Thuchan, I didn't say you, personally, accepted everything Dertonarm said. I was making a general point. I am always willing to discuss things, and admit when I'm wrong, the operative words being "discuss" and " wrong". you said The (analogue) world is like it is, some good developers and failed ones.
Mostly the failing guys do have a motivation to define the world and tell the succesful developers what they seem to have done in a wrong way.
believe me, I do know producers of tonearms and even turntables who do understand the theoretical implications of proper alignment but they do not really care about it. Success or failure in hifi and good and bad developers do not necessarily correlate. Making money from a product doesn't mean it is good, merely that a lot of people buy it, and vice versa. My, and many other's, experience is that often a good product can fail because someone who can influence the market decides it should fail - it's all part of the way markets work... probably best to stay out of it (or, vice versa, as given by your example above,...!) J |
Dertonarm Glad to see you have responded to my post (via T Bone). Why did you do that? I am willing to discuss the SME issue directly. You said Given the fact that the mounting hole in the SME V is not really intended to allow anything like a "cartridge offset angle" (which in tonearm geometry not really exists at all - other as by wishful thinking)... please read my post to Peter re the conflation of headshell and offset angles and why this is confusing.I am assuming you mean cartridge mounting. ...one can assume that it's designer did so by good reason... That is a fair assumption, but only if you give a fair analysis of why they might have done it that way. ...As this mounting hole is (to the regret of many of it's owners past and present - including me ..) not really an elongated one either... Patently not, given it has no slots. Why would this be? ...the effective length is - at least in theory and designer's intention - pre-determined as well... No. The alignment chosen, ie Baerwald/LofgrenA IEC, is predetermined. The effective length is nominal. ...Setting the "cartridge offset angle" other than the offset angle of the tonearm's headshell does produce an additional break-down torque in the tonearm's static model - i.e. an additional force vector.
This is a plain mechanical fact - thanks to Isaac N. ...;-) .... This is vague. What do you mean by "break down torque" and why would it be additional if the overhang remains the same? The stylus merely rotates, the groove tangent remains the same, therefore the vector towards the centre remains the same. The only change could be due to the stylus, which may or may not increase the force along the groove tangent depending on the stylus profile. (re Issac Newton - I have heard he had a great hifi, but maybe Einstein's was better on the super fast transients... (just a joke)) That additional break-down torque does of course influence the skating force. In what way, by how much? Now you get to the point: Now is the SME V designed and constructed strictly following Löfgren A IEC (Baerwald)?
According to it's designer's it is.
According to it's technical parameters it is too.
Can one adapt the SME V to different alignments by moving its slide carriage? It was not intended to adapt to different alignments, but to different position of stylus relative to the mounting hole of the SME V. Granted, though Lofgren B IEC is much easier than with a slotted headshell - no need to loosen the cartridge, just slide the base. ...The moving of the SME carriage does alter P2S and adapt's the effective length to different distances - in cartridges - between the mounting hole and the stylus. Correct Thus being able to retain the original Löfgren A IEC alignment is was calculated to. Thank you for agreeing. But why not just say you were wrong, or had expressed yourself badly, previously? As Piet Hein, the Danish scientist/philosopher/poet said: The road to wisdom?
Well, it's plain
And simple to express:
Err
And err
And err again
But less
And less
And less. |
Dear Daniel, for second time in this thread you state :
+++[ "Setting the "cartridge offset angle" other than the offset angle of the tonearm's headshell does produce an additional break-down torque in the tonearm's static model - i.e. an additional force vector.
This is a plain mechanical fact - thanks to Isaac N. ...;-) ....
That additional break-down torque does of course influence the skating force." ]+++
I'm sorry for I'm not in a deep embarrassed position and have the nerve to ask you about such widely known physics.
I have a question for you (and it is a genuine one, due to my ignorance) :
The Talea, Schroeder, Clearaudio Satisfy are designed with adjustable arc on their rudimentary headshell. The Simon Yorke has circular headshell which does not shows any preference in cartridge angle. Moreover, there are some circular cartridge bodies also! How does the Newton's law applies there?
The antiskating force is always an adjustable issue and in no way the value of it can determine a fault on design. The fact that most of tonearm designs can not provide this feature by the right way, thus gradually increasing antiskating force, it does not giving the wright to anyone to acuse the cartridge's twisting on headshell.
Please tell me what I'm missing ? The cartridge is always slaved by the arm which is slaved by it's pivot point, so, there is no any relationship with cars moving freely on a road and are coming to take a close turn while having 100m/h
I'm sorry for asking but I really want to know better.
Thank you in advance.
George |
Dear George, that now is a question/comment worth being addressed.
The Talea, Schroeder, Clearaudio, SY and before them other tonearm designs ( Well Tempered et al) did use this smart trick for good reason.
By this design feature they avoid a pre-determined offset angle and thus are much easier to adapt to different alignments (calculations) without trade-offs due to the alternation of a "pre-determined" offset angle by a cartridge's body aligned in a different angle.
Circular bodies further reduce the problem, but - unless they follow the Ikeda or DECCA/London cantilever-less principle - there is still the line of the cantilever which should be in line with the offset angle.
If we have a cartridge body other than circular, the problem get's worse and if the cartridge's body and its cantilever aren't in line with the headshell's offset angle, we will get another force vector - i.e. a second breakdown torque and thus an alternation (not necessarily an increase!) of the skating force the tonearm can ( NOT must!) apply to the stylus/groove contact.
Before I address your statement regarding skating force and "anti-skating", please clarify what you think skating force is and where it comes from.
There are a very few pivot tonearms out there with apply practically zero skating force to the stylus.
