conical versus ellipticals

[Thomas_A]

Also ice skating has been problematic to solve. So I am not very suprised that there are many types of explanations out there.

[desktop]

Hi all, I'm not sure that playing a vinyl record once is a good test of any theory about how spherical, elliptical and line contact styli affect the groove walls on a disc. The best case seems to be a lubricated stylus that is highly polished and is of a high quality hyper-elliptical shape (or better) with sufficient tracking force to hold the stylus in contact with both walls of the groove all the time, and equally. Once we get to a lubricated and highly polished spherical stylus (like a Denon 103), playing a new disc with sufficient tracking force and correct anti-skating, I think you'll find vinyl wear in the grooves goes way up (at least according to the NAB).

The reason for this seems to be that if an album is popular, and even if it is cleaned carefully every time between plays once per day, and even if the stylus is cleaned and lubed every time it is used for an album side, the "track" in the bottom of the grove caused by a spherical stylus can be seen clearly by about the 60th play. The disc of Iron Butterfly's "In a gada da vida" (?SP?) is played full length each time (it covers one side of the disc). We have a station here in Kansas City that often plays the Tangerine Dream album sides straight through, as well as M Olfield's Tubular Bells for their "New Age" show. Many many classical discs were played tris way. It is clear even with a standard microscope at 300x that there is a rippling effect of wear on the contact areas of these records.

As an AES member this problem was brought to our group 10-12 years years back. A radio station playing classical and other full-length-play albums was finding many albums unavailable on CD. These albums were also difficult to source on vinyl. The cost of maintaining a music library at a fastidious station was substantial. We had the station use calibrated Stereohedron Stanton cartridges whenever possible (681 S). The records in question seemed to last 3x to 4x times as long, before noise became objectionable due to the contact "track" that formed after as few as 60-70 plays using the Denon 103R catridge (also calibrated for Radio Station use). We (AES members) went in and chose the best of the remaining best turntables and arms. We set them up properly, and installed the cartridges ourselves. The problem was eventually solved (the high cost of replacement vinyl) by burning all these discs to CD once in a while and automating the shows.

But the problem is still there. The lubricants in the vinyl itself may "burn off" and then under-surface lubricants may re-mix with the fast melting vinyl (I prefer the view that the vinyl only softens, not fully melts). But eventually this built-in lubricant inside the vinyl formulation is gone. This is most obvious in discs made of 1/2 crushed vinyl and 1/2 new vinyl. It is obvious when viewing the grooves after a while, that the crushed vinyl particles are "showing thru" like cobblestones will eventually show thru when a thin layer of blacktop is put over them to produce a smoother ride in a car.

So play a new disc once and check for groove wear. Since my college minor was statistics I then suggest this test sequence; play it 10 times and check for wear. Use three discs; one with a spherical stylus, one with an elliptical stylus and one with a line contact stylus. Then check after 30 plays, then 60, then 100, then 150, then 225 plays and so on with a maximum of 1721 plays (if there is no visible creation of a new contact wear track in the groove bottom after 1721 plays, there is no need for further tests.), and compare how fast the track/noise wear occurs at the bottom of the groove. The spherical will always be worst, but the elliptical will only be useful for about 25% longer, while the line contact stylus may be useful 100% longer than the elliptical. Other styli like shibata and hyper-elliptical etc. will be between elliptical and line contact styli, while the best 6 designs (Stereohedron, Microridge, MicroTracer, Replicant, VdH1, and Gyger 1) will go the longest without obviously making a track due to contact in the groove. I'm trusting that there are no huge improvements in vinyl in 1992 since CBS Labs went thru this testing regimen.

[Ldg]

Thanks for interesting insight, desktop. One thing I don't get from your post is why should vinyl wear in the grooves go way up with a lubricated and highly polished spherical stylus (like a Denon 103), playing a new disc with sufficient tracking force and correct anti-skating. Can you explain more please ?

Some months ago I did a DSC analysis of a piece from a Decca record.
I found the Glass Transition to be just below 70degC.
As vinyl is a amorphous thermoplastic I believe if this temp is reached there will be a plastic deformation of the vinyl that is permanent.

Following this thread I am totally convinced that the transition in the vinyl is taking place in a very thin layer and is of no importance regarding deformation. If there should be any resamblance with ice skating I believe that the temp above the record´s surface must be closer to Tg temp. The surface pressure when playing will not normally make the vinyl too stressed, it´s still well within the elastic area.
missan
Edit: better spelling

Calculation yields 15nm as typical groove skin thickness at which glassing temperature is exceeded at 20 deg C ambient. This is 150 Angstroms, about the size of vinyl polymer molecules, though that can vary. About the size of a small virus ! Accumulated groove wear perhaps involves progressive changes and erosion for these first few molecular layers, through glassing, leaching of plasticisers, fracturing of polymers, and mechanical surface interaction with the stylus.......?

[missan]

Accumulated groove wear perhaps involves progressive changes and erosion for these first few molecular layers, through glassing, leaching of plasticisers, fracturing of polymers, and mechanical surface interaction with the stylus.......?

