Background: In our listening tests, we evaluated the EF-6 with ancillary components as outlined below.
The Sound: The sound of the HiFiMAN EF-6 bespeaks seemingly limitless reserves of power—even when driving HiFiMAN’s own HE-6 headphones—yet the amp in no way sounds slow, sluggish, or “muscle-bound.” This, I think, is one of the most appealing aspects of the amplifier; it offers locomotive-like power and drive capabilities, but with skateboard-like agility.
What does “power” sound like in action? In the case of the EF-6, the sound of power could be described as the cumulative effect of a hundred small sonic cues that tell you this amplifier is unfazed by difficult loads and is never working very hard—no matter how outlandish or extreme the dynamic challenges your music might present. Through the EF-6, vigorous transient sounds seem to hit a little harder without so much as a trace of apparent compression, while potent crescendos seem to expand in scale and impact without any discernible amplifier-induced limitations. Over time, then, you come to trust the fact that with the EF-6 in your signal path, the amplifier will never, ever again be the limiting factor in reproduction of musical dynamics. This is one respect in which the EF-6 deserves to be called a world-class amp.
The amp is also very fast sounding and well defined, although I would not say that either speed or definition represents the primary defining quality of HiFiMAN’s flagship amp. Rather, those characteristics seem to be byproducts of a very well thought out Class A, MOSFET-powered circuit that focuses on offering a rich, natural presentation of the recordings at hand (complete with appropriate natural warmth)—this in contrast to amps that focus on providing a squeaky-clean, pluperfect, blueprint-like, and almost clinical rendition of the sound. Those who prefer amps that wear clarity and precision on their sleeves like audiophile badges of honor might initially find that the EF-6 seems disarmingly easygoing, because it does have a certain relaxed and yet hearty-sounding quality. Listen more closely, though, and you’ll find that all—or nearly all—of the expected audiophile traits are present and accounted for. Transient speed, delicacy and nuance, and resolution of fine low-level details are all available to you through the EF-6, but they aren’t necessarily the main event; instead, musical naturalism is the main event, which suits us just fine.
Some high-end amps seem to trade in sonic revelations, as if their main goal is to expose certain aspects of your favorite music in ways you’ve never been able to hear clearly before. But when listening through the EF-6, which is plenty revelatory in its way, the overarching effect is of discovering that your music has suddenly become richer, more substantial, and above all more accessible than ever before. By helping to remove sources of constriction (dynamic and otherwise), the EF-6 let’s music flow more freely and to become (with apologies to U.S. Army for borrowing its slogan) all that it can be. This, to our way of thinking, is one of the most compelling reasons to consider owning the EF-6.
Are there drawbacks? There are a few. In the global scheme of things, the EE-6 falls a couple of percentage points behind the Cavalli Audio Liquid Fire amplifier in terms of subtlety, low-level resolution, and overarching sonic refinement. Tempering that remark, however, are two factors: first, the EF-6 is if anything even more powerful than the Cavalli amp, and second, the EF-6 is less than half the price of the Liquid Fire.
Similarly, the EF-6 is perhaps not quite as accomplished as Burson Audio’s Soloist amplifier in terms of capturing the more three-dimensional aspects of music. The Burson conveys the timbres and textures of individual voices and instruments with an almost uncanny, sculptural solidity—a quality that seems all the more impressive when you consider that the Burson is priced several hundred dollars lower than the EF6. Excellent though it is, the EF-6 is not without serious and worthy competitors at both higher and lower price points.
Finally, some amps—and I am thinking of the Burson Soloist once again—offer three-level master gain settings rather than the EF-6’s two-level settings. As I noted above, the EF-6’s high gain setting is ideal for driving HiFiMAN HE-6 headphones and other extremely power hungry, low-sensitivity ‘phones. The EF-6’s lower gain setting, in turn, works better with the vast majority of headphones that offer moderate sensitivity and are moderately easy to drive. Where the situation can become tricky, though, is when trying to use the EF-6 to drive extremely high-sensitivity earphones or headphones (for example, most custom-fit in-ear monitors).