Hi Larry (Cello), Doug, all ...
Every time I'm around Frank, I learn/modify my knowledge base.
About 6 months ago, I had a Lyra Parnassus in house. This cartridge has an extremely tall cantilever. I got to thinking about this (there you go again ...Thom).
With a mirrored surface like the one on my protractor, it seemed to make sense to perform an initial azimuth setting referenced to the stylus instead of starting with a horizontal headshell. The stylus is after all, the business end of things.
Of course, I got in the habit of doing this with all of my cartridges as I got used to sighting in on the stylus.
At the RMAF, I gave my 'table a preliminary setup on 4 hours' sleep - knowing that Frank would pass by to do the final tuning the next morning. A fellow can get pretty lazy (tired?) knowing that Herr Schröder will ride into town on his white horse.
Frank took one look from a few feet away and noticed the slight tilt in the headshell. He commented that there's no way that he would trust his own eyes to perform the initial setting by referencing to the stylus.
Of course I saw this tilt, but I viewed it as an indicator that the stylus was not perpendicular to the body - as evidence of manufacturing tolerances needing to be compensated for.
What's interesting about all of this (yes ... there is a point to this story) is that I found that by using this technique, I could still dial in a sweet spot in the azimuth. It was just not *the* sweet spot. Just as with VTA/SRA, you can get false nulls at various points along the adjustment continuum.
We've seen this with VTA/SRA adjustment, where you can drop the arm post so much as to actually start to increase the high frequency content in the playback.
With respect to azimuth, you can be off by a relatively large amount (let's say, 2 degrees for sake of argument) and within this range, find a place where everything locks in (let's call this place 2.15 degrees in this example).
This "locked in" place can end up being a false null, with the true zero point (again, just an example) being a rotation of perhaps .2 degrees.
The moral of this story is that starting with a level headshell is the safest place to start your adjustments from.
Cheers,
Thom @ Galibler