Dear Timeltel,
You wrote, and I comment:
"Two items related to the discussion, go to this link and click on "owners manual", the geometry of the tonearm is pictured on the last two pages and also gives two offset angles, one for the 12" and one for the 16" Sony arm. Hopefully it can be seen that the importance of offset is a matter of alignment and not the "offset" appearance of the headshell."
This kind of makes me say, "Duh!" Of course the offset angle is there in order to maximize the tonearm geometry or "alignment". What we/I am saying is that (additional) skating force is an unhappy consequence of offset angle. I thought we all agreed on this and the only area of controversy was my additional proposal that lack of tangency to the groove of a line drawn from stylus to pivot is an additional factor (because even if there is zero headshell offset angle, that line will still not always if ever be tangent to the groove).
"That a headshell appears to be out of congurence with the center-line of the arm and is largely the cause of skating needs to be dismissed." OK. Dismiss it for me in terms of the physics. I don't mean this to sound confrontational; I hold you in high esteem as a friend and source of information that I take to heart. I am willing to be wrong and to be educated. But many other sources do flatly maintain the importance of headshell offset angle in the generation of a skating force.
As regards the role of VTF. All other things being equal, which I realize is not the case, an increase in VTF should be accompanied by an increase in friction and therefore an increase in skating force. But if the stylus of an MC is typically riding at some level in the groove where less stylus drag is generated, perhaps that factor could dominate over the effect of VTF per se.
Dear Raul, You are too fickle for me to be unsettled by your claim of the superiority of the Astatic to the Grace. Did you compare them both in the same tonearm on your system in the last day or two, or are you going on your memory of the sound of the Ruby? Does it not also count that our systems and probably our preferences are miles apart? Actually, I have no basis at all to claim that the Grace is better than the Astatic, just that it's really really nice for me right now. I am not tempted. |
Dear Lewm: Last day I did it. Normaly when one of you talk about a cartridge performance I give a listen to that cartridge like with the Grace and the AKG or the MF-200 that Idid not bring here but from other of you.
+++++ " Does it not also count that our systems and probably our preferences are miles apart? " ++++
certainly not, I'm not checking which cartridge likes me but which one is better than the other through a comparison well defined and precise process.
Unfortunately and as you said: you don't have the MF-200 on hand, maybe in the future.
Btw, if I can I will test the MF-300 next.
Regards and enjoy the music,
R. |
Hello Fleib and thank you for the very kind words. Not personally knowing you or the group but eric does throw a wrench into posting a response with out intentionaly coming off in the wrong way. And trust me i mean no disrespect or harm to you or the group just trying to learn at the senior level.
Yes universe is a dandy of a cartridge. And mr. Mehran is a good audio buddy but being on that fixed income time in life i just cant afford to reup again. Yes i go the extra effort cleaning my vinyl and it pays off with extended life of my cartridges. That universe gave me a ton of musical enjoyment but thanks to Raul and the posters here the MM alternative is no slouch. I dont believe to my ears I'm getting any less in the musical enjoyment department with MM. In fact these fine music makers i have on hand pretty much all can hang with universe. I do believe that less is better as in the vintage fisher 400c phono stage in the preamp im using has something to do with the pleasing sound my system delivers.
I have spent some time reading up on anti skate on the net and what i think the biggest problem is getting the proper adjustment across the whole record. Along with finding the right weight to apply. Havent listened to any music the past few days hoping to experiment tomorrow with AS.
Mike |
Never mind. I am reading the Sony treatise on their bias compensator. Need to see where it leads. |
Regards, Lew: "I thought we all agreed on this". Yep. Matter of fact, said so. Two days ago.
Being the knucklehead that I am and think of it as you wish, I have a hard time believing that if one were to twist a cartridge in the headshell so that the cantilever was in line with the center line of the arm (zero offset) that with any but the most extreme stylus profiles skating would be impacted to any significant degree and that would depend on what you consider "significant". Really this is nothing more than the idle speculation of an idle mind but look at it another way: Regardless of offset, go for (an exaggeration) 90* if you wish, if a conical stylus is used and the point of the stylus itself is in line with the CL of the arm, would it really result in much/any more side force than if it were perfectly on axis? Really?
Three things I need to qualify. First, I'd like to think that on occasion a quasi-conversational exchange of ideas might take place on this forum, there're some pretty intelligent people here. Next, to remind myself that a sphere (or was that a conical paddle?) ;-) offers equal resistance to a consistent force applied from any aspect. Vector. And finally, as there are those who like to play this particular game, if anyone is intending to ask for proof concerning consistent friction (regardless of offset) with a conical stylus, I'll first ask for hard proof that it isn't so. This isn't a thesis, damn it.
