I have HD580's that I usually use plugged into my y1 / mini^3 combo. The mini^3 has a 3.5mm terminal, so I use a kind of sketchy and awkward 1/4" to mini adapter to plug them in. Since the adapter and the length of the stock cable are inconvenient, I figured I would get a new 1/4" cable and then strip and re-terminate the old one.
I cut off the 1/4" jack and stripped some of the jacket to expose the wires. Something about these wires is a bit off, though. They're insulated somehow - my ohmeter reads no connection - and I can't tin them. The solder just doesn't stick. So it seems like each of the copper strands has some kind of coating, but I can't figure out what it is (it seems invisible) and I don't know how to get it off.