The importance of measuring VTF at the right height when using the Kuzma 4-point etc

[Adagio]

At what height you measure VTF is very important, if you measure above the height of the record surface you will get the wrong VTF.
On some balanced tone arms this isn’t a problem but with the 4-point the most of the arms mass is so above the record surface, that it’s what they call a negatively balanced arm.
Anyway my gauge was way to high so I modified it slightly to get it to work properly with my 4-point.
I just cut a piece of thin aluminum and bent it in perfect angle, then glued it on the gauge. Since it automatically resets itself each time it’s turned of the extra weight doesn’t affect it.

 

[mtemur]

I bent original plate of the VTF gauge in order to lower measuring height to vinyl level. Works fine.

 

[Adagio]

I bent original plate of the VTF gauge in order to lower measuring height to vinyl level. Works fine.

I thought of that but it seemed a bit risky.

 

[J.R. Boisclair]

I suggest counterbalancing that scale surface. The strain gauge may throw off bad readings when it is subject to rotational torque force as your setup surely will do more than the original design. Other than that, you are perfectly right to want to improve what you have for a tonearm that has its center of gravity so much higher than the horizontal pivot axis!

 

[Adagio]

I suggest counterbalancing that scale surface. The strain gauge may throw off bad readings when it is subject to rotational torque force as your setup surely will do more than the original design. Other than that, you are perfectly right to want to improve what you have for a tonearm that has its center of gravity so much higher than the horizontal pivot axis!

Well 5g is the reference weight and is measures the Sam wherever I use it on the scale. 2.0 g is much less so I think is still accurate.

 

[sbo6]

Well 5g is the reference weight and is measures the Sam wherever I use it on the scale. 2.0 g is much less so I think is still accurate.

It's possible but the degree of accuracy (or inaccuracy) may not be linear up to 5g, the cart being at ~2 g.

 

[miniguy]

I have never played with a 4-Point tonearm so I can’t comment on what you’re trying to do, but you guys should be using correct terminology. See the second paragraph in my post #9 on this page: https://www.whatsbestforum.com/threads/my-thoughts-on-cartridge-arm-set-up.25143/

 

[rDin]

If you use a thick(ish) mat on your platter you can measure the height of the stylus on a record, including that mat, then remove the mat and use thinner ones/spare records to elevate the scale's platform to the exact same height as the stylus on the normal mat + record. My mat is 5mm height: by using a 3mm mat, my scale sits at exactly the same height as the stylus normally does.

 

[Don_Camillo]

Sorry, but VTF needs to be measured at right height (LP surface level) with any tonearm.

 

[Balle Clorin]

That would be correct for a static balanced tonearm, but a dynamically balanced would probably not care.. I can check VTF on my SME V with different mat thickness and see..V sets VTF be a spring so it is not statically balanced.

The effect on angle on a static arm is estimated by simplified trigonometry.. 1mm thicker mat affects the VTF by a factor of 0.9999906 , so no scale would notice it…

 

[miniguy]

That would be correct for a static balanced tonearm, but a dynamically balanced would probably not care

Incorrect. How VTF is applied, whether by spring or counterweight, does not matter. It only depends on the location of the arm’s CG in relation to the vertical pivot. If the CG lies below the pivot, the arm is said to be in stable balance so that upward displacement of the arm causes an increase in VTF. If the arm CG lies above the pivot, it is in unstable balance so that upward displacement of the arm causes a decrease in VTF. If the arm CG is coincident with the pivot the arm is in neutral balance so that no change occurs in VTF for any vertical position of the stylus.

 

[Balle Clorin]

The question I answered was not during dynamic behavior,but static position when setting the VTF, I think that will be different.
Considering that an arm is balanced to a given VTF with a slope and stylus below playing surface, bringing the arm horizontal at level with the playing surface will give a higher VTF . So correct VTF is set on a static arm with the stylus at the correct playing level.

 

[miniguy]

So correct VTF is set on a static arm with the stylus at the correct playing level.

Static or dynamic, makes no difference.

 

[Balle Clorin]

You are missing the point , VTF and leveling when setting it. Post 9

 

[PeterA]

I think we can all agree that changes in vertical tracking force are audible. I am curious that there is there so much focus on an actual number and how accurate it is. Once you’re close to the middle of the range of the manufacturer’s recommended tracking force, why not just make very small adjustments until it sounds right? Why not judge by listening as the record is playing rather than try to reach some target value? And then just leave it at that. If you want to record it for later reference, just use the same scale for repeatability. Accuracy is less vital than consistency.

Whenever I am setting up a cartridge, I do everything by listening, except for alignment. For me, the target is what sounds right not adjusting to some specific number.

There seems to be enough variance from sample to sample to simple repeat settings. I find I want to adjust each individual cartridge by ear for best performance.

 

[Balle Clorin]

VTF and crosstalk AT33PTGii

 

[PeterA]

I usually play within a range of half a gram or less when I am adjusting VTF on my cartridges. I just in roughly .05 or .1 g increments.