BALANCED v. UNBALANCED

Steve Williams said:

Nick base my cable based on my balanced switch circuitry coming off the heads. IOW it is a true balanced switch. He redid my switch based on the need for SE outputs. Lack of space beside the existing XLR outs. So I need a balanced pair of cables coming RCA out of my Studer and XLR into his tape head preamp. Hence the need for such a cable. I have since sent back a pair of my balanced Valhalla cables for R A on one side and XLR on the other. Works beautifully. Dead quiet.

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Steve,

Nick explained it all some posts ago :
http://www.whatsbestforum.com/showthread.php?10535-Doctor-s-Orders-Part-Two-The-New-Listening-Room-Of-Steve-Williams&p=202200&viewfull=1#post202200
I found it interesting because Keithley pico-ameters have done it since long using special BNC connectors.

Probably Nordost connected the two signal cables of the Valhalla cable to the RCA tip and ground and the cable shield only to pin 1 of the XLR.

Not sure how the connections are made but I even have a fully balanced Valhalla cable that is RCA on one end and XLR on the other

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This can be done but you run the risk of potential noise. Probably not suited for all systems.

I have built some custom preamps and amplifiers that use single ended RCA type connectors (BNC on my personal pieces) for balanced connection. However, the way I do it is as follows:
The center pin of one "RCA" is the "hot" the center pin of the 2nd RCA is the "neutral" while the ground of both are tied together and are used for the shield. I have found this provides better results than XLR connectors but I don't think the industry is ready to convert. I also prefer BNC connectors to RCA.

This method will be installed on some of my custom built preamps and amplifiers using BNC connectors (for another company I design for). There is also a way to switch this for use of single ended RCA connection as well as an XLR connector allowing users to use a standard balanced cable should they choose to.

Bill, that's a very legitimate way to make a balanced interconnect cable.

But the center pin of one "RCA" is the "plus" and the center pin of the 2nd RCA is the "minus" while the shells of both are tied together and are used for the shield. As there is no ground wire in a balanced interconnect.

You are correct speedskater but often the shield is connected to ground. Either directly or through an RC circuit. You can also float the shield. We use unique switching that connects pin 1 to ground and then connects pins 3 and 1 together so you can prevent potential noise when running single ended çonnections to some amplifiers. Of course this depends on what type of balanced circuit is used.

Some of you guys are beyond my paygrade on circuit design, but there are pieces of gear that used 'balanced' type connectors, i.e., an XLR, that are not balanced circuits, e.g. Lamm SET amplifiers.
I thought the XLR thing (and perhaps balanced outputs and inputs) was originally adapted from 'pro' applications to reduce noise and hum on long cable runs.
My phono stage outputs balanced to my linestage and I use XLR cable for that. The line stage outputs balanced and I run XLR terminated interconnects to my Lamm ML 2s, which have both RCA and XLR inputs, but it is not a balanced input or circuit.

Hello whart,
You are correct, some products oout there do have XLR connectors just for the sake of having them. They are simply a single ended connection using an XLR connector. I have had to do this for customers that didn't want to have to buy new cables and keep there balanced/XLR cables.

Unnfortunately, [some] of these companies (not many) don't even tell you that it is not a balanced circuit.

Balanced circuits were originally more opted for pro gear but due to its advantages, found its way into hifi as well.

pingu said:

I asked the manufacturer why not and he advised that balanced has the effect of canceling out even order distortion but leaving the odd order harmonics. More gain of course, but a thinner, less bloomy sound. This is, I am told, the result of electrical theory well beyond my pay grade. For that reason, he opted for single ended only.

Is there any consensus on this issue? Is balanced properly left to long microphone runs with single ended the right choice for home stereo?

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It does not matter the length of the cable- if true balanced the performance is always better than single-ended. It is true that internally balanced circuits will cancel out even ordered harmonic distortion, leaving the odds. However, the odds alway operate at a lower level then the evens, for example the 3rd (being the only odd order that has a musical sound to the human ear) is considerably lower level than the 2nd might have been were it still present, and its presence nevertheless masks the higher orders that are at even lower levels.

Even ordered harmonics (the 2nd in particular) will make for a more lush sound (warmth) but will also mask lower level detail. Its a good idea to get rid of it if you can.

Of course, this being high end audio, there is no consensus But if you want to understand how well balanced operation really works, you need look no further than your own recording collection. Any recording made in the 1950s or 1960s was done with balanced lines, long before any exotic interconnect cable industry existed, yet the better you get your stereo to perform the better these recordings (many of which are highly respected 50 years on) sound as well. You don't run into some sort of ceiling because you start hearing the defects in the cables used back then.

The whole point of the balanced line system was to eliminate cable artifact. Now you would think audiophiles would love to do just exactly that, but a surprising amount come up with some considerable push-back, but I suspect it is mostly because they don't understand how the balanced system works and the benefits that are thus derived. This is true of a lot of manufacturers too!

