Granite under wood for better isolation?

Regards, Tonywinsc: I too am a believer in laminated bamboo for isolation purposes. For custom applications, most cabinet shops can supply 3/4" material cut to your dimensions.
For consideration:
An 18 x 22 x 3" bamboo (open bottom) "box" of 3/4" laminated bamboo was lined with 1/4" builder's closed cell styrofoam insulation and stapled in place, joins were taped to prevent leakage. 2" decking screws were run 1/2" into the underside every 3", leaving a length exposed to anchor concrete (large aggregate removed) poured into the platform's cavity. A triangular bracket was fixed inside to each corner. Outside shoulders then rounded with a router and after sanding, a coat of oil finish applied to the outside before placing the concrete. The brackets provide a surface for mounting feet. 2" felt discs are used there now but might be replaced with spikes, cones, sorbo. pods, pucks etc. later on. Materials used were those currently at hand. Distortion from mechanically sourced vibration is effectively addressed. As no elevator shafts are available, I will remain pleased with the results.

It could be that my catridge and arm work better with the wood.. The instruments just sound more natural and I get less inner groove vibration with the thick maple. One thing I may do is Lower my table so I get more soundstage. The maple is very dense and is in the wrong place as far as at my ear level. Once I move it lower I think I will be very very happy. The wood isolates better for me than the granite. I do understand what you are saying by the turntable liking the granite. The wood and granite both have their own sonic signature. I have gone back and forth but so far the maple is winning.

Tony, I see your plinth is already solid wood. Nice table by the way. Maybe with that being the case, the granite may be the perfect fit.

Sand is your answer. Maple deadens the music. Put the granite into a sand box. All ringing will be gone.

I will have to try that.