Cheers,
D. |
"There are a very few pivot tonearms out there with apply practically zero skating force to the stylus."
Why are you mention this? Are they having an advantage over the rest tonearms? I thought that as the friction increases towards the center of the LP, we can not assume the skating force as a constant value and so, we must apply an increasingly antiskating force anyway. I'm I get it wrong? |
I spent an afternoon with the Uni-Pro.
The following is my own impression and opinion:
The Uni-Pro came packaged very very well. All parts were in protective pouches, etc. The PDF manual is excellent. Easy to read and follow.
I initially took a gander at my LPs and found most were not even IEC standard and the grooves ended well before. So I chose Lofgren IEC template to start.
The set up of the Uni-Pro is very simple and the build quality is top notch. I felt great to having this tool to use.
The set up using the Lofgren IEC template with the Uni-Pro was the easiest of all my jigs and protractors. The 10x loupe positioned perfectly and I was able to really see the cantilever in relation to the alignment lines. The parallax lines really help out to know that your head position is correct. So much easier than the Mint with the supplied 10x loupe which can roll easily and hit your cartridge. With the Uni-Pro loupe, it was a cinch to know for sure. It allowed for me to really see the cantilever of my Grado Statement1 which I was not able to do with Mint loupe.
The Uni-Pro also comes with nice extras like LED light which came in handy, ruler to measure P2S distance, and other goodies. Even gloves for the super obsessive! Great, as I am a bit of that.
I will try Daniel's VPI 10.5i template next and then try the Baerwarld IEC as well. To note, I did not like the sound of Lofgren IEC and reset my cartridge to VPI's own jig which has a sweeter timbre and less harshness on grand pianos. So it makes me realize Harry at VPI knows what he's doing although some here seems to consider his methods suspect.
Finally, I am not a tone arm physicist or anything like that. I am just musician and also a recording engineer who work with my ears daily musically since I was 2 years old.
Is Uni-Pro worth the 700 bucks? That would be up to the individual and their wallet. For me, it was a great purchase as it makes setting up my cartridge so much easier with no fuss. So a yes for me but I am in NYC where a nice evening out with your date can cost a grand... |
Dear Daniel, I promise I'll stop to tease you with so much out of topic queries any more. I've just figured out that is worthless, as it seems you avoid to answer anyway. Not that you are obliged to do that of course.
(ie): the "alternation of the skating force the tonearm can apply to the stylus/groove contact" that resulted by the twisting of the cartridge to the headshell, it does not seems a downside to me. And this is coming logically once the skating force isn't constant, we have to apply an antiskating force even to those pivoted tonearms that "apply practically zero skating force to the stylus" in order to fight this force across the whole length of the record groovies. So, it seems a neccessity and also inevitable to me as long as it is depended by the cartridge & the groovies also and not only by the tonearm. Now according to this logic, once that we have to integrate an antiskate mechanism to the tonearm, I can't see why the value of it could be in any way an indication of the tonearm's quality. We just have to apply more to those tonearms that carring a "twisted"?! cartridge on their headshells.
I'm really sorry but I just can't follow your replies, as in your posts it is impossible for me to find anything like an advice or a suggestion, no matter what the question is. I'm sure it must be a comprehension issue due to the combination of my bad English and my sciolism and so, I'm stopping right here with my apologies. Anyway thank you for your patience and your ability to stay calm with me for so long. |
T Bone I take on board all your points, and, as it happens, I agree with Dertonarm on some points. I just wish he would stop obfuscating and avoiding admitting he has completely missed the point on others. Regarding reasons for different weighting, check out Keith Howard's piece in the features/reference section http://www.stereophile.com You said you couldn't get the numbers to match and something had to give. Something always does. In this case, the theoretical world. I never saw the point of giving numbers which were impractical for set up. Thirty years ago, no one set their tracking angle and the rest, to three decimals.No one does today. The numbers were rounded up for a nominal effective length of 230. The important word is "nominal". I should have perhaps laboured the point more, but that was back when tonearm geometry was perhaps better understood, and the issues concerning the choice of design - sliding vs fixed pivot, slots versus holes etc, were better appreciated. How are you doing with the SME (or rather, sliding base) geometry? I'm going to post an explanation separately. You said Your point about 'just adjust angle and mounting distance as necessary' is EXACTLY right and appropriate given the imperfections we each bring to the table when we mount a tonearm/cart, but that is the art, not the science (and most of the critiques of Dertonarm's ideas and protractor on this thread are on the science, not the art, of tonearm setup, and his product I would think is specifically addressing ease of getting the art right - because the science is gotten right by anyone who gets the algebra right). If his device makes setting up easier I'm all for it, but not if it is less accurate. That was my reason for posting originally. He doesn't say what the accuracy of his device is, compared, for example, to a paper two point. Now I don't know how accurate a paper two point is, but I do know it is more accurate than the easier one point - two nulls are always better than one, as they allow an obvious a way of double checking. And in any case, as Dertonarm has said in the past:
But the alignment of the zero (points) is the raw basic on which everything else builds.
So, adding an arc in addition should certainly make it easier to set up (for a specific effective length) as the arc and the nulls must intersect, thus giving two opportunities to check offset. I don't have a problem with that, I think it is a good idea. If it is easier, great, fine, but is it more accurate...? Hopefully, if not DerT, then someone will tell us. J |
Jazzgene
Thanks for your comments. I find them helpful and illustrative.
|
John,
I have read the Howard piece (assuming you mean 'Arc Angles'), which I think is an appropriate intro to the subject for many people. His brief points on weightings are interesting but, they just aim at the idea, and go nowhere with it. The last time I dug around in the Stevenson articles, I did not fully understand where some of the assumptions had come from, and I remember being bothered by one in particular (stylus to 'turntable pivot distance'). I assume it is in the Baerwald so I'll have to go back and actually spend some time digging in the formulae. |
I agree that accuracy is very important and should not be sacrificed by ease of use.
