How to isolate turntable from footstep shake or vibration

Shock/vibration isolation of avionics is documented and easily accessed - examples  Microsoft Word - avioinics_iso_revC.doc (vibrationdata.com), and compressed_PC6116_AerospaceandDefenseIsolatorCatalog.pdf (lord.com).  Exactly what shock & vibration performance the avionics has to survive can be classified.

@atmasphere,

in my prior post I should have gone into greater detail, but for the OP, when the floor bounced in the upward direction, the turntable spring went into compression.  But because the spring was not stiff enough the spring fully compressed at which point the 'suspension' essentially bottoms-out and now there is no suspension and the force is transmitted directly to the table. 

In your circumstance, I suspect that the floor is resilient/soft enough that foot fall causes a ripple effect which then has vertical force component and a horizontal force component.   Use of ball bearings to absorb horizontal vibration is well documented; ergo, they worked for you. These vibration reducers originally were developed for audio use - Vistek - Designing with Series 320 Vibration Isolation Bearings (newport.com).

Mijo, Mijo, Mijo. You consistently mistake your own observations and opinions for science and facts. Tubes are microphonic, some more than others, and most tube gear does benefit from isolation and dampening. Not necessarily with spring suspension. Like I said, some guys even isolate, suspend, or dampen their solid-state gear, although the rationale for that is perhaps less obvious. If you ever looked inside a Halcro preamplifier, for one example, you would see that the entire printed circuit board has been sprayed with a rubbery coating to dampen vibration of the individual components. And that is solid state to the utmost.

I endorse the use of wall racks.  I used a target rack for years in several different rooms, and holding a Linn Sondek.  Never ever a trace of footfall.

D.J.’s from the past were used ash trays with rubber bands wrapped around them. Not insinuating that you are a DJ or a smoker but surely you get the idea. 

Pleased that you got the problem sorted...