Octave Audio - Non Magnetic Main Platter

By: Octave A Audio Us  09-12-2011

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

Other products and services from Octave A Audio Us


Octave Audio - Plinths

Our "Solid Design" plinth was developed to satisfy demands for a massive plinth which could deliver real sonic improvements (NOT the case with many of the replacement plinths we've encountered, which are sonically detrimental to the TD 124's performance). Replacing the plinth is simple - just lift the chassis out of the original and place it in the new one, making sure that the rubber mushrooms and their metal supports are correctly seated.


Octave Audio - Main Platter Bearing with Shaft

From the standpoint of decoupling, this is an excellent solution, but the combination of the heavy rotational force of the drive system and insufficient tolerances of the supplied parts inevitably resulted in extensive wear. The set includes a complete main platter bearing with shaft, an addtional replacement bearing thrust plate and oil gasket und a bottle of Thorens oil.


Octave Audio - Hardenet Alloy Upper Platter

After experimenting with various casting and machining properties, extensive sonic tests led us to eventually choose a much harder aluminium alloy, more difficult to shape and machine than the original but delivering improved sonic performance. Our goal, as always, was to produce a "new vintage" product which respects the sonic, mechanical and aesthetic properties of the original Thorens part while offering advances in sound quality.


Octave Audio - TD 124 Tonearm Boards

The shape of the 12" armboard has been expressly designed for resonance control, bringing with it substantial sonic improvements. Our replacement armboards for the TD 124 are hand made from select beech by Swiss craftsmen. Carefully adjust the tonearm according to the manufacturer's instructions. Taking care not to forget all grounding wires. Octave Audio - TD 124 Tonearm Boards.


Octave Audio - Tone Arms from Ortofon

VTF in the range 0-5 grams can be precisely adjusted by means of the supplied digital force gauge. With dynamic balance graduated vertical tracking force control through a new spring design. Ortofon now introduces tone arms to the North American market. Dynamic tone arms: RS-212-D and RS-309-D. Static tone arms: AS-212-S and AS-309-S.


Octave Audio - Moving Coil Cartridges

Many of the first generation of moving coil cartridges were low impedance and low output units which demanded a transformer or a comparable step-up device. Some of today's most exclusive moving coil designs still deliver the ultimate in analogue sound quality through a specially developed matching transformer. Each of the four coils contains between 11 an 24 turns of wire, depending on model, and has to be wound by hand under a microscope.


Octave Audio - Motor E 50 MK I / MK II Conversion Kit

This was recognized early on by Thorens, and accounts for the differences in motor decoupling between the TD 124 Mark I and Mark II models. Correct decoupling of the motor from the chassis is a key element in any turntable design. The motor suspension rods were lengthened and additional damping devices. Motor E 50 MK I / MK II Conversion Kit.