Classic Cartridges

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Cressy Snr
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#31 Re: Classic Cartridges

Post by Cressy Snr »

Well, as far as my knowledge goes, it is the stylus that is being pulled inwards, not the cantilever or the arm. The cantilever cannot become displaced sideways in this case. If it does become displaced then your lateral arm bearing friction is too high and the bias is the least of your worries.
Trouble with anti-skate is that the inward force is constantly varying, with groove radius because its a spiral, and with recorded velocity, which exerts a constantly varying drag on the stylus. As with everything analogue, we have to find the approximation that works best for us.
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steve s
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#32 Re: Classic Cartridges

Post by steve s »

I never thought no anti skate would damage the cartridge, only that there may be slightly more sideways pressure on one side of the stylus.
I have a couple of anti skate less tone arms, one of which did run central and sounded great with a few 1960s cartridges
I've not used the decca professional yet, still deciding about getting the cartridge refurbed..
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vinylnvalves
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#33 Re: Classic Cartridges

Post by vinylnvalves »

It’s the tracking error that causes the sideways force, this is why with the longer tonearms, such as the 16” no bias is generally used, where the tracking error is less. The stylus path isn’t the same as the pivot of the tonearm due to the overhang so a resultant force is set up. Which is proportional to the VTF of the stylus. So lower tracking cartridges should have less problems, but they have more compliance in the cantilever. Whether the bias application method mimics the required force is another matter, a weight on a string cannot be more than a constant force, without eccentric cams. Other approaches can apply a varying force, such as Tom Fletchers weight on a pivoting wire... I modelled the arrangement some years back I will have to dig it out. Of course linear trackers don’t need antiskate but have other challenges of their own.
You could reduce the overhang and increase the tracking error to reduce the skating force.. however tracking error imho is more noticeable. Obviously conical styli are more tolerant to tracking error.
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Nick
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#34 Re: Classic Cartridges

Post by Nick »

I was not suggesting that there wasn't a force, I was questioning how it could create the first two effects that were suggested.
1) skew of the cantilever until that becomes permanent
2) misbalance between the left and right channels
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Ant
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#35 Re: Classic Cartridges

Post by Ant »

Have a look at the james kogen study on bias from 1967,
I think its called 'the skating force phenomenon
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vinylnvalves
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#36 Re: Classic Cartridges

Post by vinylnvalves »

I missed off the first line of my reply - the skating force is always there, Newtonian mechanics. If the stylus and tonearm pivot are common then the arm would accommodate everything assuming low friction bearings, and the stylus would sit in the bottom of the groove. So to answer question 1 As the pivots aren’t aligned offset by the overhang the resultant force has to be accommodated by the compliance in the cantilever skewing it. Answer to question 2.... not sure as any motion of the cantilever is picked up by both coils isn’t it? The only logic is it must be be setting up a wave where the amplitude of the side which is rubbing is larger than the side where the stylus is not following the contour of the track. ( waiting to be shot down in flames for a ladybird book answer :( )
Nick wrote: Wed Sep 30, 2020 12:28 pm I was not suggesting that there wasn't a force, I was questioning how it could create the first two effects that were suggested.
1) skew of the cantilever until that becomes permanent
2) misbalance between the left and right channels
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Nick
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#37 Re: Classic Cartridges

Post by Nick »

As the pivots aren’t aligned offset by the overhang the resultant force has to be accommodated by the compliance in the cantilever skewing it.
But if, there is a sideways force on the cantilever, why doesn't the arm just move to cancel it, in the same way as the arm is moved across the record by the groove. I can understand why the stylus sees a different force on the two sides, what I don't see is how this translates to a force on the cantilever that can't be removed by the arm moving in reaction to this force. The fact that it is suggested that bias applied at the pivot can be used to counter the force at the stylus seems to me to show the bending action won't happen at the cantilever.
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vinylnvalves
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#38 Re: Classic Cartridges

Post by vinylnvalves »

The friction force on the stylus is normal to the groove, as the tonearm pivot isn’t normal to the groove the additional force is set up. You will say isn’t this the case for linear trackers, the answer is yes, they have the same force but the linear bearing can move to accommodate it, in theory.
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#39 Re: Classic Cartridges

