Features of the Mørch Tonearms
The MOERCH tonearms consist of an arm base with its mounting facilities, bearing assembly, balancing rod and weights, and the arm tube for the cartridge. One appealing feauture of the MOERCH design is the arm tube, which can be separated from the arm base by removing a nut. Four standard 9” arm tubes, each one of different mass (from ultra light to extra heavy), are available for specific cartridge requirements.
|Green dot: Effective mass 4 g.
Red dot: Effective mass 6 g.
Yellow dot: Effective mass 8 g.
Blue dot: Effective mass 14 g.
Standard 9” armtubes
The fundamental tonearm resonance (present in all arms) is partly determined by the compliance and the weight of the cartridge that is to be used and partly by the weight of the arm, known as the “effective mass” of the arm. However, the frequency of the fundamental resonance can be moved up or down by altering the mass of the tonearm. Thus, by choosing the correct weight of arm tube out of 4 available, the fundamental resonance can be moved to a frequency where it does not interfere with the audio signal.
With the lightest of the arm tubes you achieve the lowest effective mass, and with this particular arm tube the MOERCH tonearm is the lightest available today. This arm tube is designed for cartridges using a low tracking force, since they have a high compliance. For cartridges requiring a high tracking force (usually low compliant) one of the heavy arm tubes should be chosen. Users that own more than one cartridge can mount each of them in its proper arm tube. Changing cartridges then becomes a simple swap between arm tubes. Thus the mass of the arm is always optimized for its cartridge.
To counteract resonances the arm tube and its mounting platform for the cartridge are made out of one piece of metal angled twice along its length, and internally damped with a foam-type material.
A cavity in the central body housing the bearings is off-centered in the forward direction, providing an asymmetric mass distribution for the prevention of symmetrical barrel resonances. Both the rod with its balancing weights and the arm tube are rigidly attached to the arm’s central body. The body itself is solid and very heavy. Thus vibrations originating in the cartridge are efficiently damped before they reach the bearings, their stability being assured.
In addition three counterweights of different size, and one tracking force weight contribute to the ideal concentration of the arm’s mass close to the fulcrum. The lateral balance is adjusted by way of the counterweights, which have the center of gravity eccentrically positioned as to the counterweight rod.
The bearing assembly in the above mentioned cavity is in height located as an extension of the horizontal plane of the record surface. Therefore with warped records the motion of the stylus will remain vertical when “bumps” are negotiated and warp wow will not be heard.
The antiskating force is applied by a watch spring. Its tension is adjustable for maximum accuracy even while a record is playing. The tension is transferred via a nylon string which is attached to the outside wall of the arm’s central body. As the arm tube moves over the record, the correct geometry between the spring/filament assembly and the central body’s rotation provide for the exact variation of skating compensation over the entire playing surface of a record.
The tonearms are adjustable for the vertical tracking angle as well as the azimuth.
A Special version of the 9” arm tube called PRECISION is supplied with a wide cartridge mounting platform having the underside precision ground for perfect contact with especially wide cartridges.
Also 12” armtubes are available. They are available only with the narrow headshell such as the one on the standard 9” armtubes.
PRECISION armtubes and 12” armtubes are available only with red and blue color codes.
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