Electrical power is produced at a generator plant hundreds, or thousands, of miles from our homes. It travels via a hodgepodge of aluminum, copper, transformers, fuses, circuit-breakers, conditioners, meters and other devices until, finally, it makes a tiny journey a few feet from your wall outlet to the device it's destined to power.

No, replacing a perfectly functional basic cord with an exotic one won't improve the sound.

As I said, if the change you noticed is real, your house wiring was defective. Not impossible at all, from the conditions you describe.