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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
ehaller
98 posts
 
I'm with Michael Fremer on this one: Set the SRA at 92 degrees, or as close as you are able to get it, and leave it. With my tonearm I can only achieve 91...good enough for me. I then adjust VTF and azimuth optimally....recheck SRA...and I'm done. The difference in vinyl thickness will have no audible effect...it's too small a difference to throw off the SRA. If I recall correctly, Fremer stated a 4mm adjustment in tonearm height will change SRA by 1 degree.
stringreen's avatar
stringreen
6,483 posts
 
One also must remember that as the record passes under the stylus and rides the slight (or excessive) warps, off centered spindle hole, etc., the VTA, the VTF, the Bias, etc....all the parameters are constantly changing. All we can do is get it "close".
tonyptony OP
617 posts
 
can you hear any difference between 1 degree changes?

Well, I was as careful with my Denon 103R in experimenting and I heard a difference between 92 and 90 degress with that cart, which has a plain old spherical stylus. But I really didn't mean my original post to be centered only around the sound. The end of my original post was where my real concern is - whether there is any relationship between SRA, VTA, and the ability to track.
dinster
76 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.
Sarcher30 (System | Threads | Answers | This Thread)

Thanks for that suggestion, I actually investigated making a series of wedged shims in different angles for this purpose, thought there may be a market for them, can't remember now why I didn't go ahead. Think I might still give it a try!
tonyptony OP
617 posts
 
I spent a good chunk of the afternoon realigning everything starting with setting the cart dead level. After tweaking and adjusting I think I can safely say that at least in my case it makes absolutely no difference in how the cart tracks, or the needed VTF and A-S. Both are practically identical to when I had the cart slightly tail up to get the 92 degree SRA. As to how it sounds, I think I like it a bit better tail up. It sounds clear and mellow (not soft), but I think I like that small extra bit of transient snap I was geting before.
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