Tapping on my table

Searched some threads and did not find an answer specific to my question, so I will try here.  My system is in my basement, which is a concrete slab with wall to wall carpet ( and carpet pad).  My TT is a Music Hall MMF 9.1 which has 3 plinths separated by sorbothane spacers.  The TT sits via its conical feet directly on a Salamander cabinet holding my amp and cd player plus some albums.  Total weight of the cabinet, equipment and albums is at least 150 lbs.  The TT weighs 40 lbs.

I have never experienced any issues with vibration, i.e when walking around while playing an lp.  I had assumed the concrete floor and thick carpet, along with the heft of the cabinet and contents, provided excellent isolation.  However,  this morning I inadvertently tapped the top of the cabinet while listening to an album and there was a very subtle but distinct thump emanating from the speaker.  Clearly the TT is not isolated from the cabinet even if the cabinet is isolating the TT from the floor.

Is there a good inexpensive solution to solve this isolation issue?  I do not want to lose the leveling benefit of the TT's feet - I have some Herbies cones under my cd player, but these would eliminate the leveling capability.