How a Portable DAC AMP Improves Mobile Music Through Your Headphones

Headphones on headphone stand on desk

Photo from Amazon

Much has changed since the original Apple iPod revolutionized how we consume music on the go. Over time, as electronic hardware has become physically smaller, more powerful, more affordable, and more capable with greater storage capacities, discerning ears have discovered a newfound love for CD, vinyl, and high-resolution audio (in all its forms). The MP3 revolution gave way to convenience. But we’ve now come full circle, back to a point where higher-quality music experiences matter—especially when it’s playing from our portable devices.

The overall quality of music is mitigated by the weakest link. So when plugging headphones into a smartphone, one might think that there are only two parts in the chain when there’s actually more. You have to consider the source of the audio (e.g. CD, digital media, streaming services), the hardware processing the audio (e.g. smartphone, tablet, media player, portable DAC/AMP), the audio connection (e.g. cable via headphone jack, Bluetooth), the audio settings, and the headphones themselves.

An Era of Mobile Music

We’ve come a long way from those early days of 128 kbps MP3s, having learned about the significant sonic differences between lossy vs lossless digital file formats. If the music file/source is low-quality, there’s no amount of expensive devices or headphones that will make the output sound better. It’s all about the weakest link in the chain. This aspect also applies to online music services, too. Sites like Tidal, Spotify, Deezer, and Qobuz offer lossless or CD-quality streaming, but only if you sign up for a monthly subscription. Otherwise, you can expect to have an upper limit of 320 kbps MP3 quality for free streaming, which still doesn’t match what you’d hear from a CD.

Headphones are offered in a wide range of prices, with varying degrees of comfort, features, and sonic prowess. But if you’re using cheap/inexpensive headphones, it won’t matter that you’re listening to hi-res/lossless music files. The audio will be limited by the capability/quality of the headphones if they happen to be the weakest link. However, most of us think to upgrade headphones first, so it’s not often the issue. There are many fantastic options that can be had for US$250 or more, so one doesn’t necessarily have to spend a fortune.

If you want pure and true audio throughput, then you’ll opt for a cable versus a wireless connection; audio cables won’t alter signals. While Bluetooth offers wireless convenience, it comes at the cost of compression, which affects the output. Some Bluetooth codecs (such as aptX) are better than others, but, ultimately, compression will downgrade higher-quality audio sources to fit the wireless bandwidth. While there’s sure to be future improvements to wireless audio streaming, using a regular cable can eliminate all the doubt now and then.

But there is one—arguably the most important—link in the audio chain that is easily overlooked. The middle part that processes the digital source into an analog signal is called a DAC (digital-to-analog converter). You can have top-of-the-line headphones, the most lossless/hi-res audio files, and the market’s best audio cable. But those together can’t compensate for the basic low-end DAC hardware found in most smartphones and tablets, which tend to be the popular products central to mobile music listening.

What’s a DAC AMP?

If an electronic device is able to handle audio and/or can play music on its own, it’s a safe bet that there is DAC circuitry inside. Your smartphone, tablet, and laptop all have DACs—that’s what takes the digital audio information and turns it into an analog signal so it can be sent to speakers/headphones. Basically, you can think of a DAC AMP like a sound card. And in most cases, our devices just work/play and we really don't give the inside functionality a second thought.

Modern desktop/laptop computers have an integrated DAC, allowing you can listen through connected speakers/headphones. A TV that has built-in speakers? It has a DAC. That little stereo CD player boombox with AM/FM radio? It has a DAC. Portable, battery-powered Bluetooth speaker? It also has a DAC. DVD/Blu-ray player? Yup, has a DAC. Home stereo receiver? It definitely has a DAC inside and probably an AMP too (amplifies the signal for greater volume/output). Those bookshelf speakers you love? They do not have a DAC. This is because standard speakers are only able to accept an analog signal sent from a connected receiver/amplifier or device that used a DAC to process the original digital input.

Using a Portable DAC AMP

A portable DAC AMP shares similar functionality to what you might have connected to your home entertainment system, be it a separate component Hi-Fi DAC (such as the Musical Fidelity V90) or inside the stereo receiver itself. Some major differences between portable and standard are the size and the power source—portable DAC AMP devices tend to be easy to carry in pockets/backpacks and often operate from internal batteries and/or USB connections, as opposed to requiring a power outlet. They also vary in size, ranging from small like a flash drive to larger like a smartphone.

