I have three racks with glass shelves in metal rectangular section tubing.
I filled all the tubes with sand in all three racks.
One low long one is for the Plasma TV and video stuff.
Another low long one I have two turntables on, plus some stuff under.
And the third tall one my main audio stuff.
I use butyl rubber bottle stoppers, and Sorbothane half domes.
The cheaper half domes are on Amazon. Same as the expensive 'audiophile' ones.
The sorbothane are softer, the Butyl a bit harder.
I also do some 'wedging' so the next up shelf is pressed on from below by rubber near the center or near the middle sides.
I find the rubber.sorbothane does all I need to stop the shelves from vibrating.
Even a cloth pad under the equipment would dampen the shelf. Even some rubber round things used to dampen sub cabinets, stuck under the center of the glass, or on top hidden under the components...
Butyl Chemical bottle stoppers, size 10 are great. Problem is they are getting to be hard to find on the internet.
I got mine from a local 'Science and Surplus', and have at least 40 of them!
Aside: if your glass shelves never bothered you, why worry what some 'know it all' claims?
To test if you can hear a difference, just use anything to dampen the shelving. Cloth, or whatever is at hand. (even your hands.. Can you 'feel' any vibration in the shelving when your system is at maximum listening level?)
