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Dumb VTA Question

Sorry ... I have a dumb question about setting VTA. I own a VPI Classic TT which has "VTA on-the-fly" capability. My cartridge is the Lyra Kleos. When I mount the Kleos, the last adjustment is VTA. I start by setting VTA so that the tonearm appears horizontal. Then while I'm playing a record, I raise the tonearm and then lower it until I like what I hear.

Ok ... that's what I do. But here's the dumb question. Some vinyl buffs talk about setting VTA at 91.5 degrees, or 92.5 degrees, and the like. How the heck can someone know the degree of VTA adjustment with such precision?? Is there a tool or special protractor that permits such close adjustments?

Thanks for the education.

BIF
bifwynne
peterayer
1,382 posts
 
I thought I read that M. Fremer wrote that with a 9" arm, a 4mm change in height amounts to a 1 degree SRA change. I have a 12" arm and adjust my SRA for different LPs. I move my arm up and down in a 3mm range which amounts to about a 1/2 degree SRA difference. That sounds tiny, but it is audible and worth the effort to me. I don't then also adjust VTF and overhang, though I know they are effected.

I mark my LPs with the best setting height for reference and this does not correspond to the varying record thicknesses. For example, I have lots of LPs that are say 160g and they cover the full 3mm range of best VTA. Same for my 180g LPs.
sarcher30
596 posts
 
Dinster, Baerwald is the best compromise for the records I play. I like to stay as close to that as possible. YMMV.

It is not an issue on my Schroder LT. With this linear tracker I can easily dial alignment in by ear.
dinster
76 posts
 
Apologies Peterayer, you are correct. I redid the calculations and 5.3mm change in base height on a 12 inch arm (304mm), changes the SRA by 1 degree. Sine theta = vertical change in height (opposite)/length of tone arm (hypotenuse). This adjustment will decrease the overhang by 0.046mm, and change the tracking force a variable amount depending on where the centre of gravity of the tone arm is. My SRA was consistently 95-96 degrees, and I suspect the 15mm came from me thinking that is what I would have to do to get the SRA correct....sink the base in to the plinth!!
sarcher30
596 posts
 
Dinster, another way to change SRA is by placing a shim between the cartridge and headshell. Placing the shim behind the cartridge screws will have the same effect as lowering the back of the arm. Of course if you have to lower the back of the cartridge so much that it drags on the record then there is something very wrong.

Using a shim is not an ideal solution but it will at least let you hear if achieving 92 degrees with that cart is a good thing or not.

I find it hard to believe your calculations for overhang change are accurate. They don't jive with my experiments. Could your decimal placement be off?
peterayer
1,382 posts
 
I use a Mint LP arc-type protractor and looked at the alignment with slightly different SRA angles. The stylus tip basically shifted from the center of the inscribed arc line to the outer or inner edge of that line, and it is a very thin line. I can not really hear a difference in that small a change to overhang.
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