What Is a Headphone Amplifier?
A headphone amplifier is a low power amplifier specifically designed for on-ear or in-ear listening devices. They come in all shapes and sizes, from integrated modules to standalone devices. Like standard hi-fi amplifiers, most are solid-state but some use analog valves.
There’s a good chance that the device you’re using to read this article has a headphone amplifier in it, whether it’s a smartphone or a notebook. This type of amplifier is designed to drive the vast majority of headphones, which are known as low impedance headphones.
Why Might You Need a Headphone Amp
If you’re using headphones with a particular device and you find that the volume simply isn’t loud enough, a headphone amplifier can be used to boost the signal and provide a higher output volume.
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One reason your headphones might not be loud enough is that the integrated amplifier can’t provide enough power to drive them. Most headphones are designed with an impedance of 50 ohms or less, which means they can be easily driven by most small devices like smartphones and notebooks. The higher the impedance, the more power the headphones will require.
The sensitivity of your headphones also plays a role, since this dictates how loud your headphones will be (measured in decibels, or dB) at a certain power level (measured in milliwatts, or mW). If you buy a pair of headphones you will see these ratings featured in the specifications, but since most headphones are low impedance and designed for use with everyday devices, you’d be forgiven for not paying too much attention.
High impedance headphones are typically characterized by drivers that use thinner voice coils. Thinner coils are more difficult to manufacture since they use more layers of wire compared to low impedance models. This means less air in the windings of the coil and a stronger electromagnetic field.
Such headphones (like the Sennheiser HD 660 S) are “harder” to drive, which is where headphone amplifiers usually come in. The result is widely considered to sound better, with less distortion compared to lower impedance models. It’s not necessarily a difference you’re going to glean from reading a description on the web, so you’re better off heading to a hi-fi retailer and having a listen to see for yourself.
High-end electrostatic headphones (sometimes known as “earspeakers”) require an amplifier specifically for that type of listening device. These headphones (like the Mitchell and Johnson MJ1 and similar Stax models) don’t use moving parts like common models which rely on an electrodynamic coil but rather an ultralight film. They’re widely considered the most natural and accurate headphones you can buy, but they don’t come cheap (particularly when you factor in the price of a good amp).
In other words, if your headphones sound plenty loud enough and you aren’t using fancy in-ear monitors or over-ear headphones, you probably don’t need a headphone amplifier.
If you’re finding that your headphones are too quiet, you’ll have to match their sensitivity (measured in decibels) and impedance (measured in ohms) with a suitable headphone amplifier.
Different Types of Headphone Amplifier
The most common type of headphone amplifier is Integrated into most mobile devices, including MP3 players, smartphones, and notebooks. These are designed to drive the most common types of headphones with an impedance of fewer than 50 ohms. Most models of headphones get plenty loud enough under these conditions.
Some devices, like Apple’s 2021 16-inch and 14-inch MacBook Pros and some high-resolution portable audio players can drive headphones with higher impedance, but this is the exception rather than the rule.
There are also portable headphone amplifiers that are powered by batteries and designed to provide a higher volume output on the go. They may be useful in driving headphones with higher impedance, but they require additional space and battery power which may be inconvenient. One example is the FiiO A3 which is suitable for driving headphones with an impedance of up to 150 ohms.
Many headphone amps also act as external digital-to-analog converters (DACs) in addition to boosting the signal. These are useful if you’re finding that the DAC built into your device is producing unwanted noise or interference. Some of these external DACs like the NextDrive Spectra X are ultra-portable and don’t require additional batteries.
Then there are standalone headphone amps designed for home listening like the iFi ZEN CAN, designed for home listening use. These are to be paired with pricier, high-impedance over-ear headphones for a richer listening experience. They take up less room than the sort of amplifier you would use to drive loudspeakers, and they’re one of the most budget-friendly ways of getting into “audiophile” hi-fi equipment.
Finally, there are also headphone amplifiers designed for studio use, with audio professionals in mind. These often allow for more than one set of headphones to be connected to a balanced source, suitable for producing and mastering music and other audio productions.
Wireless Headphones Don’t Need a Separate Amp
Wireless headphones and earphones already have an integrated amplifier and DAC inside of them. Most headphones of this type are purely wireless, so there’s nowhere for them to “plug in” and receive a boosted signal.
These headphones are designed with low-power Bluetooth audio in mind. They often sacrifice audio quality in the name of convenience, since the audio signal must be compressed before it leaves the device and makes its way wirelessly to the headphones.
Wireless headphone amplifiers like the FiiO BTR3K do exist, but they serve a different purpose. These devices add Bluetooth functionality to wired headphones and earphones, providing an additional boost in signal and better digital-to-analog conversion using a DAC that’s superior to most integrated models.
You Probably Don’t Need a Headphone Amplifier
Most headphones don’t need a signal boost, since most are designed for use with low-powered devices like smartphones and portable audio players. If your headphones are loud enough for your listening habits, you probably don’t need one. If you use wireless headphones like AirPods or similar Bluetooth models, you don’t need one either.
If you’re looking for an audio experience like no other, high impedance headphones and a good amplifier offer a great starting point. You’ll be able to get a complete setup for less than the price of a high-end amplifier or set of speakers, and there are fewer variables like room acoustics to account for.
But more people than ever are going for convenience over sound quality, as they trade wires for wireless technologies like Bluetooth. Check out our top recommended wireless earbuds for iPhone and iPad. If you’re not ready to cut the cord yet, we’ve also got a list of our best headphones.
