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Fun with vinyl measurements

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Balle Clorin

Balle Clorin

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Here is a turntable noise feedback test. Playing a REW full range Pink noise signal at 82db at turntable. And recording Clearaudio testrecord track 3150hz .
As I wrote before , in my case playing with the turntable cover on is not a good idea, mor feedback and resonances break through to the player/cartridge
1668251855207.png






Test with cartridge stationary in record groove and blue overlay with TT spinning 3150Hz track
1668252737614.png
 

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Thomas_A

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A very odd result I would say. What is the physical reason for the peaks found? They must relate to some acoustic waves hitting the record, arm or fundament.
 
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Balle Clorin

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Dont know, I was puzzled <30hz peaks on a stationary record and silence. Some building vibrations? Elevator, ventilation , refrigerator , traffic? . In the case of spinning record the test records are rarely perfect, both noise and spurious frequencies and rumble can occur.
 

Thomas_A

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I can only relate to that your cover transmit vibrations to the fundament. Did you try soft feet under the cover corners?

You should also see some effects of room acoustics - sound waves between the record surface and roof. This would give you peaks of vibration above noise floor. Do you get the same using a high volume sine sweep trough the loudspeakers?
 
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Balle Clorin

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Not done sine sweep yet. But redid the stationary test, when stylus is resting on platter -in silent room -it picks up vibrations below 30Hz. at -67db

1668266530443.png
 

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Here is a turntable noise feedback test. Playing a REW full range Pink noise signal at 82db at turntable.
I apologize if it is obvious, but can you explain what you mean by this or rather how you do this?
 
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Balle Clorin

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I play pink noise on my stereo through the loadspeakers. Volume is 82dB C, at the turntable using my RadioShack digital readout dB meter. At the same time I let the pickup rest on a record on my turntable, and record via the RIAA to PC (Optical out from Park Audio Puffin). That way the recoding shown the influence of sound in the room that feedsback to the pickup. The purpose is to see how much sound from the speakers pollutes the signal from the turntable/cartridge/arm system. You may call it microphony

I record in Cooledit Pro ( Adobe Audition), but can also do it in REW
like this, it shows the feedback noise when stylus is in groove, compared to lifted up and not touching the record
1668267661119.png


Diffrence armrest. pink noise-silence. No real difference with pink noise or silence when arm in in armrest.
1668268134474.png


Difference in groove . Pink noise -silence
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Balle Clorin

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https://www.ginifab.com/feeds/angle_measurement/


Are you sure it's 21 degrees?

Shouldn't it be this:

View attachment 241884

The VTA should be defined by the axis line between the stylus tip and the suspension/pivot point of the cantilever. It is the motion of the stylus tip deflecting this axis line that determines the electrical output of the cartridge. The suspension/pivot point is not visible in the photo so there is margin of error either way, blue or red, but the way I've drawn it more accurately pegs the VTA as 24 degrees, which is closer to AT's spec of 23. If you reposition the origin of the protractor onto the stylus point then the measurement will become apparent.

An example that clearly demonstrates the point is a Shure M44-7 which has a bow shape cantilever. The entire cantilever is curved, but the axis line between the stylus tip and the suspension/pivot point positively defines the VTA.

View attachment 241897

Ray
Your comment is absolutely correct, Audio-Technica said the same:


"I would suggest only trying to measure with the correct downforce applied and the arm height set so the arm tube is parallel to the record surface (at eye level), and whilst the stylus is in the groove of a record. You should then draw a line from the centre of the stylus tip to the center of the pivot point of the stylus (as can be seen in the attached diagram). It is quite difficult to do."



The VTA for the OC9ML/II was originally specified at 23 degrees.


1668721254876.png


1668721364819.png
 

Thomas_A

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SRA%20OM40.001.jpeg
With respect to rake angle this is a shot I took on OM40.
 
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Balle Clorin

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My seem look too low , but hard to see any microridg angle
 

George Vardis

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It's my first post here. So I introduce myself quickly(?)
I am a HiFi amateur and after almost 50 years in this hobby, I would say that I had the opportunity to get to a level of considerable measurement and reproduction/ listening instruments .
I describe my listening system:
Sources:
- EMT 950 Record Player
-Sony SCD1 CDP
-Studer A80 (R2R)
- Revox A77 (R2R)
-Nakamichi Dragon
- DIY DAC(Soekris)

Amplification/Speakers
- AR SP11 MKII
-ATC 100 Pro Active
In the pictures below, my measuring instruments and 2 W&F measurements of my EMT 950 with Audio Precision Portable One DD+ HP35665A.
PS1. I am a biologist and I spent a long time before I could learn to use these tools
PS2. I need a help measuring the W&F of the EMT 950 with LP tests
 

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Balle Clorin

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Seems like you already got a result, . An alternative way: Google WFGUI A software W&F meter, and download it , record A wav file from the test record and play it on PC and run WFGUI via a PC and USB DAC in loop. Or just from RIAA into your PC. I use a cheap USB DAC/adc from DLock 63926 as soundcard.

