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November 9, 2017

What’s a headphone amp, and do you really need one? You’d be surprised

by John_A

From analog turntables to digital streaming, the way we get our music has transformed mightily over the years. As our music has gone increasingly mobile, headphones, too, have evolved into a daily obsession. Today, there’s a glut of affordable, high-performance options available, promising to enrich our lives with sweet, glorious music everywhere we go.

If you’re reading this article, there’s a good chance you care a great deal about those precious cans you dropped a pretty penny on, and are now wondering if you can improve their performance with a shiny new headphone amp.

The short answer is: Yes. Yes you can. Depending on what kind of headphones you use to mainline your daily soundtrack, there’s a good chance a quality headphone amp — or a headphone amp/DAC (digital-to-analog converter) — can breathe new life into your music. But what is a headphone amp? How does it work? And more to the point, how much do you have to shell out to raise your headphone game? We’re going to answer all those questions and many more.

What is a headphone amp?

Your DAC is an extremely important stop on the good train audiophile.

A headphone amp 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 (or transduced) into soundwaves by the speakers inside your headphones. A headphone amp is like the amps used to power big speakers, but operates at a lower scale.

What is a DAC?

Most modern headphone amps also include an electronic component called a DAC (digital to analog converter). A DAC’s job is to convert digital audio information into a low-voltage signal that an amplifier can use.

Analog components like a turntable or tape deck don’t need a DAC – they already put out analog low-voltage signals – but any digital audio device like a PC, smartphone, iPod, or tablet, need both a DAC and headphone amp in order for you to hear sound with your headphones.

Why do I need a headphone amp?

All those digital devices we just mentioned 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 different headphone amp?

Unfortunately, the quality of those built-in components varies greatly from device to device, and, therefore, so does the sound quality. A MacBook Pro has a decent DAC and headphone amp built in, so it sounds … decent, but many laptops, like the old Dell Inspiron N5110 for example, have very low quality DACs and headphone amps built in, so they sound pretty bad. The same goes for phones: Some sound terrible, some are decent, and some – like the LG V30 – sound superb.

Frankly, if you don’t have a good quality pair of headphones (read: better than a pair of $30 pair of earbuds), you won’t benefit from a headphone amp. But as the quality of headphones increases, so does the potential benefit of using a headphone amp.

Does anyone need a headphone amp? That’s questionable. But might you want one? If you dig great sound, the answer is a resounding YES.

Impedance (aka, the numbers game)

There are certain kinds headphones that really do need a headphone amp to function properly: we call these high-impedance headphones. 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.

As our audio sources have gotten smaller, headphone designers have adjusted.

For headphones, impedance can vary widely, from around 16 Ohms on the low end to as high as around 600 Ohms. (There are some headphones, like the insanely expensive Sennheiser HE1 Orpheus, with impedance far above that number but they usually come with an 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’re curious about the impedance on a pair of headphones, you’ll find it in the manual or specs section online.

Classic headphones like the Sennheiser HD800 (300 Ohms) and the Beyerdynamic DT880 (600 Ohms) were originally designed for use in listening rooms and recording studios with powerful audio gear. Therefore, a headphone amplifier with more voltage than what’s available inside the average smartphone is needed to get these headphones to play loud enough and perform properly. Modern designs such as Audeze’s LCD-3 (110 Ohms) and LCD-4 (200 Ohms), which use planar magnetic drivers instead of more traditional dynamic drivers, also require the power of a dedicated amp for optimal performance.

Not all high-performance headphones are high-impedance, power-hungry monsters, though. As our audio sources have gotten smaller, headphone designers have adjusted. New technology makes high-performance headphones with low impedance possible, and these work well with low-power devices. Audeze’s EL-8 (30 ohms) and Sine (20 ohms) planar magnetic headphones are great examples.

Audeze’s Sine (20 ohms) headphones is one of the best high-performance, low impedance headphones we’ve ever tested. Greg Mombert/Digital Trends

Most in-ear headphones — which naturally utilize smaller drivers that require lower voltage — also generally work fine with portable devices.

While there are no hard or fast rules, if your headphones have an impedance of, say, 50 Ohms or higher, a headphone amplifier is probably a good idea – we would consider you to be in the need camp.  If your cans are below 32 Ohms, they’ll work fine with virtually any consumer audio device. With that said, you could still be in the want camp.