As to additional VTF, tell me that when young, if a Lp tracked badly the first tool you thought of to correct the situation didn't come from the U. S. Mint? As mentioned when written, off the top of my head and not terribly scientific, but in that example the needle obviously wasn't equally involved with both groove walls and this might be a pretty good place to start. Could we please just go with that? If it's thesis time, I'll get back to you in no less than a week. If you have any alternative thoughts or sources to site (either one works for me) as to why Stiltrains (Mike, excuse the impersonal reference) could run a Universe (didn't say but I presume it was in the 1.9-2.0gm VTF range) for 2700 hours, no anti-skating, and still have even stylus wear then fire away, I'm all ears. Err, eyes.
Lew, thanks for the consideration in your manner of asking. Any solutions or alternatives you might suggest for the questions you asked me would be most welcome. It's a subject I'm obviously interested in and I"m always open to opportunities for being better informed, however I'm pretty sure the horse is already dead.
Peace, |
|
Tangency and AS are two issues that impact on each other. If we agree that skating is caused by the additional vector from offset, then tangency becomes a separate but related issue. After all, a pivoting arm is only tangent to the groove at two points on a record side. I keep referring to linear tracking arms, and their lack of skating. Many linear arms can not maintain perfect tangency 100% of the time, especially with records with off-center spindle holes. There is still no skating because there is no offset. When skating was first explained to me, back in prehistoric times, I was told it was because the arm/cart had inertia moving toward the spindle. Wrong!!
Because the one perfect setting for AS is impossible to achieve, we need a sensible way to find a satisfactory setting. There are 2 factors that effect AS, position on the record and stylus velocity. The technique of sighting your cart from the front is effective in ballparking. You can try this with a "normal" record, representative of your regular fare in terms of volume. If you haven't tried this, I think you'll be amazed at how revealing it is. A mono vocal record is often recommended to get a good center. If you set your AS for the worst case possibility, the loudest passages, then you'll have too much AS during quiet passages, so you have to find a happy median. IMO, too much is worse than too little.
All set-up parameters impact on each other and it's a mistake to think you can optimise one in isolation. Azimuth is one that that goes hand in hand with AS and has similar adjustments and consequences. Viewing from the front, if the needle is tilted so the top is going to the left or spindle, the right ch high frequencies suffer. That mono vocal record is very effective here as well. Not all styli are mounted perfectly in line with the cart body. It might look funny, but sometimes the whole thing must be tilted a little to have the tip straight up and down. If you're having trouble hearing it, get some kind of output level indicator, PC program, test record to help you. VTA/SRA is another setting that impacts. As you adjust one thing, the others come into focus.
The consequence of alignment error is the needle bouncing off the grooves at an odd angle. I hear mostly a phase distortion between channels. I'm not sure if phase is the right description. One channel is delayed with respect to the other, so the information at any instant in time is slightly off. I can only hear this if the error is greater than 2 or 3 degrees (I think). With a familiar set-up, I hear the difference between Stevenson or Loefgren A or B, especially at the beginning. Longer arms minimize this and VTA/SRA differences but have another issue, moment of inertia.
My apologies to most of you who know this stuff. Some people and many newbies seem to need a little advise. For the next installment: William Tell saves Sir Issac Newton and we all go flying off into space.
Regards, |
One thing I didn't describe well is alignment error consequences. The odd angle is in relation to the cartridge and cantilever. Although it's the tip that actually traces the groove, it's the movements of the cantilever that get the generator going. Alignment error has audible consequences. Time delay or phase error might not be the right description. I'm not sure what is.
Regards, |
Dear Fleib: Good explanation on set up. I only want to add that VTF/SRA/VTA are not only related each to other but overhang too. When we are talking of " perfect " alignment as Lewm likes we have to take ( as you pointed out. ) in count all the parameters around the one we change as is the case of overhang because if not then that Löfgren A/B Stevenson or whatever will be off that set up.
It is complicated because: what happen for example when the Löfgren A is right on target and we change VTF or SRA? then we have to reset that alignment and maybe when we reset it we don't like what we heard because that tiny overhang change moves the stylus tip and maybe we have to change again the SRA or VTF or both and then what after this.
Every set up cartridge change must " respect " the original overhang of that set up.
Regrads and enjoy the music,
R. |
Timeltel, I am with you on this. Lack of tangency to the groove is all that is needed to generate a skating force. I need to think more about the added or supplementary effect of headshell offset angle. But on many fora around the internet, skating is ascribed to headshell offset, and I was influenced by that because I had not thought it thru for myself. Further, while sitting at a sublime live jazz concert last night I came upon a proof that for our conventional pivoted tonearms the stylus tip is never parallel to the groove wall, based on the Pythagorean Theorem. Hence, there is always a skating force of varying magnitude. (I am finally remembering how to do vector algebra, which will allow me to consider the headshell offset angle, but I need to sit down with pencil and paper.)
