At what distance are balanced XLR cables needed?

Kijanki, you and I are on the same page in that regard. It does you no good to drive 600 ohms if the circuit doing it sounds worse!

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.

Kijanki, yes, I think I can. The purity of metal has a lot to do with 'diode effects' in the material. The idea is that strands of wire do not conduct completely linearly- they are affected by diode junctions that exist between them.

However these diode junctions are not very profound or robust. They would only be detectable (if you will pardon the pun) if you had very low currents in the cable.

Well my friends, this will be the case with most single-ended connections, and for that matter any connection of high impedance.

OTOH, if we are using a balanced system *that conforms to the balanced standard* then there *will* be significant currents, and any primitive diode junctions will be of no account.

Now I should point something out. If anyone tells you that they have more than 99.99% purity of metals in the wire, they are likely pulling your leg. Oxidation makes it virtually impossible to exceed this figure!

Additionally, OFC (99.99% pure copper) was *not* developed for audiophiles, it was developed for alternators and generators because it is more flexible. However, a few weeks after extrusion into the insulation, there will have been enough oxygen contamination of OFC so that, other than flexibility, it will have about the same characteristics and purity as regular ETP copper.

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?

Eldartford, FWIW our preamp has an output impedance much lower than 600 ohms. A lot of tube preamps do as well. The trick is: what is their output impedance at 20 Hz or 5Hz. With most tube preamps the output impedance at these frequencies will be much higher than stated. Its another way of saying that if you have a 600 ohm load, these preamps will no longer play bass right.

The 600 ohm value comes from the fact that spaced conductors reach a maximum characteristic impedance of 600 ohms in free air. The reason this was adopted is due to the phone companies: before balanced line existed, there was no such thing as true long distance calling! Transcontinental and intercontinental calls became possible due to the increased resolution of balanced operation.

Even if the cable is only a meter long this increase in resolution is audible.

So the 600 ohm value is a practical maximum. Microphone often run much lower- my Neumann U67s run at 150 ohms.

These days any professional or semi-pro audio gear for music or recording has to support this standard. It is only in high end audio where there is still mystery surrounding this subject. And, not surprisingly, it is something that cable manufacturers, for the most part, would rather you not know. I see their business as safe, however, since there are still single-ended cables to be made, as well as speaker and power cables. And as long as the high end industry remains ignorant regarding the standard, there will be a market for 'exotic' balanced cables too.

Kijanki, with the 1600 ohm parameter selected, it assumes a high impedance at the other end as there would be distortion if it were actually driving a load of a lower impedance.

You will hear big differences in cables with it set up this way.

As a general rule of thumb, the output impedance should be about 1/10th of whatever it is driving. So the 60 ohm position *should* be able to drive a 600 ohm load just fine. And FWIW, many solid state preamps can do that. Its the tube units where this is a challenge.

So if you set the unit to 60 ohms and then place a 600 ohm resistor between pins 2 and 3 at the input of the amplifier, the result is that you will not be able to hear differences between interconnects, regardless of cost.