Turntable speed accuracy

Dear Halcro, 'but the way many are discussing ...strobes (versus) Timeline...symply leaves me open-mouthed.'
You are suggesting the lack of intellect while it is about simple psychology. A phenomenon which can be observed in nearly any thread.

Regards,

Halcro,
I think you're on the wrong track ...
Simple physics dictates that speed must "swing" above and below 33 1/3 rpm in order to average out at 33 1/3. A speed change to below 33 1/3 HAS to occur first, before it can be detected and then corrected by applying more torque. If a drive mechanism does not "make up for lost time", the timeline laser would slowly, but constantly drift. The fact that these speed changes are very very small make it difficult to understand, but they have to be there in order to be corrected. Without any servo circuit measuring and correcting speed changes, the speed-torque curve of the electric motor would have to be a vertical line ... and there simply is no such thing.
You are right, it is very problematic to ceorrect speed in a way that our hearing tolerates it. The very high torque drive system of a Technics SP-10 MK3 or a JVC TT-101 sound much different from a low torque direct drive, but they both are able to maintain correct AVERAGE speed of 33 1/3 and the timeline laser will not show a differnce.

You're right of course Decibell.
The 'correction' to any stylus drag speed reduction is so instantaneous...that we cannot see it on the Timeline.
What I really meant to say was........once a speed shift has occurred....without any instaneous correction.....no turntable motor will 'speed up' to 'remove' that abberation over the course of a few revolutions and thus restore the Timeline laser to its mark on the wall?
Yet with a strobe.......all will seem to be runnIng perfectly immediately after a speed shift (or even during if you blink).

Your timeline device is averaging speed. It is not giving you an instantaneous reading. The laser pulses every 1.8 seconds. As long as the turntable achieves one revolution in 1.8 seconds, the laser spot remains stationary. Your turntable could be speeding up 25% and slowing down 25% in one revolution and the timeline will happily show a stationary spot on the wall as long as the platter rotation averages 1.8 seconds per turn. The best way to determine how your turntable is behaving is to look at speed real time. One way is some type of encoder with the output to an X-Y plotter. Another way is to play a record with a fixed frequency such as 3150 Hz. The inherent errors are 1) accuracy of the recorded frequency and 2) record runout. Using an FFT analyzer you can see any speed drift realtime. A good substitute is the iPhone app. It seems very good to me. It will show you your turntable wow and flutter real time and filters out the 0.5556Hz frequency caused by any record offset to the platter.
I would like to know if anyone's turntable wow and flutter measures less than 0.01% regardless of drive type.

If you take a look at one of the old brochures for the Denon DP80 (I think), they present an actual plot of instantaneous speed v time. The DP80 is not perfect in this graph, but Denon claim it was superior to the un-named competition. This is really just to say that the old guys understood and were able to graph this phenomenon.