As music lovers, headphones have always been a part of our lives. Whether this was for privacy concerns, such as listening to music late at night, or for use when traveling on a short commute or a long trip on an airplane, headphones are our escape and salvation. The Woo Audio WA7d Fireflies 192kHz/32-bit DAC tube headphone amplifier answers the call to duty. For those in the music "industry", whether amateur or profession, many of us have had headphones wrapped around our heads for hours at a time in the recording studio. Headphone amplifiers for my personal use were never part of the equation until about fifteen years ago, when I purchased a set of Sennheiser HD-600 headphones. Before that time the best headphones I ever owned were a set of Grado Lab's inexpensive models purchased when Grado initially got into the headphone business in the very early 1990s. But enough about me. At least for now.
These days' headphone amps are ubiquitous, even for many who don't consider themselves audiophiles are even getting into the game – and who can blame them? A good set of headphones deserves a good headphone amplifier. A great set of headphones deserves a great headphone amplifier, and as we will learn in this review a great headphone amplifier doesn't have to cost an arm and a leg. But I suppose everything is relative, and with the Woo Audio WA7d Fireflies headphone amplifier with 32-bit/192kHz DAC we will also learn that one can enjoy a great headphone amplifier and upgrade it into a superb headphone amplifier at a later date... or from the get go.
The WA7d that Woo Audio sent me for review came with the matched set of the Electro-Harmonix 6C45 tubes with gold-plated contacts. I was also sent the matching WA7tp tube power supply along with a standard power supply for the WA7d for comparison's sake. Plus, my review sample came with the Sovtek "stock" tubes so I could compare the two. Woo Audio was also nice enough to send me their HPS-R aluminum headphone stand finished in black to match the WA7d/WA7tp system. The stand's height is adjustable (11" to 14" high) and is made from aluminum and which makes for quite a nice looking setup. Next to my listening seat is a heavy duty end table where I placed the WA7d/ WA7tp system and the headphone stand with my headphones de jour suspended on its outstretched arm. The stand can be adjustable from 11" to 14" high, and is made from aluminum. With a o.75" thick bass, its rubber feet, and its substantial weight – at about four pounds – it isn't likely to slide off the table or wherever one parks it. Its base is only about six inches in diameter, so rather than one of those dummy-head type headphone stands it should take up less room since the headphones are hanging above the rest of the equipment on the desk or table. Nice.
The faceplate of WA7tp vacuum tube power supply looks practically identical to the WA7d, except what looks like the large volume control on the WA7d it is instead a heavy-duty on/off switch. Beside the absent of headphone outputs, WA7tp tube power supply looks practically identical to WA7d amp. What looks like a volume knob on WA7tp is actually a heavy-duty power ON/OFF button. Woo Audio recommends one use the power ON/OFF button on WA7tp tube power supply for daily use; leaving the main power ON/OFF flip switch on the back of WA7d amp in the ON position unless the system is not in use for an extended period of time (such as when you're on holiday). If one leaves the power to the WA7d in the on position, switching on the WA7tp will switch both units to the on position.
Of course the headphone jacks on the front of the WA7d are absent on the WA7tp, leaving just its sleek front panel. The two tubes used in the WA7tp power supply are a pair of omnipresent 12AU7s, so a tube swap might be hard to resist. For the review I left the Russian tubes in place for most of the review period, but near the end substituted a set of military-grade Sylvanias I had lying about. The sonic benefits were a subtle increase in all that makes a good power supply a good power supply; which was quite audible when using the best headphones I have in- house.
About 95% of the files on my iPod are uncompressed 44.1k/16-bit AIFF ("CD quality") files, so when listening to them there was little difference in the sound of these files when sourced straight from my server or the iPod. Bypassing the DAC of the WA7d and running straight, high-resolution files from my main system through the Auralic Vega I reviewed in July is another story, this had the best sound quality by far, but only because this DAC costs roughly four times as much as the WA7d. I also used the WA7d as an outboard DAC. Since the WA7d has two digital inputs plus an analog input and output, if one doesn't mind switching some cables around every once in a while the WA7d could be used as a killer centerpiece of a very nice desktop system.
Headphones used for this review included the fifteen year old Sennheiser HD600 that I spoke of earlier, recently restored to minty-fresh condition by Sennheiser USA. Most of the time, though, if I really wanted to hear what the Woo Audio gear was made of using the top-of-the-line Grado PS1000 headphones was the way to go. I also had on hand the excellent Oppo PM-1 planar magnetic headphones reviewed in August, and the modest but certainly fine sounding Grado SR80e which is a relatively new upgrade of their affordable yet impressive SR80i.
I'm convinced that vacuum tubes are largely responsible for the excellent sound quality of the WA7d. It is one thing to use a tube amplifier to power a pair of speakers in one's listening room, but since it takes much less power to drive a set of headphones the design of the WA7d will not exacerbate any sonic downsides of using tubes. Although there is no denying, and I can speak of from experience, that there is a certain "magic" that many tube amp fans speak of. Still, those stereotypes of old are sometimes difficult to shake. Some might assume that tube amps reproduce bass-shy, midrange forward, and rolled-off treble music through a pair of speakers. Yes, at one point in time tube amps had these characterizes, especially if matched with the wrong type of speakers. The WA7d is a Class A single-ended tube design, yet one is not going to hear a sound that resembles this at all. Tube amps have come a long way, and a quick glance at the WA7d's specifications is evidence of this.