Interestingly, for the RS-A1 tonearm, which specifies 21mm of stylus tip UNDERhang, the stylus is likely to be parallel to the groove wall at some point in tracing its arc across the LP. Thus canceling skating force. |
Timeltel, see acos lustre 801 report third paragragh page two for a decription of a tonearm that uses magnets to adjust antiskating. Caution, allot of marketing going on in that report.
http://www.vinylengine.com/library/acos/lustre-gst-801.shtml |
Regards, Fleib: Here we go again. You said "There are 2 factors that effect AS, position on the record and stylus velocity." So far, so good. Next, "skating is CAUSED by the additional vector from offset".
So far there have been four influences identified. Vector one: Centripetal force was defined by Sir Isaac three hundred years ago. Call it side force if you will, it has stood the test of time and is most definitely a factor. Second vector, overhang. As the tonearm traverses the Lp it follows the groove. This groove spirals towards the center. Are you familiar with the Archimedean screw? Sometimes referred to as a screwpump, it is a machine historically used for transferring material from one location to another by turning a spiraled shaft. As the spiral becomes more aggressive, increased forces are exerted against the material being transferred. These principles have been repeatedly observed.
Here's where you'll have to use your ability to visualize alternative circumstances. A spiral groove on a flat surface in rotation will also move an object anchored at one end but free to follow the groove at the distal end. As overhang is increased, the stylus encounters the groove at increasingly greater angle of incidence, side force is accordingly also increased. This is the "opposite and equal" part of Newtons' laws of motion, it was previously agreed upon that the forces exerted upon the stylus by these two vectors are variable, centripetal force is the first, the angle of incident is the second variable.
Both of these principles are dependent on downforce or VTF, this is a third vector and also variable.
We're down to offset now, which is, as previously agreed on, primarily a matter of alignment. Please reconsider the conical stylus and the fact that regardless of azimuth, VTA, SRA or degree of offset, it contacts the groove walls at two points and these contact patches are circular. Two degrees of stylus rake or any amount of rotation, or "offset", will not, as long as it remains in line with the centerline of the tonearm, alter this. It's been so frequently observed that stylus friction is reduced by styli with Shibata, LC or ML profiles that it shouldn't be necessary to offer references. Should one wish confirmation a little research into works published by Norio Shibata of JVC or the papers relating to stylus wear offered by Shure Bros. in the 1970's might be productive. I don't think any of us are so inept that we'll run a cartridge so far out of alignment that "offset" errors are going to be of any great impact, especially in consideration of the scale of magnitude of the forces exerted by the first three variables. "Where's the beef?"
I sincerely hope that these principles remain constant as should you manage to repudiate them, the laws of motion will be revoked and perchance we will all join Misters Tell and Newton in outer space. This would be most regrettable.
Peace, |
|
Skating force is a centripetal force because the tonearm resists movement in the actual direction of the force vector that is generated by lack of tangency of the tonearm/pivot/stylus to the groove wall. That vector is actually changing in direction AND magnitude as the stylus goes from outer to inner groove and is never truly "centripetal, but only its centripetal component (component that is perpendicular to the tonearm/pivot/stylus line) is "expressed", because of the stiffness of the tonearm. Thus only the force vector that is along the arc defined by the location of the pivot and the tonearm effective length is in play = centripetal force = skating force. Besides this geometrical source of skating force, there are also the variables related to friction, which is affected both by stylus shape and groove modulations, both of which alter the magnitude of the skating force but not its direction. That's my story, and I'm sticking to it. I can prove it, if you want. (Without having completely read the Sony treatise, I have a feeling this is pretty much what they said using different words.) The headshell offset angle can figure into this only possibly by changing the angles involved. |
Timeltel, Lewm, I wrote that as a practical guide for AS considerations, not as a physics lesson and repetition of everything that's been said. Apparently neither of you figured it out yet, because you're both only partially right. NO, centripetal force is not a factor. It is so inconsequential in this case, it really doesn't matter and any additional skate would be compensated for.
Vector 1) VTF causes friction and the groove pulls the stylus at 180 degrees to the (arm) pivot, or in line with.
Vector 2) Cart is offset to maximize alignment. This same friction/groove pulls the stylus at 180 degrees to the cantilever, or in line with offset.
Vector 3) 2 forces combine to cause skating.
Conical styli use VTF and have friction. If mounted on a pivoted arm with offset, there will be skating.
A stylus being other than tangent does NOT cause skating.
You're making more of this than it is. No need to reinvent the wheel.
Regards,
|
Regards, John Gordon: Thanks for the reference. I thought your information useful and presented in a practical and easily read fashion. Input from professionals is always welcome.
