Ok,
more "off-set" friction.
I'm lost, but learned to be stuck, just being with the question :-)
More to learn as it seems. So thank you all for your patience and kind participation, massaging my lack of awareness in this matter.
Axel |
Hi Pär,
the vinyl is indeed kind of soften and expanding its surface due to the heat of the stylus .
That is an old problem noticed by record companies as long back as the middle 1950ies. Thats why records do suffer from repeated playback (especially single tracks played over and over again in a row - which BTW is a (smaller) problem with CDs too....) - the vinyl has no "time" to "recover" (read: return into its original form and cooling down completely).
Thats why it is so important - aside from recovering the most tiny detail information engraved - that the stylus is as perfect aligned as possible.
A misaligned stylus does obvious create much more "problems" to the softened vinyl groove wall.
An while friction may be linear to VTF, the pure kinetic force on the groove wall is a result of down-force divided by contact area. The largest contact area (and resulting lowest force on the groove WALLS (plural..) in A GIVEN RECORD is in the groove-compliant VTA.
Means - even if not all agree on the sonic benefits of a certain VTA for a certain record, it is in this very situation, that we have the least "pressure" (VTF divided by contact area) on the walls of the record groove.
Cheers,
D. |
Axel, that is in the general accepted model I mentioned.
To illustrate the point:
an uni-pivot tonearm with no lateral balance and an offset (be it in the way of a S- or J-shaped pipe or an offset headshell mounting area on an otherwise straight arm-pipe) "head" would - if viewed from the front towards the cartridge mounted - "swing" down with its right side over the long axis till it finds a position in gravity.
This "down-swing" over the right side does cause the force towards the inner groove wall (left....- viewed from the front).
Now - if this obvious tendency is (just as a hypothesis...) completely (even the technical books aren't very detailed here, but the general term used - even in old AES literature - is, that the bearing in general does not "completely support (address)" this torque movement) counter-balanced at or in the bearing, we would see no longer an additional friction at the inner groove wall which would be rooted in the offset.
This model would indeed require a design which does feature a lateral balance option which would be able to counter-balance the downforce initialized by the offset.
The "actual friction force" we see on pivot tonearms is (I am careful now...) "maybe" not only a matter of the offset.
As this force is in my 30 years long experience quite different in different tonearm designs (mounted with identical cartridge and stylus and VTF) I believe (I am careful again....) that there is still more to it than just the force initialized by the offset of the pivot tonearm's geometry.
All I want to suggest (carefully....) is that maybe there is more and that we - maybe - settled to soon with an explanation which - maybe - does not address all parameters.
I will get a Wacom touch board next week - then I can draw the whole model and try to illustrate the point by graphics.
Cheers,
D. |
Perrew
No that's not what I'm saying.
I said I wan't going to try to explain Hertzian contact theory to you and I'm sticking to that.
Mark Kelly
|
Dertonarm,
I'm a bit lost with the concept "that the bearing of the tonearm is not able to *completely support* the resulting force towards the inner groove"
All that means to me the friction of the tonearm-bearing subtracts itself from the skate force as it is an opposed force?
If you tighten up the bearing that much so is equals the skate force, the arm will not be moved by the skate force anymore.
Where it fits into the understanding of it all I'm not sure right now.
The friction force will create a vector forces due to the arm held at the pivot and produce a resultant force - the skate force. Actually pretty simple, until you want to actually calculate what this resultant force would be.
All we know, it's pretty much proportional to the actual friction force --- that force which we usually don't know and keep guessing about.
Axel |
Mark, regarding Hertz are you saying the contact area of the vinyl is expanding due to deformation with increasing force, (I dont see the stylus deforming), and therefore the contact area might expand more than the force and P becomes smaller even though F increases? |
Axel
I've just read your post more carefully and my first response was too hasty.
I'm not familiar with the term "tangent trace angle" but by your description it is what I described as "true offset angle".
Indeed we may have been suffereing from terminological incommensurability.
Mark Kelly
|
Axelwahl
You said no groove = no offset. That's not correct.
The tangent to the arc of the stylus traces on the vinyl does not pass through the tonearm pivot. Therefore there is a separate vector pasing through the same point (the stylus contact point) which does pass though the tonearm pivot. The first vector is the stylus frictional reaction force vector, the second is the tonearm restraining force vector.
