Woo Audio offers a remarkably deep bench for those headphonistas interested in vacuum tube amplifiers. But when it comes to the 300b, arguably the finest audio tube the world has ever known, Woo Audio has only a couple of options. Aside from the monoblocks, that is. Those are something … different.

The first is the WA5, an amplifier that Frank Iacone of HeadphoneGuru, reviewed for us here at PTA. The (very) short take on that amp? The Guru was a fan. A big fan. A biggity-bigbig fan. He loved that amp. He raved. He waxed poetic. He burbled. He bubbled. He loved it. He loved it so much, he bought it. I’m not sure there’s a higher indication of personal enthusiasm than that, is there?

The WA5 is a dual-purpose device — it can drive your headphones to a fare-thee-well, and then also drive your loudspeakers (certain assumptions about levels and sensitivity aside) for when “personal listening” requires the possibly inadvertent inclusion of your non-headphone-wearing roomies. The WA5LE, on the other hand, is the headphone-only version of that amp. Both use more or less the same topology and leverage the same tube set. Both are built like tanks, and if thrown at one, will cause mayhem. Not surprisingly, they command prices commensurate with their capabilities and build. They’re big. They’re bad-ass. They’re legend.

And now, they’re different. Frank is gonna be pissed.

“Back in the day”, either the WA5 or the WA5LE could be factory-upgraded. That is, if you wanted to spring for the extra $1200, you could (at ordering time) get the “standard” guts swapped for a whole mess o’ better, featuring “audiophile-grade” capacitors. The difference is supposed to be significant, but given the performance of the “standard” unit, this sort of upgrade will always evoke punctuation marks. “Will I hear it? Will it be worth it?” are two questions that I’m sure the folks at Woo are completely sick of hearing.

So, what’s new? Well, with the WA5, the base price is now $5899. Don’t faint — this includes the “audiophile grade” internals update as standard. The WA5 is clearly meant to be a flagship-level product, and the updated best-they-can-come-up-with internals now reflect that.

Which brings me to the new WA5LE. The base price on this model is $3699. Don’t faint — this does not include the internals update as standard — that’s another $1200. Does that mean the WA5LE is not a flagship-level product?

I think it is one — but one with two levels of “pain sensitivity”. You got the cash? There is an obvious choice. You no-gots-the-cash (which would be me, just so we’re clear), you no have to go all-in to get your 300b fix. And remember, if price is your primary driver, there are plenty of other options from Woo Audio to help you out.

Okay, so that’s that. But that’s not all.

On the face of it

Aside from the all-new internals, and the new XLR input and output (convenience only — the units are still single-ended) for either model, owners of either can now fully indulge their late-onset OCD when it comes to their headphones. I mean that pretty much as it sounds. With the new units, there are … options.

Probably the first thing you’ll notice is a set of switches on the front panel. The old panel had two 1/4″ phono plugs (high and low impedance outputs), a volume knob, and an input selector. The new fascia adds … things. Ha ha! Knobs and toggles, oh boy!

These things are there for one purpose only — to “tune” the amp (which now puts out an extraordinary 8 watts per channel) to best fit the headphones you’re using today, and have the flexibility to change the amp’s capabilities for the headphones you’re going to use later today. Or tomorrow. Or next week. Or last week, you time-traveling devil you. Whatever. The point is, the amp is crazily customizable. And that is the big change over the outgoing model, and the main reason for the price hike.

Off to the left, next to the now-standard XLR output, is a chunky knob that’s very helpfully marked “Power”. I like power. Moarrr powah! The knob has three positions: speaker, high and low. On the WA5LE, the ‘speaker’ option is unavailable/can’t be selected (this is reserved for the WA5, but the WA5LE and WA5 share a faceplate), but the high/low can be. Select ‘high’ and the amp gives you all she’s got — 8 watts per channel. In case you were wondering, this is a stunning amount for a headphone amplifier — but with great power comes great responsibility, so please be careful. Select ‘low’ and the secondary circuit topology is selected, yielding a total output of 1.5 watts/channel. I know, this seems anathema, but trust me when I say that not every headphone is going to respond optimally to strapping on jet engines. Caution — do not turn this knob while your amp is on and your headphones are connected. If you do, there will be a loud-as-a-freaking-cannon-shot POP that will come through your headphones. Turning down the volume will not help — unplug the cans first. Save yourself. Save your headphones. Capiche?