Post by Ant »

As far as i can see, the cantilever is not bent by the force, rather the groove moves to the left in the suspension bushing until the bush is fully compressed on the left hand side, which then pulls the arm in the same direction. In which case, the softer the bush, the more the cantilever can compress the bush in that direction, meaning the bigger the skew looks.
If this is the case, the cantilever should move back to the centre when there is no load on the stylus as that side of the bush should return to its original shape and re centre it.
With an old cart with a hardened old bush in it, it might not recentre if the bush has degraded over time
So the bias is working to balance the side force applied to the cantilever against the compliance of the bush
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Nick
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#40 Re: Classic Cartridges

Post by Nick »

The friction force on the stylus is normal to the groove, as the tonearm pivot isn’t normal to the groove the additional force is set up.
Yes, but if this force causes a twisting force on the pivot point of the cantilever (which is the only way I can see it causing a permanent deformation to the stylus when its at rest) if that twist can not be removed by the action of the arm turning on IT'S pivot, why would applying a force at the arms pivot, counter the force on the cantilever pivot.
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Nick
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#41 Re: Classic Cartridges

Post by Nick »

You will say isn’t this the case for linear trackers
Well, to be picky. in the case of a linear tracker, the inner wall is moving slower past the stylus than the outer one because of the smaller radius, so the friction on the inner and outer grove walls will be different. (see fixed rear axle cornering to use a car analogy).
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Cressy Snr
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#42 Re: Classic Cartridges

Post by Cressy Snr »

I did something silly: I put the old stylus back in the cartridge, placed my finger on the stylus tip, lifted the arm with the finger on the stylus then moved the arm towards the centre spindle.

As I expected, there was no sideways deflection of the cantilever; there can’t be, the arm moves because the stylus moves it. It cannot skew itself, physics does not allow it. It would be like standing on a pair of roller skates with a horizontal tin bath full of water on your back, lowering a running outboard motor into the bath and moving yourself forwards at 30 knots. The only way the cantilever could skew under inward force would be if the horizontal bearing was locked in place, or had sticky movement.
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Nick
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#43 Re: Classic Cartridges

Post by Nick »

Cressy Snr wrote: Wed Sep 30, 2020 2:29 pm I did something silly: I put the old stylus back in the cartridge, placed my finger on the stylus tip, lifted the arm with the finger on the stylus then moved the arm towards the centre spindle.

As I expected, there was no sideways deflection of the cantilever; there can’t be, the arm moves because the stylus moves it. It cannot skew itself, physics does not allow it. It would be like standing on a pair of roller skates with a horizontal tin bath full of water on your back, lowering a running outboard motor into the bath and moving yourself forwards at 30 knots. The only way the cantilever could skew under inward force would be if the horizontal bearing was locked in place, or had sticky movement.
That's part one of my argument, but if instead of placing the stylus on your finger tip, you grabbed the stylus tip with a pair of pliers pointing up, and twisted them, then you would bend the cantilever and the arm cant move to prevent it as it would need to move in a direction it can't. That's VinylyAndValves argument which I accept.

But my point is if the twisting as described can bend or deform the stylus assembly (which the pliers show it could) then adding an extra force at the arm pivot (from the bias) can't prevent that from happening.
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izzy wizzy
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#44 Re: Classic Cartridges

Post by izzy wizzy »

The inward skating force exists on a flat record. So if the inward skaing force is greater then the inward motion of the groove, I can imagine the cantilever being dragged in more than it should. Likewise too much antiskate holding it back. Or maybe I have a vivid imagination.

I've just got a new Analogue Productions test record I want to try but haven't got around to it yet.
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Nick
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#45 Re: Classic Cartridges

Post by Nick »

izzy wizzy wrote: Wed Sep 30, 2020 6:09 pm The inward skating force exists on a flat record. So if the inward skaing force is greater then the inward motion of the groove, I can imagine the cantilever being dragged in more than it should. Likewise too much antiskate holding it back. Or maybe I have a vivid imagination.

I've just got a new Analogue Productions test record I want to try but haven't got around to it yet.
I would have thought that for the average record the sideways force from the spiral would be less than any out of centre content.
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