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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
impulseh2
8 posts
 
I've had quite a few of these tables - all ex. BBC broadcast studios. They usually come from there mounted on ply motor boards which I guess are well less than an inch thick. They clearly sat into a desk. In this guise they sound awful...feedback may not be a problem as I suppose that they do not have large volume sound in the broadcast room itself and that the DJs wear earphones.

My experience is that the heavier a plinth the better. Google 'Kinyata SP10" and you will find the ultimate plinth. But, provided you remove the feet, the Technics obsidian plinths are petter than many think they are.
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
albertporter's avatar
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albertporter
4,927 posts
 
http://www.soundfountain.com/amb/sp10plinth.html

There's a guy named Albert Porter who has images of a very heavy plinth for his Technics SP10 MK2 posted at that site. Unknown if that's a benefit or not.
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