VTF, VTA, SRA, and 92 degrees - question

I am sure some of you have noticed that different records seem to need a slightly different VTA. The reason for this is two-fold; first the LP is a different thickness. The second is the the cutter stylus on the cutterhead that cut the lacquer for the LP may have been set at a slightly different angle. This is why two LPs of the same thickness on the same label may still need to have two different settings.

The cutter stylus has the job of cutting the lacquer. To do this it is shaped a certain way, heated to a particular temperature, set to a particular angle (cutter height) and tracked at a certain pressure. What works on one day in the mastering lab may not work the second day as the lacquer can be different, even if only by temperature (they cut easier on warmer days for example). So the mastering engineer has to be constantly aware of the condition of the stylus and keeping test lacquers on on hand to get immediate feedback on the effectiveness of his settings.

So this may not be as exact a science as you all might be thinking- it is as much an art. The 92 degree value is an excellent approximation, just as is getting the front of the cartridge to be perfectly perpendicular to the LP surface. This is why it is helpful to be able to adjust the VTA on the fly, like you can do with the Triplanar tonearm.

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.

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".

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, 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!