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Old 14th September 2008, 12:44 AM   #1
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Default how to? simple wow/flutter measurement

I'm working on some turntable drive systems. I need to measure how they perform: does anyone know of some public domain software that can extract a wow/flutter figure from say a recorded wave file, or even give real time wow/flutter figures from a test tone injected into a PC sound card?
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Old 19th September 2008, 04:06 PM   #2
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I think Audiomatica CLIO offers the ability to measure wow & flutter as an option, but it is rather expensive.

You might have better luck finding an old W&F meter on eBay or building one.
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Old 21st September 2008, 04:29 PM   #3
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On this page New power supply you can read a method for measuring wow and flutter.

It won't give you values to compare with measurements made in another way, but it will give you values which you can compare with earlier measurements to see if you're improving on things.

"Official" wow and flutter measurements depend heavily on standards and protocols which will prove very difficult to engineer yourself.

greetings, MArco
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Old 21st September 2008, 06:45 PM   #4
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Thanks for the suggestions, but no-one seems to have done what I need.
I guess I will have to write my own software to do it!
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Old 23rd September 2008, 08:05 PM   #5
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Hi Steerpike,

I am also very interested in doing this but in the past didn’t found anything ready made for it for free. Here is some software that does it. It comes complete with a test record but it is huge expensive:

http://www.adjustplus.de/

(If you can read German)

To do it you need a test record with a pure sine tone (usually 3 kHz) and a FM-demodulator for extracting the deviation from the test tone.

In the past I did it with Spectrum Lab for the FM-demodulation and fed the output to a FFT analysing program. Spectrum Lab is free and can be found here:

http://freenet-homepage.de/dl4yhf/spectra1.html

Cheers
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Old 24th September 2008, 12:45 PM   #6
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Hi Pjotr

It's seems odd that no-one had done it, since a desktop computer is so ideally suited to it!

I do have a test disc, but for those who DON'T have, it would be also possible to print a disc - like a strobe disc - and pick off the frequency optically with a photodiode (or a pair of photodiodes for more accuracy)

That Spectrum lab might be just what I need - thanls for the link.

Otherwise, maybe a simple analogue PLL circuit to detect the FM component, and then do the A/D conversion.
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Old 24th September 2008, 05:07 PM   #7
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Here a result I got with Spectrum Lab with a 1 kHz test tone from a Cardas test record. TT was a Transrotor Fat Bob with a SME series-V arm. Cart was a Benz ACE. The TR is one of the most sturdy TT’s with regard to speed stability. What you see is the difference of the FB equipped with (green) and without (orange) their advertised TDM bearing.

Clearly visible is the 50 Hz torque ripple from the synchronous AC motor. Also you can see the 0.55 Hz spike from the not perfect centricity of the test record.

The cause of the other spikes below 50 Hz I don’t know…..

Cheers
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Old 24th September 2008, 06:54 PM   #8
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I have downloaded several of the software tools from your link - even if they don't do the Wow & flutter thing exactly as I want, they are going to be VERY interesting and useful analysis tool, so THANK YOU for pointing them out!!!
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Old 24th September 2008, 07:20 PM   #9
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Ok good luck Steerpike

To give the levels an absolute meaning you can make a reference signal: Say a 3 kHz test tone FM-modulated with 0.1% deviation. This will give you then a reference level. You can make this with the build-in signal generator of Spectrum Lab itself.

My previous post was just to show how deep you can measure with a soundcard, a test record and some free software.

And yes, it is big fun!
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Old 24th September 2008, 08:49 PM   #10
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Quote:
Here a result I got with Spectrum Lab with a 1 kHz test tone from a Cardas test record. TT was a Transrotor Fat Bob with a SME series-V arm. Cart was a Benz ACE. The TR is one of the most sturdy TT’s with regard to speed stability. What you see is the difference of the FB equipped with (green) and without (orange) their advertised TDM bearing. Clearly visible is the 50 Hz torque ripple from the synchronous AC motor. Also you can see the 0.55 Hz spike from the not perfect centricity of the test record.
Very nice work. Can you please explain how you obtained this graph with the mentioned software?

Thanks, MArco
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