Unusual string rattle/vibrations?

[SeanTracey]

If you look at the post I have in the General Guitar Chat board about my Maton EBG808, you'll see that I'm having some trouble with my new Maton in that I'm getting some weird rattling from the strings - and I've just noticed it's happening on my Avalon too

Although something is really really annoying me about it, and it's not the guitar's fault. I'm experiencing rattling from the body, not fret buzz, when I fingerpick the strings (I play bare-tipped so I hit the strings quite hard, not like a player with nails) and especially when I play open harmonics. Maybe if Jim sees this he could give some advice? It's so hard to tell where the rattle is coming from...I think it's coming from the bridge or inside the guitar. It's not just one string either, it can come from most of them and it's ruining the sound of the guitar because it leaves a buzzing undertone any help would be great.

Anyone any ideas? There's more info on the other thread. It's not half as bad on the Avalon as it is on the Maton, but it's happening nevertheless, especially with open harmonics (G and B strings on the Avalon, all over on the Maton).

EDIT: If it helps, when I capo the first fret on both guitars, the rattle disappears completely - possibly a problem with the nut?

[JB]

Although we'd need to inspect the guitar to be sure there are a few things that can causes strange buzzes / rattles for example a pick-up cable that may have come loose, or if you play with an already low action and the neck has straightened out a bit more ... also, a buzz from the nut can sound as though it's coming from the body, sound transference is a weird thing somethings.

[SeanTracey]

I think I've narrowed it down to the G and B strings on both guitars only, which is quite unusual. The Maton is definitely more noticable than the Avalon but it's there and can be heard on both guitars. Only seems to happen when you dig in hard with the fingers and harmonics ring with a particularly juicy rattle. Would you have any suggestions I could try at home before bringing it to a pro Jim? Thanks for the help man.

[Darach]

sounds like a carbon copy of the collings problem I described, A, D and G strings all bucked like crazy...it was a "nut job", first fret buzz...
took it to a local shop (Musician Inc) who built up the nutslots, filed them to the right height and in about 15mins it was like a different guitar, ringing like a bell!