Since the polar plot era, about 5 years ago, at least 3 well conducted tests involving 2 arms on independent rigs concur. There's no meaningfully detectable change in platter speed arising from changes in stylus-groove friction or drag from modulation. Using methods sensitive enough to detect even momentary speed changes way below the audible threshold. Some of the tests were blind, and I was involved in analysis of some of them. Independent rigs, apparently otherwise healthy.
For good theoretical reasons too. To avoid the audible threshold, a typical drive system need only be responsive enough to provide about 0.001Nm of extra platter torque within 0.1s or so. It's all small stuff and easy for normal healthy rigs.
Platters can't, and don't, change speed meaningfully given the small forces involved.
LD
For good theoretical reasons too. To avoid the audible threshold, a typical drive system need only be responsive enough to provide about 0.001Nm of extra platter torque within 0.1s or so. It's all small stuff and easy for normal healthy rigs.
Platters can't, and don't, change speed meaningfully given the small forces involved.
LD
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None of which takes anything away from the Engineering Technics did to produce the SP-10Mk3 which can spin up a 10kg platter to speed in 1/4 revolution and has some of the best polar plots on here
.This is true. But phenomenal torque isn't causal as to its phenomenal speed stability. Rather, it's an all round ('scuse the pun) well engineered product and gets it all right. IMO, of course ! And its speed stability can be matched fairly modestly.........None of which takes anything away from the Engineering Technics did to produce the SP-10Mk3 which can spin up a 10kg platter to speed in 1/4 revolution and has some of the best polar plots on here
LD
While a transient change in stylus drag due to groove modulation will not impose a significant step change in the speed of a platter whose mass is measured in kilograms, that same transient change in stylus drag can de-stabilize the tracking of an arm/cartridge whose effective mass is measured/calculated in grams. This transient change in stylus drag can be significant enough to induce stylus scrubbing from vertical displacement due to the effects of stylus VTA and from horizontal displacement due to the effects of tonearm offset angle. It was demonstrated early on in this thread that stylus scrubbing from either of these conditions has the same net effect as speed instability, even if the turntable drive itself were to have perfect numbers. Focus.
Ray K
Ray K
Yes, absolutely.
This effect is real, and doesn't show up in the 2-arm polar plot test regimes because the 'test arm', by definition, is reading a continuous tone without dynamic modulation.
What the test regime does confirm, once and for all, is that platter speed variation isn't the cause of pitch instability induced by dynamic programme modulation.
Cart/arm stability, rather than platter speed variation, is typically a significant factor in overall pitch stability. IME.
LD
I recall there's a Test LP thread going, I wonder if they've decided on the tracks they want and pressed the thing yet. A test tone switched on-and-off, or sine-wave-modulated in the 7Hz to 14Hz range might give interesting results.
If there is a silent passage before a test tone we can start measuring when silent passage starts and to the test tone this will give same effect as on / off.
Regards
Toshikazu Yosumi of Technics did the same thing in 1979 and found there was a correlation, but perhaps he had better resources than Arthur ?
You're quite right. Such test tracks were suggested and supported, not just by me, but I think we lost the debate on that AFAIK when I last looked.... I've given up the record up as a frustrating lost cause and missed opportunity to get tests that actually test the right things, but accept my part in that.
LD
Pink fish was where polar plot analysis of 'instantaneous' speed emerged about 5 years ago? IIRC it was good even then, and IMO likely to be far better than anything available in 1979.
Digital analysis tools post-date the 1st great vinyl era. AFAIK its only now, and by a few enthusiasts like us, who have ever applied them to vinyl playback, because vinyl was seen as a dead technology.
Dead? I saw new vinyl for sale in Sainsbury's today......... and that's a supermarket !
LD
I love these "once and for all" type conclusions in audio
Why does perceived pitch stability improve when changing the drive system from a belt to something else then? You really believe program modulation has nothing at all to do with it?
Why does the best bass always come from idlers, or monstrously powerful DDs?
The debate is not lost. And there is plenty of run time left on the record. If you are willing to produce the digital files they can still be added*. We are missing your input!
*and yes aware of the 'issues' around that and not bringing them up here.
My table is a belt driven one. I am highly confident that my diy air bearing arm with the table can challenge any table and arm combinations in bass areas. I used Graham 2.2 with same table. I could never get the bass performance as I am getting now. I am not saying that table has nothing to do with bass performance but arm plays even larger role in bass performance.
The drive type changes the bass in a very different way. Unless you experiment on the same setup with belt vs friction drive you would not know what i mean. Hard to explain perhaps, but has more to do with drive, incisiveness and rhythm, all qualities not particularly affected by the arm.
Even the best belt drives with super-heavy platters and BLDC motors have this leisurely attitude in the bass, not unpleasant and not necessarily wrong, but very different. IMHO only of course.
Even the best belt drives with super-heavy platters and BLDC motors have this leisurely attitude in the bass, not unpleasant and not necessarily wrong, but very different. IMHO only of course.
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