Zen, Wait to you see a wheel. Now THAT's something amazing!
Zero Antiskate vs Stylus Wear
This article, based on a long term study, was “plagiarised” from another Forum. It’s quite an old article so apologies to “older heads” for whom this may be old news.
It comes from an era when light VTF = good, but was not necessarily true, however the basic principle of long term wear looks sound.
Styli were tested to destruction over their full lifecycle.
http://www.audiomods.co.uk/papers/kogen_skatingforce.PDF
Viewers may have to cut & paste but in the event of difficulty with the link I will give a brief summary :
Of 14 cartridge samples tested without bias, 9 of them suffered excessive wear on the inner groove. One was neutral and the remaining 4 were “outer wall”.
When bias compensation was applied to a group of 6 samples, the wear pattern that resulted was symmetrical.
Given the strong and logical argument that skating damages styli asymmetrically – and gives a skewed reading of the LP over time, the “deviations” are a concern i.e. why 4 of them behaved oppositely.
Poor bearings? Arm cable too stiff? Wrong geometry?
IMO most turntable enthusiasts considered it self evident that unilateral force would cause this type of wear pattern so we didn’t need to be told but documented study, even one as old as this, is always interesting.
The photograph of the spherical stylus is poorly resolved on this copy but it makes the point quite graphically.
Based on long term experience that the simplest things can affect the sound of a turntable, I cannot deny that the idea of “de-stressing” the cantilever by removing a poorly directed/located AS force IS attractive and may produce a degree of audible benefit…at first...(?!?!?!!!)
The doubter in me always asks the question : can a mechanical assembly successfully zero out all mechanical influence and give a pure result? (If true zero AS is the goal even arm damping might be prohibited?)
The principle of using excessive VTF (up to 50% more) to achieve the same “trackability”, without bias, it was suggested, merely accelerates the unilateral wear & tear with (presumably) commensurate damage to the LP(?)
The proposed compensation of up to ”50% extra VTF” sounded a bit excessive to me.
(I’d balk at applying more than 0.1g over maximum.)
Old as it is, I found this study mildly unsettling.
Comments and opinions are invited from both Zero-antiskate adherents and those who always use AS.
It comes from an era when light VTF = good, but was not necessarily true, however the basic principle of long term wear looks sound.
Styli were tested to destruction over their full lifecycle.
http://www.audiomods.co.uk/papers/kogen_skatingforce.PDF
Viewers may have to cut & paste but in the event of difficulty with the link I will give a brief summary :
Of 14 cartridge samples tested without bias, 9 of them suffered excessive wear on the inner groove. One was neutral and the remaining 4 were “outer wall”.
When bias compensation was applied to a group of 6 samples, the wear pattern that resulted was symmetrical.
Given the strong and logical argument that skating damages styli asymmetrically – and gives a skewed reading of the LP over time, the “deviations” are a concern i.e. why 4 of them behaved oppositely.
Poor bearings? Arm cable too stiff? Wrong geometry?
IMO most turntable enthusiasts considered it self evident that unilateral force would cause this type of wear pattern so we didn’t need to be told but documented study, even one as old as this, is always interesting.
The photograph of the spherical stylus is poorly resolved on this copy but it makes the point quite graphically.
Based on long term experience that the simplest things can affect the sound of a turntable, I cannot deny that the idea of “de-stressing” the cantilever by removing a poorly directed/located AS force IS attractive and may produce a degree of audible benefit…at first...(?!?!?!!!)
The doubter in me always asks the question : can a mechanical assembly successfully zero out all mechanical influence and give a pure result? (If true zero AS is the goal even arm damping might be prohibited?)
The principle of using excessive VTF (up to 50% more) to achieve the same “trackability”, without bias, it was suggested, merely accelerates the unilateral wear & tear with (presumably) commensurate damage to the LP(?)
The proposed compensation of up to ”50% extra VTF” sounded a bit excessive to me.
(I’d balk at applying more than 0.1g over maximum.)
