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Tone Arm board material

My VPI Ares3 turntable which is made with a laminated acrylic/aluminum/acrylic plinth, about 2.5 inches thick in total, has a 5/8 inch circular cut through the top layer of acrylic which exposes the center laminate of aluminum.  Set into this circular cut out is the 'puck' arm board mounting disc which is about 7/8 inches thick acrylic.  This bolts to the aluminum via three machine bolts.  My SME Series IV magnesium tone arm is bolted to the acrylic tone arm puck.

Magnesium is known for its superior vibration and sound deadening qualities, so I was wondering if anyone has any thoughts on making the tone arm board 'puck' out of solid magnesium vs. the factory supplied acrylic??  I can see why they probably don't use magnesium as it's super expensive.  I just got a quote on a small piece of magnesium to machine a new tone arm board and its $125.  But if it were to make an improvement in performance, its cheap money.

Does anyone out there have any thoughts on this?

slimpikins5

Showing 1 response by atmasphere

atmasphere's avatar
atmasphere
12,088 posts
 
The plinth of the turntable should be as dead and rigid as possible.

The thing that most people don't think about is that the arm board is part of the plinth. The base of the arm should couple as rigidly to the bearing mount of the platter as it can. If the arm board is made of a different material than what supports the platter bearing, its possible for vibration to move the platter on one plane while the base of the arm is moving in another or maybe isn't moving at all.

You want the base of the arm and the base of the platter bearing to move in the same plane at the same time or else the difference is interpreted by the pickup as a coloration.

IME for this reason the arm board should be the same material as the structure that supports the base of the platter bearing and hopefully that is the same structure that supports the arm board too.
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