Quite a few romantic and interesting views of AS, carts, and arms here, but they are quite confusing and some, just plain wrong. Virtually all carts, both MM and MC with a conventional cantilever, have a rubber suspension damper. This is for obvious reasons and to control high frequency response. The natural HF rise is controlled by damping. This trades off imaging/phase linearity for FR, but it's a necessary compromise and prevents ear bleed and excessive cantilever excursion.
Carts are not preloaded with cantilevers to the left(?). Perhaps this can be verified with a cart designer like VdH or J Carr. Cantilevers should be close to centered when at rest. If your cart came with the cantilever SLIGHTLY off-centered, you can align to the cantilever rather than the body. A linear arm exhibits no skating because there is no offset. The stylus/cantilever should be free to track in either direction. there is no pre-canting.
Yes, AS is applied to the arm near the bearing, while skating occurs at the stylus. But it's the arm mounting and its offset that causes skating. That is the relationship between the plane of the cantilever and that of the stylus to bearing. Just because groove velocity and arm position have an affect on skating, doesn't change the basic cause or solution.
AS force has the affect of reducing VTF, slightly. This could have something to do with perceived SQ degradation. I haven't experienced this. A minimal value of AS would tend to center the image and balance the channels. If you don't have a scope or appropriate software, a tape deck with a good display will show this. Just because optimal value of AS is a compromise, doesn't mean you should throw the baby out with the bath water. My 2 cents anyway.
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Tonywinsc, thanks for the explanation. It corroborates with my experiences, we must listen. The downside of using our ears is that errors in other areas such as VTA, optimum tracking weight can influence what we hear and the process for dialing in a cartridge in all set up parameters is iterative in nature. New cartridges in particular or rebuilt cartridges should be rechecked for VTA, tracking and antiskating force after running in for a few weeks/months. |
The main friction is between the vinyl and the stylus, but yes, groove modulation adds additional drag to the stylus and therefore creates additional AS force as Lewm points out. I found some data on the internet a few months ago. Research was done on various types of vinyl and shellac records decades ago. The coefficient of friction varied from 0.2 to 0.6. That coefficent number would have a direct impact on AS force along with groove modulation. I believe that most modern vinyl records have a fairly consistent coefficient of friction- probably in the 0.2-0.25 range, but that is only a conclusion based on that research data. Friction force is your normal force, eg. 2 grams, times the coefficient of friction. So if the coefficient is 0.2 then the friction force would be 2 grams times 0.2 or 0.4 grams and the AS force will be a component of that friction force. AS force is going to be friction force times the sine of the angle between the stylus and tonearm pivot, I believe. While tonearms may have AS force calibrated in grams for the sake of simplicity, the real AS force acting on the stylus is much smaller than that. Someone correct me if I am wrong with that conclusion. But that is why you really have to dial in AS force by listening rather than just setting it and forgetting it. The tonearm makers have to use average values while stylus angles, horizontal compliance and friction forces can vary which have a direct impact on AS forces. |
Tony, When the stylus is tracking an actual LP, the friction that causes skating has everything to do with the grooves. |
Tony...as a fellow left-hander, I sympathise :)
You must have nerves of steel m8! ("DJ scratching" - in the "safe" direction - on your protractor :) :)
I'm usually a quivering wreck just making routine adjustments :)
It reminds me of NSGArch's repeated appeals that platters be secured during cart alignment to avoid any accidental cantilever reversals. Sadly, few of us - including myself - take this simple precaution (I will next time, I promise!) :)
On my turntable, I've noticed that after deceleration the platter comes to rest with a final small oscillation (backwards-forwards, about 1mm or so, for a split second). Perhaps wrongly, I attribute this to the rubber belt stretching alternately either side as it grapples with the heavy platter's inertia...
It doesn't encourage the idea of not being present during a power failure while a record is spinning! :) |
I just uploaded a couple of pictures of my phono cartridge for illustration on my
system page. One shot shows the cantilever in the free state and resting low
and to the right. btw- I said that wrong in my previous post about being down
and to the left. (I'm left handed. We get our rights and lefts mixed sometimes.)
The other shot shows the cantilever cued onto the record. I tried to get a good
angle. It shows the cantilever very nearly centered. The angle of the camera
shows it off a little, I think, but in reality it looks centered.
I usually end up at the high end of the VTF tolerance from the manufacturer and
my AS force set a little less than my VTF. I also keep the stylus clean with a
wetted stylus brush. That is key to maintaining good tracking.
