I first learned of the Chinese headphone specialist HiFiMAN through my interest in the firm’s cool planar magnetic headphones, including the HE-5LE, the HE-6, and the new HE-500. Very early on, though, I realized those planar magnetic ‘phones were quite power hungry and therefore could not be driven properly by just any old headphone amplifier.
What was needed in order to tap the performance potential of the planar magnetic headphones was a headphone amp with plenty of gain and very robust power output capabilities. Naturally, HiFiMAN was already fully aware of this requirement, and so they graciously loaned me a sample of their EF5 hybrid tube/solid-state headphone amp ($499) as a way of facilitating my listening tests.
I soon discovered the EF5 not only worked well with HiFiMAN headphones, but also with virtually any good headphones—especially with those generally regarded as comparatively difficult loads to drive. Recognizing that many Playback readers might find it interesting to learn about a mid-priced amp that has sufficient moxie to drive higher-end headphones with grace and aplomb, I decided to prepare this review of the EF5.
- The EF5 is an attractive, compact, minimalist headphone amplifier that is based on two chassis—one chassis housing a HiFiMAN DY-1 power supply module, and the other housing the main audio circuitry and user controls. The footprints and faceplate designs of the two chassis match one another, so you can place the audio section on top of or alongside the power supply module, to suit your preference.
- The EF5 is a hybrid tube/solid-state design based upon a 12AU7 tube and an OP275 opamp.
- Maximum output for the EF5 is specified in term of volts, not watts, with the figure of merit being a whopping 15V at 32 Ohms.
- The audio section of the EF5 features a power supply input and two RCA jack audio inputs on the rear panel, with a volume control, on/off switch, and ¼-inch headphone jack on the front panel. The top of the audio section chassis features a clear Plexiglas viewing window through which you can see the main circuit board, plus a two-layer Plexiglas heat shield for the top-mounted 12AU7 tube.
- In a perhaps too-subtle-for-its-own-good detail touch, the amp is set up so that, when fully warmed up and ready to play, a concealed blue pilot light illuminates, casting a ghostly blue glow over the audio circuit board. This is actually a pretty tasteful visual feature if you like to listen under low lighting conditions, but if you place the amp under bright lights they will almost completely wash out the glow from the pilot light, making it difficult to tell at a glance if the amp is on (hint: watch for the subtle orange glow of the tube filaments).
- Recently, an improved CE-certified version of the EF5 has been released, and is now the only version of the amplifier being sold in the US. Among other changes incorporated in the CE-spec EF5 are a new volume control, which enables users to bring up the gain a bit more gradually than was the case with the original EF5, and an upgraded Fullmusic 12AU7 tube, which now comes as standard.
- Note, please, that the Playback review sample was manufactured slightly before the CE-certified version became available, so there is every chance that the EF5 you might buy will sound even better than our sample did and does.
For this review we did much of our listening through HiFiMAN’s own HE-5LE and HE-6 headphones, but also with a mix of other models including Beyerdynamic T1 Teslas and DT-990 Pros, Sennheiser HD800’s, and Shure SRH840’s.
Comparison amplifiers included the Apex Peak /Volcano, the Burson HA-160, the Cavalli Liquid Fire, the CEntrance DACport Mini and DAC Mini, the Furutech/Alpha Design Labs GT40, the Peachtree iDecco, the NuForce Icon HDP.
The EF5 creates three indelible impressions on most listeners. First, it sounds very highly detailed relative to other amps at or perhaps slightly below its price class. Second, it offers truly terrific bass punch and definition. Third, it offers powerful, lively, and highly expressive dynamics, along with all the gain any sane listener will ever need, no matter how difficult to drive or power-hungry his or her headphones might be. Let me expand on each of these points.
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.
To appreciate how good the EF5’s bass really is, let me encourage listeners to listen to “Nothin’ To Do Blues” all the way through to the end, and to drink in Brian Bromberg’s amazing, virtuoso bass solo. The solo doesn’t venture extremely low (that is, all the way down to the bottom octave), but from the mid-bass region on up it will give any system a thorough workout. Bromberg shows off a dizzying array of skills and techniques, and plays some of his lines at what could only be called “warp speed.” The amazing part is that the EF5 tracks cleanly through the sole from end to end, never faltering, never missing a subtle shift in textural or dynamic emphases, and never, ever allowing notes to become blurred or to blend together. At a couple of points, Bromberg plays some sliding double stopped notes, causing the bass to at once seem to “sing” and to “snarl” (a trickier combination to reproduce than you might think), and the EF5 follows along with gusto, every step of the way.