Peace, |
Timetel/John_Gordon,
Thanks. Expertise is really useful and most welcome.
As always... |
Hi Raul, Do you have experience with any Coral cartridges?
Years ago I had an Adcom HOMC that I believe was made by them. The SAE 1000 is said to be there's also. I seem to remember something about a model 777?
Thanks, |
Dear friends: Always is important to know and learn why and how " things " works ( as AS and any other audio subjects. ) to make concience of the importance of the set up on that " subject " regards.
Till this moment almost no one posted not what happen or not but what we heard when applying the AS in correct way or incorrect way, I think Timeltel mentioned about but there were no " quorum " to speaks on listening experiences. At the end and after the " learning time " the most important subject ( IMHO ) is or are each one of us experiences under playback.
Same happened with my last post to Fleib where I left a " question " in the air: how to match VTF/VTA with overhang tonearm cartridge geometry set up? because when we make a tiny change on SRA/VTA or VTF exist a change in overhang too and we have to reset this parameter that could change those VTA/SRA/VTF tiny changes.
On this reset set up changes the stylus tip change its position and " reads " the grooves with tiny differences that maybe through playback could like us at random or not.
What are your take here or what do you think about? is there something wrong that I'm unaware? am I wrong? why?
Regards and enjoy the music,
R. |
Dear Fleib: As you I had experiences with Adcom and SAE but was many years ago and what I remember due not only to the time already pass but the differences in my system my opinion about is almost useless.
In the other side I can't remember any first hand experience with the Coral one ( direct to Coral. ).
From some months now those Coral, Adcom and Saes cartridges were on ebay/agon sites but I was and I'm not tempted to test one of those cartridgesm maybe we have to do it and see what Coral has to " shows " us.
Maybe some one of the Agoner's could put some " light " on that subject.
Regards and enjoy the music,
R. |
Happy Mardi Gras!!!
http://experiencemardigras.com/
|
Regards, Dgob: You are being too kind. I thought the discussion was educational, entertaining and on occasion deliciously nonsensical. Everyone else made points to be considered and there's still some difference of "opinion" evident so for now, "the jury is still out". I took one look at the fomulae offered by Sony and decided my once fair math skills had atrophied. If Lew can wade through it and make it sensible to the rest of us, I'll be even more impressed with his capabilities.
As to the nonsense, I found this bit "somewhere". Sorry 'bout that.
"Poem"
by Henry Gibson
Tonearms swing like a pendulum do.
AS calms its travel from rim to spindle through.
Take it away and then to late you'll scowl,
The inner groove your stylus did plow.
Centripetal force Newton first knew.
Then it was overhang
Your channel balance further to screw.
Magnets and springs, weights depending from a string
Unkindly tension and torsion these will make true.
An evenings' journey of Pythagorean jazz,
Repetitive Mantras of rock, perhaps something soulful and blue.
The mathematical progressions of Bach, this some say will do.
Introspection found in music, just think it through.
All said and done in that vector stew,
Listen to your favorite, you'll hear it anew.
Dial in your anti-skating and AS always,
May the force be with you!
Peace, |
alas the slightest amount of AS applied to my micro arm can be added without me thinking theres a lost of my dearest SOUND. what i am getting from the added AS to playback is tighter bass and those sounds with in the image of the sound stage are tighter also. i would say thats for the better.
i just added the AS assy back to my triplaner not sure if just the lever is to much. dont know how herb came up with the 4g weight supplied with TP but it seems way to much no matter where located on the lever but who am i to question his design and im not, love the arm.
i am one who promotes getting off your butt and trying different things with our vinyl playback and systems. i was wrong to think AS was not necessary and thats getting back to triplaner cause i used the supplied weight rubber donuts brass washers and more and was happy with out any AS. the way the wiring passes thou the arm tubes and comes out of the arm tube could play a part in applying some AS on triplaner possibly.
i bought a wally skater years ago and never removed it from its wrappings. going to give it a good look over/use compare that to my ear method adjustment and hear where that takes the only thing that matters to me SOUND.
Timeltel on those moodys tracks theres not much of a difference in locations/sounds with as you mention there position in the soundstage with or with out AS here. sound wise Thomas flute is woodie and wonderful i sure miss him touring with the band. Norda Mullen who took his place is excellent and looks a lot better than ray.
throw me something mister
mike |
well i have my answer and to those using a triplaner you could have wire interference with your anti skating settings. the wally skater is a cool vinyl tool that gives you a percentage of skate.
with my micro all was as wally has stated in his instructions of WS tool. without antiskate theres none in fact negative numbers. when AS is set on the red line the percentages fall right in to what wally advises.
now with triplaner the only arm ive used i 4 years or so its a whole different story and explains why i did not need to add skate to mine for good sound. with just the lever only no weight added i am getting what wally recommends front middle and rear of the platter. without any applied skate the percentages are only off by 1 or 2. as emeril lagasse says bam, there it is.
i feel better playing around and learing something today. and it was a good mardi gras right here at the house.
now show your xxxxxs
mike |
Mike, nice to read about your recent experience with AS and your arms. As per Raul's request, your post was an empirical description of consequences or benefits. I took it for granted that the goal is to get a proper image and center. Bass performance is also impacted because excursions between groove walls will be affected by side forces on the arm. There are programs available now (like Feickert) to see performance plots on your PC. You could also see azimuth at the same time. Someone on another former has the Feickert program and wound up using a mono record. I think David knows something of what's available and might be able to recommend one.