I have a 45 rpm direct to disc record of the Appassionata that is very
challenging for any tonearm/cartridge. It is very dynamic. Once my old Koetsu
was worn I had to stop playing it. It could not track the record on the
crescendos. This cartridge tracks it perfectly from beginning to end and the
peaks do not come until the end. It gives me goosebumps. |
I can't say for certain, but I think that the stylus/cantilever pulls the tonearm along, so if those loads are balanced properly then it is going to be centered. I had a buddy who used the ET2 linear arm on his VPI table. It took him a few years to figure it out, but I recall him telling me that he had to level his table a certain way- slightly downwards, I think and it would track perfectly. He also said that he had to keep the air bearing tube perfectly clean. It would sound grainy if the tube had any dust on it.
Also, cartridges are different. I think some may have a different compliance in the horizontal direction than in the vertical direction, ie. the cantilever may be stiffer in the horizontal direction. So you may not see as much deflection horizontally on some cartridges. My Benz cartridge has what looks like an o-ring on the cantilever for a suspension. So the bias downward and slightly to one side is very apparent. But when riding on the vinyl it is centered. The cantilever goes through a hole in the housing which makes a good reference for seeing the cantilever position.
When I am setting up my tonearm and setting the HTA, I have the protractor on top of a record so that the arm is at the right height. Anti-skating is set to zero. I pull on the platter while viewing the protractor alignment. This applies friction drag to the stylus and sets the cantilever in the "as playing" condition. I can see the difference in the protractor alignment when turning the record slowly versus the record remaining stationary. (The record slides along under the protractor). |
Tony, interesting post. Regarding pre-loading and non-pivoted arms : does this mean that the cantilever will be permananently skewed when a cart is fitted on linear tracking arms? |
Skating is a component of the force vector generated by the friction between the stylus and the vinyl. If the stylus on a pivoting tonearm is not in line with the center of the pivot bearing, then the x and y components of the friction force try to pull the stylus out of the tonearm, ie. away from the bearing and also left (towards center) of the tonearm because the stylus is to the left of the pivot bearing. Linear tracking tonearms have no anti-skating adjustment because the stylus is in-line with the sliding arm tube bearing. It has nothing to do with the grooves. The tonearm will be pulled to the center of the record even with a blank vinyl disc. Since the counter force, or anti-skating force must be applied at the pivot of the tonearm, cartridge manufacturers apply a bias or prelaod to one side of the stylus/cantilever suspension just like they apply a preload to the suspension in the vertical direction. That is so when the cartridge is cued onto the record, the VTF load and AS load center the stylus in its suspension- as long as those loads are to design intent. Try to look at the stylus cantilever on your cartridge sometime when it is in the free state. It should look offset down and left. Then cue it onto a record and it should look centered and left. Now start the record turning and it should look centered. That is if the loads are adjusted within the range of the cartridge manufactureres' specifications. |
Lew,
I agree with the elaborations in your post. For clarity, the only point of my (admittedly over-simplified) analogy was to illustrate this fact:
- skating forces act (first) upon the stylus
- anti-skating devices act (first) upon the tonearm
This seems non-controversial, obvious even, but this difference must be mediated somewhere. Practically speaking, the only non-rigid component between the stylus and the tonearm is the suspension in the cartridge. That's where imbalances between skating and anti-skating forces will be dampened. To the extent such dampening occurs, sonics will be affected.
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Yes I agree with Lewm that AS should be applied, with due care.
In my experience as a dealer and 30 years of audio I have found that very few TT's provide a platter surface and armboard surface that are congruent, that is if the platter is level then the armboard isn't. How many of you have run dial calipers over the platter/armboard to measure this and corrected it.
If you dont run a unipivot or arm that includes adjustability for levelling the horizontal bearings, then you have in inward or outward force applied to the cartridge before you even start.
It is entirely logical to me that each arm may require different AS levels due to differing arm geometry, cartridge alignment preferences and bearing friction levels.
I think the most common issues with applying AS that I have seen are :
Compensating for an out of level arm relative to platter surface.
Compensating for output level imbalances between channels, either in the cartridge or system ( or even the audiophile's ears ! ).
Following the manufacturers recommendation without listening.
I can pass on my experience with the Ikeda MC which has no cantilever. The diamond is mounted on a hoop which is at a rightangle to the groove. The hoop is held by a string which prevents the hoop from being pulled out when playing. The hoop has a little compliance built in.
http://www.avguide.com/blog/high-end-audio-japan-part-five-analog-ikeda-sound-lab
This cartridge requires AS on every tonearm I have tried it on, both unipivots and gimbal bearings. No antiscate the you get mistracking, channel imbalance and compressed soundstage and harmonic structure. Optimum AS applied yields no mistracking, no channel imbalance and most importantly maximum soundstage and harmonic structure.
