MDF sand box tweak - effective for DAC, pre-amp?

Hi all,
I have heard about the MDF sand box tweak (a MDF box that
contains sand - the lid of the box rests completely on sand)
under CD player or turnable with good results.

Has anyone implemented this tweak under DAC or pre-amp?
How effective is it?
I appreciate your feed-backs
yes its a definite improvement, a preamp with tubes benefits more than a digital converter.
I use one under my TT VPI Jr and it is great. I also used them under my tube amps. Again with positive results. Little tweaks all add up to great results. I had a master cabinet maker make mine for $40 each. I painted them myself and they look and perform as well or better than the mass produced.
The only thing I would add to the above is to use Maple instead of MDF. All woods have a signature, maple, oak MDF etc. The top shelf, the one over the sand made out of maple or oak (solid, or glued like a butcher block)would make for a faster more alive sound than mdf. Besides if you stain it, it makes for a much more atractive material. Idealy make the whole thing out of wood, it will still be much cheaper than the comercially available ones.

Just my 2 cents. The original idea came from the folks at Shun Mook.

Good luck
I use the sand boxes for Pre-amp and Monoblocs. I found the sandbox sucked the life out of my cd player. I had better luck with the BDR #3 Racing cones under the cd player. If I had to do the sand boxes again, I'd use Corian on top of the sand instead of MDF. I sprayed the sand boxes with high gloss black (piano black). It took 5-6 coats because I forgot to use primer! So save yourself some time and get some primer to saturate the MDF before spraying with high gloss. They look really beautiful. Talk to your local kitchen outfit about using their kitchen sink Corian cut outs for your sand boxes.
Buckingham had the same idea as I as I was reading this thread, except I would use Corian for the entire thing. They have pre-cut back splash material which would make the frame, then use sink cuts for top and bottom. Just remember to leave a gap around the lid. I live in Florida, so I'm pretty familiar with sand. Can someone fill me in on how wood of any density would be better than marble or Corian? I thought the whole idea of these was to eliminate resonance? Thanks