The attachment is from the March 1977 BAS meeting, reported in:”THE B.A.S. SPEAKER” Volume 5, Number 7, April 1977
George
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Sy,
I think that temperature rating must be another of those not so obvious things here as that would be above the melt point of vinyl and would just melt the groove away. So there has to be more to it than just that, the stylus is moving at a rate and the heat dissipation would have to be one factor alone into the vinyl. I would think that the differences in hardness between a diamond or sapphire and the vinyl would have more impact than the temperature and any dust or dirt would change things again.
Chris,
that sounds like it would be a wild ride and you would definitely get my motion sickness going on a cantilever that long....
I think that temperature rating must be another of those not so obvious things here as that would be above the melt point of vinyl and would just melt the groove away. So there has to be more to it than just that, the stylus is moving at a rate and the heat dissipation would have to be one factor alone into the vinyl. I would think that the differences in hardness between a diamond or sapphire and the vinyl would have more impact than the temperature and any dust or dirt would change things again.
Chris,
that sounds like it would be a wild ride and you would definitely get my motion sickness going on a cantilever that long....
Well, yes, and you also have diamond (the best thermal conductor) tightly bonded to a heatsink) in direct contact, so the thermal "outflow" is pretty high. The groove itself is integral to a large mass of a material with high specific heat. When you examine a record which has been played once, you don't see a melted trail though the groove.
Nope, I just don't see it.
Nope, I just don't see it.
Attachment 1
The upper curve of fig. 5 bears a striking resemblance with the curves that Joachim showed. The peak (it is a peak Joachim, sorry for the noise!)is due to tip-record interaction/resonance. From the following article:
http://shure.custhelp.com/ci/fattach/get/29245/
The trackability curve which draws as the inverse of the mechanical impedance of the tip is a very indicative figure. I havn’t seen many manufacturers show such curves (Denon publish mechanical impedance curves, see DL-103 attachment 2, but limits the data to 20KHz, while the resonance is above it.)
George
The upper curve of fig. 5 bears a striking resemblance with the curves that Joachim showed. The peak (it is a peak Joachim, sorry for the noise!)is due to tip-record interaction/resonance. From the following article:
http://shure.custhelp.com/ci/fattach/get/29245/
The trackability curve which draws as the inverse of the mechanical impedance of the tip is a very indicative figure. I havn’t seen many manufacturers show such curves (Denon publish mechanical impedance curves, see DL-103 attachment 2, but limits the data to 20KHz, while the resonance is above it.)
George
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Since I've been working on and off on some phono preamp ideas for the last several years, I was initially a bit annoyed that I had yet another feature to consider
However, if it really translates into sonic benefits I'm all for it. One would think that about everything that could ever be considered in vinyl reproduction has been considered. But from a modest survey of current and past products, coupled with diy-oriented articles, it seems this isn't the case.
Listening tests, especially vinyl-based ones, are fraught with peril. Whatever the stylus temperature, tracking forces, record warp, there is general agreement that one doesn't want to play the same LP in quick succession, so the level-matched switching between overdamped and normal needs to be more-or-less seamless. Oddly, my experiences with my own listening tests are that I tend to be more objective than most people --- even when I hope to hear differences and know to what I'm listening, when there is nothing there I don't usually manufacture it. A case in point would be the audition of the Tice-like stuff, where I would have been delighted to hear something substantial and that warranted further investigation.
So perhaps I can move to realize a setup and test the effects for a given cartridge at least as I hear them. If a group of listeners, as reported by van Maanen, can discern in 30 seconds the difference, and it wasn't due to level changes or frequency response, then I ought to be able to as well. Whether I like the change or not is another story.
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You could infer it to some extent knowing the thermal conductivity of the diamond and the rest of the assembly, and its heat capacities, and measuring the temperature further away. Or, with a small telescope and an infrared camera? We're back into emissivity issues for which we can correct.
