I am not making this up.
Yesterday I was goofing off on The IntarWebs and came across a DIY isoloation project.
Picture the bottom half of a shallow wooden box, just larger than your turntable.
Got that picture in your head? Now put an inflated bicycle tire inner tube (the kind for 20" BMX bikes) inside the box. The inner tube isn't fully inflated - probably to 90% capacity. The inner tube is sticking out of the shallow wooden box 1/2" to 1".
OK, now take a big ol' piece a wood, like a giant butcher block, and set that down centered over the inner tube and box.
Now place your turntable on the butcher block.
The creator of this DIY project said he did it all for less than $20 plus glue, stain and varnish he already had on hand.
If anyone really wants me to, I'll try to track down the site again. (I'm goofing off on The IntarWebs again today )
Current primary listening: SMMC20EN -> BG4002 -> BM4000 -> Beovox M70