This would seem very likely. The mtrl in the part of the groove that has repetedly been exposed to to high stress, will with time be something else than the original vinyl. Some of the Cl and H will probobly loose their bondings and form acid, plastizisers will loose their roll and the surface with the highest stress will become brittle.
missan

[desktop]

To reply to ld

I am not suggesting that record wear goes up with the type of stylus mentioned (highly polished spherical lubricated like the Denon 103R). On the contrary we picked this example because of all the spherical stylus cartridges in the world, the Denon 103R provided documentation that it was the spherical stylus with the lowest amount of groove wear at the contact point, compared to any other spherical stylus cartridge in the world.

So if we started with the best possible spherical stylus cartridge, and compared it to a high quality elliptical, and a high quality line contact stylus (and also a superior grade stylus design), we felt we could not be faulted because we chose a low quality spherical stylus cartridge as our test starting point.

I appreciate missan's comments and tests as well. The onset of damage to a groove, when small ripples are forming at the point of stylus contact at the bottom of the groove, may not be obvious when scanned. But those ripples represent a very hard, and very different kind of vinyl compared to the rest of the groove, and not only will this vinyl chip off quickly in future, sticking to styli, they cause chatter and what seems to be an odd form of mistracking. After repeated plays after the ripples first appear, they are chipped/sheared off, and then the cartridge seems to track properly again, but now the disc is noisy, and the tracks at the bottom of the grooves are plainly visible. Vinyl cannot soften without some damage, so this is why replicant styli which have the lowest tracking weight per square surface area of the groove make discs last the longest, noise-free (or as well as possible).

By the way, these ripple-chips that end up sticking to hot stylus tips, then pick up grit and they are at that point like huge gouging plows in the groove, with added tip mass and the terrible problem that this sharp grit is being held in the groove right at the point where the vinyl has softened the most. This is why it is so difficult to use vinyl. The vinyl has to be treated the best it can, and the stylus tip as well.

[Ldg]

Thanks desktop, much appreciated and interesting. Understood. A few further questions following on...... any notion of how deep the ripples appear when first observable or during progressive development ?.......How wide is the groove wear track, roughly? When fragments chip off, any notion of size ?

[Ldg]

Just realised that diamond is almost the only material with sufficient thermal conductivity to get heat away from the contact area with minimal vinyl glassing, and so minimises groove wear. Despite being hard, tricky to polish and expensive, starting to understand why stylii are made from diamond now.........not just for show then !

[Ldg]

Here's part 4 of calcs on temperature of stylus and vinyl. It's been a while because I was surprised by this result and thought would try and find an error, but can't, so thought would post anyway and get some help ! The other parts are on this thread.

Conclusion from part 1 was that typical heat flow rate at stylus/vinyl contact is of the order of 2mW. Conclusion of part 2 was that whatever the temperaure of the contact region, some 1uW is conducted into the vinyl, and this is effective heating power. Conclusion from part three was that average temperature rise T of vinyl groove wall skin to thickness of 0.1um was c 10 deg K (celsius).

This is part 4 and looks at temperature rise of stylus near the contact region.

Unlike vinyl situation, same area of stylus continually generates and conducts heat from contact region. Assumed area is c 25um^2, in a solid arc of radius c 3um. Assumed conducted heat flow = 2mW.

Method is to examine heat conduction from this area, in a spherical pattern radiating from the contact area, determine thermal gradient and from that specific temperature of the contact region. Assumption is that there is no thermal gradient by the time the stylus/cantilever boundary is reached, i.e all 2mW can be conducted by the cantilever with negligible thermal gradient and dissipated by the cantilever or cartridge.

Won't post detail math unless anyone asks, not easy in text. Assumed a spherical stylus in the end, and certain boundary conditions such as the shank is much larger than the spherical radius etc.

Result is that stylus contact region within 100nm of contact region is less than 5 degC above ambient. Seems that diamond is a truly excellent heat conductor, and heat is conducted from contact area very well. I checked a rough calculation a number if ways and got similar results. Can't see the mistake, but there may be one. Other than the obvious 'there must be some mistake', anyone know of similar calculations or results or methods that I can have a look at ? Where does the knowledge that stylus gets hot come from ? Anyone got an infra red camera with macro function to check ?

[vinyl_junkie]

I have experience with ortofon DJ styli.
My nightclub E doesn't take some records well. Beats go like prr prr prr like it has troubles with too hard recording, or having to read too many tones at one time. So the sound deforms.
on some records. For the rest it sounds more balanced, natural. Not screamy in the mids like the conical.

I prefer elliptical, but with conical you are safe. Every record will give an reasonable sound quality. The shape and a low cantilever mass and needle pressure can do a lot well on a conical stylus.

I am aware of these issues and this is simply because they are awfull needles. To put it simple the make them too tough and thus comprimising sound big time. They have big issues tracking high frequencies let alone hot records.
Stanton 680EL's out track them and out perform them in just about every way not to mention a sound close to a Stanton 681EEE. These carts have no issues tracking highs or give you that awfull sibilance the Ortofon do.
The Night Club E is an awfull sounding cart..you get a more neutral balanced sound from the Pro although that is a very flawed cart too.

