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Decca International arm
The Decca engineers designed a tone arm to match the Decca London cartridges.
It has specific features:
1. Frictionless unipivot with magnetic bearing. This reduces rumble. This was probably devised with the turntables of those days in mind: Garrard 301, Garrard 401, and Lenco/Goldring.
2. Optional fluid damping. If it is necessary to dampen the fundamental resonance of the cartridge-arm combination, the appropriate viscosity can be selected.
3. Magnetic Bias Adjustment. This design (later followed by other manufacturers) further isolates the arm completely. The arm is free as opposed to those arms which use threads and small weights.
4. Complementing sound pattern. As the review in Hi-Fi Choice showed, the measured frequency characteristic of the arm is different from most arms. This sound characteristic of the arm compensates for the frequency characteristic of the Decca cartridges. The arm is best suitable for the older Blue and Gray, MKV, and Mk VI, respectively. For the later Decca Gold and Maroon some prefer
the Hadcock arm. The Decca International arm is not suitable for most non-Decca cartridges as trials with the Denon DL-103 showed. But then the silicon damping fluid was not removed.
5. Precise leveling of cartridge (VTA and Azimuth) and balance. The arm can be adjusted to very a high and very fine level to retrieve the complete signal out of the record groove.
In general the use of magnets for the arm bearing is not preferred by all designers. They do not go for rubber insulators either, for threads and weights in bearings, or other ways of de-coupling the pivot with the aid of a magnet. They prefer the "grounding" of the arm to the chassis or plinth right at its base.