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"As soon as I think I'm out, they pull me back in..." (Michael Corleone)
Doug, I think the genesis of the skating force is a bit more complex than simply that of a force pulling the stylus toward the center of the LP (or the spindle). Skating force is due to friction of the stylus in the groove, I think we all agree. The actual direction of the main force vector generated by friction is more toward the left rear of the turntable (exact direction depends upon headshell offset angle, and other factors like length of tonearm and position of the stylus on the LP surface). The reason we "see" it as a centripetal-ish force or a force pulling the tonearm inward in its arc, is because that is the only motion permitted by the tonearm pivot, due to tonearm stiffness. Similarly, AS force creates a vector mostly toward the outer and rear, because of headshell offset (and above). The combination of skating and AS vectors, if AS is theoretically perfectly chosen to equal skating force, would be to pull the stylus and cantilever back into the cartridge body. (Maybe that could cause the dampening to which you refer.) I think that the reason we observe bent cantilevers is that in most cases there is too much or too little AS. Anyway, that's my take on the subject. You and others have made me an AS minimalist but not a nihilist. |
"Pre-loaded" implies to me that there is a load on the cantilever independent of the stylus being played in the groove. Sorry. By "pre-loaded" I mean that A/S devices pressure the cantilever against the suspension as soon as the stylus locks into a groove. I could have called this "loading" rather than "pre-loading" It seems to me that there is no load on the cantilever until it hits the groove. Agreed. If the record is not spinning, with no anti skating force, the load is only vertical if the stylus is in
the groove. Correct. You write: The pre-loaded force is "pressuring it (the cantilever) against the elastic suspension reducing its freedom to respond to groove transients." My question is: Isn't this exactly what skating force does if you don't apply anti-skating force? It seems to me that skating force is also "pressuring it against the elastic suspension reducing its freedom to respond to groove transients." Skating forces do load the cantilever against the suspension but anti-skating devices do not counteract that loading, they actually increase it. Imagine that your hands are very small. Grab the STYLUS with your L hand and pull it toward the record center. That's skating and yes, you can feel the squidginess of the suspension being compressed by the far end of the cantilever as you tug. Now grab the TONEARM with your R hand and pull it away from the record center. That's anti-skating. If the stylus is locked into a groove you'll feel a similar squidginess as the cantilever compresses the suspension. Now pull simultaneously with both hands (which represents playing a record with A/S engaged). If you pull equally hard with each hand the pressure you apply to the suspension is doubled. It's that much closer to "bottoming out". While you have these tiny hands, try shifting your R hand to the stylus and pulling it outward just as your L hand is pulling it inward. What happens to the cantilever/suspension interface ? Nothing! No squidginess. The two forces are now aligned and precisely oppose each other. That's how a perfect anti-skating device would work. It would negate skating forces without effecting cantilever freedom. Of course nobody has built such a device and it's unlikely anyone ever will. The compromises necessitated by real-world design considerations mean that A/S devices pull on the tonearm while skating forces pull on the stylus. Result: increased dampening of the cantilever (squidginess). *** As to what you hear in your system vs. what we hear in ours, every system differs and the listener's ears must be the judge, as we both keep saying. Your cartridge, tonearm and electronics are quite different to ours. It's no surprise they act differently with regard to A/S. |
Doug, I agree with your comment that one should fine tune his setup by
listening. However, there is an aspect to this that you could perhaps clarify
for me.
I am confused by what you mean by "pre-loading". "Pre-
loaded" implies to me that there is a load on the cantilever independent
of the stylus being played in the groove. This is not the case. The load is on
the arm, not the cantilever once anti skate is applied. It seems to me that
there is no load on the cantilever until it hits the groove. If the record is not
spinning, with no anti skating force, the load is only vertical if the stylus is in
the groove.
With anti skating force applied, once the stylus hits the groove, a horizontal
load then reaches the cantilever and pushes against the groove wall. If the
record is spinning an additional horizontal load occurs in the opposite
direction. I agree that these loads are constantly changing and it is difficult or
impossible to make them equal and opposite.
You write: The pre-loaded force is "pressuring it (the cantilever) against
the elastic suspension reducing its freedom to respond to groove
transients." My question is: Isn't this exactly what skating force does if
you don't apply anti-skating force? It seems to me that skating force is also
"pressuring it against the elastic suspension reducing its freedom to
respond to groove transients."