This is what a nos 681SE sounds like on a standard 1210mk2 using a Urei 1620 mixer...ditch the ortofon's for Stanton's even the not so good new Stanton 680E v3 sound better than a Night Club E.
I know it would be better if the audio clips were dance music but I wasn't in the mood lol so have some 70's and 80's funk

http://www.zshare.net/audio/50635939584074ab/

http://www.sendspace.com/file/62b1xd

[flavio81]

Many records are really playable except the end-of-side grooves, where the modulations get more narrow and distortion rises. Several say that a linear tracking arm is "the solution", but I am not totally convinced.

I use a linear tracking turntable (SL-7) with an hyperelliptical stylus. There's no serious increase of distortion at the end-of-side grooves, except for records who were already damaged by another turntable.

But i think this is due to the stylus not due to the tangential tracking.

The sss-sounds (sibilance) gets more distorted, as I figure is in the critical 3-6 kHz region, which probably is due to:
(...)
Naturally, these two could be due to wear, most probably by the use of elliptical stylii, worn or not, the most common ones used back then. I have a typical such record which I am now investigating.

A micro-ridge stylus will give much less sibilance (or no sibillance) than an elliptical on the very same record. I have heard two MP3 files comparing sibilance with a JICO SAS stylus versus an elliptical, and the difference is obvious.

[Thomas_A]

Many records are really playable except the end-of-side grooves, where the modulations get more narrow and distortion rises. Several say that a linear tracking arm is "the solution", but I am not totally convinced.

I use a linear tracking turntable (SL-7) with an hyperelliptical stylus. There's no serious increase of distortion at the end-of-side grooves, except for records who were already damaged by another turntable.

But i think this is due to the stylus not due to the tangential tracking.

The sss-sounds (sibilance) gets more distorted, as I figure is in the critical 3-6 kHz region, which probably is due to:
(...)
Naturally, these two could be due to wear, most probably by the use of elliptical stylii, worn or not, the most common ones used back then. I have a typical such record which I am now investigating.

A micro-ridge stylus will give much less sibilance (or no sibillance) than an elliptical on the very same record. I have heard two MP3 files comparing sibilance with a JICO SAS stylus versus an elliptical, and the difference is obvious.

I am awaiting the JICO SAS stylus for my V15VxMR, but it takes a few weeks before it arrives. I will do some tests then.

I have not got any info regarding the stylus shape of the SAS stylus, other than it is "thinner" than the microridge (I assume the side-radius) From the picture at JICO, the front radius appear to be quite small also and the SAS appear to be riding the lowest way down at the groove wall compared to the other style types (line contact, conical/elliptical).

[flavio81]

Many records are really playable except the end-of-side grooves, where the modulations get more narrow and distortion rises. Several say that a linear tracking arm is "the solution", but I am not totally convinced.

I use a linear tracking turntable (SL-7) with an hyperelliptical stylus. There's no serious increase of distortion at the end-of-side grooves, except for records who were already damaged by another turntable.

But i think this is due to the stylus not due to the tangential tracking.

The sss-sounds (sibilance) gets more distorted, as I figure is in the critical 3-6 kHz region, which probably is due to:
(...)
Naturally, these two could be due to wear, most probably by the use of elliptical stylii, worn or not, the most common ones used back then. I have a typical such record which I am now investigating.

A micro-ridge stylus will give much less sibilance (or no sibillance) than an elliptical on the very same record. I have heard two MP3 files comparing sibilance with a JICO SAS stylus versus an elliptical, and the difference is obvious.

[1200y3]

A pivoted arm must have less fricton than an affordable tangental arm, but a tangental arm can be made with lower mass. A tangental arm is very important on mono (lateral) discs. A tangental arm should allow for very even stylus wear and life.

A micro-ridge and hyper-elliptical are extremely sensitive to compliance, which is also relative to cantilever mass. A conical with a low mass cantilever can sound amazing. I did a lot of work figuring out how to remove cantilever haze, and discovered that without extreme factors, line contacts and micro-ridges are dangerous. Take Shure's V15 IV and then their berrillium designs, both quite impractical for the manufacturer. The berrillium was simply a way of avoiding extra work to perfect a standard cantilever. Then the V15 IV had a telescoped cantilever with a two piece bearing and it was famous for its conical stylus.

An MR can surely get some tight detail, but a great conical is the most inviting sound. The best toss-up performance was the hyper-elliptical, but still required technical detailing (compliance, low size cantilever, damped cartridge body, nude stylus, etc).

Just beware that sibilance and last groove distortion is still on the record even though the finner styli track below it. If grading records is important it should be done with a conical or .4x.7 elliptical. The Grado Gold will uncover it.

Sibilance will also be found on a new record if the stylus has poor compliance and too much tip mass. If you find a broken stylus but still attached (cracked) it will sound close to an MR. The cantilever mass is has been reduced on the stylus tip.

[midfi]

I had no idea that when I started this thread that it would take off like this! I've learned so much from you guys on this thread alone that I'm about to have an aneurism! Please carry on, maybe I'll learn some more.