As I understand the physics of it, as you lower the tailpiece you increase it's mechanical coupling to the guitar body. By rights this should result in increased sustain. In my experience I have never been able to tell the difference on any guitar I worked on. Some customers claimed they could. This would be because any vibration beyond the saddle can have a dampening effect at the bridge. The difference is negligible at best.
The downside is that an increase in break angle is an increase in stress at the point the string crosses the saddle. In extreme cases you may have more string breakage.
I tend to set them up just like Light suggested.
One further note: If you decide to adjust your stop tailpiece, at least remove all the tension from the strings and use a quarter to turn the studs. A screwdriver will chew up the slots every time. They make a wrench to do this.
Muttley, I will take my beating now
hehe, no beating or otherwise yout understanding is sound I guess but one of your conclusions is not right. I'll try and help you think about it some more..
Lets just have a look at what goes on in mechanical and physical terms around the bridge. It will give us an understanding of what we should expect, then we can see if our experience backs it up.
First if you have buzzing due to too little break angle you need to increase the break. What you effectively have in that situation is a string that is not anchored correctly and therefore a longer string length than you should have. There should be a point on the saddle at which the string is "fixed" and it forms a "node of vibration, ditto the nut. I can elaborate on the manner in which the string behind the bridge behaves if anyone wants but now for the sake of argument ignore it acoustically because for our purpose it is irrelevant.
The string behind the bridge is more important when you consider the way it imparts a downward force through the bridge. What you have is pretty much the same as the force in a bow and arrow type arrangement. The more the string is drawn back the greater the force. On a guitar this force is static and wants to push the bridge down. The bridge resists the force. You can calculate the force and if anyone wants it I can post the formula.
You say you expect the coupling of the two to be increased if the downward force is increased that is correct. Have another think about what dictates sustain/decay and volume/amplitude as the two are linked. When the string is plucked a given amount of energy is put into the string. That energy gives us our amplitude and decay, as the string vibrates you can only have a certain amount of one or the other, more sustain equals less volume and vice versa. As the string loses energy the amplitude drops and the vibration decays. The energy is lost in several ways but in this example the most important is the energy lost via the bridge and the nut. With a higher break angle the energy in the string is encouraged to leave via the bridge faster than it would if the break angle were less. This results in LESS sustain as the energy is lost faster. Thats the theory and what actually happens.
How does it effect the tone or note produced. Well as most have stated it has less effect on an electric. The reason for this is that the note is being produced as a result of the pickup detecting the movement in the string and converting it into an electrical signal. Also a lot more of the strings ebergy is reflected back down the string as on a n acoustic it is encouraged to move the soundboard. The relationship between the strings vibration and the electrical signal is more forgiving than the way an acoustic handles the transfer of energy, but the sustain will be less the greater the break angle.
An acoustic or archtop converts the strings energy differently. The energy in the string that leaves the bridge makes the soundboard vibrate and it is this that amplifies the sound. So the greater the break angle once again the greater the initial amplitude or volume and the faster the decay. On an archtop this has a marked effect.
Violin family instruments are different in one distinct way. Despite sharing exactly the same mechanics and physics in terms of the string and the break angle. The energy that is being put into the string is a constant supply from the bow rather than a finite amount from a pick. This is why soundposts work in violins, they couple the front and back and allow the energy to pass faster and further around the instrument. That also explains why they are not really a good idea on plucked instruments and not used on archtop guitars.
You can see why I ignored the string behind the bridge now can't you. This post is far too long already...
Oh and if your breaking strings at the saddle you need to make sure it is clean and allows the string to move over it smoothly just the same as a nut slot. The difference of a few degrees break angle will not kink or work harden the string excessively so it shouldn't be a problem. Look for rough or burred edges instead.
Or does it really matter?
