The Woo Audio WA5 is truly a 300b amplifier to pay attention to.This multifunctional, aluminium encased juggernaut can reproduce sounds in headphones and speakers with unremitting clarity! It holds the ability to effortlessly power planar and dynamic headphones of both high and low impedances. The amplifier has become (at least for me) the perfect pathway from headphones into speakers; it can push 8 Watts per channel into 8 ohms making it one of the most versatile headphone/speakers amplifiers on the market.
In the past many audiophiles would gravitate towards headphones after developing a taste for high end speakers. Headphones were seen as a backup for the bigger more exotic speaker rig in your home that you couldn’t blast at night because the kids were in bed. However advancing technologies in headphone design have allowed levels of fidelity that are comparable or even on par with some of the best speaker setups. There are a lot of us out there that want the best of both worlds and amplifiers like the Woo Audio WA5 deliver just that.
Woo Audio are a US based company founded in 2004, and all their products are designed and assembled in New York. They are a family run business where the leading engineer and builder Wei Wu – is also the patriarch. The other two members are brothers –Dong and Jac. Dong’s expertise lies in designing and engineering while Jack manages the face of the company, taking care of sales, publicity and customer support. The vast majority of parts used in the Woo amplifiers including magnets, output transformers and filter chokes are designed on site where they also developed a unique winding method.
Build
All Woo Audio products are known for their beautiful minimal aesthetic. With their design approach; the reduction of non-essential form seems to be the goal. Some of the design features are vaguely reminiscent of the works of the minimalist artist Donald Judd. The majority of Woo amplifiers have a sleek and uniform finish and this is also true of the WA5. The shape of the amplifier never distracts from the most apparent and functional design feature – the vacuum tubes; the eye is drawn immediately to the glass.
The amplifier is large, in fact it’s one of the largest headphone amplifiers in production its dimensions being 8.5(H) x 9(H) x (17) inches for both chassis. Thankfully Woo Audio have added two handles on each side of the transformers for lifting. All essential handling parts are placed with the utmost care. The volume knob consisting of a large circular chunk of aluminium is centred right in the middle of the left chassis. The wheel itself being smooth and easy to turn belies its weighty construction. All corners and edges of the WA5 are polished to a softer consistency of the main body of the amp. Two acutely shaped selectors exist at either side of the volume pot. One is for changing input, the other for switching from high to low impedance and from K1000 to speaker port.
The K1000 port delivers the amplifiers full power into a headphone and was originally designed to meet the handling needs of the AKG K1000 headphone. However it is also said to be one of the best pairings for the Hifiman HE6 headphone and the Abyss AB-1266; and I know myself that many headfier’s use it for those purposes. At the back of the amplifier you can find four pairs of gold plated inputs for connecting different sources and two pairs of gold plated speaker terminals. Also at the rear are sockets for the umbilical chord that connects the dual chassis.
The WA5 utilises two 300b power tubes along with a pair of dual 6SN7’s coupled with two 5U4G rectifiers. All internal components are wired from point to point by hand.
This amplifier is a heavyweight among headphone amps weighting 35lbs while its twin power supply clocks in at close to 40lbs. It can handle any headphone from 8 to 800 ohms and outputs .850 watts into 300 ohms and .560 watts into 600 ohms on the HPH setting. The amplifier features two independent circuits, one dedicated to powering headphones and the other a separate implementation designed to handle speakers. On the front of the left chassis housed to the right, it has a ¼’’ headphone jack and on the opposite side an XLR connector for K1000 and HE6.
Sound
Put simply the WA5 is the best amplifier that I have ever heard. I also own a Woo Audio WA2 and the differences between these two amplifiers are far from subtle. I had previously upgraded the tubes in the WA2 which improved its sonic capabilities to no end, but even at that it was no match for even the stock WA5. I had naively thought that the WA5 with stock tubes would not be a huge improvement over a maxed out WA2 but I was wrong. The WA5 trumps the WA2 in every way imaginable – bass, mid-section and treble seem infinitely extended by comparison.
The WA5s soundstage is deep and expansive. Its 300bs set the listener in a three dimensional space like no other tube can, but the biggest difference between the two amplifiers are their rendering of treble. In this regard the WA5 is phenomenal, it has a way of displaying sounds in higher registers without any glare or severity. This lack of glare on top makes for an extremely pleasant and euphonic listening experience. The WA5 manages to take the beautiful warm character of its smaller brother (WA2) without sacrificing any detail across the rest of the spectrum. It does this whilst also stretching the midrange to allow space into a recording, where with other amplifiers; that space is just not there. Even more surprising is that after burn in (approx 150 hours) the midrange gains even more scope.
