Stylus Evaluation Imaging

the thin end of the wedge
chiz
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Re: Stylus Evaluation Imaging

Post by chiz » 06 Jun 2019 20:43

Interesting stuff Ray.

Can you be sure that all your records conform to RIAA standards?

If you look at the “Comparative Table of Standards” here it appears the maximum bottom radius can vary between 4 and 8 microns:

http://www7a.biglobe.ne.jp/~yosh/standards_table.htm

If my calculations are correct then a minimum contact width of about 0.45 mil (8√2 microns) should be safe for records conforming to any of these standards.

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Re: Stylus Evaluation Imaging

Post by ray_parkhurst » 06 Jun 2019 21:03

chiz wrote:
06 Jun 2019 20:43
Interesting stuff Ray.

Can you be sure that all your records conform to RIAA standards?

If you look at the “Comparative Table of Standards” here it appears the maximum bottom radius can vary between 4 and 8 microns:

http://www7a.biglobe.ne.jp/~yosh/standards_table.htm

If my calculations are correct then a minimum contact width of about 0.45 mil (8√2 microns) should be safe for records conforming to any of these standards.
Thanks for the standards table. I did not realize there would be such a discrepancy. Even if only looking at RIAA, the spec is the maximum, so a measurement is needed. This is why I proposed doing a cross-section, though I am not sure how accurate a measurement can be made of a cross-sectioned piece of vinyl. I have not tried that yet.

I'll need to do some imaging of my styli to see the range of contact spreads. I really have no idea what I will find.

chiz
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Re: Stylus Evaluation Imaging

Post by chiz » 06 Jun 2019 23:19

ray_parkhurst wrote:
06 Jun 2019 21:03
This is why I proposed doing a cross-section, though I am not sure how accurate a measurement can be made of a cross-sectioned piece of vinyl. I have not tried that yet.
Apologies, I misread that part.
Looking forward to your findings.

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Re: Stylus Evaluation Imaging

Post by ray_parkhurst » 07 Jun 2019 00:35

I measured the minimum contact span of a bunch of styli. These have all seen significant wear, though not all by me so I don't really know how many hours are on each. I have estimated play hours for each based on the contact flats and then did the span measurement. Here are the results, in estimated hours, contact span in mils:

Pickering 2DTL: 250, 0.59
Shure LTP-2: 500, 0.55
Empire LTD290: 1000, 0.27
AT733: 250, 0.60
Technics P33S: 250, 0.56
Technics P510S: 250, 0.58
Shure V15LT: 500, 0.40
Shure M94LT: 500, 0.66
Sony ND145G: 500, 0.51
Shure DT35P: 500, 0.58
Shure HE150: 500, 0.68
AT231LP: 250, 0.23

These run the gamut from spherical, elliptical, hyperbolic, to line contact, so it's hard to make any conclusions about the contact spans vs estimated wear. The AT231LP is an odd one. It does not appear to have much wear, but the tip is already so worn that it is essentially dragging bottom. The Shure V15LT is the only one of the group that is close to the limits being discussed, with all others well on one side or the other.

Comments on which ones make the most / least sense to evaluate are appreciated.

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Re: Stylus Evaluation Imaging

Post by ray_parkhurst » 07 Jun 2019 18:58

chiz wrote:
06 Jun 2019 23:19
ray_parkhurst wrote:
06 Jun 2019 21:03
This is why I proposed doing a cross-section, though I am not sure how accurate a measurement can be made of a cross-sectioned piece of vinyl. I have not tried that yet.
Apologies, I misread that part.
Looking forward to your findings.
No worries. Actually, I don't think a cross-section is the best way to do this. First, I don't really trust the results since I think vinyl will smear a bit. More sophisticated techniques can be used, but I'd be doing this at home. Second, it can only be done after the fact, in a destructive manner, so might waste a lot of time (and records). A non-contact / non-destructive method would be better...

I took a damaged record (unrepairable skip), and using the same ringlight imaging technique I've been using for stylus imaging I was able to highlight the groove bottoms with bright-line reflections. This particular record was MHS 654, Bach Trio Sonatas, pressed by Columbia Special Products. I don't know the date.

