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Old 13th September 2017, 01:01 PM   #411
davidsrsb is offline davidsrsb  Malaysia
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Quote:
Originally Posted by scott wurcer View Post
I should finish tomorrow and will put up a .pdf.
Can't wait
I took your old code listing and figured out what is happening. It runs straight away as Python3
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Old 13th September 2017, 02:31 PM   #412
Pano is offline Pano  United States
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Turntable speed stabilty
Good work all around! Pun intended.

I mention again that seeing this graphed as a percentage would very nice indeed. Not to hard to figure it from the frequency, but just having it on the graph would be superb.
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Old 13th September 2017, 02:47 PM   #413
fasterbyelan is online now fasterbyelan  United Kingdom
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Turntable speed stabilty
There is some great work happening here, keep it coming!

Quote:
Originally Posted by JP View Post
@luckythedog: I believe this is my best running MK3.

Dropbox - MK3_NE0AF10025_XG-7001_WF.wav
Hope no one minds but I processed the above sound file using the software I was given by the guy who used it on the Pink Fish Media Thread – see http://http://www.pinkfishmedia.net/forum/showthread.php?t=70027.

The polar plot does not give absolute values but as the software exaggerates any errors, such are readily apparent. The two FFT plots are, with respect to frequency, absolute values. The FFT Demodulated one was of particular use in sorting my Lenco out. I have also added an Audacity FFT plot of the sound file.

MK3_NE0AF10025_XG-7001_WF Polar.png

MK3_NE0AF10025_XG-7001_WF FFT Raw.png

MK3_NE0AF10025_XG-7001_WF FFT Demod.png

MK3_NE0AF10025_XG-7001_WF FFT Audacity.png

From my experience the results are very good and it would be hard to better. Only things to note are that the TT is running slightly slow (nominally 2996Hz (-.13%)), there is a slight peak at 16.5 Hz (which is apparent on LD’s FFT plot as well) and the Test LP is very slightly off centre (not a TT failing!!). It would be good to see a PlatterSpeed app result for this TT.

I hope this is of interest.

Regards,
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Old 13th September 2017, 03:00 PM   #414
Pyramid is offline Pyramid  United States
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Default A suggestion.....

Thanks to Scott for taking on this project and sharing his results!

If you plan to share the source code with the public, maybe you could split this off into a separate thread and make it an open source project? People could add to, or modify the program with enhancements, and after the field has tested and approved them, the OP (Scott) could update the first post with the latest (approved) version, so he would have document control of the project.
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Old 13th September 2017, 03:29 PM   #415
davidsrsb is offline davidsrsb  Malaysia
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Originally Posted by Pano View Post
I mention again that seeing this graphed as a percentage would very nice indeed
Its easy to calculate and display percentage rather than absolute frequency, but should this be against nominal or mean actual value?

I am suspecting that SP10 owners might be actually measuring the cutting lathe and the test record producers signal generator.

Creating accurate test signals in 1975 when HFS75 was released was expensive, these days we just run Audacity.
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Old 13th September 2017, 03:41 PM   #416
JP is online now JP  United States
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@davidsrsb, I've around a dozen test records. I'll try to record a few this weekend on the same 'table for comparison.
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Old 13th September 2017, 03:54 PM   #417
fasterbyelan is online now fasterbyelan  United Kingdom
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Quote:
Originally Posted by JP View Post
@davidsrsb, I've around a dozen test records. I'll try to record a few this weekend on the same 'table for comparison.
I used this record for checking TT speed recently for the first time -

download.jpg

It gave a frequency of 2938Hz on a DD TT which did surprise me (it should have been 3000Hz). Cross checking with other test records proved the lower frequency was due to the record and not the TT; I will not be using it again!
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Old 13th September 2017, 04:11 PM   #418
scott wurcer is online now scott wurcer  United States
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Turntable speed stabilty
Quote:
Originally Posted by davidsrsb View Post
Can't wait
I took your old code listing and figured out what is happening. It runs straight away as Python3
Ok here's the code in plain text format, I've commented it and removed any hard dependencies on sampling frequency so any sampling frequency should do the right thing. Also one last plot run on this exact code with file label added (compare to plot in post #346).

@ Pano that's a good idea and it would not be difficult, but a little work to get 3K, 3.15k, and even 1k to work as the base frequency.
Attached Images
File Type: jpg pplot.jpg (154.7 KB, 89 views)
Attached Files
File Type: txt polarplot.txt (2.7 KB, 42 views)
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Old 13th September 2017, 04:49 PM   #419
Pano is offline Pano  United States
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Turntable speed stabilty
Quote:
Originally Posted by davidsrsb View Post
Its easy to calculate and display percentage rather than absolute frequency, but should this be against nominal or mean actual value?
Good question - for which I don't have a good answer. Your thoughts?

Quote:
I am suspecting that SP10 owners might be actually measuring the cutting lathe and the test record producers signal generator.
Same thing I was thinking, you beat me to it. How good is the lathe and the cutting head, not to mention the generator? How can we know? Fortunately JP may provide the answer below.

Quote:
Originally Posted by JP View Post
@davidsrsb, I've around a dozen test records. I'll try to record a few this weekend on the same 'table for comparison.
A big step in the right direction. How difficult would it be to sort out the table artifacts from the LP artifacts? Anything that appears across all recordings should be TT specific, shouldn't it?
We did a similar test with record wear, George using a Shure cart at the beginning and end of the test run, with a Stanton in between. That worked well.
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Old 13th September 2017, 05:43 PM   #420
luckythedog is offline luckythedog  United Kingdom
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Quote:
Originally Posted by scott wurcer View Post
Ok here's the code in plain text forma
Thank you Scott, that's very tidy and results look excellent.

I'd guess that Python library function performance is, in practical terms here, at least as good as the one I came up with - and certainly more compact from a coding perspective ! So I think this outcome is, pragmatically, far more useful.

Though I doubt my algorithm is original, I'm very happy to see the Python library supporting a function that, in this application, appears to at least match performance. Next time, I'll look there first (!!)

Well done indeed, this takes the art forward !

LD
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