mr dave

like LLSS said, it's probably the input jack in the amp.

if you're mostly concerned about the bass and its electronics try plugging it into anything else and see if you still get the signal interruption.

the easiest way to check the line is to run your fingers along the length of your signal chain, along the entirety of the cables from the instrument straight through to the amp. the crackling will be worse the closer it gets to the source of the issue. in your case it definitely sounds like the amp.

more often than not it's due to dust or rust. if you've moved it around (or from Aus to NZ) and it's gotten cruddy i'd start with some compressed air into the input then some kind of moistened cotton swab (like for cleaning your ears) and rub it around in there to clean anything stuck on the contacts.

if it's rust then you can use a pen and some fine sandpaper. just wrap the sandpaper around the pen / pencil, stick it in the hole and twirl it around a few times to grind away the rust. it'll work for the instrument just as well as the amp. although it's generally got to be a pretty old and neglected piece of gear to get rusty.

unfortunately it's easier to fix a crappy input jack in an instrument than it is in an amp. you'll likely need to bring it to an electronics repair shop if it's something internal. your local music store should be able to refer you to a local business that can handle your issue if you want to take things that far.

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