Woo Audio WA3 Headphone Amplifier in Review

[shigzeo]

If there ever was an argument for valves in audio, it no more evident than at home. A large, heavy, and hot valve power amp is an item of luxury. But if you ain’t got the home, or you just prefer to augment your collection with a good headphone set up, your source (surprisingly, even an iPod) and a good valve headphone amp are a match made in heaven. Why? Valves aren’t about performance – they are about sound. Woo Audio has been churning out quality amp after quality amp, each with one thing in common: milky smooth valves and a lot of power. Their WA3 is a great valve amp at a very good price point which puts the fuzzy wuzzies into your best records.

Specifications

Build and Package
There is nothing to regret in Woo Audio’s construction. The WA3 is as sturdy as my stainless steel Marinoni Fango CX – nothing can conquer it. Woo has smoothed edgy corners, given the amp 4X4 clearance, and stopped the WA3’s bolts like a freaking nuclear damn. Each valve comes snuggly fitted into slim cardboard boxes, or dressed in foam sleeves, and the entire amp is tailor-fit into a brick of pressure Styrofoam. The WA3 is ready for nuclear holocaust.

It is solid, heavy, and bombproof. Nothing flexes. Nothing bends. The main case is battened down in extruded aluminium and ported for the valve and the power integrated power supplies. It's tubby backside secures the amp on any surface against the constant swapping of headphones. Rest easy, the WA3 won't slip.

Heat radiates up and out, through its open grill, but the amp vents through the bottom; and a modicum of exhaust escapes through the valve ports. Valves get warm, so exposing them on the top is important. The only reservation I have regarding this design is that there is no protective chassis for the valve tubes - not that anyone will lay things on top of the peaky WA3, but it never hurts to add a roll-cage.

The WA3’s belly button, the overly large and perfectly balanced volume-pot dominates the front panel. Ergonomically speaking, it is perfect: on the left is the 6,3mm headphone jack and on the right, the power switch. The back sports the Pre-amp out and one set of line inputs. Everything is firmly bolted and battened.

If I was a car guy, I’d say it is like a perfectly built AMG. But, I’m not, so I’ll just say that its industrial lines remind me of the best-engineered classic bicycles. If ever something was to go amiss, it could easily be replaced. Under the bonnet, Woo Audio use point to point wiring rather than circuit boards, a bragging point among audio makers, but for end users, a sign that do-it-yourself tweaking/repairing is simple.



Features
One of the special features of a good valve amp is that its stock valves can be rolled. If you prefer more power, or longer valve life; even if you’d rather a different glow, you can roll out the old and in a new set of valves. The WA3 utilises 6922 and 6080 socketed valves from GE and Phillips. The combination sounds good, but valves will eventually burn out, needing replacements. Fortunately, it is as easy as mildly ‘rolling’ the valves around till they lift loose.

Valves have their own sound. Generally, they are known for being ‘warm’, technically, this warmth comes form high orders of harmonic distortion and a goodly amount of channel bleed. Distortion may be a bad word to newbie audiophiles, but it is actually widely used among high-end audio companies and among engineers. The WA3 harnesses this distortion to very pleasing results.

But before we get onto sound, I’d like to mention why this amp is a good value. 475$ isn’t cheap, but then, the WA3 isn’t a factory-churned amp. It is a beautifully engineered piece of kit. It looks great on top of a desk, a bedside stand, or near another audio component. The WA3 also has a serviceable pre-amp on the back. But more than anything, it supplies all the power you will need for the most intimidating of headphones.



Continued in next post:

[shigzeo]

Sound
Sound
Every amp strives for a certain sound. Some, like the Einar Sound VC-01i and the MST FiQuest, attain to neutrality. Woo Audio does neutral, sure, but more poignantly, its warmth ‘tames’ many cutting headphones.

For years, my go to headphone has been the Beyerdynamic DT880. Last year, I parted with my 250Ω version as it was my cyclocross bicycle, or the headphones. Hands down, Marininoi won out. This year, however, I purchased the 600Ω version. Both versions are alike: revealing, harrowingly wide, and generally, mid-oriented, but boasting lungy treble. Bass comes out in gobs, but not enough to excite hip hop fans or break the glass face of an iPod. Generally, however, the DT880 is known for sometimes harsh, grating treble that really squeals on poorly recorded albums.

The WA3 isn’t the warmest of valve amps out there, but it affords the DT880 a very pleasant introduction. The sometimes nonplussing, stringent treble is gone. But perhaps what really sniffs out the good match is how well the WA3 and the DT880 jive in the lows and mids.

The WA3’s magic starts at the bass and works its way up. In terms of frequency response, the WA3 isn’t doing anything out of order – certainly not technically better than a lot of other sharp-as-a-tack amps out there. No, it is warm and weighty. The lows kick in strongly, but in paced, calculated steps, like the WA3 knows the dance. It isn’t a monitoring tool – it is a listening tool.

It’s funny actually, the bassy, fun DJ1Pro jives very well with the WA3. More so than the DT880, however, its mid-bass comes out in force - nothing chaotic, but spiked by something intoxicating. Otherwise, the WA3 plays fair with every full-size headphone I’ve used. Its warmth tames some sharp headphones, and its smooth midrange is addictive with everything from an AKG K701 to a Sennheiser HD600. Mid-bass oriented headphones, especially low-Ω models can splash around but generally mate well with the WA3 warmth policy.