But if you want to hear the EF5 go low, and I mean really low, jump forward to another track from Jazz Kaleidoscope: namely, “O Vazio”, as performed by the Jim Brock Ensemble. The song opens with the plunging sound of low-pitched percussion instruments, whose deep, dark voices are contrasted against delicate high-pitched chimes, gongs, and cymbals. But at about 30 seconds into the track, you’ll hear the mind-blowingly subterranean sound of a large and ultra low-pitched drum arrive. What’s impressive through all of this is not just the ease with which the EF5 goes way down low (tapping the full bass potential of headphones as few other amps can do), but the impressive pitch definition it maintains while doing so. You can easily hear, for example, the subtle modulations of even the lowest notes. Good work, HiFiMAN.
Finally, to enjoy the EF5’s hearty and expressive dynamics, let me recommend the track “Back to the Blues” from Hadden Sayer’s album Hard Dollar [Blue Corn Music], where Sayer’s delivers a lovely and deeply evocative blues duet with Ruthie Foster. Several aspects of the track are revealing. First, note how the EF5 reveals (but does not exaggerate) the very subtle inflections and points of emphasis that Sayers and Foster’s vocal lines both express—especially at moments where emphasis shifts from one singer to the other. Next, carefully note the sheer variety of electric guitar sounds captured on the track (one of the strengths of this album). You’ll hearing everything from solo lines where the guitar’s voice seems to soar and almost to cry, on through tot abruptly yet delicately strummed chords used to provide split-second rhythmic accents—and everything in between. One of the most impressive things to hear is how the EF5 captures the momentarily explosive sounds of the guitar tearing into a note, but then equally quickly gathering itself back up and pulling back the dynamic reins to maintain control. The EF5 teaches you that it is just as important to handle decrescendos well as it is to capture moments of explosive power. Once you listen to “Back to the Blues” through your favorite ‘phones as powered by the EF5, try going back to play the same track through a similarly priced competing amp. My educated guess is that—in most, though not all cases—the competitor will sound noticeably less energetic and expressive than the EF5 does.
Consider this headphone amp if: you want an amplifier with a good measure of resolution, a lively and dynamically expressive sound, and available levels of gain that can easily handle most hard-to-drive ‘phones. We can’t overstate the benefits of that last point so let us reiterate: the EF5 easily and gracefully drives ‘phones that can cause many mid-priced headphone amps to audibly “run out of steam.” Bluntly, this amp comfortably goes where many others fear to tread.
Look elsewhere if: you use very high-sensitivity phones, in which case you may find the taper of the EF5’s volume control not entirely to your liking. But note, the recently released, CE-certified version of the EF5 is said to provide a volume control that allows gain to ramp up a bit more gradually). Also look further if you want to push for ultra-high levels of resolution (albeit at an inevitably higher price point).
Ratings (compared to similarly-priced headphone amps):
- Tonal Balance: 9.5
- Clarity: 9.5
- Dynamics: 10
- Flexibility: 8 (one input only)
- Value: 10
The EF5 headphone amp makes a great choice for those who want to explore the merits of potentially hard-to-drive top-tier headphones, yet without spending an arm and a leg on amplification. While some higher-priced solutions do offer an extra smidgeon of resolution and finesse, we feel the EF5 is one of the best amps available at its $499 price point.
Significantly, the EF5 is arguably the least expensive amp we have found that can drive adequately HiFiMAN’s fabulous (but admittedly power hungry) planar magnetic headphones, and can do so without breaking a sweat—or your wallet.
In sum, the EF5 is a simple and affordable amp that offers very good levels of sonic sophistication and that is absolutely fearless in tackling tough loads, thus enabling even finicky high-end ‘phones to “sing” and to show off most of their sonic potential.
SPECS & PRICING
HiFiMAN EF5 Hybrid Tube/Solid-State Headphone Amplifier
Tube: 12AU7 (new CE-certified versions of the EF5 are supplied with upgraded Fullmusic 12AU7 tube)
Frequency Response: 20Hz -30 kHz
THD+Noise: <0.2% maximum
Analog Inputs: one stereo analog (via RCA jacks)
Analog Outputs: ¼-inch phone jack
Input Impedance: 50 kOhm
Headphone Output Impedance: 2 Ohm – 2 kOhm headphones
Headphone output strength: up to 15V @ 32 Ohms
Dimensions (H x W x D):
- Main amplifier (with tube installed): 3” x 4.33” x 8.5”
- DY-1 power supply module: 1.97” x 4.33” x 8.5”
Weight: 5 lbs.
Warranty: One year, parts and labor