Talking about religion, prophets and believers.
Well, for the moment no head haven't been cut yet, thanks to the virtual aspect of Internet, but we're not far away.
Seems nothing of consequence......but isn’t that part of the problem?
I wouldn’t wave my arms so much if I didn’t hear many of the controversial things that supposedly can’t/aren’t measured.....and it’s not because I went looking for it, most all these things I’ve heard then sought out answers.
It’s just that the answers I’m finding are all in minority camp. 😛
Ah sorry I'd started editing before you did that. Shure did a load of stuff for the V15 series where they claimed some horrendous modulation levels. I think they over egged a few things as the inference was that only shure cartridges would track lots of records out there. BUT I can't prove that without measuring some of these records for myself. I really should get off the internet and do something useful 🙂
I think it's the whole problem because it means we still don't know what is being referred to.
Ok, correction:
"I'm sure it sounds better than the DAC somebody **** smeared and you listened with Richard."
Please do and please try to make a hypothesis and propose some experiments that can be done. I've already said the distortion does not appear to change over a 10:1 groove velocity while some equations predict an increase in elastic deformation which quickly increases distortion. As to Shure trackability has nothing to do with this.
I don't see this as a "done deal" decades ago.
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Bill,
It would not be the temperature rise that would distort a vinyl record it would be the yield strength. Probably under 10,000 PSI for a record formulation but above 5,000 PSI. So the question would become what is the contact area and force applied to it? Questions would probably also include the width of the groove, effective mass of the tip and stylus velocity.
My quick estimate is a spherical stylus at 3 grams tracking force resting would be under 10% of the yield strength.
It would not be the temperature rise that would distort a vinyl record it would be the yield strength. Probably under 10,000 PSI for a record formulation but above 5,000 PSI. So the question would become what is the contact area and force applied to it? Questions would probably also include the width of the groove, effective mass of the tip and stylus velocity.
My quick estimate is a spherical stylus at 3 grams tracking force resting would be under 10% of the yield strength.
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Ed there is a rich body of literature full of analyses with real numbers for all this. Where did you get that number for the transition from elastic to plastic deformation of vinyl? In fact it is a very complicated problem involving stress tensors that does not scale linearly.
To make my point take a fine tungsten needle and exert the force of a few grams on a pane of glass. As in the LP analogy there are tons per square inch exerted, but take a one square inch contact area and place tons of weight there.
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Scott
It is a problem encountered daily everywhere material is formed by stamping or bending. Tables of yield strength are easily found and are given on the material data sheets.
I use "Precision Steel" for forming cases. It has a specified yield strength of 30,000 PSI +/- 5%. A quality very much needed to insure repeatable stamping or bending results.
Not surprisingly the vinyl intended for record stamping also has close tolerances on the important properties like melting point and such. A local plastics plant had an issue where something happened in their processing and the product parameters no longer met the data sheet specifications. A major issue as what shifted was not clear and tweaking the process to give the desired results is very close to a black art. Very much in the realm of trade secrets.
It is a problem encountered daily everywhere material is formed by stamping or bending. Tables of yield strength are easily found and are given on the material data sheets.
I use "Precision Steel" for forming cases. It has a specified yield strength of 30,000 PSI +/- 5%. A quality very much needed to insure repeatable stamping or bending results.
Not surprisingly the vinyl intended for record stamping also has close tolerances on the important properties like melting point and such. A local plastics plant had an issue where something happened in their processing and the product parameters no longer met the data sheet specifications. A major issue as what shifted was not clear and tweaking the process to give the desired results is very close to a black art. Very much in the realm of trade secrets.
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Ed the problem of pressure (stress) applied at a small point to a material is a highly non-linear problem. Just like heat applied at a small point to a block of material. I don't think anyone has ever presented an all physics solution to this problem.
It seems to me impossible to fulfill this requirement as GD differences are a *consequence* of other factors.
