Turntable speed accuracy

Hi Peter,

I updated my calculations and also found an error. My previous calcs were off by 100 because I had calculated a % and then used that for an absolute. The correct numbers now with your measurements are speed is fast by 0.003%. The 5.2 minutes of playing time were off by 0.0059 rotations out of 173.33. (That 100 makes a big diff in the numbers). Drift to the left means slow? Ok, I see that now too.

Thank you Tony. So, if I understand you correctly, my table is slow by roughly 6/1000th of a rotation out of 173 rotations or 0.0000346 per rotation. Said another way, 0.003% slow is 0.00003 RPM slow. So my table in this video is running at 33.3333333-0.00003 = 33.333303 RPM. Is that correct?

The precision of the Sutherland TimeLine is such that is can clearly show this deviation. I'm sure that SME and most other designers do not use such fine measuring tools when testing the results of their designs. I've mentioned elsewhere that my turntable shows correct speed while using both the KAB strobe and the paper disk supplied with the turntable.

I am perfectly satisfied with setting the speed with the KAB. But this experiment with the TimeLine has been very informative. The motor controller increments are course enough to be detected by the TimeLine. I've tested the number of increments I can hear, and it is somewhere between 4-5, either too fast or too slow. I can not detect by listening a variation of 1-3 increments on the motor controller in either direction. Perhaps others with perfect pitch could hear this.

The new TechDas turntable has "passed the TimeLine test." It would be interesting to see that video and the video results of other tables which have different drive types using a similar methodology to my and Halcro's test.
I have heard of some tables showing even better results, but without video documentation.

Hi Tony,

The TimeLine device that I borrowed from Albert Porter is the older model. The new/current one has, I think, six strobe lights/flashes spread equidistant around its perimeter. I know it is different in some meaningful way.

It would also be interesting if the duration of the strobe itself would be quicker on and off. Then the strobe slash or line on the wall would be of shorter length. As it is now, because the device is rotating on the platter, the length of time that the light is on smears what would be a dot into what appears to be a line. This is consistent with my observation that the further away the wall is from the spindle, the longer is the strobe line/slash.

It is an incredibly interesting device and I think one could study what happens to the line with a slow speed camera and thus detect different behavior between belt drive and DD tables during the moment of flash, i.e. during very short durations, and perhaps detect visually deviations of speed consistency. Some listeners claim to hear this earlier in this thread.

If you look closely at Halcro's video, the strobe line looks different than it does on my video and the quality of my line changes slightly during the course of my video. So something else is going on.

As was mentioned earlier in this thread, there is also a distinction to be made between speed accuracy and speed consistency. I agree with those who think the latter is more easily heard.

Peter,
Having extra flashes would not necessarily be more accurate or enable small period variations to be seen. That would depend on the indexing accuracy of the machine used to make the multi flash Timeline. A typical Rotary Head might be a factor of 10 less accurate than the performance of your deck in percentage terms as shown above, and certainly less than the clock in the Timeline.

John
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