The angle between these two vectors is the angle I described as the "true offset" and which we are now going to call something else, hopefully slightly less cumbersome than "the angle between the stylus frictional reaction force vector and the tonearm restraining force vector". As explained above, the fact that the stylus frictional reaction force vector doesn't pass through the pivot is what causes skating. That's all there is. Nothing more, nothing less.
Mark Kelly
|
Mark,
+++ The frictional force vector is in the direction of relative motion between the stylus and the vinyl. +++
>>>Yes!
When the stylus is following a groove, this direction is tangent to the groove curvature.
>>>Yes!
When the stylus is not following a groove, this direction is tangent to the scribed arc of the stylus on the vinyl.
>>>Yes!
+++
I completely agree with all the above.
I have no idea where you see a: "false dichotomy"
in my statements of: No friction = no skate force, no groove = no "off-set" in the groove (well there is NONE).
The only other angle is that angle between pin-point stylus to pivot and the pivot to centre of rotation. This angle seeks itself to be closed as soon as a friction force is applied.
If indeed it is what you keep referring to, we have no argument only an issue with terminology.
"Off-set angle" is by definition (in my universe and also at least SME's) the angle the head-shell and thereby the stylus is "off-set" in relation to the tone-arm-wand. This "off-set", (specific to each tone-arm) should produces two null-punkt (0 deg tangent angle) spots on the vinyl after correct alignment.
This tangent (tracing) angle is a constantly changing angle whilst the tone arm moves toward the centre of rotation, or end of record.
I am starting to think you are using "off-set" in place of this variable "tangent trace angle"?!
Sen wat we hav here is se problem mit de "Begriffsbestimmungen", oh mein Gott!?
Failure to communicate?
Axel |
Ok I can see it now.
The coefficient of friction does indeed reduce with pressure but what we haven't established is that the pressure is a linear function of VTA. For that to be the case contact area would have to be constant and it isn't.
I'm not even going to try to explain why not, I have a reasonable grasp on Hertzian contact theory but not good enough to explain it to you. Google Hertzian contact theory and you might see why.
Mark Kelly
|
Mark you said, P=F/A and "The breakdown takes the form of a pressure dependent coefficient of friction; the coefficient decreases with increasing pressure "
Still an example with your choice of tonearm would be helpful. |
Perrew
I cannot see how you can get to that conclusion.
Axelwahl
I love how you can take a simplification and twist it until it becomes a complexity. Your jump from "no groove" to "no tangent" is unjustified.
The frictional force vector is in the direction of relative motion between the stylus and the vinyl. When the stylus is following a groove, this direction is tangent to the groove curvature. When the stylus is not following a groove, this direction is tangent to the scribed arc of the stylus on the vinyl.
The rest of your post rests on this false dichotomy so it also falls (except for the bit about our befuddled friend DT not knowing what he's talking about. That I agree with)
Mark Kelly
|
Axel, the often cited law of friction by G. Amonton (who kind of re-discovered it 2 and a half centuries after its original "inventor" Leonardo) as the main "law" being the skating force in phono playback assumes, that the bearing of the tonearm is not able to *completely support* the resulting force towards the inner groove. This force is a result of the offset of the tonearms "head" and therefor the cartridge and its cantilever. This offset implies a force that would - if not compensated by bearing or lateral balance - swing the tonearm's "offset part" (the "right side" if view from the front towards the cartridge/tonearm head) downwards because it needs to find a stable position in gravity.
Thus resulting in a horizontal force on the inner groove wall.
So far so good.
And I agree with this of course.
This is true for most pivot tonearms.
But not for all I think.
Now what IF the bearing is able to COMPLETELY SUPPORT the resulting force.
It is obvious, that most uni-pivot tonearms and knife edge bearing tonearms (among others) can NOT completely support this force.
However - a rather long effective (12" is fine .... of course 16" would be better) tonearm with resulting LESSER offset and a left side lateral balance can (at least in empirical observations.....) almost (if not 100%) completely support that force, as it is compensated by lateral counterforce.
A completely balanced FR-66s with its lateral balance correctly adjusted and on dead level TT shows no skating force in the 2 zero points of the tangential curve.
2.7 VTF with a stylus even "sharper" than a line contact.
A SME 3012 with bronze knife bearing does show heavy skating even in the 2 zero error points.
