Accuracy

Bruce B

WBF Founding Member, Pro Audio Production Member
Apr 26, 2010
6,760
150
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Seattle, WA
www.pugetsoundstudios.com
#1
Just been thinking about this. Also can be applied to R2R's as well.

When you get test tones on an LP, how accurate are they? Has anyone done any tests on the Neumann and Scully lathes? Same for R2R. The MRL tapes we get have test tones as well. How accurate are the machines that recorded them? I know when I send a test tone from a generator to my Studer and record test tones, when I play them back it's not perfect.

How can you get as close to perfect on a turntable?

How can you get as close to perfect on a R2R?
 

audioarcher

Active Member
May 7, 2012
1,330
2
38
Seattle area
#2
Just been thinking about this. Also can be applied to R2R's as well.

When you get test tones on an LP, how accurate are they? Has anyone done any tests on the Neumann and Scully lathes? Same for R2R. The MRL tapes we get have test tones as well. How accurate are the machines that recorded them? I know when I send a test tone from a generator to my Studer and record test tones, when I play them back it's not perfect.

How can you get as close to perfect on a turntable?

How can you get as close to perfect on a R2R?
I'd say the biggest problem for a test tone on a LP would be whether or not the spindle hole is perfectly centered. Since that is rarely the case that's the biggest road block. Then after that the lathes wow and flutter would be the next biggest concern. Also the lathes speed accuracy. I wouldn't expect LP test tones to be very accurate unless the spindle hole is centered.

I don't know much about R2R motors but I would assume that some sort of servo control may improve their specs?
 
Jul 25, 2012
2,541
5
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NY
#3
I'd say the biggest problem for a test tone on a LP would be whether or not the spindle hole is perfectly centered. Since that is rarely the case that's the biggest road block. Then after that the lathes wow and flutter would be the next biggest concern. Also the lathes speed accuracy.

I don't know much about R2R motors but I would assume that some sort of servo control may improve their specs?
The ability to correct that was an excellent feature of the Nakamichi TT.

I don't know why its self centering feature has never been incorporated in anybody else's TT.
 

audioarcher

Active Member
May 7, 2012
1,330
2
38
Seattle area
#4
The ability to correct that was an excellent feature of the Nakamichi TT.

I don't know why its self centering feature has never been incorporated in anybody else's TT.
Good point. Nobody seems interested in tackling this problem with another design like the Nak Dragon. I have never heard one but would like to.
 

garylkoh

WBF Technical Expert (Speakers & Audio Equipment)
Sep 6, 2010
5,438
28
48
Seattle, WA
www.genesisloudspeakers.com
#5
Good point, Bruce.

When I use the Platterspeed app (on Android) using the Hifi News test record 1000 Hz, it gives me +/- 0.17%. With the Analogue Productions test record, the best I've been able to get was +/- 0.13%. Using the 3150 Hz track on the Analogue Productions record, I can get +/- 0.09%.

May be the timeline might be a more accurate measure in this case as we don't know if the variation is already on the test album.
 

morricab

Well-Known Member
Apr 25, 2014
3,414
487
83
Switzerland
#6
Good point, Bruce.

When I use the Platterspeed app (on Android) using the Hifi News test record 1000 Hz, it gives me +/- 0.17%. With the Analogue Productions test record, the best I've been able to get was +/- 0.13%. Using the 3150 Hz track on the Analogue Productions record, I can get +/- 0.09%.

May be the timeline might be a more accurate measure in this case as we don't know if the variation is already on the test album.
I use an Allnic Speednic, which is accurate to 0.001% according to their own claims (I cannot prove it is this accurate though). What I can tell you is that it is VERY sensitive to tiny fluctuations in TT speeds and you can watch it while playing the record (you would be surprised how many TTs show variations under load from the needle.).
 
May 30, 2010
15,499
710
113
Portugal
#7
Accuracy to more than .1% in vinyl sound reproduction is meaningless, unless you are worried that your LP playing time can increase by more than one second and his costing you some extra cents of your precious stylus lyfetime ...

Even the best reel to reel machines are accurate to +/- .2%.

Very short time fluctuations (wow and flutter) are the critical parameters to check in most turntables. In order to be precise, the ultra accurate and precise meters integrate the measurement for a significant time, ignoring anything else.

