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Positive Feedback ISSUE 65
january/february 2013


A Tale of Two Woo's: The WA22 and the WA6-SE and What "Balanced" Really Means
by Andy Schaub


"Hey Jude, don't make it bad.
Take a sad song and make it better.
Remember to let her into your heart,
Then you can start to make it better."


OK, I admit it. I thought the Woo WA22 had a phase splitter in it… until I read the instruction manual and contacted Jack Woo. Then I found out "Nope," the WA22—though an excellent, excellent headphone amp—does not convert single-ended (RCA) inputs into balanced output. It just plays it as it lays. So in my all SET (Single-Ended Triode) system, I was wasting half of the circuit. There was just no two ways about it. So after much thought and consideration, I sold my WA22 and bought a WA6-SE, which is a single-ended triode headphone amp; and I have to confess I'm much happier. That's not to say the WA6-SE is a better amp than the WA22, it just suits my system better. If I had all Audio Research or Ayre (or Bryston, which makes its own very reputable balanced headphone amp that does have a phase splitter), then the WA22 would have been appropriate; but with my Audio Note Oto Phono SE Signature and my Audio Note AN-Vz interconnects, the WA6-SE is a better match, even with the stock tubes and no special modifications. And, in truth, it really does sounds better for me. But first, let's answer that question: what does balanced really mean?

"Balanced lines work because the interfering noise from the surrounding environment is induced into both wires equally. By measuring the difference between the two wires at the receiving end, the original signal is recovered while the noise is cancelled. Any inequality in the noise induced in each wire is an imbalance and will result in the noise not being fully cancelled. One requirement for balance is that both wires are an equal distance from the noise source. This is often achieved by placing the wires as close together as possible and twisting them together. Another requirement is that the impedance to ground (or to whichever reference point is being used by the difference detector) is the same for both conductors at all points along the length of the line. If one wire has a higher impedance to ground it will tend to have a higher noise induced, destroying the balance."

Put another way, in a balanced circuit, you have two signals travelling along parallel lines that carry the same music, but are 180 degrees out of phase with each other. When the two signals are recombined, one side gets its phase inverted and suddenly you have double signals in phase with each other but noise picked along the way out of phase and perfectly identical, meaning that most of it gets cancelled and you get a quieter line (or amp, or whatever else). Put in even simpler terms, it's a way of reducing noise in a circuit while maximizing power or amplitude; and when it works, it works great; but it's not always necessary and based on my own experience, I think single-ended circuits, implemented properly, sound more musical. That's just an opinion and not meant to be interpreted as fact. It's just that I liked my Woo WA22 (with it's all premium tubes) so much, that I tried to find a place in my system with balanced output where I could put it; but the only place that qualified was the output of my Berkeley Audio Design Alpha Series 2 DAC, and there was simply physically not enough room to put the WA22 on the digital music server rack. So, with great dismay but joy for its new owner, I sold it and ordered a WA6-SE at Jack Woo's recommendation.

Now let's get to the good stuff: the sound. The first pair of headphones I hooked up—with an adapter—were my balanced (Moon Audio Black Dragon) Denon AH-D5000's, going into the low impedance output of the WA6-SE. Miracles are born! I'd never heard such good sound coming from these well-reputed headphones, the bass was notably richer. In just the first few hours, the soundstage widened and improved and the imaging became rock solid while the treble sweetened and softened. I don't remember what came next, just that with each pair of headphones, I heard "more", more bass lines, more treble, more midrange detail; this is the way a reference headphone amp should sound. And I was perfectly happy with my WA22 until I realized the mismatch! I think the best overall listening experience I had was with my Fostex TH900's (stock, unmodified). After several hours of break in, they took on an almost electrostatic sound (only with bass, ample, pleasurable bass). Because they represent an industry standard, I felt compelled to try to my Sennheiser HD800's with Moon Audio Silver Dragon cabling. So I queued up ECM's Manu Katché in my Audio Note CD 3.1x/Mk. II and plugged the HD800's into the high-impedance output of the WA6-SE.

Again, I got an almost electrostatic sense of drive of rhythm while at the same time remaining oh so laid back, very difficult to do with the HD800's. Perhaps I didn't get the visceral "thud" and "thwack" of my HiFiMan HE-5LE's (also with Silver Dragon cabling); and there might have been a twinge of brightness to the top end, but I was running the amp cold with the stock tubes and all silver cabling on a notably bright pair of headphones, and still just couldn't get enough of the music. Many people prefer the Blue Dragon cabling—or another brand—with the HD800's. I'm kind of a detail freak (I used to own Spectral) and I want that clean, crisp dynamic range. So what can I say? The combination was phenomenal; and that was with nothing special save (a) my system itself and (b) the Harmonic Technology Magic Power Cord, which cost more than the amp itself at around $2K for a six-foot plus run. As I listened to Manu Katché and things settled in, I began to truly appreciate the pleasure of headphones again in a way I couldn't even with my portable rig(s). Sure, they're nice, and the Ray Samuels SR-71B does have a phase splitter in it; but it doesn't sound like the Woo WA6-SE (nor the WA22 for that matter). As you can tell, I'm happy; and I think that's all that really counts.

Kindest regards,


P. S. Each pair of headphones has nominal impedance. To accommodate all of them, Jack Woo cleverly designed two outputs into the WA6-SE, a low and a high output, just like the switch on the Woo WA22. The turnover point on the WA6-SE is about 100 Ohms, so I listen to the vast majority of my headphones using the low-impedance output; however, some do qualify for the high-impedance output, including the cruelly 300 Ohm HD800's. However, you can mix things up. So if you prefer your HD800's plugged in the low impedance output, go for it. While the output of the WA6-SE is very high (over 1 watt), I don't think it has enough power to drive a pair of HE-6's; but I could be wrong. As always, ask Jack, and consider the most expensive premium tube upgrades with the Teflon pin adapters, which reputedly put out more power.

Woo WA22:

Woo WA6-SE: