14 INCH FATBOY-

Re: 14 INCH FATBOY-

Postby Orchids1 » Sun Sep 01, 2019 5:20 pm

Golear et al, I’m not implying that there is anything dishonest about promoting the 14” Fatboy. What I’m trying to say is that, after all the highly technical linear offset/tangential cantilever analytics are said and done, the conclusion appears to be that there is tradeoff of very slight skate distortion for very slight tracking distortion. I don’t even know whether either type of distortion is audible. I can’t recall anyone complaining about skate distortion on a properly set up VPI tangential cantilever, although there has been plenty of discussion about the physics of the skate force. So I don’t see the advantage to the Fatboy relative to the other the VPI arms, unless it’s to give us a choice between different sorts of very slight, and perhaps undetectable, distortions. Rich
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Re: 14 INCH FATBOY-

Postby jonathanb » Sun Sep 01, 2019 5:58 pm

Are you talking about all Fatboys or just the 14" one? Your posts read as if you mean all of them.
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Re: 14 INCH FATBOY-

Postby Harry » Mon Sep 02, 2019 1:04 pm

Sorry I walked away for so long, we have been working on multiple items and have been a bit tied up plus I had no idea my response would generate this much interest!!

First, the use of a non offset headshell does not preclude to null points, think about it. We have two null points, tracking error is rather low, and the sound of no skating force
constantly pulling the coil out of the focus of the magnetic field is very smooth, very low distortion.

Try to forget all the old theories and start at the beginning, why have skating force if we don't have to. Why have short arms if we can now produce long ones that are very rigid and light, why use anti-skate that simply pulls the arm in different directions to ever changing force?

Most important a 14" arm with two null points sounds really, really good!!

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Re: 14 INCH FATBOY-

Postby Ducky » Thu Sep 05, 2019 2:20 pm

Harry-

I'm having trouble understanding your statement: "We have two null points, tracking error is rather low...". It's difficult to see how a tonearm with zero offset can have more than one null point. I plugged the numbers into an on-line calculator and came up with the following:

14in No Offset.jpg
14in No Offset.jpg (341.2 KiB) Viewed 603 times


It shows only one null point at 95.498mm, tracking angle error of 7.5° at 60mm from the spindle (blue trace) and distortion of >6% (Red trace). Can you tell us how you are coming up with your measurements?
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Re: 14 INCH FATBOY-

Postby Brf » Thu Sep 05, 2019 2:41 pm

Ducky wrote:Harry-

I'm having trouble understanding your statement: "We have two null points, tracking error is rather low...". It's difficult to see how a tonearm with zero offset can have more than one null point.


I can't figure out that one either.....
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Re: 14 INCH FATBOY-

Postby Harry » Fri Sep 06, 2019 10:48 am

I've never plugged it into the various programs to calculate these things I do it from the CAD drawings that I would love to share but can't yet. Picture an arm positioned so at the middle of its travel it is ## mm in front of the tangent line in the center of the groove area and then as it tracks its arm it creates two null points as it crosses the tangent line. Sorry for being obtuse about this but the CAD drawing doesn't lie and the math is really, really good and groundbreaking.

When mat showed the 14" no offset arm on Facebook a mathematician from Italy sent me a three page treatise on why this is so perfect for tracking a vinyl groove. As we explored his math and zeroed in on what was actually needed in overhang and location it all came together. This will be a game changer!!

Will show all the details after Capitol Audio Show and we will discuss it there at the usual forum we attend.

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Re: 14 INCH FATBOY-

Postby Ducky » Fri Sep 06, 2019 2:21 pm

We might have a confusion of definitions?

Moving the stylus forward from the normal tangent line (to the left) will create 2 points where the stylus will intersect the original line, but neither point will be a 'null' in the sense that the tracking error is zero. If both the S2P distance and length of arm are fixed during playback, there is only one solution to Pythagoras' theorem, therefore only a single null point.

From my example above, shortening the S2P distance by 10mm (moving the stylus to the left of the normal tangent point), will move the single null to 43.08mm from the spindle (probably the dead wax area) and rotate the normal tangent line 6.9° CW; the inner groove tracking error drops to 2.7°, but the outer groove error increases to 10.8°.

Lengthening the S2P distance by 10mm (moving the stylus to the right of the normal tangent point), will cause a single null at 128.78mm from the spindle and rotate the normal tangent line 5° CCW; the inner groove tracking error jumps to 16.35° and the outer groove error drops to 2.47°.

Unless I'm missing something; maybe you could provide some numbers for the S2P you are using?
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Re: 14 INCH FATBOY-

Postby Harry » Fri Sep 06, 2019 6:27 pm

Your math is impeccable and as you said we are talking about different things and by accident these things happen when I am trying not to spill the beans on the math used. Let's just put it this way, the second half of the record where the distortion and tracking error actually matter (this is a weighted issue, not linear) the new design will lower tracking error where it really matters and remove that pesky skating force that is really bad when a hole is not in the center and the forces on the arm are greatest. Sorry, best I can do till November but really nice work Ducky, you would love the math on this new design!!

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Re: 14 INCH FATBOY-

Postby Ducky » Fri Sep 06, 2019 6:43 pm

Thanks Harry. I'll look forward to your further explanation.
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Re: 14 INCH FATBOY-

Postby Mat » Mon Sep 09, 2019 11:04 pm

Well I guess this one is out of the bag too 8-)

Than again we did throw the design on the screen at a turntable seminar :P

Looking forward to Capital!
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