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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
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.
sarcher30
596 posts
 
Peter, that sounds about right with small changes in SRA. With a 1 degree change in SRA the difference will be large enough to worry about.
bifwynne OP
2,206 posts
 
Folks, I make this post with a smile and a frown. Based on the good advice from Jonathan Carr and a few others, I've made arrangements to send my Kleos back to Lyra for a check up. The smile is that I am taking the advice of people who know what they're talking about. This way I'll know that my Kleos is in tip-top working order when it comes back in 6 to 8 weeks.

And that's why I am sad. :( I won't be able to use my Kleos for 6 to 8 weeks.

IMHO, this is one super-duper cartridge. I still have my S-S VPI Zephyr, but the Kleos is in another league.

What else can I say? :( I suppose, if this is the worst thing that ever happens to me, thank G-d.

Bruce
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