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
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 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.
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

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.
The plinth shown on the above site is not a Kaneta plinth.
It is however beautifully made.

The Kaneta system for the SP10 involves discarding the whole chassis, power supply and mounting - just the motor and platter - in a fruit-wood plinth made from strips of wood (pear i seem to remember) which are glued alongside each other. There are 4/5 such layers each at 90 deg. to each other glued together vertically.

The PS is ditched in its entirety and a circuit designed by Kaneta is used as an outboard supply. This supply contains many now obsolete devices.

But as I have said above AP's work looks to be excellent and I would like to hear this alongside my own SP10 which has had the original PS boards taken off - chassis and mounted in an external-case connected by umbilical to the deck. It is in the original Technics obsidian (the solid version) plinth (as in my previous post) and the table sits on a sand-box. This treatment has lowered the noise floor to un-noticeable level....inky black in fact. The result is greatly enhanced dynamics, a MUCH more solid sound-stage with vast improvement in transparency and an altogether improved listening experience. This is most noticeable when listening to small scale classical music. The arm is a stripped to essentials Zeta rewired and an Audio Note Io from the first month of production.

I am confident that this set-up will outperform all but a very small number of TTs. I am seriously considering investing in a better arm and am unsure what to Ikeda 12" appeals!
Impulseh2, I have an early IOj and it does best in an Ikeda FR64x rather than a new Ikeda 407, OTOH my Denon 103R performs best in the Ikeda. I also great great results with the IO in an SMEV, but it is a bit fiddly to install. I might try it one day in my Triplanar VII, but not intuitive with the fixed wiring for both and having to use conectors.