Rule of thumb for VTA height

Re: Rule of thumb for VTA height

Postby EdAInWestOC » Tue May 30, 2017 10:55 am

Pevo wrote:EdAinWestOC, interesting observations, but something doesn't seem right. In the past Brf has said that one turn of the VTA tower raises/lowers the arm 1/32" (0.03125") and he states it is 1.4 turns of the tower (0.04375") to go from 120g to 180g vinyl. In your evaluation you found the difference between thinnest and thickest discs to be 1.25 mm or 0.0492126". The strange part is the difference you stated is greater than what Brf said yet you are turning the tower less than one full turn. This indicates to me one of three things; 1) Your tower raises/lowers more than 1/32" per turn, or 2) you are turning more than one turn and didn't realize it, or 3) your measurement of the record thicknesses is off. I say this since you state you measured with a calipers. When measuring make sure you are not measuring the thickness of the edge of the record, rather, measure the groove area. Depending on your caliper design this may not be possible. I would suggest using a micrometer to make sure you are clear of the edge of the record. Perhaps someone else will see another possibility here, but that's my thought for now.

The calipers that I am using has a gap at the inner portion of the jaws that clears the outer bead. At any rate that would not effect either the UHQR or the Classic Records 200gm heavy weight pressings both of which have no outer bead.

I am not new to setting VTA, nor am I missing the fact that I am turning more than one turn. I am an educated man that has experience with what I am dealing with. I am sure what I listed is the thickness of the LPs and it seems to be verified by the fact that the optimum VTA setting is between 45 and 75. Otherwise it would require more than one full turn and the measurement of the arm height would not agree with the LP thicknesses.

That is why I was confused by Brf's post of the 1.4 turns for standard to heavy weight pressing. If I turn past 75 on any of my heavy weight LPs I can guarantee the LP will sound strident indicating that I have past the upper point of SRA. Anyone with a way to measure their LPs can verify my LP thickness numbers. And if they care to measure the amount that the arm actually moves for the range that I have indicated, they can verify those numbers as well.

Another problem is that everything I have measured is reinforced by my listening. If I attempt to turn the VTA tower 1.4 turns, a heavy weight pressing would be un-listenable. The right place for VTA is within the range I indicated.

Maybe I should also include the cartridge I am using, which is an Ortofon Quintet Black S.

Is there anyone here that uses the 3D arm with VTA on the fly AND turns it 1.4 turns for heavyweight pressings? Unless the arm mechanism has changed I would doubt that.

Ed
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Re: Rule of thumb for VTA height

Postby Pevo » Tue May 30, 2017 2:59 pm

Ed, not trying to lay blame on you, just raising some possibilities. Always best to not make too many assumptions under these circumstances. The important point to me, unless I'm screwing something up here, is you are getting more raising/lowering in less than one turn than what Brf stated. Something doesn't add up and maybe someone else has figure it out. I'm not at home right now and cannot confirm any of the measurements, plus my arm is older and should conform to what Brf stated. Perhaps new arms have a coarser pitched thread?
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Re: Rule of thumb for VTA height

Postby EdAInWestOC » Wed May 31, 2017 7:54 am

Pevo wrote:Ed, not trying to lay blame on you, just raising some possibilities. Always best to not make too many assumptions under these circumstances. The important point to me, unless I'm screwing something up here, is you are getting more raising/lowering in less than one turn than what Brf stated. Something doesn't add up and maybe someone else has figure it out. I'm not at home right now and cannot confirm any of the measurements, plus my arm is older and should conform to what Brf stated. Perhaps new arms have a coarser pitched thread?

Pevo,
I apologize if I sounded somewhat course. I appreciate your feedback and I wondered about the thread change too.

My post my not be totally clear on this but I was surprised by the results of my measurements. I expected to see some discrepancy but an exact measurement between the arm movement and the LP thicknesses has to be coincidental. Nonetheless, it did reinforce my experience with the 3D tonearm.

If the 3D arm's VTA tower adjustment functioned the way it was described by Brf, I would have discovered this via usage of the VTA on the fly. I read Brf's post sometime ago and I knew it did not agree with the way I was using my tonearm. I intended to measure the LP thicknesses and the tonearm vertical movement but it wasn't a critical item since everything was functioning properly according to my ears.

I started a thread on another forum and it appears that the number of people who adjust the VTA/SRA for each LP is not a very large group. If people are not using the 3D arm with "VTA on the fly" the rule of thumb that is the topic of this thread could be incorrect. That or I am completely wrong.

That last point would not be hard to accept except that the measurements of the LP thicknesses and the measurements of the vertical movement of the tonearm platform reinforce each other, exactly.

That places me in the odd position of maybe being correct, just maybe (something that my ex-wife would never agree with). :lol:

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Re: Rule of thumb for VTA height

Postby Brf » Wed May 31, 2017 8:53 am

EdAInWestOC wrote:
Brf wrote:For every 1 degree change in sra, it takes approximately 5 1/2 turns of the vta tower. The change in sra between standard vinyl and heavy weight vinyl is approximately 0.25 degrees, which equates to 1.4 turns of the vta tower. Of course, these rough calculation change as the effective length of the arm changes. Personally, I don't change sra for different vinyl thickness.

