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What angle should I set the VTA on my VPI turntable?

I can't believe after all these years, I am asking such a basic "analogue 101" question, but here it goes. I own a VPI turntable that has a "VTA on the fly" knob.  I thought the best VTA setting was for the arm to be 100% parallel to the record surface.  

However, based on some research, I am not so sure that is correct way to set the arm to achieve optimal VTA and correlatively, optimal SRA.  Not sure, ... but I think I have to raise the pivot side of the arm.

Any advice would be appreciated. 

Thanks.     
bifwynne
wlutke
744 posts
 
cleeds,
Wrong. On a unipivot the balance changes and I am correct.  You're comparing VTF and VTA.  Two different parameters.  
There is a typo though. There is no VTA/VTF block. It’s a VTA/Azimuth block. My bad.
lewm
13,732 posts
 
But if you replace VTA with VTF in cleeds post, the statement is correct, tail up, VTF up.
cleeds
6,252 posts
 
wlutke
cleeds,
Wrong. On a unipivot the balance changes and I am correct. You’re comparing VTF and VTA. Two different parameters.
You’re obviously confused.
VTA = Vertical Tracking Angle. Shown here.
VTF= Vertical Tracking Force. That’s the weight (force) on the stylus as it sits on the LP surface.

If you raise the "tail" (pivot) you can only increase VTA. It’s simple geometry - again, see diagram.

I’m not sure why you mentioned VTF but since you did: Increasing VTA by raising the "tail" (pivot) will also increase VTF. It will also decrease overhang. Again, this is all basic geometry and physics.
wlutke
744 posts
 
cleeds,
If you raise the "tail" (pivot) you can only increase VTA.
I know. Show me where I said differently.

Increasing VTA by raising the "tail" (pivot) will also increase VTF.
Wrong. Again, it changes the balance and the VTF lightens.
As an example, visualize the arm at level neutral balance above the platter. Raise the platter until it contacts the stylus. Still 0 grams pressure. Lower the tail. Now you have pressure. You’ve LOWERED the tail, INCREASING the pressure. There’s your physics.
lewm
13,732 posts
 
Dear lutke, I don’t know about your model, but throw it out. Now think that you and a friend are carrying a sofa. On level ground, the burden is equally shared. Now you have to carry the sofa up a staircase. Who is working harder? The guy at the top end or the guy at the bottom end? Raising the pivot point shifts the center of gravity toward the stylus. VTF goes up.
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