Have had this experience with my Ariston 11-S, (like an old Linn) after I removed it from the wall. The other folks who responded are correct. It's the Floor. I put the TT on top of the Target turntable shelf,6 vibropods in the middle, and a black flakeboard shelf on the bottom. This vibropod sandwich rests on my stand. Results were good. I like the Granite Idea. Also, I installed 2 lollycolumms under the 40yr old woodfloor which really helped. Walking softly right in front of the stand also helps.
What is under your TT, cheap islolation?
I am looking for a way to isolate my turntable without using a shelf bolted to the wall. I am trying to save money while I re-configure the room. For now my turntable is on top of my stand but you have to tip toe around the room. I am wondering if a big rock iso platform (or DYI version) or some iso nodes under a butcher block would help with the bouncing turntable? I have two tables I am testing at the moment, one is a Thorens TD-160 & the other is a VPI HW19 MKII, both of them suspended. The floors are pretty sturdy, it is a dedicated room over my garage with serious supports built in to the floor.