Macro Photos of Record Grooves

[Soandso]

Glad this is already well-known, as it makes it much easier to move forward. I had posited mistracking as the cause but it was only conjecture. Seems that others had the same idea decades ago

This photo from comment #34 (shown below) is quite problematic for establishing that your own photographed anomalies are a result of mistracking. What I see in the above referenced photo is continuous fletches of anomalous light along the entire distance of the groove segment. Whereas in your own photos (an example shown underneath) only see sporadic fletches of anomalous light separated by clear intervals of the groove segment without anomalous light.

They are not identical markings, although share some similarities, thus definitively ascribing mistracking as the cause of your cases seems premature. I think it is logical to suppose that a song on your photographed records' side(s) were most commonly played in their entirety so that the song's grooves endured the same tracking throughout. Yet your anomolies in a song's grooves show up sporadically instead of consistently.

 

[ray_parkhurst]

I think that's because the peaks are sporadic, rather than consistent as is the case with the test tone groove.

I'm not 100% sure that mistracking is the cause, but I am 100% sure these anomalies were not created in the manufacturing process.

 

[Thomas_A]

The damage as seen in the references paper looks more like a stylus grind (at the right position of the groove wall). I cannot really see such traces along the groove in your photos, @ray_parkhurst. It is more like a rough surface at the lighter areas.

 

[Zapper]

This photo from comment #34 (shown below) is quite problematic for establishing that your own photographed anomalies are a result of mistracking. What I see in the above referenced photo is continuous fletches of anomalous light along the entire distance of the groove segment. Whereas in your own photos (an example shown underneath) only see sporadic fletches of anomalous light separated by clear intervals of the groove segment without anomalous light.

They are not identical markings, although share some similarities, thus definitively ascribing mistracking as the cause of your cases seems premature. I think it is logical to suppose that a song on your photographed records' side(s) were most commonly played in their entirety so that the song's grooves endured the same tracking throughout. Yet your anomolies in a song's grooves show up sporadically instead of consistently.
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View attachment 290666

>> Yet your anomolies in a song's grooves show up sporadically instead of consistently.
I would expect that, given that real music is highly non-uniform compared to a test record.

The wear appears to be the mistracking that occurs when the mass of the stylus assembly no longer accurately follows the high frequency modulations of the groove, and starts to lag behind. This will occur more readily with inexpensive, high mass styli. (And, ironically, with some very expensive but high mass moving coil cartridges.) The lagging response of the stylus & cantilever causes the wear point to move from the point of greatest deflection (where the acceleration should be the highest) towards the point of greatest slope (where the acceleration should be zero) due the the compression of the vinyl that is required to accelerate the heavy mass of the stylus. The lagging response creates a phase shift that accompanies a roll-off of the high frequency response - to the extent that the cantilever system is rigid. However, the cantilever may have resonant modes of nearby frequencies which can change the dynamics of the system in complex ways.

This is why records that have been played many times on a cheap record player usually sounds terrible when played on a high quality turntable with a good cartridge. The high frequency signals are degraded, and are accompanied by a lot of staticy noise from the irregular wear patterns in the groove. Such a worn record may not sound noticeably worse than it usually sounds when played on the cheap record player, because the cartridge/electronics/speakers are not reproducing the high frequencies anyway. But the high quality system clearly resolves all the groove damage, and it sounds very bad.

 

[ray_parkhurst]

The big question with the groove photos I show is why the damage extends (on some anomalies) to the top and bottom of the groove. The only explanation that sounds feasible to me is the stylus used must have been very worn, chisel-tipped and major radius flat going from top to bottom of the groove. A stylus like the one I showed in first pic of the Stylus Evaluation Imaging (VE) thread would fit the bill here. I can see something like that causing this damage, and knowing what record players this album was played on I would not doubt that's what the stylus looked like.

 

[Thomas_A]

The big question with the groove photos I show is why the damage extends (on some anomalies) to the top and bottom of the groove. The only explanation that sounds feasible to me is the stylus used must have been very worn, chisel-tipped and major radius flat going from top to bottom of the groove. A stylus like the one I showed in first pic of the Stylus Evaluation Imaging (VE) thread would fit the bill here. I can see something like that causing this damage, and knowing what record players this album was played on I would not doubt that's what the stylus looked like.

Perhaps if it was chipped. A worn stylus should not be polished flat with sharp edges by music grooves (but getting larger radius), unless it has been polished in a run-out groove.

 

[ray_parkhurst]

Perhaps if it was chipped. A worn stylus should not be polished flat with sharp edges by music grooves (but getting larger radius), unless it has been polished in a run-out groove.

Based on the many styli I've photographed, I can say this statement is incorrect. Every one which has significant wear has flat contact patches, including ones from folks who don't just play runout grooves.

 

[Zapper]

The big question with the groove photos I show is why the damage extends (on some anomalies) to the top and bottom of the groove. The only explanation that sounds feasible to me is the stylus used must have been very worn, chisel-tipped and major radius flat going from top to bottom of the groove. A stylus like the one I showed in first pic of the Stylus Evaluation Imaging (VE) thread would fit the bill here. I can see something like that causing this damage, and knowing what record players this album was played on I would not doubt that's what the stylus looked like.

The vinyl is not a rigid surface. When the stylus is not following the groove (because it is too massive to respond to high frquency modulation) the force of the stylus on the groove wall is very high, causing deformation of the vinyl. The soft vinyl bends under the force of hard diamond. This increases the area of contact patch between the stylus and vinyl in those regions where the force is greatest. So you get wear that extends higher and lower in the groove than you would expect given the shape of the stylus.

