4 points.

Thus, the proposed invention provides effective damping of the energy of the sound wave excited by the pickup needle in the support disk and returned back to the pickup at the resonance frequencies (the main and its modes) of the support disk for various types of record players with a smaller thickness and weight, which is expressed through an improvement in the quality of reproduction of phonograms and is confirmed by the test results.

Claims (9)

1. A damper for a turntable support disc, made of at least two layers, characterized in that the speed of sound propagation in the layers differs by at least 10%, while the thickness of each layer is in the range from 0.1 to 2.5 mm. 2. A damper according to item 1, characterized in that the speed of sound propagation in the layers differs by at least 20%. 3. The damper according to item 1, characterized in that one layer is made of copper and the second is made of aluminum. 4. The damper according to item 1, characterized in that one layer is made of copper and the second is made of molybdenum. 5. The damper according to item 1, characterized in that one layer is made of copper and the second is made of stainless steel. 6. The damper according to item 1, characterized in that one layer is made of copper and the second is made of concrete. 7. The damper according to item 1, characterized in that one layer is made of aluminum and the second is made of glass. 8. The damper according to item 1, characterized in that the layers are rigidly fastened together. 9. A damper according to item 1, characterized in that a sticky or adhesive layer is applied to one surface of one of the layers.