Phonograph Stylus Wear Experiment

[USER]

The FR is unlikely to change with wear - what is more likely is that the proportion of distortion will increase... so same measurement sequence, but I think the key aspect will not be FR...

The problem is that most turntable message forums are as full of anecdotes about being able to hear sound signature changes (ostensibly FR) as much distortion. All the work we are doing is aimed at the public really. We are lucky we ourselves have the means to thoroughly investigate the medium for ourselves. I don't need this experiment, I can look at my measurements and take images of my styli, but I still fully supported the project. While there is always the opportunity to run the experiment again I see this as a wasted opportunity to show the public proper data, including if there are FR changes. More, and worse I think, this is much easier to misinterpret as it is poorly set up and gives a false sense of how a cartridge behaves to those new to measurements, which is most people. Just a bad representation of the work we are doing.

 

[ray_parkhurst]

The FR is unlikely to change with wear - what is more likely is that the proportion of distortion will increase... so same measurement sequence, but I think the key aspect will not be FR...

This seems a strange statement. Wear increases contact length, reducing the ability for the stylus to fit in shorter (higher frequency) grooves. It's the same phenomenon that makes a Shibata stylus have wider FR vs a 0.3mil elliptical, which is wider than a 0.7mil conical.

 

[USER]

It's the same phenomenon that makes a Shibata stylus have wider FR vs a 0.3mil elliptical, which is wider than a 0.7mil conical.

What do you mean by this? Higher than 20kHz? You can't hear anything above that. Conicals can't reach 20kHz?? I'm sorry but those are old wives tales.

 

[ray_parkhurst]

Yes, higher than 20kHz. Odd that you would not know Shibata was invented for CD-4.

 

[USER]

Yes, higher than 20kHz. Odd that you would not know Shibata was invented for CD-4.

Odd that you of all people would think that matters or that you'd be able to say anything conclusive about it without a rare test record. Clearly these examples extend past 20kHz.

 

[JP]

When geometry becomes an issue it’ll start to lose amplitude as the stylus isn’t able to fully trace the groove. Even with a fresh elliptical this can be seen when comparing inner and outer grooves well below 20kHz.

 

[USER]

When geometry becomes an issue it’ll start to lose amplitude as the stylus isn’t able to fully trace the groove. Even with a fresh elliptical this can be seen when comparing inner and outer grooves well below 20kHz.

Does you TRS-1007 have an inner groove sweep? If so I'd love to see an example. I was trying to play around with overhang to see if I could approximate some of the difference and got results like this.

 

[JP]

These are measurements with TRS-1005 outer vs. inner tracks.

 

[ray_parkhurst]

Odd that you of all people would think that matters or that you'd be able to say anything conclusive about it without a rare test record. Clearly these examples extend past 20kHz.

A larger minor radius has narrower FR. When new, even a 0.7mil conical can reasonably trace a 20kHz outer groove. But pretty quickly the contacts will wear, and the response will start to drop (and distortion increase) at higher frequencies. In the limit, the tip will wear to a wide chisel, and will just drag across the high frequency grooves. I hope you don't believe that a chisel point stylus of any type will still have flat FR.

 

[JP]

They are. The first one dropped (T0) in a post I made on July 14, Friday at 3:11 PM. See it at the bottom of the page. You have to expand the post to see it.

Not sure how I messed up that post, but somehow I embedded my response to @Digby within his inquiry. If ASR has a site moderator, perhaps they would be willing to clean that up.

Did they do multiply laybacks with a couple of test records as advised, or just the one? Or, did anyone ascertain the cause of that left channel glitch?

 

[USER]

A larger minor radius has narrower FR. When new, even a 0.7mil conical can reasonably trace a 20kHz outer groove. But pretty quickly the contacts will wear, and the response will start to drop (and distortion increase) at higher frequencies. In the limit, the tip will wear to a wide chisel, and will just drag across the high frequency grooves. I hope you don't believe that a chisel point stylus of any type will still have flat FR.

Just to be clear I wasn't saying that FR could not be impacted. I am open to it. In fact I wrote, "I see this as a wasted opportunity to show the public proper data, including if there are FR changes." Again, this is why I was hoping you guys were conducting your measurements properly. I just had issues with the way you framed your statement.

But you have seen this measurement of something quite close to a chisel point. This is already past the point of a cartridge anyone should use.

I have a NOS stylus coming in and I'll be able to measure it and compare it to this, so we will be better able to see the difference. But here, on an outer groove recording, FR doesn't seem too impacted. At the very least it is a "flat" result. And I am aware that this is an outer groove sweep and its limitations. But your CBS STR-100 is an outer groove record as well so your results will likely not be any more conclusive, especially as you guys made no effort to be able to distinguish stylus wear from test record wear.

 

[ray_parkhurst]

But you have seen this measurement of something quite close to a chisel point. This is already past the point of a cartridge anyone should use.
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I have a NOS stylus coming in and I'll be able to measure it and compare it to this, so we will be better able to see the difference. But here, on an outer groove recording, FR doesn't seem too impacted. At the very least it is a "flat" result. And I am aware that this is an outer groove sweep and its limitations. But your CBS STR-100 is an outer groove record as well so your results will likely not be any more conclusive, especially as you guys made no effort to be able to distinguish stylus wear from test record wear.

