Nude Turntable Project

Perhaps you should try an air suspension shelf (see Albert Porter's system thread) or a spring loaded turntable shelf, like the Symposium Isis. I believe either of these would solve the acoustic feedback problem. The new cradle looks really nice!

Henry, are you sure the feedback comes through the shelf? Could it be airborne direct to the cartridge?

It cannot be air-borne feedback Aigenga....
The stylus is in the groove with the turntable motionless and no music coming through the speakers.
When I turn the volume up to a very high level...a low frequency drone begins and then increases in volume without further manual volume input.
The feedback begins when the room is in silence...🔇

Henry,
I suspect the coupling - 3 rubber grommets are the root of this evil. It won't matter how much mass or how stable the base is, if the coupling is inadequate.

Can't say I have a solution, but I'd try something like a thin bead of silicon caulk, or possibly the sealer they use to couple a speaker driver to a cabinet. I wonder what Mosin uses to couple Saskia to the slate plinth.

Regards,

Now that I see your last post, what you're describing is a low frequency oscillation (gets louder). If the stylus is stationary, does this originate in the table or preamp?