One prominent drawback of using a portable DAC AMP with mobile devices is that you have an extra/optional piece of hardware to carry and connect to your smartphone or tablet. It may not be so convenient to use when you're walking around versus sitting in one spot since they connect via cables (e.g. Lightning, Micro USB, USB). Another drawback is that you have one more thing to remember to charge (if it has a built-in battery) every so often. 

When you use a portable/external DAC AMP, it plugs into to your mobile device (e.g. smartphone, tablet, laptop) and works by automatically bypassing the integrated audio circuitry in the connected device. This is desirable for those who want mobile music sounding its best, since many smartphones, tablets, and laptops tend to have the most basic/mediocre audio hardware inside. If you own a great set of headphones, you're not hearing music's full potential through them if you're using smartphone/tablet hardware.

Not All Are Created Equally

Although smartphones and tablets are quite powerful in their own right, limitations still exist. Manufacturers and consumers are primarily focused on major aspects of screen size/resolution, memory/storage, processing power, digital camera technology, and especially battery life. With a finite amount of physical space for electronic hardware, the parts handling audio (DAC AMP) tend to be allotted only the very minimum required to get the job done "just fine," particularly when it comes to mobile devices. So just because your smartphone has a DAC inside, it doesn't mean that it's very good or powerful.

Some smartphones—like the LG V10 or the HTC 10—are designed with fancy Hi-Fi DACs built inside for hi-res audio. However, such options are few and far between in the marketplace. Additionally, many of us upgrade so often, that seeking only the models with enhanced audio can be extremely inconvenient. But the good news is that portable DAC AMP devices are readily compatible with most modern smartphones, tablets, laptops, and even desktops. Since they are separate units, they offer easy, on-demand plug-and-play functionality through the connected cable (e.g. Lightning, Micro USB, USB).

Not all DAC AMP technology is created equally. The best ones are more capable, offer more precision, exhibit less noise/distortion, deliver better S/N (signal-to-noise) ratio, and express a greater dynamic range throughout the entire digital-to-analog translation process. Basically, music sounds notably better. While a bit of an overly-extreme and simplified example, consider the sonic differences between a child’s toy piano and an orchestral grand piano at the hands of a skilled pianist. The former—which we’ll liken to a simple/vanilla DAC AMP—could certainly play recognizable tunes. However, the latter—which we’ll liken to a high-performance DAC AMP—would convey unrivaled acoustic depth and majesty.

Better DAC AMP performance generally involves larger and more complex circuits, which calls for more power to operate. A smartphone or tablet with a high-performance DAC AMP inside is going to have significantly less total battery life than models using basic audio circuitry. Given how most consumers prefer their mobile devices to last longer between charges, it’s understandable why most smartphone manufacturers choose to use basic audio hardware. But this is where a portable DAC AMP comes in since it's able to perform a whole lot better.

What to Expect from a Portable DAC AMP

The evaluation of audio quality is both personal and subjective, like preferential tastes for food or art. Perceived differences in audio output can vary from individual to individual, depending on how well one’s ears are attuned to all the sonic details. But as long as you’re listening to high-quality music from a smartphone/tablet through capable, cable-connected headphones, inserting a portable DAC AMP into the audio chain will elevate the experience. You can expect your favorite tracks to go from sounding "acceptable enough" to anything between "subtly superior" and "absolutely mesmerizing."

With a high-quality portable DAC AMP, music should come across as clearer and more transparent, similar to wiping off a thin layer of dust from a mirror. You should notice a soundstage that feels wider, more spacious/enveloping, and more capable of delivering fuller sound. While the core elements of instruments and vocals may not seem to change too much, it’s the smaller, softer, and/or fringe details you’ll want to listen for. As a whole, performances should exhibit greater vibrancy, crisper imaging, a more natural richness, smoother textures, emotive energy, and notes that are muscular/defined yet musically expressive. Basically, you can expect the music to be driven with authority.

In some cases, depending on the kind of headphones owned (typically higher-end), a DAC AMP is required for the output power. Although many newer headphones are designed so that they can be driven by the low-output of mobile devices, there are those that need the added boost from the AMP in order to function properly.

What About Bluetooth?

