looking for damping material for my dac

Trying to internally damp my unit (DAC) I need a non conducive metal or XXXX, must he heavy and solid that can be screwed on.
2 pieces L8 X W2 X H2 inches.

Thinking about Slate / Granite / any suggestions??????

I think you would want non magnetic metal or XXXX, but that alone might cause vibrations in other places. I would also damp the inside of the cab with Soundcoat, or Sorbothane, and maybe some Marigo dots on the board, chips, and caps. I mass damp my cabinets on the outside with a brick, shakti, brass, bag of sand, etc. with a piece of damping between the top of cab and weight(except for the sand), i've used bubble wrap in that application also.
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