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Positive Feedback ISSUE 65
january/february 2013


The Woo Audio WA7 Fireflies 32/192 DAC and Tube Analog Headphone Amp
by Andy Schaub


woo audio wa7

You'll be the brightest light
The world has ever seen
The dizzy height of a jet-set life
You could never dream

—Natalie Merchant, "San Andreas Fault"

I remember first seeing the WA7 in a picture on my iPhone 4S while sitting in a Laundromat with my girlfriend Lori, waiting for her clothes to dry. I immediately sent Jack Woo an email asking for a review sample and, many months later, it finally arrived. A nice silver one with clear glass and stock Sovtek tubes, a beefy power supply including a long umbilical cord so you can hide the power supply and just see the lovely WA7 Fireflies sitting next to—in my case—a 17" MacBook Pro with a 256GB solid state drive inside it. I had been using an Apogee Duet 2 with a Locus Design Axis USB cables, and a pair of Moon Audio Blue Dragon Sennheiser HD650's at work, because the Apogee is a little bright and both the Axis and the Blue Dragon cable, as well as the natural high-frequency attenuation of the HD650's, help to give the sound a nice, warm glow all the way up to 24/192. I thought, given the price of the WA7 ($999), I should start with a less expensive USB cable; so I pulled out my Locus Design Polestar and—after a bit of fiddling to get the computer and Pure Music to recognize the WA7—queued up the 24/96 download of Tigerlily by Natalie Merchant from Unlike the Duet 2, the WA7 was much more neutral, and I found that the Blue Dragon HD650's overly muffled the high frequencies, so I switched to a pair of Black Dragon Ultrasone Edition 10's. While I wouldn't describe the sound as bright, it was a little raw; so I finally settled on a pair of Silver Dragon Audez'e LCD-2's, which had a "just right" quality with the WA7. It still needed to break in though; so I queued up the 24/96 download of Mark Knopfler's Shangri-La, also from, and just let it play. It only took that one album for things to start to sound right; however, I felt that the WA7 had yet more potential. I asked Jack Woo for an extension on the loan, to give the WA7 Fireflies a better chance of being all it could be.

WA7 Fireflies in Silver with a Clear tube protection glass

I will say that on "5:15 A. M.", Mark Knopfler's voice had plenty of air or ambience around it while at the same retaining ample bass and possessing a sweet, extended treble. I switched to a 24/44.1 down sample I had made of Like Minds by Gary Burton et al (because my other DAC, the HRT Music Streamer Pro, doesn't properly support 24/88.2, at least my earlier model doesn't), also from On "Question and Answer" both the vibes and the piano had a very natural sense of rhythm and drive to them, and I found it quite shocking that the WA7 Fireflies had broken in after just one album, because it had already developed the tube warmth and kind of sweet treble that you just can't get from a solid state amplifier. On "Elucidation", Pat Metheny's electric guitar had a slight crying sound to it without seeming harsh, so—again—it was, "just right". I should mention that the output impedance can be adjusted with a switch on the back. With my HD650's I had it set for high-impedance headphones, whereas with my Edition 10's and LCD-2's, I had it set for low impedance headphones. It's a nice touch on a well thought out design. On "Country Roads", still from Like Minds, the bass and drums had a nice pluck and thwack to them, the bass was ample without be overstated, and the cymbals had a nice treble glow. This is possibly the most linear DAC and headphone amp I've heard connected to a computer for under $1,000.00, maybe more. On the 24/96 download of Duo Sonatas from Channel Classics, the violin and viola both has a nice sense of air and ambience while retaining warmth to the sound that makes the music very engaging. Rachel Podger is the violinist. According to Wikipedia, "Podger currently plays a violin made in Genoa in 1739 by Pesarinius, a later student of Antonio Stradivari. Initially Rachel played a 1988 Stradivarius copy by Rowland Ross." You can tell that the violin has Stradivarius-like warmth, and that's saying a lot for a little two-tube amp with a built in 32/192 DAC and a pair of headphones that cost less than $1000 (minus the Silver Dragon cabling). I have trouble tearing myself away from the music to write.

