conical versus ellipticals

[Ldg]

Perhaps more of these scanning electron microscope studies from AES would shed more light on this matter.

At the molecular level under SEM there's bound to be some damage arising with each playing, but how deep does this extend ? Not far in real terms.......it's not all about temperature, it's about heat. Ever passed your finger through a candle flame ? ......bet your finger had some molecular damage too !

[rito25]

So conical better but higher wear.
Elliptical not as good but less wear.
That to me says go ellipitical.

[Ldg]

Here's part 3 of my calcs on temperature of stylus and vinyl.

Conclusion from part 1 is that typical heat flow rate at stylus/vinyl contact is of the order of 2mW. Conclusion of part 2 is that whatever the temperaure of the contact region, some 1uW is conducted into the vinyl, and this is effective heating power.

This is part 3 and looks at temperature rise of vinyl near the contact region.

Vinyl contact region continuously changes as record moves.

Assume contact region has a surface radius of 3um, stylus/vinyl velocity = 0.33m/s.

In one second, area swept by contact region A = 3um * 0.33*10E+6 um = 10E+6 um^2
From part 2, heat flow rate into vinyl from contact region P = 1uW
then heat flux into vinyl groove wall Y = P/A = 1uW/10E+6 um^2 = 10E-12 W per um
1um^2 = 10E-12 m^2
then Y = 1 W per square meter

For vinyl groove skin depth of 0.1um, volume swept by contact region in one second V

V= A * 0.1um = 10E+6 um^2 * 0.1 um = 10E+5 um^3
1 um^3 = 10E-18 m^3
V = 10E-13 m^3
Specific gravity of vinyl is close to 1 g/cm^3 = 10E6 g/m^3
Weight of vinyl occupied by volume W = V * 10E6 g/m^3
W = 10E-7 g = 0.1ug

In one second, heat flow = 1 uJ
Specific heat of vinyl is close to 1J/gK

Then average temperature rise T of vinyl groove wall skin to thickness of 0.1um

T = 1 uJ / 0.1ug = 10 deg K (celsius)

Obviously, convenient typical values were chosen to make the math plain, but these choices seem reasonable. Point is, there is not significant heating of the vinyl groove wall skin, not enough to melt or deform.

[Ldg]

The contention is that it is only on the surface of the groove, where the stylus contacts, that the vinyl melts for an instant, then re-forms. Apparently this phenomena was OBSERVED by Mr Alexandrovich. The tremendous pressure might have more to do with it than theoretical temperature calculations.

ld,
I noticed that your formula for friction seems inadequate. Although 1.5g VTF is reasonable, the actual force is dramatically higher due to the size of the contact area. Was this taken into consideration?

No dispute that this phenomenum happens, in fact it's a normal part of contact physics. Surfaces mesh under pressure, the composite can be low friction, but it happens over very short distances at these pressures, orders of molecules. Not unusual to see much larger contact pressures elsewhere.

Yes, I've fully taken into account the difference between VTF the force (g) that brings about the pressure (g/um^2). Force and pressure are different entities, of course. It was yosh's JVC friction coefficient that opened the door to calculating heat generated by friction. This coefficient is simply validated by observation of skate force.

[analogaudio]

Paladin wrote

"A record is designed to use a conical tip and the elliptical tip gets very little use out of its potential. "

This is not true from the disc mastering viewpoint, the master groove is cut by a sapphire the shape of a chisel and if played back using the same stylus would be free from some types of tracking distortion. The use of a conical playback tip stylus was an economy measure and not because it did the job right. The elliptical playback stylus design was introduced because conical does not get the job done right. Elliptical is not perfect but introduces less tracking distortions than than conical.

Ted

[Paladin]

I didn’t know that albums were not designed for conical tips.

[Thomas_A]

Thanks Luckdog for the calculations. There are now two calculations showing that temperature rise in vinyl is small.

