Direct drive vs belt vs rim vs idler arm

I noted the recommendation from Tonywinsc re the Dr Feikert Analogue iPhone/iPad free App....so promptly downloaded it onto my iPad and ordered the 10" Test disc from his Website.
HEREis the Frequency Plot from the Victor TT-101 Direct Drive deck and HEREare the Specs.
Note the almost perfect Mean Frequency Response against the recorded 3150Hz and the impressive .01% speed deviation.
Note also the impressive mirror-imaged sine wave plot positive and negative?
HEREis the corresponding Frequency Plot for the Raven AC-2. note the lack of symmetry above and below the mean line?
HEREis the corresponding Data for the Raven showing a less precise match to the 3150Hz Test Tone. This is the closest that the Raven Motor Controller allows me to get. Still not too bad?
The thing these Plots do not show however.....is that every time I do a new plot for the Raven AC.......it gives slightly different results whereas every Plot for the TT-101 is identical.

Whereas this information may have some value to the academic or scientist......I find the Timeline to be a better indicator of both short-term speed drift as well as long-term speed maintenance.
The only disparaging remarks about the Timeline I find....comes from those who don't own one....or those whose turntable performs poorly against one? :-)

Hi Halcro,
Thanks for uploading those pictures. It is exciting to see how different tables perform. First, note that the Raw Frequency plots are nearly the same on both tables as it should be. That is due to the eccentricty of the grooves to the center hole of the record. Is the Raven a belt drive table? I also see different results on my table (belt drive); but the numbers improve the longer I let my table run. Warm up time seems to be more critical for belt drive vs. your direct drive.
What is interesting too is that I see about a 5 second period in the filtered plots which is the same for my table. Since the period is 5 seconds, I would not call that motor cogging. I think it is the speed control circuits. The designers have probably purposefully put in long time constants to make sure the speed correction is slow and gentle so as not to be heard.

Hi Tony,
Yes....the Raven is belt-drive.
I'd appreciate it if you could explain to me what you can see in the different plots.....as I must admit....I'm not sure what to be looking for? :-)

I see variation about the setpoint which is normal. That is the speed control system working. The DD table has a funny pattern to it. Notice the two bumps and then a flat line in the speed plot? The DD table speed control seems to do a correction over about 10 seconds and then rest. Then the cycle repeats. The Raven on the other hand has a pretty constant cycle about the speed setpoint which is very similar to my table. Note that these corrections are within 0.01% to 0.02% of speed. Very fine control.
Also note that even if your speed is off by 0.1Hz, it will take 945 minutes of running time for your platter to gain/lose one rotation. Nothing against the timeline, just that your turntable would have to run for almost a day with the timeline to see how accurate it is. These plots show you results in a matter of seconds.

Note the almost perfect Mean Frequency Response against the recorded 3150Hz and the impressive .01% speed deviation.

It makes you wonder if you're measuring the speed stability of your turntable, the lathe that cut the test record, or both. Perhaps this is a benefit of the Timeline. Your measurements are not hindered by lathe inaccuracy. There has to be some lathe inaccuracy. If there wasn't, wouldn't we all be listening to records on lathes or turntable with record lathe type drives?

If your Timeline was 31" from a wall, a speed error of .01% would appear as a 0.02" (0.5mm) laser deviation per revolution.