At what distance are balanced XLR cables needed?

If I can make some comments?

To clarify, the balanced cable can run as long as you want it to and the cost of the cable will have no bearing on the sound if:

The equipment supports the 600 ohm standard. If this is true you will not be able to hear any differences in cable, regardless of length.

Now this is not true of all high end audio equipment. Most of it does **not** support the standard, and so as a result people are still hearing differences in balanced cables.

The balanced standard was developed specifically to eliminate this problem! So you can see, supporting the standard is important if you want to eliminate the artifact (or 'sound') that all cables have. And yes, many well-known companies don't support the standard, and as far as I can tell, don't seem to know that one exists.

"cost of the cable will have no bearing on the sound if"

Can you explain why purity of metal becomes unimportant in balanced configuration?

Over 20 Feet.

Kijanki raises a good question of Ralph. And if all of the fussing with materials and geometry don't make a difference with balanced connections so long as the electronics comply with standards...well, what about unbalanced cables?

AFAIK, there are no such standards for unbalanced audio connections.

Kal