Ok. The guitar has been back to the PRS dealer. Tech spent about 45 mins checking it over making sure the set up was ok (and reducing the neck relief). No, he couldn’t find anything wrong. No lifted fret or high fret; nut and tuners were all good; and action wasn’t too low. He tried a different B string and still the dead note was there. The only thing left to would be to return to PRS Tech centre.
I declined that option for the following reason:-
Before taking it back to retailer I did a lot more research. In the PRS forums there are quite a few (loads) of pages about this issue. A lot of it is nonsense spouted by the usual ill-informed forum idiots. But amongst the other posts there are some incites to what’s happening and that I am by no means alone in noticing this problem.
To summarise what I have understood:-
All guitars (stringed instruments) suffer to some extent from this. to quote a quote from one posting
"John Suhr did leave an interesting comment:"
'
All guitars will have a dead spot some place unless they are made out of concrete.
The more alive the guitar is the more dead spots you will have. PRS are not exempt either and even had a kit they would ship you to try and move the dead spot to an area that doesn't bug you as much. Changing mass in the headstock will move it like even different tuning gear buttons
A good finger vibrato would go a long way in letting the note regenerate itself as well !'
My understanding of the major reason it happens is due to the neck having one or more resonate frequencies. If that coincides with the frequency of the note being played we can get a cancelling of the sustain if it is out of phase and an increase in the sustain if it’s in phase.
The best analogy to this hypothesis is if you have two waves on the water approaching each other where the peaks and troughs coincide (in phase) we get heightened peaks and lowered troughs. Where they are 90degrees out of phase we get a cancellation. Of course this isn’t quite what happens with the water as the waves will carry on after meeting with more or less the same energy and in their original direction. With the guitar the note loses energy much more quickly. Which is a function of the fact that higher frequencies require much more energy to continue (sustain) unless there is some external energy causing resonance. Phew!
An alternative explanation could be just that if the note frequency is the same as a resonant frequency of the neck; then that’s what is ‘stealing’ more of the energy from the note. A much simpler reason to understand; but not necessarily correct.
All this (at least in my mind) is why some people have this problem and some don’t. i.e. if the guitars resonant frequencies don’t correspond to a node point (fret) then it not as noticeable.
Other references.
http://www.logosfoundation.org/kursus/The Science of String Instruments.pdf
http://acoustics.org/pressroom/httpdocs/137th/fleischer.htmlMy final test to check this out was to add mass to the headstock (via 2 Shubb capos). The dead note disappeared from that B string 12 th fret. I didn’t check to see where it moved to.
I will just have to play that Mark Knopfler solo on my strat.
Take care
Styrr