Upgrading from standard JMW 10" arm...3D or Fatboy

Re: Upgrading from standard JMW 10" arm...3D or Fatboy

Postby suntea » Wed Aug 08, 2018 11:27 am

[/quote]

Same for me - I have the smaller weights on the way.

New issue: while waiting for the smaller weights, I changed out the old Classic 3 pivot spike for the new one that will accept the 3D arm, and set the pivot spike at the same height level as the old spike. When I put my metal 10.5" JMW arm back on (to use while I wait for the smaller side weights for the 3D) I have the correct space of 1/8" to 1/4" between the azimuth ring and the dogleg platform.

However, now when I set the VTA, I have to turn it clockwise ALL the way until it stops to get the arm even close to parallel. I cannot lower it enough to get it parallel, which is always my starting point to set VTA by ear. The hex bolt in the bell housing has never been changed from the factory setting. I am at a loss, there must be something about the new 3D pivot spike that needs another adjustment. But it seems that changing it would compromise the distance between the azimuth ring and dogleg platform.[/quote]

You can raise your platter by putting a large washer(s) between the inverted bearing flange and the plinth. Alternatively, remove the armboard and have a local machinist remove 1/8" height. If you only need a bit of height, it won't hurt if you move the bearing pivot spike interface up a touch.[/quote]


Thanks for the ideas. Regarding your last comment on moving the bearing spike interface up a touch, are you referring to raising the spike level and increasing the space between the azimuth ring and the dogleg platform? Or something else? Thanks again.
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Re: Upgrading from standard JMW 10" arm...3D or Fatboy

Postby Brf » Wed Aug 08, 2018 11:32 am

suntea wrote:
Thanks for the ideas. Regarding your last comment on moving the bearing spike interface up a touch, are you referring to raising the spike level and increasing the space between the azimuth ring and the dogleg platform? Or something else? Thanks again.


Yes to raising the spike level and increasing the space between the azimuth ring and the dogleg platform
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Re: Upgrading from standard JMW 10" arm...3D or Fatboy

Postby suntea » Wed Aug 08, 2018 11:35 am

Brf wrote:
suntea wrote:
Thanks for the ideas. Regarding your last comment on moving the bearing spike interface up a touch, are you referring to raising the spike level and increasing the space between the azimuth ring and the dogleg platform? Or something else? Thanks again.


Yes to raising the spike level and increasing the space between the azimuth ring and the dogleg platform

Thank you Brf. I will try that first. I will go up another 1/16 of an inch and go from there. I realize the lower the better for weight distribution.

Do you think there is a maximum that should not be exceeded?
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Re: Upgrading from standard JMW 10" arm...3D or Fatboy

Postby suntea » Wed Aug 08, 2018 2:23 pm

Brf wrote:
suntea wrote:
Thanks for the ideas. Regarding your last comment on moving the bearing spike interface up a touch, are you referring to raising the spike level and increasing the space between the azimuth ring and the dogleg platform? Or something else? Thanks again.


Yes to raising the spike level and increasing the space between the azimuth ring and the dogleg platform


Just thinking this through a bit more. If I raise the spike level, I would need to lower the pivot point of the arm more to make the tonearm flat. Since the VTA tower is already all the way down, would raising the spike make the issue worse? Do I actually need to lower the spike as opposed to raising it? It does seem that the spike needs to be a certain height to engage the female end so it can only be lowered a certain amount.

I would appreciate thoughts - am I off base here? Thanks.
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Re: Upgrading from standard JMW 10" arm...3D or Fatboy

Postby suntea » Wed Aug 08, 2018 2:44 pm

Golear wrote:Re: New Issue

I ran into that, too! And I kept the original spike. You can see my post on this thread:
http://vpiforum.com/viewtopic.php?f=9&t=10726

I'd also see if there's any way to reduce the height of the spike assembly, by removing some metal, in a lathe.


