Isolation for turntable

David, all of my experiences have shown that the less "soft" material under the TT, the better. Preferably none. Hard materials that control vibration would be preferable to soft in a TT application. I strictly steer away from rubber, springs, air bladders, sorbothane, and the like in my personal TT support. I have always found rigid stands with good solid direct coupling to the floor have always served me better, especially in terms of bass and dynamics. Different people have different needs and tastes, but that is what I have concluded. It was better on all my different kinds of TTs, in different houses and rooms. However I don't play at 117db, so that could make a difference. Up to 108db, I have found no ill effects from this type of setting.

As far as adding more weight to the stand, that would be individual to the turntable in question. It will certainly change the vibration characteristics of the stand, and it may be better or may be worse. My guess that with a TNT it might be a little better to have more weight, but I'm not certain about it.

I agree with Twl on this, even though I still use the custom table-base I designed for my TNT. It features 3" square metal tubing feet, filled with sand and stand on cones. They support a 2" high density board on top of which I placed 4 inner tubes from wheel barrel source. On top of the tubes there is another 2" board with black melamine. On top of which I have placed all my maple bases on my newly designed TT. (see, " VPI redisigning experiment").
My advisor, Pierre Sprey of Mapleshade, from whom I ordered the maple boards, feels that Sand, metal, air bladders etc, degrade the sound, he has found that components sound most natural when they stand on solid blocks of maple. The cones he uses are either solid brass feet or the ones made from layers of cork and ribbed rubber, ( pardon the expression!)
I tend to agree with him and Twl. I will take out that heavy air bladder table I have under my TT, as soon as I can. I will keep the heavy feet but I will place a butcher block from maple on them and then the solid maple bases of my new TT.

I second Twl & Tphalieros' advice for rigid base, no soft items under the TT.
One a/market shelf that can do the job (is rigid and efficient in vertical vibration control) is the Neuance, mentioned above. But again the principle is the same: rigid base, lightweight if it's standing on a hard floor...

Of course, those advocating the totally rigid approach to TT support are also presumably disinclined to prefer an integrally-suspended TT at all, including the TNT Jr.'s own self-damping compressed-elastomer based system - which is apparently correctly pre-tuned to do the job it seems to be working fine at in David's set-up. As I said above, I wouldn't necessarily recommend adding any additional compliant support to his TT, especially since he reports no feedback problems as is.

check out this earlier thread...
http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1046040392&openusid&zzSlipknot1&4&5#Slipknot1