First off, a headphone itself cannot be balanced or unbalanced. It is a set of speakers, so it is unable to do common-mode rejection. The connections to the headphone, however, can be balanced or single-ended. Therefore, the question becomes is a balanced headphone amp or a single-ended headphone amp better? Let's look at some ways that amps create balanced connections and see how the overall design affects what will work best with your set of headphones.
Operational Amplifiers Versus Transformers
Balanced circuits between components can be done in two different ways: operational amplifiers and transformers.
You can work with operational amplifiers (opamps) and split the single-ended circuitry into dual-operational amps to create a balanced connection, though doing so would not create a true balanced circuit. It would be considered a pseudo-balanced circuit because the circuit internally is single ended but is transferred/converted to a balanced circuit just to do common-mode rejection between the two components. For reference, a “true” balanced connection would be balanced from input to output, without requiring operational amplifiers or transformers for signal conversion. The Bryston headphone amp is not a 'true' balanced headphone amp even though it has balanced inputs and balanced outputs. They use operational amplifiers by changing the input to single ended, installing a single-ended circuit and changing it to a balanced output for the headphone jack.
Then we have balanced headphone amps like our Dragon Inspire, which has a transformer coupled output. A transformer doesn't care whether the input or output is balanced or single-ended. In the Dragon Inspire, we have a single ended tube (SET) design, which sends the signal to the transformer, which then splits the positive and negative from each other so we can have a 4pin XLR for balanced output on the headphone jack.
A transformer is a winding of coils and the signal essentially jumps from one coil to another. It strips all the noise, it doubles the power, separates the left and right channels, grounds, etc.
The Differential Amplifier
When talking about "balanced" headphones and any kind of similar headphone amp, we are essentially referring to a differential amplifier or differential signaling. If you think about an old two-channel car stereo, you could bridge each channel together and get double the output/power. It might not always be double the power output (it really depends on the circuit), but ultimately, you've increased the overall output. You've also made the circuit more efficient. Not only is it more powerful but it's also a lot quieter because it operates at a lower load capacity on the power supply, etc. Differential amplifiers are a type of operational amplifiers, which are a core component of achieving this balanced circuitry.
Any headphone amp is what we call a differential amplifier circuit. It's not common-mode rejection. You can't do common-mode rejection with a headphone because it's a speaker. There's no send and receive - you're just sending the signal to the headphone - so it's different. People get very confused about that.
Common-mode rejection can also work as a splitter to make the lines quieter. Not a lot of products are "truly" balanced. You'll see more headphone amps that are truly balanced versus speaker amps, cd players, or preamps because it's more expensive to create truly balanced products.
If we’re being completely honest here, most headphone amplifiers are designed with pseudo-balanced circuits as a cost-saving method. To make a “true” balanced circuit, you would have to double all the circuitry from input to output. By doubling the circuitry, you are also doubling the cost to produce. If the one clear answer we have on this page is that true balanced circuit design will always sound better than single-ended, and if the cost wasn’t an issue, then everyone would design their amps the same way. But the cost is always a factor because when something is expensive to make, it’s also expensive to buy! Again, this only applies to true balanced circuit design, which is rare in the market.
Any headphone amp is what we call a differential amplifier circuit. It's not common-mode rejection. You can’t do common-mode rejection with a headphone because it's a speaker. There's no send and receive - you're just sending the signal to the headphone - so it's different. People get very confused about that.
An amplifier provides output power to a set of headphones. Depending on your application or set up, it might be possible that you need additional power, say if you have headphones that have power-hungry drivers. For example, if you are listening to music on your phone but don’t have enough juice to power your headphones, it will result in very poor audio quality.
It is also important to keep in mind what kind of connections your headphones have. If you have a balanced connection (XLR) on your headphones but a quarter-inch output on your headphone amplifier, it won't work, unless you have a compatible cable. Here at Moon Audio, we can create custom solutions for your headphones. Again, it is not your headphones that are balanced or unbalanced, but the connection to the speakers. These cables and connectors can be switched out with various options depending on if the stock option is not your preference. Different connectors, impedance ratings, and other factors that will be crucial to factor in when deciding what kind of headphone amplifier you will need.
Here are some examples of single-ended and balanced headphone amp options:
NOTE: Keep in mind that there are various types of headphones amps and configurations based on balanced, single-ended, as well as multiple connection types. For instance, the Dragon Inspire IHA-1 has both single-ended and balanced options on the device. The Bricasti M3H is a full-balanced signal path, which as we mentioned is rare. Be sure to check these types of specs when researching your next purchase to see what is best for your system.
Which Connections Should I Use?
Sometimes a customer will ask, "Should I use the balanced outputs or the single-ended outputs?" If it's not a true balanced design, most of the time we'll recommend using the single-ended outputs, because it's very possible that depending on how they manufactured the pseudo-balance, it can actually deteriorate the sound, even though there's a voltage increase on that output. Feel free to reach out to us about specific hardware you may be considering; we’ll be more than happy to take the time to determine if it is the right piece for your system.
Getting back to single-ended versus balanced connections on headphone amps, if you compare the single ended output to the balanced output on the same product, and it's a true-balanced headphone amplifier, the balanced will always sound better than the single ended. On an Astell & Kern player, the 2.5mm output will always sound better than the 3.5mm output. That is unless you have an IEM or a headphone with an abnormal impedance rating. The Shure SE846 in-ears has an abnormal impedance rating that actually sounds better on the single-ended than the balanced. That's a really rare case. There's a custom 300V Cary Audio amp we used to make as an upgraded version of the original single-ended headphone amp. It's an example of a single-ended amp that sounds better than most of the balanced headphone amps we sell, except for maybe the Auris Nirvana. Ultimately, it comes down to the design.
You could have two amps that cost $1000, one being single-ended and the other balanced. The balanced one may not necessarily sound better than the single ended. It just depends on how good the circuits are, who the designer is and how they manufactured it. However, as mentioned previously, if the circuit is a true balanced design then in all cases it will sound better than a single-ended circuit. There are just not a lot of true-balanced amps on the market because they are much more expensive to produce.
Q: What if my headphone amp has a balanced output but my headphones have a single-ended connection?
Remember, headphones are just speakers, so it doesn't matter if the cable is balanced or single-ended. What matters is what you are connecting them to. In the case where you have mismatched connections, we can create a custom cable solution just for you that will be compatible with your system.
Keep in mind that apart from the headphone amp, cables can also make a difference in the sound quality and fidelity you are getting from your music. Though this isn't necessarily the platform to be talking about cable materials, it is directly related since we are on the topic of headphones and compatible cable systems. See more information on our award-winning Dragon Cables HERE. Also, learn about each cable's specific sound signature, so you'll be able to pair the right cable with your headphones for that perfect sound.
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