By example, time aligning speakers change the G.D. curve. But has impacts on the response curves at the crossing frequencies. (Same frequencies additions with phases differences). Response curve changes our tonal perception. Group delay impacts transients (precision of attacks). I use a DCX2496 to deal with those parameters.
In my KEF LS50 Wireless, there is too an optional delay to align or not bass and treble speakers delais. The changes in precision are obvious.
BTW: I never made serious "evaluation" of group delay audibility factors. Just a compilation of practical experiences. By example, digital and analog equalisers are day and night. And what else than phases turn differences ?
I make no claims about temperature rise. I don't know how to translate from pressure to temperature, and I'm not certain that the guys back in the day really could either. But I'd trust their guesses over my own. My case goes:
Peak (each channel) stylus velocity at NAB 0VU = 5 cm/s. At +20 VU peak acceleration is then about 3km/s/s or about 320 G. Not all recordings are so conservative, and peaks of +30 VU must be expected, or a little more. Lets call it 1000 G's for maximum drama. (But real.)
An excellent, perhaps no longer available, stylus might have an effective moving mass of .25mg - we'll use that as a conservative best case. So the vinyl surface must exert a peak force on the stylus of 2.5 mN.
Assuming a contact area of 25um ^2 (ballpark for modern shapes - no fricking idea how they come up with it) peak pressure at the contact points is 2.5^-3 / 2.5^-5 = 100 Pascals = 689500 psi = 344 tons per sq inch.
My argument goes that we can't apply day-to-day rules of thought to vinyl playback. It's more profound than meets the eye, and more interesting!
Much thanks, as always,
Chris
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Stylus point pressure on moving vinyl groove :
I was under the impressions that, for the very same reason recording industry to overcome groove damage changed vinyl speed from 78rpm to 45-33rpm. Then changed pressure exerted on the groove and stylus profile so that stylus shape has maximum contact points with groove modulation(distributes pressure), than improved upon stylus tip mass.
So even if we can all agree that it produces heat, distortion, noise and deformation. My guess would be it would be very very small. And can safely be ignored amongst other major drawbacks of vinyl playing if one wants to listen to vinyls.
Following video reports about 0.5 to 1 db. loss in amplitude of high frequencies and little added noise in midrange. (After 100 playes i.e.)
YouTube
Regards
I was under the impressions that, for the very same reason recording industry to overcome groove damage changed vinyl speed from 78rpm to 45-33rpm. Then changed pressure exerted on the groove and stylus profile so that stylus shape has maximum contact points with groove modulation(distributes pressure), than improved upon stylus tip mass.
So even if we can all agree that it produces heat, distortion, noise and deformation. My guess would be it would be very very small. And can safely be ignored amongst other major drawbacks of vinyl playing if one wants to listen to vinyls.
Following video reports about 0.5 to 1 db. loss in amplitude of high frequencies and little added noise in midrange. (After 100 playes i.e.)
YouTube
Regards
Cheap bad quality parts are expensive, because they can't satisfy you on the long run: frequent renewals expected.
But there not always a correlation between prices and qualities, so depending on each budget and goal expected, careful study has to be done to optimize quality/price ratio and hit our targets. ;-)
When we only have a limited budget, we can't afford any snobbery.
So, I don't see the usefulness of these crusades against audio fooleries: I don't mind that people who have money to throw out the windows ... throw it out the windows.
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For interest sake, here is a graphic from the Holman article on this subject. Note the y axis should read milliseconds and not seconds.
An LTspice sim of an all active RIAA only introduces about 10us GD at LF - it increases to > 240 us at very high frequencies (MHz).
I was quite concerned about this issue because my RIAA includes a 40 dB/decade HPF - but the GD is low single digit ms at 20 Hz when switched in ie not an issue.
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Clarification on the above post - I am talking about 'differential' GD at 20 Hz compared to GD in the pass band above the filter. Absolute GD in the passband is 18 ms
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