I cut off the 3.5mm jack and soldered on a mini XLR connector. I kept the factory wires in place. First, I didn’t think the probable quality gains would be worth installing new wires (mmcx at the cups). Second, the XLR connector met my goal of allowing cable extensions and use with any amp regardless of connector type.
The combo of Yaxi pads, the right amp, and a warmer DAC helps keep the PortaPro’s whining treble under control. But, even after the mods they are still outclassed in every way by the HD-58X.