Does "perfect alignment of cart" eliminate 100% ?

None of the currently popular protractors use Stevenson, as far as I know, because Stevenson is slightly out of favor compared to Baerwald and Lofgren A, in that order of preference. You might google it to see if there is something available. There is a rudimentary protractor available on Vinyl Engine for free, but you have to print it at 1:1 ratio and mount it in some rigid substrate in order to use it accurately. Stevenson gives an inner null point at about 60mm, which is at the innermost of any inner grooves. I recently saw some measurements of typical LPs, and in many cases the grooves had run out before the 60mm radius from the spindle as centerpoint, i.e., the true inner r was >60mm. This means that in some cases Stevenson will not give you two null points over the course of an LP, only the outer one. Having said all that, if you have a vintage Japanese tonearm, chances are it was optimized for Stevenson (In that the offset angle of the headshell is best for Stevenson alignment), and you might therefore want to use it. Finally, don't get overly obsessed with this issue; it ain't worth it.

You can download a Stevenson protractor at the link below. Actually, it combines Baerwald and Lofgren (presumably "B"), too. I've never had any problem printing the protractor at 1:1 onto an inexpensive photo paper. Works fine for me. The only possible caveat is that you have to line it up to the exact pivot point of your tonearm, which I understand is difficult with some arms. Go the the link below and click on the KWillis Universal Accutrak Protractor Version 2.
-Bob

http://www.vinylengine.com/cartridge-alignment-protractors.shtml

Does a 12" inch help reduce the IGD ?

In short, is it a majority of us experiencing IGD or some of you guys can claim that you can play most of your LPs w/out any IGD ?

What cartridge are you using? My understanding is some carts are going to give a little more IGD than others, even if they excel in other areas.

I'm using an AT440MLa on a Technics 1200. Not the highest-fi setup, but the AT tracks well, and I don't hear any IGD.

And for the record, I set it up with the TT Basics mirror protractor(with a string taped to the sight line to help make sure it was pointed at the pivot).

Eric