I'll set up using Uni-Pro's Baerwarld IEC and then recheck with my Mint protractor which is also Baerwald IEC and see if they are spot on or any differences. |
Geoch As Dertonarm has avoided the issue yet again, (he only seems to respond to posts on which he feels he can appear to be right) and (if your question was genuine and not to provoke) perhaps I can help. You said I have a question for you (and it is a genuine one, due to my ignorance) :
The Talea, Schroeder, Clearaudio Satisfy are designed with adjustable arc on their rudimentary headshell. The Simon Yorke has circular headshell which does not shows any preference in cartridge angle. Moreover, there are some circular cartridge bodies also! How does the Newton's law applies there? Newton (the famous hifi enthusiast), said that to all forces there is an equal and opposite reaction.Bear with me if you are familiar with the following, but I will say it for those that are not. The friction of the stylus against the moving groove causes a force which is aligned along the groove and reacts against the arm mount. The resultant would pull the arm inwards and out of the groove, were it not for a force reacting against it, so a counter force needs to be applied in some fashion. VTF supplies some of this force and the remainder usually as an antiskate device of some sort near the pivot. As you correctly state, Geoch, this force has to increase as the arm approaches the centre, because, while the overhang is constant, the radius decreases, therefore the inward force varies in proportion. All good arms have antiskate/bias, adjustable in amount and in degree. Longer arms need less antiskate, as they have less overhang. (There are arms with zero or negative overhang (underhang). These have very small skating forces, but, unless fitted with a mechanism to maintain the cartridge parallel to the groove, will have large tracking errors.) Whether a cartridge is cylindrical, cuboid, flower-shaped or whatever, is neither here nor there. It does not affect antiskate if correctly mounted. The bottom line is that there is only a vector towards the pivot from the stylus, and a vector from the stylus along the groove, These result in an inward rotation of the arm. It has nothing to do with cartridge offset angles, except inasmuch as the stylus contributes more or less to the frictional force along the groove, (eg elliptical versus conical) and certainly nothing to do with the cartridge body shape. I could explain further, but for now that is enough. So, the question of round headshells, rotating headshells is all baloney in terms of antiskate. The arms DT mentions may well not have a specified offset and therefore provide a facility for adjusting whatever offset is desired, which is a good thing (although the way they do it doesn't look as smart to me as he seems to see it, as none of them apply the rotation at or around the stylus where it would be most useful (and where, should I ever (no! no!) design another tonearm, put it - (there's a hint for DT if he's designing an arm...god forbid) Other stuff: About weird shaped cartridges (in my opinion the result of designers /stylists who have more interest in being different, than in good, practical functional design) Dert says they avoid a pre-determined offset angle and thus are much easier to adapt to different alignments (calculations) without trade-offs due to the alternation of a "pre-determined" offset angle by a cartridge's body aligned in a different angle. Well, he would say that, given his commitment to arc protractors: the more weird shapes there are, the harder it is to align using anything else. Cartridge manufacturers must be rubbing their hands at the prospect of being able to mount generators and cantilevers any old way... Dertonarm says Circular bodies further reduce the problem, which problem? he doesn't say, for it isn't antiskate. but - unless they follow the Ikeda or DECCA/London cantilever-less principle - there is still the line of the cantilever which should be in line with the offset angle. I hope every reader out there (with a Decca (or otherwise)) sees this error for what it is. The Decca does not have a cantilever in the accepted sense, but has the equivalent nevertheless - the armature - it is just not visible. So it must be aligned like any other cartridge. If it wasn't cantilevered one could mount it reversed - try that with your client's Decca, Dertonarm, and you'll probably get a slap round the ear for being so stupid... Also when we talk about cartridge offset angle, that term is usually accepted as encompassing the generator, cantilever and stylus, which ideally should all be in line. Errors here are an issue for cartridge designers and manufacturers. By all means line up to a cantilever, but that doesn't mean either the generator or stylus are lined up with the cantilever. Geoch, Dertonarm shows his ignorance and arrogance by his response to you. Instead of explaining something he asks you for your ideas, perhaps because he is not truly clear in his thinking, as in the case of SME arms. I realise your wisdom in avoiding getting too involved, but avoidance of bullying, for that is what it is, can lead to unwanted and unpleasant consequences, both here, in a small way, and, in the greater world, in a big way. |
Dear Jazzgene,
wow, did not know you are in the professional music field. great! i just received "The Recordings Of The Beatles" . You get a feeling how enthusiastic and technical advised those engineers were in these days. Long forgotten. Therefore the quality of many products of today are somehow ... I received the manual yesterday and I do think it is very helpful. Not many developers take care as Dertonarm did. On the other hand for such a product it might be absolutly mandatory.
I remember tonearm developers not being able to produce some good words on their own product. nevertheless not every developer needs to be a good marketing guy of course.
I received my EMT JPA66 and I am playing around a little with my FR-66s arms. Good to have a Uni-Protractor when you need to change carts. IMHO The discussion in this thread goes a little backwards and many positions are repeated. I would like to hear some critics or experiences others have with the tool.
Best & Fun Only -Thuchan |
@John,
You state all good tonearmas have anti-skating. The VPI 12.7 and 10.5i does not. Are they bad tonearms from your experience? The 10.5i sounds really good to me. I did try the VPI after market anti-skating and it made the sound worse. So I went back to what Harry recommends which is to not use any anti-skating with the 10.5i arm. The music sounds much better this way to me.