But if the tip sustains such a temperature it will necessarily approach an equilibrium temp and warm up the assembly. I wonder how opaque clear vinyl is to IR? Maybe image from the other side of a platter with some holes in it?
bcarso,
I can't imagine that even if the temperature of the interface does momentarily heat up as was said earlier that the mass of a vinyl record would hold much heat over the time it would take to play an album. The heated area is tiny in comparison to the mass and the dissipation alone would make me think this not likely. Perhaps if you were playing the same few tracks repetitively that would happen but playing an album through I can't see the mechanism for that. If you have ever seen and injection molded part made you would have to question that premise. From injection to ejection in the mold would be in seconds and that would be from a large mass in the injection barrel of an injection machine. Something doesn't add up to what is going on here.
I can't imagine that even if the temperature of the interface does momentarily heat up as was said earlier that the mass of a vinyl record would hold much heat over the time it would take to play an album. The heated area is tiny in comparison to the mass and the dissipation alone would make me think this not likely. Perhaps if you were playing the same few tracks repetitively that would happen but playing an album through I can't see the mechanism for that. If you have ever seen and injection molded part made you would have to question that premise. From injection to ejection in the mold would be in seconds and that would be from a large mass in the injection barrel of an injection machine. Something doesn't add up to what is going on here.
Remember we're talking about the temperature at the stylus tip, not that of a wake of molten vinyl which rapidly cools due to the heat capacity. The stylus will heat up, the diamond will conduct superbly well to the cantilever, and so on. After a while some point not too-far-removed will experience a temperature rise, and we can back out what the temperature had to be at the tip.
If it really is anything like the stated temps, we'll see a measurable rise not too far away, and with a thermal time constant not all that terribly long. There are some very tiny thermistors that could be affixed somewhere nearby that wouldn't drastically interfere with transduction of vibrations.
As far as the LP itself, I seem to recall someone saw deformations that slowly relaxed back into shape given some time. This too could be re-investigated today with some new tools. For example, use a laser table to play and digitize the record, then play with a stylus, then back to the laser table. Compare the digital files before and after.
I think (always a bad sign) that the temperature numbers were calculated from contact pressures required to accelerate the stylus at the hundreds or thousands of G's (not as surprising a number as it may seem!) from a teeninsie contact area. The actual "groove" geometry traced by the stylus is *not* on the surface, but includes a certain amount of the inner vinyl. One reason why the laser scanners are so different - the other is the insane amount of noise reduction needed without a stylus' "averaging". I don't think it's a question of friction, or anything like that. Simply enormous pressure in a tiny space.
When Lord Kelvin (now there's a name to conjure with!) (and his daughter invented computin') calculated the age of the Earth it was by temperature rise caused by gravitational pressure. He was way off because he didn't know about radioactivity yet, but his numbers were right for his day. I'll try to find some numbers to back up the 400 F claim, so I won't be as wrong as The Man ultimately was.
Thanks,
Chris
When Lord Kelvin (now there's a name to conjure with!) (and his daughter invented computin') calculated the age of the Earth it was by temperature rise caused by gravitational pressure. He was way off because he didn't know about radioactivity yet, but his numbers were right for his day. I'll try to find some numbers to back up the 400 F claim, so I won't be as wrong as The Man ultimately was.
Thanks,
Chris
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Lord Hornbeck,
Thanks for the information. I would imagine that some of the heat would go up the cantilever until some equilibrium was reached and that most of the heat would be lost to air as the surface area of the stylus tip must be large compared to the diameter of the cantilever. But I am just guessing on that. Very interesting phenomena that I had never considered before. Still can't see the groove retaining that much heat over time though, the mass and surface area would be so much greater than the small contact area.
Thanks for the information. I would imagine that some of the heat would go up the cantilever until some equilibrium was reached and that most of the heat would be lost to air as the surface area of the stylus tip must be large compared to the diameter of the cantilever. But I am just guessing on that. Very interesting phenomena that I had never considered before. Still can't see the groove retaining that much heat over time though, the mass and surface area would be so much greater than the small contact area.
Absolutely. And the big temperature numbers would be for the vinyl itself, and not necessarily at the surface. This is over my head, but having opened my big mouth I need to find out what truth I can, or at least figure out where the numbers came from.
