Here's my experience, based on measurements of friction coefficient and noise. Caveats apply because there are always many variables in play, such as quality of diamond, geometric accuracy of shape, polish, setting on the cantilever, and cartridge alignment in 3D. Also, it's a near Herculean task to find and test enough examples to be statistically valid - so it's not !
All other things being equal then, IME the ranking order, best first is:
Spherical
Psuedo eliptical
Line contact
True elliptical
However, much depends on the specific example in practice, because other factors such as those listed above can dominate. Spherical and pseudo-elipticals better tolerate poor setting in the cantilever, and poor cartridge alignment - line contact can be super fussy with small changes making big differences to friction and noise performance IME. It can also be also a very slow and iterative process to find optimal alignment for friction/noise, but worthwhile especially for line contact types which once set up can be left alone.
I also have a loose idea that older vinyl composition better suits spherical profiles, but I have no evidence or measurement supporting that.
Just my 2p worth, but I did invest a fair amount of time testing for myself to explore that question.
Makes sense. Part of the reason I am starting to rethink my views on MM is the ability to swap tips. Not sure if that is just OCD kicking in tho. Since I re-discovered how good some 50s mono recordings are I figured I should at least look into having more optimised playback for different vintages.
plus a re-tip on my benz is not something I can justify at the moment.
plus a re-tip on my benz is not something I can justify at the moment.
As a nod to those who look for a simple solution, I ground a few telescope mirrors in my youth and grinding always used a water/abrasive slurry. There might be something in the lens making literature to shed some light on this issue.
BTW Lucky thank you for all the data this is a real brain teaser thread.
EDIT - a start? http://www.optimaxsi.com/PDFs/BetterPolishingThroughChemistry.pdf
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You're welcome Scott. There are many loose ends or accepted explanations that don't make sense in conventional vinyl playback generally, and quite a few fundamental accepted precepts must simply be flawed..........
Concerning abrasive solutions of debris, there's no doubting the principle. But in the case of wet playback, changes which adversely affect dry playback noise can happen even after the most vigorous cleaning, and need only a single play - however any abrasive slurry of debris is only created behind the stylus.......? Furthermore, the changes are not permanent in the sense subsequent wet playback is noise/distortion free.
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Yes just tonight I came across Harley's principles of vinyl playback "The friction between stylus and groove creates
enough heat (500° F) to melt the groove wall for a brief instant." I suspect 500 F would destroy rather than melt. It's interesting that this groove wall melting has been accepted without question and absolutely no evidence for years.
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polymers certainly orient in response to friction - maybe you could think of the process as involving "melting/refreezing"
a weird case is the "infinite" life of polyethylene bearings lead to its use in replacement hip joints
turned out that cross axis motion in the hip joint caused previously friction/motion oriented polyethylene surface to scrub off as narrow fibrils
which despite polyethylene being physiologically inert - the pointy ends mechanically damaged cells trigging immune response that eroded the bone the ball joint part was glued into
the "solution" was to irradiate the plastic after shaping to give high cross linking
a weird case is the "infinite" life of polyethylene bearings lead to its use in replacement hip joints
turned out that cross axis motion in the hip joint caused previously friction/motion oriented polyethylene surface to scrub off as narrow fibrils
which despite polyethylene being physiologically inert - the pointy ends mechanically damaged cells trigging immune response that eroded the bone the ball joint part was glued into
the "solution" was to irradiate the plastic after shaping to give high cross linking
I hold the opinion that the groove wall polymer surface, in fine detail, typically holds the key to random variation in friction - and therefore the key to crackle-pop noise. But only by eliminating most other candidates, no direct evidence.
Perhaps the vinyl polymer, as it is formed, varies at the surface as to molecular 'grain' alignment, or as to cavities and surface texture? Perhaps detergents can alter the molecular surface texture, with results as per the Pardee paper ? Perhaps wet playback can do too. Yes, all seems plausible IMO.
However, I doubt that dry playback significantly alters the vinyl surface as to friction. I have measured and found no change in friction or surface noise after (dry) playback of virgin vinyl media, up to 10 repetitions. Records seem to be 'born' with a surface noise fingerprint, which survives decades IMO.
The 'melting' myth in the classic sense, ie a thermally induced phase change, just can't be true - not least for reasons sketched out in post #26. I don't know, but would love to find out, what happens at the molecular surface level between the diamond and the vinyl polymer as it gets a tough shear force workout for a few uS. Imperically, however, it typically doesn't result in significant changes to friction IME. It is possible that the molecular friction surface isn't actually vinyl polymer, rather some other constituent of the mix such as a plasticiser, surfactant or lubricant I suppose ?
