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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 4 responses by slimpikins5

slimpikins5's avatar
slimpikins5 OP
192 posts
 
OK, this is interesting; I spoke with the chief designer at Oracle Audio in Canada on this subject.  He said that my stock arm board puck on the VPI Ares3 is 1 inch thick acrylic which is a very good material.  He said Acrylic is a surprisingly good acoustic dampening medium and he suggested I stay with it.  If I go to another material, there is a risk of 'ringing'.  That will simplify my project, I can fabricate the parts I want for the VTA on the fly adjuster and bolt them to the stock arm board.
slimpikins5's avatar
slimpikins5 OP
192 posts
 
I do understand the strength to weight issue with magnesium, however I have also been told that it is very good at dampening sound vibrations which is why I was considering this material.  It would be nice to find a table of dampening values for various materials.


slimpikins5's avatar
slimpikins5 OP
192 posts
 
The service dept. at SME sent me a note this morning, they say magnesium would not be beneficial for the arm board, they like to use either aluminum or brass. Delrin is good too as yes its part of the super platter, which by the way I have on my Ares3.

But since the stock acrylic material appears to be a desirable material and its already made, I’ll stick with it. My plan was to make a one piece new arm board with a bump out on one side to accept the Tru-lift arm lift for end of record pick up and another bump out to accept my new micrometer head VTA adjuster. However last night I machined a stainless steel part which will bolt to the acrylic arm board and it will support the Tru-lift and offer adjustment so that the lift can be perfectly dialed in for where I want it to activate. I’ll make up other parts to mount on the other side for the VTA on the fly using the micrometer head.   This is actually easier for me as all I have to do is drill and tap the arm board to accept the new parts.
slimpikins5's avatar
slimpikins5 OP
192 posts
 
Thank you Atmasphere for the thoughts on materials used.
My Ares3 is Acrylic sandwiched with a center layer of aluminum.  The top layer of acrylic was machined out down to the aluminum layer so that the same acrylic material used for the arm board  is bolted directly to the aluminum.  In other words, the arm board is the exact same construction and materials as the plinth which mirrors what you stated.

I will stay with  this for sure (after the turntable does sound fabulous) and why fix what is not broken.


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