November 2023

A Simple Guide To Balanced XLR
Versus Unbalanced RCA Audio Signal Flow
Let's finally bring it all together in an understandable form.
Article By Roger Skoff

  Recent conversations with audiophiles and music lovers have brought me to the surprising realization that, although they may have excellent systems and even a fair working knowledge of how to put them together, set them up, use them, and keep them running, a good many audiophiles have little idea of how they work.

It's sort of like driving a car: Any licensed driver can do it – some even with great skill – but how many drivers know how an internal combustion engine or automatic (let alone manual gearshift) transmission works?

Here's a starter about audio. If you like it, let me know. More may follow.

With audio, it all starts with the electron. And that, just in itself can be a major source of confusion. Electrons are part of the structure of every atom and, although atoms and the molecules they form can be very different, all of the electrons that are part of their composition are identical, interchangeable, and can easily move from one atom to another. When that happens in quantity and in response to a stimulus, it's called current flow and is the basis for all electrical and electronic activity.

Where it can get confusing is that electrons are charged particles and all of them have a negative charge. However, when an atom or an object made of atoms (meaning any object at all) has exactly the number of electrons it's supposed to have, it's not said to be charged, but to be at (electron) balance or to have no charge at all.

Confused yet? No? Good, let's keep going.

When we say that an object – a wire, or any other conductor – is "charged" we're never referring to the charge of the electron, itself, but to the number of electrons present as compared to the number it's supposed to have. If there's a surplus of electrons – more electrons than necessary – because each electron has a negative charge, we say that the object,  having too many negative elements, has a negative charge. If there are fewer electrons than there should be, however, because the object is lacking in electrons (not sufficiently negative) we say that the charge is positive.

So, in physics and usually in the electronics industry, "too much" means negative, and "not enough" means positive – exactly the opposite of what common sense would dictate. To make it worse, though, in the electrical industry (not electronics, but things like house wiring) the opposite approach is taken. To an electrician (but not to an audio designer), if a wire has a surplus of electrons it's "hot", "live", or "positive", and if it doesn't have enough, it's negative. 

The point of it is that it's always a matter of electron count and, ultimately, the electron count is always going to try to get to electron balance – exactly the number of electrons that are supposed to be there; neither more (we'll use electronics lingo here, and say that that would be a state of negative charge) nor less (what, in audio, we would call a positive charge) but just exactly the number there's supposed to be. In either case, when a charge is detected, it can only be either negative or positive, and whichever one it is is what we call the charge's polarity.

There's still another potentially confusing factor: "Static" electricity.

Unlike what happens with electrical conductors, where, if electrons can flow they will flow, and the system will eventually revert to electron balance, static electricity is a condition of NON-conductors where an electron imbalance occurs and simply stays on the surface of the non-conducting material until something (your finger touching it, for example) happens and it's suddenly released to the ground (anything with an appropriately opposite lack or surplus of electrons which the static charge can help to return to electron balance).

That's really all that any current flow is – a flow of electrons from a too-high electron count area to a too-low electron count area, with the purpose always being to restore (to the extent possible) the electron balance of the two areas.

That being the case, and because an audio signal is, at the base, just a particular kind of current, let's take a look at audio signals and the two most commonly used systems for transporting them. In doing so, we're only going to look at wired systems. "Wireless" signal transmission is certainly possible (consider radio and television), but because some amount of wired transmission must always follow the wireless signal, it's just an extra step in the process and doesn't need to be discussed here.

Before we do that, though, let's take a look at, other than a surplus or shortage of electrons, the one thing most essential to current flow: the existence of a complete and unbroken circuit.

At its simplest, a circuit is nothing more than a system (a "loop|) for maintaining electron balance. Think of electrical current flow as analogous in some ways to the flow of water. Just as water in a closed system, will always "seek its own level" (meaning that all of the water in a number of connected vessels will always seek for the level of water in every vessel to be the same as that of every other vessel), so will the electron "level" at every point in a circuit seek to be at or as close to its electron balance point as possible.

Just as water in a vessel with too much in it will flow to another vessel in the system that has too little until the level of all of the water in all of the vessels in the system is the same, so will electrons flow from a (see, here it comes again) negatively charged area (too many electrons) to one with a positive charge (too few electrons). And, if we create a shortage in one area (a positive charge) by taking electrons away from it, available electrons will flow, if the circuit is complete, into it from another source until, to the degree possible, both are at their point of electron balance.

That's "if the circuit is complete..." If it's not, there will be no current flow, and the three ways that that can happen are:

1) An "open" circuit. That's any break in the circuit thar doesn't allow the electrons a path to complete their flow.

2) A switch. That's any means for purposefully creating an open circuit to stop current flow or to allow it by closing the switch and allowing current flow to happen.

3) A lack of "grounding". A "ground (or "earth") is the final element of any circuit.

Early electrical experimenters created the term in emulation of the process whereby the massive charges of electricity that constitute a lightning bolt are allowed to dissipate into the ground by striking a tree or other tall object connected to or projecting from the earth. Now it refers to any final contact or connection that completes an electron flow loop and allows a circuit to neutralize to electron balance.