Below is the overall view of the image, followed by a crop showing the groove bottom. This technique is giving me a very high contrast line pair delineating the bottom of the groove, where the 45-deg sidewall meets the radiused bottom. The outer edges of the line pair is the point where the radius begins. By measurement, this width is 0.26mil, so the radius is 0.18mil, well inside the 0.25mil RIAA spec.

I think this technique will allow me to quickly assess my potential test records to determine the range of bottom radii, and the minimum width my styli could wear to before causing interference with the groove bottom.

Overall view, 20x magnification, ringlight illumination:
IMG_0001A.JPG
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100% crop view of the above:
IMG_0001B.JPG
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I think the 3 cartridges/styli that will be of interest with this record are the Empire LTD290 (0.27mil), the Shure V15LT (0.40mil), and the AT231LP (0.23mil).

I'll be looking through some more records to see if I can find one with a larger bottom radius. I'll look especially at some european pressings since they have potential for larger radii per the comparison table.

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Re: Stylus Evaluation Imaging

Post by ray_parkhurst » 08 Jun 2019 05:31

OK...first impressions:

I started with the cartridge I currently have in rotation...the Empire 480LT. It is not yet fully broken-in, and is still quite edgy. It served as a decent "cleaner" for the grooves of the Bach Trios, but as yet has not become a reference.

Second was the V15LT. It let me know immediately why it is so well regarded. Quiet sections were dead-silent, and I perceived no significant distortion. This is a true reference cartridge.

Then I installed the LTD290, the one I've been imaging most recently. It is very worn, and has a pretty narrow bottom contact span. But on actual grooves it sounded glorious! I can see why whoever owned it before me wore it to the bottom of the grooves. Image specificity was at least as good as the V15LT, and distortion was nearly as good. It was much more subject to groove noise, and then it hit me...between tracks it was very noisy. I could imagine that the tip was hitting bottom of the groove, and that's what it sounded like! It displayed much more noise between tracks than did either the 480LT or the V15LT.

Next was the AT231LP. I expected to hear even more groove noise and perhaps more distortion from this one given its small minimum contact spacing, but it surprised me with the best sound of the group! No discernible distortion, extremely quiet between tracks, and superb imaging. Really a surprising showing.

So it appears my hypothesis of minimum contact spacing as the primary criteria for determining terminal stylus wear is not correct. My AT231LP has smaller minimum spacing than the LTD290, both of which are smaller than the V15LT. Only the LTD290 subjectively shows its age, and not on distortion but only on quiet groove noise. The short contact lengths of the V15LT and AT231LP must be more important than narrow contact span in determining distortion and noise versus the much longer contact lengths of the LTD290.

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Re: Stylus Evaluation Imaging

Post by ray_parkhurst » 13 Jun 2019 23:51

I received the Ortofon X5-MCP today. It has a few problems unfortunately. The cantilever is significantly skewed, and it appears to be bent. It was also described as having very little use, but it has seen many hours of play. The contacts are worn pretty flat, and although the stylus design is such that the contact length (record play direction) don't grow quickly, they do merge at the tip like any other stylus. the contacts have worn to only 0.3mil span, so in theory are quite close to dragging the groove bottom. Overall it looks like I will need to send this rare beast back, as I paid way too much for it to be in this condition.

I did take time to image the stylus with a standard macro technique, similar to my avatar, as well as using my ringlight technique to show the contact patches. Ortofon lists this stylus as a VDH2, and I have no other reference, so I assume this is correct. It looks like what I'd expect from VDH but I don't know difference between VDH and VDH2. Perhaps someone can comment?

I was disappointed that the cantilever is just a simple pinched aluminum tube. Not even tapered. Seems odd to put a VDH2 stylus on such a cheap cantilever in a MC cartridge.

One very interesting thing about this stylus is that the sides are at a higher angle (nearer to 45-deg) than any other stylus I have imaged. This makes the contact appear to be extremely long in the orthogonal dimension, while extremely short in play dimension. The wear patches are of course at exactly 45-deg. I expect that if I used a more vertical lighting system the worn patches would show more contrast vs the unworn sides of the stylus. This is the first cartridge that has required a higher contrast lighting method to discern worn from unworn contacts. I'd expect this stylus to be extremely sensitive to setup, though on a P-mount system it should be much simpler as long as the stylus is not at all skewed.

