I've tried mixing several of them, in example cutting the jack from a set with only one earbud working, and connecting it to a set with 2 earbuds working but no jack; or adding a working earbud to a set with only one earbud working.
I didn't manage to recover any of them.
I've seen many tutorials on youtube and read many pages, and I don't think there is anything I'm doing wrong.
It should be as easy as stripping the insulation, separating the wires and removing the smaller insulation and then connecting them, making sure colors match.
I've tried stripping the thin-colored insulation either by fire (lighter), sand paper or with the soldering iron, but the result is still the same.
As a final trial, I cut the cable of a working earbud, and then tried to connect it back, so that I was expecting it to go back to its working status, but it didn't.
I tried just by connecting manually the 2 ground wires and 2 signal (coloured wire) after removing the insulation, and it didn't work;
I tried wrapping and it didn't work;
I tried soldering and it didn't work.
How is that possible?
I can't understand where I'm failing.
All of the earbuds are cheap Chinese products, but I don't think it should make a difference