Certainly sounds better than my Thorens table which has anti-skating. |
Jazzgene,
I have not heard your arm, but if you tell me it's a good arm and you prefer it without antiskate, I believe you.
From the manual it appears that VPI recommend using a higher tracking force than might be otherwise used. In my post I mentioned that downforce contributes to antiskate.
That the wiring can supply some antiskate, depending on how it is dressed, is mentioned too, in the manual. I don't know if you use this procedure, but these are methods of counteracting the skating force, without a specific antiskate device, so in that sense the arm has the means to do it, but you can choose not to use it, as with any arm.
Being longer than a 9" helps to an extent and the specific construction of the arm, being a unipivot, might lead to compensating forces in the rotational mode. The skating force is always present, though.
But if all the above mentioned things together mean you can do without a dedicated mechanical device to supply the antiskate, (spring/ string and weight etc), then that's a good thing, and the designer is to be commended.
|
@John,
Yes, Harry says in the manual that with every tonearm he's heard, it sounded better without anti-skate and heavier VTF.
The twisting of the cable is a bit "hit and miss". I tried it with a test record and whichever way I twisted it, it increased distortion on the same channel (left). With my oscilloscope and headphones, I confirmed it was the best without any twist in the arm cable. Without a twist, the arm and cartridge (Grado Statement1) tracked perfectly.
Grado recommended 1.7g vtf with the Statement1. I went with 1.8g but in the end, to my ears, 1.9g sounded the best so that is where it is now. Also some damping fluid for the pivot.
Thanks for you response. |
Dear Jazzgene,
regarding Antiskating I had the VPI Memorial 12" tonearm and it's a pretty clever construction compensating by the wire. Harry is fully correct, Antiskating is mostly overrated. This has led to extensive usage by tonearm users damaging the carts over years. I am very careful with used carts cause many show signs of desorientation.
best & fun only - Thuchan |
Jazzgene, You said ...Harry says in the manual that with every tonearm he's heard, it sounded better without anti-skate and heavier VTF. Perhaps so, but there can be issues with this method depending on the cartridge. The bottom line is that there is a force which tries to rotate the arm inwards and it is a consequence of pivoted arms. It's not my opinion - it's the way it is. The issue is what to do with the fact of it. That then becomes a matter of choice and preference for the designer and the user. |
Dear John,
You said "this force (antiskate) has to increase as the arm approaches the center." How about from the outermost of the lp toward the center? How should the antiskate work for a pivot designed tonearm ?
Apologies to the original poster Downunder, but I think this is the best kept secret in analogue.
Regards, |
Dear Jazzgene, dear Thuchan, dear Mesael, please allow me to briefly bring some "certainty" into this "vague" topic "anti-skating".
Gene and Thuchan - your observations regarding the VPI and SAEC tonearms are correct and backed by physic.
A brief summary of skating - it's whereabouts and effects in analog audio.
The notorious "skating force" is a result of the friction in the inner groove wall in conjunction - and this is the very important point now ! - with the offset angle of the pivot tonearm, the stylus' contact area's shape and the VTF.
It is an un-linear force by nature ( in a given set-up with a given cartridge and a singular given pivot tonearm ), as it is in conjunction with the position on the tangential error curve, the distance (= radius of groove wall) towards the inner label and the VTF.
The higher the VTF - the lower the skating force.
The longer the effective length of a given pivot tonearm - resulting in smaller offset angle - the lower the skating force.
The is no skating force in a tangential tonearm at all.
The friction on the inner groove wall is the result of the breakdown torque in a tonearm with an offset angle - a tangential tonearm (at least so far ..) has no offset angle.
If you encounter skating force in a tangential tonearm, then there is a serious misalignment of the tonearm and/or your turntable isn't leveled ( or there is a stream of air aiming at your tonearm .... ).
The breakdown torque in a pivot tonearm is an inevitable force. It can be addressed, but this is rarely done.
To compensate skating force in groove tracking - unlinear by nature - with a linear compensation is futile from the start. Futile in the sense that you fight one evil with another. In most 9" tonearms working with high compliance/low VTF cartridges you will need anti-skating, as this dreadful effect-force is very high here.
A tonearm with 12" (= small offset angle = lower breakdown torque) and with a low compliance cartridge with VTF of 2.5 gr and higher will most likely make anti-skating obsolete. In any case the resulting force is much smaller than with a 9" tonearm and a MM working with 0.8 to 1.5 gr VTF.
Then there are a few tonearm designs whose designers addressed the breakdown torque where it occurred and created tonearms with very low skating force applied to the stylus.
Cheers,
D. |
Dear Mesael, No ide what 'the best kept secret in analoque'
is but to my knowledge only the Sony PUA 237 has an ingenious antiskating construction which 'provide' different force depending on radius. All others have the same force everywhere as far as I know. If my quess is correct than the Sony solution should answer your question
'how should the antiskate work for a pivot arm'.
Regards, |
Dear Thuchan, Jazzgen,
I mounted my 12 JMW memorial on an armpod and set it up on another table on weekend for the Jrs. experiment.
It took all of two minutes no numbers or calculations - I put the cartridge in the VPI tonearm head - nice and straight the way I wanted it to be held - firmed up the bolts.
Then I rotated the JMW arm hinge and the armpod until it lined up perfectly with the VPI jig.
I have found that JMW arm works best for me with no turn of the wire.
Sorry to digress away from the thread theme.
Cheers Chris |
Dear Nandric,
Not so fast. I'll show you examples of tonearms.
