Page 3 of 6

Posted: 04 Feb 2011 22:27
by Guest
desktop wrote:If everyone goes to the JICO website and clicks on their "SAS Information" link you will see that now JICO is claiming that their stylus will meet spec for 500 hours.
OK, I admit I'm a muppet, and can't find anything relating to specifics as to distortion versus stylus wear. Or even anything meaningul as to wear spec on Jico's site. I can't believe I'm reading the same site in this respect. So I presume I'm not.........!

Would someone please either point, or advise exactly what to search ?

Appols, I would like to read it, and am obviously being dumb.........!

Posted: 04 Feb 2011 23:51
by Snead

Posted: 05 Feb 2011 00:17
by Guest
Snead wrote:Bottom of the page...
Thanks, snead, appreciated. had found already found that, and it's scant more or less just stating a vague 500 hour anticipation. If one was skeptical, one might be cautious to accept at face value. Can't believe that reference is the extent of what was is meant by desktop's references.

What I was referring to was the Jico website info referred in desktop's second post, concerning substance as to wear and distortion.
desktop wrote:...........That being said, lists a 5% distortion vs wear level, where the original stylus was at the less than 3% level to start.................there is significant distortion due to styus wear after 600 hours on ANYTHING JICO has tested. They are very up-front about this on their website. They say that their SAS stylus ONLY begins to have this distortion vs wear/time-usage period after 500 hours......

My bolded emphasis.

This is exactly what I cant find. Obviously, it would be very interesting...........pointers ?

Posted: 06 Feb 2011 06:49
by desktop
My own opinions and interest in the JICO SAS listing is because I won't be trading for, or buying used styli with more than 200-300 hours on them any more unless I can look at the stylus with my soon to arrive Olympus 500x stereo microscope. I'll be using 2 - 30x eyepieces with 2 - 16x research objectives.

I too was surprised by JICOs willingness to back their SAS stylus for only 500 hours. This would seem to be low, reflecting poorly on the stylus, ... this is an honest portrayal of the real lifespan of the best styli. So through my retipper and a diamond stylus polisher & supplier, I asked why such a poor usage rating would be used by JICO if it discouraged buyers from paying (effectively) US$0.24+ per hour for the SAS stylus.

The 500 hour hour rating is aimed at markets for JICO like Germany, and I think in Japan, the 500 hour rating is viewed as a conservative estimate that the company is willing to back. My opinion now is that making conservative claims about a product is considered fair and honorable. It seems that JICO could say nothing, which would introduce uncertainty, which discourages sales. JICO sells only for export, and they could make "estimates" of stylus lifespan that would match the currently tossed about expectations, like 1000 hours, or 1500 hours, but it is more normal in Japan to make honest estimates of stylus lifespan based on JICOs research.

You should look at JICOs little story about how they build/make every single stylus they sell (short of polishing the diamond). In Japan JICO is highly respected (and many of the stylus crafts-people in Japan know them). But if a company making excellent styli of various types estimates the stylus life of the SAS stylus (they have designed to have the maximum lifespan) at 500 hours meeting the "new" spec (or the point where there is measurable degradation), I became curious and had someone ask questions for me. Seems this new lifespan rating is based on real testing, and not just guessing or hoping.

Posted: 06 Feb 2011 07:22
by dlaloum
So what is required to allow proper stylus inspection?

Based on the Shure SEK microscope thread I organised a 200x scope for myself.

I have a bunch of "suspect" styli - and I was surprised by how few of them reflected the "worn" pictures from the shure manual... in fact NONE of them...
(Mind you a Virgin ADC Shibata is literally a beautiful translucent Jewel quality Gem.... fabulous!)

Some showed wear - but not even close to the Shure "Worn" images.

So how does one tell how far along a stylus is?

What do you look for? And what magnification is required?

at 200x I find it very difficult to identify some of the stylus shapes... let alone seeing wear detail (which I am primarily seeing using the Shure reflection method) - perhaps a topic for another thread...

Posted: 07 Feb 2011 05:59
by Alec124c41
The one thing you do not want to see is the flat on the side forming a square angle with the leading edge of the diamond. This becomes a cutting bit.


Posted: 07 Feb 2011 15:26
by Guest
Yes, I really doubt that sharp leading edges form except in extreme. Rather, I prefer the notion of compound curved contact areas with lower curvature (due to wear) that blend into original curvature at extremities. Probably.

I remain thoroughly confused about what's reported on this thread. I re-read carefully to try to piece it together and this is what I summarise as what is posted.

(Please point out where I'm mistaken)

1. The only Jico public info cited is a single sentence in the link that snead kindly posted, referring to a scant statement that Jico anticipate 500 hours wear life for the SAS stylus, and that this is 3-4 times more than typical other stylii, according to Jico.

2. It is reported on this thread that Jico have a test which examines distortion versus hours use. Conditions of this test are not posted here, as to frequency, level, rpm, spindle radius. There is suggestion that the test is at 15kHz, except for sphericals where it is at 7kHz.

3. Test results for new stylii of all types are reportedly c 3% or less distortion. Failure threshold for this test is c 5% or more distortion.

4. On this test, sphericals reportedly transition from 3% to 5% in 133 hours use. Elipticals c 200 hours use. Jico SAS c 500 hours. VdH1 800-1000 hours use.

I find this whole lot impossible to reconcile !

Harmonic distortion correlates with stylus contact curvature in a well known, established way. For example, a 4um minor radius stylus at 15kHz, 33rpm, -10dB (ref 5.6cm/s@1kHz), 15cm spindle radius exhibits c 3% harmonic distortion. 6.5um minor radius produces 5% distortion.

