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Building plinths for quality DD tables?

Nearly every reference I've read on building a plinth for a Technics SP-10 series table assumes high mass is needed, similar to Garrard, Lenco, etc. rim drive tables. Yet, the SP10 does not display the same noise and vibration problems as a rim drive. So why would a similar massive plinth be needed? Did this idea originate with the two Obsidian plinth models offered by Technics?

I'm in preliminary design of a plinth for my SP-10 Mk2A and a friend who also owns an SP-10 recommends a minimal plinth - basically a platform to bolt underneath the table, along with a tower to mount the tonearm. He lives a great distance away so I cannot audition the performance of his set up. So, does anyone have experience with a minimum plinth design rather than the more typical 40-50 pound plinth? If a minimal plinth would work as well, it would be much simpler to build.

If you have experience with plinth building for SP-10, Denon, Kenwood/Trio, etc., I would appreciate your input.

Thanx, Pryso
pryso

Showing 1 response by quiddity

quiddity
119 posts
 
A direct drive motor's counter-torque is directly coupled into the chassis. This is an inevitable consequence of it being a direct drive, so it can't be avoided (unless you can work out how to suspend Newton's Third Law of Motion). Since a DD servo loop maintains constant speed by rapidly correcting the torque of the motor, the counter-torque must also exhibit these same variations.

I believe that DD designs are defined by how successfully they deal with this problem. The most original solution was Sansui's X99 with its counter-rotating platter but I've never actually seen one.

The most promising approach I have seen recently is Jonathan Weiss's custom cut slate plinth for the SP10.

Mark Kelly
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