Rustling noise out of A string

[DubDelay]

I have an old cheapo les Paul that sounds nice but it’s a bit wonky.

It had a similar problem and it was one of the machine heads was a bit damaged. The machine head off the D string created a similar sort of noise as you’re describing when I hit the E string. It took me ages to figure it out and now I just have a tiny bit of blue tac on it, can’t even see it.
 

If you try holding the E, D and G machine heads one at a time it would eliminate that sort of thing. It’s probably not the problem but no harm in checking. 

[DarkHeart]

I had an E string like that, turned out it was faulty, the inner was loose in the wrap, try a different string.

[NancyJohnson]

I've experienced this with a handful of basses over the years; an inconsistent rattling from an undetermined area of the bass and in general the noise only happens when you play one particular note.

It's a resonance frequency issue (like when crockery rattles when your TV makes a certain sound).  It's nothing to do with how short you cut strings, break angles, loose truss rods or rattling frets.  The most obvious loose part will be the springs on the bridge - which in general are the only things loose enough to rattle - just put a finger on the springs to test that. (Remember that it's not necessarily going to be the A string spring if you play the A string; it could be any spring/any string.)

Elsewhere, make sure everything is locked down tight, saddle grub screws, machine heads securely screwed in, bolts tight on the front of the tuners and if your tuners have changeable leafs, make sure they're firmly attached (and the nylon washers are intact).

Unlikely cause (but worth checking) might be in the control cavity, but shielded wires/batteries do not have the capacity to rattle.

My old Aria rattled like b*ggery, during one upgrade, I swapped out the BBOT bridge and that solved it, despite doing the spring test.  Perhaps it was a combination of things.

[MoonBassAlpha]

I had a weird thing that probably wouldn't occur on any other bass, but it took an age to track it down. I had convinced myself the truss rod was rattling as the neck is very stiff and doesn't need much tension on the nut.

It wasn't, it was the metal control cavity plate, despite the screws being as tight as they would go. A tiny amount of electrical tape between cover and body sorted it. 

[ezbass]

My new JMJ Mustang had a weird resonance on the open A and 12th fret harmonic. I went all over it trying to find the source. It turned out it was emanating from the nut slot. A quick pass with an nail Emery board fixed it.

[Skybone]

IIRC, G&L's have a grub screw on the side of the bridge in order to stop the saddles rattling. Maybe tighten the grub screw, as it sounds like a 'loose' saddle.

[wazdabaz]

50 minutes ago, Skybone said:

IIRC, G&L's have a grub screw on the side of the bridge in order to stop the saddles rattling. Maybe tighten the grub screw, as it sounds like a 'loose' saddle.

Could be an issue since that screw is long gone. But I did manage to tighten the saddles and test that part. The issues goes on. Besides, it happens on certain strings, not all of them (of the strings that go that saddle). I am starting to thing that I should visit a really experienced repairer. (For the story, I put a fresh new set of Dunlop MM super brights. After setting up the action/intonation I hear that noise on E and B strings. Things are getting intense

[Beedster]

On 19/03/2021 at 08:32, NancyJohnson said:

Remember that it's not necessarily going to be the A string spring if you play the A string; it could be any spring/any string.

Yep, so many people get that wrong "why would the G-string rattle when I play the A-string?", because it's the frequency of the note that causing the rattle, not the mechanical components of the string on which the note is played. We used to rehearse in studio which had so many loose and noisy items in the room that you could play a kind of mid-70's Dusseldorf school avante garde industrial music piece just by kwnoing which notes on which instruments were going to start the various bits of metal rattling and for how long