How to isolate turntable from footstep shake or vibration

As a general rule, I look for the simplest solution as it is also usually the least expensive.

As many others have noted here, set the table on a platform that’s bolted to the wall. It’s worked for me each time, both in my NYC loft (where I held many dance parties with up to 100 pairs of feet pounding the floor) and in my new home in Newburgh NY. before: vibration bad enough to sound like the woofer was going to rocket out of the cabinet. After: completely gone.

I apologize for being too harsh, Mijo. Was trying for humor. By the way, my OTL Atma-sphere amps originally used the high current Russian triodes (6C33C) designed for use in their jet fighters on board radar. This was deemed advisable because tubes are immune to nuclear blast emissions whereas SS is not. The US countered with an even higher current triode, the 7241, which until not so long ago was used in our own radar installations, at Andrew’s Air Force Base in MD, for one example. It may still be in use, for all I know. Anyway a few years ago I converted my amplifiers from the 6C 33C to the 7241. They are way more expensive and harder to find, but the sonic benefits seem worth the effort and expense.

Chakster, after I added a Velodyne 15” sub, my Altecs sounded much crisper at the low end and in the midrange, with improved stage imaging. 

FWIW I have a VPI TNT sitting on 4 hand balls, per the last of the VPI TNT suspension designs. It sits in a sandbox on a table, itself on a suspended floor. When I start hearing sound of walking on the floor, I know it’s time to change the handballs, about every 6 years. With new ones it’s quiet. I have a subwoofer that causes no problems whatever--and no high pass filter.

Since you probably have a different set-up, why am I relating this. Because it works so well that if I had a different TT I would get 3 or 4 flat pieces of wood, drill them out so that handballs could sit on them comfortably. Think Ginko.. And sit my TT right on them. Only other thing to do is to shim for level.  If the plinth didn't have sufficient weight, I would place it on a heavy cutting board and place the board on the balls.

Thick slab of Sorbothane foam sandwiched between two marble slabs