SteveL123 wrote: ↑
Mon May 22, 2017 5:07 pm
On my guitar with high tension carbon strings, moving the treble string 1 mm laterally does not cause a perceptible out of tune note or chord.
Then, I would surmise that the instrument in question has an intonation/setup issue. Yes, string gauge does affect intonation (thinner flattens and thicker sharpens), however if the instrument is set up as well as it can be for a particular string gauge there should not be problematic tuning issues. The guitar may have been setup up for higher tension strings and if the setup is good (neck relief, saddle compensation (and nut if the luthier was that precise), action height, fret height) then it should be possible to adjust for the different strings. If the frets were not positioned correctly...oops! If the use of higher tension strings corrects the problem, then the guitar is very sensitive to string gauge due to having been setup for higher tension strings. Note that higher tension strings will change the action height due to small changes in the neck relief and vertical pull on the bridge.