Old as it is, I found this study mildly unsettling.
Comments and opinions are invited from both Zero-antiskate adherents and those who always use AS.
24 responses Add your response
To complete Raul's explanation, when the distance from the tonearm pivot to the stylus tip (P2T) exceeds the distance from the tonearm pivot to the center of the spindle (P2S), as is the recommended motif for nearly all pivoted tonearms, then you have "stylus overhang". When P2S exceeds P2T, then you have "underhang". I know of only one pivoted tonearm for which underhang is recommended, the RS Labs RS-A1. |
Thank you Moonglum for the very interesting article. Between this and Graemme Dennes article on Tonearm cartridge geometry analysis that Raul pointed me to, I've managed 2 hours sleep the past 2 days and zero work. I'm facinated and intrigued by this. My wife is ready to have me commited. Keep up the good work guys. |
Nick and Lewm, I should have checked my post, as I meant to say that the arm in Nick's straight arm example "has zero skating forces at one point, which coincides with it being a null..." (not overhang) The arm has underhang as measured from the turntable centre, and so experiences positive and negative skating forces, as the orientation of the arm varies as it pivots. There is just one point where both the arm and cantilever are tangent to the groove (as in a linear tracking arm) and so there is neither skating force nor tracking angle error. However, everywhere else the error becomes extreme and difficult to compensate for. To reduce the error there has to be overhang, and as this is increased until, at two points (which will later be the nulls) the errors are equalised either side of a particular value. The reason for cartridge offset is to minimise the error angle with regard to the stylus, and set the cantilever and stylus in line with the groove, thus constituting a null at two points, but this does not alter the angle between groove tangent, stylus and arm pivot which still varies across the record and is never zero. And it is this angle which generates the skating force i.e. that between the groove tangent and the arm effective length, and only at the nulls is it the same as the value of the equalised tracking error angle and the cartridge offset angle. |
When you guys mention overhang (or underhang) what exactly is that. I guess I want to know what the overhang is in relation to. Thanks Moonglum for the great information on AS. Between that and Raul's guidance to Graeme Dennes Geometry Analysis I have slept about 2 hours the last 2 days and didn't get a lick of work done. I never realised how interesting tonearm/stylus geometry and how such things shape what we hear. I'm fascinated guys, keep up the good work. |
John, You are the first guy who has agreed with me on this. Last year, I decided to ignore the most common explanation for skating force (as related to headshell offset angle) and re-think it from scratch. What I posted above is what I came up with using the remnants of my understanding of Newtonian mechanics as taught to me at a very fine liberal arts college many decades ago. I purposely avoided reading other explanations. After having done the analysis in my head, I never did get around to adding in the effect of headshell offset angle. So I am in no position to argue one way or the other about the magnitude of the skating force that may or may not be generated by that mechanism; I thought it was quite possible that headshell offset angle would mitigate or exacerbate the effect of stylus overhang and most likely that the effect would be different at different points across the arc traced by the stylus. Thanks for the URL reference. |
Nick, The forces you mention will be just the same in any arm, whether with straight or offset cartridge, as long as it has an overhang. And similar overhang or underhang will produce similar skating forces, everything else being equal. In your example, the arm has zero overhang at one point, which also coincides with it being a null, ie stylus and cantilever tangent to the groove. As soon as an arm has any overhang there will be skating forces irrespective of whether there are nulls or not. Cartridge offset is a bit of a red herring. See http://odysseytonearms.blogspot.co.uk/2011/10/antiskate.htmlfor more info on antiskate. John . |
Lew, what you describes makes sense but you must take directionality into consideration. First off, we are describing a hypothetical tonearm, it must be straight, the cartridge must be in line with its axis and it must not have an overhang. As you stated if it has an overhang it will never have a null point. But let us assume that it has a null point at the groove which is tangent with the tone arm pivot point. At this one point there will be no skating force. Now take a standard arm at its null point, due to the offset angle it will have a skating force. Now as this 0 offset arm travels away from the null point, in the spindle direction then the skating force should be pushing the arm in wards, however moving out wards towards the record's edge the skating force should be pushing the stylus out wards. So I agree, that there is a force, but it is not the same as the skating force caused by the offset angle and I would guess that it is much smaller in magnitude. |
