Sutherland "Timeline"
Measuring turntable speed
Happy Holidays everyone! This has probably been discussed before but I'm of the age that makes me a bit of a Luddite. I have a VPI Scout and SDS. I use "The Ultimate Analogue Test LP" to play the test tone and (at least I used to) the app Dr. Fridrekson(??) had other there. It mysteriously disappeared from my iPad and I can't find it anywhere. What are you using? Thanks!
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@mijostyn I'd be curious to see how accurate it is compared to something more expensive. I paid full price for mine, all of $25 I think. I had a problem with mine a while after I bought it and they sent me another one immediately, no questions asked. Great service. I also like their cartridge mounting kits a lot. |
I have an industrial rpm/ fpm etc etc strobe that I use for work. It has two modes, contact with various size wheels and strobe non contact very similar to the one Greg linked to. It is EXTREMELY accurate. But for a test I also just ordered one of them at $15 so I can compare to my industrial unit. Will report back. |
I have a very lightweight paper strobe disc I put atop a spinning record. I also sometimes find a record that I'm certain possesses a 440 hz A somewhere within it (any recording of a non-period instrument orchestral recording will have one) and then match the pitch on the record to my Seiko metronome's 440 tuning tone. BTW, it's absolutely shocking how inaccurate my SOTA Sapphire's fine speed adjustment wheels have gotten over the centuries. |
+1 on the RPM Speed and Wow app I used it on my TT and it registered 33.35 and I compared it to my $15.00 laser RPM meter that big_greg mentioned and that registered 33.29 so between the 2 I should be pretty close and my Acoustic Solid 111 Metal keeps it constant, I check it once a month and for 11 months no variation from my base line readings. |
All the strobe things is what they are. But it lacks the resolution 3150 Hz (number/second) of and the industry standard of DIN IEC 386 (formerly DIN 45507). Like the "Feickert Platter speed" app. I it is not in android app store (or Apple store). I just downloaded the app from here and side loaded it on android. (It side steps security so there is a risk. But you all have a old android phone laying around that can be used for this highly important task! ;) It will cost you $0.) https://apkpure.com/platterspeed-vinyl-tool/ch.progtec.PlatterSpeed Not just it has better resolution and graphs it also do the measurements exactly as when you are playing a record. With the mass from it and you can use the clamp you usually use. And with the stylus in the groove with its tiny drag. 👍 In comparison I have never played a record with a phone on the platter. I see those low resolution apps more like a party trick and nothing when I want accuracy and the speed fluktration. (But that is maybe just me) Just a discarded android phone and a record with a 3150 Hz track and you are done. |
I guess one question is how accurate you are looking to get as yes an Android phone app is not going to be the last word in accuracy. But if all you are looking for is to get very close and check stability they are free and fairly decent. How many here are going to claim they can hear the difference between 33.30 and 33.40 say as long as speed is constant? I know I cannot...... PS. That does NOT mean I am not going to strive for 33.33 but just saying..... |
Cousinbilly, you are absolutely right. You have to be able to measure the speed with the record playing which big_greg's device will do. I have the Road Runner on my SOTA so I can compare big_greg's device to that and use it to check the SME. Hard to go wrong for $15.00. As an aside, is turntable speed all that important. I think not as important as speed variations like wow and flutter. The absolute speed could be off 1 or 2% and most of us myself included would not know. The only time I ever noticed it was when I was synchronizing the turntable with the computer to compare digital vs analog versions of the same record. |
As an aside, is turntable speed all that important. I think not as important as speed variations like wow and flutter. The absolute speed could be off 1 or 2% and most of us myself included would not know.For once we agree on something! How many here are going to claim they can hear the difference between 33.30 and 33.40 say as long as speed is constant? Have a great day! |
https://i.imgur.com/Lo0LYl1.jpg This is good enough for me and the DIN standardisation. 3150 complete sine waves in one second. Is more than a strobe disc can ever do. And the lack of the high granularity we can not get the speed variation either. Now we get graphs with the better resolution. Regarding the lathe machine speed accuracy precision. It starts to get more silly and pointless the more number 3:s we add to the end of 33.3xxx. And yes we measure with the diamond in the groove. That someone asked. |
