At what distance are balanced XLR cables needed?


I've been looking for a new preamp for my 2 channel system, and I'm debating whether I need balanced inputs if I want to eventually connect it to my home theater processor. I plan on moving soon, so I can't say for sure what distance I would have between the two systems. My preamp options quickly dwindle if I require XLR cables.
hoffer71
No answer is possible without knowing (1) the output current abilities of your preamp and (2) how much EMI noise there is.

Kal
If the HT Processor output impedance is about 50 ohms or less (typical for solid state) 20 feet should work fine.
Hope this helps:

My HT processor is an Anthem D2V. According to its specs, its input impedance is 20 kΩ, and its output impedance for "main" is 300Ω (RCA), 600 Ω (XLR), and for "zone 2" is 51Ω.

Impossible for me to determine EMI, but I plan on moving to an apartment in Manhattan.
I run 10meter interconnects, balanced and unbalanced, in Manhattan and have no noise problems with either. FWIW.

Kal
Thanks Kal. When discussing the output current, I'm assuming you meant my HT's output. If my apartment is relatively noise free, any concerns with running about 20 feet unbalanced given the d2v's impedance?
Kal, 10 meter unbalanced and no problems? How did you manage that? Unbalanced runs tend to act like an antenna in my experience, I had to resort to long runs of balanced interconnect to mitigate the attenuation.
There are no guarantees. I have heard of people resorting to balanced cables for much shorter lengths because their situations involve lots of EMI. (Do you live near a radio/TV transmitter?) Recording/mastering studios have miles of cables all influencing each other.

So, my cables are no less antennas than anyone else's but, as far as I can tell, they are not picking up any signals inside my apartment. Literally, YMMV.

Kal
If Zone 2 is really 51 ohms you could use that output. 300 ohms is a bit high for solid state but it will probably be OK.

Bear in mind that you can spend an arm and a leg for unbalanced interconnects made with exotic wire. Balanced interconnects don't need exotic wire, and might cost you less.
Eldartford - you can spend arm and a leg for a balanced IC as well. They're also made of fancy materials - both metals and insulation. There is no reason why it should be different IMHO. Purity of metal still applies since impurity reside between crystals while insulation material directly affects capacitance and dielectric absorption.
The superior connectiviity of a balanced connection makes it an easy choice--if you have that option. And while Kinjanki makes a valid point, reasonably priced XLR cables are widely available. A well-known manufacturer touts Belden cables with decent connectors for his very pricey gear. If it's good enough for him... Kal's comments are certainly valid also. Try borrowing cables from the Cable Co. The only downside is that they probably have limited choices in the lengths discussed. Blue Jeans Cables might be a good, low-cost option for you. Just my $.02 Good luck!
Kijanki.. And you can pay an arm and a leg for little stones.
Atmasphere, whose opinion carries a lot of weight, has suggested that fancy wire is of little value in balanced interconnects.
I ran a 30-feet Purist Dominus RCA-RCA IC from Aesthetix Callisto Sig line stage to CAT JL-3 amps for a few years and had no problems with noise, radio station pickup, etc. My experience with this one setup nullified many of the theories regularly reported here. You won't know if it a cable works for you unless you try it out yourself.

Atmasphere, whose opinion carries a lot of weight, has suggested that fancy wire is of little value in balanced interconnects.
I value the contributions made here regularly by Atmasphere. But my experiences about balanced and single-ended cable differences significantly differ than his reports here. Once again, don't get too attached to the blanket statements often made here, but rather try many cables for yourself.
Jafox... I also ran long single ended interconnects for many years without problems. And they weren't any exotic wire. I changed over to balanced interconnects simply because I bought some new equipment having this interface.

I trust Atmasphere on this subject not only because he is usually well informed but also because he once provided a good writeup on the subject of balanced interconnects. Maybe he will come by and do it again.
Atmasphere, whose opinion carries a lot of weight, has suggested that fancy wire is of little value in balanced interconnects.

There is a little more to that statement than meets the eye. For example, Ralph indicates that the balanced cable used between his preamps and amps need not be anything more than Mogami cable. The reason being his designs support the 600 ohm standard, something used in pro audio, and thereby controls the interconnect and makes the capacitive, inductive, resistive and other aspects of the cable negligible. Not all components are designed to this standard.

To further clarify, according to Ralph who posted this in another thread I'm a participant in, a low output impedance will mean that the preamp can drive a load of less than 1000 ohms without loss of bandwidth, voltage or increase in distortion. IOW if you can hear differences in the cable between the line section and the power amp, then the cable is not being controlled.
I was about to compose a post saying essentially the same things as in Clio's post above, but he saved me the trouble :-)

Ralph has particularly emphasized the part about "not all components are designed to this standard," meaning that it is common for balanced interfaces to have inadequately low output impedance, or to be otherwise poorly designed. That would seem likely to be the major reason for differences being reported between balanced cables.
Kijanki 1-19-11: You can spend arm and a leg for a balanced IC as well. They're also made of fancy materials - both metals and insulation. There is no reason why it should be different IMHO. Purity of metal still applies since impurity reside between crystals while insulation material directly affects capacitance and dielectric absorption.
This assumes that differences in impurities between crystals and differences in dielectric absorption are sonically significant, neither assumption having been proven based on widely recognized science, as far as I am aware. Although neither assumption has been disproven either, as far as I am aware.

Low capacitance, of course, is easily obtainable in low priced as well as high priced cables, and is only significant if output impedance is high and run length is long.

Regards,
-- Al
Al - I'm not sure if metal purity or dielectric absorption or capacitance play role in any particular setup either, but if they do - I can't see any reason why it would be different for balanced vs unbalanced cable.