To the right of ‘Power’ is a small toggle for ‘Impedance’. On the old WA5LE, this was implemented as a pair of 1/4″ jacks; here, it’s a toggle and cuts across both jacks. The rule of thumb is this — select ‘H’ (for “high”) for cans over 100Ω; select ‘L’ (for “low”) for cans under 100Ω. And I’m serious about the “rule of thumb” comment — this is not written in stone. Try it out. This one, you can select while the amp is on and the headphones are connected.

Dead center of the amp? The volume knob. Just as big, fat and knobby as you’ve come to love. It’s fun to touch. To turn, ever so slowly. To caress. To let your fingers linger on, perhaps a hair to long. Oh, it’s a big one all right. Rowwr!

To the right of that is ‘Level’ setting. Level? Yes, Level. Not output, mind, but input — this is where you start tweaking for those high-sensitivity headphones. Selecting ‘L’ (for “low”) will shunt more than 50% of the input, which happens before the gain stages. Again, if you think “hiss” could be an issue with your (think: high-sensitivity) cans, this is the toggle you want to fiddle with. Selecting ‘H’ (for “high”) lets everything through.

To the right of ‘Level’ is the input selector, and there are three that you can wire into the amp.

Last but not least, and all the way to the left on the face of the amp, is the 1/4″ phono plug for your SE headphones. And yes, both it and the XLR jacks are simultaneously “live”.

Sound

So, how does the amp sound? In a word, “full”. Unpacking that is a little difficult, and will depend in no small part on the tubes used. With the best tubes, I got the best sound. Staggering insight there, right? That’s how we roll. But perhaps I ought to say rather that the WA5LE is an open platform on which to play with sonic signatures — and it’s clearly transparent enough that such play can have dramatic impact.

For example, take the 300b power tube. That tube has a stereotypical signature, that by most accounts is best described as “lush”. But “lush” is not a sin-free descriptor — the 300b is also usually portrayed as bass-shy and treble-less, which makes the mid-range stand out all that much more. A common (and apparently contrarian) comment about a “modern” 300b amp is, therefore, that there’s “good bass” (whatever that means) and air (where that is taken to mean “treble”). These comments are always offered with a flair (surprise!), as if to say that these features are impossible because it is a 300b-based amplifier.

Let me assure you: they’re not impossible. But given that the tube was originally designed to amplify telephone signals, perhaps it’s not surprising that commenters assume the worst. But lo! Let me assure you — those days are long past. Designers leveraging the 300b in their designs have realized that there’s more to the audio story than 400-3400Hz, so learning that 300b-based amps can and do (at last these days) hit hard both very low and very high shouldn’t be surprising. Case in point? Ta da! The Woo Audio WA5LE.

Treble, during my use, was generally pleasant and non-fatiguing. Being more specific than that, however, depends on the tubes I used (more on that in the next section), and could be grainy or brilliantly colored. Be warned — before you explore tube rolling, have a budget predefined. You can go bananas, pretty easy.

On the other end of the spectrum, I found the bass. Real, thumpy, subterranean cave-dwelling stuff. On the whole, I found that the bass performance tended to vary less by-tube than the top-end did, which was interesting. Assuming that the headphones could “go there”, and that the match was good enough to drive those headphones appropriately into the down-low (separate issues, those, even if they’re related), I heard bass that tended to be looser and more organic than what I heard with my solid-state amps. With the best matches, I heard electronica that rivaled anything I could have produced on an all-solid-state setup. With the less-good matches, things strayed toward “fleshy” but never hit “soft”.

We good so far? Yes, these are general comments. So, lets talk about tubes.

Tubes

At the risk of being painfully obvious, the best things about a tube amp are the tubes. It’s kinda in the rule book: reviews of tube amps include some comments about the thermionic options. Happily, Woo Audio offers lots of such options.

The default tube complement is from Shu Guang (or Shuguang, but the box has the two parts separated), and the best thing I can say is that they’re cheap. As in free. They’re included, and yes, they do let the amp make sounds. For funsies, my review unit also came with an alternate set of tubes: Sophia Electric mesh-plate 300b tubes ($385/pair), Sylvania 6SN7GT NOS tubes ($330/pair) and Sophia Princess Mesh Plate 274B ($320/pair).

