The 3.55 mm headphone jack on my Denons snapped off inside the 6.35 mm adapter I was using ... before I ship them off to be re-cabled, if I soldered the stub of the jack that remains on my headphones to the severed end still stuck inside the adapter ... would it conduct sound? I tried just pressing them together and got nothing ... but maybe a little solder ... ?
Jumping in late, because from the way you put things it sounds like you might not have a clear idea of what's going on inside the jack. Pardon me in advance if that's not the case.
The jack doesn't conduct sound, it conducts electricity. The electrical audio signal generated at your player (or amp, computer, phone, etc) gets converted into sound waves at the headphones. The jack's function is to make electrical contact with whatever you are plugging into so the signal can flow through the cable into the headphones.
To that end, there are a number of wires involved which need to stay isolated for the signal to transmit properly. A standard stereo jack has three wires: Left channel signal, which makes contact at the tip of the jack, Right channel signal, in the middle, and Ground (electrical return path), closest to the collar. Each of those are conducted by a separate wire inside your cable, soldered individually to special contact points inside the collar of your jack. The jack itself is essentially a series of concentric metal rings separated by plastic (to keep the electrical signals separate). The Left signal is on the inside, Right is in the middle, and Ground is on the outside. Some headphones have four or more wires, but you get the idea.
So fixing a jack that snapped in half would require reconnecting each circle and making sure they don't short each other out, while also keeping the same mechanical strength and making sure the whole thing stayed exactly the same size, since otherwise it won't fit into the plug socket properly. Using a blob of solder to just "glue" the two broken pieces together would pretty much be certain to cause an electrical short between the different wires and fry your gear (or worse).
To make a long story short, the way you fix a broken jack is by cutting it off and replacing it with a new one