You can also import the sound file to Audacity an use the wow&flutter add in to demodulate the tone and see the speed variation as a plot. But it does not give any meaningful % numbers
 
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George Vardis

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Seems like you already got a result, . An alternative way: Google WFGUI A software W&F meter, and download it , record A wav file from the test record and play it on PC and run WFGUI via a PC and USB DAC in loop. Or just from RIAA into your PC. I use a cheap USB DAC/adc from DLock 63926 as soundcard.

You can also import the sound file to Audacity an use the wow&flutter add in to demodulate the tone and see the speed variation as a plot. But it does not give any meaningful % numbers
Thank you Balle Clorin for your reply.
But maybe I didn't explain myself well. I have the Audio Precision Portable One which is a reference instrument for measuring W&F, among other measurements. My request for help is if you have to show me an LP Test with a signal of 3.150Hz. I have "The Ultimate ANALOGUE test LP" but the diameter of the central hole is a few tenths of a millimeter wider than the spindle of the EMT 950. So the measurement of W&F is not reliable.
So the question is if any member of the Forum could point me to any good quality LP Test disk ?
And that's my Audio Precision.
 

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sergeauckland

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Thank you Balle Clorin for your reply.
But maybe I didn't explain myself well. I have the Audio Precision Portable One which is a reference instrument for measuring W&F, among other measurements. My request for help is if you have to show me an LP Test with a signal of 3.150Hz. I have "The Ultimate ANALOGUE test LP" but the diameter of the central hole is a few tenths of a millimeter wider than the spindle of the EMT 950. So the measurement of W&F is not reliable.
So the question is if any member of the Forum could point me to any good quality LP Test disk ?
And that's my Audio Precision.
That LP is probably as good as it gets these days. I too have exactly the same problem. I have three different LPs with 3kHz (or 3.15kHz) W&F tracks, and they all have the same issue. There used to be the Feickert W&F meter app which had a notch filter at 0.55 Hz to remove the eccentricity, but that app is no longer available, so you would have to have a meter, whether physical or software that included that filter.

Does your AP meter include that notch? If so, then that's about the best you can hope for, as 'perfect' test LPs don't exist.

Oh, and by the way, even with the filter, you need to repeat the measurements a few times with the LP repositioned to make sure that the errors in the turntable, which could also be once per revolution, don't coincide with the LP's eccentricity.

Your 950 is also about as good as it gets, I have to put up with a 948...

S.
 

JP

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That LP is probably as good as it gets these days.

Disagree. The W&F track on the two samples I have is among if not the worst I’ve ever seen. Perhaps there are re-cuts where they did better?
 

George Vardis

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That LP is probably as good as it gets these days. I too have exactly the same problem. I have three different LPs with 3kHz (or 3.15kHz) W&F tracks, and they all have the same issue. There used to be the Feickert W&F meter app which had a notch filter at 0.55 Hz to remove the eccentricity, but that app is no longer available, so you would have to have a meter, whether physical or software that included that filter.

Does your AP meter include that notch? If so, then that's about the best you can hope for, as 'perfect' test LPs don't exist.

Oh, and by the way, even with the filter, you need to repeat the measurements a few times with the LP repositioned to make sure that the errors in the turntable, which could also be once per revolution, don't coincide with the LP's eccentricity.

Your 950 is also about as good as it gets, I have to put up with a 948...

S.
Thank you, I suspected such an answer.
No, AP does not have a similar filter. I also have the Feickert record, which is even worse. The 948 is excellent.
 

JP

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@George Vardis send over a recording of the W&F track and I'll do a polar for you. EDIT - be sure to catch the start of the track so I've something to index off of. That way it can be compared to other polars of the "same" record.
 

stereoplay

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I have quiet a lot of speed measurement test records. Some time ago, I put them on a Grundig PS4500 (Aka Technics SL-Q2) to see what happens: All of them showed different values.
So what I can say from my side of view: Be careful with the test records you

Look at this post. Here I compared some discs. That's why I use a gyroscope...
 
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