Sources of digital audio are often overlooked due to the abundance of modern devices such as laptops and smartphones that can easily play music. But the truth is not all sources are made equally. And that is made evident when using higher quality audio output devices such as headphones.
The source of your audio is equally as important as the headphones themselves. A bad audio source would negatively affect the overall experience regardless of how much you spend on your headphones. If your source cannot fully power your headphones, then you are not going to get the best results.
This concept can be compared to an electric guitar. An electric guitar produces sound even without a guitar amplifier. However, plugging the guitar into an amplifier helps it produce a wider range of sounds that is similar to the ones you hear in professionally recorded tracks.
If you have mid-range or higher-end headphones and you want to make sure that you are getting the most out of your pair, then you should think about upgrading your source. There are various devices that you can purchase to improve the sound quality of your headphones.
There is the headphone amplifier, DAC, DAC/Amp combo, and preamplifier. For this article, we are going to be solely focusing on what a headphone amplifier is, what types of headphones it is best used with, and other related topics.
What Is a Headphone Amp
A headphone amplifier is a device that is responsible for giving enough power to the drivers of the headphone to produce an audible sound. It works similarly with speaker amplifiers, only on a lower scale. All devices that have an analog audio output (usually a 3.5 mm jack) also have a headphone amplifier.
The quality of most built-in headphone amplifiers is however not designed for headphones with higher impedance. They were typically designed to power consumer-grade earphones such as the ones that come free with smartphones since those only have a lower impedance.
The headphone amplifier inside your smartphone or laptop for example probably won’t be enough for more demanding headphones. Standalone portable or desktop amplifiers, on the other hand, are designed specifically to power harder to drive headphones such as the Sennheiser HD800s that has an impedance of 300 ohms or the Beyerdynamic T1 that has an impedance of 600 ohms. (Power requirements will be tackled in the next question).
Open back dynamic and planar magnetic headphones are the usual headphones that require more power than usual. If you plan on acquiring these types of headphones, it is almost always recommended that you pair them with a good headphone amplifier.
Do I Even Need a Headphone Amp?
Without looking at the specifications, you can quickly determine whether or not headphones require an amplifier by looking at their intended use case. Headphones designed for portable use are usually very efficient and are designed to be paired with a smartphone.
Most headphones in this category have an impedance below 100 ohms therefore they do not need to utilize an amplifier.
Open-back headphones, on the other hand, that are designed to be used in a desktop or indoor environment have a higher impedance, therefore, having higher power requirements. These types of headphones almost always benefit from having an amplifier.
Of course, this does not always apply because there are open-back headphones like the Pioneer SHP9500 that are only rated at 32 ohms and do not strictly require an amplifier to function properly. The proper way of checking whether or not headphones need an amplifier is by looking at the specifications, specifically the impedance.
Low impedance headphones that are less than 100 ohms do not need an amplifier. Headphones with an impedance between 100 and 300 ohms can still be powered without using an amplifier but would benefit from using one. And headphones with an impedance of 300 ohms and above will need an amplifier as the signal you get will be weak.
Will a Headphone Amplifier Improve the Sound of My Headphones?
A headphone amplifier’s primary purpose is to amplify the signal being fed to a headphone. In other words, a headphone amplifier is designed to help bring out (or in some cases, color) the full capabilities of the drivers of the headphones. It is not meant to introduce a sound that is not there in the first place.
Those two headphones have completely different sound signatures and driver technologies used. A headphone amplifier can only help headphones sound more correct but not improve them beyond what their drivers are capable of reproducing.
If a headphone does not need any further amplification, then there would likely be no audible improvement in terms of sound quality. This applies to low impedance headphones. Mid to high impedance headphones, on the other hand, depending on the model, have some benefits.
Apart from the volume, some qualities such as the soundstage and dynamics may have some improvements. This is because the added power to the drivers helps deliver more detail. Depending on the headphone and amplifier used, these improvements may be minor.
For headphones that have an impedance between 100 and 300, like the Sennheiser HD660s or Sennheiser HD58X which have an impedance of 150 ohms, these will usually work without an amplifier.
However, these headphones will greatly benefit from having a dedicated amplifier – because of that, we gave our top recommended Amps (and DACs) for the Sennheiser HD models here.
Again, unless you are using a higher quality source, these headphones would not necessarily sound correct and you would get that congested feel with the soundstage.
As stated above, some headphone amplifiers may introduce some coloration or distortion. This usually happens to tube amplifiers such as the Schiit Vali 2.
Tube headphone amplifiers are known to introduce warmth to the overall sound. This can be useful for taming high frequencies of bright-sounding headphones like the Beyerdynamic T1.
Read our full article with recommended Amps for the Beyerdynamic T1s).
If your goal is to improve the sound quality of your setup, look at changing or adding a DAC instead. A dedicated headphone amplifier is meant to be used with a standalone DAC.
Headphone Amplifier vs. Headphone Preamplifier – What is the Difference?
Traditionally, the amplifier section for speaker setups is separated by the preamplifier and the power amplifier. To put it simply, the preamplifier houses the volume control and is responsible for source selection. It can also influence the sound. The power amplifier, on the other hand, is responsible for giving power and thus driving the speakers.
Some headphone amplifiers combine the two and are called integrated headphone amplifiers. An example of this is the Schiit Magni 3. Units that already combine a preamplifier and power amplifier for headphones can help your stack setup be more compact as you’d only need 2 units (amplifier and DAC).
As mentioned earlier, headphone preamplifiers may affect the sound of your setup. Tube preamplifiers can give warm coloration to your solid-state headphone amplifier if you prefer this kind of sound. It still depends on the synergy of your gear. Also, pairing a headphone preamplifier with a headphone amplifier may cause some issues as you have to match their volume levels.
