Fun with vinyl measurements

[Ferran melero]

Anyone with a smartphone can do a RPM check. While my strobedisk is very stable at correct speed i get +0.24% on the app . The app also show similar w&f variations a recording of A test record.

Anyone with a smartphone can do a RPM check. While my strobedisk is very stable at correct speed i get +0.24% on the app . The app also show similar w&f variations a recording of A test record.

 

[Ferran melero]

Anyone with a smartphone can do a RPM check. While my strobedisk is very stable at correct speed i get +0.24% on the app . The app also show similar w&f variations a recording of A test record.

Anyone with a smartphone can do a RPM check. While my strobedisk is very stable at correct speed i get +0.24% on the app . The app also show similar w&f variations a recording of A test record.

 

[alvaro-oliver]

In the contrary, hardly any modern TT is good enough, except Technics.. but some new Technics has a platter run out problem . My best TT on W&F is a vintage Denon 51F that is refurbished. My Fisher MT-6330 turns out to be good too , but is extremely sensitive to weight imbalance- phone or Shaknspin placement disturb the levelling of the suspension which affects the drive signal-low torque drive probably sensitive to drag too..
View attachment 466138
Fisher with good balance.

That depends on what you consider 'good enough.' I was thinking more along the lines of figures below 0.1% weighted wow and flutter, which is what a Hanpin super-OEM promises and delivers. I have no doubt that better-engineered players, whether from today or 50 years ago, will yield much better results.

Interesting what you mentioned about the effect of imbalance on suspended chassis — definitely an important point to keep in mind.

 

[Balle Clorin]

If we look at this review we find that 0.1 % DIN WF relates to 0.27 peak variation which puts the TT in the worst 5% in my 40TT measurement collection.I have no problem hearing wow at this level ..
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Regarding audible or not..

Analysis: 0.5% wow and 0.2% W&F DIN is clearly audible befor correction, after correction it is less than half , judge audibility yourself . JIS WRMS numbers will be even lower maybe 0.12-0.14%.

 

[alvaro-oliver]

Thanks. It's the gyro integration that I'm interested in along with any supporting and analysis code.

FG on what I use is very easy to acquire as most of the upper-end Technics have a buffered signal available on a diagnostic port. Analysis it can be a different matter due to the low frequency.

I think I can help you with that. You can use my capture and analysis script just for the gyroscope data if that’s what you need. Regarding the FG signal, any source that outputs pulses of 50 Hz or more can be used for wow and flutter analysis, and it’s worth integrating it as a reference signal. This signal should be the closest to the truth.

Interesting what you mentioned about the diagnostic port on high end Technics turntables — my SL-1600MK2 doesn’t have it, but I was able to identify the FG signal and was about to tap into it. However, I decided not to intervene and ended up buying a turntable I wouldn’t mind modifying: a Reloop RP-4000, which has detailed documentation of its electronics. My next step is to modify the pitch control, replacing the manual fader with a controllable signal to generate artificial wow and flutter. If everything goes well, I should be able to generate different percentages of W&F within the frequency range allowed by the Reloop’s torque (ideally from 0.1 to 10 Hz). That way, I’ll be able to verify whether the gyroscope’s response is linear across the generated magnitude and frequency ranges.

 

[alvaro-oliver]

If we look at this review we find that 0.1 % DIN WF relates to 0.27 peak variation which puts the TT in the worst 5% in my 40TT measurement collection.I have no problem hearing wow at this level ..
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View attachment 466223


Regarding audible or not..

Analysis: 0.5% wow and 0.2% W&F DIN is clearly audible befor correction, after correction it is less than half , judge audibility yourself . JIS WRMS numbers will be even lower maybe 0.12-0.14%.

Yes, I can clearly hear the modulation in the video. Thanks for putting the figures into context. you clearly have a huge amount of testing hours across multiple systems that give you that perspective. You’ll understand that, having only two systems to test with, my view of what’s 'a lot' or 'a little' is very biased.

On a separate note, how on earth do they manage to keep that device fixed while the platter is spinning in the video? If you attach an optical decoder, you could measure speed and wow & flutter with incredible detail and precision.

 

[Balle Clorin]

Not sure how they do it.The device has been on sale with a local high end dealer at 50% discount for a year, still too expensive for me and others too. It would sureeky be a bigger improvement than buying a cartridge for the same price…

It would probably upset my suspension turntable, too

 

[morillon]

on discs with this type of major defect... the interest is rather obvious... the subject had already been addressed in a commercial manner a long time ago with the Nakamichi turntable
;-)

 

[Thomas_A]

If nessecary, I use my eyes and a manual "nudge" which works with a felt mat. Not perfect, but at least it gets better.

 

[alvaro-oliver]

What a cool and expensive gadget!

 

[Thomas_A]

What do these centering devices measure? It's sits over the spindle but needs to measure the LP track.

I once saw another DIY solution where the speed was modulated instead (measuring the tonearm movement). It really took care of the wow, but it is a poorer solution vs. centering.

