If you are acclimated to the sound of good headphone amplifiers in, say, the $200 - $300 price class, then your first taste of the EF5 may come as a bit of a revelation. One of the main reasons why this is so is that it simply retrieves and reproduces more low-level sonic information than its lesser brethren can do. So satisfying is the amount of information the EF5 presents that you may never feel the urge to push the envelope further. Still, in the interest of candor, let me point out that if you are willing to step up to the level of an amp such as the Burson HA-160 ($695), or to take things even further than that, you will find—with a bit of judicious shopping—that there are headphone amps that can probe even deeper levels of detail and resolution than the EF5 can.
There is little to fault in the EF5’s overall presentation and tonal balance, but if you listen carefully and through ultra high-resolution headphones (e.g., through HiFiMAN’s flagship HE-6 ‘phones), you’ll discover the EF5 sounds just a hair less refined and less focused the higher you go in the audio spectrum. This is not to suggest that the EF5 sounds “foggy” or diffuse when playing way up high, because that is simply not the case. Rather, it sounds only a touch less refined up top than it does in the midrange or below. By “a touch less refined” I mean only that it exhibits, for example, very faint traces of splashiness on hard, abrupt treble transients, and that treble textures are ever so slightly less fine-grained than their lovely sounding midrange counterparts.
Bass is one of the EF5 greatest strengths, where it offer a truly delightful combination of extension, appropriate weight, transient speed, and sheer punch. When listening to music that rocks or swings in a vigorous way, the EF5 really comes into its own—making many competing amps sound compressed or even anemic by comparison. It’s interesting to note how the low-end superiority of the EF5 plays out under real-world conditions. Sometimes, headphones that tend to sound bright, edgy, or lacking in low-end weight when heard through other amps will miraculously begin to sound properly balanced and less midrange or treble forward once the EF5 is brought into play. Such are the at times mysterious benefits of getting the low-end right, which the EF5 does in spades.
Finally, we come to dynamics, which I regard as the EF5’s pièce de résistance. Stated simply, this little amp does a wonderful job with both small and large-scale dynamic contrasts in the music, and it does so even when pushing decidedly hard-to-drive headphones. It is instructive to listen to some lively or evocative tracks through the EF5, and immediately to play those same tracks through competing, like-priced amps. In almost every case, the EF5 comes across as sounding more expressive and muscular, bringing the energy and emotion in the music to life. By contrast, lesser amps sound almost as if they are running the music through a compressor, so that dynamic contrasts lose their potency and sonic flavor.
It is helpful to bear in mind that HiFiMAN created the EF5 specifically to be able to offer a sensibly priced amp that could power their excellent but admittedly demanding HE-5LE headphones. The two products make a wonderful, synergistic, and reasonably affordable pairing.
To hear the resolving power of the EF5 in action, try listening the wonderfully well-recorded jazz track “Nothin’ To Do Blues” as performed by the Mike Garson Quartet on Reference Recordings Jazz Kaleidoscope [Reference Recordings, HDCD]. Listen carefully as Mike Garson’s piano and Brian Bromberg’s bass jointly state the song’s opening theme and note how, even though the two instruments are largely doubling the same musical line, their voices remain perfectly clear and distinct as heard through the EF5. Note, too, how easy it is to follow the very, very soft and delicate sound of Billy Mintz’ brushes on a snare drum head keeping time in the background. Later, note how you can clearly hear subtle, barely audible vocalizations from ensemble members murmuring words of appreciation or encouragement to one another as the song unfolds. Although some people perceive small sonic details to be trivial or inconsequential elements, I think that—when properly reproduced, as is the case here—low-level details can do an awful lot to pull the listener in and to convey a sense of realism and life in the music. As I mentioned above, the EF5—while not the very most detailed amp available in an absolute sense—does such a good job with low-level detail that I suspect many listener will find themselves fully satisfied by the HiFiMAN and feel no need to reach higher.