"Buzz Feiten was experiencing operational difficulties of this nature when he decided he was mad as hell and wasn't gonna take it anymore. "The guitar was set up perfectly, I was doing everything right, but still, the first three frets were terribly sharp," ....Curious, he started checking his other instruments on an accurate tuner - he found them consistently sharp near the headstock, and flat above the 12th fret. "That meant that the nut was in the wrong place, and has been for over 400 years," he says."
This is one of the more peculiar claims Buzz makes without offering any verifiable evidence in support. The only thing that could cause this is if the nut is too high. I work on around six hundred guitars a year and I’ve never heard one in which the first three frets sound sharp if it had been properly built and set up. In fact, the reverse is true. The fixed value for compensation at the 12th fret tends to result in the first fret receiving more compensation than it needs, resulting in a slight flattening of the note. The same thing causes the flattening above the 12th fret (see my explanation here) The only explanation for this is either that Buzz's guitar wasn't properly set up or that he was mistaking the sharpness of the A-flat in the E major chord - which is normal in a guitar properly tuned to equal temperament - for an error in the placement of the first fret. Compensating nut systems such as Earvana (based on the same principles employed by Stephen Delft are designed to overcome this specific problem but cannot have any effect on the sound of chords in any position other than the first position, so they are really only suitable for strummers who never play more than three open chords. To achieve the same effect on barred chords with a capo would require dividing the fret up into six sections and moving them around each time you changed chords...
There are guitars that attempt to do this but because their makers also do not seem to understand the principles of equal temperament it seems to me they are up the same technological blind alley since such guitars could be designed only to play in one key.
A more sensible approach to guitar intonation, based on sound thinking without overtones of commercial exploitation can be found here:
Improvement of Intonation and Playability of Guitar Fingerboards
