My A string rattles at the nut

[Low_End_Theory]

^^ What can I do about this? Do I have to replace the nut?

[millsbass5]

Are BOTH adjustment screws firmly touching the base of the bridge?(The part of the bridge that mounts to the body.)

[20db pad]

If it's a Fender style headstock, you have to wind extra wraps of string on the tuning post. By winding these extra wraps down the post as close to the bottom you can get, it gives an angle that firmly seats the string in the nut. This prevents the A string buzz.

If you press the length of string between the nut and the tuning post down into the face of the headstock, you'll notice that the buzz will be gone if you play the A string. This is a sign that you simply need more string on the tuning post.

[NickInMesa]

I suppose it only happens when you play the open A string? And that when you do it does not change the sound of your bass?

The pickups pick up (duh!) the string vibrations at their level.

The rattle you hear is air vibration picked up by your ear.

I suppose it's aggravating but it should not do any big harm to your sound.

Changing the nut will not harm either.

[RavynWolf]

Originally Posted by NickInMesa

I suppose it only happens when you play the open A string? And that when you do it does not change the sound of your bass?

The pickups pick up (duh!) the string vibrations at their level.

The rattle you hear is air vibration picked up by your ear.

I suppose it's aggravating but it should not do any big harm to your sound.

Changing the nut will not harm either.

Perfectly put.
One thing to bear in mind however; when posting a new thread, be sure it is in the right section. There is no need to get a lecture from a mod or something :P.
In another note, see if the screws on the truss rod cover are loose and resonating; I had this problem once.

Ravyn