Both tonearms adjusted for same tangential curve and running with the same cartridge (FR-7) on the same table.
Maybe this way I can illustrate why i still think, that the model ... maybe .... is a bit more complex as the initial anti-skating model we are used to.
BTW - I vividly remember that the anti-skating devices in former Thorens, some EMT and Dual turntables (among others of west german manufacturers of years gone by) showed at least 2 different anti-skating scales: - one for elliptical stylus, one for conical......... |
Mark,
ja now fine, and so we have even more discrepancies since I, for the sake of TRUE simplification, been talking over and again about BLANK vinyl, and the stylus point riding on this smooth surface --- AND THEREBY taking any of this groove tangent stuff OUT OF THE EQUATION.
There IS a skate force WITHOUT any groove! Therefore NO tangent, what so ever comes into play as I tried real hard to get across.
Taking things into the groove, with all this stuff Perrew is on about is no good, if the basics are not cleared up, yes?
So, again, NO friction force, NO skate force, period.
Tangent has NOTHING to do with it at this point, *if we are NOT in any groove*!
As such all this talk about tangent, or off-set, etc. only serves to cloud the basics of the skate force issue --- unless you are much more deeply into the details then at this point was my understanding.
As such, and going back to the SIMPLE, *no groove*, model Dertonarm is NOT right in assuming a zero skate force at a 0 groove tangent angle.
I can prove that, as soon as there is friction, there is a skate force.
His (Dertonarm's) point is such only of any relevance, if at 0 tangent groove angle -- and as he assumes --- there be less friction force than at any other angle.
If this be so in the first place (and I have no explanation why it should be so!), it be so minute a difference, as to have no measurable effect.
Therefore off-set is as little part of the PRACTICAL equation as is Over-Hang. If one groove side is traced a micro-millimetre later (or earlier) then the other --- what be the increased friction due to that?
None! for a spherical stylus, and none for most any other stylus as well, even it the sides be a sharp as it gets.
It will make a mess of the signal, oh yes, but that is another discussion all together i.e. correct cart alignment.
Axel |
Mark, so increasing the VTF would increase the pressure and the skate force would decrease, all else equal? Wouldnt this imply that high VTF means anti-skate can be ignored? |
Axelwahl
I think I have confused you by trying to simplify things. The angle I referred to as the true offset is the angle between the groove tangent and the line between the stylus and pivot. The frictional force acts along the tangent so this is the angle between the frictional force vector and the restraining force vector. The true offset angle varies with groove radius for ordinary pivoted arms and the offset angle of the arm is an approximate average of the true offset angles.
I can see how this is confusing and I should probably have used a different term.
Perrew
You are confusing force and pressure. The force is set by the VTF and the groove angle, so the sum of the forces on the sidewall is SQRT 2 times the VTF (for 90 degree groove). The pressure is this divided by the contact area. Larger contact area = lower pressure for a given VTF.
Mark Kelly
|
Mark, my rudimentary understandig says line contact has less force on the groove wall so shouldnt less force lead to lower friction and hence lower skate force, but I cant reconcile this with your Amonton law breakdown stating lower pressure implies higher friction, although wont some of the breakdown be ameliorated by the cantilever making the diamond less hard compared to the vinyl? |
Mark,
am I having a different understanding of what is off-set?
It may explain perhaps some crossed wire...
"Off-set" in my vocab is the angle that a head-shell / cart /cantilever is mounted out of the true / straight line with the tone-arm-wand i.e. 0 deg = no off-set.
As to the various measured forces caused by friction between various materials I have no issue with at all.
In fact, and often, the faster the speed the LESS the friction force e.g. when an object starting to plain on water, rather then being dragged through it is some extreme case in point.
If a tiny tip of a stylus is 'dragged' over smooth vinyl, I can see that no measurable difference in friction force would be the case.
However, no friction force *NO* skate force!
It is this friction that wants to pull the stylus tip with it. Since it can't, due to the arm pivot holding it back, it will do the next best thing and pull the arm in line with the center of rotation. This would also be the shortes distance from pivot to center of rotation, right?
Like a pendulum being pulled (eventually) to the shortest distance from pivot to the center of gravity.
No gravity force, the pendulum will remain where ever is happens to be.