Regarding the theory behind AS: I really don't know if centripetal force is the primary cause. The arm swings in an arc and it is accelerating, so maybe it is. Then, is the additional force from offset a Coriolis force? [Joke]
Point is, it's moot as far as empiricists like I am concerned. I know that conical styli use friction to stay in the groove and are subject to the same considerations, possible less so than other types. BTW, a .2 x .7 has smaller contact area than most conicals. I don't think tangency has much to do with it. Why would tangency have an affect on these forces, would it negate friction, the primary force?
For practical considerations, adjusting AS, there are two primary considerations to take into account. If you adjust for the loudest passages or highest velocity on a test record, you'll have too much, most of the time. I find a mono female vocal, most useful to get a center image.
Regards, |
Dear Fleib, You wrote, "Regarding the theory behind AS: I really don't know if centripetal force is the primary cause."
Skating force IS a centripetal force. "Centripetal force" is just a descriptive term that tells us that the vector of the force is directed toward the center of a circular path of a body in motion. Centripetal force does not "cause" anything. What causes the (centripetal) skating force is the fact that conventional pivoted tonearms are never tangent to the groove wall. Because of that there is always a force vector generated that is in a direction determined by the angle between tangency and the actual angle of the tonearm wrt the groove. This force is per se not centripetal, but we only "see" its centripetal component because the mechanical stiffness of the tonearm translates the actual force vector (which is always changing in direction and magnitude) into one that IS unidirectional and is centripetal. (The tonearm only allows free rotation in one arc, directed toward the spindle, i.e., "center-seeking".)
As I see it, the skating force is a force over and above that which is exerted on the stylus tip by the grooves to guide it in a spiral toward the center of the LP. That force by itself would not induce the tonearm to skate. Anyway, that's what I am thinking at this point. The forces exerted by the groove wall would be present for any and all styli riding in any tonearm, even linear trackers. (I start from the fact that in an air-bearing linear tracker, that force is the only force acting on the stylus tip, yet we say that linear trackers do not induce a skating force.) |
From physics class:
"Any motion in a curved path represents accelerated motion, and requires a force directed toward the center of curvature of the path. This force is called the centripetal force which means "center seeking" force. The force has the magnitude." Clearly in our case this force is friction and the direction is defined by the groove and the fixed arc of the arm. Also:
"Centripetal force is a force that makes a body follow a curved path: it is always directed orthogonal to the velocity of the body, toward the instantaneous center of curvature of the path." In this case the force is not what makes the stylus follow a curved path. That path is determined by the stylus and pivot position being fixed. That's why I have doubts if it really is centripetal.
"What causes the (centripetal) skating force is the fact that conventional pivoted tonearms are never tangent to the groove wall. Because of that there is always a force vector generated that is in a direction determined by the angle between tangency and the actual angle of the tonearm wrt the groove." IMO this is totally an unequivocally wrong. 1)There are two points along the arc that are perfectly tangent. Does skating stop for those points? 2) Friction keeps the tip in the groove which determines direction. Is it dependant on alignment or being tangent, or can there be friction and forces regardless?
"The forces exerted by the groove wall would be present for any and all styli riding in any tonearm, even linear trackers. (I start from the fact that in an air-bearing linear tracker, that force is the only force acting on the stylus tip, yet we say that linear trackers do not induce a skating force.)" Most linear trackers AFAIK, use VTF and friction to keep the stylus in groove. Your point supports what I'm saying. The only reason a pivoting arm and skating could be considered centripetal is because the path of stylus is curved, the force is toward the center, and it's accelerating.
It was stated by physics type people that the vectors of force derived from friction, by the stylus, is what causes skating. Centripetal force is usually applied to spheres orbiting a larger body, or twirling a ball on a string. It would also apply to a car spinning out on a curve so maybe it applies. Perhaps if you find the answers to these questions, we'll know.
Does a pivoting arm with no offset, skate?
If a linear arm is not tangent at some point, does it skate at that point? Why, because of lack of tangency or no offset?
Regards, |
Hey guys, I can't add anything to the why? or how? of AS, only a further question.
