Digital-to-analog converters (DACs) are all the rage nowadays, as digital audio file playback continues to increase in popularity. There are many varieties of DAC: the DAC/preamp, CD/DAC, USB DAC and beyond. The central functionality is the same: to take a digital signal from a source (a digital file stored on a physical medium like a CD, SACD, or DVD-Audio disc or in a computer, media server, or NAS drive) and convert it to an analog signal that an amplifier can accept and work its magic to drive beautiful music through your speakers. As a traditional AV enthusiast, I already have a very competent DAC that's built into my Oppo BDP-105 (using the critically acclaimed ESS Sabre ES-9018 platform), which I use to play all shiny, spinning discs and which also has a USB input for playing any number of digital files. Other enthusiasts probably have something similar built into their AV preamp or receiver if their music system doubles as their home theater. But the concept of home theater and music enjoyment is constantly evolving, and that's what we love about this hobby.

The USB DAC caters to the group of audio lovers who primarily listen to digital files stored on the computer. Oftentimes, a computer's internal DAC (depending how nice of a sound card you have) can be a little deficient on sound quality or may lack proper analog outputs to work with most amplifiers. Retailing for $499, Denon's new DA-300USB DAC weighs a mere 3.3 pounds and features a 32-bit DAC that can handle sample rates up to 192 kHz. To support the many different sample rates possible, Denon has built in two separate master clock crystals, one for 44.1 kHz and one for 48 kHz to provide maximum accuracy with just about any common sampling frequency out there today. It can also decode DSD signals, including both DSD-64 and DSD-128 (commonly referred to as double DSD). Inputs include one asynchronous USB, one coaxial digital, and two optical digital. Output options include a stereo analog RCA in the back and a headphone out in the front that fits a quarter-inch connector. The front panel is fairly minimalist in design. In addition to the headphone output, there's a power button, a volume knob, and an OLED display that shows the volume level and current source, with its file type and sampling frequency.

The Hookup
Included in the box is a custom bottom plate that, when attached, allows the Denon DAC to stand vertically - similar to the way many people like to position an external hard drive on the desktop - which is a thoughtful, space-saving design. Since I tested the unit with my main stereo rig in the living room instead of a desktop system, I decided to skip the bottom plate and just lay the Denon flat horizontally.

I primarily played music files from my HP Envy laptop using both the built-in HP Connected Music player, as well as the Foobar2000 media player (for testing DSD files). I connected my laptop to the Denon via a standard Belkin USB cable. While many users will not need an additional preamp when using the Denon, I wanted to keep everything else in my reference system as similar as possible, so I fed the analog signal (using Monoprice RCA cables) from the Denon's output into my Parasound JC-2BP preamp with Crown XLS-2500 amplifiers driving my Salk Soundscape 12 speakers. Basically, the Denon took the place of the Oppo BDP-105 that I normally use as a DAC for digital music files.

Click over to Page Two to find out about the Performance, the Downside, Comparison & Competition, and the Conclusion . . .

Performance
Amazon has an AutoRip utility that allows you to download MP3 file copies of all songs contained on certain CDs that you buy from Amazon. I wanted to compare the same music across a variety of file types and resolutions, so I ripped a few of my CDs this way. I started with one of my favorite singers, John Legend, with the track "All of Me" from his latest album, Love in the Future (Columbia). Legend's characteristically raspy voice was clear and easy to discern. His piano sounded a little compressed, lacking the dimensionality that I knew to be there. But overall, the sound was still quite enjoyable. The Denon is a lot more forgiving with MP3s than a lot of DACs I've listened to. I've heard a lot of high-end DACs that perform perfectly with a high-resolution audio file but sound terrible with MP3s. I found the Denon refreshing in this respect, and frankly I think it's a big plus for a modestly priced DAC like this one that's designed to cater to a wider audience, including folks who are perhaps just getting their feet wet with higher-resolution audio but still have most of their collection in lower-sample-rate formats. I'm a firm believer in buying the right gear to suit your own musical tastes, rather than letting the pursuit of better gear dictate what you can listen to.

Next, as an experiment, I plugged the CD copy of the same album into my computer's CD drive. Listening to the Legend CD and a few others I had on hand, I didn't hear a significant improvement over the MP3 files. Keeping the computer as the source device for CD playback might seem like a logical choice - same source, same DAC, same signal chain after the DAC. But here's the thing: the run-of-the-mill CD player that HP decided to stuff inside my laptop hardly rivals my usual Oppo BDP-105 disc player -- which reads and decodes the music, provides error correction on the fly, and streams the data to the Oppo's internal ESS Sabre DACs for analog conversion and output to the rest of the signal chain. To confirm this difference, I connected my Oppo to the Denon using a Blue Jeans coaxial digital cable, using the Oppo as the disc spinner but bypassing its internal DACs and allowing the Denon to perform the "Dac(ly)" duties. Legend's piano now had that heft and richness that I expected to hear. The texture of his voice now crystallized to an even clearer picture, and I could hear all the gritty nuances. Other details began to form, like the resonances from the piano's cabinet, microphone effects like ever-so-slight reverbs, and sibilance from Legend's voice - all adding greater dimensionality to the presentation.