Has anybody else noticed the long-long term memory that vinyl records seem to have? Could be just *my* poor memory (and likely!) but it seems like records that seemed worn and beat a few decades ago "recover" after a long nap. Or I could be getting older and more forgiving. Thoughts?
Thanks,
Chris
Chris,
The only thing that I could attribute an album recovering over time is the phenomena of memory. The other standard mechanism in plastics is called creep. In one the load over time causes the material to move, just as glass will flow over time because it is not truly a solid. But that type of deformation is usually not reversible. But memory is when the molecules have been created in a specific way, a matrix, and though they have been pushed around they would have a tendency to return to the original shape over time as the stresses are relieved. Since an album is made in a mold and the grooves are set the shape would have that original pattern in the matrix and this could explain the return back to the original shape. I know that there would be more to it than that as dirt and a worn stylus would cut some of the vinyl over time and once material is removed it would be gone for good. And no I am not making this stuff up off the top of my head, been molding plastics for far longer than I care to admit......
The only thing that I could attribute an album recovering over time is the phenomena of memory. The other standard mechanism in plastics is called creep. In one the load over time causes the material to move, just as glass will flow over time because it is not truly a solid. But that type of deformation is usually not reversible. But memory is when the molecules have been created in a specific way, a matrix, and though they have been pushed around they would have a tendency to return to the original shape over time as the stresses are relieved. Since an album is made in a mold and the grooves are set the shape would have that original pattern in the matrix and this could explain the return back to the original shape. I know that there would be more to it than that as dirt and a worn stylus would cut some of the vinyl over time and once material is removed it would be gone for good. And no I am not making this stuff up off the top of my head, been molding plastics for far longer than I care to admit......
While Chris his chasing that temp thing (thanks Chris, much appreciated) can I briefly return to the overload electrical damping? Something is bothering me.
It seems most here agree that electrical coil damping does not lead to mechanical cantilever damping; that is, the cantilever resonances are still there but are no longer in the electrical output of the coil, and this leads to a smooth freq response. But this damping system can not differentiate between unwanted mechanical resonances and wanted vibrations from signals on the record. Are we not loosing signal content with this damping method?
jan
It seems most here agree that electrical coil damping does not lead to mechanical cantilever damping; that is, the cantilever resonances are still there but are no longer in the electrical output of the coil, and this leads to a smooth freq response. But this damping system can not differentiate between unwanted mechanical resonances and wanted vibrations from signals on the record. Are we not loosing signal content with this damping method?
jan
Jan,
Just as you have stated so eloquently the problem with trying to electrically damp a mechanical resonance with the phono cartridge the same principals apply to electrical filters that are placed in electronic crossovers to dampen mechanical resonance with loudspeakers. I just sit there and keep my mouth shut every time I see someone say they are going to use a notch filter to remove the mechanical resonance of a loudspeaker. Isn't going to ever happen, the resonance has nothing to do with the electrical signal, the excitation can be caused by many other physical phenomena and unless you physically change the loudspeaker the original reason for the excitation still exists. Learned this long ago, you can use electrical equivalents to describe the functions but that does not mean they are exactly equivalent. Just a way to understand and study the functions, not something that can overrule physics.
Just as you have stated so eloquently the problem with trying to electrically damp a mechanical resonance with the phono cartridge the same principals apply to electrical filters that are placed in electronic crossovers to dampen mechanical resonance with loudspeakers. I just sit there and keep my mouth shut every time I see someone say they are going to use a notch filter to remove the mechanical resonance of a loudspeaker. Isn't going to ever happen, the resonance has nothing to do with the electrical signal, the excitation can be caused by many other physical phenomena and unless you physically change the loudspeaker the original reason for the excitation still exists. Learned this long ago, you can use electrical equivalents to describe the functions but that does not mean they are exactly equivalent. Just a way to understand and study the functions, not something that can overrule physics.
If I have two complementary filter functions (say, a peak and a notch) with the same amplitude, phase response, delay, and Q, why would they need the same mechanistic cause in order to cancel? After all, on the other end of the chain, it's very common to use the combination of mechanical and electrical transfer functions to achieve a particular acoustic transfer function (e.g., a Linkwitz transform in an electrical filter to extend the mechanically-limited bass).