Balanced XLR cables have been around since the first half of the 20th century.

By the way, no current consumer equipment has true balanced outputs and inputs. What they have are "differential" or "electronically balanced" outputs and inputs. The only way to have a real balanced circuit is to use transformers, which are way too expensive to use in consumer equipment. Transformers have the advantage of completely isolating the circuit from all external references, such as ground, chassis ground or the active circuit elements.