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"Hello Wojtek! Tell me, have you really listened to this particular setup (he asked about the Devialet D-Premier AIR driving the Acuhorn Superleggera Giovane85 high-efficiency widebander) or was your recommendation based only on assumptions from your experience with the Devialet two months prior to the Acuhorn review? The reason I ask is because usually ultra-light drivers like the one used in these speakers hate to work with amps of very high damping factors. Actually in such a setup bass rolls off much earlier than it would with tube amps that have high output impedance. You have noticed that yourself when you tried these speakers with your Soulution amp. If you wrote about the Devialet based on actual experience I would have to reconsider the whole thing but if you were just guessing … well then you made a huge mistake recommending this setup. It so happens that this particular problem was one reason for the FirstWatt F1 amplifier, a current source and not voltage amplifier. It sports a high output impedance (around 50Ω) which makes it incompatible with most loudspeakers except for those with wide-range drivers which feature quite high damping themselves. When you hook them up with an amp like the F1 you can expect more bass extension and a less restricted more open sound. Knowing that Devialet has very low output impedance I can't see how this particular setup could really work. ATB." [This type of inquiry is stock MO for reviews I edit or syndicate. Here I was preparing the Acuhorn review and suspected a possible mistake to ask before publishing it blindly. My suspicion proved correct since Wojciech had omitted an important detail which would have explained that this single-driver speaker otherwise lacked bass with the Devialet which could only be fixed with a cheat – Ed.]

The first thing was yes, I had listened to this setup. Admittedly in 'flat' mode there hadn't been sufficient bass. But Devialet is not your regular amp. It has digital tone controls. So I simply added some extra bass and voilà. The real point of Srajan's email was that not everything in audio is as it appears to be. Finding a proper match of amplifier and speakers for any given room isn't as easy as it might seem on paper. By contrast headphones would seem to be perfect loads. They usually have higher or very high impedance, there is almost always just one driver which usually omits crossovers as they don't need any. Usually their voltage sensitivity is high too so 1 watt is all they need to sing. And you don't have to worry about room acoustics. Piece of cake then. Until one listens to some high-quality headphone amp with various cans.

Now one realizes that different voice coils, diaphragms, enclosure loading etc. make it impossible again to predict how a particular pair of cans will work with a given amp. I know of only two headphone amp which clearly show the true character of each pair of headphone whilst hiding their own character pretty well. But even these two aren't perfectly transparent. They are the Leben CS-300 XS [custom version] and the SPL Phonitor 2730. The former is a tube device, the latter transistor. Both apply a high voltage to their output devices. The EPA-007 Phasemation now became the third in this group which should offer high performance with any given pair of headphones. Of course some will still sound better, some a bit worse but they will always offer a similar tonal balance—which mostly depends on the headphone—and very extended frequency response.

I had opportunity to listen to 8 different headphones with this Japanese amplifier and the best results, no surprise, came from two reference pairs: Sennheiser's HD800 and HifiMan's HE-6 as two real challengers that had sounded brilliant with just a very few amps before. Let's start with the HE-6. It's the top planarmagnetic from this Sino/US company and a true amp challenge due to low impedance and very low efficiency. Despite the latter, high power alone can often deliver a pitched aggressive sound. Not with the Phasemation. Now the HE-6 delivered very transparent sound with great resolution to sound exactly how planar magnetics should but with also very rich consistent body and good 3D imaging. Using this setup I listened for the first time to the newest Depeche Mode album's Japanese issue. This allowed me to call off my prior dark vision of this album when I'd reviewed the first single Heaven. The music on DM's album is mostly created with analogue synthesizers and guitars. It translates into a particular richness, sonic depth and exceptionally broad frequency response. The Japanese amplifier delivered it all without the smallest issue to allow me deep insight into the recordings. This confirmed for example how heavily compressed the Heaven cut really was.

The sonic key feature of the Japanese amp was transparency. With the Sennheiser HD800 and compared directly to the Leben, the latter seemed a bit dull. It's not entirely true but made me wonder. The solid-state EPA-007 had superior treble resolution. After changing from the valved CS-300 XS I for some time thought that the Phasemation emphasized the treble a bit. The sound opened up and I heard more detail, more subtleties as though it had become easier to see details of decisions that had been made in the recording and mastering studios. It was most obvious with older recordings, preferably mono and with a lot of tape hiss. Nobody listens to tape hiss of course but it's still part of a recording and thus has merit by showing off any irregularities in the response, perhaps more easily so than with the music itself. The EP-007 delivered perfectly flat response with bit more tape hiss amplitude than my reference amplifier.