Granite surface plate

I've been using 2" granite, layered with 3/4" Corian, separated by 1/8" felt, under my amps for a couple years. My VPI turntable is sitting on top of a cabinet I built(30 years ago), on 2" of granite, atop 1 1/2" of HDF, with Texas Instruments EMI/RFI Shield and 1/8" felt between. There is zero acoustic breakthrough or resonance, as cramped as my sound space is, regardless of listening levels. As Mr G mentioned: Don't hit your granite with a hammer, and it won't ring. I'm NOT going to worry about a resonant frequency of ONE Hz.

Jump on granite don't worry about the sound.

I second Roxy54 recommendation of Adona shelves. Been using them under my TTs for years.

The Adona shelf won't cost a fortune, and it's just a "set it and forget it" solution that avoids a lot of experimentation and looks good.

I have granite shelves in my equipment closet and have no ringing problems at all. I have rubber vibration pads for the appropriate weight between the shelves and the shelf support, a sheet of sorbothane secured to the bottom of the shelf that the turntable sits on to dissipation energy that the pads do not deal with. I have no ringing at all from any shelves.