Many Playback readers have become fans of portable hi-fi systems where the notion is that all—or nearly all—system components should be small enough to fit in your pocket, handbag, or backpack.
For many listeners, the game starts by acquiring a good set of earphones or perhaps custom-fit in-ear monitors that can be plugged directly into an iPod or other portable digital music player (including, in some cases, laptops, netbook or tablet PCs, etc.). But over time, the logical progression of things—not to mention our innate desire to take musical excellence to the max—often leads us to a quest for high-quality portable amplifiers (some of which come with onboard DACs).
With that thought in mind, let’s take of a look at four of the best portable amplifier options Playback has encountered thus far, weighing the particular strengths (or possible downsides) of each model in turn.
ALO Audio Rx Mk2 Portable Headphone Amplifier ($449)
What it is: A pure, straightforward, and beautifully made headphone amplifier (sans onboard DAC) that can successfully drive a very wide range of earphones, in-ear monitors, and headphones.
Why you might choose it: To paraphrase the words of acerbic political advisor James Carville, “It’s the sound, stupid.” In a world where many headphone amps sound a bit bright, brittle, and a little too edgy for their own good, ALO’s Rx Mk2 offers a wonderfully warm, rich, natural sound that offers vibrant tonal colors and enough power to drive most headphones.
Visit one of the popular Head-Fi Can-Jam events and you’ll see any number of headphone/earphone manufacturers using the Rx Mk2 as their reference amplifier of choice. There are at least four reasons for this. First, the little ALO is beautifully made and very sturdy. Second, the amp’s onboard battery pack and clever charging system make for A) lots of playing time per charge, and B) the ability to do partial recharges without having the battery develop a “discharge memory” that will limit playing time in the future. Third, the amp offers two switch selectable gain ranges, which makes it easy to adapt to ‘phones of widely varying sensitivity ratings. Fourth, as mentioned above, there’s the sound, which tends to show most ‘phones in a very positive, flattering light.
Why you might look further: Much though we like the Rx Mk2, we can think of two reasons you might not choose it. The first is price: at $449, the Rx Mk2II isn’t cheap, but then truly good stuff almost never is. The second is the fact that the Rx Mk2 is purely an amplifier, whereas your particular needs might be better served by a combination amp/DAC.
CEntrance DACport ($399.95)
What it is: CEntrance’s DACport is a bit of an iconoclast in that it is a tiny, roughly cylinder-shaped, and entirely USB-powered combination high-resolution USB DAC (96kHz/24-bit capable) and—get this—pure class A-powered headphone amplifier. As such, the DACport is offered as a potentially ideal companion product for listeners who prefer to use laptop computers (or other devices with USB interfaces) as their source components of choice.
Why you might choose it: when you get right down to it, one of the main reasons to buy the DACport is to enjoy the cumulative benefits of the many different advanced technologies that have gone into its design. CEntrance, as it happens, is a high-powered technology consulting company whose clientele includes makers of DACs for the high-end audio and pro-sound (think, recording studio) communities, as well as a large number of manufacturers of chip-level DAC devices. All of these clients have turned to CEntrance to tap the firm’s expertise in the areas of USB interface design, device driver design, and jitter reduction technologies—expertise that has most definitely found its way into the deceptively simple-looking DACport.
Viewed as a DAC, the DACport sounds highly detailed, focused and revealing—more so than many standalone DACs that cost as much or more than the DACport does. In terms of extension, definition, and refinement, the DACport simply sounds more expensive than it is. Note, too, that the DACport comes with self-installing plug-and-play drivers that makes installation in either PC or Mac-based systems a snap.
Viewed as a headphone amp, the DACport is also astonishingly capable, though like almost any class A amplifier it needs to be fully warmed up in order to sound its best. Once warm-up is complete, however, the tiny DACport sound great and can drive all but the very most power-hungry full-size ‘phones without a hitch. The only sonic drawback we could identify was that the DACport’s mid- and low-bass could sound just slightly lightly balanced relative to some other headphone amp/DACs we’ve tried (which may reflect the fact that there is only so much power you can possibly pull from a USB port).
