Which has higher priority, overhang or VTA?

Every change  requires adjustment of all other parameters

That is in theory only. The best protractor only get you to the closest overhang and the VTA is in the same situation. My question is, with the same amount of error, which one makes the sound worse? For me, final adjustment is by ear. So, when you hear the best, one of those two is in the right position, which one?

IMO, VTA is more important !

Can anyone confirm the old expression for cartridge alignment that if you're off 1/10 degree in any direction of alignment the distortion increases by 100%?

Hopefully you are resetting the VTF with the scale surface at record height, whenever you adjust the VTA on your unipivot arm.  If not, that is what you are most likely hearing.  Raising the arm will decrease the VTF while lowering the arm will increase it.  The change in VTF will affect the SRA which will then affect the overhang.  As Stringreen said, every parameter must be correct.  Repetition and patience will be rewarded.  Choosing between two evils will not.

Isn’t the cartridge/stylus type being adjusted also a prime consideration here?

My personal experience - my standard Denon DL103 seemed to perform very well - setting it up using the free protractors that are available on the web - overhang was close to optimal, but being precise did not seem to impact SQ too much.

VTA did have a marginal effect on bass performance, but I found setting the cartridge such that it was parallel to the surface of a record of standard thickness had little impact when playing 200 gram vinyl

In comparison - my Soundsmith modified version of the Denon DL103 was almost the complete opposite ...
- I initially set it up using the free protractor - then a friend brought over his precision glass protractor.
- Overhang setup was now extremely precise
- Cantilever alignment (as opposed to aligning the cartridge body) was also extremely precise

The improvement using the precision protractor was very noticeable with this particular cartridge.

I still find VTA is less of an issue as long as the cartridge is parallel to the record surface, but ensuring the other settings were precise brought out the very best in this cartridge

I’m still very much a newbie at understanding the "eccentricities" of phono related issues, but I rely on what my ears tell me and for me, using a precision protractor to setup the SS modified DL103 is the only way to go. For the standard DL103 - it was not so demanding

Does the level of precision depend on stylus type ?

The few stylus tyoes I know about are...
- conical (as on my standard DL103)
- elliptical
- Contact Line
- Shibata Style
- Optimized Contour Contact Line (as on my SS modified Denon 103)

Here’s a link that provides many details on this stuff:
http://www.sound-smith.com/articles/stylus-shape-information

Regards...

Some good points above, and my experience has been that VTA has a substantial impact on sound.  Conical styli are unaffected by VTA as they have a uniform cross-section from tip to base.  All other styli shapes are affected to greater or lesser degrees.  You should note that 1 or 2mm of VTA adjustment is quite a large change and shouldn't be necessary very often.  Perhaps you are simply becoming more sensitive to what VTA changes can do?

I respectfully disagree that changing VTA axiomatically changes other set-up parameters, however.  VTA adjustment systems move the entire arm assembly relative to the arm board/plinth and are intended to correct for minor differences in pressing thickness.  Provided that overhang, alignment, azimuth and VTF were correctly set for a uniform reference thickness to begin with, they will remain correct when adjusted to a different thickness.  Changes to those parameters can only occur if the thickness adjustment is incorrect for the pressing being played.  

Those changes are indeed audible, and a big reason why I very much prefer arms that have the ability to adjust VTA on the fly.  I believe your JMW can do that and you can hear when the adjustment is just right if so.  It does take repetition and patience to acquire the skill, but oh, so worth it.

There are a large number of threads here with all kinds of information on this point that you may wish to search for more background.  Many posters disagree with my opinions, many agree and many equivocate toward one datum over another.  One of the more entertaining aspects of the vinyl hobby.  The only real rule is:  Do what sounds good to you.

Good luck & happy listening!

Thank you all for your replies. Sometimes, I just wanted to find a scientific explanation on why I hear better with just a micro adjustment on the VTA. It seems many variables involved. I might just hit a sweet spot on overhang, or vta or vtf. And you are right, in the end, what sounds best to my ear are all that counted. 
THANK YOU

dangcaonguyen
Sometimes, I just wanted to find a scientific explanation on why I hear better with just a micro adjustment on the VTA.

Hi Dangcaonguyen
As explained in the ET 2 Tonearm manual by Bruce Thigpen..

Vertical Tracking Angle Adjustment (VTA) - Eminent Technology ET 2 Manual Part. 2

The full manual can be downloaded from here. Go to Support-manuals.

http://www.eminent-tech.com/main.html

Some text from a couple of sections.

From Page 51

Several articles have appeared which address the area of cartridge performance. Vertical Tracking Angle (VTA) and Stylus Rake Angle (SRA). We have designed the Model 2 tonearm to optimize the vertical tracking angle of the cartridge.

The angle that the cutterhead is placed at when a record is cut results in an included angle in the final disc. This included angle must be duplicated with the reproducing stylus or distortion will result. The problem today lies in standardization of the angle by record manufacturers and corresponding standardization by cartridge manufacturers. Presently most records are cut with resulting vertical angles between 16 and 20 degrees. The average vertical angles of cartridges manufactured today is slightly higher than 22 degrees. The result of this mismatch is less than optimum performance for many cartridges.

Although the vertical energy contained in a record represents approximately 40% of the total energy on the record (60% lateral). The distortion levels are dealing with are quite high. In some cases, the vertical performance with certain types of distortion can be improved from 2.5% to 1% or less.
.....in most cases, optimizing the vertical tracking angle will not affect the lateral performance (or frequency response, and tracking abilities) of a cartridge and the result is an overall improvement on cartridge sound and imaging. .......The correct vertical tracking angle is by no means the only way to improve phone cartridges but we believe standardization would represent an important step toward optimizing this medium.

Page 56 - Conclusions

1. Not all cartridges will be improved by using them at some angle other than the intended design angle. (The top of the cartridge parallel to the surface of a record)
   
2. The European record vertical cutting angle standard closely matches the vertical angles present in phono cartridges today. There is a need for a universal record cutting standard which closely matches this.
   
3. If the measuring vertical tracking angle of a cartridge is high (greater than 22 degrees) its vertical performance will probably be improved by tilting it back (2 or 3 degrees) (front goes up) to match present vertical angles on records.
   
4. If the measured vertical tracking angle of a cartridge is 18 to 20 degrees. It will probably perform best when its top is mounted parallel to the surface of the record.
   
5. Some cartridges are very sensitive to small changes in VTA, others are not.

Hope this is helpful
Happy Listening.

Thanks CT,
Calvin

" it seems to me, any time I change the VTA, the overhang is changing also."  Theoretically true.

But hard to see what the issue is here.  You can always reset overhang after adjusting for VTA/SRA.

But you really don't have to.  As a bit of high school trig will reveal, if you begin with a 10" level arm and raise (or lower) it by 2 degrees, you will shorten the overhang by about .006".

Not to worry.