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VTF, VTA, SRA, and 92 degrees - question

I'm familiar with the logic that has been out there for a while about setting SRA at 92 degrees for what is considered the optimal styus position, based on a lot of analysis done by Elison and others. My question is, if VTF and VTA are set per cart maker's recommendations (let's discount Anti-skate for this discussion even though it would come into play), then wouldn't the SRA be automatically set optimally per the manufacturer's intention? Assume a cart that is built to the company's design parameters - no bent cantilever, no offset stylus etc.

Take a Benz cart for example. Many (if not all) of them specify a VTA of 20 degrees. So if VTF (and yes A-S) and arm height are set so that when all's said and done the VTA is 20 degrees, isn't that what it *should* be set at based on how Benz expects that cart to perform?

I ask because I set the SRA on my Benz to 92 degrees going by that camp, and when I checked the SRA it was at - guess what - about 22 degrees. That kind of suggests Benz expects the stylus to be at 90 degrees relative to the record. Isn't that how they've designed it? Don't I run the risk of having to compensate in other ways if the cart winds up exhibiting tracking problems at an SRA that does not support the specified VTA?
tonyptony
tonyptony OP
617 posts
 
Yes, you're right Peter. I guess my real concern is how much / whether a non optimal SRA can impact tracking ability. With everything set the way it is, I'm running a VTF of just under 2.1 grams for good tracking. That's a bit above the magic 1.9 grams that practically every bit on info I can find says is "correct" for the Benz Wood of my vintage. I'm not sure I understand what (if anything) the relationship is between SRA, tracking ability, and tracking force.
dinster
76 posts
 
The difficulty with VTA is that it is the angle between the record, and a line joining the tip of the stylus with the fulcrum...wherever that is. It is not the same as the "cantilever angle"! It is usually about 2 degrees more than the cantilever angle, depending on the length of the cantilever and height of the diamond. It seems that no cartridge has the "gold standard" setup (VTA 20 and SRA 92), they all seem to be out, often by quite a large margin. So I'm not sure what to do about this. Mine sounds brilliant with the tone arm near horizontal, which gives a cantilever angle of 22 degrees and an SRA of about 95 degrees, to correct the angles I would have to drop the tonearm base by about 15mm, and I'm sure the mechanical problems associated would make things worse (on an 11 inch arm 1 degree change in SRA equates to over 5mm change in arm height!!). I think the jury is still out on this one, perhaps the best is to set by ear from horizontal. I suppose I'm as confused as most everyone else:)
tonyptony OP
617 posts
 
Well, with all the measuring tools, calibrated blocks, and digital photos I have I think (!) I can get back to where I am now. I'm going to try again by starting with the cart at horizontal and see what happens from there.
brf
1,715 posts
 
Tony, can you hear any difference between 1 degree changes?
sarcher30
596 posts
 
Dinster, you could try putting a 2mm shim on the back of the cartridge between the headshell and cart. This will angle the back of the cart down and get you much closer to 92 degrees. I have a little brass shim for this purpose and it works well. I have a cart that needs this shim in the front because I can't raise the back of the arm high enough without it.
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