Why you might look further: Wonderful though the DACport can be in its intended use context, we can think of several reasons you might look elsewhere. The first reason is that—for obvious reasons—the DACport can only be used with devices capable of providing power through USB ports (meaning you cannot, of course, run the DACport directly from an iPod). Second, you may or may not find the bass balance of the DACport to your liking (it works great with many headphones, but not all). Third, you may need or want a bit more power output than the DACport has to offer. Still, in terms of sheer sonic sophistication, the DACport plays way above its pay grade, which is a huge part of its appeal.
NuForce Icon Mobile ($79)
Playback Issue 19
What it is: An almost ridiculously affordable combination headphone amplifier/DAC that offers a substantial step up in sound quality from box-stock iPods, etc.
Why you might choose it: while the Icon Mobile is actually one of NuForce’s oldest products, it enjoys a certain evergreen appeal—largely because the product concept was so very clever to begin with, while the price (a mere $79) is also right. Here’s what $79 buys you: a class D headphone amplifier with switch–selectable gain settings, plus a USB 2.0 DAC that can support up to 44.1kHz/16-bit or 48kHz/16-bit audio files, all fit within an enclosure that is only slightly larger than a typical business card case. Seriously, the Icon Mobile is ultra-compact, which is but one of the reasons for its enduring popularity.
Sonically, this little amp offers good extension at both frequency extremes with what I described as “taut, well-defined bass and an impressive ability to resolve very fine, low-level midrange and treble details.” If there is any drawback, here, it might be that the amp tends to exhibit a touch of midrange/lower treble forwardness, though this can be mitigated somewhat by giving the amp plenty of run-in time, which helps smooth its sound. Happily, the little Icon Mobile has enough grunt to power just about any earphone and most full-size headphones (though it probably wouldn’t be the best choice for driving certain power-hungry top-tier models).
Why you might look further: If you’re willing to spend more and to accept units with slightly larger enclosures, you can find amp/DACs that offer even better sound and DACs that can handle high-resolution (e.g., 96kHz/24-bit) audio data files. But judged on a “bang-for-the-buck” basis, the Icon Mobile is very tough to beat.
Qables iCube V1 Headphone Amp ($549) and V2 Amp/DAC ($699)
What they are: From the Dutch firm Qables come two closely-related sibling products—the V1 portable headphone amplifier and V2 portable amp/DAC.
Why you might choose them: Let me start by mentioning an intangible, which is apparent or perceived build quality. If you run your fingers over the casework of the V1 or V2, or simply study how they are put together, you may come to feel—as I do—that they exhibit something of the vibe of an old-school German camera (think vintage Leica, for example). Whenever you interact with these Qables products, you just can’t help thinking, “Man, these are really nicely made.” The even better news is that the fine exterior look and feel of the components is reflective of the sonic goodness within.
Let’s start with the V1 amp. The V1 is a class D amplifier that embodies all of the expected benefits of class D technology (tautness, control, definition, good extension at the frequency extremes), plus something more: namely, what I described in my Playback review as “a robust, hearty, and full-bodied quality” that class D amps often are not able to provide. It’s that quality of providing everything you expect plus that elusive “something more” that makes this amp so special.
The V2, which is slightly larger than the V1 amp, basically combines the V1’s amplifier circuit with a USB DAC that can support up to 48kHz/16-bit audio data files (sorry, no support for higher res files). On the one hand, the V2 DAC, which is voiced fairly similarly to the V1 amplifier, adds an extra performance dimension to the product, and manages to sound better than some competing higher-res DACs we’ve heard in this price class. But, a small potential drawback is that the V2 DAC tends to impart a faint trace of treble “dryness” that isn’t particularly objectionable, but that undercuts realism to a degree. In truth, the V1 amp also shows very faint traces of this same quality of dryness, though the DAC makes them more apparent than the amp, alone, does.
Why you might look further: Both Units are relatively expensive, which may prove a deal-breaker for some buyers. On the whole, the V1 is a very fine amp and perhaps the more uncompromised of the two products, while the V2 amp/DAC is quite good in its own right, but arguably less of a slam-dunk choice than the V1 is.