01-31-09: Tvad
Not sure if I'm going to replace the Technics' feet, but I was considering brass footers from Starsound Technologies (Audiopoints), or the Isonoe feet.
I recently installed a sandbox under the Technics (designed by Thom Mackris of Galibier Design, and built by Timbernation), that has made an improvement over the Neuance platform I was using previously.
Long after I platformed my SL12x0 (wherein I noticed a significant improvement), I swapped out the stock feet for the Parts Express cones. The sound improved quite noticeably (my wife immediately heard the difference). All of a sudden I got the inner detail I'd been missing. Clarity took an overall jump, as well as a bit of speed, microdynamics, and a little bit of frequency extension. My platform is nowhere as sophisticated as yours, however, either before or after.
The image is larger and clearer, and my perception is that the volume level is higher at the same setting on my preamp. That's probably not true though.
This is a classic description of what happens when the noise floor is lowered. Low level detail pops out and everything seems louder.
Isonoe tests confirm that when you get the entire foot with the glass puck and the sorbothane boots, the Technics noise floor drops by a full 3dB. While this may not sound like so much, it's actually huge because it means your amp would have to be putting out twice the power as before to reach the same level of feedback. As a semi-educated guess, your description of the platform swap sounds like a 1.5dB lowering of the noise floor.
I *think* that brass cones transfer vibration from whatever the fat end is touching to whatever the point is touching. They would also make it difficult for in-room vibrations to travel up the cone in the other direction. If I'm correct, then brass cones would transfer turntable base vibrations into your vibration-absorbing platform.
Isonoe footers are designed to buffer vibrations both ways--they should neutralize in-TT vibrations while also isolating the turntable from the room. If you have another means to level the TT besides the threaded feet, one solution I've wondered about would be to place the (footless) turntable on a set of Vibrapod cones, which have Vibrapod feet under them. In this implementation the cones' metal balls would rest in the TT's foot threads. I would think that the Vibrapod foot/cone approach would do the same sort of thing for less money ($56 as opposed to $200+), but I don't know if this inexpensive approach would lower the noise floor by as much (3dB).
Anyway, the rig sounds great as it is, and I have no huge desire to change the feet, but I was curious about what adding brass feet might do.
I feel like my Technics didn't really start giving up the music until I swapped the feet. My opinion is that the stock Technics feet hold back its performance significantly. If you try it and find out otherwise, the worst that would happen is to have to pay return shipping.