The need to complete a circuit is why an electrical or electronic cable must always have (at least) two wires and the things it connects to must each have at least two terminals or contact points: Purposely simplifying things to allow for ease of explanation, one wire is to carry a charge from the source component to the receiving component (or, if it's an AC power cord, from the wall to whatever device will use it), which will then result in that component having an electron imbalance, and the other wire is so that the source component, now short of electrons can get electrons equal in number to the ones it lost back from the receiving component, thus restoring electron balance in both places. The two wires constitute all that's necessary – both source and ground – to create a circuit and support current flow, either AC or DC.

And that, finally, gets us to talking about audio and music.

Unlike the constant polarity DC (Direct Current) current flow that comes from a battery or that is created internally by our audio electronics to power their operation, all music signals are Alternating Current (AC), and constantly change polarity. In fact, it's the varying intensity (amplitude or "volume") and rate (frequency) of polarity change that is what our speakers convert to the changes in positive or negative air pressure that we hear as the music coming from our system.

Perhaps interestingly, "positive" and "negative" as used here are, unlike for electron polarity, just what we would expect them to be: "Positive" meaning more pressure and "negative" meaning less. [Perhaps interestingly, "positive" and "negative" as used here are, unlike for electron polarity, just what we would expect them to be: "Positive" meaning more pressure and "negative" meaning less.

In order to communicate those changes from their point of origin (the signal from a phono cartridge, tuner, streamer, digital device, or whatever else) through the rest of our electronics and eventually out to our speakers, we typically use cables employing one of two very different operating systems: "unbalanced" (often called "single-ended") or "balanced" (also known as "differential").

In an unbalanced line, the signal (a single string of alternating positive and negative charges) [Or charges of a single polarity varying in intensity to a degree and at a rate that corresponds to the varying pressure levels falling on the original recording microphone(s). Think of a complex oscilloscope trace containing multiple frequencies. (In short, a typical musical passage) Although it includes many component signals that may all be alternating in polarity, it, at any given instant may, as the algebraic total of all of its elements, all be varying above (positive) or below Perhaps interestingly, "positive" and "negative" as used here are, unlike for electron polarity, just what we would expect them to be: "Positive" meaning more pressure and "negative" meaning less… or charges (negative) the zero line and, for that time, be of a single polarity passes from the source through the load and back to ground to complete the circuit. As an example, think of AC current coming out of the wall, passing through a light bulb, and going back to the wall (ground). With an unbalanced line there's a "live" or "hot" lead or terminal and a "ground" lead or terminal. It's simple, easy to build or use, and can work very well.

Or charges of a single polarity varying in intensity to a degree and at a rate that corresponds to the varying pressure levels falling on the original recording microphone(s). Think of a complex oscilloscope trace containing multiple frequencies. (In short, a typical musical passage) Although it includes many component signals that may all be alternating in polarity, it, at any given instant may, as the algebraic total of all of its elements, all be varying above (positive) or below Perhaps interestingly, "positive" and "negative" as used here are, unlike for electron polarity, just what we would expect them to be: "Positive" meaning more pressure and "negative" meaning less… or charges (negative) the zero line and, for that time, be of a single polarity.

A balanced line, however, can do it better.

In a balanced line, there is neither a "live" nor a ground lead or terminal. Instead, three wires are typically [But not always. It is possible to have a balanced line using only two wires and no shield. A balanced speaker cable, for example] used, commonly called "hot", "cold", and "shield" (non-signal bearing, but just there to provide shielding against external or internally generated noise and interference), and two signals are carried, both identical in every way except that they are of exactly opposite polarity. The result is that, in a balanced line, no ground lead is necessary. Both of the two leads or terminals, because the two signals are of opposite polarity, are always out of phase with each other and, therefore, can and does act as a ground for the other, each always having exactly the surplus or shortage of electrons necessary to bring the other to electron balance.

Because of this "self-grounding" effect, the balanced line is said to "float above ground", and needs no chassis or other grounding to function. That means that, if the cable is shielded (the third lead) the shield can be chassis grounded to provide separate shield grounding from the return leg of the cable (as it would be in an unbalanced system) and the overall signal-to-noise ratio may be improved. (How loud the signal is as compared to the level of background noise.)

With balanced or differential circuits, because there are two lines of charge, there is twice as much signal voltage available and twice as much current. That means, because 3dB of output is gained every time you double either the voltage or the current (the amperage) of a signal, and balanced operation doubles both, that a total gain of 6dB in output is achieved by balanced operation as compared with single-ended, and that also means an automatic 6dB of gain in signal-to-noise ratio.

Another benefit of balanced operation is "common mode rejection". This, despite the fancy title, is easy to understand. Because both of the two out-of-phase balanced signals are carried by two leads of the same cable, both, whether the cable is shielded or not, will be exposed to the same noise and externally generated distortion. That means that both will be distorted or pick up the noise of the same kind and degree, and when the two signals are combined, the noise and distortion will be completely canceled out and only the pure signal will remain.

Good stuff!

One further thing that you may find interesting is that most audiophile phono cartridges are naturally balanced-output devices, with the two output terminals for each channel  (normally mistakenly described as positive and negative) really out of phase with each other at all times.

Now that you know all there is about signal flow, go listen to your system and...

Enjoy the music!