Axel |
Axelwahl
Go back and read my post 15 above this one.
Mark Kelly |
Thank you Mark,
but you are missing the friction force in your test suggestion, present in variable degrees due to variable VTF / stylus shape / friction, as mentioned.
Therefore there will *always* be a skate force present even at 0 mm over-hang :-)
There will be MORE skate force with more overhang, my initial argument and proven by test.
The influence of the VTF => friction is (as I said also) of much more influence i.e. over-hang may therefore be ignored as be off-set, since they are a non-variable parameter (in theory at least) according to a specific arm geometry.
The test: lift the stylus of the vinyl and you'll have 0 skate force where ever the arm is :-)
Greetings,
Axel |
Axelwahl
I have a simple test for you.
If possible, adjust your arm to zero overhang and check the skating. It will have changed very slightly (due to the change in offset angle) whereas if I read your theory correctly you would expect no skating at zero overhang.
Mark Kelly
|
Al,
I'm fine by that, it does not contradict any of my own findings.
Axel |
This has certainly evolved into an interesting thread, and an educational one despite the several contradictory claims which have been made.
I've just done an experiment to try to bring it all down to a more practical level. As I mentioned in my earlier post, I have always set up anti-skating on my mm/mi cartridges so as to produce no visually detectable right or left deflection of the cantilever when it is in the record grooves, compared to when it is not in the grooves (which has always meant straight ahead, with my cartridges).
Using the high output Grado Reference Sonata which I presently have installed (compliance 20, vtf 1.5g, elliptical stylus), I carefully looked for cantilever deflection at approximately 12 different points distributed across the full length of a lightly modulated (chamber music) recording.
At no time did I see the slightest deflection.
The cartridge is mounted on a 1980's SOTA Sapphire turntable with Magnepan Unitrac tonearm. Anti-skating is set for about 2/3 of the value recommended in the tonearm manual for the 1.5g vtf (35 shot pellets in the bucket, instead of the recommended 52). As a point of interest, I had previously had a Grace F9E Ruby mounted in that arm, set up by a very good dealer using an oscilloscope, test record, and Lissajous pattern. Their setting was also about 2/3 of the recommended anti-skating for the 2g vtf used with that cartridge (52 pellets instead of 79). And I have found a similar 2/3 factor to be about right on some other turntables/arms/mm cartridges I have set up in the past.
When I have done these setup procedures in the past, modest deviations from the anti-skating settings I settled on, such as using 30 or 40 shot pellets instead of 35, produced clearly perceivable deflection.
It seems to me that this experiment, indicating no perceivable deflection at any point across the record, supports the following conclusions, as pretty much stated earlier by Neil (NSGarch):
1)While skating force may vary from one point on the record to another, the range of variation is very small compared to the nominal value of the skating force.
2)The considerable cantilever deflection that does in fact result with these or similar cartridges from using zero anti-skating force would seem simply based on common sense to be undesirable.
3)Common sense would seem to suggest that the same two conclusions apply to moving coil cartridges, except that with these cartridges the differences resulting from different anti-skating settings (including 0) may be more difficult to perceive, because of their stiffer suspensions, lower compliance, and (possibly) different stylus shapes.
Can we all agree on this, from a practical standpoint?
Regards,
-- Al |
Ok, move the SME arm forward you change the off-set angle yes.
Again, if you are running on the pin-point of the stylus, it has NO influence at all, at what angle that pin point rubs on smooth vinyl as a pin has no unequal sides --- unless that is only the case in my universe...
The change in friction force caused by a change in VTF of that pin-point is of course of MUCH greater influence and goes hand in hand higher VTF asking (all things being equal, which in the groove they are not...) for higher anti-skate compensation.
Also, the over-hang for a given arm is a ~ fixed parameter and as such it can actually be disregarded, fair enough.
There the variable is the VTF / friction force => stylus geometry.
As to the "off-set" it is the same as with the over-hang i.e. fixed also for any particular arm geometry and therefore also can be disregarded.
Axel |
Mark, I understand you dont want to do that but could you desribe with some other tonearm?
Tks
Par |
Perrew
Unfortunately I can't do that without revealing details of my tonearm's geometry which are not yet ready for publication.
Sorry.
