Mass and vibration cancelling on top of CD player?

Making the chassis rigid doesn't prevent the disc from vibrating, which in and if itself is not too good for the sound. One way to ameliorate disc vibration and flutter is to obtain absolute level of the disc while spinning. Not as easy as it sounds.

My transport is level, but that is not as critical in my setup, as I use a Pioneer stable platter transport which clamps the disc.

I use low weight cast iron barbell weights (2.5, 5 lbs) to which I glued 1/8" cork on underside.

I don't understand why dead level is so important. It doesn't seem to matter to a gyroscope? I like the cork idea. Probably could serve more than 1 function.

Roxy54, you cannot ensure that the disc is spinning level by checking the level if the chassis. Just saying.