Balanced Headphones Guide
You may have heard many people talking about running their headphones or IEMs in a “balanced” configuration instead of “single-ended,” or running headphone amplifiers or DACs in similar configurations.
But what is a “balanced” amp, DAC, cable, or headphone?
What do “balanced” and “single-ended” even mean?
Single Ended
Single-ended transmission is the more common method of audio signal transmission in headphones. In single-ended connections, both left and right have 2 wires each: one wire for transmitting the signal voltage and one ground wire.
Benefits of a single-ended connection are pretty much down to cost, convenience, and ubiquity. Most audio connections, whether it be the output jack of a laptop or computer motherboard, or the AUX cable you find in most cars are single-ended. Because they’ve been the norm for so long, they’re both less expensive to produce and buy as well as easier to find for ones intended use-case.
The downsides of single-ended connections mostly have to do with noise rejection… or lack thereof. Which brings us to “balanced” connections.
Balanced
Balanced transmission is designed to minimize noise and interference, making it a popular choice for high-end audio, where consumers are always trying to optimize their setup.
In balanced connections, the audio signal is transmitted through the positive and negative wires simultaneously, but with opposite polarity. The positive wire carries the signal with positive polarity, and vice versa.
How do “single-ended” and “balanced” cables differ?
A single-ended cable usually uses a total of 3 leads to provide the signal to the headphone driver. Looking at the 6.3mm (¼”) TRS cable as an example, there are 3 leads attached to the tip, ring, and sleeve of the cable. The black circles are actually insulation to separate the three gold sections that form the conductive parts of the cable. The “tip” is the triangular segment at the end of the cable, the “ring” is the middle segment between the two black rings, and the part closest to the connector housing is the “sleeve.”
Inside the cable are multiple smaller wires that handle different parts of the signal outputted by the amplifier. In a single-ended headphone chain using a 6.3mm TRS cable:
- The “tip” connects to a wire that goes to the positive (+) lead of the left headphone driver coil.
- The “ring” connects to a wire that goes to the positive (+) lead of the right driver.
- The “sleeve” (bolded) usually receives its lead from a solder joint in the “Y” split of the cable (or in the earpiece itself) where ground wire leading from the amplifier end’s plug splits into separate wires that are connected to the negative terminals of each driver coils.
So both drivers actually share a common negative connection + ground in a single-ended system. Is this inherently inferior for sound quality? Absolutely not, many single-ended systems can sound great! But there are legitimate reasons to desire a balanced system that, while they may not positively affect sound quality, can serve to inoculate the system from spurious noises.
In a balanced cable, there are instead 4 leads—one positive per channel (two total) and one negative per channel (two total).
In a chain with a balanced cable between amplifier and headphone, the normal three-conductor cable with the common ground connection plug is replaced with a cable that has four conductors: right positive and right negative conductors to the positive and negative connections of the right driver coil; and left positive and left negative conductors to the left driver coil.
Okay, but how does this reject noise?
Balanced connections are more resistant to noise because any interference picked up by the signal wires is typically canceled out. This is because the interference will affect both the positive and negative wires equally, which means when the signals are recombined at the end of the cable run (which functionally reverses the polarity of the negative wire upon arrival) the “common-mode” noise or interference—the noise picked up equally by both wires as they travel between devices—between the two wires is eliminated.
We can frame this as a group of equations, but first we need to determine our variables.
The positive wire: Audio Signal + Noise (picked up along the cable)
The negative wire: Inverted Audio Signal + Noise (picked up along the cable)
The sound starts at the DAC and travels down the cable. The hot and cold wires inside the cable carry the original and inverted signal respectively. When noise enters the cable via electromagnetic or radio frequency interference, it does so at the same polarity for both wires.
So if the amplifier were just going to take this signal from the wire, sum it, and amplify it, what we’d get would be
(Audio Signal + Noise) + (Inverted Audio Signal + Noise) = Noise
However, this is not how a balanced transmission ends up, because balanced amplifiers only amplify the difference between the two cables! They do this through the use of a balancing transformer that only allow current to flow when signals are opposing.
So before the output gets amplified, the equation actually ends up being:
(Audio Signal + Noise) + (-(Inverted Audio Signal - Noise))
Or
(Audio Signal + Noise) + (Audio Signal - Noise)
The positive and negative Noise get cancelled out, so what we are left with is solely the signal!
While the above described the connection between a DAC and a headphone amplifier, the same would be true about the connection between the headphone amplifier and headphone, provided the cable connections were equipped to properly run balanced.
It is also important to note: only noise resulting in EMI/RFI entering the cable between the sound source and destination would be canceled, and any noise that entered at the source of the sound would not be canceled.
What is the difference between “balanced” and “fully differential”?