Anti-skate from outer grooves toward inner grooves:
Constant : Clearaudio Unify, and simple counterweight
with string
Increases: Clearaudio Satisfy, and those using spring, and
most of magnet design
Decreases : Morsiani.
Here's the link :http://www.morsiani.it/
So, which one is correct or none of the above ?
I'll wait for John. He's a designer,and seems knowledgeable.
Cheers, |
Dear Mesael, Morsiani is right.
He is right in that the skating force get's lower/less towards the inner label - i.e. decreases with decreasing groove radius.
As the contact area towards the inner groove wall decreases with decreasing radius, so does the friction - ergo the related skating force.
So Morsiani's concept does address the problem rather smart.
Cheers,
D. |
Dear Daniel, why don't you get a cup of hot milk and get a good sleep also?
Ooops! I forget. I promised not to ask anything. |
Regards, Mesael: Thanks for the link to "morsiani". The thought of skating forces increasing towards the spindle was not consistent with what little I understand about Newton's concept of centripital force.
Peace, |
DT and Timeltel,
Given the nature of how the tracking angle changes over the course of the record (for any arm), I would expect the skating force to fall on its way inward and then start to rise again as it moves past the peak tracking distortion area between the null points. The changes in friction coefficient (which will, of course, depend on stylus shape) would affect this, as would any changes in VTF as the cart/arm track the record. Different AS methods should actually affect the VTF 'curve' (as a function of groove radius), as should the fact that the VTA/SRA angle will actually start to get steeper on the way back in. Kind of interesting to think about...
I am assuming that one's choice of alignment (or perhaps more particularly, the location on the record of the peak tracking error between the null points) will have some effect on how much skating force ceases to tail off in the last part of the record...
I've just given myself more stuff to muddle through, obviously... |
Dear Timeltel& Mesael, Those are HUGE confusions I should think. On an 'blanco' LP or an LP without grooves one can
observe the acceleration of the arm toward the spindle if no antiskate is used. Ie the centripetal force as Timeltelt stated can be seen in action . The Morisiani story is the opposite one. Ergo it is logicaly as well as physicaly impossible for both to be true. However those
forces should be the basic one for all of us to understand.
Regards, |
@Ct0517
Yes, I find my VPI 10.5i arm to be best without a twist in the cable as well. |
Dear T_bone,
a correct calculated alignment curve - much to my regret ... ;-) ... - has practically almost zero influence on the skating force. Unless the alignment curve is really VERY bad and raises to astronomic values.
Cheers,
D. |
To Jazzgene,
"To note, I did not like the sound of Lofgren IEC and reset my cartridge to VPI's own jig which has a sweeter timbre and less harshness on grand pianos."......
"Is Uni-Pro worth the 700 bucks? That would be up to the individual and their wallet. For me, it was a great purchase as it makes setting up my cartridge so much easier with no fuss. So a yes for me......."
So, you say it's worth the 700 bucks, just to go back to your old original alignment with the supplied jig......
I don't understand that....... |
Dear 04rdking, please read Jazzgene's full post - he did not like Loefgren B IEC (which is a standard calculation ) and will try the special VPI-template supplied with his UNI-Protractor and the Baerwald/Loefgren A instead. It is a choice of alignment-options - not of the alignment instrument.
Cheers,
D. |
@04rdking
It's okay if you don't understand it.
The Uni-Pro allows me to try out different alignments. I just didn't like the Lofgren IEC compared to the VPI. I will try the Baerwald IEC and the VPI specific alignment later this week. Perhaps I'll find one of them preferable to the VPI alignment.
Oh, I also want to add that the Uni-Pro is much more precise than the VPI jig. The VPI jig has a certain amount of play between the jig and the metal piece that moves to contact the pivot base. The parralax effect can throw you off on the vpi jig as well. |
DT,
I would have figured that different alignments altered the shape of the tracking error curve (this is indeed the critique of using a Stevenson vs a Baerwald - that the tracking error curve is "worse" than the Baerwald over the whole of the recrod) and/or tracking angle curves as functions of radius, even if ever so slightly. If they did so, would the skating force curve not change as well? |
Perhaps it might be a good idea to go back to basics. There are two aspects to this issue. One is to acknowledge what the force is and how it originates. Second to see how it manifests itself on a record deck.
While we might call it antiskate, or bias, or whatever, the force which pulls the arm inwards is not specific to tonearms. It can apply in any situation where there are two forces opposing each other.
To illustrate the simple example of a linear tracker. (Those of you with linear trackers can start practising your smug grin.)
Say you hold one end of a short rope. You are the Tonearm bearing. You put a conical blob of blutak in the middle of the rope - the Stylus. Your wife holds the other rope end. She is Friction.
Friction acts on the Stylus by pulling it along the groove in a direction directly opposed to the Tonearm bearing. It reacts by holding on and pulling back. The rope is straight. The Stylus remains unmoving in the middle. As friction moves to the side, Tonearm bearing follows every move (hopefully).
Now a Pivoted arm.
Friction takes a different tack. She pulls at an angle. Tonearm bearing reacts against Friction. It is immovable. It holds on to the Stylus. but the rope wants to straighten, and Stylus will be pulled sideways, unless......
Help arrives. Another pal called VTF, stands on the Stylus. now it's harder for Friction to pull Stylus sideways. Then yet another pal, Antiskate, comes in and pulls the Stylus in a direction which stops the rope straightening, just enough to stop the Stylus moving without pulling it in the opposite direction.....
Ok, this is simplistic, but relevant. First, note that we have no mention of cartridges, only the stylus which is simply the name for a point on our rope. The angle we talk about is the angle formed by a line from pivot to stylus and stylus to groove. Which is not quite the same thing as cartridge offset.