Very sightly slowing under load can be a good thing - it shows that your turntable has no feedback and is not permanently correcting the speed. And here we go again, David is probably approaching his keyboard now! :rolleyes:
 
Jul 30, 2015
138
0
16
#8
Just been thinking about this. Also can be applied to R2R's as well.

When you get test tones on an LP, how accurate are they? Has anyone done any tests on the Neumann and Scully lathes? Same for R2R. The MRL tapes we get have test tones as well. How accurate are the machines that recorded them? I know when I send a test tone from a generator to my Studer and record test tones, when I play them back it's not perfect.

How can you get as close to perfect on a turntable?

How can you get as close to perfect on a R2R?
Bruce,

Why you need record tone to LP? Why don't get it stright from generator?

Do you want to check the LP player?
 

morricab

Well-Known Member
Apr 25, 2014
3,414
487
83
Switzerland
#9
Accuracy to more than .1% in vinyl sound reproduction is meaningless, unless you are worried that your LP playing time can increase by more than one second and his costing you some extra cents of your precious stylus lyfetime ...

Even the best reel to reel machines are accurate to +/- .2%.

Very short time fluctuations (wow and flutter) are the critical parameters to check in most turntables. In order to be precise, the ultra accurate and precise meters integrate the measurement for a significant time, ignoring anything else.

Very sightly slowing under load can be a good thing - it shows that your turntable has no feedback and is not permanently correcting the speed. And here we go again, David is probably approaching his keyboard now! :rolleyes:
You are misinformed regarding properly designed servos...they are not permanently correcting the speed...PLL based DDs, yes top models from Japan? No. Slowing is never a good thing because it indicates that the TT will be at the mercy of modulation in the record. A heavy platter will still slow some and if the motor is a low torque design (like it takes more than a few seconds to spin up the platter) then it will be incapable of getting the speed back on track. JVC and Yamaha both used a bi-directional servoe that prevented over and undershoot. I have measured quite a few TTs now with the Speednic with and without records playing. Nearly all the belt drives were off on absolute speed and nearly all showed minor fluctuations in the strobe pattern under load of playing a record. My Yamaha doesn't budge without or with a record. No fluctuation at all visible in the strobe pattern. If it was "hunting" this would be revealed I think in a waver in this strobe pattern(that of course looks stationary when the right speed is reached). I will try a Pioneer PL-7L and Technics SL1200 at a friend's the weekend after this one to see if they have visible fluctuations under load. I think these fluctuations are likely audible.

Interestingly, the best japanese DDs mixed high mass (sometimes oversized to increase inertia) platters, relatively high torque, cog and torque ripple free motors and sophisticated servo speed control, so not just one solution to the probolem (high mass or high torque, or smooth running motor or servo control) but all four ideas. What they didn't do (with the excpetion of Kenwood L07 and Exclusive P3 and to a lesser degree my Yamaha) is go all out on vibration and resonance control like what became the obsession in Western TTs, while largely ignorin the motor (some exceptions naturally). I guess they figured the delivering the speed exactly correctly was more important.

If the speed is off by 0.1% and precisely at that incorrect speed then I would agree with you about the audibility; however, if you have a TT running one speed unloaded and then it drops when you drop the needle then it is clear that this level of drag has an impact on that design and modulation of that drag will also then modulate the speed. I have not calculated it but I would think you would need a very high mass platter on a very low friction bearing to not be influenced to a signficant degree by moduation of the needle in the groove if your motor was not able to respond because the torque is so low.
 

morricab

Well-Known Member
Apr 25, 2014
3,414
487
83
Switzerland
#10
You are misinformed regarding properly designed servos...they are not permanently correcting the speed...PLL based DDs, yes top models from Japan? No. Slowing is never a good thing because it indicates that the TT will be at the mercy of modulation in the record. A heavy platter will still slow some and if the motor is a low torque design (like it takes more than a few seconds to spin up the platter) then it will be incapable of getting the speed back on track. JVC and Yamaha both used a bi-directional servoe that prevented over and undershoot. I have measured quite a few TTs now with the Speednic with and without records playing. Nearly all the belt drives were off on absolute speed and nearly all showed minor fluctuations in the strobe pattern under load of playing a record. My Yamaha doesn't budge without or with a record. No fluctuation at all visible in the strobe pattern. If it was "hunting" this would be revealed I think in a waver in this strobe pattern(that of course looks stationary when the right speed is reached). I will try a Pioneer PL-7L and Technics SL1200 at a friend's the weekend after this one to see if they have visible fluctuations under load. I think these fluctuations are likely audible.