Will be good to see what a NOS stylus measures on the same cartridge. If it has +2dB response, then the -2dB here means a 4dB degradation. Plus, that stylus just appears worn, not chiseled quite yet. It may not even be hitting bottom. The contact flats still appear "oval" shaped.

 

[USER]

Will be good to see what a NOS stylus measures on the same cartridge. If it has +2dB response, then the -2dB here means a 4dB degradation.

Agreed.

This is one I wish I took a picture of. Seems crazy worn.

Edit: this is a conical.

 

[ray_parkhurst]

Yes, H2 is rising to a resonant peak of -3dB! I'm actually not sure how that is possible, the physical mechanism of having both elevated fundamental and H2. It is very interesting indeed.

 

[dlaloum]

What do you mean by this? Higher than 20kHz? You can't hear anything above that. Conicals can't reach 20kHz?? I'm sorry but those are old wives tales.

View attachment 300753
View attachment 300754

Shibata and fine line contact types were critical in enabling CD4 which needed the 40kHz carrier to be tracked - so yes they are fine enough horizontally (in terms of the contact patch) to properly track well beyond 20KHz.

What is far more difficult is the cantilever / effective moving mass...

lower mass = reduced distortion, better tracking, flatter frequency response

 

[dlaloum]

This seems a strange statement. Wear increases contact length, reducing the ability for the stylus to fit in shorter (higher frequency) grooves. It's the same phenomenon that makes a Shibata stylus have wider FR vs a 0.3mil elliptical, which is wider than a 0.7mil conical.

Yes - that means it won't PROPERLY track the high frequency... which means increased distortion - it doesn't mean a decrease in primary signal amplitude - the increase in distortion might in fact increase the signal amplitude ... I don't know.

But the assumption that the inability to track FR properly would result in a reduced amplitude at higher frequencies doesn't have much basis I think!

Many of the more basic cartridge with "fat" styli, have a droopy high end, but that can be calculated... based on their loading and inductance ... their recommended setup would guarantee a rolled off high end... thereby removing any nasty distortion from the frequencies that they can't track!
High Inductance + High Capacitance + a heavy cantilever with resonance between 8k and 10k .... they definitely have their own "voicing"!

 

[Icewater_7]

Yes - that means it won't PROPERLY track the high frequency... which means increased distortion - it doesn't mean a decrease in primary signal amplitude - the increase in distortion might in fact increase the signal amplitude ... I don't know.

But the assumption that the inability to track FR properly would result in a reduced amplitude at higher frequencies doesn't have much basis I think!

Many of the more basic cartridge with "fat" styli, have a droopy high end, but that can be calculated... based on their loading and inductance ... their recommended setup would guarantee a rolled off high end... thereby removing any nasty distortion from the frequencies that they can't track!
High Inductance + High Capacitance + a heavy cantilever with resonance between 8k and 10k .... they definitely have their own "voicing"!

Worthy of the “Audio Science” in the forum’s name. As new evidence is made known, existing theory may need too be revised.

 

[JP]

Nothing new here at all - these are well known and measured facts. If the stylus doesn't physically fit in to the "bottom" of the modulation there is less velocity, hence lower amplitude. Again: #209

 

[ray_parkhurst]

I've done the imaging of the DUT stylus at T24 (24hr), and as expected can see no wear.


One image I take, but rarely publish, is looking straight down at the tip. This is the same view that is used with the Shure method, but instead of lighting from the side, I use the 45-deg ringlight to illuminate what I call the "contact span", which is the distance across the tip at the lowest point of contact in the groove. I have added this view in projection with the front view.


I have also added a drawing of a typical record groove, with the RIAA max spec (0.25mil radius) for bottom radius. This will give you all an idea of how much space there is between the stylus tip and groove bottom, and as the stylus wears we can all observe the gradual but inevitable groove bottoming.


The stylus will be on its way to @BMRR today for second test point (T48) sequence.

 

[ray_parkhurst]

Yes - that means it won't PROPERLY track the high frequency... which means increased distortion - it doesn't mean a decrease in primary signal amplitude - the increase in distortion might in fact increase the signal amplitude ... I don't know.

But the assumption that the inability to track FR properly would result in a reduced amplitude at higher frequencies doesn't have much basis I think!

I think many folks can describe the possible mechanisms that would result in the (fundamental) response to decrease with wear. @JP did so above. But I am not sure of the explanation for the response to increase. Many folks seem to believe it could/will happen, so I'm wondering if anyone has a hypothesis? Perhaps we'll at least get some data from this experiment.

At T24 test point, @BMRR will record the STR100, as well as a new VMN95E stylus that we'll keep as a reference. He's also going to do the recordings with a second preamp. This data may help to shed light on the interesting FR seen in the T0 recording.

We're also contemplating eliminating the T48 test point in favor of going straight to T96.