Forget about cartridge offset for the moment and just imagine your arm with no cartridge, just a sewing needle on the end where the stylus would be, and then follow its arc on a record. Follow it beyond the inner groove, beyond the label, beyond the spindle, and out the other side. See how the angle between pivot, needle, and groove changes. Think of the rope story and in what direction the arm will be pulled. The angle changes towards the centre not varying much, but under 7cm radius, the closer to the spindle it gets the greater it becomes, until at 0 it is a right angle..
That is the basis of the antiskate issue. Does it exist as a force. It exists, yes, it definitely does. But why some people prefer no antiskate, that is for them to say. My arms had an antiskate mechanism, using lever and thread, which allowed for varying the force, and the ratio to some extent across the record, or it could be removed completely. But it was not any more sophisticated than that (It could even have been used to apply a reducing force like the Morsiani,though I am not aware anyone ever did, and not a negative antiskate as in their example of the blank disc; I think there's something wrong there.)
It would be possible to design a cam system given different leverages so as better to follow the average variation, though not the instantaneous.
Whether you can adjust for it totally and in every way, I doubt. As there are many other factors involved in the friction calculation. Some people are more sensitive to its effects than others. Personally, I always tried to compensate for it. I was concerned with its effects on imaging, soundstage etc
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Regards, T_bone: If I understand your point then an alignment with zero overhang would result in all relevent forces coming into balance at the spindle, progressively increasing overhang would bring "stasis" at incrementally greater distances from the center?
Peace, |
@John,
I might install the VPI after market Anti-skate weights again just to re-confirm what I heard the first time.
The thing is if the anti-skate force differs from the beginning to the end of an LP, how can a constant weight compensation like the VPI weight on a string work correctly on the entire LP? It can't, I would think. |
Dear T_bone, yes, different alignments do alter the shape of the tracking error curve. However - it is always a bundle of effects which you can't actually isolate from each other and their dependences. The more "flat" a tracking error curve becomes, - it goes hand-in-hand with longer effective length and less offset angle. All these do influence the skating force. A zero offset angle (tonearm and cartridge body ..) would result in zero breakdown torque and thus any remaining skating would just be a function of friction due to contact area size. That would diminish even further with increased VTF. But even in a zero tracking error point - i.e. "null point" (strange blend of german and english here..;-) ... ) there is still the breakdown torque of the tonearm itself as the ever dominant source for skating.
You are right - a skating force "curve" across a record's groove will never be linear. Not with a pivot tonearm ( not even with the Thales).
The groove's radii change - so does the friction on the inner groove's wall. The tracking error decreases and 2 times and increases 2 times during the groove.
IMHO the most suitable way to handle this practically was always the same: - 12" tonearm w/low offset angle, low compliance cartridge with high VTF, lateral balanced pivot tonearm.
In other words - all measures taken to minimize breakdown torque so to minimize the evil at the source. Better to minimize skating to a value negligible then to fight a constant war with lots of friendly fire (anti-skating...) and no aspect to win.
That way of mine does of course limit the choice of cartridges and tonearms.
As my prime choices in both categories do however qualify in all points to this schemata I am kind of lucky..... ;-) ...
In any case - it is a path as suitable as some other.
It just suits my personal way of addressing problems at the source rather then seek painful cures for situations which have already evolved way past practical solutions.
Cheers,
D. |
Dear John,
You didn't answer my question, or might missed it. How should anti-skate work in a pivot designed tonearm ?
From outer groves to inner groves :
1. decreasing
2. increasing
3. decreasing then increasing
Or none of the above.
Regards, |
Mesael Sorry. I said The angle changes towards the centre not varying much, but under 7cm radius, the closer to the spindle it gets, the greater it becomes, until at 0 it is a right angle.. What this means is that the inward force trying to rotate the arm stays more or less constant within a few percent reducing slightly following the tracking error curve of the arm (not the tracking distortion curve) which varies across the record. Depending on the overhang used and the arm effective length, at the inner null the force starts to increase rapidly. So it would appear that the ideal would be to follow this curve, reducing slightly then increasing. However, it has been shown that there are other factors which increase the friction force as the radius decreases, which would skew this result and make it more likely that the force should at least be constant then increase, or even gradually increase all the way across the record When I designed my arm that's what I did, as I thought that, like tracking distortion it seemed to be worse towards the inner grooves, and less of an issue further out, and should be weighted that way. But it was all "suck it and see". So, really, a tonearm should perhaps give the user the option of trying different things. The actual amount of antiskate needed is very much dependent on stylus profile and downforce. With enough downforce the stylus will never meet a modulation large enough for it to lose contact with the outside wall, or even throw it up out of the groove. However there will still be unequal forces on each side of the groove unless there is some kind of compensation. As Dertonarm says, a longer arm has less skating force than a shorter one. But it is still there, and it has to be dealt with somehow - you can't just sweep it under the mat.... |
Dear John,
Thanks for your response, I appreciates. |
Hi John_Gordon, like it what you you said: we can`t just sweep it under the mat... this is also the case regarding precision! we don`t like to listen under the mat and you don`t do it too.
Best & Fun Only - Thuchan |
Dear Mesal, John stated (04-11-11) 'It would be possible to
to design a cam system given different leverages so as better to follow the average variation...' Well this was
the Sony solution as I mentioned before. One get the impression that the issue is rather avoided then solved by
adding more(confusing) variables. But looking to the actual constructions of the antiskate mechanism one can conclude that not much thought is implemented. And those are all mechanical issues that can be measured as well as covered by Newton. Or so I thought.
