Classic Cartridges

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izzy wizzy
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#46 Re: Classic Cartridges

Post by izzy wizzy »

Nick wrote: Wed Sep 30, 2020 6:22 pm
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.
Maybe my explanation/thoughts weren't well expressed. If the skating force is greater than the travel due to groove pressure and the anti skate force, then the cart will sit on the inside of the groove and if the anti skate is more than the inward skating force. then it will sit on the outer groove wall. Off centre is never good but a reality unless you have a Nakamichi IIRC from way back that fixed it.
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Nick
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#47 Re: Classic Cartridges

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But unless its mistracking the stylus should be in contact with both walls at all times.

The force created by the spiral will be tiny, and as Stave said, removed by rotation at the pivet point. The skating force is a result of the stylus not being perfectly parallel with the grove walls because of the offset from the perfect position so the stylus is in line with a right angle between the line from the centre of the record and the stylus (or in other words parallel with the groves).
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#48 Re: Classic Cartridges

Post by izzy wizzy »

I thought skating force didn't need grooves. It's an inward force due to overhang. Anti skate counters this so the stylus has even pressure on both walls. I set mine on a blank part of the record at the moment. Maybe I don't understand it.
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#49 Re: Classic Cartridges

Post by Nick »

It doesn't. I just used the grove as the reference for the position when there would be no positional error so no force in my description. Its still true if you remove the grove.
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#50 Re: Classic Cartridges

Post by vinylnvalves »

To add further enlightenment (confusion) https://www.analogplanet.com/content/ev ... ting-wrong
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#51 Re: Classic Cartridges

Post by izzy wizzy »

vinylnvalves wrote: Thu Oct 01, 2020 6:51 am To add further enlightenment (confusion) https://www.analogplanet.com/content/ev ... ting-wrong
That helps thanks. As I read it, it's overhang that causes skating not offset.
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#52 Re: Classic Cartridges

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izzy wizzy wrote: Thu Oct 01, 2020 7:15 am
vinylnvalves wrote: Thu Oct 01, 2020 6:51 am To add further enlightenment (confusion) https://www.analogplanet.com/content/ev ... ting-wrong
That helps thanks. As I read it, it's overhang that causes skating not offset.
Well, its tracking error, which is what I was trying to explain with the right angle. Giving up on my original point about bending the cantilever the main point being is that the optimal bias will depend on the cartridge setup, the stylus friction, so profile, and the tracking force, So just setting it on the dial based on tracking force is almost certainly not going to be the optimum setting. Likewise as the tracking error varies across the record, the bias will not be correct for most of it (unless the bias somehow matches the tracking error). So the bias will also depend on the geometry chosen.

I could argue that as the point of the optimum tracking geometry is to minimise the tracking error across the record, the average tracking error will be zero, therefore if there is only a fixed bias available, the correct setting is also zero.
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#53 Re: Classic Cartridges

Post by izzy wizzy »

If tracking error caused skating force, how come the arm skates inward on a flat record? Doesn't matter whether there is tracking error or what stylus shape, it still skates inwards for most pivoting arms. Sure these other factors will modify the absolute amount but it's there regardless of them.
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#54 Re: Classic Cartridges

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Depends on the weight distribution of the arm and wether its mounted level or not.
If the left hand bearing is a fraction of a degree lower than the right it will be trying to fall that way. The arm is almost never levelled by the user at the bearings because its pretty much impossible to do so. Unless you have a unipivot which must be levelled or it wont work properly. The wand is independent from the pillar in terms of the pivot angle where a gimbal arm is not. Most arms straight arms will be heavier to the left of the centreline at the cartridge end.
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#55 Re: Classic Cartridges

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If tracking error caused skating force, how come the arm skates inward on a flat record?
Because tracking error is a feature of geometry doesnt need need the groove. Again, back to my comments about the stylus angle against the line from the centre of the record and the stylus not being 90 deg.
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#56 Re: Classic Cartridges

Post by izzy wizzy »

I can't see how other than a unipivot, why an arms bearings would not be horizontal, well at least in the same plane as the platter. And if they are not, why not? The arm I have can be shown to be level by sticking a level on top. I acccept most arms can't. The stylus is in line with the arm. It skates.

I thought the linked videos earlier explained where skating force comes from. It comes from overhang. I'm going to leave this discussion as maybe my words aren't coming across right or my belief system is out of whack. 1000 words, pictures and all that.
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#57 Re: Classic Cartridges

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If by overhang you mean the distance the stylus is ahead or behind the zero tracking error point, then yes, I agree. But that does vary across the arc of the arm.
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#58 Re: Classic Cartridges

Post by izzy wizzy »

You trying to drag me back in to this Nick ;) A line 90 deg to the arm at the stylus is always ahead of the tangent that a linear tracking arm would be and so a pivot arm skates inwards. If it was behind, it would skate outwards. Put a square against the arm and it can be seen. The combo of overhang and offset allows the cartridge to be roughly accurate to tangent in the groove which is where the various alignments come in but overhang causes the arm to skate. Overhang being the distance it overhangs the spindle. The videos show this in action.
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#59 Re: Classic Cartridges

Post by vinylnvalves »

As this problem is related to angular velocity.. then it makes a mockery of 45rpm half speed masters... if skate forces are that significant. The Shure cartridge that started this debate was probably designed for 78’s so can cope with the side load. Obviously the 16 rpm records developed for car audio systems should be best..... for skating forces
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#60 Re: Classic Cartridges

Post by rowuk »

I do not know of anyone who really made an effort to quantify bias forces. It does seem to me however that generations of tonearms were developed WITH various bias schemes. Those were during the days when real engineers made decisions - not the marketing department. I therefore think that some is better than none.

I did test bias (or lack of it) once by accident in the early 1980s. On a modified to repeat automatic Dual turntable, I let a record run around the clock for a month and did not have the spring bias set. On that cartridge (a Shure something or other), I had a bent cantilever (skewed towards the middle of the record) at the end of the month. I did NOT accurately measure anything at the beginning and only noticed the problem due to very audible distortion. The experiment was actually music for a telephone system until a tape machine showed up.
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