Of these (or maybe not), the tubes that made the most impact were the 300b tubes. The Sylvania (driver tubes) were next. The 274B rectifiers, last. With the Sophia Electric mesh plate 300b, the sound stage opened, grain dramatically dropped and tonal colors emerged from what had been a grayish sonic tapestry. The Sylvanias added some more color and mid-range lushness. The 274B improved bass response. Not much. Some. Almost a tweak.

I will offer that my favorite improvements to this amp came from a further upgrade — a pair of Takatsuki TA300b tubes, available for an additional and shocking $1620/pair (with 12 month warranty). The difference between these tubes and the stock tubes were … enormous. With the Taks, the amp was a wholly different experience. After this comparison, I packed up the Shu Guang tubes and never touched them again. Compared to the Sophia Electric 300b tubes, the Taks were holographic, grainless, and extraordinarily extended in both bass and in treble. I have a very hard time recommending these tubes, given their price, but I will sheepishly also offer that I have not found another current-production tube that is better. If you know anything about 300b tubes, please understand that I’m aware of the current panoply and will cheerfully reiterate that claim, regardless of how wide you want to extend the context. The TA300b is the best there is.

That isn’t to say that there maybe isn’t better out there, however. I also have a pair of late-production Western Electric tubes that I swapped into the amp. These tubes are not current production (insert hysterical weeping and gnashing of teeth) and also typically start at well over $2k/pair on eBay. Yikes. I typically run my pair in my $26k SET tube amplifier from BorderPatrol, and they are big and bold and dense and OMFG are they amazing. I love ’em. They’re the berries. They’re that and a bag of chips. Did I mention that I love ’em? I’m sure I did. Also, they’re not the best vintage 300b tube you can secure from the Internet. Yes, there are better and worse vintages for WE tubes. Is that weird? I think so. Anyway, that said, the Taks are not worse. They are different — leaner, perhaps, but more extended in both directions and also faster/tighter in the bass. Sonically, I actually preferred the Taks in the Woo amp over the WE tubes. Blasphemy? Maybe. But I prefer the term ‘synergy’. The pairing with the planar-magnetic headphones from Audeze and HiFiMAN were superior in every way with the Taks. Interestingly (or not), turning to the Sennheiser HD800 and Abyss AB1266, I found the WE tubes to be more salubrious. In neither case, however, was I convinced of needing either mega-tube to make this amp “work” or listenable, so don’t take this the wrong way. I’m simply offering that if/when you’re ready, your Woo Audio WA5/WA5LE can be straightforwardly improved — and for the record, Woo Audio is offering a sweet deal on a pair of warrantied TA300b tubes.

Most of my listening was performed with the very capable and highly recommended Sophia Electric mesh-plate 300b upgrade.

Comparisons

I compared the WA5LE v2 to the Cavalli Audio Liquid Gold and the WA5LE v1. Lets start with the lattermost, first.

Fight: WA 5 LE v1

Being able to compare the new amp versus the old one was, honestly, the only reason I agreed to do this review. I wanted to hear, pretty much on an instant, what the new amp brought to the table over the old one.

The answer, in short, is not a lot.

Now, don’t take that wrong. The WA5LE v1 had a lot. Dramatically improving it isn’t likely — that amp is most decidedly not broken. Sonically, it has big brassy ones. There’s nuance, there’s tone, there’s bass, there’s sex. It’s a great amp. Did I mention that it is entirely non-fatiguing? It’s an all-day, easy to use, reality escape-hatch and it’s going to catch a boat-load of wide-eyed looks wherever it sits. The answer to the question, “What is that thing”, never evoked the “You are clearly insane” recoil that expensive audio gear typically earns from the unwashed. Folks look at it and say, “Really?” It looks expensive — better, it sounds it, too.

What the WA5LE v2 does? It keeps all that great stuff. And then takes a clear, clean, step forward.

It is almost assuredly the ability to better tailor itself to headphones that makes this possible. Performance will always vary by headphone — simple/single-configuration amplifiers will perform differently with every headphone they’re asked to drive. They have to. They only do the one thing. But the WA5LE v2 does not do the one thing. It does a lot of things. For every headphone I tried.

They sent me this handy chart, which lays out some of the recommended configurations for some of the more common high-end cans.

