Home made turntable isolation

for the isolation of the tt, try this: you could call it 'hifitommy's toysRus isolation trick'. go to tRu and buy two paks of children's water toys that have the rings and arm floaties. use the four arm floaties from the two packages of toys. inflate and place a mdf board the size of your tt on them, and adjust air for levelness. this gives a stable and DEAD isolation for your tt. and its SOOOOO pretty. an enterprising chap could make an inverted box that doesn't touch the cabinet and put veneer on it for looks i suppose.
you can now hammer on the cabinet with VERRRRRY little or no sound thru the spks while the cart is on the disc. its so cheeeeeeep that its embarrassing.

I went to a NY Audiophile meeting where the guy poured a cubic meter of concrete on a steel dolly that had threaded cannisters for leveling. Seemed to work with foot falls and high sound pressure levels.

Cylinderking_1,

Another suggestion would be to use cork between the sheets of steel. It's much better than foam. Has good isolation properties but not the mushiness of foam. Also, cork doesn't collapse like foam might under continuous weight.

This might be 2X the price you quoted of $125 in your post -how about a Neuance shelf from Ken Lyon? I have 2 friends who are using it & swear by it. One has it under his Spacedeck & the other under his VPI Aries. The Aries perf. went up a few notches w/ the Neuance shelf under it. Maybe you've already checked into this & decided it's too expensive?

Have you considered commercially available damping materials used (for example) to isolate electric motors from their mounting surfaces in boats to eliminate noise?

I'm not an analog guy, so I really don't know if you want to isolate the TT from the rack in the same way, or if you just want a steady base for it- from TWL's comment I would suspect you may not want to isolate it per se because a hunk of maple really wouldn't be as effective as a couple of rubber pucks of the right consistency, but the maple reportedly sounds better. But, if you do want to isolate it you should be able to buy a sheet of vibration damping material engineered for any of a number of given weights / vibration frequencies at a pretty low cost to sandwich between your sheets of steel, which would make a nice isolation platform. If you could pin down what characteristics you really want, there will be someone with an isolator material that fits your needs.

check this out: http://www.vmc-kdc.com/pdf/pad_e%2B.pdf as an example of what's out there

good luck-

I'd use a thick piece of butcher block maple. It sounds better than foam. I have even read some accounts of where people have replaced their VPI plinths with solid maple to good effect. Just my opinion, but soft absorptive materials generally tend to deaden the sound of a TT.