 

[ray_parkhurst]

Yes, I'm sure that is true, but this shows a surprising amount of deformation if indeed that is the mechanism. You can see small damage sites where the damage is centered in the groove wall, and larger ones that extend much farther to top and bottom. Deformation is a good hypothesis for this, and allows a normal stylus which is not hitting bottom nor top. I'll run with it.

 

[JP]

This photo from comment #34 (shown below) is quite problematic for establishing that your own photographed anomalies are a result of mistracking. What I see in the above referenced photo is continuous fletches of anomalous light along the entire distance of the groove segment.

Those images are SEM.

 

[ray_parkhurst]

Those images are SEM.

Are you sure? The first looks like low resolution optical to me. The second is for sure optical, as I took it with my system.

 

[JP]

Yes, I wasn't talking about yours. The article is titled "The Scanning Electron Microscope - A New Tool in Disc-Recording Research" I miss-attributed it to Shure, though - it was RCA.

 

[Thomas_A]

Based on the many styli I've photographed, I can say this statement is incorrect. Every one which has significant wear has flat contact patches, including ones from folks who don't just play runout grooves.

I’ve seen your excellent pictures but it is difficiult to say IMO if these are completely flat with cutting sharp edges. Polishing in a modulated groove must include different angles and variying contact patch area as opposed to a stationary unmodulated groove. I can’t see it happening unless someone left it running in the runout groove.

 

[ray_parkhurst]

I’ve seen your excellent pictures but it is difficiult to say IMO if these are completely flat with cutting sharp edges. Polishing in a modulated groove must include different angles and variying contact patch area as opposed to a stationary unmodulated groove. I can’t see it happening unless someone left it running in the runout groove.

For sure they are not completely flat, and the edges are not perfectly sharp. Indeed early on in my imaging I had posited that a stylus might be "reconditioned" by running it in a groove with high modulation such that it would "round off" the corners of the contact patches and improve the contact tracing, thus lowering distortion. I still do believe that it might be possible with a certain constant frequency and high modulation, but that frequency would be different for different stylus types with different minor radii.

Which brings us to the core of the argument. For a stylus tip to trace a groove without distortion, it must fit in the groove and contact it without interruption from peak to trough. This requires that the radius be quite small, perhaps a max ~0.25mil/6um for 20kHz. For lower frequencies, the groove "looks" much flatter. At 2kHz the groove has a 10x aspect ratio vs the radius, and at 200Hz a 100x aspect ratio, ie essentially flat. RIAA pre-emphasis increases the amplitude vs frequency, but the PSD of most music is still skewed toward LF, and there is of course quite a bit of amplitude variation, as well as a large percentage of the record being relatively quiet. End result is that you don't really need runout grooves to wear the tip flat, most any record will do fine. Unless of course you only listen to HF test tones...

 

[JP]

For a stylus tip to trace a groove without distortion, it must fit in the groove and contact it without interruption from peak to trough. This requires that the radius be quite small, perhaps a max ~0.25mil/6um for 20kHz.

Worth specifying that this is also dependent on amplitude and radius.

 

[ray_parkhurst]

Worth specifying that this is also dependent on amplitude and radius.

On inner vs outer grooves as well. I'm actually not sure what the max radius would be to trace a fully modulated 20kHz inner groove, but it's probably moot since I don't think that groove exists anywhere.

 

[Thomas_A]

For sure they are not completely flat, and the edges are not perfectly sharp. Indeed early on in my imaging I had posited that a stylus might be "reconditioned" by running it in a groove with high modulation such that it would "round off" the corners of the contact patches and improve the contact tracing, thus lowering distortion. I still do believe that it might be possible with a certain constant frequency and high modulation, but that frequency would be different for different stylus types with different minor radii.

Which brings us to the core of the argument. For a stylus tip to trace a groove without distortion, it must fit in the groove and contact it without interruption from peak to trough. This requires that the radius be quite small, perhaps a max ~0.25mil/6um for 20kHz. For lower frequencies, the groove "looks" much flatter. At 2kHz the groove has a 10x aspect ratio vs the radius, and at 200Hz a 100x aspect ratio, ie essentially flat. RIAA pre-emphasis increases the amplitude vs frequency, but the PSD of most music is still skewed toward LF, and there is of course quite a bit of amplitude variation, as well as a large percentage of the record being relatively quiet. End result is that you don't really need runout grooves to wear the tip flat, most any record will do fine. Unless of course you only listen to HF test tones...

Yes agreed. I would think as seen from the previous experiment with one record that the amplitude of 10-20 kHz gets worn on the record while it takes a while before that is seen in stylus wear. However that wear would be most evident on high HF levels at the end of the record when stylus no longer fit in the tightest modulations. The other stylus wear issue I can think of and have measured is an increases background noise. I think that relates to higher friction or the same suboptmal HF tracking as above causing stylus to loose contact in very short time spans and therefore casuing HF broad noise (read ssshhh instead of sssss in sibilants). The latter can be even if the stylus fit but the acceleration is just too large to keep the stlylus in groove contact, ie classic mistracking. Both may lead to groove damage which might be what is seen in the coarse surface parts.

 

[JP]

On inner vs outer grooves as well. I'm actually not sure what the max radius would be to trace a fully modulated 20kHz inner groove, but it's probably moot since I don't think that groove exists anywhere.

Radius = groove radius in my post. What is fully modulated?

 

[ray_parkhurst]

I haven't done the calculation to determine what the radius of a fully modulated 20kHz inner groove would be. I'd assume that the stylus minor radius would need to match, but again it is moot since it would be untraceable.

 

[JP]

Sure, but I'm not asking what the radius would be, I'm asking what fully modulated is?