The information above bothered me. It does not correspond with my experience with the VTA settings for the 3D arm and its use with my LP library. Either I am using the VTA adjustment wrong and/or I have gone deaf.



There are only three factors at play, 1) trigonometry, 2) the delta in thickness between standard and heavyweight vinyl, 3) and the height indexing of the VTA tower.

1) The trigonometry of an acute angle is not in dispute (see diagram below)
2) I agree that the delta between album thickness is approx. 1.25mm
3) The VPI VTA tower has a thread pitch of either 1-28, or 1-32 (sorry can’t recall exactly which one, but using a micrometer on my vta tower confirmed that it is either one of the two). The VTA tower has 100 indexes per rotation. Using a pitch of 1-28, that translates into 0.00035 of an inch (0.0091 of a mm) for each index on the VTA tower.

If I want to maintain the same stylus angle between standard and heavyweight vinyl (Δ1.25mm) one needs to adjust the vta tower by 1.25/0.0091 = 137 indexes or 1.37 turns of the vta tower. That’s the math based on known values.

If one decides not to change the vta tower height between standard and heavyweight vinyl (Δ1.25mm) that would result in a change in stylus angle of approx. 0.26 of a degree.

When I set up my VTA/SRA, I use an album thickness that represents the average thickness of my collection, therefore, reducing the possibility of a delta between album thicknesses.

As previously mentioned, I do not change vta based on album thickness because I cannot hear a difference between a sra 92° and 92.26°, however, I do respect those who do claim to hear a difference, therefore, adjust away.
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Re: Rule of thumb for VTA height

Postby EdAInWestOC » Wed May 31, 2017 2:46 pm

Brf wrote:
EdAInWestOC wrote:
Brf wrote:For every 1 degree change in sra, it takes approximately 5 1/2 turns of the vta tower. The change in sra between standard vinyl and heavy weight vinyl is approximately 0.25 degrees, which equates to 1.4 turns of the vta tower. Of course, these rough calculation change as the effective length of the arm changes. Personally, I don't change sra for different vinyl thickness.

The information above bothered me. It does not correspond with my experience with the VTA settings for the 3D arm and its use with my LP library. Either I am using the VTA adjustment wrong and/or I have gone deaf.



There are only three factors at play, 1) trigonometry, 2) the delta in thickness between standard and heavyweight vinyl, 3) and the height indexing of the VTA tower.

1) The trigonometry of an acute angle is not in dispute (see diagram below)
2) I agree that the delta between album thickness is approx. 1.25mm
3) The VPI VTA tower has a thread pitch of either 1-28, or 1-32 (sorry can’t recall exactly which one, but using a micrometer on my vta tower confirmed that it is either one of the two). The VTA tower has 100 indexes per rotation. Using a pitch of 1-28, that translates into 0.00035 of an inch (0.0091 of a mm) for each index on the VTA tower.

If I want to maintain the same stylus angle between standard and heavyweight vinyl (Δ1.25mm) one needs to adjust the vta tower by 1.25/0.0091 = 137 indexes or 1.37 turns of the vta tower. That’s the math based on known values.

If one decides not to change the vta tower height between standard and heavyweight vinyl (Δ1.25mm) that would result in a change in stylus angle of approx. 0.26 of a degree.

When I set up my VTA/SRA, I use an album thickness that represents the average thickness of my collection, therefore, reducing the possibility of a delta between album thicknesses.

As previously mentioned, I do not change vta based on album thickness because I cannot hear a difference between a sra 92° and 92.26°, however, I do respect those who do claim to hear a difference, therefore, adjust away.

OK...thats all accepted...but what I may have missed is why is my 3D tonearm moving up/down 1.25mm when changing the VTA tower setting from 45-75 (within a single rotation, not over one)? I repeated the measurement and if I rotate my VTA tower by 30 markings the arm platform moves up/down by 1.25mm.

It does not correspond to the trig. To tell the truth I prefer it the way it is and would not like to have to rotate it over one turn to make the adjustment. It is more convenient the way that it is.

All of that said, since the title of the thread is "Rule of thumb for VTA height" the amount that the tonearm is moving up/down is relevant and maybe we should have other people actually measure their tonearm vertical motion to verify what is going on.

Ed
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Re: Rule of thumb for VTA height

Postby weust » Wed May 31, 2017 3:40 pm

And all I asked was a rule of thumb :-)
But nice to see the discussion. The reason I asked in the first place, was because I learned with my Technics 1210 MK2 you're supposed to level the arm, and then use the height adjuster to vertically adjust the arm assembly relative to the record.

Plus, I thought the VTA had the numbers in millimeters. Which I am wrong about too.
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Re: Rule of thumb for VTA height

Postby Brf » Wed May 31, 2017 4:09 pm

EdAInWestOC wrote:OK...thats all accepted...but what I may have missed is why is my 3D tonearm moving up/down 1.25mm when changing the VTA tower setting from 45-75 (within a single rotation, not over one)? I repeated the measurement and if I rotate my VTA tower by 30 markings the arm platform moves up/down by 1.25mm.


