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Wow, Flutter, W&F, weighted and unweighted, JIS/DIN/CCIR and NAB. Help me!

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restorer-john

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They are active.

So "reading rate" of 20 measurements per second and "1 reading rate" per second for the W&F utility?

@JPJ sent me polar plots of the individual files. Here is the 1% plot. At 1% the 3150Hz file should peak at 3181.5Hz and bottom out at 3118.8Hz and that is what @scott wurcer 's plot script and my meter are both showing. What am I missing? Is the "real time" function of the AP utility too short and it's getting skewed? Maybe the post processing function (if it has one) can bring the JIS numbers back in line with time integration.

1578449472439.png


The other two plots JPJ sent also correlate perfectly with the 0.1% and 0.3% files for upper and lower frequency points on the polar plot.
 
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scott wurcer

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So "reading rate" of 20 measurements per second and "1 reading rate" per second for the W&F utility?

@JPJ sent me polar plots of the individual files. Here is the 1% plot. At 1% the 3150Hz file should peak at 3181.5Hz and bottom out at 3118.8Hz and that is what @scott wurcer 's plot script and my meter are both showing. What am I missing? Is the "real time" function of the AP utility too short and it's getting skewed? Maybe the post processing function (if it has one) can bring the JIS numbers back in line with time integration.

View attachment 44965

The other two plots JPJ sent also correlate perfectly with the 0.1% and 0.3% files for upper and lower frequency points on the polar plot.

Not sure I can help, the script was intended to show revs of an LP and I see it's sort of been re-purposed but still gives the answer. One point to note is that what you view is a projection onto a 3D cone in 2D so a very eccentric LP looks like an ellipse rather than a circle due to this distortion. Not sure this matters here.
 

SIY

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I ran the DIN 3.15kHz 0.3% file using the MI setup and got numbers right on the nose.
DIN 0.3% unweighted MI.png
 
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restorer-john

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Not sure I can help, the script was intended to show revs of an LP and I see it's sort of been re-purposed but still gives the answer. One point to note is that what you view is a projection onto a 3D cone in 2D so a very eccentric LP looks like an ellipse rather than a circle due to this distortion. Not sure this matters here.

Thanks Scott. :)

So basically like looking down on the blue cone and orange ring from above.

1578468671766.png


Your polar plot sure looks beautiful when fed the digitally derived frequency modulated test tracks. I'd love to get a copy of it if it's available? I figure your plot would show +/-42.4Hz on the lobe ends for the 1% JIS flutter track?


First try with the JIS 3kHz track, I got 1.4% unweighted from MI. Not exactly the same, but reasonably close.

Maybe that JIS 1.4% reading from MI is a peak unweighted, whereas the track is RMS/Average weighted. That would account for the difference (/sqrt2).

It doesn't explain the AP's numbers, something is not right there.
 
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scott wurcer

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Thanks Scott. :)

So basically like looking down on the blue cone and orange ring from above.

View attachment 44989

Your polar plot sure looks beautiful when fed the digitally derived frequency modulated test tracks. I'd love to get a copy of it if it's available? I figure your plot would show +/-42.4Hz on the lobe ends for the 1% JIS flutter track?

Yes, a good TT does not deviate much so it's usually a nice circle. You're welcome to it, JPJ changed the cosmetics at little. You would have to change a few things for large deviations if the distortion gets too great. I also added a text tag for mean speed, don't know if that helps here because the mean is computed over one LP rev. Not sure what OS you use, a free Python distribution like Anaconda has all the libraries you need pre-installed.
 

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JP

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Ah, you’ve tweaked some things. Should put this on github or similar so people can always get the latest.
 

scott wurcer

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Ah, you’ve tweaked some things. Should put this on github or similar so people can always get the latest.
Fine, did you tweak the title and spacing of the degree tags? On mine the title and 0 degree tag start to overlap.
 

