Direct drive vs belt vs rim vs idler arm

Dear Dover, That was a nice post. But as regards your "old" Sota Star, I had a different experience with my old SOTA Star Sapphire Series III. I owned it from about 1990 to the late 1990s. This was the turntable that made me a believer in the potential deficiencies of belt drive. I could easily hear the pitch instability, particularly on jazz and classical piano LPs. For all that time, I put up with it, because I thought that the distortion I was hearing was on the master tape from which the LPs were made. (There was no internet in those years to tell me I was wrong.) Then I bought a Nottingham Hyperspace, which is not too different from the SS in design philosophy but is worlds better in its accuracy of reproduction of piano music, i.e., pitch stable, elastic belt drive notwithstanding. When I added a Walker Precision Motor Controller to the Hyperspace rig, everything went up a notch further; the Walker made a huge improvement in what I already liked quite a bit. These experiences led me to begin to appreciate the importance of drive mechanisms and the proper job of a turntable. I hasten to add that, from what I have gleaned second hand, the modern SOTA turntables are also much improved over my old Star Sapphire. I mean no slur on their current products.

Yes, the modern Sota uses an AC motor and electronic power supply in lieu of the previous DC motor. My Cosmos IV seems dead on, and since the motor is mounted to the same suspended sub assembly as the platter and arm, there is no movement between them, unlike most suspended tables where the motor is fixed and the platter/arm is suspended.

Still no comment on my interpretation of the Fat Bob's video after dropping the cartridge?

Lewm - same experience, but from the motor & power supply mods we did, the cogging in the early motors on the SOTA was significant. According to our tech the "cogging" was induced by shortcomings with the power supply regulation on the papst motor board, not the traditional cogging as in poles/slot rotation of the motor itself. That being said, the motor/platter should be rigidly coupled for stability, and obviously SOTA addressed this issue later by mounting the motor on the same chassis as the platter & arm.
After the SOTA I temporarily used a Townsend Rock with the ET2 and the stability of the fixed plinth design was apparent, despite the sloppy build quality of the early Townsend.

I don't think "cogging" had anything to do with the wavering pitch of my old SS Sapphire. Possibly the mounting of the motor on the plinth whilst the bearing and platter were suspended did have something to do with it. I think that cogging, if indeed it is audible at all in any well designed TT motor, would give a "regularly regular" type of distortion and would probably not affect pitch so obviously. I actually heretofore thought that what I heard with my Sota was due to the old stylus drag/belt stretch bugaboo, but that's just an unsubstantiated guess.

Interesting to note that the original AR turntable, which I used for years, also had the motor mounted on solid ground and the platter suspended. Yet it is touted as a "classic". I can't even remember whether it gave an accurate rendition of piano notes.

Lewm - the "cogging" mostly showed up as instability, most apparent in the bottom end. This was cleaned up with the updated power supply & on board regulation. This was consistant across many SOTA's we sold at the time. Sounds like you had a different issue.