HiFiMAN EF-6 Headphone Amplifier
Editor's Note: Again I am so very pleased to welcome another new contributor to InnerFidelity's growing cadre of writers. Skylab is a long time member of Head-Fi (profile here) and has contributed numerous laudable gear reviews there. He'll be focussing his efforts here at InnerFidelity primarily on headphone amp reviews. I can't tell you how pleasing it is to find myself feeling more and more surrounded by a talented team of qualified reviewers. I'm stoked ... and humbled. I feel like I'm going to have to step up my game to keep up with these guys. Okay, I'll shut up now and let you get on with Skylab's review. Welcome aboard, mate!
The HiFiMAN EF-6 ($1599)
My first review for InnerFidelity, after having done many dozens of amplifier reviews on Head-Fi.org, did pose something of a challenge. The EF6 was designed to provide a partnering amplifier for the company's HE-6 planar magnetic headphones. The challenge was to write about the EF-6 and not about the HE-6. The HE-6 (my post on Head-Fi about the HE-6 is here) has been a difficult headphone for many people to get their arms around, and I believe the primary reason for that is their very demanding nature---they require far more amplifier power to sound good than just about any other modern-day headphone made. This is largely due to a quite low efficiency (published at 83.5 db but with no qualifiers, which makes the figure pretty well useless).
I initially thought that what people were saying about amping the HE-6 was overblown---until I tried them with a VERY powerful vintage stereo receiver, the Pioneer SX-1980 (which delivers about 27 wpc into the 50 ohm impedance of the HE-6 from its headphone out)---and this was for sure the best I had ever heard the HE-6 sound, and remains my reference to this day. (For those unfamiliar, the SX-1980 was Pioneer's flagship stereo receiver in the late 1970's, sold for $2,500 back then, and often fetches more than that today on the used market.) So I became a believer that the HE-6 need a lot of good clean power to really shine.
It's not as though HiFiMan doesn't know this---their original demo amp for the HE-6 was a Threshold power amplifier, driving the HE-6 from its speaker outputs. And this is how many people amp the HE-6 today---from the speaker taps of a stereo amp which is NOT envisioned as a headphone amp.
Slowly, however, as the HE-6 gathered a large following as a very top tier headphone (which it absolutely deserves in my opinion), "dedicated" headphone amps for it started to emerge. More accurately, these amps were designed to meet market demand for use with all of the relatively power-hungry planar magnetic headphones that have been gaining popularity, primarily from HiFiMan and Audeze. The EF-6 is HiFiMan's offering in this segment, which currently includes amps ranging in price from the Schiit Audio Lyr at $450 to the Ray Samuels Audio Dark Star at $4,000. Mercifully, the EF-6 is slightly more toward the affordable end than the Dark Star (which I thought did an excellent job with the HE-6), at $1,599.
I reviewed the EF-6 driving both the HE-6, and the Audeze LCD-3. I drive them from the balanced out of the EF-6, which offers 4-pin balanced and standard 1/4" headphone jack unbalanced outputs. Note that only unbalanced inputs are provided, but there are three switchable inputs two on RCA's around back and one 1/8" stereo mini on the front---a feature I like. The amp appears well made, looks nice but not exotic (which is also my preference), and is pretty heavy, weighing almost 25 pounds.
Source for the review was the Red Wine Audio Isabella Pro DAC, as included in the "Audeze Edition" DAC/Amp. I compared the EF-6 to the RWA driving the LCD-3, and to the Pioneer driving the HE-6.
Turn the page, and we'll have a listen ...