Is there any way to measure detailed parameters of a vinyl player?

[Richarrd]

I think it is difficult to measure this kind of product, and there is no clear clue for me. The first is, how to measure unique parameters such as wow and flutter? And for signal-to-noise ratio, etc. How to get more original data without the influence of the vinyl and needle itself? And how to generate the measurement signal in the most scientific way?

 

[MaxwellsEq]

I used to repair and setup turntables in studios.

Assuming you are considering a pivoting tonearm (linear tracking is different). The cartridge compliance needs to be correct for the arm mass to prevent extremes of resonance below 25Hz. Then the cartridge must be correctly aligned (usually) so that the cantilever is parallel to the record groove in two locations. Mostly this is done with a two point protractor.

Then you use a test record which has many test tones, frequency sweeps etc. with measuring equipment which can analyse wow and flutter, frequency response, distortion and crosstalk. The measuring gear used to be expensive, but now you can use a good but cheap ADC and free software.

 

[sergeauckland]

Test records are fine for comparative measurements, less good for absolute measurements, as the record's accuracy is unknown. In particular, built-in rumble and Wow & Flutter can be greater than that of the turntable one is trying to measure, especially if the centre hole is not accurately centred.

Frequency response also varies strongly with wear. Decca test records were guaranteed accurate above 10kHz for only 5 plays, as I recall. Albeit, that would have been with tracking weights much higher than the 1-3 gms of today.

Nevertheless, arm cartridge resonance can be easily checked, as can tracking ability. W&F and residual noise more of an issue, frequency response a bit of lottery.

S.

 

[somebodyelse]

Wow and flutter are usually measured by recording a single frequency tone from a test record and looking at variation of the frequency. This can be influenced by any eccentricity in the test record, or slack between pin and hole, although this is arguably still valid as it represents an issue common to all records. The frequency of change can give indications of the cause such as eccentricity on the platter, on the motor, or something belt or roller related. There are other methods like optical sensors and slotted or strobe discs, or more recently using accelerometers and/or gyros to measure rate of change of speed.

There are a couple of threads regarding cartridge measurements, how they are taken and what they mean:
https://www.audiosciencereview.com/...-cartridge-response-measurement-script.41148/ - details of a script used for analysis of frequency sweeps, including differences found between sweeps on different test records
https://www.audiosciencereview.com/...he-phono-cartridge-measurement-library.46108/ - results of this analysis for a range of cartridges, including tests of the same cartridge under different conditions, and of different examples of the same cartridge model giving some idea of sample to sample variations.

 

[MaxwellsEq]

Test records are fine for comparative measurements, less good for absolute measurements, as the record's accuracy is unknown. In particular, built-in rumble and Wow & Flutter can be greater than that of the turntable one is trying to measure, especially if the centre hole is not accurately centred.

Frequency response also varies strongly with wear. Decca test records were guaranteed accurate above 10kHz for only 5 plays, as I recall. Albeit, that would have been with tracking weights much higher than the 1-3 gms of today.

Nevertheless, arm cartridge resonance can be easily checked, as can tracking ability. W&F and residual noise more of an issue, frequency response a bit of lottery.

S.

You are absolutely correct - this is at best really measuring the test LP

In the cartridge script thread there are many discussions about which test records are good for a specific measurement.

 

[MaxwellsEq]

I would also add that LP playback is a dynamic mechanical system and therefore really quite complex.

 

[Richarrd]

I used to repair and setup turntables in studios.

Assuming you are considering a pivoting tonearm (linear tracking is different). The cartridge compliance needs to be correct for the arm mass to prevent extremes of resonance below 25Hz. Then the cartridge must be correctly aligned (usually) so that the cantilever is parallel to the record groove in two locations. Mostly this is done with a two point protractor.

Then you use a test record which has many test tones, frequency sweeps etc. with measuring equipment which can analyse wow and flutter, frequency response, distortion and crosstalk. The measuring gear used to be expensive, but now you can use a good but cheap ADC and free software.

What is the name of the free software you mentioned? It seems that REW can do a good job of frequency response and distortion, but the wow and flutter rate is a problem.

 

[Richarrd]

Wow and flutter are usually measured by recording a single frequency tone from a test record and looking at variation of the frequency. This can be influenced by any eccentricity in the test record, or slack between pin and hole, although this is arguably still valid as it represents an issue common to all records. The frequency of change can give indications of the cause such as eccentricity on the platter, on the motor, or something belt or roller related. There are other methods like optical sensors and slotted or strobe discs, or more recently using accelerometers and/or gyros to measure rate of change of speed.

There are a couple of threads regarding cartridge measurements, how they are taken and what they mean:
https://www.audiosciencereview.com/...-cartridge-response-measurement-script.41148/ - details of a script used for analysis of frequency sweeps, including differences found between sweeps on different test records
https://www.audiosciencereview.com/...he-phono-cartridge-measurement-library.46108/ - results of this analysis for a range of cartridges, including tests of the same cartridge under different conditions, and of different examples of the same cartridge model giving some idea of sample to sample variations.

Looks like a good py script, and a very good database! But it seems that after recording with ADC, using REW's input sweep recording can accomplish the same work? I tend to use REW to do most of the work

 

[Richarrd]

Test records are fine for comparative measurements, less good for absolute measurements, as the record's accuracy is unknown. In particular, built-in rumble and Wow & Flutter can be greater than that of the turntable one is trying to measure, especially if the centre hole is not accurately centred.

Frequency response also varies strongly with wear. Decca test records were guaranteed accurate above 10kHz for only 5 plays, as I recall. Albeit, that would have been with tracking weights much higher than the 1-3 gms of today.

Nevertheless, arm cartridge resonance can be easily checked, as can tracking ability. W&F and residual noise more of an issue, frequency response a bit of lottery.

S.

Thank you, I will pay special attention to these issues