Question regarding dual pivot kit

Re: Question regarding dual pivot kit

Postby leftside » Fri Oct 18, 2019 1:09 pm

Mr_Putty wrote:
leftside wrote:Would slightly unscrewing the outer weight (on the right of the tonearm) also decrease the force on the pivot? Then I wouldn't have to mess with the counterweight and the VTF?
Yes.

Alright I'll pull out the high-powered reading glasses at the weekend and give it a go. Thanks.
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Re: Question regarding dual pivot kit

Postby leftside » Fri Oct 18, 2019 5:23 pm

Think I found the thread you guys are talking about:
viewtopic.php?f=12&t=9534&hilit=dual+pivot

Ordered :)
https://www.amazon.ca/gp/product/B003STEJAC/1

So, if my VTF is 2g, I'm going to want the opposing force of the pivot to be around 1.2g to 1.4g (measured using the above counter weights and blutac)? And this opposing force will cause the pivot to raise very slightly off the plate - and I'll assume the pivot is then applying the correct pressure on the plate?
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Re: Question regarding dual pivot kit

Postby Mr_Putty » Fri Oct 18, 2019 10:09 pm

I think you have the plan. Please post your result with any issues.
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Re: Question regarding dual pivot kit

Postby leftside » Sun Oct 20, 2019 8:36 pm

All good. I just had to slightly unscrew the weight on the right.

Straight away, I noticed when returning the cart to the arm holder (after a record had finished playing), I no longer heard the very faint scraping noise I could hear before of the pivot screw on the metal plate.

I'll weigh/adjust the pivot point later in the week when I get some blu tack.
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Re: Question regarding dual pivot kit

Postby Waxxy » Fri Nov 08, 2019 12:17 pm

Golear wrote:Does the second pivot have to be a sharp point? Will it work just as well if the tip is rounded?


A perfectly round tip...such as the ruby ball pictured below, will have less of a contact point than almost any sharpened point. Without material deflection, a ball has an almost infinitely small contact point. The smaller contact point would focus the weight applied to the dual-pivot to a smaller area, effectively increasing the mass and causing more friction / stiction. At least that's how it works in my head!

I would think that a small tip made from a material like teflon (or any other slippery plastic) mated to a teflon skid plate, would allow the dual pivot to perform more optimally. It's obvious that the current design has friction issues or it wouldn't be carving a groove in the stainless steel plate.

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Re: Question regarding dual pivot kit

Postby Mr_Putty » Sat Nov 09, 2019 3:23 am

Waxxy,
If you have not done so, I think you would enjoy a similar thread in the Support forum by Votan. Titled, The best tweak for all VPI turntables. Not specifically stated in the other thread, I think there are two concerns being addressed. One is the absolute rigidity of the VTA adjustment tower mechanism, and the other is how micro vibrations of various sources are affecting the final system sound. Those trying various tweaks seem to agree (IMHO) that removing the vibrations from the dogleg results in improved sound. My observation is that wear on the second pivot plate appears to be caused by micro vibrations more than just by sliding friction between the plate and the post contact area. Also, the contact of the post appears to be acting as a ground-plane-relief of micro vibrations in addition to its main purpose of stabilizing the tone arm in the horizontal plane. My thought is that a soft surface for a plate would not allow micro vibrations to exit the dogleg efficiently. Your ball idea looks interesting. What is the material you used?
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Re: Question regarding dual pivot kit

Postby tom collins » Sat Nov 09, 2019 8:44 am

I recently had an in-depth discussion with a person whom I won't name, but is quite involved in the VPI world. I trust his insight. His suggestion was to not purchase the 2nd pivot. As you can see in my system description, I use the 12.7 arm. I told this person that what I hoped to get from the 2nd pivot was tighter bass. He said you might get that at the expense of treble clarity and that the drag of the pivot would damage the faceplate. His recommendation was for a pivoted arm to accomplish what I wanted without the sacrifice to the treble. Interestingly, the table had an SME Model 4 when I bought it because the original owner felt that the original JMW-10 metal arm sounded too unfocused. With the exception of the bass I wanted to tighten up, I have never felt the 12.7 was unfocused in any way, in fact, it seems to be a micro-dynamic vacuum cleaner. I can't afford the VPI pivoted arms, but there are other pivoted options out there that I may try possibly as a winter project. I just wanted to throw this out there for everyone to chew on. Bon apetit
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Re: Question regarding dual pivot kit

Postby Waxxy » Sat Nov 09, 2019 9:41 am

Mr_Putty wrote:Waxxy,
If you have not done so, I think you would enjoy a similar thread in the Support forum by Votan. Titled, The best tweak for all VPI turntables. Not specifically stated in the other thread, I think there are two concerns being addressed. One is the absolute rigidity of the VTA adjustment tower mechanism, and the other is how micro vibrations of various sources are affecting the final system sound. Those trying various tweaks seem to agree (IMHO) that removing the vibrations from the dogleg results in improved sound. My observation is that wear on the second pivot plate appears to be caused by micro vibrations more than just by sliding friction between the plate and the post contact area. Also, the contact of the post appears to be acting as a ground-plane-relief of micro vibrations in addition to its main purpose of stabilizing the tone arm in the horizontal plane. My thought is that a soft surface for a plate would not allow micro vibrations to exit the dogleg efficiently. Your ball idea looks interesting. What is the material you used?


The (ruby) ball pictured in my post above is not mine, and not my idea...it's an image I've borrowed from a similar discussion on another forum.

I don't use the second pivot, and in my opinion it's a flawed design. The concept has some validity, but the execution needs a bit of rethinking.

You mention..."Also, the contact of the post appears to be acting as a ground-plane-relief of micro vibrations in addition to its main purpose of stabilizing the tone arm in the horizontal plane. My thought is that a soft surface for a plate would not allow micro vibrations to exit the dogleg efficiently."
I would imagine the main tonearm pivot itself would act as a ground-plane-relief in the absence of the secondary path provided by the dual pivot. And in my mind, if as you say, the arc carved into the skid plate is caused my micro vibrations - literally hammering the second pivot into the plate! - then it certainly would be causing more harm than good. But second pivot users all report much increased performance, and they can't all be imagining things, so there is something to it and maybe I'm out to lunch! :lol:

I have old-school JMW-10 and 10.5 armwands that allow the use of fluid damping at the pivot. I like that concept better than the existing execution of the second pivot.

As for the 'best tweak' thread, I've been using a cone / spike directly underneath the tonearm pivot for some years now, trying to approximate the simpler VPI tonearm mount supplied with the JMW-9 tonearm, which eschews the VTA-on-the-fly mechanism. At one point, I considered replacing my VTA tower with the simpler JMW-9 style mount, but I'm happy with the "cone solution".

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