Michael Lim Basic Aluminium Sub-platter .....


Introducing to you now a new Basic aluminium sub-platter with simpler design (more cost effective as requested by many) but keeping to the theory of "light mass" concept.

Basic aluminium sub-platter
(model ALSPZ) - USD129.00
Suitable For Rega RP1, RP3, P1,P2,P3,P5/P25, Planar 2/3
Why a light mass sub-platter?  What about the expected performance in comparing with a heavier mass design?

From moment of inertia* point of view, the sub-platter which is placed in the inner 1/3 segment (together with the glass platter assembly), contributes very much lesser to the moment of inertia as compared to similar mass at the outer 2/3 segment of the platter. So I believe it's better to keep the sub-platter light. Swapping to a heavy sub-platter would not be my choice as it would add unnecessary load to both the motor and bearing hub without much benefit to the moment of inertia. In fact I like the idea of underslung platter (like the new RP6 platter) which provides more mass at outer rim/segment.

Roughly in calculation, replacing a solid  aluminium sub-platter to RP6 would add a whopping ~240g(~8 oz) of extra load as compared to the total weight of stock phenolic sub-platter plus cap. The same goes for a solid full size metal sub-platter for RP3/P3/P5, adding  ~120g (~4 oz) extra load comparing to the stock phenolic sub-platter. In short, a heavy platter together with a heavy solid metal sub-platter is not a good combo as it could, very well push the system (motor and bearing hub) into "overload" conditions.

We have to understand that by any measurements, the Rega TT motor is a "tiny" one of several watts and hence we shouldn't simply add any amount of load as we like. Consider upgrading to a heavy RP6 metal sub-platter (adding 240g/~8 oz), a heavy stainless steel record clamp (adding 450g/~15 oz), a heavier after market platter (adding another 200g/~6.5 oz). The total extra load added would be 890g/~29.5 oz which is about 40% over the stock RP6 platter/sub-platter combo! I guess even Rega  RP6 TT designer would forbid!!

So in my humble opinion, it's better and safer to upgrade to an underslung platter with more mass at the outer rim together with a light mass metal sub-platter to achieve higher moment of inertia without the risk of over-loading the TT!

That's the reason in designing my aluminium sub-platters, "MASS" is one of the important factors I seriously consider. Other than as rigid as possible, it's also designed to be as light mass as possible. To achieve this, substantial part of the aluminum alloy mass is dug out carefully from the sub-platter. And anti-resonance pattern is crafted at the same time into the alloy to produce a unique looking sub-platter.

Besides, it's also more "stable" as the combo mass runs at a lower center of gravity(CG) which would result in less stress and wear at the bearing hub wall.

Enjoy tweaking!


*Note: Higher moment of inertia would increase speed stability, hence pitch stability, especially for single-belt driven Rega TT.





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