conical versus ellipticals

[Thomas_A]

I think I got the groove width wrong... its only in lead-in groove. Otherwise only a minimal groove width is specified, around 30-35 um, perhaps an average of 50-60 um. So I suppose a line-contact stylus with 70 um radis will be reading the groove at the surface as well, where other distortion may occur.

Perhaps thats why the line-contacts with smaller diameters (30-50 um) are preferred by some makers (Lyra?) when playing used records?

Or perhaps I got the geometry all wrong...

[fantasia]

Hi Thomas!!!
good point i wish i knew both these carts are from the 1970s(late) and getting specs for the stylii would be difficult but gee they play worn records quite well with low noise, it would appear that they are going below quite a bit of ware!!! Which would suggest smaller radii than would be "conventional"

what ever that was at the time!!!!!
they playback stereo very nicely on a low wear Lp out of all proprtion to the cost of the carts actually.


regards

fantasia

[Ldg]

I think I got the groove width wrong... its only in lead-in groove. Otherwise only a minimal groove width is specified, around 30-35 um, perhaps an average of 50-60 um. So I suppose a line-contact stylus with 70 um radis will be reading the groove at the surface as well, where other distortion may occur.

Perhaps thats why the line-contacts with smaller diameters (30-50 um) are preferred by some makers (Lyra?) when playing used records?

Or perhaps I got the geometry all wrong...

I've never understood what dimension eg 70um radius means on a fine line stylus, because I'm sure min groove width at top of groove is less than this.........50um? so can't mean a traditional radius as in spherical/eliptical sense, it wouldn't fit ! Perhaps its the arc radius on the contact line?

Sibilence probably mostly IM distortion landing around 3-6kHz, could be stylus or cantilever self resonance...........or mistracing hf.

I've cracked the melting calculation BTW, pretty sure can now prove there's no melting. Will post derivation and calculation once I've doubled checked.

Lastly, those contact areas lini posted seem strangely large perentage cf stylus size/wavelength, thinking about it.........are units correct?

[Thomas_A]

I think I got the groove width wrong... its only in lead-in groove. Otherwise only a minimal groove width is specified, around 30-35 um, perhaps an average of 50-60 um. So I suppose a line-contact stylus with 70 um radis will be reading the groove at the surface as well, where other distortion may occur.

Perhaps thats why the line-contacts with smaller diameters (30-50 um) are preferred by some makers (Lyra?) when playing used records?

Or perhaps I got the geometry all wrong...

I've never understood what dimension eg 70um radius means on a fine line stylus, because I'm sure min groove width at top of groove is less than this.........50um? so can't mean a traditional radius as in spherical/eliptical sense, it wouldn't fit ! Perhaps its the arc radius on the contact line?

Sibilence probably mostly IM distortion landing around 3-6kHz, could be stylus or cantilever self resonance...........or mistracing hf.

I've cracked the melting calculation BTW, pretty sure can now prove there's no melting. Will post derivation and calculation once I've doubled checked.

Lastly, those contact areas lini posted seem strangely large perentage cf stylus size/wavelength, thinking about it.........are units correct?

Yes, I cannot really see how they are defined for a line-contact since a front radius of 70 um cannot fit into the groove; rather it must be placed above the record surface. So talking about a front radius in line contacts is very confusing. As I understand it the conical 18 um should contact the groove walls approx 1/3 to 1/4 from bottom of groove and never go further than 1/2 of groove at minimum groove width (around 30-35 um). If the line contact-styliis contact "patch" extend to the surface there is a risk of introducing distortion from the vinyl surface structure (minor scratches, and deformations caused during cutting that are present at the upper part of the groove). In that case a round/elliptical stylus or a shorter line stylus would be better.

Inner groove distortion is interesting since it was shown in some paper that IM distortion has a peak around 5 kHz for inner groove (elliptical stylus), but around 8 kHz for outer grooves. This would fit with higher sibilance problems (sss-sounds) in the innergrooves, irrespectively of wear. I do not know if this pattern is general for vinyl or if it applies to elliptical stylii only.

[Thomas_A]

Hi Thomas!!!
good point i wish i knew both these carts are from the 1970s(late) and getting specs for the stylii would be difficult but gee they play worn records quite well with low noise, it would appear that they are going below quite a bit of ware!!! Which would suggest smaller radii than would be "conventional"

what ever that was at the time!!!!!
they playback stereo very nicely on a low wear Lp out of all proprtion to the cost of the carts actually.


regards

fantasia

Thanks, the Shibata profile has been reintroduced by Ortofon in the 2m black, which is an older design than the vdh/FG. Its dimensions are 6/50 instead of the FG 5/70, which means it should ride a little lower, or at least, it will touch the upper part of the groove less than the FG. It may track older records better, perhaps.

The problem with the Shibata is that the contact line is not straight as in the vhd/FG, but curved, meaning that the stylus may have some "false" vertical movement. I asked Ortofon why they chose the Shibata over the FG since it is an older design. They answered that it is indeed an older design but pointed towards their Jubilee, which has gotten really good response. Nevertheless their top of the line has instead the "replicant" stylus, with dimension of 5/100, i.e. even bigger front radius than the FG at 5/70. I cannot however understand what this means, if the portion anyway rides above the vinyl surface; an FG 5/70 should not be different from a replicant 5/100 in terms of contact profile. But then I may have the geometry thoughts all wrong; perhaps someone that knows better can explain?

