Bituminous Damping

With all the tweaks I've seen discussed in this forum, I've seen nothing yet about bituminous damping material. This is stuff that's sold for sound-proofing car interiors, and is sold at auto supply stores in the form of rectangular thin sheets of a square foot or more. What I've used came from Germany and is 2 mm thick, but there are similar US products. I've used it mostly on CD players, transports and DAC's, sticking it everywhere I can find room for it on the inside and on the bottom outside. It is self-adhesive, but with my German product, I had to use my own floor/tile adhesive for the underside of the lid--when I didn't, it sometimes fell off. It made quite an improvement in cheap CD players I treated for friends, though that was easier to hear in my system than in theirs. I don't know how much it helps DAC's or other components without moving parts, but for CD players, transports and DAT's, let me recommend it as a highly cost-effective upgrade.