Phonograph#Arm systems

The tone arm of a turntable is used to attach the pickup and the exact guidance of needle in the groove of a record.

The most common type is the Radialtonarm, wherein the pickup arm is rotatably mounted about a point. The rare -to-find Tangential, in which the tone arm moves parallel to the radius of the platter, though avoids some inherent disadvantages of Radialtonarms such as tracking error, but is technically much more complex.

Main components of the tone arm are the arm itself, either as a straight or Radialtonarmen as s-shaped executed arm, the attachment mechanism for the pickup, the counterweight with which the tone arm on different for cartridge and bearing forces can be adjusted, and Radialtonarmen an anti - skating mechanism. In Radialtonarmen from the professional field, such as the electrical measurement technology Wilhelm Franz EMT 929/997 the contact force generated by spring force. The company introduced the dual tracking force their tone arms, especially in the 1960s and 1970s, by means of a torsion spring in the horizontal tonearm one. Such designs can be recognized that the counterweight is mounted " swinging " pushed into a rubber bushing. In particular discs, which had a slight waviness, is the production of the support by means of spring force of the weight advantage, as a " Anarbeiten " with a moment of inertia as it is a simple counterweight reduces the scanning precision. As the inventor of a precursor form of the tone arm in the record applies gramophones industrialist Carl Lindström.

• 3.1 The half- inch standard
• 3.2 The SME mounting

Type

Radialtonarm

The Radialtonarm is rotating, ie a vertical radius kept in stock. Storage of a Radialtonarms leads inherently to the fact that the pickup does not occupy a constant angle to the groove of the disc on its way across the plate. This results in severe distortion when playing differently depending on the position of the pickup on the plate.

In practice, the tonearm and the pickups are adjusted so that the pickup at two positions on the plate ( for radius 66.0 and 120.9 mm) is exactly tangent to the groove to the distortion caused by the toe-in error over to minimize the total disk page.

However, the latest findings by Walter E. Schön have meant that the measuring points are redefined for the toe-in error on pickup system. His calculations are based on other geometric factors, such as the average game time of a disk page as well as DIN IEC98. The dimensions are mentioned here as follows: 62.5 and 117.2 mm (distance from the Tellerachs - center). When the perpendicularity to the tangent is set exactly at these two measurement points, including the measure of the overhang ( the distance from the Tellerachsmitte to the needle ) should match exactly. Thus, in this version of the calibration, two parameters are precisely defined. ( (Source: operating instructions and Declaration of Nice template type 2 with www.dos - hifi.de ) )

A variant of the Radialtonarme represent compensation arms, pivoted at which the tone arm and thus the pickup. Head and pickups are twisted here by a mechanism on their way from the outside to the inside of the plate relative to the arm and then the toe-in error compensated to a certain degree. The design effort for a play and friction -free bearing of the head is enormous.

The best known example was in the 1970s, the Garrard Zero ( UK).

Tangential

In a Tangential the tone arm is rotatably supported at a fixed point, it is moved on a slide tangentially to the turntable axis in a straight (linear ) direction. The main advantage of a Tangentialtonarms is that the needle is always exactly tangential to the groove in the ideal case. So occur less distortion because the needle at the same angle as the scans Schneidestichel, which forms the groove in the manufacture of the plate.

This was achieved in the early days by a servo motor, which nachführte the tone arm of the record groove. The arm was pivoted to the carriage. An electronic control responded to the slightest deflection of the arm from the linear ideal orientation by tracking the carriage. Disadvantage of this method was that the very first one - had to deviation occur, which could then be corrected - even if very small.

Servo Controlled Tangentialtonarme allowed technical gimmicks, such as vertical placement of the turntable or title programming similar to CD players. Some equipment manufacturers have, especially in the 1980s record player with these features brought out (eg, the Technics SL -J3 with other CD - usual features such as programming to eight tracks, automatic track skip and repeat, or HMK PA 1205 RFT with similar functions ).

Modern systems are mechanically improve continuously ( high-precision mechanical or air cushion support for the smallest friction), so that the Nachführkraft the record groove, the tracking force, sufficient for the tone arm of the record groove can follow by itself. The actual tone arm is no longer laterally rotated, but is firmly mounted on the slide in the tangential direction. Servo motors and control electronics fall completely off here. These tonearms are and therefore find themselves in the simplest form very complex only in the high- end segment.

