I have a vintage single cutaway hollowbody acoustic archtop. It has a set neck. The action is medium-medium-low. I get a fretbuzz on almost all strings when fretting just above 12. It clears up for the final frets after 15. Yes, the problem is occurring where the neck joint is, but the set looks really sound. The fretboard does seem to angle up very slightly at this point. By the way, the end of the fretboard is, by design, off the body. That is, there is an intentional gap between the fretboard/and the body.
I just got the instrument and it came with electric strings (9s). A replaced them with acoustic 12s. I tecj adjusted the truss rod, and I didn't notice the buzz then. I didn't notice it with the light strings, but then again I didn't get into the upper registers. Could the neck have settled into a buzz based on the new string tension.
Readjust truss rod?
Go to lighter strings?
Avoid playing up there?...(I don't like that one)
Thanks for any help
The tech is on vacation and I'm anxious to figure this out.