As it stands in today’s times, some type of wire is necessary to connect components and speakers in a high performance audio system. Unlike lower fidelity audio, wireless technology has not yet progressed to the point of any measure of the superior sound audiophile’s demand. For anyone new to the hobby, I thought it might be informative to look at the principal differences between balanced, or XLR, and single ended, or RCA cables in more detail. Please note, however, this is a cursory look – audio cables are far more technical than discussed in this article.
When we use the term “cable,” we are using a catch all phrase. Any piece of wire in an audio system could be called a cable. However, the term cable principally refers to something transferring the signal from a power amp to a speaker.
The term “interconnect” is used for components connected to each other – like a music server or streaming device to a DAC, or a DAC to a preamp or amp. This article will briefly examine interconnects more closely.
Generally speaking, the goal of any piece of wire in an audio system is to transmit a signal from one place to another with no change to that signal in any way. In other words, the cable or interconnect should come as closely as possible to doing absolutely nothing to what passes through. It doesn’t always work that way, however. Physics, and electronic circuitry tend to get in the way.
There are any number of types of insulation available. Actual design depends on the application. As such, insulation used on a lamp cord will very likely be quite different than what is used for high performance equipment. Air is widely considered the best insulator, or dielectric, but is also the hardest to utilize. Hence, many insulation materials are some type of plastic or rubber compound. Insulation alone, however, is only the beginning.
One unchangeable characteristic is wire tends to act as an antenna, therefore picking up unwanted signals from the air. Longer lengths act more as antennas than shorter lengths. The dielectric may or may not adequately filter out unwanted externally borne signals.
These signals, be they TV, Radio, Wi-Fi, Bluetooth, Cell Phone, you name it – any and all may potentially be picked up by that piece of wire and ultimately passed through the system as distortion. It is these signals and subsequent distortion we want to eliminate.
Balanced or unbalanced, in addition to describing a type of interconnect, also refers to a circuit. Because if a balanced interconnect is being used, a balanced circuit within the component must also be used to ensure distortion is removed to the highest degree possible. Just because a component has a balanced connection, typically called an XLR connector, does not mean the component is balanced. It needs to be “balanced” from the input to the output. Somewhere in the component’s literature you should find terms like “fully balanced,” or “balanced from back to front.”
In most cases, a single component possessing separate circuits for the left and right channels are called dual mono, or two (basically identical) mono components in one enclosure. Dual mono components are also, most commonly, a balanced design. Fully mono components, like monoblock amplifiers, have one enclosure for the left channel and a separate enclosure for the right.
Bottom line, the component must be balanced or using a balanced interconnect will not make a lot of difference. Sadly, some components have XLR connections even though they do not have balanced circuitry. Be wary of a very inexpensive component with an XLR connection on the back. Check to be sure the component is actually fully balanced.
Common Mode Rejection. This is pretty much the crux of the discussion of XLR (balanced) vs RCA (unbalanced). Common Mode Rejection is the ability to eliminate externally created distortion from a circuit that will otherwise be passed through to the speakers.
More specifically, three wire, or XLR interconnects have a hot, neutral and ground. Actually, the technically correct terminology is “hot,” “cold” and a ground. Use whichever is easiest to understand and remember. RCA has one wire to carry current and a ground wire to complete the circuit. Actual music signals carried by XLR will have the polarity of the hot wire opposite to that of the neutral, or cold. Those signals are allowed to pass. Specifically, they are 180 degrees opposite in phase.
Distortion that enters the interconnect from the outside, because remember, all wire acts as an antenna, is removed because the signal is in the same phase on both the hot and cold in an XLR connection. Because of Common Mode Rejection, any signal, or part of a signal that is common, or in phase with both current carrying conductors is removed. As such, distortion is reduced.
Because an RCA connection only has one wire to carry current and a ground, any signal the interconnect picks up from the outside will easily pass through to the component, through the system and to the speakers manifesting as distortion.
Oddly enough, and very often the case in high performance audio, using RCA connections does not always mean an inferior to XLR sonic quality. There are certainly instances where system owners will actually prefer the sound of an unbalanced circuit. Like absolutely everything in our hobby, the ultimate preference lies in the ears of the listener.
What cannot be denied, however, is with a proper balanced circuit in the signal chain, XLR will remove, or not allow externally borne distortion to pass. This, therefore, lowers the signal to noise ratio (or how much noise a music signal contains – less noise means better sound) and delivers an overall improved listening experience.
Also, like in many other areas of an audio system, a widespread and comprehensive usage of a technology is recommended. It is a wise choice to not permanently mix unbalanced and balanced components and interconnects. It is also generally the case that systems more on the budget side of the price spectrum will be unbalanced. More expensive systems will be balanced. Despite balanced cables typically costing more than RCA, the safest choice for superior sonics will be an XLR connection connected to balanced components.
Most seasoned audiophiles are aware of these differences. However, for anyone who may be unsure why XLR interconnects are used in preference to RCA, this article will hopefully help provide increased understanding.