HiFiMAN EF5 Headphone Amplifier (Playback 45)

A Great Solution for Hard-to-Drive 'Phones

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.

FEATURES

• 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.

ANCILLARY EQUIPMENT

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.

SONIC CHARACTER

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.