Non Magnetic Main Platter
The TD 124 "drive platter", also known as the "main platter" or "sub-platter", is an essential element in the Thorens design concept. Thorens chose cast iron for the TD 124 series due to its outstanding properties: high density and damping capacity, great rigidity and extraordinary dimensional stability. These structural advantages, so important to the Thorens sound, involved one major disadvantage: the platter is magnetic, limiting the choice of cartridge. Heavy cartridges with strong magnets – like the Ortofon SPU – were drawn to the platter by magnetic attraction, sometimes to the point of damaging the cartridge. Tracking force across the platter, and accurate anti-skate was impossible to achieve. To address the problem, Thorens engineers in Sainte-Croix experimented extensively with alternative platter materials. Each of these experiments resulted in a platter which was either prohibitively expensive or sonically inferior to the original formulation. In the mid-60's, for example, Thorens offered on special order a non-magnetic replacement main platter manufactured from pressed aluminum. The platter was produced by Inca, the Swiss foundry that also produced the TD 124 chassis. In addition to the excessively reduced weight (2.8 kg), the platter brought with it distinct sonic disadvantages, namely high-frequency ringing! For this reason the platter was never offered as a standard component in the TD 124 series. Similar problems plagued the lead prototypes that Thorens also experimented with.
The only appropriate material for a sonically superior non-magnetic platter is "grey cast" iron with graphite flakes, a unique compound developed by the US marines for minesweeping operations during World War II. This unique alloy shows a 98% reduction in residual magnetism compared with the standard cast iron, while equaling or bettering it in terms of density, stability and damping properties. At the time, however, high raw material and production costs limited the availability of this material for civilian applications.
Today, however, we can offer a non-magnetic replacement platter weighing 5 kg - nearly the same weight as the original – which surpasses the original in all respects. Our replacement platter is manufactured from raw materials chosen without compromise, followed by state-of-the-art casting, precision machining and finishing and faithful reproduction of the original strobe markings, all carried out by the finest Swiss specialty firms. The new, non-magnetic replacement platter for the Thorens TD 124 Series I and II meshes effortlessly with the original Thorens concept, while offering the advantages of:
- no magnetic influence on cartridge coils or magnets
- exact, reliable anti-skating adjustment now possible
- lower noise floor and radically enhanced dynamics
- greater overall tonal balance and coherence
- extended frequency response
- tighter bass
- no restrictions on cartridge selection