Thank you - I have read the thread you mention. This makes me think using a platter mat would do the same thing as using an LP under the LP you are listening to? I have always gone "bareback" on my Classic 3as suggested by HW. Maybe its time to try a mat and see if it solves my problem at the same time?
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Re: Upgrading from standard JMW 10" arm...3D or Fatboy

Postby Brf » Wed Aug 08, 2018 2:46 pm

suntea wrote:
Brf wrote:
suntea wrote:
Thanks for the ideas. Regarding your last comment on moving the bearing spike interface up a touch, are you referring to raising the spike level and increasing the space between the azimuth ring and the dogleg platform? Or something else? Thanks again.


Yes to raising the spike level and increasing the space between the azimuth ring and the dogleg platform


Just thinking this through a bit more. If I raise the spike level, I would need to lower the pivot point of the arm more to make the tonearm flat. Since the VTA tower is already all the way down, would raising the spike make the issue worse? Do I actually need to lower the spike as opposed to raising it? It does seem that the spike needs to be a certain height to engage the female end so it can only be lowered a certain amount.

I would appreciate thoughts - am I off base here? Thanks.


Just to clarify. The VTA tower is at its lowest setting. You want to lower the back of the tonearm beyond parallel , then yes, you need to lower the pivot spike a touch. Sorry for the confusion, but you are on the right track
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Re: Upgrading from standard JMW 10" arm...3D or Fatboy

Postby suntea » Wed Aug 08, 2018 2:48 pm

[i]Thanks Brf. As subsequently stated, I was thinking a platter mat might also help. Any suggestions on a mat?[/i]
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Re: Upgrading from standard JMW 10" arm...3D or Fatboy

Postby Brf » Wed Aug 08, 2018 3:03 pm

suntea wrote:[i]Thanks Brf. As subsequently stated, I was thinking a platter mat might also help. Any suggestions on a mat?[/i]


I've used the Pro-Ject Leather-it mat with excellent results. I now use a custom CNC carbon fiber mat which is 3mm thick but unfortunately no longer made.
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Re: Upgrading from standard JMW 10" arm...3D or Fatboy

Postby Golear » Wed Aug 08, 2018 5:38 pm

Regarding an LP mat.... Yes, that's going in the right direction. But I found that a mat did not raise the height of the LP that's being played by a sufficient amount. And I did not like the sound of the soft mats. One 180 gram LP was not thick enough, either - hence my putting two LPs together.

I agree that there's a nice sound when playing LPs directly off the platter, and that's what I'd do too, if I could.

Come to think of it, if you put a something between the cartridge and the tonearm, then you would be able to play the LP directly off the platter, and be able to set the VTA. Many years ago, the great Enid Lumley suggested sandwiching a piece of relatively soft wood. Other options are hard metal (steel?), soft metal (copper? aluminium?), vinyl (from an old LP), or the same material as the 3D arm (if available from VPI). There's also delrin, and acrylic.

I didn't do this because I didn't want to re-align my cartridge. I might do this sometime in the future. I have a feeling (just a feeling) that vinyl from an old LP would sound good, so I should just have to drill two holes (can be outsize) and then cut a rectangle of material out and sand it down to size.

One would need slightly longer bolts. And given the use of two LPs as the "mat", the spacer would have to be at least as thick as the two LPs, too.

(I'd not consider using a stack of brass washers.... I think that would not sound good.)
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Re: Upgrading from standard JMW 10" arm...3D or Fatboy

Postby BillK » Wed Aug 08, 2018 9:33 pm

475211EB-B474-4583-B11C-C5FAE9433AF6.jpeg
475211EB-B474-4583-B11C-C5FAE9433AF6.jpeg (725.45 KiB) Viewed 309 times
That’s very interesting; I literally have the opposite problem: the VTA tower is at the top of its travel to get my stylus angle to 92° with the 10” 3D arm on my SSM.

The lock screw for the post behind the arm rest completely clears the top of the post.
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