Interestingly, the best japanese DDs mixed high mass (sometimes oversized to increase inertia) platters, relatively high torque, cog and torque ripple free motors and sophisticated servo speed control, so not just one solution to the probolem (high mass or high torque, or smooth running motor or servo control) but all four ideas. What they didn't do (with the excpetion of Kenwood L07 and Exclusive P3 and to a lesser degree my Yamaha) is go all out on vibration and resonance control like what became the obsession in Western TTs, while largely ignorin the motor (some exceptions naturally). I guess they figured the delivering the speed exactly correctly was more important.

If the speed is off by 0.1% and precisely at that incorrect speed then I would agree with you about the audibility; however, if you have a TT running one speed unloaded and then it drops when you drop the needle then it is clear that this level of drag has an impact on that design and modulation of that drag will also then modulate the speed. I have not calculated it but I would think you would need a very high mass platter on a very low friction bearing to not be influenced to a signficant degree by moduation of the needle in the groove if your motor was not able to respond because the torque is so low.
I misspoke partly, I meant older PLL DDs (early 70s and later mass market with cheap solutions). From late 70s onward they were mostly done correctly with top designs.
 
May 30, 2010
15,499
710
113
Portugal
#11
You are misinformed regarding properly designed servos...they are not permanently correcting the speed...PLL based DDs, yes top models from Japan? No. Slowing is never a good thing because it indicates that the TT will be at the mercy of modulation in the record. A heavy platter will still slow some and if the motor is a low torque design (like it takes more than a few seconds to spin up the platter) then it will be incapable of getting the speed back on track. JVC and Yamaha both used a bi-directional servoe that prevented over and undershoot. I have measured quite a few TTs now with the Speednic with and without records playing. Nearly all the belt drives were off on absolute speed and nearly all showed minor fluctuations in the strobe pattern under load of playing a record. My Yamaha doesn't budge without or with a record. No fluctuation at all visible in the strobe pattern. If it was "hunting" this would be revealed I think in a waver in this strobe pattern(that of course looks stationary when the right speed is reached). I will try a Pioneer PL-7L and Technics SL1200 at a friend's the weekend after this one to see if they have visible fluctuations under load. I think these fluctuations are likely audible.

Interestingly, the best japanese DDs mixed high mass (sometimes oversized to increase inertia) platters, relatively high torque, cog and torque ripple free motors and sophisticated servo speed control, so not just one solution to the probolem (high mass or high torque, or smooth running motor or servo control) but all four ideas. What they didn't do (with the excpetion of Kenwood L07 and Exclusive P3 and to a lesser degree my Yamaha) is go all out on vibration and resonance control like what became the obsession in Western TTs, while largely ignorin the motor (some exceptions naturally). I guess they figured the delivering the speed exactly correctly was more important.

If the speed is off by 0.1% and precisely at that incorrect speed then I would agree with you about the audibility; however, if you have a TT running one speed unloaded and then it drops when you drop the needle then it is clear that this level of drag has an impact on that design and modulation of that drag will also then modulate the speed. I have not calculated it but I would think you would need a very high mass platter on a very low friction bearing to not be influenced to a signficant degree by moduation of the needle in the groove if your motor was not able to respond because the torque is so low.
It seems you are misinformed about servos :) - they are permanently correcting errors, unless they can guess the future ... You can optimize the way they correct speed fluctuations and claim they are inaudible, it is what is called performance tuning, but they are permanently actuating and correcting. Just because your rudimentary measuring system does not detect it does not mean that there are no fine speed variations at all. When people say it prevents over and undershoot they are just saying it minimizes them. There is no absolute perfection in these affairs.

Sorry, I dislike when people say there is only one proper way to do something in audio and it is just the way their equipment does it, all others who do differently are ignorant and are obsessed with secondary aspects.