Balanced versions are always slightly more expensive. If noise is the only concern balanced cable can be more effective for less money. Shield on single ended cable protects from capacitive coupling and high frequency EMI, but might be less then perfect in lower range of the radio frequencies where it works still as an antenna (poor one) while skin effect (that causes induced EMI to run on the outside - shield)is not strong yet. Balanced configuration suppresses common mode signals in this range of frequencies, while twisted conductors provide further noise rejection (cancellation thru even exposure).
IME, more than 15ft.
Anything over 3 meters, but I would still keep the interconnects as short as possible
Kijanki -- I agree 100% with your post just above.

I would additionally mention the fact that balanced interfaces will be much less susceptible to ground loop issues than unbalanced interfaces. That susceptibility can be length-dependent, because it is sensitive to the resistance of the inter-chassis connection path. But the length-dependency will be system-dependent and unpredictable.

Best regards,
-- Al
Mariv26: Anything over 3 meters, but I would still keep the interconnects as short as possible
I don't think you can make such a general recommendation. It really depends on the EMI environment. OTOH, if you believe that there are no potential disadvantages, only potential advantages, to balanced interconnects, you might want to use them regardless of length.

Kal

Kal, Absolutely. Why not to use balanced if environment is known to be noisy. My Rowland 102, a class D amp, has only balanced input connector - a mature decision on a side of Jeff Rowland. Balanced has also two practical advantages - it won't disconnect (latch) and prevents touching input (exposed side always female with recessed sockets). The only disadvantage I know of is a little higher price.
IOW if you can hear differences in the cable between the line section and the power amp, then the cable is not being controlled.
Hmmmm, now there's a pretty serious generalization. I have heard significant differences between IC's in the critical line-stage to amp link with Audio Research, CAT, BAT, Aesthetix, Aria/Counterpoint, to name a few products. Are you claiming that the designers of these products are not competent to "control" the cable?

Mariv26: Anything over 3 meters, but I would still keep the interconnects as short as possible

I don't think you can make such a general recommendation

Agreed, as my own experience voids such a generalization.
I have heard significant differences between IC's in the critical line-stage to amp link with Audio Research, CAT, BAT, Aesthetix, Aria/Counterpoint, to name a few products. Are you claiming that the designers of these products are not competent to "control" the cable?

Actually I was restating something Ralph Karsten restated in this thread:

http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1276356977&openflup&531&4#531

It is 8 paragraphs into the response if you include the numbered paragraphs.

Personally, I think Ralph has been on to something for a while. There is some credence to supporting the 600 ohm standard in balanced designs. Not many manufacturers do. This does not make them incompetent, but it does allow the cable to exert an influence on the signal. As for single ended designs the ability to design components to control the cable is more difficult. As Ralph states in the first sentence of this response to me in another thread:

http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1276356977&openflup&537&4#537

Driving a load of less than 1000 ohms is not an easy task. So it makes sense that in single ended designs you could more easily hear differences in cables.

FWIW, I hear very little difference in cables in my system these days. I've sold off all my Stealth and other uber expensive cables and am running very modestly priced cables in my system. There's not much I'm missing IMO. Allowed me to to put more money in my components as well.
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
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.
I would suspect that bigger current would cause bigger voltage drops on said junctions (or impurities) everything else being equal.

600ohm must be not very common since I've never seen anything that can drive 600ohm without distortion. For now I will stay with my Acoustic Zen Absolute XLR (7N silver, 0.02uH/ft, 6pF/ft). Acoustic Zen as well as Audioquest and many others must believe that metal makes a difference since they use 99.99999% pure copper and silver.
Kijanki... 600 ohms is the output impedance of the preamp. You don't have to drive 600 ohms.

200K is the input impedance of Atmasphere power amps.
Acoustic Zen as well as Audioquest and many others must believe that metal makes a difference since they use 99.99999% pure copper and silver.
It makes a difference in what they can charge for the product, that much appears to be true.
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?
Atmasphere... Question... 600 ohms is a practical low output impedance for tube circuits. (Some are 1000 ohms or more). But solid state circuits can be much lower eg: 50 ohms is common. Is the 600 ohm value a maximum?
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.

Atmasphere... So the 100 ohm output, balanced, from my Behringer DEQ2496 is OK. Whew!!

Your preamps are no doubt better than the average tube gear. 600 ohms is what I always saw with the mid fi stuff I used.
Output impedance is not that important within certain limits. My Benchmark DAC1 has output impedance values from 60 to 1600ohm dependent on output divider jumper position. Benchmark recommends for 1600ohm output maximum cable length of 26ft - assuming typical 32pF/ft and 0.1dB drop at 20kHz. With my cable (6pF/ft) I could go 139ft.
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.
I have a McIntosh C2300 preamp feeding a McIntosh MC402. They are 16 feet apart. I have used both Balanced XLR connections and RCA single ended connections. The balanced has sounded better every time. By the way the RCA Single ended cables were supposed to be more highly regarded and definitely way more expensive.

So, to answer your question, I found 16 feet the distance in my system.

I would suggest using the very best cable and connectors available, and if that means using XLR's, by all means use them.
Atmasphere, unfortunately I don't like gain at 60ohm position. Not many solid state amps have 60ohm output impedance while the most of them cannot drive 600ohm. The reason for that are op-amps used. Only few like LM4562 or OPA1611/12 are designed specifically for that. In addition most of preamps have output capacitor not designed for 600ohm load. I used to solder resistors left and right when I was young. Now I know better and do always whatever is "standard".
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!