With the WA7d a headphone aficionado can take advantage of the inherent beauty of the sound of tubes sound without the downsides. Still, there is just enough of that old tube sound to use it to one's advantage. Through the WA7 the midrange was the star of the show – vocals, whether male or female, had a lifelike, reach-out-and-touch presence. Even though the signal is very transparent through the WA7d and does not homogenize the sound of difference recordings, the treble of the WA7d, even when playing files of "vintage" CDs was reproduced with a natural sweetness that is as attractive as the real thing, but without any graininess or sibilance that can ruin a recording. The bass on the other hand is another story. Yes, it is "fatter" sounding than the typical solid-state headphone amplifier, yet through the WA7d it also goes as deep as the recording demands, is very pitch stable, and has enough transient edge to make its definition pleasing to all but the pickiest of listeners.
The "soundstage" rendered by the WA7d is also a pleasure to hear. Of course soundstage is in quotes because the soundfield generated by a set of headphones is nowhere like the soundstage that comes from a properly set-up pair of loudspeakers, and that is why in the ratings section of this review this section is not considered. But the "music-inside-the-skull" sound is often a complaint of many who dislike the headphone experience. My life-long involvement in the art of headphone listening has shown that this is usually the fault of the headphone and the headphone amplifier, and not the fault of the medium. Inexpensive headphones cannot generate sounds that leave the confines of the headphone's earpads, and usually congregate inside one's skull between these two earpads, at best. Listening with a poor headphone amplifier will result in the same effect, and the same thing will happen when listening to headphones with no headphone amp at all. Listening to music with a good (or better) set of headphones, through a good (or better) headphone amplifier will relieve one of these unsettling effects to large degree.
Sure, there are going to be some sounds that are panned to center that still end up sounding like they are geminating from one's cerebral cortex, but one will be surprised when listening to a record recorded in mono, such as the new Beatles In Mono set, that sounds are not confined to a single area even though the program material is just one channel. The amount separation of voices and instruments that occurs is quite amazing through the WA7d. Separation of instruments and voices is a hallmark of a good high-end system, regardless of whether it is coming from a pair of speakers or from one's headphones, or its coming from a tube or solid-state powered component. Admittedly, even though there is a separation of instruments that result from listening to just about all the material that comes through the WA7d, it is not by a long shot a representation of the original event's positioning of the instruments. It is what it is. But it is one of the great things about listening to a set of high-quality headphones such as the Grado PS-1000 and a great headphone amp such as the Woo Audio WA7d Fireflies: The music isn't just lumped together in an amorphous blob, but the voices and instruments are separated so one can hear the musicians, producers, and engineer's original artistic intent.
Another trait of the WA7d is the ability to reproduce real instruments and voices with a very lifelike sound. This is one of the greatest characteristics of the WA7d, so when playing orchestral and jazz my headphone setup became a sonic time machine, if you will. When I spun my LP of Le Sacre Du Printemps recorded by the Leonard Bernstein's New York Philharmonic in 1959, I was "there". In part due to the excellent Grado PS1000, it brought me to another place and time. With this record I bypassed the WA7d's digital section and listened through the analog input of the WA7d. Wow! It is a great recording, made even greater due to the beefy sound quality of the WA7d. The right side of the orchestra (the double basses and to a large extent the cellos), the percussion, and tympani rattled my brain. In a good way. I could see the string section in my mind's eye, each playing as a whole but separate, the sound as smooth as silk via this re-issue on 180 gram vinyl. Each section of the orchestra occupied a different space in the soundfield, yet there was no discontinuity between them, ever. Although the "soundstage" was nowhere near realistically laid-out and scaled, but still, the separation of each section let me bathe in Stravinsky's complex masterpiece.
Those who are aware of my tastes in music (or lack thereof) know that I hardly spend most of my time listening to music that features real instruments and voices recorded in a real space. So, what about music that isn't "real"? That is a subject where I'm tempted to waste lots of space with questions such as "is a recording of a microphone placed in front of a guitar amplifier "real"? Is a multi-track recording of a drumset with the microphones inches away from some of the drums "real"? Is a recording studio where a band is set up to record their basic-tracks a "real" space?" I think we've come far enough, and the audiophile demographic has changed enough, to answer these questions as "yes".
Therefore, the WA7d can reproduce the 2013 self-titled debut album by Ensemble Pearl, a band comprised of members of Sunn O))), Boris, Jesse Sykes & The Sweet Hereafter and Earth with as much "realness" as one who is listening to the band in the studio (wearing earplugs, I hope) as they record the album, and then attend the mixing sessions and hear it playing back through headphones with the rest of the band, engineer and producer -- although when we're listening it's through a much better headphone amplifier, with (hopefully) much better headphones then they are. When listening to this album the heavy sounds that emanate from my PS-1000 headphones connected the WA7d/WA7tp set up are mesmerizing. The guitars don't sound like "normal" electric guitars playing through a loaded pedal board connected to stacks of their amplifiers, but droning ghosts (a description I read in a listener review). The cymbals on the drumset sound as if they are sometimes being struck by something other than drumsticks, and the added percussion isn't the off-the-shelf variety, that's for sure. But I hear the end result of what they were setting out to accomplish, and because of the WA7d setup can hear everything that was recorded – not only because of the stupendous amount of separation between the individual sounds, but the "realistic" sound that the WA7d/tp is reproducing of each instruments. Screw the "I know what a real violin sounds like so I can judge this component" mind-set. This is some heavy stuff, and it is obvious why this album made my and many other's best of 2013 list, and it is made so, so enjoyable through the Woo Audio gear.