What is a headphone amplifier?
A headphone amplifier is a relatively low-powered amplifier that raises the low-voltage audio signal from a source device (be it a turntable, PC, or smartphone) to a sufficient level such that it can be converted into sound waves by the speaker drivers inside your headphones. It works just like the amps used to power full-sized speakers but operates at a smaller scale. Headphone amps are most useful with certain power-hungry high-impedance audiophile headphones that can benefit from the improved clean power of a dedicated amp. A headphone amp can improve detail resolution and dynamic range extension and maximise overall musical clarity & coherence.
Do I need a headphone amplifier?
Most digital devices like smartphones & computers already have a DAC and headphone amp built right in – that’s why you can just plug your headphones in and hear sound. Why then, would you need a separate component? Unfortunately, the quality of those built-in components varies greatly from device to device and therefore, so does the sound quality. The quality of the amplifier in your smartphone or laptop is just good enough to make your headphones work, but they have not been designed to offer you a good quality listening experience.
If you are not using a good quality pair of headphones (anything up to a $50 pair of earbuds), you won’t benefit from a headphone amp. But as the quality of your headphones increases, so does the potential benefit of using a dedicated headphone amp. However, if you are using a pair of high-impedance headphones, the power being produced by your smartphone or computer will not be adequate to drive them and in this case, you have to use a headphone amplifier.
What is impedance?
Impedance refers to the resistance of an electrical signal and is measured in ohms. The higher the impedance, the more resistance a pair of headphones or speakers will give to an electrical signal.
For headphones, impedance can vary widely, from around 16 ohms to around 600 ohms. There are some headphones with an impedance far above that value but they usually come with their own dedicated amp. The higher the impedance, the more amplification power is needed to drive the headphones and the more likely a headphone amp would be beneficial. If you’d like to know the impedance value of a pair of headphones, you’ll find it in the manual or the model specifications published online.
Some audiophile headphones have been specifically designed for use with powerful audio gear in listening rooms or desktop systems. Therefore, a headphone amplifier with more voltage than what’s available inside the average smartphone is needed to get these headphones to play at desired volume levels and perform properly. Headphones that use planar magnetic drivers also require the power of a dedicated amp for optimal performance.
If your headphones have an impedance of 50 ohms or higher, a headphone amplifier is probably a good idea. If your headphones are below 32 ohms, they’ll work fine with virtually any consumer audio device. With that said, you may still want to use a headphone amplifier for sound quality reasons.
The quality of the signal path
The signal path refers to all of the components that interact with your audio signal. It’s all the pieces of equipment that are involved from the moment of generating the music signal to the moment of you experiencing the signal as music. Your signal path is likely to be:
A Digital Source → DAC → Amplifier → A Pair of Headphones → Your Ears.
The higher the signal-path quality is, the higher the sound quality will be. Though you can’t replace the last stop on the list (yet), the rest are all worth considering.
A digital source is something that sends the musical information to the DAC. These can be desktop computers, laptops, streamers, music servers, hard drives, CD transports… any device that sends a music file (in the form of ones and zeros) to the DAC. These source components are important because this information can be sent in a way that contains noise, information errors or timing errors. The higher the quality of the digital source, the better this information transmission will be. High quality digital sources are engineered to send a music file in the right order with all of the critical timing (clock) information intact without any electrical noise.
The DAC (Digital to Analog Converter) as the name suggests converts a digital signal into an analog signal. More specifically, it converts the signal received from the digital source which is in the form of ones and zeros into current. The DAC is a critical component because the better this conversion, the better the sound quality. It is responsible for converting the information from digital form into a form that can be experienced as music. As the quality of the DAC improves, the sound becomes purer, more accurate to the original recording, cleaner with less distortion and more natural sounding.
Quality amplification is then paramount for achieving great sound. It can ‘colour’ or ‘flavour’ the sound to suit your taste. It can make the sound clearer, balanced, present the micro-details or emphasize the timbral qualities of the music. It can make the sound warmer, richer, smoother, emphasize a more natural tone or emphasize the more structural aspects of the music. As an amplifier gets better, it tends to do all of these things better. A good amplifier can also affect the sound in other ways, including lowering the noise floor, isolating the current running inside the device to limit crosstalk (interference between stereo channels) which can smear the sound.
The headphones have the job of converting this carefully managed signal that has been cultivated by the digital source, the DAC and the amplifier into sound waves for you to enjoy. There are many types of headphones with different ways of performing this critical function. In recent years, the level of research & development that has been invested into headphone design & engineering has been extraordinary and as a result, we have been blessed with an incredible selection of headphone technologies. When you find the type & model that suites your preferences, it can be an ethereal, mind-blowing experience!
Remember that an audio system is only as good as its weakest link. If you have well-recorded music and great audiophile headphones but are relying on the low power/quality headphone amp inside your laptop to make your headphones sing, there’s no way that you will be driving your headphones to their full potential.