JP

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No, just the overall size, ability to choose scale, and the auto save.
 

scott wurcer

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OK changing the size could do that. For reference this is the intended application. The very inexpensive Uturn kickstarter turntable. You can start to see the 300RPM motor vibration transmitted through the belt (9 cycles per rev.). This is a 3kHz track from some spot frequency disk.
uturn.jpg
 

VIRTINS

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Maybe that JIS 1.4% reading from MI is a peak unweighted, whereas the track is RMS/Average weighted. That would account for the difference (/sqrt2).
You are absolutely right. :)

I was led here accidentally after typing "NAB wow and flutter" in Google Search. I searched this today because some MI users requested the support of weighted and unweighted RMS W & F defined by NAB/JIS. Currently MI only supports weighted and unweighted Peak W & F defined in AES6-2008 (r2012), which is also compatible with IEC 60386, IEEE Std-193, CCIR 409-2, and DIN 45507.

Strictly speaking, this "peak" value is not exactly the maximum value. It is a "peak" value determined through a so-called “2-Sigma” statistical method. In this method, the cumulative time for which the instantaneous frequency (speed) deviation exceeds the "peak" W & F is equal to 5% of the total time. Assuming the modulating signal is a sine wave, then "peak" W & F is sin(0.95*90 degree)= 99.7% of the real maximum value. Anyway, 99.7% is almost the same as 100%:), but this is a more robust method statistically if the modulating signal is not sinusoidal and contains noises.

Thanks for the standard WAV files. I have tested 3KHz NAB-JIS 0.1.wav as follows. The measured weighted peak flutter is 0.1407%, which is very close to the theoretical value: 0.1%*1.414*0.997=0.1410% of this calibration file. One trivial issue with this calibration file is that it contains a zero portion at the beginning and the end. These zeros need to be removed for a better measurement accuracy if the WAV file will be directly used for analysis, or they should not be sampled in the acquired data.

3kHzNAB-JIS0.1.png



The unweighted value is the same as the weighted value as the modulating frequency is 4 Hz. In the following figure, Ch.A (Blue) shows the original FM signal while Ch.B (red) shows the FM-demodulated signal (which is 4 Hz).

3kHzNAB-JIS0.1-Demodulated.png


BTW, the FM function of the signal generator in MI can be used to generate the calibration file as well.
 
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restorer-john

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Thanks for the standard WAV files. I have tested 3KHz NAB-JIS 0.1.wav as follows. The measured weighted peak flutter is 0.1407%, which is very close to the theoretical value: 0.1%*1.414*0.997=0.1410% of this calibration file.

That's excellent. Glad I could be of service. :) That not only confirms the official NAB test files are perfect, but also we have verification on both your MI and my dedicated W&F meter.

Maybe I should retire the W&F meter and half the other dedicated instruments on my bench and just use MI? I know SIY loves it too. ;)
 

Balle Clorin

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OK changing the size could do that. For reference this is the intended application. The very inexpensive Uturn kickstarter turntable. You can start to see the 300RPM motor vibration transmitted through the belt (9 cycles per rev.). This is a 3kHz track from some spot frequency disk.View attachment 45048
How did you create this plot?
 

scott wurcer

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How did you create this plot?

A Python script reading a 4 sec .wav file. The Anaconda Python install runs it turnkey, some Python distributions require the advanced math libs to be hand installed. The script is posted a few posts above.
 
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Frank Dernie

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Interesting measurements in the recent review of the Pro-ject debut Carbon Evo where a round section belt is supplied for use at 78rpm.
Round section belts are poor engineering practice (If I had designed something supposed to be with a round section belt when I was a young designer almost 50 years ago I would have been looking for another job.
Anyway the measurements show a speed error, not surprising since the round section belt changes the "gear ratio" but also very broad peak in the W&F measurement too, not a big surprise since a round section belt has stick-slip inevitably but bigger than I had expected. I had never seen measurements of flat and round section belt on the same TT on the same plot before.
There are a lot of TTs with round section belts and it has always surprised me - I would never buy one.
 

VIRTINS

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@JPJ, the file is 300s long and contains more than 2M samples. MI will refuse to calculate Wow and Flutter if the number of samples in the Oscilloscope exceeds 2M. I use [File]>[Extract] to extract the data in the first 40s and then analyze it and get the following weighted wow and flutter results.

WowAndFlutterWeighted101Hz.png
 
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JP

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Awesome, thanks! Where do I find the DDPs for RMS drift, wow, and flutter?
 
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