Vintage DD turntables. Are we living dangerously?

And the winner is .....

Belt drive Onedof turntable.

Richard - one final correction.
Halcro keeps posting the VPI Direct Drive raw graph.

10-16-15: Halcro
Here is the real time analogue print-out of the actual sinewave produced by the VPI Direct whilst tracking the 3150 Hz Test Tone.

Unfortunately the raw graph Halcro posts is in fact the Onedof turntable.

Here is the link to the original graphs -
VPI Direct & Onedof raw data graphs
Figure 2 is the VPI Direct raw data graph.
Figure 3 is the Onedof raw data graph.

Interesting to note that the smoothest raw data graph by a substantial margin is the Onedof TT with stretchy rubber belt drive and high mass platter.

Fremers testing and listening notes that the Onedof and Caliburn turntables have similar absolute results, but different shaped graphs They sound substantially different in character, perhaps the raw data graphs go partly to explain it. This of course is conjecture only.

*since the availability of the Feikert Speed App I have regularly stated that the Data downloaded on its 'Chart Info' was imprecise and non-scientific as it was not possible to duplicate the results from test to test.*

Why do we give credence to this in a magazine? Stereophile is Amateur Hour, unprofessional and lacking expertise. Too much trouble for them to conduct a proper test?
Read the specs page on the VPI Direct and all it has is the price.

I propose (without any data to back me up) that the tonearm has a lot of influence on the shape of the Feickert App speed deviations. I believe that unipivots are more easily excited by the 3D eccentricities of the records and thus show a more ragged perhaps more exaggerated trace. This belief is easily attributed to my dislike of most if not all unipivots but at the very least I think it safe to state that the w&f measurements are influenced by the tonearm and are therefore even less comparable from one table to the next.

Non-sequitur: I was at VPI yesterday and Harry Weisfeld is experimenting with adding additional pivot points to his 3D arms. Good idea.

Aigenga.
re unipivot arms.
You raise an interesting point, different arm bearings may well show a difference in the graphs. (Arm geometry may also show difference, as BT argues.)
That said, have any of the rigs recently listed by Halcro had unipivot arms?
The W&F visible on the raw data for the TT-101 seems to be quite similar from arm to arm. This would imply that the speed changes are localised in the drive unit itself.

I believe that Halcro posted three gimballed arms - the only unipivots that I noticed was the VPI on the Classic Direct. It showed a rather ragged trace.

I lean towards the idea that the regular speed changes on the Feickert traces are the results of record eccentricity; the fact that they occur once per rotation (16 - 17 per 30 second measured period) tells me that they reflect an out-of-round condition and are not due to speed correction feedback which would probably occur far more frequently.