The tubes that come with the WA5 are Shuguang 300b – Shuguang 5u4g – Sylvania 6sn7. I had imagined the sound would be harsh in the treble region when paired with my HD800. When I plugged in I breathed a sigh of relief – The HD800 never sounded this good before. In fact the pairing of WA5 – HD800 is truly magical. The WA5 accentuates the HD800s ability to enlarge the sound bubble that surrounds you when listening. The soundscape changes immediately when this amp is turned on and the HD800 is injected with vigour and oomph. It really becomes a different headphone altogether. One of the albums that sounded great with the WA5/HD800 was the 1959 album by Trombone player Curtis Fuller entitled ‘Blues-ette’. This album was originally recorded by the legendary Rudy Van Gelder and has that trade mark warmth in its presentation which is particularly noticeable on the first track – ‘4 spot after dark’. Van Gelders recording technique which usually involves adding reverb to the brass solos, in this case Fullers trombone couple that with the WA5s smooth yet detailed characteristics and you are left with a remarkable listening experience. The WA5s ability to pick out the reverb on fullers trombone was incredible especially near the end of ‘4 spot after dark’ at 4.46 – I could visualize the air moving around the sound hole of the trombone. These small details were very apparent on the WA5 and not so much through the Cary 300b.
There were times when I sat down to listen and thought that the sound couldn’t possibly be any better than what I was hearing – then I upgraded the tubes and realised the true strengths of this amplifier. Most of the tube amps that I was familiar with before receiving the WA5 were sensitive mostly to changes in the power (output) tubes, where changing driver and rectifiers had little or no effect on the performance of the amp. The WA5 is extremely sensitive to all changes in tube types.
There are hundreds if not thousands of tube combinations available for the WA5, couple that with its hypersensitivity to those changes and you are left with a chameleon of an amplifier with the capacity to remodel itself depending on the tastes of the listener. I settled on the Emission Labs 300B mesh plate for power, the Tung Sol 6F8G with a 6SN7 adapter for driver and a Brimar 5ZG4Y rectifier. This combination is both luscious and refined. The advantages that these tubes have over the stock are instantly recognisable – in short all areas of the soundscape are magnified, improved, polished, expanded and controlled with definition and accuracy.
I decided to try the WA5 with a set of open baffle speakers sensitive enough to achieve high volumes. The speakers that I choose were the Dubh floor standers designed by the Irish Audio company Éist Audio. These speakers have a sensitivity of 91db and are a beautiful pairing for the WA5. I had lived with the amplifier for 2 months without hearing what it had to offer when powering speakers. The results when I finally got around to it were outstanding! One of the first tracks I listened to was Gregory porters ‘Be good – Lion song’. This track is perfect for testing male vocals. The WA5 reproduced Porters vocals with astonishing realism. What impressed me most was the speakers ability to place instruments in the soundstage which was even better than the HD800 In this regard. I found that one of the main differences between speaker and headphone listening on the WA5 was that the speakers were capable of conveying height in a way that the headphone could not, for example – when listening to ‘Be Good’ on speakers I could actually tell the height of Gregory Porter’s mouth from the floor! His voice would resonate from one point in mid-air and expand outwards.
Another huge contrast between speakers and headphones is the displaying of depth in the soundstage. The HD800 is an amazing headphone in terms of soundstage size but with the WA5 and Éist Audio Dubhs there was an extra dimension from the centre to the back of the soundstage. For example when listening to Mendelssohn’s Violin Concerto in E minor I could visualise the orchestra stacking back in rows just as one would experience it if one were in the concert hall. This piece sounded tremendous with the Dubh floor standers and rendered Julia Fischers bowing technique with verisimilitude. The sound of her violin seemed to float just in front of the orchestra and as the piece unfolds the intensity of her playing became more and more involved.
Conclusion
This amplifier has become the centre piece of my listening station. Its ability to effortlessly drive headphones of any kind puts it at the top of the food chain. The added feature of speaker compatibility is no afterthought, in fact it is one of the very best speakers amplifiers that I have ever heard being on a par or even better than the Cary 300b. Every type of music sounded sensational through the WA5 – it reveals details in recordings that just aren’t there with lesser amplifiers. Its beautiful aesthetics and military build are nothing short of breath-taking. Finally I have an amplifier that satisfies all my listening needs and I am confident that it will give me many years of satisfaction.
Test Tracks
Julia Fischer – Mendelssohn, Violin concerto in E minor, 1st movement
Janos Starker – suite no 4 in Eb major
Evgeny Kissin – Tchaikovsky, Piano concerto no 1 in B flat minor Op 23
Gregory Porter – Be Good (Lion Song)
Curtis Fuller – Five spot after dark
Curtis Fuller – Love your spell is everywhere
Pink Floyd – Nobody Home
Ken Nordine – Reaching into in
The Kingston Trio – Raspberries Strawberries
Joe Walsh – Lifes been good
Technical Specifications:
* Two 300B [PDF] power tubes * Two 6SN7 [PDF] drive tubes * Two 5U4G [PDF] rectifier tubes
* Voltage: AC 110/220V, 50/60 Hz
* External dimension (each): 8½(H), 9″(W), 17″(D)
* Weight: Amp Unit: 35 lbs, Power Supply Unit: 40 lbs
Headphone Amplifier Specifications:
* Headphones impedance : 8-800 Ohms
* Frequency response: 10 Hz—60 KHz, -2dB
* Power output >= 1.5 watt
* Signal/Noise: >= 95 dB
* THD: <= 0.08%, 1Khz
Speaker Amplifier Specifications:
* Power output: <= 10W x 2, THD <= 3%, 1Khz
* Frequency response: 16—38 Khz, -2dB
* Output impedance: 8 ohms
* Signal/Noise: >= 90 dB
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