Starting from the bottom, with the Sennheiser HD800, a pair of headphones that many have told me are the greatest available. I’m a little less than convinced of that, but I take it that this is an issue of personal preference. I like my sonic tableau to have a bit more meat on the bones and a lot more juice in the caboose. To me, the HD800 have usually come off as a little threadbare, a little fatiguing and a little light on their feet. Big tubes tend to help a lot. But the difference between the WA5LE v1 and v2, with these headphones dialed in low-power + high-impedance + low-level, was hard to pick out. That said, what I heard here was among the very best presentations for this headphone. Treble was very even and altogether pleasing — there’s a long-term use issue that is a legitimate complaint for this headphone, in my view, and here, with the WA5LE v2, I found it all-silk and no-spike. Bass, an issue with these headphones pretty much always, was still an issue.

The next few cans reacted differently to power & level — options not available on the WA5LE v1.

I got more mileage when using the new HE1000 headphones from HiFiMAN than with the old Senns. These new HiFiMAN cans are delightful. Dialed in as high+low+high, the sound was full and meaty, and a good deal more “open” and punchy on the v2 WA5LE. How so? Take Lorde. The HD Tracks 24/96 version of Pure Heroine is a great version of a great album. Assuming you’re down with pop, that is. As her producers tend to be really down with the massive bass tracks, it’s also an interesting album to fiddle with. On “Royals”, there are several passages that can track lower than the Sennheisers can clearly articulate — the bass becomes a bit one-note and indistinctly “deep”. With the HE1000, there’s more reach, and there’s actual texture — it’s two-note. Okay, maybe three-note. Look, it’s pop, what do you want? Some fantastic sound, here.

The Audeze LCD3-Fazor, which the chart suggested I dial in as low+low+low, I didn’t like so much at first on either amp. Okay, that’s too strong. Especially on the v2 amp, I found I was spinning the volume dial way over, and still reaching for that last bit of slam even as the overall volume went past my personal comfort zone. I found that flipping the ‘Level’ up to ‘high’ helped immeasurably — and I was able to keep the volume knob comfortably under that midpoint, where it not only became too loud, but where hiss also started to creep in. Less play with the knob, of course, but there was just more fun with what I had. The Audeze, and the HiFiMAN — and maybe planars, generally — really don’t come “alive” until they’re well-fed.

I found that trend continued with the Fostex TH900RP headphones. Another low+low+low headphone, and ostensibly more sensitive than the Audeze (100dB to the 93dB Audeze), the TH900 did react better with the ‘low’ Level setting than the Audeze, and I could achieve “interesting” by cranking things over to 3 o’clock on the dial. After my experience with the Audeze, however, I flipped things over to ‘high’ on ‘Level’, and that got me more jump, and faster, but I ran out of dial really fast — 9 o’clock was now concert-level. Still, this was a worthy combo and big fun.

Fight: Cavalli Audio Liquid Gold

Normally, headphone amps hate the Abyss AB1266 — they’re low-sensitivity power-hogs — but when they’re fed a high-octane diet, the rewards are unparalleled. Say what you want about the Hells Angels aesthetic, but the fact is, these guys have bass that every other headphone only dreams about. In my experience, they are the best there is, was, and may yet be for the aspiring bass-head.

I dialed them into the WA5LE v2 as low-impedance, high-power and high-level, and … skadoosh. In many ways, this is the best that I’ve heard these headphones. With their relatively low sensitivity and massive drivers, the Abyss produced astonishing bass and a soundstage of stunning width and depth.

Prior to the WA5LE v2, the only amp to really do the Abyss justice was the Cavalli Audio Liquid Gold (aka, the LAu). Sure, I’ve been able to make those headphones do interesting things — they’re not impossible to drive — but with power, they tend to come on-song. Again, it’s a planar-thing. Now, I reviewed the Liquid Gold a year ago, and I’m still impressed with its effortless handling of some of the world’s most devilish headphones, specifically and most especially, this particular pair.

It’s extremely rare to find a pair of headphones that don’t translate “great bass” as “bloated mess”, but to get the best transient attack across the frequency spectrum (and not just in the treble, say) requires a special amp. With adequate power, the Abyss dance. The WA5LE pretty much matches the LAu watt for watt, and both amps drove the Abyss. No questions there. Both produced prodigious bass response, where “prodigious” equals “will scare you”. Where the LAu and the WA5LE v2 separated was in bass texture. Generally, I felt that the LAu handled the lowest registers more firmly, more forcefully and more cleanly. Bass attack was sharper and more startling. That continued all the way up the register — at each point in the frequency climb, the LAu presented a bit more sharply, with a bit more bite. But there was a point, in the treble particularly, where that wasn’t exactly welcome.

