All Anti-skating mechanisms are wrong!
- Thread starter ear4audio
- Start date
AvFan
Super Member
For the most part I don't worry about it either on my XB but I did detect some skating with my Grado cartridge. Marc recommended the tonearm wire twist to put a little AS force on the arm. It did the trick.
Is why sometimes I wanna go back to R-R tape--out of theTWENTY-ONE items mentioned to "worry about"---only FIVE of those would apply to a QUALITY machine.And even of those 5 items,probably only TWO would be a repetitive (real-time) issue.Azimuth-set ONCE.Alignment-once in a blue moon.Wow and flutter-mine get .03-04%,INAUDIBLE.and with records--don't forget another major headache---room-induced vibrations.Tape is immune to that.
In summary,
A. The stylus on a traditional turntable wants to "skate" towards the center of the record.
B. How hard it wants to skate is proportional to how far it is from the center of the record.
C. If you don't counteract this force the stylus tip will higher on the inside of the groove than on the outside.
D. This will result in:
D1. An imbalance between the audio response between the two channels.
D2. Increased wear on the inside of the groove wall.
E. You counteract the skating force with anti-skate (spring, weight, electronic mechanism, etc.) which, ideally, varies in proportion to how far the stylus is from the center of the record.
ALL ANTI-SKATING MECHANISMS ACHIEVE THEIR INTENDED PURPOSE BUT ARE NOT PERFECT!
... then again ... they don't call this the disinformation superhighway for nothin'
Caveat: I'm an engineer and can accept "close enough" - if you are physicist well .....
Manfred/lini - chime in when I get it wrong.
I could just wave my hands here and say "Believe!" but ....
Adjusting anti-skate:
Most traditional (modern/vintage) turntables are equipped with a device that will, in parallel with a tracking force adjustment device, prevent the stylus tip from skating across a record. You adjust the this so-called anti-skate device in concert/parallel with your tracking force adjustment to achieve this objective. The people at Technics/JVC/Pioneer/Sony/etc./etc. were pretty intelligent and figured this stuff out for us. I'm assuming that, in the olden days (antiques), you just pushed down really hard on the stylus to keep it from skating but that wasn't very kind to records nor was it very high fidelity.
So, just adjust as the instructions indicate and you should be good to go. If it's a spring based system on a vintage table you might run into a "worn" anti-skate spring (30, 40, 50, 60 years sitting there tensioned and it may lose some of it's "springyness".
In a more perfect world you could ignore the instructions and use a 1 kHz stereo test record and adjust your anti-skate at the outermost and innermost grooves to get proper balance between the channels or, actually, somewhere closer to the outermost groove since that's where the halfway point of the groove (lengthwise) exists.
What was the OP thinking?
Not sure what the OP got right. This business of centripedal force, maybe right in some frame of reference but, WRT to the stylus tip and the record surface not sure where it was going.
At least it made me think through the whole process rather than assuming that the manufacturers got it right.
The gory details!
Apologies to those who fully understand this but just thinking it through.
(Note: if I was a better electronic artist I'd provide drawings but I suck) so you will have to visualize.
The objective is to balance the skating force with anti-skate so the forces acting on the stylus tip (between the left and right groove of the record) are balanced and you get balance between the L/R channel audio and wear.
Why does the stylus want to move to the center of the record (skate)?
Well, for it to want to move there has to be a force acting on it.
If we look at the forces acting on the stylus tip there should be:
(1) The force (weight) applied by whatever "tracking force" is being applied - vertical tracking force (VTF)
(2) The force due to friction as the tip drags across the vinyl grooves - I'll make this up - "tangential (with respect to the record groove) tracking force" or TTF
There are also acceleration forces as the stylus tip follows the deviations in the groove wall (music) but, for the purposes of anti-skate, I only consider their effects on the tangential tracking force as the increase apparent friction between the stylus tip and the record surface.
The TTF is the result of the vertical tracking force (VTF) and the dynamic coefficient of friction between the stylus tip and the vinyl (mu): TTF = VTF x mu. TTF acts "along" or tangential to the record groove.
All of these forces can be variable. The VTF will change if the record that isn't perfectly flat. The TTF will increase as you increase VTF or increase friction (loud low frequency passages). Conversely, TTF will decrease as you decrease VTF or decrease friction (quiet passage or between songs on lp).
Think sliding a box across a surface, as you increase the weight (eg. VTF) or the surface gets rougher (increase mu) the force required to slide the box (TTF) increases proportionally. (won't get into static and dynamic - we're dynamic). Guess you could consider a box that is already sliding and add weight to it - it will slow down. Or, better yet, press harder on your car brake pedal and F1 increases and increases the rate at which you slow down.