In case this is moving a little fast, and you aren't even sure what an amplifier is or why you need one, check out our video about that here to get a quick primer on the basics of what an amplifier is and why you might need one.
So we've learned how a properly balanced headphone chain can get rid of the common noise shared by the left and right signal paths—whether it be a DAC, amp, or headphone transmission line.
But unfortunately, even the terminology “balanced” has subtle nuances and meanings that need to be explained to fully understand what we’re talking about when we talk about a proper balanced system.
The most common use of balanced audio signal transmission has actually little to do with driving headphones in balanced mode.
In many professional audio applications, signals are routed from place to place via balanced cables in an effort to reduce common-mode interference from radio frequency (RF) noise sources like fluorescent lights and motors.
Because the voltage (noise) on the cable run arising from RF interference is identical on both normal and inverted signal conductors, and because the balancing transformers at the input only allow current flow when the signals are opposing, the common interference signal is canceled out.
This problem is not typically an issue even with single-ended headphones because the low output impedance of most amplifiers prevents a significant RF interference noise voltage from ever developing. But there are other reasons to drive headphones with a particular type of balanced amplifier.
Certainly, there are a number of amplifier designs that are single-ended internally, but use transformer coupled outputs; these amplifiers improve headphone performance largely because of the removal of the common ground.
However, there is an entirely different approach that can be used to get significant and measurable performance improvements, often called “fully balanced” or “fully differential” designs. This type of amplifier has completely separate and matching electronics circuits for all four (left normal and inverted, and right normal and inverted) audio signal paths.
The advantage of this design is that there are two power amplifier circuits driving each coil; each amp effectively driving half the coil, with a virtual ground or zero voltage point halfway into the coil. Since each amp is only driving half the load, a significant improvement in efficiency can be achieved. And this doubling of amplifier stages also means (usually) that balanced amplifiers often—but not always—have more available wattage.
This is likely the core benefit of running in a fully-balanced configuration for most people: some headphones like the Hifiman Susvara can actually quite hard to drive with single-ended amplifiers, so fully-balanced designs like the Ferrum OOR or Zähl HM1 are popular for headphones like these.
Unsure if your headphone needs a balanced setup or more power? Check your headphone's specs in our Headphone Power Calculator!
How do I run my headphones balanced?
First, you need a headphone that can accept a balanced connection in the first place. That would most often look something like the traditional dual-entry earcup designs you’d usually find on most high-end audiophile headphones from Sennheiser, Focal, Hifiman, Meze, Dan Clark Audio, ZMF, and others.
Second, your headphone cord must be terminated in a “4 pole” connector on the amplifier side, whether that be a 4-pin XLR or a TRRRS connector (the latter often in the form of a 4.4mm Pentaconn or 2.5mm jack).
[Caption: A balanced headphone cable with dual 4-pin miniXLR cables on the headphone side, and 4-pin XLR male on the amplifier side]
Now that you are familiar with what balanced amps and DACs are and what they do, it’s time to find the right fit for you!
Do you need a balanced amp or DAC for your setup? Click here to browse our selection of options!
FAQ
How can I tell if my headphone chain is balanced or not?
For your headphone chain to be balanced your headphone’s amplifier-end cable termination, your headphone amplifier’s output jack and DAC’s output jacks must have at least a 4-pole output connection, most commonly 4-pin XLR or 4.4mm Pentaconn TRRRS.
This, at minimum, gestures towards the latter two components having balancing transformers to handle the signals, even if the signals themselves are single-ended. To verify if the amplifier or DAC is “fully-balanced,” one usually needs to check the specs of the amplifier in more depth or contact the manufacturer.
For the headphone, generally if it’s terminated in a 4-pin XLR, 4.4mm Pentaconn, or 2.5mm TRRS cable, and has separate cables running to each of the cups, one can assume it is able to be used in a balanced configuration.
Can I plug Single-Ended headphones Into a Balanced amp and get a Balanced signal?
No. You can listen to standard headphones on a balanced headphone amp just fine, you're just not listening in true balanced mode.
Why can't all headphones be used in Balanced mode?
Indeed, even some 'high end' headphones cannot truly be balanced due to their internal wiring construction and/or other design issues. We at Headphones.com would never say a single-ended headphone is inherently inferior to a balanced one, but generally the reason most consumer headphones aren’t made for a balanced configuration is that most consumers aren’t consciously utilizing balanced audio chains.
Can My Headphones Function Both as Balanced Headphones and Single-Ended Headphones?
Yes, you just need to choose headphones that accept dual-cup entry as well as can have their cables removed to swap between single-ended and balanced cables.
Is the actual cable different w/ Balanced headphones?
Yes, the cable braid must have at least four conductors to get the proper balanced signal to the headphones. Many cable manufacturers have their cables internally structured to provide shielding and separation of the left and right channel pairs to reduce crosstalk.