Axelwahl
You have changed the offset angle (because the SME overhang adjustment works by moving the pivot not the cart)
Mark Kelly
|
Hi,
funny, talking with my 'learned friends' I find *experiment most ALWAYS precedes scientific explanation...* :-)
I just now proved to myself by simply sliding my SME V arm forward from its ~ 18mm overhang to some more without changing VTF = 1.25g and anti-skate 1 on the arm scale which keeps the arm in balance on the blank area of my test record.
Slide the arm enough forward (increase overhang) and ---- the skate force increase enough to now pull the arm to the centre.
Now let's consider a cart like my Windfeld with more then twice! the VTF (2.6g) and the result should be even more telling.
Greetings,
Axel |
Mark, could you walk me through a real life example of Anti_Skate setup with your own arm and cart? |
HDM
The reason tonearm manufacturers put a scale on the antiskate corresponding to VTF is that the skate force is directly proportional to VTF, not that it equals VTF.
The constant of proportionality has already been factored in and the manufacturer based this on "average" vinyl composition and a typical contact area.
The difference between your old stylus and your new stylus will depend on the degree of polish on the diamond and the actual area of the contact patch. Note that with line contact styli the actual area changes with VTA so VTA and antiskate interact. BTW This is the only rational explanation of the effects of VTA I know of.
This also shows that even if one confines onesself to the realms of actual verifiable physics the situation "on the vinyl" is quite complex. There is nothing in audio which can't be explained with physics, its just that we haven't worked out all the physics yet. One thing is certain, if an explanation for an effect defies the known laws of physics than that explanation is wrong.
Mark Kelly
|
Mark: I'm interested specifically in what your thoughts are on antiskating as it relates to stylus profile.
If I'm reading you correctly, elliptical styli should require less antiskate than spherical and line contact should require more than elliptical-please correct me if I'm wrong and misunderstanding your post.
Despite all the reading on (in theory) how little antiskate may actually be needed, I've found that my Denon 103R (with its stock spherical stylus) sounds best with an antiskate setting that is very close to the 2.6 gram tracking force.
I'm in the process of having another 103R retipped with a line contact stylus and am curious as to what, if any, changes I may have to make with antiskate when that cartridge comes back. Would you expect that, like the stock 103R, one retipped with a line contact would require antiskate set to approximate tracking weight? Thanks in advance. |
Oops
The Xs and Ys are reversed. Consider the arm lying along the X axis with the Y axis pointing down and it comes out right.
Sorry about that
Mark Kelly
|
Doug
I find your argument a little confusing. If one did as you say and merely twisted the cartridge in the arm while keeping the alignement of the arm WRT the groove tangent the same, you would create very little force, as my post above explains.
The force you do create would be because the cantilever was bent out of alignment and the suspension is trying to force it back. This force is very small compared top the true skating force and with good alignment it is even smaller.
Mark Kelly
|
Hm,
I still don't get it, call me stupid alright :-)
Put any (hypothetical) 20, 60, 90 deg. off-set angle on a POINT contact only stylus (I'm not talking distortion right now) just spinning on a blank vinyl -- what effect will you notice as long as the point contact to pivot would be the same?
No difference at all is what I stated earlier.
(no 'spade' is getting dragged through some sludge or a groove at this test!)
The stylus' point, sliding over smooth (no groove!) vinyl, will want to align the arm wand in a straight line *pivot to centre of rotation*.
Now increase the over-hang and then what happens?
The more overhang, the longer the frictional force's lever. It will pull the arm wand harder in line (pivot to centre pin) = more skating force? I think so.
Or no change at all? I do not think so.
In deed, what means off-set angle with regard to a 'round' point (contact stylus tip) any way?! - as long as the over-hang length is not affected?
Axel |
Axelwahl
You are assuming attitude is important but it isnt.
Consider the frame of reference of the tonearm with its pivot point as the origin and the arm lying along the y axis. The stylus frictional reaction force vector runs directly from the stylus tip in the direction of groove motion. The restraining force vector runs directly from the stylus tip to the tonearm pivot. The sum of these two vectors is the net force on the stylus.
The angle between the groove tangent and the x axis is the true offset angle. The stylus reaction force vector can be resolved into x and y components equal to its magnitude multiplied by the cosine and sine of this angle respectively. Since the x translational degree of freedom is constrained, the sum of forces in the x direction must be zero so the restraining force must be equal to the x component of the stylus reaction force vector.