[Thomas_A]

""Role of Scanning Electron Microscope in Disc Recording." George Alexandrovich. AES Preprint 1274, 58th Convention.
Among other subjects we investigated was the method of playing records wet. By applying a thin film of water as the record was rotating and playing the groove with an ordinary stylus, it produced unexpected increase in vinyl deterioration in the area where the stylus was touching the groove. Our SEM pictures unveiled extraordinary ripping of the vinyl surface which I can explain only by the fact that the vinyl is not allowed to liquify momentarily under the pressure of a fast moving stylus because of the cooling action of water in the groove. This phenomenon, I believe, is identical to ice skating where one does not skate on ice but actually on a film of water which comes from the ice being momentarily melted under the pressure of the thin metal blade. If ice is too cold, one cannot skate. Evidence of the fact that vinyl melts can be found in pictures taken of record grooves played at different temperatures. "

I do not know exactly what would happen when the record is played wet. Cooling may be one thing, but I am not sure how much that will affect. Another thing might be a weaker contact between stulys and groove because of liquid passing between the stylus and groove, effectively reducing the contact force and area and significantly reduce friction. The end result may a stylus that is forced to stay in the middle of the groove, not following the high-frequency modulations, leading to reduced HF noise but also, tearing of grooves when stylus is constantly bouncing off and on the modulations.

Compare car wheels that loose contact when going too fast on a wet road.

[missan]

Some months ago I did a DSC analysis of a piece from a Decca record.
I found the Glass Transition to be just below 70degC.
As vinyl is a amorphous thermoplastic I believe if this temp is reached there will be a plastic deformation of the vinyl that is permanent.

Following this thread I am totally convinced that the transition in the vinyl is taking place in a very thin layer and is of no importance regarding deformation. If there should be any resamblance with ice skating I believe that the temp above the record´s surface must be closer to Tg temp. The surface pressure when playing will not normally make the vinyl too stressed, it´s still well within the elastic area.
missan
Edit: better spelling

[rayr0683]

Hello All,

I know that the grooves reach temperatures of about 350 degrees farenheit, but never have noticed and sound degradation on any albums that I play, or have played on a consistant basis. I wonder if this is being taken too seriously. It is very important to clean the stylus after every played side of an lp, from accumulated, and caked on gunk, from the heat, and other debris within grooves. It gets baked onto the stylus. However, when reading the studies that have been done with LAST ARCHIVAL RECORD PRESERVATIVE, after a good cleaning with a vacuum record cleaning machine, and also cleaning, and possibly using LAST Stylus preservative, the records that were played many many times, I forget the exact number of times, showed virtually no wear. So, proper cleaning, and the use of LAST products can keep your vinyl as new as possible. I do this myself, and have never noticed any problems. I myself dont use a microscope, but the LAST studies did. Ray

Some months ago I did a DSC analysis of a piece from a Decca record.
I found the Glass Transition to be just below 70degC.
As vinyl is a amorphous thermoplastic I believe if this temp is reached there will be a plastic deformation of the vinyl that is permanent.

Following this thread I am totally convinced that the transition in the vinyl is taking place in a very thin layer and is of no importance regarding deformation. If there should be any resamblance with ice skating I believe that the temp above the record´s surface must be closer to Tg temp. The surface pressure when playing will not normally make the vinyl more stressed than it´s still well within the elastic area.
missan

[Ldg]

Some months ago I did a DSC analysis of a piece from a Decca record.
I found the Glass Transition to be just below 70degC.
As vinyl is a amorphous thermoplastic I believe if this temp is reached there will be a plastic deformation of the vinyl that is permanent.

Following this thread I am totally convinced that the transition in the vinyl is taking place in a very thin layer and is of no importance regarding deformation. If there should be any resamblance with ice skating I believe that the temp above the record´s surface must be closer to Tg temp. The surface pressure when playing will not normally make the vinyl too stressed, it´s still well within the elastic area.
missan
Edit: better spelling

I agree, Missan. Even allowing for 'worst case' friction coefficient, high VTF, slowest velocity and smallest contact radius, temperature rise in the first 100nm skin of groove wall is below 20 deg C, well below glass temp even at high ambients.

Interesting that factors VTF, friction co-efficient, and contact area radius (inversely) influence temp rise linearly, and there's not a clear advantage between spherical or eliptical. Line contact has an advantage if increased line height offsets increased friction coefficient, but it all seems small and not significant.

I know that the grooves reach temperatures of about 350 degrees farenheit, but never have noticed and sound degradation on any albums that I play, or have played on a consistant basis.

That's because of what Missan describes. There's not enough heat associated, doesn't even significantly heat or deform 100nm groove skin.

[Thomas_A]

Also ice skating has been problematic to solve. So I am not very suprised that there are many types of explanations out there.

