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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

Showing 6 responses by tonyptony

tonyptony OP
614 posts
 
VTA and SRA are basically the same, its just a matter of where you choose to measure.

I'm not sure about this, Peter. Based on what I'm seeing with my Benz, they have the stylus set up so that at the specified 20 degree VTA the SRA appears to be dead 90 degrees, not 92. Almost too exact to be a mistake. So is this what they really intended as the nominal staring point, I wonder?
tonyptony OP
614 posts
 
I assume that you are using a digital microscope and overlaying the image with digital protractor to measure SRA. How are you measuring VTA?

Yes to your assumption. VTA is being measured in a similar manner, except for that I am measuring the angle of the cantilever relative to the horizontal surface of the record.

Using Expressimoaudio's 0 degree precision VTA block to insure measurement are with respect to an angle corrected image. Using a Supereyes B008 digital scope.
tonyptony OP
614 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.
tonyptony OP
614 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.
tonyptony OP
614 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.
tonyptony OP
614 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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