It is for vibration and so the metal does not ring. It works really well for turntables. I use a VPI turntable stand filled with sand for my ClearAudio Inovation Wood turntable. For tube gear I prefer maple. I went from a SolidSteel rack to a Zoethecus rack and amp stand. It made a big difference especially for my amp.
Equipment rack with hollow tubes.
Ive heard alot about filling equipment racks with hollow tubes with sand... What is the reason behind this ? For vibration ?