[desktop]

Hi all, I'm not sure that playing a vinyl record once is a good test of any theory about how spherical, elliptical and line contact styli affect the groove walls on a disc. The best case seems to be a lubricated stylus that is highly polished and is of a high quality hyper-elliptical shape (or better) with sufficient tracking force to hold the stylus in contact with both walls of the groove all the time, and equally. Once we get to a lubricated and highly polished spherical stylus (like a Denon 103), playing a new disc with sufficient tracking force and correct anti-skating, I think you'll find vinyl wear in the grooves goes way up (at least according to the NAB).

The reason for this seems to be that if an album is popular, and even if it is cleaned carefully every time between plays once per day, and even if the stylus is cleaned and lubed every time it is used for an album side, the "track" in the bottom of the grove caused by a spherical stylus can be seen clearly by about the 60th play. The disc of Iron Butterfly's "In a gada da vida" (?SP?) is played full length each time (it covers one side of the disc). We have a station here in Kansas City that often plays the Tangerine Dream album sides straight through, as well as M Olfield's Tubular Bells for their "New Age" show. Many many classical discs were played tris way. It is clear even with a standard microscope at 300x that there is a rippling effect of wear on the contact areas of these records.

As an AES member this problem was brought to our group 10-12 years years back. A radio station playing classical and other full-length-play albums was finding many albums unavailable on CD. These albums were also difficult to source on vinyl. The cost of maintaining a music library at a fastidious station was substantial. We had the station use calibrated Stereohedron Stanton cartridges whenever possible (681 S). The records in question seemed to last 3x to 4x times as long, before noise became objectionable due to the contact "track" that formed after as few as 60-70 plays using the Denon 103R catridge (also calibrated for Radio Station use). We (AES members) went in and chose the best of the remaining best turntables and arms. We set them up properly, and installed the cartridges ourselves. The problem was eventually solved (the high cost of replacement vinyl) by burning all these discs to CD once in a while and automating the shows.

But the problem is still there. The lubricants in the vinyl itself may "burn off" and then under-surface lubricants may re-mix with the fast melting vinyl (I prefer the view that the vinyl only softens, not fully melts). But eventually this built-in lubricant inside the vinyl formulation is gone. This is most obvious in discs made of 1/2 crushed vinyl and 1/2 new vinyl. It is obvious when viewing the grooves after a while, that the crushed vinyl particles are "showing thru" like cobblestones will eventually show thru when a thin layer of blacktop is put over them to produce a smoother ride in a car.

So play a new disc once and check for groove wear. Since my college minor was statistics I then suggest this test sequence; play it 10 times and check for wear. Use three discs; one with a spherical stylus, one with an elliptical stylus and one with a line contact stylus. Then check after 30 plays, then 60, then 100, then 150, then 225 plays and so on with a maximum of 1721 plays (if there is no visible creation of a new contact wear track in the groove bottom after 1721 plays, there is no need for further tests.), and compare how fast the track/noise wear occurs at the bottom of the groove. The spherical will always be worst, but the elliptical will only be useful for about 25% longer, while the line contact stylus may be useful 100% longer than the elliptical. Other styli like shibata and hyper-elliptical etc. will be between elliptical and line contact styli, while the best 6 designs (Stereohedron, Microridge, MicroTracer, Replicant, VdH1, and Gyger 1) will go the longest without obviously making a track due to contact in the groove. I'm trusting that there are no huge improvements in vinyl in 1992 since CBS Labs went thru this testing regimen.

[Ldg]

Thanks for interesting insight, desktop. One thing I don't get from your post is why should vinyl wear in the grooves go way up with a lubricated and highly polished spherical stylus (like a Denon 103), playing a new disc with sufficient tracking force and correct anti-skating. Can you explain more please ?

Some months ago I did a DSC analysis of a piece from a Decca record.
I found the Glass Transition to be just below 70degC.
As vinyl is a amorphous thermoplastic I believe if this temp is reached there will be a plastic deformation of the vinyl that is permanent.

Following this thread I am totally convinced that the transition in the vinyl is taking place in a very thin layer and is of no importance regarding deformation. If there should be any resamblance with ice skating I believe that the temp above the record´s surface must be closer to Tg temp. The surface pressure when playing will not normally make the vinyl too stressed, it´s still well within the elastic area.
missan
Edit: better spelling

Calculation yields 15nm as typical groove skin thickness at which glassing temperature is exceeded at 20 deg C ambient. This is 150 Angstroms, about the size of vinyl polymer molecules, though that can vary. About the size of a small virus ! Accumulated groove wear perhaps involves progressive changes and erosion for these first few molecular layers, through glassing, leaching of plasticisers, fracturing of polymers, and mechanical surface interaction with the stylus.......?