I'm getting there.
Now, change perspective from the sylus tip to the tonearm pivot. The stylus is connected to the cartridge which is connected to the tonearm which rests on that pivot.
If you consider a traditional turntable and draw a line tangent to the record groove at the beginning of a record (lp) you will see that it doesn't intersect with the tonearm pivot but passes "outside" the pivot by some distance "R". Since TTF is acting along this line and it doesn't intersect with the pivot you end up with a force acting on an imaginary arm of length R which will push the stylus inwards towards the center of the record
Fskating = TTF * R
Been a long time - think it's Newton's third law. For every action/force there is an equal but opposite action/force or the system will accelerate.
Unless there is something else keeping the tonearm from pivoting the only thing stopping it is the inner groove wall "pushing" on the stylus tip - this is bad.
As the stylus moves towards the center of the record the offset (R) between the tangent line to the groove and the pivot of the tonearm gets smaller.
As a result, the skating force (Fskating=TTF * R) also gets smaller.
Side note: the stylus won't skate if you put enough VTF on it but it won't work sound good and it will increase wear on your record. A U.S. penny is about 2.5 grams. You want a little VTF as possible (as the cartridge/stylus designer wanted) but as you reduce VTF you increase the likelyhood that the stylus tip won't follow the groove and physically skate across the record towards the center.
If we go back a bit, we had defined TTF as being a function of VTF and the dynamic coefficient of friction (mu).
Fskating = TTF * R = VTF * mu * R
If you increase VTF then the Fskating will also increase.
To keep the force on the stylus balanced (between left and right sides of the groove) we need to apply the anti-skate (Fantiskate).
The anti-skating force will need to vary in direct proportion to the skating force, Fs, (larger at the beginning of the record and progressively smaller as the stylus moves towards the center).
Since it's most common, consider an anti-skating spring.
The force applied by a spring, Fspring, is a function of its "stiffness" K and how far from its relaxed position it is, X, so Fspring = K * X.
I don't have one open now and haven't really looked at it but I believe the spring in a common Technics turntable is a leaf spring (flat metal piece) where X is actually the spring deflection from its relaxed position.
If you have another arm connected to the tonearm pivot down below the turntable and put this spring against it will counteract the skating force based on how much it is deflected.
If set up correctly the spring would be fully relaxed when the stylus was at the center of the record and apply increasing force as you move away from the center.
In reality, you turn the anti-skate dial to a setting that the manufacturer determined based on the tracking force and hope that you get balance that is our final objective.
Fskating = Fantiskating
or
VTF * mu * R = Kspring * X (dial setting).
You could also have Fantiskating = m * g * R where m is the mass of a little hanging doo-dad attached to a separate anti-skate arm at the pivot where R is the distance from the pivot center to the attachment point (g is gravity).
Of course, you could also get a linear tracking turntable but what would be the fun of that?
Or, you could have my JVC QL-Y5F where it senses tonearm position and uses electromagnets attached to the tonearm to counteract skating forces and a separate set of sensors/electromagnets to adjust VTF "on the fly" - think warped record. Talk about a nightmare when it fails eh?
Hopefully I didn't make too many errors here. At least I sorta-kinda understand this all now I think.
A. The stylus on a traditional turntable wants to "skate" towards the center of the record.
B. How hard it wants to skate is proportional to how far it is from the center of the record.
C. If you don't counteract this force the stylus tip will higher on the inside of the groove than on the outside.
D. This will result in:
D1. An imbalance between the audio response between the two channels.
D2. Increased wear on the inside of the groove wall.
E. You counteract the skating force with anti-skate (spring, weight, electronic mechanism, etc.) which, ideally, varies in proportion to how far the stylus is from the center of the record.
ALL ANTI-SKATING MECHANISMS ACHIEVE THEIR INTENDED PURPOSE BUT ARE NOT PERFECT!
... then again ... they don't call this the disinformation superhighway for nothin'
Caveat: I'm an engineer and can accept "close enough" - if you are physicist well .....
Manfred/lini - chime in when I get it wrong.
I could just wave my hands here and say "Believe!" but ....
Adjusting anti-skate:
Most traditional (modern/vintage) turntables are equipped with a device that will, in parallel with a tracking force adjustment device, prevent the stylus tip from skating across a record. You adjust the this so-called anti-skate device in concert/parallel with your tracking force adjustment to achieve this objective. The people at Technics/JVC/Pioneer/Sony/etc./etc. were pretty intelligent and figured this stuff out for us. I'm assuming that, in the olden days (antiques), you just pushed down really hard on the stylus to keep it from skating but that wasn't very kind to records nor was it very high fidelity.
