Cartridge azimuth adjustment using a voltmeter and a test lp

I agree on the importance of correct azimuth.  Critical azimuth setting IMO is more important than critical horizontal tracking setting which occupies so much of our posts and energies, it seems.

Just a few comments.  I begin with trying to set the cartridge level by viewing its reflection in a playing recording and making it parallel to the cartridge.  I use an Audio Technica cartridge, which I think is more likely to have the cantilever and stylus placed symmetrically than smaller volume producers. If I had a more hand made device I would try hard as I can to see the stylus vertically in the groove.  But this is only a starting point.

The final setting must, I think, be by ear.  I would not use a mono recording; I would use a stereo recording with the biggest sound stage in my collection, classical preferably.  I would make very small adjustment with the aim of maximizing soundstage for that would maximize separation which is the object of correct azimuth.

For those that use VPI unipivot arms I highly recommend the second pivot option.  Even if it accomplished nothing else, and it does, it makes setting azimuth crazy easy.  You just dial it in.  I was VERY pleasantly surprised at what a small difference in azimuth can make in enlarging the soundstage.  You can't do it on the fly, but it works out easily enough.

Thank you everyone for your comments and advice.  
As i said I know that there are many methods by which to set azimuth and it is very difficult to measure.  In fact my interest in using a voltage output measure is to see how that might differ in results with how I set-up the cartridge currently, which I did by ear:  first I get in the ballpark by making sure the cartridge is aligned properly and then confirm that with a mirror and magnifying glass to check the position of the cantilever and stylus....and then I listen.  To me it starts sounding right when listening to vocals, or a female vocal to be more precise, and her presence becomes more defined and localized, and in the right (or let's say in better) proportion to the rest of the musicians and soundstage.  From my testing when the voice starts sounding too diffuse and laterally too wide, which also means that the soundstage also seems to flatten, then the azimuth is off.  And I say the azimuth is off only because by changing it I notice somewhat the better definition and focus when I change the azimuth (the JMW10 allows for this type of adjustment).

@lewn
I am surprised you never heard of measuring output voltage at the amplifier terminal as almost all who use the voltmeter (vs Fozgometer)  method seem to suggest doing exactly that- for example Michael Fremer in a Stereophile article on Azmuth adjustment writes the following: 
"Whether or not you've built the box, the next step is to set the voltmeter to low AC volts (around 5 volts) and put the probes in the left channel of your amplifier's speaker terminals....."
He then repeats this for the right.
And there are countless others that suggest the same thing.  And to your point, if you are going to use this method, why there vs measuring from the speakers?  To be clear I am not suggesting this is necessarily a good method- I am just curious for comparison to what I have done already.  If anything, as you also suggest, I would measure from the phono using a Fozgometer - but barring that why amp terminal vs speakers since all the imbalance, if any,  has already "happened".  And because I am not sold on measurements per se and I am just experimenting, I do not really want to drop $300 on a Fozgometer either.
@millercarbon
I did indeed read Peter's advice on this- now if he finally did come out with his long promised cartridge set-up device I would actually take the plunge!
@mrubey 
I am indeed doubtful that 1Khz sweep from a test record does the trick- I am not at all surprised that that at different frequencies azimuth setting doesn't jibe with what you get at 1Khz.

Anyway, thanks for all the responses- it is always great to hear from others more experienced than myself- and I will do another set-up round using all your insight to see what I get.

But let me know if you have any thoughts about taking a measurement form the amp terminal and speaker terminal- I am very skeptical of the insistence on using the former. 

Hi,
my understnding is that cartridges with low to middle seperation figures are more affected by incorrect azimuth compared to ones with high figures. Reason behind is that a high seperation cartridge even if loosing some db of incorrect azimuth will still maintain high figures. I do not imply that azimuth should be overlooked but in my opinion is not the top priority in cartridge alignment. Having so much off centre image, as mentinoed above is not only the outcome of incorrect azimuth but HTA would be way off, or in case of a tubed phono tubes mu is not closely matched (just mentioning 2 factors). All methods stated above are a fine way of checking/adjusting azimuth but practically we are talking of minor vertical adjustment (if it is too high change the cartridge or the arm). In the end a mirror for checking would be fine to have at least the min db loss. 

Pgastone, having written so much about how to adjust azimuth electronically, which is to say so that the measured crosstalk from one channel to another is minimized, I have come in my old age to agree with Mijostyn in that the net benefit of just having the stylus sit squarely in the groove is greater than the net benefit of minimizing crosstalk, if it means positioning the stylus tip asymmetrically in the groove. So I no longer mess around with ways to measure crosstalk.

mijostyn.....I suspect you are way off. Most mirrors are silvered in the back and therefore you’ll have a great deal of error with the stylus resting on the glass with a few mm to the silver. If this is your tact, using a mirror from an old SLR camera.....you’ll have a much better chance of accuracy. I use the Fozgometer with its test record. Done a few times, with brand new batteries, the soundstage widened considerably...more depth, air, etc.  Be the way, I'm wiring the Foz at the output of the phono preamp.