Time to move on to higher-resolution digital files. The presentation of Patricia Barber's "The Wind Song" from her Smash album (Concord Jazz, 24-bit/192-kHz FLAC) was immaculate. Her voice was crisp and gravelly, but most impressive was how lifelike the accompanying instruments were. The acoustic bass sounded tight and controlled. I felt like I could hear the tension in the strings as they were pulled back and released with a pluck. The piano was rich and well defined. And then came something I didn't expect to hear from a sub-$500 DAC... A piano creates sound by striking its strings with a hammer. The wooden hammer is usually wrapped with a felt covering. Thicker felt often creates a muted or dampening sound, which is quite a contrast with the sound of brighter resonating strings. In the midrange, this creates a uniquely rich tone that begins with the thud or muted strike. As a pianist in my youth, this was a strangely familiar sound I heard coming through my system. I guess those are the little spatial and timbral details that you don't get with compressed audio that are only revealed with higher-resolution recordings. The details that get you closer to believing it's a live performance.

Playing this same file through the Oppo's DAC produced a slightly quieter background, with a sound that was a little more open. The character of the each of these DACs is different. With the Oppo, I got a more matter-of-fact, neutral sound, probably a little crisper and more detailed in the upper range. The Denon sounded a little warmer, especially in the midrange - a sound that I had previously associated more with sister company Marantz than with most Denon products I've heard.

DSD playback was similarly riveting. I played through the Allegro Con Spirito movement of Tchaikovsky's "Souvenir de Florence" (2L, 5.6M Stereo DFF) as performed by the Solistene Sondheim, a wonderful group of string soloists from Norway. I heard something that separates the Denon (and other high-end DACs) from the ordinary pretenders. Classical stringed instruments, especially the violin in the upper registers, have this funny way of starting off with a nails-on-the-chalkboard screech as the bow gets dragged on the strings while simultaneously producing the some of the sweetest, most pleasant tones. You hear it in live music; and, with the most carefully recorded, high-resolution presentations like on a 2L-produced double DSD file, it's again possible to hear when played through a very competent component. The fact that, at under $500, the Denon DA-300USB DAC can provide this level of quality is no small testament to its value.

Lastly, I took out my Skullcandy Hesh 2 headphones and plugged them into the Denon's headphone jack. Since my headphones were designed for a one-eighth-inch connection, I had to use an adapter. Running through many of the same tracks and files I tested through my speakers, I found, unsurprisingly, that the Denon was an equally adept performer through its headphone output. I heard the same level of detail and clarity. The same slightly warm midrange bloom I spoke about earlier was also present, and very pleasing to listen to, especially on orchestral pieces. Sense of scale is obviously different compared with the room-filling experience of having large speakers powered by high-powered amplification. Comparatively, I found the Oppo's headphone amp to be a little better in this regard, giving a slightly larger sense of scale and, in addition, providing a tad tighter bass control.

The Downside
There's not a lot I can fault the Denon unit for, especially at this price point. If I had to be absolutely critical on sound quality, I would improve with a quieter background and maybe a little more open sound. But again, I haven't heard any competitive options that are less expensive and can perform better on these fronts. One wish would be for balanced (XLR) outputs. Many computer audio enthusiasts like to use professional, powered nearfield monitors that work best with XLR inputs. And of course, many higher-end amplifiers have fully balanced designs.

Comparison and Competition
At a lower price point, you have the popular Audioquest Dragonfly, which in its current version 1.2 retails for $249. The Dragonfly is smaller and even more portable, being about the size of a USB thumb drive, but it only handles sample rates up to 96 kHz, so the highest fidelity files won't work with it. Furthermore, the only output is a 3.5mm headphone out, which means you need an adapter for many audiophile-grade headphones and connecting to a traditional setup would be difficult. And honestly, the Denon would be a significant step up in sound quality in my book. The $189 Cambridge DacMagic XS is another portable USB DAC/headphone amplifier that accepts up to 24/196, but it also has fewer inputs and outputs.

At $475, the Parasound zDAC probably provides the closest competition in terms of price, sound quality, and features. While the Parasound also accepts signals with sampling rates up to 192 kHz, this is only true with the optical and coaxial digital inputs. The USB input on the Parasound only accepts up to 96 kHz; so, if most of your highest resolution files are stored on your computer or if that's how you otherwise access them, the Denon would be the more versatile choice.

As you move up in price, such as with the Rotel RDD-1580 for $799 (and certainly beyond), you can expect an improvement in sound quality. However, since the Rotel lacks the ability to decode DSD files, the versatility of the Denon still makes for a compelling argument in many respects.

Conclusion
The Denon DA-300USB fills a unique void in the world of DACs. While being larger than the many thumb-drive-style USB DACs, it is still small enough and light enough to fit in any small compartment of a backpack. Although a step up in price, $499 is still quite reasonable compared with some options that can cost as much as an exotic sports car, all the while giving a taste of far better sound quality and versatility in connection options. If you store your files on or primarily listen to digital audio files through your computer and want a unit that is portable or sometimes want to hook up your computer to a bigger traditional stereo rig, I highly recommend the Denon DA-300USB DAC.