Tangentialtonarme point of principle on no skating and do not require anti-skating measures.

Skating and anti-skating device

The anti-skating mechanism of a tone arm balances directed to the center of the turntable skating force in Radialtonarmen, resulting from the fact that grooves tangent and the imaginary line between the stylus point and Tonarmdrehpunkt usually are not aligned in the same direction. Although the track error angle (angle betw pickups and grooves tangent ) can be reduced to a relatively small interval (about ± 2 °) by crimping of the tonearm, the skating force is, however, not affected.

The real tone arm including offset can be reduced to the consideration of the forces on an imaginary tone arm ( green line). The friction between plate groove and stylus first acts tangential to the plate groove force Ft. This allows the imaginary tone arm by two mutually perpendicular forces take, namely the radial force Fr in the direction of the imaginary tone arm and the skating force Fs from the two different positions of the tone arm is seen that the skating force in these conditions, although always would drive the tonearm towards the center plate, the force becomes smaller when running on smaller groove radii. For this reason, anti-skating facilities need to build a dependent of the Tonarmstellung counterforce. The offset of the tone arm is deliberately exaggerated to show that the resulting skating force has no connection with the angles of the real tone arm to the plate groove.

The above friction force Ft is dependent on the needle shape and the contact force, which is why you usually adjust the anti-skating force on a scale of tracking force.

In the details picture for Tonarmlagerung a " static anti-skating mechanism " with a balance weight and a three-level adjustment will be used. Dynamically this is achieved by means of a spring force configuration, located in the lower part ( not visible) is the tone arm. A disadvantage of the dynamic design is the huge effort with possibly more sound-affecting components.

Installation standards for pickups

Tone arms can be equipped with different mounting options for the pickup. Some tonearms mounting is made directly to a built- in tone arm Haltevorichtung. As a rule, the pickup but not directly to the tonearm, but on a system carrier (English headshell ) mounted.

The system support can be attached in different ways to the tonearm. Simple usually older devices without high demands on sound quality often only offer a vendor- or even device-specific attachment of the pickup to the tonearm and head support. In this case, replacement of the series - pickup (usually a crystal cartridge) is not intended against a higher quality copy. In addition, clamping or adhesive bonding can be used, whereas high-order designs axial screw or bayonet fixtures are common.

In addition there are other proprietary quick-change systems for pickups and system support, such as the exchangeable TK - head support for half-inch cartridge with older dual turntables, the Japanese T4P standard or the SME bayonet attachment.

The electrical connections between the actual pickup and the head support or the Tonarminnenverkabelung via color- coded cables. A common color code: red for " " and green for "-" the right audio channel, white for " " and blue for "-" the left audio channel.

The half- inch standard

In the Hi-Fi systems the half-inch screws is widespread ( see picture). This designation refers to the horizontal distance between the two screws that hold the actual pickup is mounted in the system unit. The corresponding openings in the head supports are designed as longitudinal slots which allow adjustment of the track angle error ( minimal deviation from the exact tangent ) and precise adjustment of the needle overhang (distance from the needle to the turntable center). The needle overhang is also required for accurate sampling, as this in turn is dependent on the toe-in error.

The SME mounting

A very common system which also allows a quick and easy change of the cartridge, the SME bayonet attachment that comes to the tone arm of the manufacturer of the same name or the tonearm of Technics-SL-1200/1210-Plattenspielers used.

In the DJ field Pickups with integrated SME bayonet mount are widespread. For example, the geometry of the tonearm Technics SL-1200/1210 and the Ortofon Concorde cartridges are structurally adapted to each other: this is true, without further adjustment, the needle position for a slight toe-in error. The lower compared to the conventional design dynamic effective mass of the pickup also allows a more compliant storage of the needle (English: " compliance" ) and thus a lower tracking force - while maintaining the optimal mechanical resonant frequency of the existing of arm and cartridge spring - mass oscillator.

TK - attachment to the tone arm of a dual - turntable

Electrical contacts of a TC head support with dual M20E Cartridge