Again, your drag test is interesting, but there is nothing in it that can correlate firmly with subjective sound quality of vinyl. BTW, we have debated this issue before when discussing DD turntables.
 

morricab

Well-Known Member
Apr 25, 2014
3,414
487
83
Switzerland
#12
It seems you are misinformed about servos :) - they are permanently correcting errors, unless they can guess the future ... You can optimize the way they correct speed fluctuations and claim they are inaudible, it is what is called performance tuning, but they are permanently actuating and correcting. Just because your rudimentary measuring system does not detect it does not mean that there are no fine speed variations at all. When people say it prevents over and undershoot they are just saying it minimizes them. There is no absolute perfection in these affairs.

Sorry, I dislike when people say there is only one proper way to do something in audio and it is just the way their equipment does it, all others who do differently are ignorant and are obsessed with secondary aspects.

Again, your drag test is interesting, but there is nothing in it that can correlate firmly with subjective sound quality of vinyl. BTW, we have debated this issue before when discussing DD turntables.
Oh I like belt drive just fine when a proper motor/controller is used. Like with a continuum caliburn or their new obsidian. There are some sinusoidally commutated motors (otherwise known as brushless DC) that can work well in BDs too. Brinkmann's new motor for their BD is really interesting too. But based on rumble specs for a Bardo, Brinkmann hasn't figured out how to make a quiet DD. So their BD with advanced motor is probably a lot better.

I also like the big Kuzma with 3 motors, which smoothes out issues with torque ripple and cogging. Voyd is interesting but noisy.

Plain old AC synch is not so bad when a synthesized AC is provided.

An idler with similar properties is also potentially good too.

My measuring system might be "rudimentary " but it is very sensitive to speed fluctuations and I disagree, those fluctuations are not doing the sound any favors any more than jitter helps digital sound.
 
May 30, 2010
15,499
710
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Portugal
#13
(...) My measuring system might be "rudimentary " but it is very sensitive to speed fluctuations and I disagree, those fluctuations are not doing the sound any favors any more than jitter helps digital sound.
The point is that the most of the fluctuations your rudimentary instrument measures are not directly correlated with sound quality. Sorry, comparing jitter to my interpretation of stylus drag is completely erroneous.

Vinyl playback is such a complex process that most of the time it is not possible to create general rules. In the end we have good and poor implementations of each technique.
 

morricab

Well-Known Member
Apr 25, 2014
3,414
487
83
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#14
The point is that the most of the fluctuations your rudimentary instrument measures are not directly correlated with sound quality. Sorry, comparing jitter to my interpretation of stylus drag is completely erroneous.

Vinyl playback is such a complex process that most of the time it is not possible to create general rules. In the end we have good and poor implementations of each technique.
Why do you call the Speednic rudimentary? Just because it doesn't have a digital readout? It is quite a precise measurement tool and while it doesn't tell you how far you are off it is quite sensitive to if you are off. The fact that it works WHILE you play your records is a big advantage.

And I disagree, those speed fluctuations are most likely audible and therefore impact sound quality in some way. Comparison with Jitter was an analogy but they are closer in their sonic impact than you seem to be willing to credit.

Of course my comments assume that everything else is equal...a much better cart or phonostage with an inferior TT will likely still sound better than a system with a poor phonostage...given how important the electronic handling of the signal from the cartridge is.
 
Jul 30, 2015
138
0
16
#15
Required precision and stability is not abstract values.

Required precision of measurement depend on required precision measurements only.

As example, if you need check changing frequency value during LP playback :

1. Need frequency meter with precision 3 ... 10 times better than expected frequency unstability.

2. Need LP-disk that provide precision 3 ... 10 times more than the frequency meter.
 
May 30, 2010
15,499
710
113
Portugal
#16
Why do you call the Speednic rudimentary? Just because it doesn't have a digital readout? It is quite a precise measurement tool and while it doesn't tell you how far you are off it is quite sensitive to if you are off. The fact that it works WHILE you play your records is a big advantage.

And I disagree, those speed fluctuations are most likely audible and therefore impact sound quality in some way. Comparison with Jitter was an analogy but they are closer in their sonic impact than you seem to be willing to credit.

