Originally Posted by I love tea:
“Which bit is the headphone jack?”
The bit on the end of the wire you plug into the source of the noise you are listening to
There are many and various reasons why headphones crackle. I know I repair professional versions more times than is good for me
By far the most common is a faulty cable. Where the cable enters the body of the plug or the headphones are common stress points. As the cable gets bent at these places the copper cores can fracture leading to intermittent connections that can make them crackle.
The cable can also break anywhere along it's length. Especially if it is prone to getting tangled. With experience you can actually locate the break just by feeling along the cable. Usually though you can provoke it by moving the cable around. If there is a break then you will find a position or two where you lose all sound.
Changing the plug is the easiest as you just chop the old one off and solder a new one on. A break at the headphone end might be repairable if there is a way to get into the headphone to get at where the cable ends up. My Sennheisers have a mini jack on the headphones so if the cable breaks I can just throw it away and replace it very easily.
Not so simple if the break is half way down the lead.
Unfortunately if you don't know one end of a soldering iron from the other then DIY repair might be out of the question. Though I have to say soldering thin wires onto a 3.5mm jack plug is not my favourite activity
It is always possible the socket on the player you are using is faulty. The socket can become detached from the circuit board and make intermittent contact. Gently moving the plug side to side might provoke it to crackle and cut out.
Again if you can use a soldering iron you might be able to solder the socket back in place. If you can get at it of course.
And rarer than you might think is the speaker unit in the headphone itself. If that is gone (not so easy to figure that one out believe me!) then you might be able to replace it. Again it all depends on whether you can get at it and have the skills required.
As tortfeasor suggests using a second pair of headphones and a second player is a good way to eliminate either player or headphones. If both pairs of headphones crackle in just one player but not another then it is the player. If your JVC headphones crackle in two different players but a second pair work fine in both then it is the JVCs at fault.