Idle speculation on my part though. Would love to know.
Hi,
we have a similar discussion at the time about the possibly high temperature values over at the german aaa-forum.
There are quotes that Mr. V.d.Hul had measured up to 160°C (how did he by the way?)
Now we know that extreme temperatures may occur in short time and on small scales.
The imploding bubbles effect of ultrasonic cleaners or the bang of a pistol shrimp for example.
I still though doubt that the rubbing action of diamond on vinyl can create so much energy that the claimed 260°C (500F) or even the 160°C can be verified.
As diamond is a very good heat conductor and vinyl not, the diamond would transfer most of all of the via the glue-joint into the cantilever.
I´d assume that the glue joint softens or even burns under such conditions.
If one takes the inner diameter of a 12" record (60mm, because of slowest speed between needle and groove), the needle tracks at 0.209m/1s or 4.7µs/1µm (unmodulated groove).
Now lets assume a 8/18µm (0.3/0.7mil) elliptical stylus.
SAS-Namiki sources claim a contact area of 20.6µm² while AT-Sources claim 40µm² (contact area = ellipse of 4.5µmx2.5µm, resp. 6.4µmx4µm)
This imples a contact time of each point on the record of less than 0.209x2,5µm, resp 0.209x4µm, hence 12µs, resp. 19µs.
I have no doubt that the vinyl won´t heat up at all in over such a small duration.
The diamond tip but undergoes the rubbing action over the complete playing time.
A tracking weight of 1.5gr would translate into 1.06gr on the groove walls (90° shape of the groove, hence vectorial force splitting by sqrt2).
The weight-per-area calculates than to 515kg/cm², resp. 265kg/cm².
And I remember numbers claiming up to 3.000kg/cm² (for highly modulated grooves).
Now this enormous pressure could certainly heat up the tiny tip mass.
But since the high thermal conductivity of diamond the cantilever would be heated via the glue joint also, like a cooling fin mounted to a transistor.
It´s probabely much too complicated to calculate the instantaneous and mean temperature for such a case, but I assume the energy input into this thermal system to be so small, resp. the thermal mass of the cantilever so high, that at least the mean temperature dosn´t come anywhere near to the above mentioned 160°C to 260°C.
jauu
Calvin
we have a similar discussion at the time about the possibly high temperature values over at the german aaa-forum.
There are quotes that Mr. V.d.Hul had measured up to 160°C (how did he by the way?)
Now we know that extreme temperatures may occur in short time and on small scales.
The imploding bubbles effect of ultrasonic cleaners or the bang of a pistol shrimp for example.
I still though doubt that the rubbing action of diamond on vinyl can create so much energy that the claimed 260°C (500F) or even the 160°C can be verified.
As diamond is a very good heat conductor and vinyl not, the diamond would transfer most of all of the via the glue-joint into the cantilever.
I´d assume that the glue joint softens or even burns under such conditions.
If one takes the inner diameter of a 12" record (60mm, because of slowest speed between needle and groove), the needle tracks at 0.209m/1s or 4.7µs/1µm (unmodulated groove).
Now lets assume a 8/18µm (0.3/0.7mil) elliptical stylus.
SAS-Namiki sources claim a contact area of 20.6µm² while AT-Sources claim 40µm² (contact area = ellipse of 4.5µmx2.5µm, resp. 6.4µmx4µm)
This imples a contact time of each point on the record of less than 0.209x2,5µm, resp 0.209x4µm, hence 12µs, resp. 19µs.
I have no doubt that the vinyl won´t heat up at all in over such a small duration.
The diamond tip but undergoes the rubbing action over the complete playing time.
A tracking weight of 1.5gr would translate into 1.06gr on the groove walls (90° shape of the groove, hence vectorial force splitting by sqrt2).
The weight-per-area calculates than to 515kg/cm², resp. 265kg/cm².
And I remember numbers claiming up to 3.000kg/cm² (for highly modulated grooves).
Now this enormous pressure could certainly heat up the tiny tip mass.
But since the high thermal conductivity of diamond the cantilever would be heated via the glue joint also, like a cooling fin mounted to a transistor.
