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Inside the EF5 head unit sits the below mother board slipped into the usual lateral rails of the aluminum chassis extrusion. Atop it piggybacks the golden heatsink board on two 24-pin connectors. This board was already visible through the plexi top as were the adjacent two black heat sinks.

The sugar-cube sized volume control isn't fixed to the board but only mounts to the face plate with its threaded collar. The PSU unit houses one toroidal power transformer whose diameter maximizes the enclosure's width and height.

Once the secondary board below is pulled off with whatever 6-legged devices are mounted beneath its anodized heat sinks (apparently there are four per square), further capacitors and some voltage regulators become visible. A single National Semiconductor LM675T op amp in a 5-pin TO-220 package mounts to its own chimney heat sink. This device can deliver a max current of 3A and work on supply voltages as high as 60V. Its function in this circuit isn't as output device however—the socketed 8-legged OPA275 together with a discrete parts circuit is—but as floating ground. The 12AU7 produces voltage gain as a cascode amplifier in the first stage.

Right in front of the plexi window is a slider switch for hi/lo gain which requires a screw driver blade or similar to move. For the HE-5LE, high is the recommended setting.

Context: The initial review system eliminated the matching EF5 amp by design and consisted of a 1TB iMac loaded mostly with CDs imported as AIFF files but also some AAC files downloaded from the iTunes store. Those files streamed via LaCie FireWire 800 to a Weiss DAC2. That converter forwarded analog signal to the Woo Audio Model 5 outfitted with Shuguang Black Treasure 300B power triodes, Synergy Hifi 6SN7 drivers and very large EML 5U4G rectifiers.

For direct competition, I had the Sennheiser HD800 and AKG K-702 both rewired with ALO Audio cryo braids; Grado PS-1000s and Audio-Technica W5000.

The HE-5LE connected to the amp's 4-pin Neutrik K-1000 output—wiring diagram above—all others to the standard 6.3mm socket of course. Switching inputs made for easy comparisons.

HE-5LE sound - general: The pronounced initial sibilance wore off after a week of hard labor. Each of these HifiMan headphone reputedly undergoes 24 hours of pre-shipping action. Considering subsequent sonic changes, that's likely for final QC. It's not complete break-in. Another 150 hours seem mandatory. What remained was an admirably even balance with unexpected punch and heft down low, tonal richness and distinct smoothness. However, viewed against the type of presentation a cured pair of HD800 will produce (cured refers to a proper replacement wire harness), the planars conveyed a prevailing sense of mist, veiling or darkness. This wasn't particular to a frequency band or zone. It was wholesale and intrinsic. As such, it didn't betray itself per se as much. Without a superior reference, you might not identify it properly, adapt quickly enough or play these cans quite loud to overcome what I considered some resistance.

Because the entire concept of planar diaphragms hinges on reduced mass and faster reflexes, this was unexpected. We instinctively equate foil drivers with heightened resolution. It's exactly why 'lighter than air' ribbon tweeters have so many admirers. Quite naturally I had expected dazzling speed and finessed resolving power as though these were Staxes. Instead they behaved like I experience many conventional 85dB speakers when compared to a rarer 98dB variant. The less efficient speakers tend to be less dynamic and immediate. They require higher levels to wake up. The HE-5LE did likewise come on song more at higher levels but the gentler SPLs I favor felt restrained and lazy though very pretty. An important question to ask is of course, compared to what? We'll play musical chairs with the above competitors to answer that. One possible concern of poor amplifier drive was laid to rest by the Woo. It delivers a claimed 10 watts into 8-ohm speakers. As a nearly purely resistive load, the HE-5LE is actually not beyond battery-powered pocket amps as my review of the HeadAmp Pico chronicled. There it will primarily be a function of enough gain. iPod-type sources don't put out the hifi-standard 2 volts. That likely makes the gain of such mini systems insufficient for the HE-5LE. But not always.

Norbert Lehmann listening to the HE-5LE during HighEnd Munich 2010