I have tried many different materials under my amps, preamps, cd players and turntables. My 3" granite slab is among the worst sounding of them all, no matter what type of couplers or damping materials are used. I don't believe the problem is as simple as "ringing" because it's hard to believe a 180lb slab of anything is ringing. But the granite does have serious colorations and they are unmusical colorations---they interfere with my enjoying the music.
I recommend trying some different types of wood instead of the granite. Each type sounds different and different thicknesses of the same wood sound different. You just have to try some yourself and reach your own conclusion about what you like best. My bet, however, is that the wood will sound much better than the granite.
A safe recommendation is to use a shelf platform made of 3/4" Baltic Birch void-free plywood. I have found this to be very neutral tonally with good dynamics and detail. Don't be tempted to use 1" Baltic Birch (too dull in the treble) or some type of plywood other than Baltic Birch. And whatever you do, stay away from mdf. Despite lots of companies using it for equipment shelves and speaker cabinets, mdf is also among the worst sounding materials.
I recommend trying some different types of wood instead of the granite. Each type sounds different and different thicknesses of the same wood sound different. You just have to try some yourself and reach your own conclusion about what you like best. My bet, however, is that the wood will sound much better than the granite.
A safe recommendation is to use a shelf platform made of 3/4" Baltic Birch void-free plywood. I have found this to be very neutral tonally with good dynamics and detail. Don't be tempted to use 1" Baltic Birch (too dull in the treble) or some type of plywood other than Baltic Birch. And whatever you do, stay away from mdf. Despite lots of companies using it for equipment shelves and speaker cabinets, mdf is also among the worst sounding materials.