Nick, But consider this: if a straight tonearm (no headshell offset) is set up such that there is any amount of overhang (meaning stylus tip overhangs the spindle, as is typical for all conventional tonearms), then the stylus can never be tangent to the groove walls, because, by the Pythagorean theorem, where the P2S distance is the hypotenuse of a right angle triangle, the condition a-squared (where a is the pivot to stylus tip distance) + b-squared (where b is the radial distance between the stylus tip and the spindle) can never = c-squared, the P2S distance, because a>c. So now I posit that lack of tangency of the stylus to the groove walls will per se produce a skating force. This is NOT to say that offset angle cannot also cause skating force. Picture a little red wagon where the front wheels are fixed in line with the rear wheels, but the long handle is free to pivot left to right. Now if you pull the wagon using its handle forward following any straight path that is parallel to but not directly in line with the direction determined by the four fixed wheels, you will generate a side force on the wagon. I think this is true. |
First let me thank moonglum for posting the link, the paper was very interesting as were some of the others listed on the Audomods site. I would have to agree with Raul, skating force is a direct result of offset angle, the greater the angle, the greater the vector force created. That is the angle the stylus is offset from line drawn between the stylus and the pivot point of the tonearm, regardless of the shape of the arm. Here is a video by Wally Malewicz that explains the theory and demonstrates the ill effects of poorly set AS. http://m.youtube.com/#/watch?v=iEVuP6-zYLE&feature=plcp Don't get me wrong, the Points raised by Kogen are valid they are just secondary. As i see it, if you could line up the stylus in the same plane as the tonearm then there would be no skating forces. Of course this would cause enormous tracking error, so it remains a hypothetical scenario. |
Thanks for bringing that old study to our attention. I don't recall whether I ever read it the first time around. I could summarize my response with three statements: (1) I don't know who ever promulgated the idea of increasing VTF to compensate for skating force without applying AS, but it's ridiculous on the face of it, since skating force will go up as VTF goes up (because friction of the stylus in the groove will also go up). (2) We all know, and you guys have accurately restated, the pitfalls and inadequacies of the AS mechanisms on a typical tonearm, but the study would suggest that imperfect application of AS is better than no AS at all, unless one applies far too much AS, in which case one has created a new problem. (3) So best compromise is to use AS but use it conservatively. By the way, Raul, in passing you wrote something that suggested that headshell offset angle is a culprit in causing skating force, but even a straight tonearm with no headshell offset will generate skating force, so long as the cartridge is aligned with the stylus tip overhanging the spindle, because in that case the cartridge/cantilever is never tangent to the groove. (Not Newton in this case; Pythagorus is responsible.) The RS-A1 tonearm attempts to mitigate the problem by using UNDER-hang; the stylus tip is recommended to be about 20mm short of the spindle. (I am really testing this idea out, about the effect of overhang, but it seems correct to me.) |
Dear Raul, I cannot agree more. Like you say, perfection can only ever be a theoretical one. Adjusting factors e.g. on a per record basis would be soul destroying because one factor offsets others – which in turn would require correction. Such levels of technicality would quench the spirit and defeat the very purpose of listening to music. It’s eminently more sensible to spend many days and many records advancing the setup to a happy medium then simply enjoying it. Perfectionism is only useful insofar as achieving the working ideal for one’s own turntable/s whilst in full realisation that temperature, humidity, record warps, manufacturing errors, stylus cleanliness, record cleanliness, etc are the Devil’s way of making sure it doesn’t always run smoothly. It’s true, we can change our ambient temp or VTA or VTF seasonally to compensate for Summer-Winter changes, depending on which is easier, and we may clean our styli at different intervals, and if we have easy VTA adjustable arms we can alter the level of