I have tried zero and very little anti skate force on my arm and I've come to
prefer using the recommended setting from the manufacturer. I actual hear
better dynamics and more low level detail. I guess in the end, fine tuning by
listening is the best approach. |
Dear Lew, this has nothing to do with 'skating' but probable well with 'bias'. Groucho invented the 'principle of the variable principles' which become the principle of the American foreign policy. Groucho:" if you don't like my principles I have other ''... |
I was really surprised at how much more depth there was to the soundstage and greater subtle details. I was then gobsmacked by the discovery that I had forgotten to re-attach the bias weight thread! Applying Lateral Bias seems to compromise performance elsewhere, true? Very true, as Harry at VPI has always maintained and as I and others have described here many times. Pre-loading the cantilever by pressuring it against the elastic suspension reduces its freedom to respond to groove transients. Result? Reduced dynamics and smothering of lower level details... just as you described. Congratulations on making the discovery for yourself... a perfect example of what I and many others have always maintained: fine tune your setup with the instrument that really matters, your ears! *** AS is a compromise because the amount of skating force your stylus sees at any given moment is constantly changing. There can be no "perfect" setting and chasing after one, by whatever method, is a quest without a destination. For example, setting AS with a test track optimizes the rig for playing that test track. That's ideal, if that's all you play. As soon as you play music the conditions the stylus sees are different, the amount of skating force it sees is different and that "tested perfect" AS setting just became irrelevant. The best record for adjusting AS is the one you're listening to. With some carts when listening critically I've adjusted AS from one LP to the next. Fortunately, my present carts sound best with no AS at all, so that's how I play. But YMMV applies here more than almost anywhere in audio. Keep playin'! Keep learnin'! |
Like Groucho said about Doris Day, "I knew her before she was a virgin." |
And from the female opera singers Callas is the best also for the antiskate adj. Even those who hate female opera singers need to endure only about 4 cm of the inside groove. |
All skin and bones and no meat, which is pretty much what you get when the antiskate is out. I use female opera singers for checking anti skate, I have a couple of records that wont track if its out. |
"Like a virgin". Not the same thing ;-) |
I thought Madonna was a virgin. |
What Fleib and Audiofeil said. But I'd rather do this topic again than Madonna. |
Amount of AS is necessarily a compromise, but with a pivot type arm there's going to be skating. Amount of skating depends on more than just VTF. It increases with stylus velocity and steeper offset angle. It is caused by offset angle - the plane of the cantilever is extended off to the side, rather than aimed at the pivot as in a linear type arm.
So set your AS for "normal" loudness of most of your listening fare, not highest velocity on a test record. Offset increases as the stylus nears the center of record. Too little AS could add to inner groove distortion. Amount of AS is a compromise, but not a myth. Channel imbalance is readily seen on a scope or with newer software available. Carts with long cantilevers - skating can be observed visually if viewed from directly in front of cart while playing. Either the cantilever is almost centered relative to the body, or it's off to one side or the other. |
Wow, setting anti-skate by scope? I'm sure it produces great results but did manufactorers really expect customers to calibrate at this level? |
the anti skate required is a function of the tone arm and cartridge combination. It cannot be correctly set by matching the tracking weight. A test record with oscilloscope is the best method to set tracking pressure and antiskate. the sine wave will show deformity until both are correctly adjusted. If you do not have an oscilloscope, listening to the test tones for uneven distortion can approximate the correct antiskating.
Incorrectly set antiskating will cause 1 side of the stylus to wear out sooner than necessarry. |
I use no anti skate with my zyx Universe. Info from posters here on Audiogon had much influance on trying none. I have tried it with the Triplanar with slight differences but nothing that I could say that I could dial in. With the Raven 10.5 I got bigger differences but again nothing I could dial in. No anti skate works best with the Universe on two arms. Just one guys experience.
TD |
Search the archives.
This topic has been done more times than Madonna. |
Record playback involves many compromises, but anti-skating (or lateral bias) is one of the biggest. Following the turntable manufacturers instructions for setting anti-skating often results in far more lateral force than what is needed.
If you want to experiment with it, add the very smallest amount of weight back (you can even try a lighter weight than supplied with the table), and gradually increase it while carefully listening.
Your VTF is very light which would normally call for a smaller anti-skating force, but you may want to also increase the VTF in small increments into the upper ranges of the cartridge manufacturers recommended settings until the combination of settings results in the most pleasing sound.
Some turntables actually work best with no anti-skating. |