The WA5LE v2 was, admittedly, softer in the bass than the LAu when driving the Abyss, but decay was natural and, on the whole, longer. I took that to also mean that the noise-floor was lower. The difference wasn’t in any way upsetting — electronica hit harder on the LAu, timpani hit with more fullness and scope on the WA5LE v2. Electronica on the WA5LE v2, however, was awesome. Daft Punk’s “Derezzed”, from their TRON soundtrack (played back on my Big Rig vinyl system), jellified my gray matter in a manner that had me dropping things for a week. Put on an arbitrary scale, I think the LAu would rate higher on bass, with the WA5LE trailing closely (depending on tubes). But flipped around, I would rate the WA5LE higher than the LAu on treble and midrange (again, depending on tubes). Given that I think the LAu and the Abyss were “best in class” at bass reproduction, the performance of the the WA5LE v2 was eye-opening in a white-all-the-way-around sort of way. “Epic” was what my notes said.

The WA5LE v2 surprised me most in long-term listening. I found that the Woo Audio amp was engaging in a way that the LAu wasn’t quite. Part of it had to do with the gentling effect that the tubes had on that headphones’ sometimes uneven high-end. Quite a lot, perhaps. Part of it had to do with the immersive quality that voices took on. There was something that the Sophia Electric/Sylvania tubes did with the Abyss headphones (and the Fostex) that I found quite magical. Take as a whole, this was another best-in-class combo, and brilliant. This pairing reminded me of some of the very-best 2-channel stereo presentations I’ve heard.

Stepping back from the Abyss, I want to note that the LAu also drives the snot out of my Sennheisers and my Audezes. These headphones clearly respond well to power, and as I noted in the LAu review, these pairings were quite special in their own way. The issue, perhaps, is that the Liquid Gold is not exactly a quiet amplifier. Run some high-sensitivity headphones through it, at moderate volume, and you’ll hear some low-level hash in the quiet bits between gobsmacking sonic tsunamis. Not so much an issue with the Abyss or the Audeze, but with the Senns, it was (a minor) one. The LAu is very clearly designed to do one thing particularly well — drive big cans. That said, I found it worked really well with headphones that really need sumpin’ sumpin’ to not sound boring — like the Senns — or that were already fulsome — like the Audeze. The Sophia Electric/Sylvania upgrades in the WA5LE amp tend toward fulsome on their own; I wouldn’t be surprised to find that fulsome can-fans would find this combination to be too much of a good thing. This is totally fixable — my recommendation would be to try some Gold Lion drivers and Emission Labs power tubes (or Taks, if you’ve got room for those in the budget) and ka-boom.

And that, friends, is the joy of a great tube amplifier.

Conclusion

The WA5LE may be the most versatile and pleasurable headphone amp I’ve used. Every headphone I threw at it, it caught and made sound extraordinary. Some headphones have sounded better with other amps, but usually along only one of several parameters, and no one amp has made this many great headphones sound as good as they can be. That’s another way of saying “some amps suck at certain headphones”, but the WA5LE is very good to great with every headphone I used. That’s unique, in my experience.

The downsides are pretty obvious — size, weight, and cost. These amps are in no way compact! The company says that to do what they do with the amps requires big iron and lots of space, and to be fair, the sonic result is very hard to argue with. Unfortunately, that means the WA5LE v2 is going to need space and lots of it. Desktop bound, it isn’t.

The bit about cost is likewise unavoidable. In the opener, I mentioned that Woo Audio does offer a whole suite of solutions targeting price-sensitive buyers, so it’s not exactly fair to hang that on one of their flagship products.

Ultimately, I have to say that this is the amp to lust after. Assuming you’re hot for tubes, like me. And that means an Editor’s Recommendation.

Associated Equipment

Digital: AURALiC Vega DAC

Analog: TW Acustic Raven AC-3 turntable, with Raven 10.5 tonearm and Miyajima Madake cartridge, played into an Luminous Audio Arion phonostage

Amplifier: Cavalli Audio Liquid Gold (LAu)

Headphones: Abyss AB-1266, Fostex TH900RP, Audeze LCD3-Fazor, HiFiMAN HE-1000

Cables: Triode Wire Labs Seven+ power cords and WyWires Platinum interconnects.