Cartridge azimuth adjustment using a voltmeter and a test lp

The issue is that the coils have the proper geometric relationship to the record. Cartridges now a days are well constructed the stylus being in the proper relationship to the coils. The parameter most affected is separation. Thus you can assume that if the stylus is perfectly perpendicular to the groove azimuth and separation are at their best.
The best and easiest way to do this is to align the cartridge, set VTF, place a pocket mirror on the platter and the stylus on it. View the stylus directly from the front with good lighting and adjust the azimuth until you see a perfectly symmetrical "hourglass" (the stylus and it's reflection in the mirror) The mirror greatly increases your accuracy in this adjustment. This is also the approach that will minimize record wear even if the coils do not have the exact correct relationship to the stylus. IMHO you will not do significantly better with meters or oscilloscopes. If your cartridge is poorly made you will align the coils, miss align the stylus and potentially wear out your records. All you need is a pocket mirror and a sharp eye.
It is also possible to do this by viewing the cantilever and it's reflection in the mirror. They have to be right in line with each other. 
Geoffkait, as luck would have it you don't have to turn up your hearing aids before you try this and please don't try to plug the mirror in.

Several months ago I found this method of adjusting azimuth by ear.
It works brilliantly.
http://durand-tonearms.com/Support/Support/azimuth.html

The best way to set the azimuth is by ear (see the note at bottom of this page). Note that if you hear a defective azimuth adjustment as an obvious problem of balance--if the sound is predominantly to the left or the right--, that could be because the azimuth is off (er, check the balance on your preamplifier first, of course!). But there could be many other causes, such as problem with room acoustics, deficient electronic component in one channel, etc. It's best to first ensure that there's nothing unbalanced in the rest of the system before attributing the problem to azimuth. It is however true that a center image can sound slightly off center if the azimuth if not perfectly adjusted.

Here are some tips to help you with this process:

Use a mono recording with relatively sparse material (for example, of a female vocalist). As you adjust the azimuth, you will perceive that the voice has the best “presence” when the adjustment is right on; that indicates that the stylus is perfectly vertical and centered in the groove; if it is even slightly off, the voice will sound somewhat recessed and unfocused. There is a very fine line between being right on, or not quite there yet; usually, a fraction of a degree is all it takes. So you really have to be very subtle when adjusting this parameter. Start with the cartridge vertical. This is just a starting point; remember that with most cartridges, the stylus is not exactly vertical, so just looking at the cartridge won't help much. A perfectly vertical stylus is what we are trying to achieve, and that's not something you can see with the naked eye.

Before you start changing the azimuth, listen to a short excerpt (2-3 minutes) several times. Identify as many elements as you can: the different vowels the singer is singing, the consonants, the mouth noises; then listen to the instruments: try to pay attention to each one individually. Is there perhaps one that seems to be more separated from the others? Don't listen to instruments or voices in the low register, they won't tell you much in this process. Percussion instruments in the middle or high register can be very useful: listen to the attack, then the decay.

Once you think that you've identified one instrument/voice that you "know" well on that recording, modify the azimuth, in one direction or the other. Let's say, you start by going toward the left (armwand rotated counterclockwise); rotate the arm by a very small amount--when you get close to the right spot, the rotation can be a fraction of degree. Listen to what happened. Then move again, in the same direction. Listen again. Is the sound getting more present, or not? Is the instrument getting more 3-D like, perhaps moving to the front a little, perhaps gaining more separation from the others? Or perhaps nothing changed, or it got worse (more recessed, less focused). Modify again, in the same direction. If nothing is improving, you might be going in the wrong direction. Come back to vertical, (on the Talea™ you can follow your changes on the little scale in the azimuth window) and do the same procedure in the other direction (clockwise). At some point, the sound will seem to change for the better. If it isn't, remember that some cartridges are less sensitive than others to azimuth changes. Or perhaps, you're exhausted by now and can't focus anymore. Don't worry, leave it aside for a while, and just enjoy listening to music.

Note that it's not impossible that the best sound is with the cartridge perfectly vertical! Sometimes the stylus is perfectly aligned.
Some possible clues that the azimuth setting is good:
- Source is larger
- In some systems source is closer (with more depth of stage)
- The sound you are focusing on is more separated from the others than before (more 3-D like)
- Sound source seems louder (consequence of previous points)
- More difficult: trueness of timbre. Listen to instrumental timbres (attacks, decay), as well as particularity of vocal timbre (sibillance and other subtle noises at beginning or ending of consonants, etc)

As with any fine adjustment, it takes time and patience to get it right. It's the same thing with tracking force and VTA/SRA adjustments: you can do it by eye, or follow the manufacturer's recommended setting, and hope for the best. Or you can experiment, try other settings just to see what happens, and suddenly discover uncharted territories. Through practice, your ears will get better at hearing the fine differences, and this in turn will take you to new heights of musical enjoyment.
Nobody said playing vinyl was instant gratification...

Just as a performer needs to understand how to take advantage of his fine instrument, anyone who has engaged for a significant period of time with the setup of a sophisticated tonearm knows that it can take a very long time to understand how it reacts to minute variations and how to anticipate its reactions and play with them. The more you play with it, the more you realize what it can do and how to make it sound its best, and the more it gives you back. And when you get it right, you can sit back and enjoy the new level you've just reached in your analog experience!
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Note: There have been other methods suggested in the past. A particularly popular one was offered by Victor Khomenko in the late 90s and seems to have been widely accepted since. In our experiments, we've found that, while this method works very well at a given frequency (most people seem to use a 1 KHz tone for this purpose), it is unfortunately not consistent throughout the frequency range found in music. We discovered that after adjusting the azimuth for perfect balance at 1 KHz with this method, voltage readings with a 100 Hz and a 8 KHz tone give widely different results; one channel would be greatly emphasized at the lower frequency, and the other one at the higher frequency. So while the method is theoretically sound, it fails to address the reality of the musical signal, which is far more complex than a single sine tone. So, until a better and more reliable method is established, our ears will do nicely... and they're free...
Additional note: to be fair, it has been suggested that crosstalk is not constant on all cartridges. Some cartridges (a few?) demonstrate excellent consistency across their frequency range, while many don't. For what it's worth...

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.