+1 @bdp24 - I use a sandwich of granite from my local kitchen counter shop + leftover 3/4" oak + the acoustic wall damp material. I think technically you are supposed to use 2 different materials separated by the acoustic damping material - there is a technical name for it which I forget right now. Am supporting tube amp, preamp and TT with 1 stand under each for a total of 3 stands. Easy to make. No noise when I rap with my knuckles. The TT plinth does resonate when I rap with my knuckles, but unsure what to do about that. TT is a stock VPI prime - 10 years old this Dec.
YMMV of course