the arm from 120g -180g as easily as throwing a switch - thereby keeping that idealised relationship unaltered but when it comes right down to it, it’s all about maintaining a reasonable equilibrium. Regarding your comments about record warps, I do find it interesting that if we introduce a 120g to 180g VTA offset we can clearly hear it and quantify it, yet our ears can be extraordinarily forgiving when it comes to warped LPs (which affects all LPs to at least some degree). Perhaps the ear/brain interface actually compares average rather than instantaneous values? :^) Speaking of mis-drilling : one of the most obvious examples of wrongly produced vinyl is the HFN/RR test disc. I’ve owned a couple of samples of this and the centre was always drilled 1 or 2mm off centre. This would result in a wavering effect when using it to adjust bias, with associated intermittent cyclic mistracking on the more severe tracks. (Personally, I only use music to adjust bias but if one must use an HFN/RR I would advise only to focus on the fadeout of the 12db tone. With some carts of varied trackability and in various states of wear, I’ve heard the tone pulling to one side as the signal level falls to zero instead of remaining centred…although don’t be surprised if your cart shows no difference at your ”ideal” setting.) Best regards… |
Moonglum, You're welcome! And just to make it clear, I do not question whether skating forces are of concern or to be ignored. I'm certainly not going to argue against the laws of physics. I merely noted that certain designs, such as VPI, might be handling the issue in their own way, whatever it might be, a strategically positioned wire or twisted wire. If that is the case, the tests are of limited value if done with different designs. I'd still very much like to examine my stylus at some point to determine any wear due to the skating forces, but right now I'm just going to enjoy the music! |
Dear Moonglum: There is no doubt that we have to take in deep care on the right TT/tonearm/cartridge set up mainly recovery all the grooves recorded information and to degraded the audio signal the less. Sometimes we fail on that " perfect " set up and if not we the analog medium is in charge to, due to its multiple imperfections, make it fails. We can have a perfect set up but the off center LP has to much to " say " and the non-flat LPs full of waves makes that our " perfect " set up goes down changing all the time the VTF/VTA/overhang during playback and we can't do almost nothing to stop it. There are so many set up parameters that always affect the cartridge traking/ride that in some way we are at " random " for what the analog medium " decide " it self. The analog medium in theory could be exact like mathematics but on playback we experienced many times that that analog set up parameters theory is not acomplished. Imperfection is the name of the game. Anyway, I always try to be as accurate as the medium permit me. Regards and enjoy the music, R. |
Dear Actus, Many thanks for kick-starting the thread. I had indeed given up on it a while back :^) Yes, the VPIs are among those odd cases where the cord is temptingly placed for manipulation. I suppose to verify that there was no interference from it you would have to do the Balanced free-arm friction test to see if it slows or accelerates at that "twist" setting? Not sure how easy that is to perform with a unipivot design such as the VPI. Since you're happy with the sound and the tracking, there may be no need to question or test it. :^) Best.... |
Dear Raul, Thank you for your kind remarks. I agree that based on long term studies like this there is a fundamental cause-and-effect which cannot be ignored and unilateral stylus wear is not an option. I think for this analysis they must have been using short-life styli (perhaps of the order of 400-500 hrs?) as opposed to todays 1200 hr MC tips? To quote Len Gregory, “…the stylus burns more than it wears. Diamonds, unlike the song, do not last forever….”. (Len has always been of the firm belief that 1200 hrs is the point where we should be considering a re-tip or replacement - significantly, "regardless of diamond quality...".) Of course, coming from a professional re-tipping company I would expect such a strict definition of cartridge life :) Granted, careful use and the judicious application of anti-skate could prolong that life but with, e.g. £5K carts, I wouldn’t be leaving anything to chance. In the case of higher quality and more finely finished diamonds like the Allaerts it has been said that Jan Allaerts inspected diamonds 17 yrs old or higher and affirmed very little wear. In such an event my attention would turn to the records :) I recall even in the decade that followed that report, the industry thought they were minimising record wear by tracking at 0.5g when in fact they were exacerbating it. Sometimes the best intentions can be misguided. Best regards, |
