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German importer Jan Sieveking: "I have heard the HE-6 sample. You can basically expect the sound of the HE-5 LE with tighter and more controlled bass and additional treble resolution. I remember that you preferred the sound of the HE-5 LE with less damping material. Thus I am sure you will appreciate the difference. What I liked best is that it does present music as a whole and not as a combination of bass, mids and highs as I feel most headphones do. In a way the homogenous sound of a Magnepan speaker with its relaxed presentation is also in these headphones. I am not sure this will appeal to everyone though. Some people prefer the way a Sennheiser HD800 sounds. I am not among them but that does not mean it's no good. I also have a feeling that break-in takes somewhat longer than with the HE-5 LE."


These were also my observations. But first, what type of amp would it take to properly drive the HE-6?

Using a docked iPod as a 1V-max source you probably relate to, I could and mostly did crank the Burson Audio HA160D, Schiit Valhalla and Meier Audio Concerto to the max. This gave me perfectly satisfactory SPLs on most music but on some I was still left wanting. For context, any of these amps fully open would clip my ears with the competing Audez'e ortho. That can actually run straight off the iPod and get nearly loud enough. Sonically and on the HE-6, the Burson led this parade followed closely by the Schiit. Both sounded very good. The Burson was ballsier and denser and would be my first choice but the leaner and softer Schiit wasn't far behind. The Meier however was a distant third. In this context it was clearly outclassed.


The petite $449 NuForce HDP surprised again by being perfectly copasetic if a bit harder edged than the two class A champs. HifiMan's own EF5 would probably have been quite ideal but my loaner had strangely given up the ghost since its review. While on probabilities still, Firestone Audio's Libby—long since boxed up again after her assignment—should slam. On regular headphones I could never get her much past 9:00 or 10:00. The Antelope Zodiac+ wasn't powerful enough.

Next in my arsenal of head amps was Woo Audio's mighty Model 5 and Trafomatic's Head One. These are triode amps, one with big 300B, the other with small 6S45P. The Head One had insufficient gain. The Woo off its balanced headphone output had enough but its output impedance seemed ill-matched because the lower registers got clearly too loose and bloomy/boomy.

While the Peachtree Audio iDecco could be maxed out too and additionally sounded a bit soft and indistinct on this particular load, the Aura Note Premier by April Audio went louder than I could tolerate and was properly robust to boot. Rummaging through my odd-ends box next, I dug up an abandoned AKG K-1000 aftermarket speaker-level leash from many years ago. That went to the outputs of the overachieving 25wpc Dayens Ampino (€220 + shipping from Serbia when I reviewed it in April of last year). At about 10:00 on its dial and still fed from the same Sieben Technology iPod dock, I had glorious liftoff and screaming room to spare. Converting the Serbian into Campino—ampino for cans—might just be the most cost-effective and also balanced-drive HE-6 solution. That's if one's source output voltage doesn't reach far enough with the $249 Schiit Asgard (the forthcoming $449 Schiit Lyr will be a tube hybrid that puts out 6 watts into a 50-ohm load to be tailor-made for orthos like the HE-6). With my 5.5V-max Weiss DAC2 for example, any of the above amps on the HifiMan would blow me into the weeds. An iPod's output stage is simply a lot weaker. I only used the iPod as an example which I assume most readers can relate to from direct experience to put the HE-6's drive requirements into context.


That said, Campino's benefits on general grunt plus bass rumble and slam in particular were impossible to argue with*. This combo was so good that much of this assignment went - um, camping. Before we get all carried away by silliness and jollification, let's stress the important point behind this particular exercise. Real power is required to get the HE-6 to fully strut its stuff. Power goes beyond the basic sound pressure considerations of playing loud enough and into all the elements we usually associate with control, damping and drive. With a low Zout amp like the transistorized Ampino, a 50-ohm load will seriously ratchet up the operative damping factor. So think of the HE-6 as the 'phone from krell and you have the proper idea.
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* I also tried Campino with its volume pot bypassed, run off the Aura Note Premier's pre-outs whilst spinning CDs. After all, the Ampino is an amp with passive pot. It's not a true integrated with an active linestage. Into these headphones and sans signal, the Serbian amp at full gain was dead quiet. Considering doing something like this really is no joke. It's a very serious and seriously affordable solution. You simply have to provide the proper 4-pin XLR to bananas/spades leash.

Because the leather-sheathed headband is metal, it can be bent into a different shape and stay that way to accommodate smaller heads. The above drawing shows how.
  
Concluding this preliminary heat to see which of my amps would even make it to the finals, I had the Dayens Ampino to stand in for a speaker amp converted to can drive**; and for the dedicated headfi stuff the Burson Audio HA160D and Schiit Asgard which would run off the iDecco as iPod DAC for additional headroom. That sequence also reflects ultimate performance. With that sorted, we can enter the final stretch. Checkered flags up ahead.
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** Don't assume any speaker amp is fair game. Some won't like a 50-ohm load and either distort, get noisy or oscillate. Speaker amps aren't really made for such impedances and some older tube amps could really protest. That renders predictions impossible. Shy of having an amp to experiment with, it's probably best to directly consult the makers for prior assurances. Here is what the HE-4 owner's manual says on the subject: "It is theoretically possible to connect your HifiMan HE-4 directly to the speaker output terminals of your home amplifier. However, the amplifier in use may not offer more than 70 watts of output power and must be stable into the higher than typical load of the headphone. Please make sure to verify both with the manufacturer of your amp before attempting a connection. Caution: Overload due to too high voltage or technical defects caused inside the amplifier by attempting this connection are not covered by warranty. This mode of operation is not recommended."


Well, you'd expect them to say that. It's self protection from warranty abuses when someone leashes their headphones to a 200wpc Levinson amp and "has an accident". That said, I fail to see how you could possibly blow up the HE-6 in speaker-amp mode if you wear them before you turn up the volume.
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