I had a problem with rumble and acoustic feedback,when playing vinyl, for years, after moving to a new house. I tried many tweaks, but most were unsuccessful. Vibrapods, sorbothane, rubber compressor mounts, inner tubes-you name it. I even built a wall mounted shelf, but still had problems (I'm on a suspended floor upstairs) The wall shelf was a good idea and it did "help", but didn't eliminate the problem. I bought some HEAVY DUTY springs, separated my shelf from actually attaching to the wall, by hanging the shelf with cables connected to eye bolts, in the front and back (forming a 90 angle in the back and a 45 degree angle in the front), then attached the springs to the underside of the shelf in the back. Connected the springs to some adjustable heavy duty nylon tie-downs and connected that end to the floor out from the shelf at a 45 degree angle. This way, I was able to pull the tie downs tight enough to where the shelf is essentially "floating" and isn't hard connected to the wall. I covered the cables with "armaflex" to help aesthetically. It was a project and a half, but it works great! If I had $3-5K for an isolation table, that would have been great, but with two turntables, my idea worked and cost considerably less.
