At what distance are balanced XLR cables needed?

Eldartford, 600ohm is output impedance and 600ohm is input impedance of power amp. Because of 2 to 1 division of the voltage output voltage of the driver (driving 1.2k total) has to be 2x higher - being equivalent to nominal signal driving 600ohms. Even if gain increase is on the power amp side driving 1.2k is not easy. Many preamps have hard time with 10x that. For instance Rowland in my 102 power amp uses additional amp just to increase input impedance from 10k to 40k.

"It makes a difference in what they can charge for the product, that much appears to be true."

Drubin, Absolutely - but on the other hand nothing suppose to make audible difference, according to calculations, but this cable is way better than very decent AQ King Cobra I had before (and it is only 0.5m XLR). What make clarity so much better? Dielectric? Metal? Who knows. I think Acoustic Zen knows (and they charge an arm and a leg for that).

The output impedance of a preamp has to be much power than 600 ohms in order to *drive* 600 ohms. Also, the output impedance at 5Hz should be the same as it is at 1KHz so there is no low frequency rolloff. You can see right away why most preamps will instantly loose bass if actually subjected to a 600 ohm load!

The 99.99999% figure quoted for purity is outright preposterous. Even if you could get that kind of purity in the metal you can't extrude it into wire and still have that. For example if you have Teflon insulation, the extrusion temperature is quite high, which is guaranteed to cause oxidation at a rapid rate. BTW this is why you don't see copper wire that is Teflon insulated.

I would suspect that bigger current would cause bigger voltage drops on said junctions (or impurities) everything else being equal.

Actually if you work the math the opposite is true- with no current at all then the minor resistances, odd diode effects and the like will become more prominent.

The 600 ohm standard was developed over 50 years ago and successfully eliminated cable variables. It made hifi possible- now it was possible to hang a set of microphones in the ideal location in any hall, without concern for where the recorder had to be to make that possible.

IOW the vast majority of all recordings use this technique. This is why a classic Mercury or RCA sounds better as you improve the playback- you don't hear cable problems in the recordings because there are none.

I have often marvelled at the fact that audiphiles are willing to pay large sums for cables, yet are often uninterested in a proven system that eliminates cable artifact altogether.

Think of it this way. If you have two cables and one sounds better than the other, right away you have to be suspicious of both. Why? Next year, the manufacturer of the 'better' cable will have a new model that is more expensive yet, and sounds better- we have all seen this! How about a system where the cheapest cable sounds as good as the best cable? Wouldn't that be something of interest?

I have often marvelled at the fact that audiphiles are willing to pay large sums for cables, yet are often uninterested in a proven system that eliminates cable artifact altogether.

Think of it this way. If you have two cables and one sounds better than the other, right away you have to be suspicious of both. Why? Next year, the manufacturer of the 'better' cable will have a new model that is more expensive yet, and sounds better- we have all seen this! How about a system where the cheapest cable sounds as good as the best cable? Wouldn't that be something of interest?

Finally THE TRUTH.

"The 99.99999% figure quoted for purity is outright preposterous"

Nordost uses 99.999999% pure copper.

"BTW this is why you don't see copper wire that is Teflon insulated."

I just look at my Satori speaker cables that are 6N copper in Teflon. You can get many Nordost cables that are 8N copper (silver plated) in Teflon insulation as well as Neotech hookup wire that are 7N continuous cast copper in teflon (no plating). Many Audioquest cables (like Colorado or Gibraltar) are 6N copper in Teflon.

I know about microphone standard but am unfamiliar with preamps designed to have 600ohm output impedance to drive 600ohm load.

"Actually if you work the math the opposite is true- with no current at all then the minor resistances, odd diode effects and the like will become more prominent."

I don't see why - where there is no current resistance is unimportant. 1ohm total (of all impurities) resistance with 40k load impedance divides voltage by 1/40001 but with 600ohm load it is 1/601 divider. If there is any diode effect then junction voltage increases with the current.

Kijanki... I have a nice bridge in Brooklyn. Would you be interested?