Buzz at the nut, help !

[Tom F]

I changed to different brand of medium strings, and now, both my A strings are buzzing at the nut. When I fret anywhere, it goes away. I am not hearing the strings buzzing on a fret, it seems to be from the nut (but you know how buzzes can show up in areas other than origination).

On the caliper, the old A is 0.46mm, the new is 0.41mm (0.017 and 0.016 in). Could that small of a change cause the nut to buzz from too much room in the slot?

[Brian Fortier]

Sounds as if the string lies too low in the nut groove.

[Mandobar]

i had this problem a week ago. turned out the nut on the end of my truss rod was loose.

[Celtic Saguaro]

One slot or both may be a bit too flat bottomed leaving a bad fit in the center for the smaller string. It would not take much side room at all in that case for it to start buzzing. If that's it, it may be easy to fix depending on how much clearance there is above the frets. If it's extra low the nut may need to be replaced.