The benefits, if done right:
1) ZERO cable interaction, and you can run the cables almost any length. This allows you to place the amplifiers right by your speakers, and have your preamp somewhere else than right between the speakers, perhaps near your listening chair.

2) lower noise, blacker background, less likelihood of ground loops

3) inexpensive cables can be used with world-class results

If equipment is internally balanced the benefits are:

1) lower noise, up to 6db less per stage of gain

2) lower distortion, which does not compound from stage to stage within the circuit

3) greater immunity to power supply noise

Disadvantages

Balanced equipment *might* cost a little more. In high end audio, due to the Veblen effect, this tends to not play out in practice.

You may have noticed That I said 'done right' above. There is a balanced standard of sorts, a set of practices that should be followed if you are to realize all the benefits. Here is the standard:

1) pin 1 is ground, pins 2 and 3 are signal, pin 2 being 180 degrees out of phase with pin 3. In the US, pin 2 is non-inverting.
2) the ground connection is ignored. Neither the input of the preamp/amp uses it, nor the output- it is for shielding only, no signal current. This, BTW, is where most high end companies screw up; by putting ground current through the shield, cable immunity is lost.
3) the input that is being driven should be low impedance (600 ohms is the line level standard), failing that the source should be able to drive that load anyway. Again, most high end companies fail in this regard as well- there are a lot of tube balanced preamps that can't even drive 10K ohms, let alone 600 ohms. BTW, all magnetic/moving coil cartridges and all tape heads are balanced sources and are capable of driving some lower impedances that would choke most tube preamps! If some aspect of this low impedance issue is not utilized, cable immunity will be lost.
4) the balanced connection shall consist of a twisted pair of wires to carry the signal, which is shielded by a common shield. No dual-shielded wires (unless the second shield is concentric around the first), no weird ground boxes, so situations where the non-inverted signal is shielded by the inverted signal, etc.

As a footnote, differential and balanced are not the same thing. It is best when the two are found together. However it is possible for a circuit to be balanced and not differential (such circuits tend to have more noise and higher parts count) and it is also possible to have differential operation without balanced operation. In fact all single-ended amplifiers are examples of the latter, although the differential aspect is usually ignored by the designers of such circuits.

mep said:

There are lots of balanced products in the marketplace and I don't ever remember reading a review that contained measurements which indicated all even order harmonics had been canceled out and only odd order harmonics remained. Seems like this would really be an issue if true depending on the level of harmonics contained in the signal.

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mep, if you recall reading about almost any push-pull amplifier, you might recall reading that even ordered distortions are canceled in the output section, for example this happens in a Dynaco ST-70. The harmonics of the original signal however are left intact.

Excellent Post from Ralph at Atma-Sphere! As an EE I think that he sums up the true balanced (XLR) equipment and cable story completely.

Expensive "audiophile approved" XLR cables are a waste of money as Ralph explains. I use Canare Quad Star Pro XLR's with excellent results.

http://www.markertek.com/Cables/Audio-Cables/XLR-to-XLR-Cables/TecNec/SC100XXJ.xhtml

Just a brief note. The terms, Balanced and Differential are not synonymous. Balanced refers to an interface where the signal conductors have identical impedance values with respect to some common ground reference. Differential refers to a type of amplification or processing, where oppositely phased signals are eventually mathematically subtracted from each other. Single-ended drivers can also be connected via true balanced impedance interfaces. However, a differential receiver make the best use of a balanced signal interface.

Ken Newton said:

Just a brief note. The terms, Balanced and Differential are not synonymous. Balanced refers to an interface
where the signal conductors have identical impedance values with respect to some common ground reference. Differential refers to a type of amplification or processing, where oppositely phased signals are eventually mathematically subtracted from each other. Single-ended drivers can also be connected via true balanced impedance interfaces. However, a differential receiver make the best use of a balanced signal interface.

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Must be an echo in here.

Ken Newton said:

Just a brief note. The terms, Balanced and Differential are not synonymous. Balanced refers to an interface
where the signal conductors have identical impedance values with respect to some common ground reference. Differential refers to a type of amplification or processing, where oppositely phased signals are eventually mathematically subtracted from each other. Single-ended drivers can also be connected via true balanced impedance interfaces. However, a differential receiver make the best use of a balanced signal interface.

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Must be an echo in here. At least give Ralph some credit.

MylesBAstor said:

Must be an echo in here. At least give Ralph some credit.

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I simply hadn't noticed he had pointed out this distinction in one of his posts. There is no attempt to take Ralph's credit.

no worries!

FWIW it is possible to receive the signal differentially by almost any amplifier even though it is not balanced. We developed a technique for that based on a similar method used by George Philbrick of Op-Amp fame, 'way back in the late 1940s.

The positives of balanced have been well addressed such as by Atmosphere Audio, but often the negatives are just commonly stated as being added complexity and not worth the extra cost in a business sense.

But one factor not mentioned and often avoided is phase distortion.