If you are new to the hobby and do not have much experience with these kinds of gear, then generally a headphone amplifier would already be sufficient for your needs.
When Not to Use a Headphone Amplifier?
It is not recommended to use a headphone amplifier if your headphones are not designed to use them. Lower impedance headphones will have little to no benefit from using a headphone amplifier. In fact, introducing too much volume can cause damage to the drivers, to your hearing, or to both.
If you wish to improve the sound of your low impedance headphones such as your portable headphones, then changing your portable source or adding a portable DAC/amp may be a better option. Switching from a smartphone to a DAP such as the Astell & Kern A&Norma SR15 would benefit your headphones because it has better internal audio components.
A portable DAC/Amp also does the same thing but in a slightly bulkier package. It is similar to a standalone desktop amplifier but already includes a DAC and usually has less power than a desktop amplifier so it is safer to use for lower impedance headphones. The DAC already gives enough difference in sound quality to hear an audible improvement for your portable headphone.
If you already own a headphone amplifier and do not want to unplug it just to use low impedance headphones, then you can still plug them into it. Just be careful and try not to increase the volume too much in order to avoid damage to the drivers.
Another scenario where a headphone amplifier should not be used is when dealing with sources that do not have a dedicated line-output such as a smartphone. In order to properly utilize an external headphone amplifier, a device must have a dedicated line-output. This is because connecting your headphone amplifier via the 3.5mm headphone out-produces the double amping effect.
Double amping happens when a source’s internal amplifier is not bypassed when connecting a standalone headphone amplifier. This means that both the internal and external headphone amplifier is working at the same time. This produces an output that may be noisy and distorted.
For smartphones or budget DAPs such as the Sony NW-A55, it is recommended to use a DAC/Amp instead. Most of these devices that lack a dedicated line-output have a digital output that can be connected to most DAC/Amps.
To summarize, do not use headphone amplifiers with low impedance headphones (especially if you are expecting a drastic improvement in sound quality), and do not use headphone amplifiers with devices that do not have a dedicated line output.
What Happens If I Use a Headphone Amplifier Without a DAC?
If you do not pair your headphone amplifier with a standalone DAC, then the headphone amplifier will utilize the internal DAC of the device being used as the source (Personal Computer, smartphone, etc.). If the source has a bad quality DAC, then this will be further amplified by the headphone amplifier producing less than desirable results.
It is therefore almost always recommended to use a dedicated DAC along with your headphone amplifier. Not only do you get a cleaner and better quality sound, but you also get additional benefits such as native decoding of unconventional files such as DSD as long as your DAC supports it.
If you have a high-quality source such as a dap, then it is okay to use a standalone amplifier with it. The DAC is most likely already good enough and would not deteriorate the sound that would be amplified by the headphone amplifier. Just make sure that you are utilizing a line-out connection to prevent double amping.
Do I Need An Amplifier For My In-Ear Monitors (IEM)?
In-ear monitors, in general, have a low impedance. This means that most in-ear monitors do not need a headphone amplifier. In fact, in-ear monitors are the opposite of headphones. A lot of high-end headphones need more power while a lot of high-end in-ear monitors need less output.
Similar to low impedance headphones, in-ear monitors may potentially be damaged if too much power is introduced. Again, amplifiers are not designed to make your gears sound better unless there are side effects such as distortion from tube amplifiers that you may perceive as better. If you wish to get more details out of your in-ear monitors, look at a DAC or DAC/Amp instead.
Plugging in in-ear monitors to a DAC/Amp on the other hand such as the iFi Micro iDSD Black Label is safe because it is not purely designed to amplify signals. Also, amplifiers such as these have a low gain switch that makes sure lower impedance headphones or in-ear monitors do not get damaged. When plugging in low impedance gear, always make sure to set the volume lower and engage the switch for low gain.
Solid-State Headphone Amplifier vs. Tube Amplifier –What Is The Difference?
There are 2 common types of headphone amplifiers. There is a solid-state and tube headphone amplifier. There are several distinct differences. The first one is how they physically derive their amplification.
Solid-state amplifiers derive their amplification from electronic transistors while tube amplifiers use vacuum tubes. Tube headphone amplifiers use a cathode ray tube in order to produce sound.
The second difference is how they color the sound of the headphones.
Solid-state headphone amplifiers such as the Beyerdynamic A20 give an accurate sound that is free from coloration.
A tube amplifier, which is an old technology, is often associated with vintage gear. Thus, it tends to add coloration to the sound of the headphones. This isn’t a bad thing, in fact, this added warmth is preferred by users who have bright-sounding headphones and wish to tame the peaks in the treble area.
Tube amplifiers also have a modular aspect. The vacuum tubes can be replaced with different types which can give various effects. Hybrid tube amplifiers such as the Schiit Lyr 3 have the ability to sound like a tube amplifier as well as a solid-state amplifier.
To summarize these points, a tube headphone amplifier is more of a modular unit that can have various effects on the sound but is not totally accurate. Solid-state amplifiers, on the other hand, give less coloration which gives a more accurate sound. Depending on what your needs are, one might be a better fit for your setup over the other.
Stephen is a musician, cinematographer, and headphone enthusiast who is passionate about reviewing audio equipment. He has been playing guitar for at least a decade, which introduced him to professional recording equipment such as headphones and in-ear monitors. With the help of reviews and online content, he was able to learn the ins and outs of the hobby. His goal is to give back to the community by providing quality content to help others enjoy the beautiful (and expensive) world of audio.
Favorite Headphones: Sennheiser HD660s