For the y translational degree of freedom also to be constrained (eg the stylus not skip out of the groove) there must be a force which balances the y component, this force is either supplied by a reaction force on the groove wall or by antiskate.
IFF the force is supplied by reaction against the groove wall then the fact that that reaction force is not purely in the Y direction creates complexities but we can assume that the arm has been designed by someone who knew what he was doing so it has antiskate therefore we can ignore this: designing a pivoted arm with no antiskate is prima facie evidence of incompetence. The antiskate can be applied as a torque to the arm pivot or a force to a point somewhere on the arm, its all the same as long as the vectors resolve.
The argument from attitude rests on a falsehood which is that the stylus frictional reaction force somehow depends on the attitude of the stylus to the groove wall. A misalignment of say 10 degrees would result in a displacement betwen contact patches of about 25 microns for an elliptical stylus 7mil across, for a spherical sylus there would be no displacement at all since the contact areas between a sphere and a plane are always normal to the radius of the sphere.
This torque arm would result in a torque of about 0,5 uNm at 20 mN VTF where the actual skating torque is around 1mNmm, a difference of 2000 to one.
The issue which Id like to resolve is that of the influence of stylus shape. Amontons law for rigid bodies breaks down if one body is much softer than the other, which is definitely the case with vinyl and diamond. The breakdown takes the form of a pressure dependent coefficient of friction; the coefficient decreases with increasing pressure this seems counterintuitive but think about a car tyre: wider tyre, lower pressure, better grip. Since elliptical styli have greater contact pressure than spherical, the friction will be less for them and this was reflected in many tonearms having separate scales for elliptical and spherical styli back in the day. Check the owners manual for the Torens TD160 mk2 for an example. Since a line contact has, by design, a larger contact area the skating force should increase not decrease as our befuddled friend supposed.
Mark Kelly
|
Axel,
Try your experiment using a pivoting arm having zero offset angle (like a transcription arm). Provided the cantilever is aimed correctly (i.e., directly at the pivot point of the tonearm), skating force will be zero. This will be true regardless of overhang.
Skating force is generated when we mount a cartridge at an angle in the headshell such that the cantilever is NOT aimed at the tonearm pivot (in a word, offset). Overhang has nothing to do with it.
Using that transcription tonearm (which has zero offset by design) you could still create an inward skating force by mounting a cartridge at an inward angle, just as on a regular tonearm that has built in offset. You could even create an OUTWARD skating force by mounting the cartridge at an outward angle. Again, you could do either of these regardless of overhang.
|
Of course my idea is wrong.
But that is always the case.
After we have agreed upon that and set it aside, maybe someone is willing - or not..... no problem (at least not mine) - to visualize what is actually happening aside from dogmas, simplified models, laws (which aren't what they used to be either) and small hills which became mountains (ever seen the nice movie with Hugh Grant who climbed up the first and came down the later?).
With all those clear models around, I really wonder why there still are so many complaints and discussions about inner groove distortion, off-angle cantilevers, wandering images and sibilants which pierce the ear.
With all those great anti-skating devices around.
Strange. |
another *sector* should of course read: another *vector*... |
Dear Mark,
use your test, whereby the tip of the stylus only touches the vinyl.
The contact area thereby sees no off-set, and simply assumes the shortest point between contact area and pivot = one of the vectors. Overhang to the spindle is creating another sector, with the spindle to pivot a third.
Thereby off-set is not involved, yes?
Axel |
>>10-12-09: Stringreen
10-12-09: Stringreen
Dougdeacon...you're correct, but anti-skate decreases with velocity<<
Wrong again stringbean.
Mark Kelly has it right.
As does Nsgarch. |
Stringreen
That is not correct, stylus friction follows the classic Amonton law so the friction is independent of velocity. This can be confirmed by a modification of the test Doug Deacon used to demonstrate that Dertonarm's idea was completely false.
Using your blank disc and having satisfied yourself that skating has nothing to do with null points, set the antiskate on the arm so that the arm remains stationary at 33 RPM. Now change the speed to 45 RPM and observe the result.
Axelwahl antiskate is properly a function of offset not overhang.
