Granite surface plate

I think the use of stone top shelves has been discussed, try a search of the archives.

I can post pages on that experience but the short answer is putting that much mass even slightly above the floor invites oscillation.

Think of an upside down pendulum. It's especially bad for turntables, less so for preamps but it has a sound that once identified is annoying.

Granite surface plates are a good idea that never quite worked out, at least for me. I don't know where you live but I still have one or more here that you may have for free.

Try a 2" thick slab of Delrin.. did wonders for my table. But not cheap.. around $1200

I agree with Albert. I've tried them on numerous occasions on many different components and they ring like hell.

They do look pretty. Wish they worked/sounded better.