While it's nice to have 32/192 capability— I will review at least one very high-resolution download—I was curious how the WA7 Fireflies would perform with red book CD rips, and even lower iTunes Plus downloads; to that end, I queued up my CD rip of Renmin Park by Cowboy Junkies. By the time I had gotten to the title track I was convinced that the WA7 was equally at home with rock, classical, and jazz. Margo Timmins' beautiful voice was dripping with sorrow and Michael Timmins' guitar strums had a weight and depth to them that I'm not sure I get from my Berkeley Series 2 Alpha DAC. Regarding iTunes Plus downloads, I queued up Thimar by Anouar Brahem et al on the ECM label, dropping a ten-foot Silver Dragon extension cord between the WA7 Fireflies and my LCD-2's so I could relax on the couch. The truth of the matter is that I found the music very enjoyable; and the longer I listened, the less I remembered that this album used lossy compression (where bits get thrown out) and the more I just fell into to the music. Perhaps it was because the WA7 had started cold and needed twenty minutes to warm up; but by the time I got to the last track, "Hulmu Rabia", I felt slightly disappointed that the music was ending. No, it doesn't sound as good as my Audio Note CD 3.1x/II playing through my Woo WA6-SE with my stock Fostex TH900 headphones; but given the form factor and price, why should it? I should also mention that I use a Harmonic Technology Magic Cord going into an Equi-Tech balanced transformer going into a PS Audio Power Plant 10 in the main system; whereas with the WA7 Fireflies, I just used an ordinary well-shielded power cable—like you'd find with a desktop computer—going into an ordinary hardware-store power strip. So that's even more of a reason for the WA7 Fireflies and its own beefy power supply to seem remarkable by comparison.

So I finally copied the 24/192 download of Waltz for Debby from onto my 17" MacBook Pro and fired up the WA7 Fireflies, including Pure Music 1.89b and iTunes 11.0.1. It immediately sounded lush and fantastic; the piano had a natural tone. The bass plucks sounded resonant without being euphonic. I felt compelled to listen to the whole album it one sitting, lying on my couch, and thinking this is the closest I've heard from a semi-portable DAC/headphone amplifier (i.e., one can you take into the office) to my Audio Note CD 3.1x/II red book CD player and Woo WA6-SE headphone amplifier. I had no complaints about the music, no complaints about the sound; in short, I was stunned and taken aback at how good the WA7 Fireflies could sound given the right source material. Now the question is how good it sounds in comparison to other DAC/headphone amp combinations out there. I already know it sounds better than my Apogee Duet 2, which is a little (well, a lot) bright; but how about something like my old HRT Music Streamer Pro, connected via Cardas adapters to an Audio Note AN-Vx cable with Eichmann Silver Bullet Plugs and then into a Black Gate modified Tri TRV-84HD? It'll only go up to 24/96 and doesn't reliably support 24/88.2; but in their day, both sounded good separately. So how about together? Going back to the 24/44.1 download of Like Minds, I heard the smoothness that characterized all three products; but they lacked the detail and the air of the WA7 Fireflies not to mention its smaller form factor. I would have to listen some more. Returning to the TRV-84HD after letting it warm up a bit, I have to say that it did sound more open and the second to last track on Link Minds, "For A Thousand Years", sounded particularly musical. Queuing back up the 24/96 download of Duo Sonatas, I hear silkiness to the strings that aren't as apparent with the Woo; but it's six of one, half a dozen of another. All things considered, I'd rather have the Woo.

The WA7 Fireflies can be used a standalone DAC or headphone amplifier; so I thought it would make sense to mix things up a bit and try it in both capacities, first as a standalone DAC, then as a standalone headphone amplifier. I disassembled my HRT Music Streamer Pro, connected via Cardas adapters to an Audio Note AN-Vx cable with Eichmann Silver Bullet Plugs, and then into a Black Gate modified Tri TRV-84HD and used the WA7 in lieu of the Music Streamer Pro. Without "cheating" and jumping to 24/192 materials, I stayed with 24/44.1 and 24/96. It involved adding an extra generic power cable into the mix, and setting a switch on the back of the WA7 to "D/A", plus plugging the input end of the Eichmann Silver Bullet Plugs into the RCA connectors on the back of the Woo. It worked flawlessly and returning to the 24/44.1 download of Like Minds, I found the much of the detail I had previously heard from the WA7 Fireflies came from its 32/192 USB DAC, but the TRV-84HD still sounded pretty sweet if lacking in overall air and ambience. Switching to the 24/96 download of Duo Sonatas only confirmed my previously made assessment; although, I will say that there was more air with Duo Sonatas than there had been with the Music Streamer Pro, perhaps because of its higher resolution. Then I switched things around again, using the Music Streamer Pro as the DAC (which is bus powered) and using the WA7 Fireflies as the headphone amplifier by reconfiguring the cables and sliding that three-way switch to "RCA". Both with Like Minds and Duo Sonatas, this sounded substantially better than the other way around except for the fact that now I had air without so much detail. Finally I just gave up in this obsessive-compulsive reconfiguration and plugged the Locus Design Polestar back into the WA7 Fireflies, setting the slider switch to "USB" and plugging a pair of black JH Audio JH16 Pro's into the mini plug output of the WA7 through five feet of Moon Audio Silver Dragon IEM cable. Although I find IEM's uncomfortable, I have never heard then sound better; and I paused for a few minutes to listen to music before carefully cleaning them with an AudioWipe and putting everything away. I haven't decided for sure yet; but I just might buy the review WA7 Fireflies. Or maybe I'll save it for my next birthday.

Kindest regards,