It´s probabely much too complicated to calculate the instantaneous and mean temperature for such a case, but I assume the energy input into this thermal system to be so small, resp. the thermal mass of the cantilever so high, that at least the mean temperature dosn´t come anywhere near to the above mentioned 160°C to 260°C.
jauu
Calvin
AS for the discussion on the old wet playback system, there may be some logic in this microdust. I was a regular user of the old Lenco cleaner in the 70's and 80's, but the strange thing is that if I use the L-cleaner again, them records are dead quiet again... ( Yes- I still have it,- and a few spare brushes)
No idea. I couldn't reproduce anything like that using a tiny thermocouple attached to stylus top shank. AFAIK no one has claimed to have reproduced it either.
Yes. If the ratio of thermal conductivities is followed, 99.9% of heat from the contact region is conducted by the diamond. Since total friction power is c 2-5mW, that would leave perhaps a few uW for 'melting' vinyl. It's just not going to happen.Calvin said:
The contact region quoted by manufacturers isn't all in contact at the same time, it can't be. The locus of the instantaneous contact lies within the region, but the dimension of the momentary linear contact length is typically less than 1um. So contact time with any point on the vinyl groove is only a few uS.Calvin said:
No, static pressure is out of context here, and besides pressure does not confer heat. The stylus is moving past vinyl surface, dynamics apply, it's very different. Shear is the dominant force in any event.Calvin said:
Any heat transferred to vinyl surface is left behind the stylus, none is recovered. If one considers what energy would be involved in heating vinyl contact region to melting point, it's just obvious there is no way this happens, because the only available energy is from friction, and it's totally inadequate.
With few exceptions, I can only recover wet playback records for subsequent low noise dry play by using a lubricant treatment, I've been unable to recover them by cleaning alone................
It is possible that this is not an actual measurement. It would not be unknown.
Another loose end is why should crackle-pop noise increase during programme material with strong high frequency content ? Good example being frequency test band records at frequencies above c 12kHZ where the test tone might be inaudible (due to hearing roll-off) leaving just an increase in crackle pop noise versus silence between the bands. Also happens in programme material, generally raising the noise floor background for certain loud high frequency sounds.
This puzzled me for ages. I believe the answer is that tracking hf involves high stylus acceleration, as the stylus follows high curvature, and the associated force to track this 'consumes' some of the force budget which keeps the stylus in contact with the groove. As does friction force, consuming the same force budget.
Effectively then the 'force threshold' for friction induced micromistracking (due to random variations in friction) becomes reduced in the presence of other factors which consume the tracking force budget. So crackle-pop noise is more prevalent during difficult tracking, that is why it can be more pronounced during loud hf passages of programme material, for example.
This puzzled me for ages. I believe the answer is that tracking hf involves high stylus acceleration, as the stylus follows high curvature, and the associated force to track this 'consumes' some of the force budget which keeps the stylus in contact with the groove. As does friction force, consuming the same force budget.
Effectively then the 'force threshold' for friction induced micromistracking (due to random variations in friction) becomes reduced in the presence of other factors which consume the tracking force budget. So crackle-pop noise is more prevalent during difficult tracking, that is why it can be more pronounced during loud hf passages of programme material, for example.
The mechanism for an exploding bubble formation (boiling) is different from the mechanism for an imploding bubble formation (cavitation), so is the rapidity vis. the amplitude and the freq content of the pressure shock result.
The size of the bubble determines the low side of the sound spectrum. Large bubbles (as in the boiling kettle) produce sound entering the audible spectrum.
Bubble oscillation coexist with bubble collapse. When a bubble collapses, the rapid resulting pressure change, excites the volume of nearby bubbles into oscillation at their self resonant frequency. Size and pressure varies, so there is a distribution of resonance frequencies. This, together with the continuous bubble implosions makes for a HF 'shaped' noise carpet rather than distinctive frequencies.
There are novel methods and techniques for spatial micro pressure/temperature variation recording. For these methods and many recorded diagrams, a good book is this Recent Developments in Cavitation Mechanisms, 1st Edition | Seiichi Washio | ISBN 9781782421757
Thank you Calvin for all these calculations you performed for us.
The cartridge cantilever is a large enough target for taking a discernible image with a thermal camera during play. A 10 d C temp rise above ambient would be clearly visible. Witch hunters would have flooded the internet with such images. Have we seen any?
Now using bionic sensors, after one side vinyl play, touching the diamond and cantilever with my finger(*) , the other finger(*) touching the body of the cartridge or the vinyl record, I can’t sense a temp difference.
George
(*) Not the same fingers I use to clean the bit of the soldering iron.
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