The VPI Turntable Thread

OMC said:
Not an actual issue but needing the counterweight that far from the pivot point does create more inertia which does affect cartridge tracing.
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Yeah this is kinda what I was concerned with. Wonder if it makes sense just to go with the lighter screws. Even though the compliance calculator seems to indicate the heavier ones are better
 
OMC said:
Not an actual issue but needing the counterweight that far from the pivot point does create more inertia which does affect cartridge tracing.
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Decided to split the difference. Went with the lighter screws because I realized that I have no idea what the finger lift weighs but it will almost certainly put the arm into ideal compliance because I'm assuming it's at least a couple of grams.

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Mather said:
Decided to split the difference. Went with the lighter screws because I realized that I have no idea what the finger lift weighs but it will almost certainly put the arm into ideal compliance because I'm assuming it's at least a couple of grams.

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Do the newer VPI arms have an optional secondary weight built into the back of them? It screwed right in the threaded arm. My older 10.6 did and I used it with my heavy (16.4 gm) Benz LPS.
 
OMC said:
Do the newer VPI arms have an optional secondary weight built into the back of them? It screwed right in the threaded arm. My older 10.6 did and I used it with my heavy (16.4 gm) Benz LPS.
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They do, but they're an additional purchase. I just upgraded from the 160 and bought this 180 weight specifically for this cart but seems that maybe I should have gone the 200 gm. But this works.
 
Lee Newman said:
Wouldn’t the heavy screws offset that a bit.
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If the world was a perfect place and all record spindle holes were perfectly centered mass would be less of a concern. As we know, a perfectly centered record is seldom achieved and that’s where the problems arise with heavier counterweights and heavier screws and inertia can be a problem. The less concentric the record the more side to side wiggles have to be dealt with by the cartridge assembly, as well as the groove walls of the record dealing with higher pressures as the stylus has to change direction with each non-concentric revolution.
 
OMC said:
If the world was a perfect place and all record spindle holes were perfectly centered mass would be less of a concern. As we know, a perfectly centered record is seldom achieved and that’s where the problems arise with heavier counterweights and heavier screws and inertia can be a problem. The less concentric the record the more side to side wiggles have to be dealt with by the cartridge assembly, as well as the groove walls of the record dealing with higher pressures as the stylus has to change direction with each non-concentric revolution.
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I get that, but would not the screws and the weight be providing opposite directions of inertia?
 
Lee Newman said:
I get that, but would not the screws and the weight be providing opposite directions of inertia?
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Think of the tonearm as a lever. The farther out and the heavier each end of the lever is the more mass that has to be dealt with, mostly by the cantilever system with the vinyl of the groove coming in second as far as elasticity goes. Overcoming the inertia of the increased leverage created by the heavier weights and farther distance from the pivot point of the arm makes it more difficult for the whole shebang to overcome the changes in direction.
 
You have a 300 Shaq and and a 175 pound Steph. Who can change directions more quickly and easily? I'll bet on Steph every time. ;)
 
OMC said:
Think of the tonearm as a lever. The farther out and the heavier each end of the lever is the more mass that has to be dealt with, mostly by the cantilever system with the vinyl of the groove coming in second as far as elasticity goes. Overcoming the inertia of the increased leverage created by the heavier weights and farther distance from the pivot point of the arm makes it more difficult for the whole shebang to overcome the changes in direction.
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I get this, but the weight is on one end and the cartridge and the screws are on the other.
The pivot point is in between those two spots.

So the weight is causing inertia to happen in one direction - let's say the outside groove. The weighted screws are somewhat offsetting that by causing inertia in the other direction - let's say the inside groove. The fulcrum of the pivot point would of course make one inertia greater than the other. Which is probably why the weights are close to the pivot point in general.
 
Or course the extra funny thing about all this is I'm stressing over decimal points and excursion graphs with the Paua and meanwhile my 2M Black was SO far out of compliance it wasn't even funny. Like not even close. And it sounded great so....
 
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