Mark Kelly
|
Dear Doug, lets not mistake the torque tension force (which is indeed a result off the offset angle at the headshell) or the J-/S-shaped form (featured on tonearms with detachable headshell) common on most pivot-tonearms (and seldom addressed....).
As many (not all) a tonearms do not feature any lateral balance device at all to counterbalance the torque tension of its armpipe, these all too often do indeed produce a movement on a plain record.
I have performed the test you suggested several times.
With my 12"+ tonearm and a cartridge with Q4-capable stylus the tonearm (... with correct applied lateral counter-balance and on a dead level TT) sits still (no inward move) at the 2 zero error points of the tangential curve.
Am I missing parameters?
Pure luck ?
Coincidence ?
Correct model ?
Whatever......
Fact is - as a selected handful (precisely...) of the bavarian routed A'goners do know very well - that sibilant distortion, inner groove distortion or "wandering images" are non-existent on the front-ends set-up by me.
And no - these aren't all FR-tonearms, but do include DaVinci, Kuzma 4P, Graham, SAEC, Micro MAX, Triplanar (to name the better of the pivot-designs).
9" to 12" which - by the way, Axel - can not really be distinguished in groups by their overhang.
And yes - exactly - what would we prefer?
A "simple" (but precisely designed and engineered - all too often forgotten as we are so accustomed to it - german car or a "complex" (....complex ? where ?) british one (and - oh, sorry - is there still any major british car brand NOT owned today (and improved in terms of reliability and performance by its new owner) by either BMW, Audi or VW .... Jaguar is owned by Ford isn't it?).....?
And yes, I know that the japanese cars are even more reliable - fact is that I still prefer 2-3 japanese born tonearms (which by the way did address the issue of torque tension producing lateral movement...) above any german designed tonearm. |
Hi,
anti-skate force is a ~99% function of the OVERHANG!... have I been missing something?!
Without overhang, no vector force, no skating force.
If you had "underhang" you'd create a vector force once again, but it is not of practical interest other then in the consideration of the vector forces.
Axel |
Dougdeacon...you're correct, but anti-skate decreases with velocity so that it becomes less and for all practical purposes, pretty much zero at the end of the LP. That being said, Highly modulated sections of the groove will create more skate than quiet sections all through the record. ...just clarification...I'm sure you know that. |
Dertonearm,
I do not understand why you assert that skating force is "null at any zero error point". If you're saying that skating force is null at points of zero tracking angle error (e.g., at the Baerwald or Loefgren points), that is simply untrue.
Skating force exists ANY time the axis of the cantilever is not aimed directly at the pivot point of the tonearm. Therefore, EVERY tonearm with a fixed pivot point and an offset cartridge mounting angle encounters skating force at all points that the stylus is riding on a spinning record.
Don't take my word for it, and let's not argue theory. Just try this simple experiment: find a record that's ungrooved (flat) at the null points of your particular alignment scheme. Set A/S to zero, spin up the record (the faster the better) and drop the stylus at one of the null points.
Unless you're using a linear tracker or a pivoting arm with no offset angle I guarantee it will "skate" inward.
Once you've performed this simple experiment you will revise your theory, because it doesn't meet observed phenomena.
If I've misunderstood your assertion, please explain in other words if you can. I fear your current assertion is potentially misleading for the less experienced.
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Stan, the Supex cartridge(s) you specifically refer to, have elliptical styli. In fact, Supex makes cartridges with either spherical or elliptical styli - no line contact styli! AND they all have medium compliance suspensions, and some even have high compliance suspensions, just like most MM cartridges. Add to the elliptical stylus, a recommended VTF of 1.8 gm and you have a recipe for high skating torque. So from an anti-skating adjustment point-of-view, those Supex are indeed more like MM cartridges. So I think you need to do your homework before making general assumptions like you did.
I also think it's a bad idea to assume, as some others here do, that there is such a level of complexity at work in this situation, that all efforts at resolution are hopelessly doomed. If one understands the basic forces at work, and especially their overwhelming magnitude compared to the little molehills some want to make into mountains, (to prove how smart they are?) it's really a simple matter to cancel 90% of them out. If you want better than that, as I said, get a straight line tracking tonearm.
As for implementation, would you rather have a 'simple' German car or a 'complex' British car? Hmmmm . . . . . ?
