Sandbox-style isolation

I have built a number of sand box type shelves for various systems over the years. I do think they can sound good and are a good approach for DIY. I built a very nice set of amp stands that looked great and sat under a set of tube BAT VK150SE monoblocks I had. I also had another system that had a set of Pass Aleph 2 monos. I had a set of stands I had built for the Aleph 2s that was a box but instead of sand I used a small inner tube under the top platform. After getting some Grand Prix Audio amps stands for my BAT amps (which by the way were hugely better than the sandboxes) I decided to try the sand box stands under my Aleph 2s since they looked better. I hooked them up and man something was wrong the sound just wasn't that good at all. I didn't even think about the stands, but I just new some magic was definitely MIA. Well finally I switched back to the inner tube the sound came back.

So the verdict that I have came to is that you never know. I know for a fact that isolation can make or break a system, so for any reasonably good system I don't mess around with homemade sand boxes

If you can someway find yourself a vibraplane that is a huge upgrade for a turntable or any component for that matter.

Ejlif, Did you ever try combining coupling and decoupling by placing the inner tube or large springs underneath the sandbox? IME this strategy is very effective (particularly with TT), as is cutting up the sandbox top plate to isolate each component footer.

J Loveys, I did see your pic on line and it did catch my eye. How do you level the table? Did you have a sand box before the Symposium? I have quite a few symposiums in my systen and do like them quite a bit. I wonder how much better it would be than what I currently have (what I have sounds awesome). I also wouldn't want to give up the ability to level, so I wouldn't be direct coupling the plinth to the base, but, rather, keep the table on the feet and have the feet rest on the symposium. I currently don't have any feedback, nothing skips when I walk or jump up and down in the room, and can tap my finger pretty hard on the plinth while a record is spinning and needle is in the groove and there isn't any sound (of the tapping) at all. Appreciate your input.

Dear Cerrot: the Ultra platform is directly on a VPI thick wood platform that has large leveling stainless steel cones , so I level the TT with them. Direct coupling the VPI makes it unsuspended and in this case it is a big improvement sonicaly over the VPI air feet suspension. I have tryed both ways and this is superior. I do use my stetoscope to eliminate any motor rumble, it is quiet, steady and external vibrationproof. A very important thing is to couple the underplatform with the wall with strong angle-iron . There shoudn't be any motion when pushing the platform sideways, especialy with wood floors. The pen tapping test on plinth and platter is dead silent too.
I have not tryed sand platforms but the VPI stand feet are filled with sand, this makes the whole thing about 150 Kg! I am working to replace the acrylic TNT plinth with a slate plinth ,...

Thanks for the feedback, Jloveys. I'll keep an eye on a used ultra platform. Thanks again.