want new plinth ideas for direct-drive turntables

I know its not popular, but go and try once for heaven's sake a plinth which is suspended with low resonance frequency - below 3Hz.
It is not the plinth weight, composition or raw material - isolate it from any outside vibration and your eyes will pop wide open how the sound and stability change for an unknown quality.

i've been living with the active air suspension and air bearing of the direct drive Rockport for 8 years and could not agree with you more. mass only takes things so far; ultimately any gounded tt will become a seismograph as it attains higher and higher levels of detail and tells you about how the earth sounds.

OTOH high mass plinths do yield very high performance overall. (of course, the Rockport has a 250 pound plinth, along with air suspension).

the Dobbins Technics SP-10 Mk3 with the 'naked' plinth (110 pounds) and the Dobbins Garrard 301 (80 pounds) are sitting on the decoupled Grand Prix Audio Monaco rack with Formula shelves. the GPA does offer a fairly effective passive decoupling that seems to work with these tt's. but more sophisticated active suspension would likely take things up a notch in refinement and low level detail.

i have pondered how a Halcyonics or Herzan Stable Table would do under the Mk3 or 301. would that added benefit get it closer to the Rockport?

Hiho, Great idea about the magnetic or other drive to "connect" the platter to a dd motor. I know it's good idea, because I have thought about it, too. (Heh-heh.) The problem is that if you are a direct-drive purist, any such coupling mechanism could defeat the virtues of direct-drive. I have never seen the EAR turntable, but I have imagined that there must be some elasticity of the magnetic "connection" between motor and platter in their magnetic drive system, which takes us back to the disadvantages of belt drive. I guess if you have a VERY powerful magnet and if the airspace between driver and driven is VERY small, then you would have almost zero elasticity.

Lewm, let me assure you that I am NOT a purist of any kind - in audio I am more of an anarchist. *Laugh*

Back to this concept turntable. I actually WANT to have a tiny bit of compliance to filter out whatever cogging inherent in a DD motor. I have done some experiment (nothing purely scientific here so please don't jump on me if you are militant about it) with using two DD turntables driving each other via a belt, an idler wheel, and direct-drive. Each one has its own sonic signature and the softer the compliance the softer the sound, the direct-drive being the hardest sound but also the most powerful sounding. Each has its plus and minus.

I also tried with DD tables with various torque, the higher torque the more powerful the sound but the lower the torque the smoother and fluid the sound. As you can see in these sonic results there's a relationship between torque and compliance. Of course, for me the ideal situation would be to have the perfect motor with zero cogging and go the purist direct-drive route. I neither have the resource nor knowledge to obtain such perfection so fiddling around is fun for me.

Anyway, what I am aiming for is a hybrid by separating the turntable from the motor in a direct-drive arrangement, that is, driving the platter right below the rotational center but also decoupling from each other. In the EAR Disk-Master and Clearaudio Statement, they go the route of non-contact magnetic force. I agree with Lewm that there must be some compliance between the connection gap so I would simply make them contact with some material from hard to soft (ranging from rubber to acrylic to metal to whatever) to "dial" in the compliance that would fit the motor behavior to filter out any cogging that remains.

The really tricky thing about this arrangement is the construction of the bearing since we need the bottom center to extend down to make contact with the motor below, that very center is where normally the thrust plate and ball bearing are in a conventional stick in a hole bearing. The EAR Disk-Master has to resort to "angular contact bearing", essentially a series of balls in a circumference instead of a single ball so they have the potential to be noisy.

One day I would like to find a machinist who can help me modify a platter and bearing so I can place it right above a conventional DD turntable like a Technics SL-1200Mk2 or motor unit of the SP-10Mk2. Essentially having a DD table at the bottom "centered driving" the above platter. Wouldn't it be fun to experiment with various DD tables in this arrangement to try them as a "motor"? My thought is that why re-invent the wheel when we already have so many DD turntables as motor in the used market. Just think of the possibilities. The EAR and Clearaudio could have used a direct-drive approach but instead they opted for belt drive, in fact the EAR uses gear belt to avoid belt slip. And the Clearaudio is essentially using one of them top belt-drive tables center driving a massive platter above it - not so clever.

There are really so many ways to make direct drive in terms of platter, bearing, rotor, and stator arrangement. Maybe I am losing some of you because I think like a deconstructionist or a gear head and whenever I see a turntable I see the sum of a platter/bearing/motor arrangement and automatically visualize each component individually and how each contribute the whole system. I NEVER see them as a box that plays records and that's the kind of disease that this hobby bought me. :-) I am an incurable tweaker when resource(money) and knowledge allows of course.

Thanks for indulging me, Lewm. :-)

Some pictures of the EAR Disk-Master and Clearaudio Statement:

http://www.dagogo.com/assets/images/image/EVENTS/2010%20CES/Coverage%202%20-%20Turntables/2010CES-2-EAR.jpg

http://www.positive-feedback.com/Issue34/images/019_EAR_turntable.jpg

http://www.enjoythemusic.com/rmaf_2007/friday/disc_master_belt.jpg

http://lh6.ggpht.com/headfi/R4_D1PGuqNI/AAAAAAAAADg/it_dJNpjqlA/s400/IMG_7850.JPG

http://www.clearaudio.de/download/presse/statement_presskit_07_en.pdf

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Mikelavigne, I have seen (rather: heard...) both the Minus-K and Vibraplane changing the performance of Micro RX-5000, TW Acustic Raven AC 2, Platine Verdier and VPI TNT all for the better. I would recommend adding a suitable active or passive isolation platform underneath ANY turntable which has not a built-in low frequency suspension (frankly - the Platine Verdier did benefit only very minor from the Vibraplane as it's own suspension works - if aligned well - pretty good).
I will soon have the opportunity to audition the Halyconics in a familiar top-flight set-up.
I will report, whether it's performance does exceed the Minus-K or Vibraplane.

Dertonarm, i'm not surprised with your experience with isolation such as the Vibraplane and Minus-K. i will be very interested in your audition of the Halcyonics. 4 years ago i had a Halcyonics in my room for an evening and it was very eye openning hearing the effect on my digital transport and preamp. i only had my 600 pound Rockport at the time so i did not have a chance to try it under a tt.

btw, you likey would enjoy this tutorial about SOTA active isolation from the Herzon site. read all 6 pages. it mentions and compares the best passive isolation such as the Minus-K and air suspension to the current active technology.