Upgrade from TW Acustic Raven AC-3 to what?

I am familiar with the Final audio products - and with the Parthenon.
As for "timing" and speed control. My table runs with the big Studer Capstan motor with regulation and Studer speed control. This was good enough for the majority of the music recorded from the 1960ies to late 1990ies. So the stability of the "timing" on most of your records was determined by this very motor drive and its control board. I always found this a most suitable solution.
Especially so as it makes all other TT-motors look like lightweight dwarfs.

As for air-bearings ... well, there are air-bearings out there quite different to the ones "usually" seen in high-end audio. Its all a matter of "thinking in different scales".
And - its not just you being "sensitive to speed stability". Everyone with a remote interest in piano music will gladly join in.

Dover, what are the specifics of the motor and speed control? Low or high torque? AC or DC?

Response to Aoliviero

Motor is AC, large ( weighs around 10kg in gunmetal case ), driven by what is described as an oscilater preamplifier, this has sine/cosine outputs, feeding a power amp of which the outputs go back into the preamp and out to the AC motor. The controller has separate infinite speed adj for 33/45 and has a torque control so you can adjust it.

Dertonam

What turntable/arm/cartridge are you using. Is it the one you built yrs ago and described in various threads ?

Dover, my tonarm/cartridge is silver-wired FR-66s/B-60 w/FR-7fc special. I am currently re-designing my initial TT from the 1990ies. It will be finished late this winter. I will post pictures and a description when finished.

Dear Dertonearm, I hate to harp on this issue, but I have a "thing" about bad science, such as your contention that the mass of the slate is a major determinant of the distance that a billiard ball will travel (and your bogus reason for saying so). I have done some reading on the physics of billiards, as a result of my consternation. Two things emerge from my research: (1) Once the ball is struck, the major contribution of the table to the distance and direction in which it travels is the static and rolling friction between the ball and the felt, as I surmised in the first place, and (2) slate is used for billiard tables not for its high mass per unit volume but because it can be worked to achieve a very flat surface, and once made flat, the surface of slate is very stable as regards humidity and temperature, i.e., it does not warp. Here I offer a reference to a pretty nice article I found on the internet that reviews the Newtonian mechanics of billiards:

http://archive.ncsa.illinois.edu/Classes/MATH198/townsend/math.html

Now if you can concede that your metaphor is ill chosen, perhaps we can also open our minds to re-examine the idea that platter mass is the sine qua non of the highest end turntables. If I could find an article that addressed your other bald statements, that a certain platter mass is needed, regardless of the drive system, and that the dynamic mass of the Saskia platter does not count as "mass", I would post those too. I don't have the requisite experience to disagree; I just don't think you have the "data", even of the subjective kind, to back up those two notions. The only defendable fact here is that YOUR turntable, which is a belt drive of a certain type and construction, sounded best with a platter of a certain minimum (high) mass when auditioned by you and your colleagues. (I don't know whether you made measurements of frequency response or speed stability that could be adduced to strengthen your case as regards your turntable, but if you did, I would be interested to see same. I am assuming your conclusions are based on subjective listening tests.) Now I can go bang my head against the wall, because my favorite football team just once again pulled defeat from the jaws of victory.