Dear Moonglum: Thank's to brought here again the AS critical and misunderstood AS subject. I know that you started this thread because the worry of stylus wear but over and behind the stylus wear subject the AS issue has more critical implications. Like Nandric pointed out: we can deny Newton laws that apply to the AS subject as Tonywinsc posted. Some of us audiophiles said that we hear better LP performance quality level with out AS but this is only a subjective point that we can't really prove in any ways other that " I like it that way " that for the overall subject research means almost nothing. That old Audio article you linked is a learning one ( for say the least ) on the AS subject that kill all and for ever different " myths " about and against AS. Between other things we can read there the importance to the AS aplication that the cartridge/tonearm overhang stay in precise/accurate way according the geometry set up alternative we choosed ( Löfgren, Baerwald, Stevenson and the like. ) and here we have to remember that each one we make changes on VTA/VTF we are changing too overhang and we have to re-set because that overhang change affect the AS force and tracking cartridge habilities/tracking distortion. According with that AS study and by common sense AS aplication improves tracking cartridge habilities that means more recovery music information from the record grooves with lower distortions and this sole/unique fact makes that AS parameter must be aplicated always in a pivoted tonearm that has offset angle characteristic. IMHO, AS is not something that we use it if want or not, I repeat it is a must to. Now, maybe some of us heard no improvements through the AS aplication because that AS force aplication is not very well aplicated by the tonearm design but not because AS is useless: no, it is not. The PUA 237 is a clever idea on the tonearm AS use and if we look to the AT 1010/1100 tonearm designs we can confirm what the study showed: that differnt stylus shape needs different AS use. The AS overall subject as many other audio subjects is not solved yet at 100%, so we have to expect that things on AS use improves in the near future. I for onece will be to re-set all my tonearm/cartridge I use according with what we are learning here, this means using AS in the more precise/accuarte way I can with the tonearm /cartridge I have because one of my main goals in my audio system is to lower distortions at each single audio link in the system chain and improving cartridge tracking is a primary way to achieve that target. Regards and enjoy the music, R. |
This link is to an old post where I made some comments about Anti-skating. This article is very good and the article's conclusions, fortunately for me, are about the same as I stated in my post. http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1325141286&openusid&zzTonywinsc&4&5#Tonywinsc I did some research and as I recall, the record materials , ie. vinyls, used became more consistent in the 70s and 80s which is good because the coefficient of friction is the main contributor of skating force. Also interesting to note is the article stated that a constant Anti-Skating force from start to finish is a minor factor with respect to performance and stylus wear. Setting AS force by ear may/or may not be optimum because no AS force will result in uneven stylus wear. I set mine by the dial on my tonearm; but my final check is with a test record. |
To deny Newton looks to me ridiculous. The real problem is the different skate force depending from the record radius as well from the stylus shape. Those are also mechanical facts. The only tonearm I know of with variable anti skate provision and correct opproach of the problem(s) involved is the Sony PUA 237 (+ PUA 12'' ). This however does not mean that the involved problems are easy to solve otherwise every tonearm designer would already done it. Regards, |
Moonglum, I just noticed this tread. As a VPI Classic owner, I found that the sound from table and my Lyra Delos is better with no anti-skate applied. I believe that's the overall consensus among VPI owners, as is Harry's opinion. I experimented with the anti-skating device and a test record, but varying the anti-skate force made no difference with the test record. I also have never noticed any cantilever deflection as the stylus hits the lead-in groove so I stopped worrying about this issue. It's possible that the tonearm wire (in my case silver Valhalla) provides just enough of anti-skate force to make any additional anti-skate unnecessary. I can't say for sure, but I think anti-skating is not a general yes or no proposition, but needs to be discussed and evaluated with regard to a particular tonearm set-up. That's why studies and tests such as the one you mention might be of some theoretical interest, but have little practical value. My 2 cents. |