So supposition might be that 500 hours of use causes stylus contact curvature to wear from 4um to 6.5um. That seems plausible. After 500 hours use the SAS stylus still has superior minor radius geometery to, say, a new 7um eliptical.

But similar models for sphericals and elipticals aren't plausible. For posted spherical figures @7kHz on this thread, transition from 3% distortion to 5% distortion means migration from 18um to 29um in 133 hours ! At 29um, the stylus would be seriously degraded. Obviously this does not happen.

For Elipticals, a migration from 7um to 12um in 200 hours also implausible, and would be readily observable with common microscopes. But it isn't.

So I reckon quite a bit here makes little sense, because I can readily construct numerical examples that just don't support the reports.

The devil must lie in the detail of Jico's test definitions. Without knowing that, I think we're just left with a single fairly scant sentence on a Jico website that, on the face of it, is contradicted by common experience and established analysis. I'm not convinced at all, and prefer to ignore it until proven. Frankly !

I'd be surprised if stylus wear rate was not at least a first order approximation to volume of diamond eroded per hour. Then higher curvature radius stlii might well wear (change curvature) faster than more bulky lower original radius types.

I should say that I fully accept the principle of measuring harmonic distortion as an indicator of stylus wear. I would love to see a standard method by which that could be repeated domestically. These days, sw spectrum/distortion analysers are common place, and it seems a likely very useful test to be able to do at home. Desktop referred to his own measurements which would also be great to see posted.

I'd love to be proved wrong, and/or for someone to come up with Jico (or any other) measurement standard for stylus wear. But it has to be test method first. Rather than conclusion/results first and work backwards, which seems to be where we are here !

Posted: 07 Feb 2011 16:21
by missan
Very interesting LD.
One thing is also how we should look at the minor radius. MLs are a little different in that aspect, even with a quite worn stylus the thickness is still 5µm, but radius could be infinite. How is this affecting the distortion?


Posted: 07 Feb 2011 21:52
by Bebé Tonto
missan wrote:Very interesting LD.
One thing is also how we should look at the minor radius. MLs are a little different in that aspect, even with a quite worn stylus the thickness is still 5µm, but radius could be infinite. How is this affecting the distortion?

ML's still have a minor radius. The sides of the ML tip are rounded off, not flat.

Posted: 07 Feb 2011 23:58
by dlaloum
Yes - but I see Missan's point.... The flattened (worn) surface has effectively infinite radius, then there would be an intersection between it and the original curve (a Line? Curve?.... is it sudden... an edge.... or gradual... a tertiary radius?)

And the question is then what would the distortion impact be of this shape?

Does the distortion / radius model encompass this shape - or is a modified version thereof required?

As LD said - there is very little detailed data with which to analyse the published result.

Posted: 08 Feb 2011 00:50
by Guest
dlaloum wrote:And the question is then what would the distortion impact be of this shape?
I don't think normal wear at the level being discussed results in a true flat. Rather a small region with less curvature that progressively increases toward the original curvature near the boundary between worn and unworn surfaces.

I believe this arises because slightly different locations on the stylus touch the groove, depending on modulation. That is what gives rise to harmonic distortion in the first place !

Distortion equations I'm aware of are for true arcs. Although i'm suggesting the wear curve is not a true arc, it's probably OK to approximate as such when discussing smallish, round figure distortion numbers, like '3%' or '5%'.

As to missan's ML point, I think much depends on the width of the contact region as a fraction of the arc section that is the 'line'. I understand this contact region is very small in 'width', and so ML wear perhaps results in a vertically elongated 'spot' which has reduced curvature. But since it is this spot that is in contact, the wear spot's curvature alone defines distortion. In principle !

As wear progresses, contact region curvature progressively decreases. And in extreme is near flat. Contact region area also progressively increases, ie the spot gets bigger. In extreme, a worn stylus has two large flats with bevelled edges.

As I see it ! Pictures are worth 1000's of words in such things.

Posted: 08 Feb 2011 04:15
by Alec124c41
In the extreme, sharp leading edges can form. Then your record turns gray before your unbelieving eyes, behind the stylus.
I had this happen with a V-15-III 40 years ago, when all anybody cared about was that the music kept coming... :spaceman:
I have absolutely no idea how many hours were on that stylus.


Posted: 08 Feb 2011 04:24
by dlaloum
Is this the stylus you reserve for playing "white xmas" albums?


Posted: 08 Feb 2011 04:43
by Alec124c41
Stylus replaced and dumped in the early '70s. Then I replaced the V-15 with a $25 Grado, which I thought an improvement. I still have the V15-III with the same stylus, and have several Grados, as well as quite a few other cartridges... :wink:


Posted: 08 Feb 2011 22:40
by Guest
Here's a diagram (borrowed form another thread) that helps to visualise how the contact point on the stylus moves significantly around the surface of the stylus when tracking a modulated groove.


It's easy to see that the contact points between the stylus and groove at B are significantly further round the stylus than at A. And C is somewhere in between. And, due to pinch effect, there's a different vertical location too. Contact, and so wear, is at a continuously varying location on the stylus. Wear location should follow a statistical distribution pattern, based on time spent at any given groove angle.

This is exaggerated in the diagram, as to angles typically involved. Nevertheless, it nicely illustates the principle of how contact points continuously vary with modulation, at least to some extent. That's why initial wear seems unlikely to be in a single spot location on the stylus, but rather follow the average modulation angle distribution pattern, and therefore be in a curved region pattern rather than flat spot. Perhaps a real average modulation angle is +/- 5 degrees, making a 10 degree arc wear pattern ??