I recall reading some years ago about Thorens' research on skating force and their finding that correct AS would actually change as the arm/cartridge moves across the record. If that is correct, how can we best compensate for skating force? Should AS be set for a mid-point on the LP (thus an average) or should it be adjusted within the last third (if that is subject to greatest distortion due to the shorter radius)?
Sorry if this muddies the waters even more. |
Pryso depending on the arm that factor has been included in the design. Both my triplaner and micro have that feature. I am not pushing wallys tools but his wally skater will show AS and its percentage at any point on your lp.
Mike |
The manual for my Technics epa 100 mk2 says to set anti-skate to same number as vtf. For my mm carts that's between 1-1.4 grams. Is this crazy?
I can't hear a repeatable difference between .5g and 1.5g. For this, I'm more worried about record and stylus wear than sound quality. |
Hi Mike, can you explain how AS is built into an arm to vary as the cartridge moves across the record? The most common mechanism I'm familiar with is the string and weight, attached to pull the arm counter to the skating force. I don't remember much from physics so does that change as the arm moves across the record and the distance of the weight from its support (fulcrum) shortens? I believe other arm designs (your MS?) utilize a spring for the counter force.
Banquo363, setting AS equal (on a scale marker at least) to VTF is a long standing recommendation, including by many manufacturers. More recent thinking suggests that AS should be 2/3 of VTF. Thus a simple example with 1.5 g VTF, set the AS scale to 1. I don't believe any of the AS scales are intended to represent specific weight so it is not 1-1.4 grams. |
That's what I was talking about regarding skating. The force will vary depending on position and stylus velocity. I think the idea is to find a setting where you get a centered cantilever at moderate velocity at different points on the record. Most AS controls are calibrated for a percentage (15 to 20% ?) of VTF. One problem is that old spring loaded controls can be way off. Also, modern stylus profile might require greater AS. The Wally Tractor sounds like a cool device. Sighting from the front at different positions on the record is also effective. Looking at output levels on an electronic device is good. Because there is no perfect setting for all occasions, I try to find a position that sounds centered with a mono female vocal with a small band behind her. This is like my normal fare only I don't listen to all that many vocals. I can't help but to sight the cart from the front. If you can get in that position you'll be amazed at what you'll see. With even lighting and being directly in front, the angle of the cantilever in relation to the cart body is obvious. Do this at three places on the record and it will get you 90% of the "perfect" setting. May the anti-farce be with you. Sorry.
Regards, |
Dear Fleib, I love you, but you have forced me to get even more pedantic than I have already been. There CANNOT be ANY points on the arc traversed by the stylus wherein the (pivoted) tonearm is perfectly tangent to the groove, and here is why:
When the tonearm/stylus is tangent to the groove it must also be perpendicular to the radius of the LP. Correct so far? When that condition pertains, then a line from the pivot to the spindle (the P2S distance) must also constitute the hypotenuse of a right-angle triangle. OK? When or if that is ever the case, then said right angle triangle must conform to the Pythagorean theorem: a-squared + b-squared = c-squared, where "a" is the tonearm effective length, "b" is the distance from the stylus tip to the spindle, and "c", the hypotenuse, is the P2S distance. Well, we already know that all conventional pivoted tonearms are installed such that there is stylus OVERHANG, which must mean that "b" in our equation is always greater than "c". Thus the Pythagorean Theorem can never be satisfied. Ergo, tangency never happens. Which is why we always have a skating force. I can go on to explain the direction of the vector of the skating force, if you like. But it's easier to do that with vector diagrams, which are not possible here.
Also, I say again, the term "centripetal force" is naught but a description of a particular kind of force. In a way, you are correct when you say that there is no centripetal force on a stylus. The force that is generated due to the geometry is actually always at an angle that points more or less to the left rear of the turntable starting at the stylus tip, not to the spindle. But the stylus cannot move in that direction due to the mechanical stiffness of the tonearm, so the force vector gets expressed in the only possible direction for the stylus to move, which is inward toward the spindle via rotation of the tonearm on its pivot.
Timeltel said it first in its simplest form: "Skating force is due to stylus overhang", or words to that effect. It took a few days to dawn on me why that is correct. |
Regards, Pryso: Skating force is relevant to the audiophiles position. ;)
Before Lew explodes: First, the speed of a revolving object is greatest at the outside perimeter. If the rpms are constant, velocity as measured in inches per second (ips) decreases as the center is approached. Stylus friction, groove modulation, skating & ALL the relevant etc.'s are contingent to ips's.