Regards,
Regards, |
Jazzgene you said The thing is if the anti-skate force differs from the beginning to the end of an LP, how can a constant weight compensation like the VPI weight on a string work correctly on the entire LP? It can't, I would think. If your antiskate is the JMW 9 then the force will increase as the arm moves towards the centre if the little arm with the weight is horizontal when the arm reaches the run out. if it is literally a weight on a string, like the old SME, it can aso be set to apply an increasing or reducing force depending on the angle it makes with the arm, though this doesn't apply if the string run round the diameter of the pillar and the radius it is acting at doesn't change. Check the output wire and make sure it is not counteracting or adding to the antiskate. You can use headphones and a test record to check for distortion on one channel more than the other. If it distorts on the right, you need more antiskate.If the left, less. If it still distorts on the left with no antiskate, the wire is pulling outwards. Using a greater VTF stops the distortion by nailing the stylus in the groove, but it also increases the skating force because friction is proportional to VTF. If this was not so, our cars would go faster as the braking force increased... |
Thuchan
I often sweep things under the mat.... Most people probably do too. Especially the hard things, like precision in areas where it is hard to be accurate or measure reliably - antiskate is one, and, for me, setting cartridge offset is another.
I was playing with an angle protractor this evening and trying to see how repeatably I could measure an angle. Where it was possible to physically set the protractor against both objects it was easy, but by eye maybe within 0.5 degrees.... that is one place we need precision.
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Dear Jazzgene, serving as the advocate of mechanics here let me briefly add that skating force does NOT increase with increased VTF.
Why so - since friction is of course direct related to pressure (here: VTF) ?
Because the friction increases on both groove walls - thus the relation of the side-wards pulling skating force to the downforce becomes less ( for those preferring the illustrative real-life picture: the resulting force of "your" sidewards pulling "wife" ( mine rather pulls on the same end of the rope as me .... ) becomes ever less dominant the higher the pressure of your "friend" nailing down the stylus .....).
Not my idea - it's simply mechanics here on our planet under the dreadful influence of gravity.
That's why in general skating force becomes negligible with very high VTF (talk about Ortofon and old SPU's running with 4 - 5 gr. VTF).
If you draw a force vector diagram it will nicely illustrate the point.
The skating force is a product of several sources.
However - the portion which starts it all comes from the breakdown torque of the offset angle.
That's the reason why pivot tonearms with full lateral balance ( direct addressing the static breakdown torque where it originates) and long effective length ( = smaller offset angle ) do display less skating force to start with. Now add higher VTF and the skating force - as a resulting force relative to forces aiming in different directions - becomes less and less with increased VTF.
In contrary this the reason why 9" tonearms working with low VTF and high compliance MMs do of course need anti-skating to address a problem VERY dominant in their particular situation.
Skating force in analog playback is diametral inverse to VTF.
No question about it, - anti-skating is desperately needed with shorter tonearms running with high compliance/low VTF cartridges. Here it resulting side-force is comparatively strong.
Influenced by many parameters all working to add to the skating force.
A longer effective length tonearm with ever smaller offset working with low compliance cartridge and high VTF is the exact opposite situation. Here all corresponding parameters do work to ever lessen the resulting side-force of skating.
BTW - how about starting a "skating - anti-skating"-thread ?
Cheers,
D. |
Maybe all said about antiskating. Nevertheless it was quite an exiting expedition and I am still admiring my Ortofon RMA 309 how it manges all these requirements. No I don't need an answer - not this time and not here.
Best & Fun Only - Thuchan |
Dear Thuchan, .. and your RMA 309 features no antiskating device at all - for good reason.
Cheers,
D. |
When I first tried to actually use the UNIprotractor, I wished I hadnt have volunteered to do a review. No matter how hard I tried, I couldnt see the stylus?! The package from Germany arrived many days ago and at first I was slightly disappointed at the appearance of this plain brown cardboard box. Surely a white or black box with some unique graphics was warranted to encase the high-tech machine-like tool within? Of course that would have increased the costs and Daniel did not at first know, how many of these machines he would sell? Once opened, the contents were convincingly revealed to be well packaged and a few surprises, such as an LED high-powered lamp and a pair of soft white gloves were included. Prior to its arrival, Daniel had Emailed the coloured Instruction Manual together with the appropriate micrometer settings for 5 of my 6 arms and let me say that with the exception of the Copperhead, these instructions are better than those which came with all my tonearms. But back to the turntable. I had easily assembled the UNIprotractor as detailed in the Manual, and had it positioned on the nude Victor TT-81 with the Fidelity Research FR-64s tonearm as the first patient. This was not a fair test admittedly, for the Dertonarm recommended geometry for the FR-64s does not follow Baerwald or Lofgren and the spindle to pivot distance recommended by the manufacturer, is not followed by the UNIprotractor. I had already adjusted my spindle to pivot distance for the arm to be 231.5mm instead of 230mm and had aligned it via the Feikert protractor by utilising its overhang alignment rather than its Baerwald alignment. This also required a twist to the tracking angle but I didnt have the correct null points to accurately gauge this angle so I knew my set-up was inaccurate. The cartridge was a MM favourite of mine
the Signet TK-7e mounted in the FR-3 headshell and for the life of me, I couldnt see the stylus, head-on, through the magnifier. After developing mild backpain crouching for over an hour, I decided to switch off the lights, have a coffee and a well-earned rest. During this interlude, I pondered whether Dertonarm had erred in his design by using only modern LOMC cartridges rather than my preferred vintage MMs which had their stylus tips generally tucked well back from the fronts of the cartridges. Had I just purchased a white elephant I wondered as I gazed at the trees framed against a deepening blue sky? After an hour, I returned to the turntable, switched on the LED lamp and peered once again through the magnifier. Could it be? Was that it? A stylus tip? I grabbed my hand-held magnifier and held it behind the fixed magnifier and there I saw it
