I've noticed an anoying thing about my new Ibanez EDB600. I get some strange vibration (quiet rattle) somewhere along the neck, especially when I pick or pluck E and A strings hard enough. It seems it's not fret buzz, and it doesn't originate in bridge saddles or nut, I guess. E.g. when I fret the E string about 7th fret, I still can hear it on the headstock side of the neck. Well, it's really a minor problem, or even not a problem at all, because it's very quiet and doesn't affect the amplified sound, and it's audible only when playing unplugged and playing hard. Besides, no other symptoms of truss rod problems: no bad curvature, no dead spots, solid feel. But still it's there, and I heard that the truss rod may vibrate when the gutter for it is too wide. Is this a probable explanation? How can I determine where the problem originates? I know the wise answer would be to go visit a technician, but maybe it's a generally known issue? Thanks.