Here's the overall pic:
Ortofon X5-MCP0B.JPG
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And here are the two worn contacts:
IMG_0018B.JPG
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IMG_0019B.JPG
(64.05 KiB) Downloaded 96 times

billshurv
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Re: Stylus Evaluation Imaging

Post by billshurv » 14 Jun 2019 12:43

Hi Ray,

Very interesting on the groove floor imaging.

Information on the vdH type 2 is here http://www.syclotron.com/a_van_den_hul_ ... c_1990.pdf

Ortofon have never used fancy stylii for their cheaper models and not convinced they really believe in them. A thin wall Al tube is light and stiff.

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Re: Stylus Evaluation Imaging

Post by ray_parkhurst » 14 Jun 2019 15:27

billshurv wrote:
14 Jun 2019 12:43
Hi Ray,

Very interesting on the groove floor imaging.

Information on the vdH type 2 is here http://www.syclotron.com/a_van_den_hul_ ... c_1990.pdf

Ortofon have never used fancy stylii for their cheaper models and not convinced they really believe in them. A thin wall Al tube is light and stiff.
Thanks. So type 1 has a very sharp edge, with only 0.1mil radius, while type 2 is almost 0.3mil radius. I imagine type 1's wear pretty fast.

This X5-MC sounds pretty good.

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Re: Stylus Evaluation Imaging

Post by billshurv » 14 Jun 2019 16:51

The Gyger FGS is similar to the type one and has very slow wear rates. But not looked for life expectancy of VdH.

chiz
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Re: Stylus Evaluation Imaging

Post by chiz » 14 Jun 2019 17:16

ray_parkhurst wrote:
14 Jun 2019 15:27
I imagine type 1's wear pretty fast.
He mentions 3500 hours here:
https://web.archive.org/web/20150607085 ... ge-reviews
and here:
http://www.goodsoundclub.com/pdf/Phono_FAQ.pdf

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Re: Stylus Evaluation Imaging

Post by Delta667 » 14 Jun 2019 17:42

About the stylus Van den Hul 1 Special ...
With all due respect to the name of the master, I want to note that the duration of some of his styli is "0". ((
This means that the new stylus immediately touches the bottom of the groove and its sound is terrible. I met him at Thorens MCH 63. How did this happen with such a respected cartridge?
I very quickly found a solution. I cut off the tip of the stylus, thereby turning it into an extended ellipse, which are often found on Aurex cartridges.
The situation was corrected, the owner of the cartridge was very pleased.
I carried out a similar operation twice, but in the second case the cartridge was in operation for some time. And very quickly began to scoop all the dirt from the bottom of the groove.

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Re: Stylus Evaluation Imaging

Post by billshurv » 14 Jun 2019 22:25

I can believe that. I suspect that for many cartridges they bottom out before they wear out with advanced stylii. It would be interesting to get a well used microridge to Ray to see how that actually looks after 1000 hours.

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Re: Stylus Evaluation Imaging

Post by poutrew » 14 Jun 2019 23:13

It is too bad that they don't make a stylus that you can turn 90 degrees when it wears out. That way you can re-use what used to be the front / back of the diamond and get double duty out of it... :)

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Re: Stylus Evaluation Imaging

Post by ray_parkhurst » 15 Jun 2019 00:23

billshurv wrote:
14 Jun 2019 22:25
I can believe that. I suspect that for many cartridges they bottom out before they wear out with advanced stylii. It would be interesting to get a well used microridge to Ray to see how that actually looks after 1000 hours.
I've been hoping for someone to send one to me for imaging. Someone must have one with lots of hours they have replaced with new.

From the styli I have imaged, my conclusion so far is that short minor radii appear to wear more slowly, since their contact lengths in record play direction grow more slowly, but ultimately they still wear to the point of hitting the groove bottom radius. My hypothesis is that the short contact length actually causes faster wear. I'd like to have the data to show if this is correct.

I would think that someone would be able to take a well-worn line-contact/MR type and polish the tip back a few um. This would increase the contact span at bottom of the groove, keeping it from bottoming-out. As long as there is still some of the MR left, this should give more life to the tip. I might experiment on a well-worn elliptical or line contact stylus of my own and report the findings, but again if someone has a well-worn MR it would be nice to see if it can be resurrected.

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