Fun gear! So you put one reflective strip on the edge of the platter. And you lay the device down so you don't hold it (movement of holding it introduces in its own fluctuations). But if we stop and think about it a second. Manufacturer of TT measure and specify speed as wow and flutter. This measurement quantifies the amount of 'frequency wobble' (caused by speed fluctuations)Source: https://en.m.wikipedia.org/wiki/Wow_and_flutter_measurement So let's look at the "speed fluctuations" that a DT-2234+ digital tachometer can capture: At 33⅓ rpm the platter has done little more than a half rotation. And you need to wait almost another half turn before you get the next measurement. With out taking into account the variance of the tachometer itself ± 0.1 rpm. (33⅓ rpm / 60s = 0.5555 RPS) So almost 2 seconds between each measuring point. During the elapsed 2 seconds the "speed fluctuations" can easily have been momentarily fluctuate between +0.25% AND -0.25%. But that fluctuation is something you don't pick up and totally miss during the ~2s wait.. we only get a average over those ~2s. Here is a example of how rapidly the speed is fluctuate during 2s if we use a better method with a greater resolution: https://imgur.com/a/Vmz7CrU Measurement is usually made on a 3.15 kHz (or sometimes 3 kHz) tone, a frequency chosen because it is high enough to give good resolution, but low enough not to be affected by drop-outs and high-frequency losses. Ideally, flutter should be measured using a pre-recorded tone free from flutter.Source: https://en.m.wikipedia.org/wiki/Wow_and_flutter_measurement As seen in the Imgur link above in this post we here measure EACH 0.1s something that have 3150 samples each second.. It a whole lot another resolution that a stroboscope never ever can give you. Yes, why is this useful? Is it not lunatic? This resolution enable you to see if you get less fluctuation if you add a standard 500g clamp (center/ring)... Will a 500g addition that add the rotating mass (inheritance) to make your platter to fluctuate less? With a strobe you will NEVER know.. You can also catch if your speed is drifting or is rock stable the same after a week or so. Small shanges is impossible to capture otherwise. Like when changing belt or maintenance with oil change and so on.. All you need is a calibration disc/LP (that you can calibrate other things also with). And a vinyl lover have to have one of those anyway! And a old discarded android phone $0 (or your present one) and just download the app. (See my previous posts) You can save and load measurements and compare them. Of course you can adjust the speed on the 45rpm also. So why pay money for a stroboscope when you can buy a test record instead that with the other tracks you can measure other things.. the strobe can only measure one thing and that is done rather poorly relatively compared to the standard way of doing it... I don't believe that I am smarter than the girls and boys behind standardisation institutions like specifications (that use a variant of this procedure):
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Is your graph more accurate than a wow and flutter meter??? Been playing with a test record and wow and flutter app lately. Do you mean a meter like this? https://youtu.be/0G2kU1e9Cpo I think that we may not need more accuracy or what to do with more accuracy than that. That is not the game. You need enough accuracy and resolution to be able to make different decisions lit the examples above. When you have enough accuracy and resolution to measure the fluctuation constantly the same between measurements. By using the same method and equipment. In the app that I used, it is written: "You can now calculate wow of your turntable in accordance to DIN IEC 386 (formerly DIN 45507) using the recorded chart data! Expensive special equipment was needed before to do so!" That tells me that the app developer thinks that he has and use the same method and resolution to calculate the results. As complies with the mentioned DIN standardisation. I believe this is "good enough". With the saved graphs and with the calculations as seen in the lower left corner IS better than only a analogue meter showing only a temporary value/level and not the other mentioned calculations. Best regards. |
Optimize thanks for the information. I have a Phoenix roadrunner for the speed which goes out to 33.333. I have been interested, in the different turntables I have been building, to see if you can see the difference between a 35 lb platter vs 55 pounder. Also different bearings I have been playing with. The roadrunner take one trigger per revolution then does the math. But like you say what goes on for the 2 seconds. It would be nice to know how the software or machine samples the revolution and how accurate it really is. I need to experiment more to see what make changes in the readings. Thanks again Tom |
Optimize, I know of no turntable were you can adjust wow and flutter. I know a bunch were you can adjust the speed. Thus a device measuring 3150 times a second is no more useful in adjusting speed than one measuring every revolution. It is revolutions per minute after all.
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Optimize, in this life it helps to be realistic about things. Nobody I know is going to spend $50 large on a turntable and try to add mass to the platter. Does a heavy platter reduce wow and flutter? Given the same motor probably but with a different more powerful motor maybe not. One thing I will guarantee is you will never be able to tell the difference. So all this is purely academic. In reality people do just fine with plain A/C synchronous motors and stepped pulleys. The only good reason to have adjustable speed is to match pitch which the vast majority of us do not need. I do have a SOTA cosmos with all the fixins and one of the nicest things about it is you can set it and forget about it. I'm not going to add mass to the platter and risk burning out the motor and I do not care about the wow and flutter spec because I can't hear it. Don not burn your brain out mental masturbating about less than trivial issues. |
Just wondering how many turntables you have built?? How many platters of various weights and materials have you tried on the same turntable?? And how about motors and controllers??? Also they use heavy platters with small motors. But the bearing could be a issue. Just wondering how you reached a conclusion on what is trivial in audio??? |