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Thread: Accuracy

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    Accuracy

    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?
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    Addicted to Best! audioarcher's Avatar
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    Quote Originally Posted by Bruce B View Post
    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?

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    Quote Originally Posted by audioarcher View Post
    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.
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    Quote Originally Posted by GaryProtein View Post
    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.

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    WBF Technical Expert (Speakers & Audio Equipment)/Member Sponsor [Technical Expert] garylkoh's Avatar
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    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.
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    Quote Originally Posted by garylkoh View Post
    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.).

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    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!
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  8. #8
    Quote Originally Posted by Bruce B View Post
    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?
    AuI ConverteR 48x44 (ISO, DFF, DSF, WAV, FLAC, AIFF,...) developer http://samplerateconverter.com

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    Quote Originally Posted by microstrip View Post
    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!
    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.

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    Quote Originally Posted by morricab View Post
    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.

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