.a clear stylus and its black cantilevered shaft framed against the mirrored gridlines of the UNIprotractor :-) Most new tonearms are somewhat intimidating on first set-up but once familiar, they become easier and eventually simple to adjust. The same must be said for alignment tools. The Feikert was initially difficult and is now childs play as is Yips MintTractor and the WallyTractor. Once I knew what I was looking at and for, it became easier and easier to use the UNI protractor until by the fifth arm, I was laughing. The Signet TK-7e was out by nearly 2mm and its tracking angle was also off. Easily fixed using the UNI. My previous defacto set-up tool of choice has been the Feikert which is a one-point devise like the UNI. Whilst I use it to set spindle to pivot and overhang (based on Baerwald), I like to use the Mint to adjust the correct tracking angle at the Null points because it is so easy to see compared to all the other devices I have. The Feikert came with my DaVinci 12 Ref Grandezza tonearm and whilst one face of the white Tractor Disc is marked as a Universal template, the other face is dedicated solely to the DaVinci. As such, you would expect it to be ultra accurate and so it was. The UNItractor proved that the DaVinci was as good as you can get. With the other arms and various cartridges, the UNI showed some to be ALMOST perfect, whilst others required adjustment. None was perfect like the DaVinci, and having the UNItractor prove this fact, I trust it implicitly for the other arms. So is the UNItractor worth its price? If you have several arms and/or interchangeable headshells equipped with multiple cartridges, I would say yes. If you have only one arm and want the most accurate tool available to align an arm/cartridge then again I would say yes. Is the UNItractor perfect? No, I think it can be improved
..and quite easily. Firstly, being a one-point device rather than a two-point arc protractor, the spindle to pivot dimension is critical. There seems little point IMO, to have the accuracy and tight tolerances of the UNI if you can be 2mm-5mm out in your spindle to pivot distance? The best device I have seen for measuring this dimension, is the adjustable Feikert aluminium sliding beam and locator. This is rigid and super accurate but what does the UNI provide?
a floppy steel rule. There is simply no way that anyone can come close to accuracy with this means other than by fluking it. And this is so silly because the UNItractor already has a device which is nearly as good as the Feikert. The locating device which locks onto the spindle and hovers over the tonearm pivot could easily have a scale on its base which can measure the spindle to pivot dimension. I know that Daniel is soon coming out with a proper measuring device but this IMO is unnecessary. Another improvement I could suggest is that the mirrored templates which click into the protractor for each different arm, should be a frosted mirror like the Mint instead of the full mirror which is more difficult IMO to see clearly. A further suggestion I have is that the selected arm geometry should be engraved on these mirrored templates. At present one does not know if one is setting the arm for Lofgren A, B, Stevensen or something else as Daniel pre-selects what he considers is best for each arm. In some cases that is simply the arm manufacturers recommended geometry so that for my Grace 940G and Micro Seiki MA-505S which both have the same effective length and overhang, Daniel supplies two separate templates. Apart from these easily incorporated improvements, I have nothing but admiration for Dertonarms UNItractor. A serious device for the serious analogue audiophile. UNIprotractor |
Dear Henry,
thank you for this throughout comprehensive and dedicated review.
Please allow me to briefly address the points of concern in your post/review about the UNI-Protractor.
* MA-505 / Grace 940.....
While both tonearms do indeed share the same overhang, mounting distance and effective length, they had different destinations from their designers.
Hence the two templates have very different null points.
Consequently the micrometer scale must show different values for these two templates too.
The Grace 940 follows an unusual alignment curve with VERY little distortion in the 2nd half of the record.
The MA-505 does follow (according to it's designers) rather the Stevenson DIN calculation. I have a bit "optimized" the MA505 calculation alignment, while letting the Grace 940's alignment stand as it is.
* ruler as P2S......
Well this was included as a handy tool ( and not mentioned in the initial Audiogon listing, but added as a "freebee" later. This is just intended to serve as a quick check whether the mounting distance is correct. I thought it to be a nice add-on, as it offers ( not common ...) 0.5mm scale.
Please note, that this can not be incorporated in the positioning arm, as the positioning arm does not aim direct over the spindle.
Since the UNI-Protractor was designed to offers precise alignment for all mounting distances, it's positioning arm can not aim direct over the spindle and must be variable too in it's distance to the spindle for different null-point-alignments ( please see Dennesen's original patent for further details and perfect explanation of the geometrical background ).
BTW - "my" P2S-tool - the UNI-P2S - will be introduced (finally) early next week.
This however will be much too much for most and is only a suitable tool for professionals who do set up tonearms on a daily/weekly basis and want the most precise.
* "full mirror" vs "frosted mirror"
That may be a matter of personal preferences - to my eyes the full mirror parallax is much better, as it allows for clear view of even the most minor declination (especially the helping lines left and right wing of the cantilever center line).
* geometry - name engraved on template
Those templates following any of the "standard 3" (Bearwald/Löfgren A, Löfgren B or Stevenson ) have been named so.
All the others do either follow their manufacturer's geometry or have been re-calculated by me. In those cases where I have recalculated a specific tonearm's alignment, I have named it so (i.e. FR-64s 231.5 D.B.) as this most often goes hand-in-hand with a mounting distance different from the manufacturer's specifications.
If my "correction" was rather marginal (i.e. MA-505) I have not left my signature.
Again - many thanks for your time and effort to supply this review !!
Still worth a smile IMHO is the fact that the birth of the UNI-Protractor was initially provoked by the deleted "FR-64s geometry" - thread of past early winter.
Cheers,
D. |
