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Reviewer: Srajan Ebaen
Financial Interests: click here
Source: 27" iMac (3.4GHz quad-core IntelCore i7, 16GB 1.333MHz RAM, 2TB hard disc, 256GB SSD drive, ADM Radeon HD 6970M with 2GB of GDDR5 memory); PureMusic 1.86; Amarra 2.3; Audirvana Plus 1.3.9 in direct/integer mode; April Music Eximus DP1; Esoteric/APL Hifi UX1/NWO-M; Audiophilleo 2
Preamp/Integrated: ModWright LS-100 with Psvane CV-181T tubes, Esoteric C-03, Bent Audio Tap-X
Amplifier: First Watt SIT1 monos, ModWright KWA 100SE
Speakers: Aries Cerat Gladius, Boenicke Audio B10
Cables: Complete loom of Zu Audio Event, Entreq & Ocellia & Vue & Telos USB cables, Stereolab Tombo Trøn BNC/BNC coax
Stands: Artesania Esoteric double-wide 3-tier with optional TT glass shelf,, 2 x ASI HeartSong amp stand
Headphone amps: ModWright LS100, Eximus DP1, Burson Audio HA160DS, Schiit Lyr, Linnenberg Audio u:c:a [on review], Burson Audio Soloist [on review]
Headphones: HifiMan HE-5LE, HE-500, HE-6 (with optional Entreq Konstantin 2010 replacement harness); Sennheiser HD-800, Beyerdynamic T1 and T5p, Audez'e LCD2 all recabled by ALO Audio
Powerline conditioning: 1 x GigaWatt PF2, 1 x Furutech RTP-6
Sundry accessories: Extensive use of Acoustic System Resonators, noise filters and phase inverters
Room size: 5m x 11.5m W x D, 2.6m ceiling with exposed wooden cross beams every 60cm, plaster over brick walls, suspended wood floor with Tatami-type throw rugs. The listening space opens into the second storey via a staircase and the kitchen/dining room are behind the main listening chair. The latter is thus positioned in the middle of this open floor plan without the usual nearby back wall.
Review Component Retail: $1.600

Whenever headfi newbies ask about the best available headphones, their friendly neighborhood bloggers will point at the usual suspects. That would be the best models Sennheiser, Beyerdynamic, AKG, Grado, Denon and Stax make. They'll also mention the LCD-2 or 3 from Audez'e, a recent startup that broke into the top leagues with their very first model. And they'll mention the HE-6 and HE-500 from another less recent startup called HifiMan. If these bloggers are responsible, they'd add to any HE-6 recos a strong demand for power. Due to its inefficiency, this planarmagnetic or orthodynamic headphone is today's AKG K-1000. It wants a few watts into its 50Ω load. A solid fistful might be better. Schiit's $449 tube-hybrid Lyr with 6 watts into its impedance is probably the most affordable amp geared directly at the HE-6 and others of its demanding kind.
Production has eliminated the speaker/headphone toggle and added a clear acrylic cover for the voltage selector
To address their live-it-up appetites and undermine potential HE-6 criticisms fundamentally based on insufficient drive—which critics wouldn't appreciate until faced with an obvious resolution—Fang Bian the HifiMan now has issued the EF6 especially for the 6. It's a chunky 310 x 330 x 105mm brick that weighs a macho 24lb. It's capable of an equally macho 5 watts into 50Ω. Those watts derive from a class A transistor circuit. Its gain is controlled by a hand-made 24-step attenuator. German importer Sieveking Sound who dispatched the loaner warned me. Its actuation was so tight as to warrant a grip as firm as a Harley-Davidson clutch might need a foot stomp. Truly?


There are three line-level inputs with blue LEDs and relay-switched push selectors (2 x RCA on the back, 1 x 3.5mm on the front). There's one pre-out to support preamp duty. A rear-mounted toggle labeled 'gain' selects between 10dB of negative feedback and none. There's also a 120/240V slider secured behind a transparent cover to adapt to international AC voltages. Appearance is basic yet solid. One concession to luxury is the shiny fingerprint-prone black acrylic dress plate. It forms a black-on-black two tone with the standard brushed black aluminum inside its cutout.

Prototype at HighEnd Munich 2011

What does the EF6 lack besides a good name? A built-in DAC. How to connect your laptop or iPod? To the 3.5mm port? You gotta be kidding. Not if you're serious enough to want the EF6 in the first place (particularly with that 4-pin XLR which the casual brigade wouldn't know what to do with*). Those who prefer a one-box solution à la Burson HA-160D/DS or Linnenberg u:c:a. will view this omission a serious deal breaker. Especially because for less coin the Aussie and Teutonic competition has it. Others with already dedicated DACs obviously won't care one wit.
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* Don't expect a balanced circuit. The EF6 is single-ended front to back. The 4-pole connector is but a convenience item for AKG K-1000 and HifiMans. It eliminates the need for a 6.3mm/XLR adaptor.

A potential deal breaker for EF6-as-preamp users could be the lack of remote control. Like team Burson, Fang opted for the sonically superior mechanical resistor-ladder attenuator. To mate that to a stepper motor for RF or IR control gets very clunky. The better solution would be relay-triggered resistors but those tend to emit switching noises. Hence no wand. My reference Eximus DP1 DAC/headfi/preamp lacks one too. At its $3.000 sticker that's arguably a lot more troubling. Clearly the EF6 is far from alone here.

The lateral heatsinks can get quite toasty to the touch if played long enough. The top and front do not.
Still I wish that companies hoping we'd take their headfi amps serious as preamps would add remote. Today's name of the game is integration after all.

Fang Bian at the Sieveking Sound booth of Munich HighEnd 2011
With the amp's mondo power mated to a low step count on the volume, cans quicker on song than the HE-6 might want a level right between two of the current steps. Or burn up useful range too quickly. That's where the gain switch might come in handy even though its means of gain reduction—negative feedback—also affects the output impedance and THD.


Now that all the obvious has been covered, what hides beneath the EF6's burly exterior?
Enlarge!