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Old 25th September 2012, 10:15 PM   #1241
gpapag is online now gpapag  Greece
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Originally Posted by Chris Hornbeck View Post
I'm certainly not an expert, but it does vary enormously with stylus shape. A phono stylus actually traces a path that includes a fairly "liquid" medium. Contact pressures are in the tons per square inch, and operating temperatures are somewhere in the 400 degrees F range (some say higher - I have no way to measure). A stylus shape that elastically deforms the vinyl less will measure as a higher resonant frequency.

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Chris
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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Old 25th September 2012, 10:20 PM   #1242
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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....
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Old 25th September 2012, 10:23 PM   #1243
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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.
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Old 25th September 2012, 10:27 PM   #1244
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I've seen that 400 degree temperature thing being thrown around before. Any idea if anyone actually measured this or if it's one of those legends-that-won't-die? It frankly doesn't make much sense.
It's a really big number fersure, and I've heard bigger, even 700F. You're gonna make me do my homework on this, aren't you? Fair enough, I'll see what I can dig out. Might be in one of the Tomlinson H papers; I'll look there first anyway.

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Chris
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Old 25th September 2012, 10:44 PM   #1245
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Thanks, Chris- hope you don't think I was picking on you. Let me know if you find any data which will make me less stupid.
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Old 25th September 2012, 11:21 PM   #1246
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400 degrees at 10^-8 cm contact area? How would you even measure that?
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Old 25th September 2012, 11:42 PM   #1247
gpapag is online now gpapag  Greece
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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
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File Type: jpg Denon DL-103 diagrams.jpg (162.4 KB, 196 views)
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Old 25th September 2012, 11:44 PM   #1248
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Originally Posted by Chris Hornbeck View Post
Well, the low frequency (effective tonearm mass x suspension compliance) damping is a pretty well fought-over battleground. (I fall out on the high Q end personally, to minimize FM). Nobody ever claims to be able to do this from the electrical side, AFAIK. A two pole high pass with Q=0.5 at 10 Hz can't hurt.

High frequency (electrical) damping seems like a natural to me, if a good enough curve could be made. Modern low Z cartridges pretty accurately reflect the actual stylus' tracing - geometric losses at shorter wavelengths and mass x vinyl compliance resonance somewhere just within or just above the audio range. One trick is that the wavelengths, thus geometric losses, vary from outer to inner. Effective vinyl compliance will vary some as the stylus ages (contact gets bigger; maybe not enough to worry about).

Dunno, what're your thoughts?

Thanks,
Chris
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.

Last edited by bcarso; 25th September 2012 at 11:54 PM.
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Old 25th September 2012, 11:52 PM   #1249
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Originally Posted by wayne View Post
400 degrees at 10^-8 cm contact area? How would you even measure that?
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?
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Old 25th September 2012, 11:59 PM   #1250
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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.
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