This is a great resource for figuring out stuff like this: http://www.cartridgedb.com but this time I'll save you the trouble. Your cartridge has a pretty low compliance, even for a moving coil (10, compared to say Transfigurations at 15, or vdH at 30) and weighs 9.8gm. Your Sig TA has an effective mass of 9.5gm, which is borderline-low for such a stiff cartridge suspension. Here is the compatibility chart for your TA and cart: http://www.cartridgedb.com/resonance_from_arm.asp?adesc=VPI%20JMW%209%20Signature&amass=9.5If you read down the left side until you come to 10, the compliance of the te Kaitora, and then read across to the cart weight + mounting hardware column (figure 9.8 gm + 1.5+ gm for mounting bolts and nuts, total = 11.5 -12 gm) you will find yourself (barely!) in the 'green' zone at 11Hz, which is the natural resonance of your arm/cartridge combo. Lower (like 8Hz) would be better but you're SAFE for all but the wildest, loud, low-frequency tracking conditions! With a cartridge with as stiff a suspension as yours, you probably should not need any fluid damping at all. Even a slight amount could slow down bass transients. As for AS, line contact styli (like yours) develop very little friction in the groove because of their shape, and therefore the arm tends not to "skate" toward the spindle with any significant force. If you feel more comfortable, twist the wire until the floating arm just barely creeps toward the outside of the record and that will be plenty ;-) |
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 |
Skating force is a 'twisting torque'. It occurs only in tonearms that have an angular offset built into them to help minimize tracking error - making it zero at two points across the record instead of one point (which would result if there were no offset.) The amount of the skating force is the result of the friction force (or drag) of the stylus in the groove times a lever arm. The length of this lever arm is the length of a line drawn from the stylus, pependicular to the axis of the cartridge, to the point where it intersects at 90 degrees with a line drawn through the pivot of the tonearm. Since this relationship remains constant, regardless of the stylus' position on the record, the skating force remains essentially constant across the record. I say 'essentially' because there is some very minor variation in the force-of-friction as the velocity of the stylus-in-the-groove slows down toward the center of the record. ANTI skating force, when applied with a spring, can be made to compensate for this (VERY slight) variation, as in SME arms. However, the weight-on-a string method or the twisted-cartridge-leads method will work just fine. Whether AS has an effect (or not) depends on the design of the cartridge. Stiffer suspension material and/or lower VTF reduce the need for AS. Further, the larger the size and strength of the magnetic field in which the coil is immersed, the less AS will make a difference/improvement.
Increasing the VTF will ALWAYS increase the skating force/torque because increasing the VTF increases the friction of the stylus in the groove. The fact that line contact styli produce so much less friction (compared to conical and elliptcal styli) is why moving coil cartridge makers (using line-contact styli) are able to use higher VTF's and stiffer suspensions necessary for the generally superior performance of MC cartridges.
With MM cartridges the situation is reversed. True they customarily track at 1/2 the VTF of MC cartidges, and many of them now employ line contact styli. However, because of their extremely compliant suspensions, it's easy for just a little skating force/torque to pull their tiny magnets out of alignment with the field coils.
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God bless America. Dertonarm has a right to express whatever ideas he feels are true ;-) and on any subject. Besides, they say laughter is the best medicine. So I say 'Good luck' to him! |
Stanwal, first of all the Grace 707 is a vintage tonearm calibrated for MM cartridges, not MC which require far less AS. The rule of thumb in the MM days was that the AS should equal the VTF, and even at that, how much sideways AS force (in grams) was applied was definitely NOT the same as the actual weight on the string. Skating force is expressed as torque (foot-pounds, or centimeter-grams in the case of tonearms) and is the product of friction (in grams of drag) TIMES the (virtual) lever arm created by the tonearm offset, in centimeters; and is easily calculated if you know the amount of drag of the stylus in the groove (admittedly hard to determine without proper instruments ;-) The lever arm length is a result of the tonearm dimensions and offset angle. Those two factors don't change, regardless of where the tonearm is positioned. To be fair, the amount of groove friction actually CAN change (but only very slightly) between the beginning and end of the record as a result of the slignt difference in linear velocity (the speed of the groove under the stylus) between the outside and inside grooves of the record -- not enough to make a significant difference in AS force required. I suppose if one wanted to get REALLY nit-picky, one could also mention that louder passages produce more friction than softer passages. But that's pretty much it in terms of the causes of skating force (torque.).
With all cartridges except those with the stiffest suspensions, as long as you can see the cantilever from the front of the cartridge, it's quite easy to set AS force visually. I always did it that way with my MM Shure cartridges. You just lower the stylus into the groove while watching the cantilever from the front. If it deflects to the right (relative to the cartridge body) you need to add AS force. If it deflects to the left, AS needs to be reduced. No deflection of the cantilever when the stylus hits the groove means the skating force is balanced out. It could also mean that the skating force (even without AS applied) is not enough to alter the relationships in the cartridge's generator (usually because the suspension is stiff enough to resist the skating forces) and so you would HEAR no difference with or without AS applied. Nevertheless, with no AS applied, the inner groove wall of the record would wear faster than the outer groove wall ;-)
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Dertonarm, my explanations are based on the Laws of Mechanics introduced by Sir Isaac Newton July 5, 1687, and which remain true and in use to this day. You can point to all the little nuances which you assert would have an effect on the basic design, but they are so small as to be irrelevant. You seem to want to make things as complex as possible, which makes any useful solution impossible of course. Nonsense!
As I said before, I have no problem with your expressing your ideas, but remember, without any scientific proof or technical underpinnings, that's all they are: thoughts, and whimsy ;-)
Anti skating in it's basic form is a very useful concept, if only to prevent uneven record wear and reduce surface noise in the left channel. To those who think anti-skating is of no value, or just TOO COMPLICATED to implement (dear, dear!), I say, "don't worry, be happy" or better yet, get a 16" tonearm with no offset ;-) |
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! |
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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