The WA3 is pretty well balanced from left to right – my unit has a channel difference of less than 0.7 dB that is inaudible with the DT880. Every volume-pot amp I’ve used favours one side or the other especially at low volumes. Thankfully, the WA3 is has enough pot-play that even sensitive earphones can reasonably be used and at normal listening volumes, it is perfect with any headphone.

There’s no need to worry about volume-induced distortion either – at least with >100Ω headphones. The DJ1Pro, a somewhat hard to drive full size headphone, is loud and controlled by 9-10 o’clock and by 4 o’clock, there is a small amount of sizzle, but at that volume setting, your ears would be dead anyway. The 600Ω DT880 simply doesn’t stutter from the WA3 and is plenty loud by 9-11 o’clock and ear piercing by 1-2 o’clock.

So is there anything to not like about the WA3? That is up to you. It is a headphone amp, plain and simple. It works well with high quality sources, or fed from an iPod. It is warm and somewhat laid back. It is smooth. Many amps disappear, leaving the recording and the headphones; the WA3 struts its stuff, adds flavour.

But, the WA3 isn’t a do-it-all headphone amplifier. Intensely warm headphones can sound stuffy. And inner earphones cause the WA3 to lose upper mids and treble, forcing an AM radio sound. They are listenable though which is surprising: many home-size amps hiss madly with inner earphones, or at their lowest volume settings, are too loud. Instead, the WA3 outputs typical valve noises: small clicks and pops, and a constant, but far from annoying hum. Full size headphones are free of this noise, but earphones bring it out.

So what is the conclusion here? Audio purists may prefer a flat-line output, snuff the warmth and channel bleed. I understand the reaction – at least at source level. But in an amp, character – at least good character – is something to cherish. The WA3 has it. For reference headphones, it has it in lush, warm spades. For already heavily nuanced headphones, however, it is a toss up.

If you can audition the WA3, do it. If you can’t – take my word for it: most headphones sound fab from the WA3, and if they don’t, you have probably already thought about selling them.

Notes on the Pre-amp. The WA3 sports what I have called a ‘serviceable’ pre-amp. I stand by that. If you want to connect it to an external piece of audio, you can. But note this: its output is linked to the headphone output, meaning that if you want to enjoy it, you’ll have to rotate the volume knob. This is a little unconventional, but it works.

[shigzeo]

Conclusion
475$ is not cheap. Neither is a Marinoni Fango. But both do their duty very well. While one hops its way down bumpy trails and across rivers, the other drives proper headphones. In either case, you can spend less and get something from Taiwan, something with a circuit board and Martian ergonomics. The WA3 sounds good, very good, but it isn’t a reference device. No, it is a warm, lush listening device that mates perfectly with proper headphones.

For the enjoyment of music, the WA3 sits high in its class and is well constructed to boot.

Headphone amps and DACs help your headphones get the most out of their transducers. Take a look through our headphone section for suggestions of good upgrade/sidegrade options, and our headphone amplifier section for suggestions on how to wring out the best performance from your beloved phones.

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[shigzeo]

The following are the RMAA results: Notice that the WA3 is a headphone amp and as such, isn't good at driving earphones or inner ear monitors. This goes for both dynamic based as well as balanced armature based earphones. It is quite like listening to a telephone call, or AM radio. Headphones, on the other hand, sound great.

Frequency Response:


Dynamic Range:


Total Harmonic Distortion:


Intermodulation Distortion:


Stereo Separation:

[shigzeo]

Just for reference, there is a long Woo Audio Owners thread at Headfi - great pictures and impressions of everything there.

[NineSwords]

This is one Sexy amp. There is just nothing as sexy compared to a open tube amp.

[shigzeo]

And Woo Audio have a lot of crazy sexy amps. The WA3 may (according to maker Jack Wu) be the most tubey sounding in their lineup. It sounds phenomenal with proper headhones like the Beyerdynamic DT880 and Sennheiser HD600, two incredible German headphones.

[WooAudio]

shigzeo,

Thank you so much for such detailed and comprehensive review. You did a great job!

The WA3 is a OTL design (output transformer-less) and it works exceptionally well with high impedance headphones such as the DT880/990, Sennheiser HD600/650, ect. Most of the IEMs are low impedance that the WA3 would be difficult to drive them properly. On the other hand, all our output transformer coupled amps such as the WA6, 6SE, 22, and 5LE handle these headphones easily.

Again, thanks for the review and I wish you success in your audio review journey.

Jack

[shigzeo]

Thank you Jack - it is certainly phenomenal with everything but IEMs and that is fine as I'd hesitate to use it that way. My wife is stunned especially with the DT880!

[jaygot]

Thanks so much for the review, Jack! Like you, I live in South Korea. I own Sennheiser HD800s, but am not satisfied with the performance I am getting out of them by pairing the headphones with an and an iBasso D10 amp (which is designed more for on-the-go listening and does work phenomenally well with my JH13 Pro IEMs).

So anyway, I am thinking of investing in a proper at-home setup -- including the WooAudio 6SE amp (with Princess Sophia upgrade). Do you know of places in Korea where I might be able to demo and/or buy WooAudio products or do I have to order directly from the manufacturer (and therefore pay the exorbitant import taxes levied on foreigners bringing items into the country)? Any insight would be much appreciated!