Elliptical?

[missan]

Has anyone looked at the Denon sphericals closely?
missan

[Ldg]

Hi missan. I found this. Credit sidandcoke for the original image :



http://imageevent.com/sidandcoke/upclos ... =2&s=0&z=2

It's side on, so can't see the nitty gritty, also mag/scale doesn't allow to see detail near contact region. But, it's a square shank (grain aligned ?), and polish appears fine, as best one can tell. Hopefully someone can post the scoop frontal zoom shot !

[Ldg]

Hi missan, here's a front shot of my moderately worn Stanton 500 spherical :



It is a decent performing spherical. As you can see, geometry is good, polish is good. It's a circular shank. There are no ground flats.

[missan]

Hi LD.
Thanks, I don´t know why I had the feeling that I´ve seen Denon´s sphericals somewhere, and they had a cut front/back. Guess I was dreaming.
missan

[Hepokatti]

Excuse me for being an idiot, but explain me how "front/back" cuts in an elliptical stylus improves contact area with groove wall over spherical? I've always thought that ellipticals are just cut sphericals. Or are the cuts made on sides? I'm really confused.



Here on the left side there is an elliptical stylus, and to my eyes it looks like the cuts are in front (and back). How this improves groove wall contact? :O

[dlaloum]

In theory... (based on that article) - after the front/back cut, they are supposed to get another stage of grinding/polishing achieved via tumbling....

[Ldg]

Yes. The issues are to what extent, if at all, does that extra step happen, and what does it actually achieve? Because if one looks at common ellipticals, the radius on the cut edge, if present at all, typically appears too small to participate or achieve anything.

The image Hepokatti posted is a marketing sketch, unfortunately and has some howlers which are misleading. The scale, especially shank, is hopelessly out, as is proportion. Drawing of the groove is below absolute limit spec for minimum groove depth, IIRC. Bottom clearance looks wrong. It seems to be drawn to convey a marketing concept, which I'm not even convinced is real.

Here's a markup of that image with actual front images of elliptical and FG styli to scale, and you'll see what I mean. In any event, I think this illustrates more realistic contact locations and proportions, and where the elliptical grind, and cut edge, is in relation to it. NB the overall groove depth is too shallow, I think, but that does not change the contact locations or fit :

[flavio81]

Here on the left side there is an elliptical stylus, and to my eyes it looks like the cuts are in front (and back). How this improves groove wall contact? :O

I don't think the elliptical improves contact respect to the conical. Makes no sense.

[flavio81]

Yes. The issues are to what extent, if at all, does that extra step happen, and what does it actually achieve? Because if one looks at common ellipticals, the radius on the cut edge, if present at all, typically appears too small to participate or achieve anything.

The image Hepokatti posted is a marketing sketch, unfortunately and has some howlers which are misleading. The scale, especially shank, is hopelessly out, as is proportion. Drawing of the groove is below absolute limit spec for minimum groove depth, IIRC. Bottom clearance looks wrong. It seems to be drawn to convey a marketing concept, which I'm not even convinced is real.

Here's a markup of that image with actual front images of elliptical and FG styli to scale, and you'll see what I mean. In any event, I think this illustrates more realistic contact locations and proportions, and where the elliptical grind, and cut edge, is in relation to it. NB the overall groove depth is too shallow, I think, but that does not change the contact locations or fit :

You made that image? This is a masterpiece! Great!

[Ldg]

Thx flavio81 ! The FG could be clearer, but the gist is there. Especially for the elliptical.

[Hepokatti]

Thank you ld. Now it makes more sense

EDIT: Might vinyl deformation play some part in where typical elliptical shape could offer advantages pushing the deformed vinyl away differently? Or is the deformation even that big considering modern, rather low stylus pressures?

[phivates]

Looks oval to me, unless the polishing is miraculous. Love tech-speak.

[Ldg]

Thank you ld. Now it makes more sense

EDIT: Might vinyl deformation play some part in where typical elliptical shape could offer advantages pushing the deformed vinyl away differently? Or is the deformation even that big considering modern, rather low stylus pressures?

You're welcome, Hepokatti.

As to vinyl deformation, my opinion is that it does not happen. At least to any significant extent as to affect contact mechanics and radii. But there's a plentiful body of opinion that it does.

If many ellipticals typically actually have the same curvature as sphericals, indentation would be the same irrespective of whether it's zero or some actual number. So it's sort of academic to the main point of this thread, of course.

One of the contradictions to indentation happening, IMO, follows on from consideration of what happens in styli with long contact lengths (major radius), or reduced minor radius. Both drag and indentation would increase, versus sphericals, if typical claimed contact region profiles are true. But friction/drag does not increase.

[Hepokatti]

One of the contradictions to indentation happening, IMO, follows on from consideration of what happens in styli with long contact lengths (major radius), or reduced minor radius. Both drag and indentation would increase, versus sphericals, if typical claimed contact region profiles are true. But friction/drag does not increase.

Sounds valid. In another forum there was a point thrown in the air that what if the groove's modulations come in such "density" on some records that the front/back cut would have an effect. The modulations in this case would be lifting the spherical stylus before it could establish it's full contact point in that said area. If you catch my drift? Sorry I can't explain it any clearer, as the original post is in different language posted by another person.

I think it might be possible, but I honestly don't know if modulations can be so dense for it to happen. I've seen some microscopic pictures of typical record grooves, but I've not seen modulations of such magnitude that could cause the mentioned effect in spherical stylus but not in elliptical. The whole issue is pretty difficult to perceive from photos, as I simply don't have the knowledge to know what to look for and how to look at it. Furthermore, the scale is rather deceiving!