So, just adjust as the instructions indicate and you should be good to go. If it's a spring based system on a vintage table you might run into a "worn" anti-skate spring (30, 40, 50, 60 years sitting there tensioned and it may lose some of it's "springyness".
In a more perfect world you could ignore the instructions and use a 1 kHz stereo test record and adjust your anti-skate at the outermost and innermost grooves to get proper balance between the channels or, actually, somewhere closer to the outermost groove since that's where the halfway point of the groove (lengthwise) exists.
What was the OP thinking?
Not sure what the OP got right. This business of centripedal force, maybe right in some frame of reference but, WRT to the stylus tip and the record surface not sure where it was going.
At least it made me think through the whole process rather than assuming that the manufacturers got it right.
The gory details!
Apologies to those who fully understand this but just thinking it through.
(Note: if I was a better electronic artist I'd provide drawings but I suck) so you will have to visualize.
The objective is to balance the skating force with anti-skate so the forces acting on the stylus tip (between the left and right groove of the record) are balanced and you get balance between the L/R channel audio and wear.
Why does the stylus want to move to the center of the record (skate)?
Well, for it to want to move there has to be a force acting on it.
If we look at the forces acting on the stylus tip there should be:
(1) The force (weight) applied by whatever "tracking force" is being applied - vertical tracking force (VTF)
(2) The force due to friction as the tip drags across the vinyl grooves - I'll make this up - "tangential (with respect to the record groove) tracking force" or TTF
There are also acceleration forces as the stylus tip follows the deviations in the groove wall (music) but, for the purposes of anti-skate, I only consider their effects on the tangential tracking force as the increase apparent friction between the stylus tip and the record surface.
The TTF is the result of the vertical tracking force (VTF) and the dynamic coefficient of friction between the stylus tip and the vinyl (mu): TTF = VTF x mu. TTF acts "along" or tangential to the record groove.
All of these forces can be variable. The VTF will change if the record that isn't perfectly flat. The TTF will increase as you increase VTF or increase friction (loud low frequency passages). Conversely, TTF will decrease as you decrease VTF or decrease friction (quiet passage or between songs on lp).
Think sliding a box across a surface, as you increase the weight (eg. VTF) or the surface gets rougher (increase mu) the force required to slide the box (TTF) increases proportionally. (won't get into static and dynamic - we're dynamic). Guess you could consider a box that is already sliding and add weight to it - it will slow down. Or, better yet, press harder on your car brake pedal and F1 increases and increases the rate at which you slow down.
I'm getting there.
Now, change perspective from the sylus tip to the tonearm pivot. The stylus is connected to the cartridge which is connected to the tonearm which rests on that pivot.
If you consider a traditional turntable and draw a line tangent to the record groove at the beginning of a record (lp) you will see that it doesn't intersect with the tonearm pivot but passes "outside" the pivot by some distance "R". Since TTF is acting along this line and it doesn't intersect with the pivot you end up with a force acting on an imaginary arm of length R which will push the stylus inwards towards the center of the record
Fskating = TTF * R
Been a long time - think it's Newton's third law. For every action/force there is an equal but opposite action/force or the system will accelerate.
Unless there is something else keeping the tonearm from pivoting the only thing stopping it is the inner groove wall "pushing" on the stylus tip - this is bad.
As the stylus moves towards the center of the record the offset (R) between the tangent line to the groove and the pivot of the tonearm gets smaller.
As a result, the skating force (Fskating=TTF * R) also gets smaller.
Side note: the stylus won't skate if you put enough VTF on it but it won't work sound good and it will increase wear on your record. A U.S. penny is about 2.5 grams. You want a little VTF as possible (as the cartridge/stylus designer wanted) but as you reduce VTF you increase the likelyhood that the stylus tip won't follow the groove and physically skate across the record towards the center.
If we go back a bit, we had defined TTF as being a function of VTF and the dynamic coefficient of friction (mu).
Fskating = TTF * R = VTF * mu * R
If you increase VTF then the Fskating will also increase.
To keep the force on the stylus balanced (between left and right sides of the groove) we need to apply the anti-skate (Fantiskate).
The anti-skating force will need to vary in direct proportion to the skating force, Fs, (larger at the beginning of the record and progressively smaller as the stylus moves towards the center).
Since it's most common, consider an anti-skating spring.
The force applied by a spring, Fspring, is a function of its "stiffness" K and how far from its relaxed position it is, X, so Fspring = K * X.
I don't have one open now and haven't really looked at it but I believe the spring in a common Technics turntable is a leaf spring (flat metal piece) where X is actually the spring deflection from its relaxed position.