Imagine a fully balanced system, DAC to pre-amp to power amplifier. From the DAC onwards each half of the sine wave is fully isolated and has its own amplification channel. When both halves of the signal are finally combined at the amplifiers output stage for driving the speakers, does anyone here seriously think that there is going to be a consistent match between those two signals?

After passing through 3 boxes of electronics and 2 sets of cables? With all those resistors and capacitors that have slightly different tolerance values?
Unless we are talking about some 200k, Japanese, obsessively hand matched components, I would say no. Now the question is, do the benefits of balanced outweigh the negatives of increased phase distortion?

Probably it does. I just think its disingenuous for some people to claim that the only negative of balanced is added part count cost.

There is also the argument that the balanced signal will be passing through many more, possibly twice the number of components as a single ended circuit (depending on comparative circuit topology). There is that old truth in high end audio, the more parts the signal runs through, the worse the sound usually gets.

agisthos said:

The positives of balanced have been well addressed such as by Atmosphere Audio, but often the negatives are just commonly stated as being added complexity and not worth the extra cost in a business sense.

But one factor not mentioned and often avoided is phase distortion.

Imagine a fully balanced system, DAC to pre-amp to power amplifier. From the DAC onwards each half of the sine wave is fully isolated and has its own amplification channel. When both halves of the signal are finally combined at the amplifiers output stage for driving the speakers, does anyone here seriously think that there is going to be a consistent match between those two signals?

After passing through 3 boxes of electronics and 2 sets of cables? With all those resistors and capacitors that have slightly different tolerance values?
Unless we are talking about some 200k, Japanese, obsessively hand matched components, I would say no. Now the question is, do the benefits of balanced outweigh the negatives of increased phase distortion?

Probably it does. I just think its disingenuous for some people to claim that the only negative of balanced is added part count cost.

There is also the argument that the balanced signal will be passing through many more, possibly twice the number of components as a single ended circuit (depending on comparative circuit topology). There is that old truth in high end audio, the more parts the signal runs through, the worse the sound usually gets.

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^^ The problem with your argument is that it usually does not work the way you describe at all, as long as there are differential circuits somewhere downstream from the source.

In particular, the scenario highlighted in bold does not seem to exist in the real world: the 'fully isolated and has its own amplification channel' part.

A differential circuit will have two outputs, one inverted and the other non-inverted. Unlike a merely symmetrical circuit though, a differential amplifier will create both phases, even if the input signal is single ended. So "When both halves of the signal are finally combined", this happens at each stage of gain in the signal path, from phono input, output, line stage input and output, and also at the input and output of the voltage amplifier in the power amp.

Now we have a balanced phono section in our preamps that is fully differential. It works with low output moving coil cartridges, but has only two stages of gain. Most single-ended LOMC phono sections have three. So the question is, is two stages of gain more complex or is three stages of gain? The reason we can get by with two stages of gain is that differential circuits (in theory) have 6 db less noise than their single-ended counterparts.

In short, the argument that you have more signal path complexity with a balanced circuit is usually not true. In our case, there is signal path simplicity compared to a lot of single-ended circuits.

There are different topologies and ways to skin a cat, I did not mean to imply anything about your own products.

But what is your opinion on the general fact of balanced amplification, that each half of the signal is being split into two, and that component tolerance values will never be perfect, and cause phase distortion when recombining?

In your phono stage, you only pass through 2 gain stages compared to 3 for a similar SE section. But it's each half of the signal (inverted/non) that is passing through 2 separate gain stages. So doesn't this mean the signal passes through 4 stages ultimately? How is this more simple than 3 gain stages.

I have never heard Atmasphere products but I want to!!

I don't know of a product that has independent signal paths for each phase. Maybe there is one out there. Seems like it would not perform very well.

In your phono stage, you only pass through 2 gain stages compared to 3 for a similar SE section. But it's each half of the signal (inverted/non) that is passing through 2 separate gain stages. So doesn't this mean the signal passes through 4 stages ultimately? How is this more simple than 3 gain stages.

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I have the feeling that there is a fundamental misunderstanding of how differential circuits work here. A differential circuit, executed with two devices (tube or transistor) is really only a single gain stage even though two devices are involved. The input can be applied to either input and the circuit will have the desired result. Or the signal can be applied to *both* inputs. In any case, the outputs will be amplified versions of the input, one inverted and the other non-inverted. The key to this is that the cathodes (or emitters) are coupled together with a common cathode (or emitter) resistor. When one side of the circuit is asked to conduct hard, the other side is forced to conduct less and vice versa. In this way, the two halves are intimately coupled in such a way that its nearly impossible for one side to do something without the other side doing the exact opposite.

IOW, I think confusion is created when the idea of 'half of the signal' gets bandied about as a concept- it really does not work like that. The one 'half' cannot exist without the other; each is in fact a complete whole signal on its own.

I use my Dynavector amps in balanced mode. Better sound all round than unbalanced IMO.

Hi for AR Ref 3, is balanced usually better than Unbalanced? Also, if I put in a Single ended in, balanced out, will I get a drop in SQ? I have to have a balanced out because my power amp, the Ref 110, is balanced only.