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Dear Stan, you are of course right. We have seen - and still have... - MCs with VTF around 1.2 to 1.5 (v.d. Hul among others). MC do NOT have ad decretum lower compliance than MMs. The skating force is - among others - a result of VTF, offset of the stylus towards the groove wall and total contact area of the stylus. Its becomes less with increased effective length and resulting decrease of tangential error. It is null at any zero error point and becomes more and less with increasing tangential error and decreasing to wards the next zero point.
Simple model.
The force is never constant - and should therefor be addressed by an inverse force which is itself variable in conjunction with the tangential curve of the given tonearm.
Not really complex - it just needs more than a plain stupid constant anti-force.
But nothing in our days is so clear as not to be neglected and denied by some.
I am positive that maybe Raul in his new upcoming tonearm-design will address this issue.
Of course we can always simplify things and we see a strong movement in this direction ever since the last 2 generations.
Why ?
Because it makes things cheaper to produce.
More profit made - less brain needed.
Simple story indeed. |
Stan, the tonearm manufacturers are indeed now catching up with the essential differences between MC and MM cartrige requirements. Or to be more specific, the difference in the tonearm settings required by cartridges with line contact styli and previous types of styli. One example of this response by manufacturers is the SME IV.V which is made specifically with MC-with-line-contact-styli in mind. It's like an SME V, but comes without silicon damping (unnecessary for MC cartridges' stiff suspensions) and without hairspring VTF adjustment (also unnecessary for cartridges tracking in the 2 gram range.) Further, no current manufacturer of quality tonearms is silly enough to assert that the user just blindly set the antiskating force scale indicator to match the VFT setting. They all know better by now ;-)
As I indicated previously, the reason MC cartridges, or more accurately, cartridges with line contact styli, require so little antiskate compensation, is because they create so little skating force to begin with. Simply put, for each gram of VTF, a line contact stylus "drags" in the groove just a fraction of the amount that a conical or elliptical stylus would. And since 'skating force' is a product (read: multiplication result) of stylus friction drag TIMES the length of a (virtual) lever arm which is created by headshell offset angle. Therefore, lower stylus drag produces less skating force with a given tonearm.
If a tonearm has no headshell offset angle (like some of the old 12 -16 inch transcription tonearms) then no skating force is produced because there is no (virtual) lever arm for the stylus "drag" to act upon. However, with long tonearms, you still pay a small price in increased tracking error and a big price in tonearm resonance and inertial momentum (the tonearm wants to keep going UP after a record warp ;-)
If you want to have your cake and eat it too, get a linear tracking tonearm - no skating force, no tracking error, stylus rake angle (SRA) adjustable while the record is playing - and they do sound fabulous, I've had one. BUT, they ARE a hassle, needing (usually) an air pump, and constant checking. Or, as you might also remember from the 60's, the goin' up just ain't worth the comin' down! |
Nsgarch, I have no idea where you got the idea that the Grace was used with MM cartridges, it was sold as a package with the Linn LP 12 and Supex cartridge in England and I sold it with the 901 Supex over here. I also have no idea where you got the idea that MM and MC required different settings, I have followed the literature since the early 60s and never heard this. We are talking about a mechanical system here, how does the physical force pushing the arm know whether it is a MM or MC. Could you tell me where you got this idea? I have sold tables and cartridges for over 30 years and I never saw a mention of different compensation for MM and MC by any manufacture of either MM or MC. It was also applied SOELY on the basis of tracking weight, the test I quoted simply said that the bias force was off by a factor of two. This test was done by people whose knowledge of the subject far exceeds that of either you or I so you have either discovered something unknown to others or only true in your universe. Otherwise I would think arm manufactures such as SME would make some mention of it. |
Hi guys,
this developing argument reminds me somehow of what Søren Kierkegaard (19th century Danish philosopher) who once said: "If you get married you'll regret it, if you don't get married you'll also regret it, and if get married or do not get married you'll regret it.
Oh, he also said: "If you hang yourself you'll regret it, and if you don't hang yourself.... :-)
Now replace 'anti-skate' for the 'married' or 'hanged' bit, and see what it looks like...
I'd say: you regret it :-)
Greetings,
Axel |
Al, thanks for the reinforcement. You obviously have more insight/experience than you want to claim ;-)
Tonarm, I really have nothing further to say to you ;-(
Neil |
