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Help me interpret this wow and flutter measurement for a cheap turntable

onlyconnect

pfm Member
Using a simple measurement app. I recorded a 3150 Hz test tone using line in to a digital recorder then played it back in front of a microphone. I'm thinking that the quality of the mic would not make much difference to the measurement in this case? But I don't fully understand the results. What might the Range setting do? Is it saying that the worst result in the last 10 seconds was 0.2536% and the max in the session 0.495% Which would place it as poor but not absolutely dreadful?

wow1.png


Tim
 
I'm not at all sure what your analysis software is doing. Nor why you transferred it via playback and a mic. (?) But as a guess, your plot shows the turntable is running about 0.2% slow. So any W&F measurement would need to take that into account. Also not clear what the 'samples' means so have no idea of the duration plotted.

And if the mic-speaker spacing varied, that would cause changes in the result.

To get good results you need an ADC or be able to copy the recording via a digital file.
 
I'm not at all sure what your analysis software is doing. Nor why you transferred it via playback and a mic. (?) But as a guess, your plot shows the turntable is running about 0.2% slow. So any W&F measurement would need to take that into account. Also not clear what the 'samples' means so have no idea of the duration plotted.

And if the mic-speaker spacing varied, that would cause changes in the result.

To get good results you need an ADC or be able to copy the recording via a digital file.

Reasons for the above: the app doesn't seem to accept a file, only microphone input. So I recorded to a file, then played it back in front of a mic. Whereas with your app I simply processed the file.

Tim
 
Here is my output from your app (saw other thread!) This is based on the file from the ADC.

jimwow.png

Id need to check the calibration to be sure, so I may be wrong here. But IIRC that implies a W&F of almost +/- 1 percent peak for the unfiltered value. (The smaller plot is AES weighted which isn't the same as DIN.)

The spikes are probably clicks. They'll make the measured values bigger so it is a good idea to 'repair' them with the audiacity tool/effect of that name, or find a section of the disk without clicks.
 
Reasons for the above: the app doesn't seem to accept a file, only microphone input. So I recorded to a file, then played it back in front of a mic. Whereas with your app I simply processed the file.

Tim

I guess from that your computer doesn't have a 'line' input? I don't use Windows, but Linux usually lets you specify the input for a program, but maybe your computer has no line input.
 
I guess from that your computer doesn't have a 'line' input? I don't use Windows, but Linux usually lets you specify the input for a program, but maybe your computer has no line input.

There's a line input. But the "Software wow and flutter meter" app only supports microphone input as far as I can see. You can't select a line input.

Tim
 
Id need to check the calibration to be sure, so I may be wrong here. But IIRC that implies a W&F of almost +/- 1 percent peak for the unfiltered value. (The smaller plot is AES weighted which isn't the same as DIN.)

The spikes are probably clicks. They'll make the measured values bigger so it is a good idea to 'repair' them with the audiacity tool/effect of that name, or find a section of the disk without clicks.

Thanks. I don't think they are clicks (Audacity doesn't find any). I think it is actually speed variation! Worse than I thought. The spec of the turntable is "less than 0.3%" for W&F.

Tim
 
1.5%, say peak-to-peak% means about 0.75% peak (with any dc removed), so weighted rms might well be well below 0.5%. Matter of details I can't easy see from the plot. Speed variations that big and short-term seem a bit weird to me. I suspect the clicks may be smaller than you think, or be 'missed samples' due to some kind of timing error.

Can you put up a copy of the audio recording somewhere?
 
1.5%, say peak-to-peak% means about 0.75% peak (with any dc removed), so weighted rms might well be well below 0.5%. Matter of details I can't easy see from the plot. Speed variations that big and short-term seem a bit weird to me. I suspect the clicks may be smaller than you think, or be 'missed samples' due to some kind of timing error.

Can you put up a copy of the audio recording somewhere?

Sure.

https://1drv.ms/u/s!AmGw_gRig37VjLNPVoCNjoZihTe3Yg

Tim
 
Wow, massive difference! What is your usual turntable? You can use Audacity's scale zoom function to get a better idea of its performance. Which test disc are you playing?
 


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