Of course my comments assume that everything else is equal...a much better cart or phonostage with an inferior TT will likely still sound better than a system with a poor phonostage...given how important the electronic handling of the signal from the cartridge is.
Speednic is just a nice looking strobe disk with a LED strobe. Its only specification is accuracy - probably that of the cheap quarzt crystal controlling the oscilator driving the LED. For the last twenty years I have used a Vellman kit (50 Hz time base) with a large yellow LED that costed me less than $20 to do exactly the same with a small strobe. Typically strobes have several rings and you use just one frequency pulsating light. They created a new expensive gimmick for audiophiles - a single ring disk with a commuted pulse light source. I doubt any one is using it at 45 rpm... :rolleyes:

However since I replaced the lighting lamp with a LED lamp do not use my strobe anymore - the 50 Hz mains accuracy (just now 50,02) is good enough for my purposes.

Anyway I was really amused when I saw the youtube movie seeing the guy who owns the Garrard 401 with the big strobe using the Speednic.
 

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morricab

Well-Known Member
Apr 25, 2014
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487
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#17
Speednic is just a nice looking strobe disk with a LED strobe. Its only specification is accuracy - probably that of the cheap quarzt crystal controlling the oscilator driving the LED. For the last twenty years I have used a Vellman kit (50 Hz time base) with a large yellow LED that costed me less than $20 to do exactly the same with a small strobe. Typically strobes have several rings and you use just one frequency pulsating light. They created a new expensive gimmick for audiophiles - a single ring disk with a commuted pulse light source. I doubt any one is using it at 45 rpm... :rolleyes:

However since I replaced the lighting lamp with a LED lamp do not use my strobe anymore - the 50 Hz mains accuracy (just now 50,02) is good enough for my purposes.

Anyway I was really amused when I saw the youtube movie seeing the guy who owns the Garrard 401 with the big strobe using the Speednic.
Plenty of speculation on your part. Battery power and ability to measure while playing, while not unique, is extremely useful. I got mine for a nice discount so, while not cheap, it is a lot cheaper than many of the tweaks touted on this site and it works as advertised.

Have you observed your TT while playing??
 
May 30, 2010
15,499
710
113
Portugal
#18
Plenty of speculation on your part. Battery power and ability to measure while playing, while not unique, is extremely useful. I got mine for a nice discount so, while not cheap, it is a lot cheaper than many of the tweaks touted on this site and it works as advertised.

Have you observed your TT while playing??
Not speculation, just facts - I even included a photo of the device I built. Sorry to say, but you are the one who is speculating on miraculous devices that you seem not to understand.

And yes, I always measure my turntable playing - I have a small strobe that is placed on the record label. Did not have to wait for the inventions of a 350 euros device to do it.
 

ddk

Industry Expert
May 19, 2013
3,963
498
83
Utah
#19
Accuracy to more than .1% in vinyl sound reproduction is meaningless, unless you are worried that your LP playing time can increase by more than one second and his costing you some extra cents of your precious stylus lyfetime ...

Even the best reel to reel machines are accurate to +/- .2%.

Very short time fluctuations (wow and flutter) are the critical parameters to check in most turntables. In order to be precise, the ultra accurate and precise meters integrate the measurement for a significant time, ignoring anything else.

Very sightly slowing under load can be a good thing - it shows that your turntable has no feedback and is not permanently correcting the speed. And here we go again, David is probably approaching his keyboard now! :rolleyes:
Mike L & I were having fun listening yesterday :)!

I agree with you that a drift of +/- .1% and maybe even a little higher over time isn't audible but constant or periodic adjustments of the same via some sort of feedback loop has a negative impact on the sound.

david
 

morricab

Well-Known Member
Apr 25, 2014
3,414
487
83
Switzerland
#20
Not speculation, just facts - I even included a photo of the device I built. Sorry to say, but you are the one who is speculating on miraculous devices that you seem not to understand.

And yes, I always measure my turntable playing - I have a small strobe that is placed on the record label. Did not have to wait for the inventions of a 350 euros device to do it.
Nothing miraculous and what exactly, am I not understanding? Your device works (maybe) and mine works...I paid more, so what? I could build the device you have shown no problem...done much more compllicated things than that in my life...both in audio and in the lab.
 

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