not another 2nd pivot question

not another 2nd pivot question

Postby elader » Tue Oct 24, 2017 4:06 pm

OK, actually it is more of a comment.

Installation of the unit on the arm - pretty damn simple
Installation of the plate on the table - pretty damn simple


tell me if this seems reasonable - >
with the pivot on, the extra weight drags the azimuth to the inside. I adjusted the pivot screw until the azimuth was as good as my eye can get it.
I then unscrewed the other side counterweight until the pivot point floated off the plate
I then backed off the side weight until the point once again sat on the plate. Checked that it sat on the plate at the beginning and end of a disk
Adjusted tracking force

Seem right? How critical is the force on the pivot point? Should I add more for some reason?
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Re: not another 2nd pivot question

Postby Letsmakeadeal » Tue Oct 24, 2017 4:24 pm

elader wrote:OK, actually it is more of a comment.

Installation of the unit on the arm - pretty damn simple
Installation of the plate on the table - pretty damn simple


tell me if this seems reasonable - >
with the pivot on, the extra weight drags the azimuth to the inside. I adjusted the pivot screw until the azimuth was as good as my eye can get it.
I then unscrewed the other side counterweight until the pivot point floated off the plate
I then backed off the side weight until the point once again sat on the plate. Checked that it sat on the plate at the beginning and end of a disk
Adjusted tracking force

Seem right? How critical is the force on the pivot point? Should I add more for some reason?



Thumbs up... :lol: All in check...I use the lightest force possible that keeps the pivot on the plate during play....Less=more here in my opinion....if not already contemplated, you may want to put a couple turns of Teflon tape on the pivot set screw to keep it from moving. I used purple Loc-Tite but in retrospect I think the Teflon would have been a better choice now that I am fixing to use AdjustPlus to set azimuth...
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Re: not another 2nd pivot question

Postby Brf » Tue Oct 24, 2017 7:35 pm

Over the last couple of months I have been theorizing as to what would be the optimal force applied on the skate plate by the dual pivot. I then tested my theory with extensive listening test and my conclusions are listed below

1) The dual pivot point force should be 60-70% of the cartridge’s vertical tracking force.

2) A dual pivot force 1.0 grams less than the cartridge vtf may result in audible dual pivot bearing chatter in heavily modulated grooves

3) A dual pivot force 0.5g greater than the cartridge vtf will result in compressed micro dynamics and loss of high end extension.

The above results were based on a 12” arm
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Re: not another 2nd pivot question

Postby jonathanb » Tue Oct 24, 2017 7:40 pm

How does one measure the dual pivot's force?
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Re: not another 2nd pivot question

Postby thegage » Tue Oct 24, 2017 9:27 pm

jonathanb wrote:How does one measure the dual pivot's force?

My question too, as this is at least the 2nd time Brf has mentioned a specific loading force.

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Re: not another 2nd pivot question

Postby Brf » Wed Oct 25, 2017 7:45 am

jonathanb wrote:How does one measure the dual pivot's force?


It's very simple. I have a set of calibration weights that I place a bit of blu tack on the bottom and attached them on dual pivot's opposing azimuth weight.

As an example, assume that the dual pivot is loaded with an unknown force. If I place a known counteracting force (example 2g weight) on the opposite side of the dual pivot (opposing azimuth weight) and the dual pivot releases off the skate plate and the tonearm azimuth reaches equilibrium, I can conclude that the load on the pivot is equal to the known counter acting force (2 grams).

Simply put, it's a balance scale approach.

If one does not have a set of calibration weights, you can use a stylus pressure scale to find and measure a bolt nut (or something similar) that approximates the desired weight.
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Re: not another 2nd pivot question

Postby elader » Wed Oct 25, 2017 8:05 am

well I hope Matt will include calibrated blue tack to the kit at a later date.

Hmmnnn... I get this. So weigh two grams blu, stick it on the rightside weight and adjust it until it offsets the pivot point. I like it.
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Re: not another 2nd pivot question

Postby Johnny » Wed Oct 25, 2017 8:27 am

Brf wrote:
jonathanb wrote:How does one measure the dual pivot's force?


It's very simple. I have a set of calibration weights that I place a bit of blu tack on the bottom and attached them on dual pivot's opposing azimuth weight.

As an example, assume that the dual pivot is loaded with an unknown force. If I place a known counteracting force (example 2g weight) on the opposite side of the dual pivot (opposing azimuth weight) and the dual pivot releases off the skate plate and the tonearm azimuth reaches equilibrium, I can conclude that the load on the pivot is equal to the known counter acting force (2 grams).

Simply put, it's a balance scale approach.

If one does not have a set of calibration weights, you can use a stylus pressure scale to find and measure a bolt nut (or something similar) that approximates the desired weight.


You’re a smart cookie Brf. Very simple and effective, even an Accountant can understand your method ;)

I would imagine that a lot of users have no idea how much pressure they are putting on their dual pivot. Although there is a lot of good information provided on the VPI forum about proper set up etc. I’ll bet that most dual pivot owners don’t frequent the VPI forum.

Please explain what you mean by bearing chatter if one put too less pressure on the dual pivot? Also, why does high end extension become restricted with too much pressure?
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Re: not another 2nd pivot question

Postby thegage » Wed Oct 25, 2017 8:46 am

Johnny wrote:Very simple and effective, even an Accountant can understand your method ;)

Heck, even an English Major could understand the method. :lol:

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Re: not another 2nd pivot question

Postby JimTimP » Wed Oct 25, 2017 9:11 am

Johnny wrote:...
Please explain what you mean by bearing chatter if one put too less pressure on the dual pivot? Also, why does high end extension become restricted with too much pressure?


This would be the noise caused by the rocking action induced in the tonearm causing the pivot point to lift off the slide plate and then the thump generated when it rocks back and contacts the plate.

Too much pressure will cause additional drag and restrict the free movement of the arm. It would be like having a different mass (higher) tonearm.
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