I cannot answer that question. All of VPI arms that I own have an index of 0.0091 of a mm, or 0.91mm per turn.

EdAInWestOC wrote:
It does not correspond to the trig. To tell the truth I prefer it the way it is and would not like to have to rotate it over one turn to make the adjustment. It is more convenient the way that it is.


Trust me, the trigonometry is correct. If rotating 30 indexes of the VPI tower (45 to 75) moves your arm up 1.25mm, then we are on the same page.

The issue that I have with your response is that I have never seen, measured, or read a VPI vta tower with that course of an adjustment. It would take less than 7 turns of the VTA knob to remove the entire tower assembly.

To other posters, if you turn your vta knob 1 full turn, does the height change by 0.91mm or 4.16mm??
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Re: Rule of thumb for VTA height

Postby Johnny » Wed May 31, 2017 5:07 pm

Brf wrote:
EdAInWestOC wrote:OK...thats all accepted...but what I may have missed is why is my 3D tonearm moving up/down 1.25mm when changing the VTA tower setting from 45-75 (within a single rotation, not over one)? I repeated the measurement and if I rotate my VTA tower by 30 markings the arm platform moves up/down by 1.25mm.


I cannot answer that question. All of VPI arms that I own have an index of 0.0091 of a mm, or 0.91mm per turn.

EdAInWestOC wrote:
It does not correspond to the trig. To tell the truth I prefer it the way it is and would not like to have to rotate it over one turn to make the adjustment. It is more convenient the way that it is.


Trust me, the trigonometry is correct. If rotating 30 indexes of the VPI tower (45 to 75) moves your arm up 1.25mm, then we are on the same page.

The issue that I have with your resdponse is that I have never seen, measured, or read a VPI vta tower with that course of an adjustment. It would take less than 7 turns of the VTA knob to remove the entire tower assembly.

To other posters, if you turn your vta knob 1 full turn, does the height change by 0.91mm or 4.16mm??


I just measured both of mine and they are No Way close to 4.16mm. I don't own a precision measuring device that can measures a gap of less than 1mm, but I would hazard a guess that is is very close to Brf's measurement of 0.91mm.
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Re: Rule of thumb for VTA height

Postby EdAInWestOC » Thu Jun 01, 2017 6:54 am

Brf wrote:
EdAInWestOC wrote:OK...thats all accepted...but what I may have missed is why is my 3D tonearm moving up/down 1.25mm when changing the VTA tower setting from 45-75 (within a single rotation, not over one)? I repeated the measurement and if I rotate my VTA tower by 30 markings the arm platform moves up/down by 1.25mm.


I cannot answer that question. All of VPI arms that I own have an index of 0.0091 of a mm, or 0.91mm per turn.

EdAInWestOC wrote:
It does not correspond to the trig. To tell the truth I prefer it the way it is and would not like to have to rotate it over one turn to make the adjustment. It is more convenient the way that it is.


Trust me, the trigonometry is correct. If rotating 30 indexes of the VPI tower (45 to 75) moves your arm up 1.25mm, then we are on the same page.

The issue that I have with your response is that I have never seen, measured, or read a VPI vta tower with that course of an adjustment. It would take less than 7 turns of the VTA knob to remove the entire tower assembly.

To other posters, if you turn your vta knob 1 full turn, does the height change by 0.91mm or 4.16mm??

Ok, then that was the point of my posting this discrepancy. I do not disagree with anything you wrote other than the fact that my VTA tower does not move the tonearm platform the amount that you say it should. That's all. I do not dislike the fact that it moves the way that it does. In fact, it is perfect the way that it is. I only posted what I did to bring up the fact that my 3D tonearm does not behave as you originally described.

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Re: Rule of thumb for VTA height

Postby Johnny » Thu Jun 01, 2017 8:18 am

EdAInWestOC wrote:Ok, then that was the point of my posting this discrepancy. I do not disagree with anything you wrote other than the fact that my VTA tower does not move the tonearm platform the amount that you say it should. That's all. I do not dislike the fact that it moves the way that it does. In fact, it is perfect the way that it is. I only posted what I did to bring up the fact that my 3D tonearm does not behave as you originally described.

Ed


Ed, something is wrong and does not make sense. I just pulled out an old issue of HiFi+ in which reviewer Roy Gregory confirms that the vta height adjustment is in fact indexed at 1/35000 of an inch.

Why would your VTA have it's thread's cut 4.5 times larger than standard? A Machinist would never cut a 1/4" shaft with a 7 inch thread count as there would be very little metal left. The lowest thread count 1/4" bolt made has a thread count of 20.

A don't want to be argumentative, but I believe that you may have measured wrong. If you are really curious as to the exact height adjustment of your vta tower, unscrew it and count the threads per inch, that will give you a definitive answer.
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