@vinylzone , I really do not want to be a Pita. I think you did a great job building your own table. My intension was to suggest improvements no get into a battle.
Any vibration coming from the cartridge should be dissipated in the tonearm. Nothing should be getting to the plinth. Unfortunately, you have a unipivot arm which is much poorer at dissipating energy than an arm with fixed bearings. You have loads of noise getting to your cartridge. You could place the table on a MinusK stand but that is expensive. You can isolate the table on your own for much less money, a fun thing to do.
As for my turntable yes, I had a problem with feedback because of a resonance issue given the prodigious bass my system can produce and the location of the turntable. That resonance has been entirely mitigated with a simple modification. The turntable is now dead silent under any circumstance and nothing phases it including jumping up and down in front of it and charging into the cabinet it rests on. Given it's suspension, magnetic thrust bearing and isolated dust cover it is as quiet as a turntable can get. Speed deviation is no more than +- 2 thousandths of a revolution. At this very moment it is +- 1 thousandth going slowly back and forth between 33.334 and 33.335. As it is also a vacuum table most of the surface irregularities have been sucked out leaving only spindle hole eccentricity as a pitch modifier. With a concentric record pitch is delightfully stable. As good or better than any turntable made. Not bad for 15K. I also get a bunch of kudos for my finger joints. Life is good:-)