If you have another arm connected to the tonearm pivot down below the turntable and put this spring against it will counteract the skating force based on how much it is deflected.
If set up correctly the spring would be fully relaxed when the stylus was at the center of the record and apply increasing force as you move away from the center.
In reality, you turn the anti-skate dial to a setting that the manufacturer determined based on the tracking force and hope that you get balance that is our final objective.
Fskating = Fantiskating
or
VTF * mu * R = Kspring * X (dial setting).
You could also have Fantiskating = m * g * R where m is the mass of a little hanging doo-dad attached to a separate anti-skate arm at the pivot where R is the distance from the pivot center to the attachment point (g is gravity).
Of course, you could also get a linear tracking turntable but what would be the fun of that?
Or, you could have my JVC QL-Y5F where it senses tonearm position and uses electromagnets attached to the tonearm to counteract skating forces and a separate set of sensors/electromagnets to adjust VTF "on the fly" - think warped record. Talk about a nightmare when it fails eh?
Hopefully I didn't make too many errors here. At least I sorta-kinda understand this all now I think.
jsmiddleton4
Active Member
Yes it’s an old thread. But it will always be permanently relevant. I use a blank acrylic record. Even if its not 100% accurate it is close.
JoeESP9
ESL's & tubes since 83
I also use a blank LP side to adjust and set anti-skating. Where I differ with many is, I set skating so that the arm moves slowly away from the spindle. I do this because I realize that tracking a groove increases whatever skating is inherent in the arm.
That's what I do-use a test record,and play the 1Khz track closest to the limits of the cartridges tracking ability--then adjust the anti-skate for equal and undistorted signal,viewing on my dual trace scope. As close to real-world conditions as I can get. Like I said--if a tape head is misaligned(azimuth),it does no physical harm,just a loss of highs that can be corrected by the turn of a screw. And it is not a moving object that is continually tilting and bobbing up-and-down and sideways,like a tonearm/cartridge combination.It stays fixed. When you think about it--it's a SHEER WONDER that music sounds as good on records as it does,considering how many pitfalls and errors and the actual level of crudity of the technology it really is!
I use the Tacet test record "Skating" track to adjust the anti-skate. It's pretty easy to use.
I used to do the "blank-groove" type of adjustment--until I read how that is rather inadequate under real-world conditions.When the stylus is "in the groove"(catchy phrase there),there is a WHOLE LOTTA shakin' goin' on -- a different set of dynamics at work,than a stylus sitting on top of a record's surface.You have the level of groove modulation,the difference of forces a (stereo) groove (in particular) puts on the stylus as it literally SHOVES the stylus around in a wild dance--which brings into place the mass-and compliance- of the stylus tip/cantilever assembly,and,by extension, the mass and resonance of the cartridge/tonearm assembly,the shape of the stylus,the tracking force applied to it,and the type of music being played.Rock,for example, has different modulations of the groove than Classical,with more sharp transients,and more heavily modulated throught the whole side of the album,while Classical,by and large is more heavily modulated toward the inner grooves,where the climax usually is.Or scattered throughout,here and there,and not usually all the way through,like much of rock and metal. So--even the type of musical genre you listen to,can affect the tracking,and thus antiskate settings of the particular record you play--something the "blank groove" setting does NOT take into account.
Doug G.
Lunatic Member
The mistake many make when arguing against the "blank surface" method is assuming there is little to no friction involved, so they insist it can't even be close. The stylus dragging on the surface, itself, creates friction as the diamond tip tries to cut a groove in the surface.
Now, this friction may not be equal to the friction of the stylus riding in a groove and, of course, ALL methods are a compromise but I believe it gets adequate anti-skate a lot closer than many claim.
Doug
Now, this friction may not be equal to the friction of the stylus riding in a groove and, of course, ALL methods are a compromise but I believe it gets adequate anti-skate a lot closer than many claim.
Doug
Furtheluva.....the scope.
Why didn't I think of that?
I use the scope to lay curves over each other for my cassette decks so the TT should have been obvious.
I don't really care about all the rest of the "antiskate" stuff guys go on about, I just want the sound to be "balanced". Laying two traces over each other has got to be about as close to that as you can get.
Thanks for helping kick my rusty old brain into moving again.
Peter Ledermann (Soundsmith) has a couple of good videos on anti-skating, tracking, etc.
As an addendum, the Tacet record has its anti-skating test track at varying modulation levels. You can then choose which level to best adjust your A/S value, for your particular setup.
As an addendum, the Tacet record has its anti-skating test track at varying modulation levels. You can then choose which level to best adjust your A/S value, for your particular setup.
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