Direct drive vs belt vs rim vs idler arm

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.

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.

It's not quite that bad. If your TT is 3' from the wall and your laser deviation is 1.5mm per revolution, your speed is off by 0.1Hz. 1.5 mm may be hard to see, but if you let it run for 10 revolutions and divide your total deviation by 10 you should be able to determine a 0.1Hz error pretty easily (if you have my Timeline Calculator Excel file that I posted about in this thread):

http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1327029459

The phone app sounds pretty cool, though. It is actually not just an iPhone app. I just discovered that you can get it for Android devices, too. I may have to try it out.