As it applies to our concerns, let's change some of the parameters. We'll tie the end of a rope to a point anchored outside the rim of a merry-go-round. Imagine that our volunteer audiophile has given us just enough rope to hang him, err, to sit him, harnessed to the other end of the rope just past the capstan of said ride, now give it a clockwise spin. If he is facing the outboard anchor he will be subject to forces from two vectors. The first (from his perspective) will be from front to back. The consequence is a tensioning of the rope. The second will be coincidental to the fact that his position is somewhat past the capstan. As the ride's platform continues around in its rotation there will also be an additional influence, this from his right to left. In this case there is a lateral force originating from his right, as the platform slips beneath him he will be drawn left towards the center capstan. As this occurs and due to the reduction of the platform's inches per second of travel as he is drawn closer to the capstan, the influence of this lateral, or centripetal, force will be progressively reduced.
Peace, |
Lewm,
Your Pythagorean theorem explanation seems flawed to me. If the cartridge is twisted relative to the tonearm then this explanation is irrelevant. If we assume the diamond is correctly alligned in the body, and the cartridge is angled to provide no tracking error at one or two points then a "tangency" can exist at one or two points.
In other words you can achieve tangency at at least one point without a right angle triangle existing as long as you can draw a perpendicular line across the stylus and hit the centre of the spindle. |
All my statement on manufacturers attempting to do as if i understand correctly with my AS research is the attempt is to add AS gradually as the cartridge tracks the grooves to its end. I cant and should not have vouched for triplaner being in that number until i get the wiring artificial AS resolved. But as for my micro the visual proof that i can see with my own eyes clearly shows increase in AS at the beginning middle and end of an lp.
Im not real sure if theres a mathematical phenomenon that can explain this reality. But if there is im sure you will read it here first.
Its a real good day in my neighborhood cause i finally has a true grip on AS. Its a good thing and contrerary to past knowledge here needed for superior playback and sound.
Mike |
Headshell offset does allow for tangency at two points across the LP surface. Flieb said that, and I agree with that. It was my error not to include that in the analysis. My model would predict that at those two points, there is no skating force. My explanation was incomplete but not wrong per se. I should have said "a straight line from the pivot to the stylus tip" is side a in the Pythagorean Theorem model, and is never tangent to the groove. Dover, tangency would always occur at TWO points on the LP surface, if the cartridge is properly aligned according to any of the conventional algorithms. You can't do better than that.
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Lew, IMO the most elegant and concise description already supplied by J Carr:
**What causes skating forces is the fact that, with offset-angle tonearms, the LP groove pulls the stylus in two vectors at once. One vector is from the stylus to the tonearm pivot. The second vector is along the offset angle.
These two vectors synthesize to produce a third vector that pulls the stylus inwards, toward the platter bearing. It is this third, synthesized vector that we call "skating force" or "side force".
Since skating forces are comprised of the drag on the stylus from the LP groove, they vary depending on stylus profile and groove cutting levels, and from what I have seen, the skating forces also vary according to the instantaneous groove radius. (If you can find an Orsonic SG-1 "Tonearm Side Force Checker" it will allow you to plot the curves).
If I recall correctly, if you can manage to cancel out the groove amplitude-dependency component (by using a constant-amplitude test LP), the side force curve ends up looking fairly similar to the tracking error curve for the particular tonearm alignment that you have chosen.**
I think offset and not overhang is the cause. If the offset is 23 degrees, wouldn't the arm be tangent when it gets 23 degrees away from the null? (not that it matters) If you offset a cart on an arm with no overhang, there would still be skating.
I think we can agree that skating exists, regardless of theory. We all agree that it's friction pulling the stylus in 2 directions at once? Both those directions are away from the pivot or stylus, not exactly toward the spindle.
Regards, |
correction: I should have said, Both those directions are away from the pivot or cantilever line, not exactly toward the spindle. |
In my scheme, the actual force generated due to friction between stylus and groove and the lack of tangency of the stylus tip to the groove (at all but two points on its arc across the LP), has a vector that is constantly changing in magnitude and direction, but the direction is always somewhere between the line drawn from the stylus tip to the spindle and a line drawn from the tonearm pivot to the stylus tip. The skate force vector is always directed away from the stylus (as you say) toward an ever-changing point within those two confines. However the stylus cannot move in that actual ever-changing direction, because the mechanical stiffness of the tonearm prevents it. Instead, the stylus moves or can move only toward the spindle, along its permitted arc, as determined by the location of the tonearm pivot. A lot of words, but precise language is necessary.