All Bluetooth-enabled headphones and speakers have their own built-in DAC AMP. When you think about a chain of audio that includes wireless transmission, music streams from the source (e.g. smartphone, tablet) to the destination (e.g. headphones, speaker). Once that digital information has been passed to the headphones/speaker, it has to go through a DAC first in order to be converted to an analog signal. Then it gets sent to the drivers, which is what creates the sound we hear.

Analog signals aren’t able to be transmitted over Bluetooth. So when using a Bluetooth wireless connection for music, the DAC AMP circuitry in the source device (e.g. smartphone, tablet, laptop) is completely skipped and taken out of the equation. The actual digital-to-analog translation is performed by whatever DAC AMP is in the headphones. So with Bluetooth, you can expect the digital music data to be compromised by both the wireless compression and the processing through a DAC AMP of questionable capacity. Although some headphones may list "hi-res capable" that point towards a certain range of audio quality, very few—like the Sony MDR-1ADAC—detail the exact specifications being used by the headphones/speaker.

Just because the DAC AMP circuits in your headphones may be a mystery, it doesn’t necessarily mean they’re bad. Generally, respected companies that are driven with a focus on the quality of their products are going to use the best hardware—Master and Dynamic touts powerful, custom DAC hardware inside of their over-ear MW60 and on-ear MW50 Bluetooth wireless headphones. But when you want to remove all doubt about how your digital music is being processed, that’s when you use a portable DAC AMP.

Portable DAC AMP Features to Consider

Portable DAC AMP devices come in a range of prices, sizes, and features. It’s a good idea to set a budget limit first, so you don’t end up purchasing more than you need. The top feature to consider is the DAC AMP’s connection compatibility with other devices (e.g. iPhone, Android, PC, Mac).

If you’re using an iPhone or iPad, you’ll want a DAC AMP that supports a Lightning connection, such as the Nexum AQUA. If you’re using an Android-based smartphone or tablet, you’ll want a DAC AMP that supports a Micro USB or USB-C connection. If you’re using a laptop or desktop computer, you’ll want a DAC AMP that supports a standard USB connection, like the Cambridge Audio DacMagic XS. DAC AMP devices can support any or all of these connection types, and more. Some models, such as the Chord Mojo, also have coaxial and/or optical inputs, which allow them to be used with audio sources other than mobile devices.

Some portable DAC AMP devices are self-powered through built-in rechargeable batteries, like the OPPO Digital HA-2SE. These types can be convenient for those who don’t want to supply power through a connected smartphone or tablet. However, such models tend to be larger, often close to the size (and maybe a little bit thicker) than the latest smartphones. Then there are other portable DAC AMP devices, such as the AudioQuest DragonFly, that draw power from the host and are often no larger than a typical flash drive.

There are other important features worth considering. Some portable DAC AMP devices are housed in plastic casings (e.g. HRT dSp), while others use premium materials (e.g. aluminum, leather). Some have a simple interface that consists of several buttons, while others can also sport multiple knobs, switches, and controls. Ones like the FiiO E17K Alpen 2 come with a digital screen to adjust settings. Different portable DAC AMP devices use certain brands/models of DAC AMP circuitry, each of which have their own specifications and strengths. Some portable DAC AMP devices can feature additional outputs, such as RCA and/or multiple headphone jacks.

The Audio Chain

Just remember that a portable DAC AMP can't compensate for low-quality music, Bluetooth wireless, and/or low-end headphones. You have to consider the capabilities of each element in the audio chain: music file, DAC AMP, cable/connection, and headphones. The weakest link can't be overcome by the rest. We can associate this same concept to an example using visuals. A comparable video chain may consist of: computer games, computer video cards (GPU), video cable, and computer screen.

No matter how good a GPU or computer screen you have, an 8-bit video game (think of the original Nintendo) is still going to look exactly like an 8-bit video game. You can have the latest realistic video game and the best available GPU, but it won't do you any good if your computer screen can only display 256 colors. And you can have the latest realistic video game and a computer screen capable of 1080p resolution, but a basic/underpowered GPU will have to downgrade the video quality in order to play.

A portable DAC AMP is similar in function to a powerful GPU, in that it goes far beyond the basic hardware that already exists in devices. But like with many things in life, there's an associated cost, and not all situations are guaranteed to benefit from a DAC AMP. However, if you own quality headphones and often find yourself listening to lossless/hi-res audio files, a portable DAC AMP can be the key to unleashing your headphones' full potential for incredible music experience.