DIY TT

@vinylzone , nice work! I would like to make some suggestions. Hang the acrylic plinth from towers placed at the for corners. Depending on the mass distribution of the turntable you will probably have to use different rate springs at each corner the goal being for the plinth to bounce straight up and down at about two Hz. You can get an idea of the differential by putting a scale under each corner. Ten put the whole show under an acrylic dustcover. You can probably make the towers out of acrylic also. Could be a work of art. Look at and old Basis Debut or the Sota Millenium to get an idea. I don't want to be a PITA (yes I do) but you deserve a better arm.

@vinylzone , I hate to tell you this old man but that is a fallacy. Just like air sound travels through the ground in waves. As a truck rolls down your street your cartridge can hear that right through the concrete. Your cartridge can also hear a lot of other stuff like your washer machine being unbalance and your refrigerator compressor starting up. It can also hear your HiFi System. Does not matter what you have the turntable on certain frequencies will make it to the cartridge by direct mechanical means or through the air. All this is distortion.

Towards the end of this demonstration there is an example of house rumble. Watch it! 

@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:-)  

@holmz , you really can't take a Sota apart. The cover (that is what Sota calls it) has the three feet attached to it and the sub chassis which has the main bearing and tonearm board is suspending inside from 4 damped springs. In all but the Cosmos the sub chassis are MDF and composites and not very attractive. The Cosmos sub chassis is machined from billet aluminum and is very cool looking but I still would not use it without a proper suspension. The Sota suspensions are precisely tuned for a certain mass which is why Sota makes specific weight tonearm boards for various weight arms. Some arms like the Kuzma 4 point11 are just too heavy for it. David Fletcher, the original designer of the Sota did not even consider anything larger than a 9-10 inch arm because as @rauliruegas has mention, given the physics involved it is silly to do so. 12" arms are bad news regardless of what anybody thinks they hear. I would trust the science way before anyone's hearing. Unless you want to buy a Dohmann Helix one, the best way to have a second tonearm is just get another Sota. You can get 6 of them for the price of one Dohmann:-)

@holmz , The new Sota bearing is just like the Clearadio. It has a magnetic thrust mechanism. The female section of the bearing is an integral part of the platter so what you are talking about is a new platter assembly which is heavier than what you currently have and the suspension will sag and it's resonance frequency drop.

You are best off sending the table back to Sota and let them upgrade it for you or just trade it in on a new Sapphire Eclipse. You might as well add vacuum clamping while you are at it. As far as multiple arms are concerned if you get additional; tonearm boards weighted for any specific arm you can have several arms mounted up and fully aligned then changing arms is a snap. Three Allen cap screws is all you have to undo. I can change arms in less than five minutes. I am contemplating getting a wood CB directly from Frank Schroder and doing just that. 

@lewm , it is interesting that the DP80 and Sota both read a trigger under the platter to gauge speed. In the Sota's case it is a small magnet. The controller's response is different. The Denon makes an immediate adjustment while the Sota makes its speed changes very slowly. The MinusK is full of springs by the way.