The sound quality quotient (aka, the signal path)

Most commonly referenced in professional audio circles, the signal path — or signal chain — refers to any and all components that make contact with your audio signal. In our case, that likely includes a digital source, DAC, amplifier, a pair of headphones, and finally, your ears. The higher quality the signal path is, the higher the sound quality will be. And though you can’t replace the last stop on the list (yet), the rest are all in play.

When matched up with good headphones, quality amplification can do some very cool things.

You may have landed here to learn about headphone amplification, but we’d be remiss if we didn’t point out that the DAC is an extremely important stop on the good train audiophile. That’s because the DAC is such a critical portal between you and your sound as it changes from digital information — simple code of 0s and 1s — into electrical current. The better that transference point, the better the sound.

Quality amplification can also improve sound quality for virtually any pair of headphones from around the $100 price point up; basically any model built for sound quality over colorways and cute designs. When matched up with a good pair of headphones (and a good DAC), quality amplification can do some very cool things. It can lend more or less color to the sound as desired. It can make your sound clearer and more balanced, or on the other end, warmer, richer, and smoother. A good amplifier can also affect the sound in other ways, including isolating the current running inside your device to limit crosstalk, or interference between stereo channels, which can muddy up the end product.

The best amplifiers and DAC solutions create a purer, clearer, and less distorted signal. And the better the signal that reaches your headphones, the better your sonic experience will be.

What kind of headphone amp/DAC should I buy?

Ok, so you’ve decided to pony up and buy yourself a dedicated amplifier or amplifier/DAC combo. That means it’s time to cash out that Apple stock, right? Not necessarily. There are a number of ways to up your headphone game, at a number of price points. We’ll go through a few to help get you started.

Going mobile

There are a wide variety of quality mobile headphone amp/DACs to choose from. On the high end (though they go much higher) are products like Shure’s excellent SHA900, which can push virtually any pair of headphones you can find (up to 600 ohms), offers versatile input connection and four-band parametric equalization, and high-resolution support at up to 24-bit/96kHz. If the $1,000 asking price is too rich for your blood, there are also much more affordable options like the $60 FiiO A3, which gets high marks from reviewers and can push headphones from 16-150 ohms.

DAC attack

A relative newcomer to the headphone amp game, the USB DAC/headphone amp or DAC stick is one of the easiest ways to get higher quality sound directly from your computer’s USB output. While they require a laptop to take them on the road, they represent a supremely simple and affordable way to raise your signal chain game. Our favorite at present is the DragonFly Red, which costs $200 and is claimed to be able to drive virtually any pair of headphones you can throw at it, even the “lowest efficiency” models like those we referenced above. There’s also the DragonFly Black ($100) for your medium- to low-impedance cans. Another option we like is the Cambridge Audio DACMagic XS, which will also run you around $100 or less.

Desktop decision

The desktop headphone amp is a staple in the industry that should not be overlooked. While often pricey and bulky, these devices are anything but out of date or style for true audio fans, and many represent the absolute best way to take your daily audio to the next level. There are far too many types to outline here, but we’ll go over a couple of very different solutions that stand among our favorite.

The first and more modern of the two is the Oppo HA-1, a gorgeous Class A amplifier/DAC that matches a healthy blend of digital and analog features for incredibly clear and smooth sound. Loaded with features, including everything from digital VU meters and analog volume control to Bluetooth connection and high-resolution audio support at up to 32-bit/384kHz, the HA-1 brings every feature you could want to virtually any pair of headphones you can buy in one gorgeous, hi-res package.

The Amps & Sound Kenzie Headphone Amp. Bill Roberson/Digital Trends

On the other end is the decidedly old-school cool Kenzie tube headphone amp from Amps and Sound. Those glowing tubes on the top will pull in plenty of admirers, while also perfectly outlining our point about sound coloration. Unlike the HA-1, the Kenzie drops plenty of flavor into the pot, serving up warm, rich, and vibrant sound. One of the few options on our list that isn’t a DAC/amplifier combo, the Kenzie sources analog sound from your preferred output, and is therefore dependent upon your DAC. Sound is a shade noisier than more modern amps, and neither of these solutions are the best choice for ultra-sensitive in-ear models. Even when connected to a basic headphone output, though, the Kenzie brings magic to your mix, and should get serious consideration from those with a great pair of over-ears.

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