Lol. Lead is one of the worst materials for sound that has ever been perpetrated on naive and gullible audiophiles. Yes, I know it seems like a good idea, all soft and heavy like. 😛 Even the esteemed Pierre Sprey at Mapleshade grew to detest lead although he was a big fan for a long time and, according to your humble scribe’s sources, had one of his employees cart out 200 lbs of the stuff to Las Vegas for use in CES shows.
Besides, mass loading simply changes the resonant frequency of the component. It is not really a substitute for real vibration isolation. I.e., mass on spring. If one is determined to use heavy mass on top of a DAC or anything else, you will have much better luck incorporating a viscoelastic material under the heavy mass, I.e., constrained layer damping.