 

[alvaro-oliver]

I’m not sure I get your point, Ferran. If it’s about the quote on measuring RPM with smartphones, I wouldn’t really recommend it. at least not without some kind of calibration. From what I’ve seen, the static offset of gyroscopes changes quite a bit depending on the tilt of the sensor (not its position relative to the center), and some models have noticeable thermal drift that can mess with measurements longer than 20 seconds. During testing, it’s rare to see the speed measured by the gyroscope consistently match other methods.
Now, for wow and flutter it’s a different story. In that case, what matters are the dynamic characteristics of the rotation, and that’s where these sensors really shine.

To measure RPM accurately, the first option I would recommend is the FG signal, as long as the turntable has one. The second-best would be a Hall sensor or an optical detector connected to a frequency counter. With that setup, you can measure absolute speed per revolution with a precision of around ±0.0001 RPM or better, depending on the crystal oscillator in the microcontroller.

 

[dennis h]

What do these centering devices measure? It's sits over the spindle but needs to measure the LP track.

I once saw another DIY solution where the speed was modulated instead (measuring the tonearm movement). It really took care of the wow, but it is a poorer solution vs. centering.

https://ds-audio-w.biz/cms/wp-content/uploads/2025/05/ES-002-Catalog_compressed.pdf

https://ds-audio-w.biz/cms/wp-content/uploads/2025/05/ES-002_Instruction-manual_250709_compressed.pdf

they don't explain it all...

 

[Balle Clorin]

A poor mans ShaknSpin.. many thanks to @Luca Sorrentino for pointing me to the the phone app!
1. Using the Iphone app PhyPhox to extract gyroscope data from the phone in spinning turntable, send CSV file to your PC&Excel via email. Make sure to have minimum 25 seconds of speed data or script will fail. Use the Z axis gyro data and make an excel column to calculate the variation from average value ( rpm_deviation.txt rename to csv) in%.
2.Run scrip below to generate wav file from variation data ( rename rpm-dev-to-wav.txt to .py)
3. Script makes a wav file that can be analyzed in Multitone LP tab
4 run Multitone

Below is my Denon 51F measured by Iphone gyro with this method
Use at own risk, I had AI CoPilot to generate the script for me

EDIT: data form a 50second run gives better resolution on FFT in Excel. Now I inly hav to fiure out why the DIN W&F in excel deviates.. 0.051 vs 0.035 a factor of 0.7 look suspiciously like 1/SQRT(2).. I do this to sum the w&F FFT values after weighing..= SQRT( SUMPRODUCT( BS10:BS3700 ^ 2 ) / 2 )

 

[dougi]

Same cart, same supposed load cap, different phono stages

A bit puzzled by the difference in HF bump on my AT VMx745ML compared with some others over on the measurement library thread, I remeasured it using my Project phono box DS2, which says its 'no cap' setting is about 50pF. Which the PA Waxwing is supposedly as well. Comparison below. Waxwing blue. The Project has even more of a hump, suggesting even more capacitance than the Waxwing! Amir's measurements of the otherwise similar Project DS2 USB suggest the HF is flat. What is going on I wonder? I guess I could measure the response of the DS2.

 

[Balle Clorin]

@dougi , Any chance you can do the same comparison with a 2M cartridge?

You could add a dummy capacitance to the waxwing by a simple RCA T splitter and tune till you find the difference

I have observed something similar , that is the way I found out I had to remove 2 protection diodes that some Puffins had for a while. Shannon Parks at Park Audio guided me through the simple surgery, popping off the diodes on the circuit board

 

[Thomas_A]

Same cart, same supposed load cap, different phono stages

A bit puzzled by the difference in HF bump on my AT VMx745ML compared with some others over on the measurement library thread, I remeasured it using my Project phono box DS2, which says its 'no cap' setting is about 50pF. Which the PA Waxwing is supposedly as well. Comparison below. Waxwing blue. The Project has even more of a hump, suggesting even more capacitance than the Waxwing! Amir's measurements of the otherwise similar Project DS2 USB suggest the HF is flat. What is going on I wonder? I guess I could measure the response of the DS2.

View attachment 469329

A bit odd. I do not see any evident shift in f just level. Which is indicative of different R.

 

[narud]

im finding that the new audio technica 45xml styli are super reactive to temperature. when my house gets hot/humid, the high end peak gets way larger. ive never experienced this with any of my other carts, or with previous audio technica styli.

regular room temp

warm/humid

 

[dlaloum]

There has been talk for years of variance due to the suspension being affected by temperature... this is the first time I have seen it measured!

And of course it is completely dependent on the properties of the suspension material... which vary a heck of a lot, and often even vary within a brand over a short period of time.

The ADC XLM family of cartridges had some wildly varying suspension material formulations... some of which had a tendency to fail within a year of being issued... (which accelerated subsequent changes!)

 

[melloncolliecat]

How much hotter and more humid than usual?