[missan]

The width of the needle, (and also really the thickness), is not totally defined by these radii that are normally given.
One needs also information where the center of the radii are placed.
There is not really so much difference in contact area between 50µm and 70µm, they can have the same width.
Personally I have found that I like the Shibata`s profile the best.
missan

[KentT]

For Stereo discs as a rule, I favor Line Contact styli in good arms. For pre-1955 Mono LP, 45 RPM discs made from Styrene, and worn 45 RPM singles, I love conical styli of better grade. Also, conicals are preferred for most broadcasting use demanding backcueing.

[Ldg]

.....Yes, I cannot really see how they are defined for a line-contact since a front radius of 70 um cannot fit into the groove; rather it must be placed above the record surface. So talking about a front radius in line contacts is very confusing. As I understand it the conical 18 um should contact the groove walls approx 1/3 to 1/4 from bottom of groove and never go further than 1/2 of groove at minimum groove width (around 30-35 um). If the line contact-styliis contact "patch" extend to the surface there is a risk of introducing distortion from the vinyl surface structure (minor scratches, and deformations caused during cutting that are present at the upper part of the groove). In that case a round/elliptical stylus or a shorter line stylus would be better.........

Line contact stylii have the line running at 45 deg vertical, i.e parallel to the groove wall. But I suppose it is not really a straight line, rather an arc segment with a large radius, that must be what is meant. The minor radius I take to mean the front-back contact line curvature, similar to eliptical. If anyone knows better, please shout !

Really, at least 3 radii are needed to specify a stylus profile. Back to eliptical/spherical debate, eliptical being made starts out as a spherical with just one radius 18um. Then front and back are ground away, side radius ground away and bottom profile ground. Thus the front profile still has contact areas on 18um radius in vertical plane, if that makes sense.

I'd be amazed if the contact areas for all types of stylus varied far from an 18um radius in that plane, and that's what sets riding height. It's an IEC standard. I recall it worked out the contact areas are thus seperated by 25um when I drew it once. Again, if anyone knows better, please shout and explain !

[Thomas_A]

Thomas_A,
I don't think Mark Kelly's post on the Asylum regarding tip temps is even in the ballpark. When CBS laboratories tested records for wear, an elliptical or spherical tip contact area was considered infinitely small. One thing that probably was not taken into consideration was that the record is moving and this is not static pressure. If you read page 2 of desktop's thread, that I previously linked to, you'll have a synopsis of some of this information and references to AES articles.
http://www.vinylengine.com/phpBB2/viewt ... e&start=15

I'm not an expert in this, only relating information I have read. But I think some of the AES articles and microscope studies I've seen would give you a different perspective.

The Linn cartridge you mentioned previously is listed as a fine line.

I'm not trying to be argumentative, just presenting some information that I really don't have the time to research. There was a thread previous to 5/07 that had even more information, and AES articles, but I have yet to find it.

But Marks calculation is not the temperature of the tip, but the temperature of vinyl. The tip can be reasonaby hot, without heating the vinyl. vDH says he measured tip temperatures of around 160° (conical) his own vdH around 60°. Some papers have claimed 500°C-1000°C tip temperature, which I have hard to believe. There is a second point; if the dust that accumulates on the tip should meet 500°C-1000°C as suggested in some papers, there should be constant smoke coming from a dusty record. Or should it ever be possible for a stylus to accumulate dust, given a 500-1000°C temperature of the diamond?

[Thomas_A]

Missan & ld, thanks for the explanations,

It must be that the radius of a fine-line defines an arc and not a radius.

[stpa]

...
... Some papers have claimed 500°C-1000°C tip temperature, which I have hard to believe. ...

I do agree. Diamond oxidizes in air if heated over 700 °C. For a quick reference, see:

http://en.wikipedia.org/wiki/Material_p ... of_diamond

Anyway, some claim that what wears down diamond styli is the heat, not the friction over a much softer material, the vinyl. That is, styli are slowly and gradually burned by the heat.

On some styli exact geometry and perhaps their dimensions, the styli patents here in VE might help. See http://www.vinylengine.com/phpBB2/viewforum.php?f=46

[missan]

Anyway, some claim that what wears down diamond styli is the heat, not the friction over a much softer material, the vinyl. That is, styli are slowly and gradually burned by the heat.

Another possible cause to the wear is embedded small diamond particles in the vinyl. Investigations I have done in another field, have shown that one can have a problem with wear if particles become embedded in a soft mtrl that has a friction against a harder mtrl.
missan

[Thomas_A]

I think the wear is not problem to understand since the diamond has the same contact patch; vinyl wears too but the contact for a given position occurs instantly and once per play.

[rayr0683]

Hello All,

I see your comments liking the AT 12 series cartridges. I recently got myself a mint AT 20 SLa cartridge, which I believe also is a shibata stylus. I was thinking of, when I get spare cash, buying a new stylus for it, its the AT 20 SS stylus, which is beryllium cantilever, and supposedly a great cartridge/stylus. Are you familiar with this cartridge? They still sell brand new old stock SS stylus for the cartridge for roughly $100.00 USD....and I was wondering how well these did indeed play on older vinyl that I may have bought used, but have cleaned with my VPI 16.5 machine. I normally clean, and then LAST all my records, and my stylus too, last stylus cleaner and LAST stylus preservative. Thanks for any info...Im using a new Denon DL-110 cartridge also, not sure what kind of stylus tip this is, eliptical?? Thanks Ray

well,
fellow countryman and VE member Missan and i are both attached to two
shibata stylii cartridges the EXCEL Es70x4 and the Audio technica At 11. 12 series the 12s and 12 Sa are both Shibatas as well which play worn and older records exceptionally well!!!!!

And anything less worn better again!!!!

regards

Fantasia