I think Timeltel (or you) was contending that this is not a true centripetal force, and I now agree. Its origin is not that of a true centripetal force as described in Newtonian mechanics. (Gravity holding a planet in orbit around the sun, for example.) |
Lew, The basic vector is tangent to the groove in a clockwise direction. This is further complicated by the pivot/offset angle thing. Please read the last paragraph under Arm Systems (below). I think that's it in a nutshell. Beyond that you'll have to consult your friendly neighborhood physicist. Further than this is beyond my current understanding. Maybe the Prof can enlighten us further. I don't know. At this point I'm more interested in results, measurements, and techniques for optimising sound.
http://en.wikipedia.org/wiki/Phonograph#Arm_systems
Regards, |
Regards, Fleib: Copy/paste from your friends as Wikipedia: "a force which keeps a body moving with a uniform speed along a circular path and is directed along the radius towards the centre. Isaac Newton's description was: "A centripetal force is that by which bodies are drawn or impelled, or in any way tend, towards a point as to a centre."
From Vince Calder, an educator with the Argonne National Laboratory: " When the trajectory of an object travels on a closed path about a point -- either circular or elliptical -- it does so because there is a force pulling the object in the direction of that point. That force is defined as the CENTRIPETAL force. It has not been more simply, or directly stated than by one Isaac Newton in his famous "Principia": ("IN ANY WAY tend, towards a point as to a centre). ""The term CENRTIFUGAL force appears to have come about because of a mistaken perception that there is a force that operates in the opposite direction as the CENTRIPETAL force. But that is a misconception. The "pull" is the force that has to be applied toward the center."
If a screw and a suitable material are turned in opposite directions, the threads will draw it into the material. The size of the screw, the constituency of the material, or wether the screw is held stationary while the material is turned against it makes no difference, the principle is constant.
An arm with added overhang will travel towards the center. An arm with zero overhang will encounter equal opposing forces at the spindle, it's movement will stop when that condition is achieved. An arm with negative overhang will tend towards the rim, it responds to centrifugal force. In the most elementary terms, regardless of size, shape or the nature of constraint, if an object is placed on a rotating surface, it will move inwards, outwards, or reach a state of balance at some point in-between.
The discussion is tending towards unproductive quibbling over terminology. To say that the observable phenomena of skating is subject to the influence of various vectors is not inaccurate, to state that by definition the concept of centripetal force encompasses those descriptions is also true.
A thing either is, or it is not. Adding qualifiers (planet) to the time honored definition is somewhat like the lady's assertion that she was "almost a virgin".
Ya'll carry on.
Peace, |
Timeltel, I said I wasn't sure about CENTRIPETAL force. I still don't see tangency or lack of, as causing skating. Must you be so emphatic?
I'm done with this. Please address further comments on this subject to someone else.
fleib |
Fleib, The "basic vector", if you refer to the torque (i.e., angular force) of the turntable motor that is applied to the LP grooves, is indeed in the clockwise direction. But the force that causes skating is the friction between the stylus and the groove walls, which must always be in the exact opposite direction from the motor torque vector, i.e., anti-clockwise. The friction force opposes the motor force, IOW. The work done on the stylus tip by the motor via the groove interface is dissipated as heating of the groove walls.
I am going to bow out of discussing this subject further here, because it is probably boring to others, but if anyone wants to discuss it further via email, I am happy to do so. |
Lewm, Timeltel, Fleib, et al
Why not start a separate thread or continue and existing one rather than drop the subject?
There is so much misunderstanding around this subject and, I am sure, so much still to learn regarding why it causes so much disagreement as to the physical versus perceived aspects. And that can only happen when the issues are discussed and argued out.
I have my views on the subject, and they have changed as time has gone on. I have to say, though, that the basic principles and causes were well known long ago and they haven't changed.
What is interesting is why some consider that skating forces do not need to be compensated for, because the corollary is that one side of the groove has less VTF than the other.
John
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"address further comments on this subject to someone else."
Oh no, Fleib, that's not how it works. An open forum, I'll address whom I please. However, it might be best to not address further comments to the other on any subject. No noob here, tired of snide remarks, your call.
Sheesh.
(All else, apologies, and of course,)
Peace, |
John, Timeltel and I were discussing the issue you bring up just today by private email. Send me a contact, and I will try to respond to your last sentence. I have a new take on why it is possible that for some tonearms and some cartridges and probably "some" music, use of AS may not be needed, as many good listeners do report. |
There are 'theoretical'- and there are 'practical' reasons.
The old Kant wrote two separat books about that. For the
most of us the practical issue is the only relevant one for
the obvious, uh, reason. We are not able to participate in the theoretical dispute. However from the theoretical dispute we can deduce that not much help is to be expected
from the theoretical guys. Do it yourself or trial and error method is what we should continue to do.
Regards, |
Hello Nikola,
Would you not agree that once a practical experiment takes place, some sort of theoretical position must follow? This must be the case for all of us to some extent unless the next experiment is carried out on a purely random basis.
And that theoretical position then informs the practical.
Regards,
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Lewm,
I would like to read your ideas, but I can't seem to find away to email you via this site. Age is telling.
If you like, you can reverse the situation and email me, or contact me through the odyssey tonearm blog.
John |
