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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
pbnaudio's avatar
pbnaudio
1,610 posts
 
VTA and SRA are basically the same, its just a matter of where you choose to measure. A better way of putting it may be they are 100 % related to each other.

I'd state that SRA is the most accurate measurement as it is where the interface to the vinyl is. What ever VTA ends up being with a SRA at 92' is just a matter of how accurate the stylus was adhered to the cantilever.

This measurement is of course to be taken at the right VTF as varying it will change the SRA.

Good Listening

Peter
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?
brf
1,715 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?
rodman99999
5,988 posts
 
"This measurement is of course to be taken at the right VTF as varying it will change the SRA." So will the thickness of the vinyl(ie: standard thin Columbia pressing vs 180 or 200 gram disc).
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.
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