Woo Audio - WA234 MONO (Mk2)

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by Torq, Mar 14, 2018.

  1. Torq

    Torq MOT: Headphone.com

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    Woo AudioWA234 MONO (Mk2)

    As a result of posting some poor-quality “iPhone-at-night type” shots of my WA234 MONO in the “Amplifier Porn” thread, I was asked to provide some insight to the unit. This’ll likely be somewhat episodic/SoC, and may, or may not, turn into an outright review of the unit, but we’ll see on that front … for now this and/or these post(s) will constitute those insights and thoughts etc.

    WA234-Tubes.jpg

    So, what exactly is the WA234 MONO?

    In short, it’s a pair of mono-block (one amp-per-channel) single-ended-triode driven, transformer-coupled amplifiers, operating in pure class-A, and capable of driving both headphones and speakers (up to 8w at 8 ohms), while utilizing 2A3, 300B or 45 type power tubes.

    To add to that, it’s a capability delivered with elegantly configurable output types/impedances, and delivered in a sumptuous, luxurious, chassis the form, and build, of which compete with the topmost echelons of the audio world.

    While the aesthetics may not be every one’s particular cup of tea, they are distinctive, rich, ridiculously well finished, luxurious and very … solid.

    How solid?

    I had to re-inforce my listening station to install my WA234 MONO. It’s predecessor, the Woo Audio WA5-LE was no lightweight at 70lb. But ... EACH of the two mono-block units that comprise a WA234 set weigh 60lbs.

    The “big Woos” are a commitment in multiple dimensions.



    For me, single-ended triodes are the “holy grail” of tube amplification. I’ll go further there. They’re the holy grail of low-power (<10 watts) amplification for me, period.

    And, nominally, when it comes to single-ended-triodes … I’m a “300B slut”.

    While I can fully appreciate the raw resolution and transparency of the 2A3, and the unique (and beguiling) tone of the 45, the 300B gives me most of my desires in both of those camps while delivering an absolutely liquid midrange and an overall sense of space and holography that I’ve not yet found elsewhere.

    How much of a 300B slut?

    I keep a set of 300B for photographic “pretties” (Sophia Electric Princess, punched-plate ... see picture below), a pair of Takatsuki’s for general listening, a pair of now-exhausted original WE 300Bs for display, and a set of good/strong original WE 300Bs for serious listening. And I have various others (KR, EML, Sovtek, VA, Svetlana, PSVANE ) for variety and/or other purposes (e.g. amplifier burn-in, comparison, completeness etc.).

    And I was on the list for new-production WE-300Bs about four seconds after I heard about them.

    Tubes.jpg

    I digress …

    --

    Context:

    All comments here are based on my “Mark 2” version of the Woo WA234 MONO. This has several internal updates and component upgrades versus the original, but the biggest change is the switch from using 6SN7 series signal/driver tubes to 13EM7.

    You could reasonably consider me to be a 6SN7 fan. My prior WA5-LE used them. To this point it has been my favorite driver/signal tube, with the possible exception of the 6922 family – specifically as implemented in the Decware Zen Taboo Mk 3 and 4. And, in that incarnation, it has been the fastest, most resolving, drive tube I’ve heard … until the 13EM7 in the WA234 MONO Mk2.

    But I’m digressing again …

    --

    Time from order to delivery was about 12 weeks.

    The WA234 MONO package arrives in three boxes. One each for the two amplifier units, and a third containing the stock-tube complement and the output and tube “switching keys” (more about which shortly).

    Just the packaging for these units, weighs more than some other actual components. I’m fairly sure if any of these units were dropped, the only casualty would be whatever they landed on.

    Fit and Finish:

    Fit and finish is nothing short of spectacular.

    High-end audio gets lambasted, and often rightly so, for excessively costly casework. First looks at the WA234 would tend to promote the same reaction. However, they’re simpler than they look. Essentially, they’re a stack of separate, but identical, plates. This greatly simplifies tooling and reduces cost, since once you can make one of these plates, you can just keep repeating it to finish up the amp.

    Now, I’m not saying this is “cheap”. They’re lavishly finished and look and feel fantastic. But it is definitely a more cost-effective approach than, say, trying to mill the entire thing out of a single block of aluminum.

    WA234 MONO Mk2 Details:

    This amplifier is unique (as far as I’m aware) among headphone amplifiers in a number of ways:
    • First, it’s implemented as a pair of mono-blocks*. In other words, there’s a completely separate PSU, amplifier, attenuator and chassis for each channel (perfect channel separation – any crosstalk isn’t coming from the amplifier).
    • Second, it allows the use of three different types of Single Ended Triodes, selectable via a plug that configures the amplifier for the tube you want to run.
    • Third, you can choose how the output is taken from the tubes (Plate or Cathode output) and, at the same time, elect for either high or low Z outputs. Plate-output yields higher power, Cathode-output gives a better sound.
    Power output is dependent on whether you’re using Plate Output or Cathode Output, Low or Hi Z and, of course, the impedance of your headphones. To quote the extremes, 300Bs in Plate/Lo-Z into 8 ohms will yield 8 watts, and 45s in Cathode/Lo-Z into 600 ohms will give you 40mW.

    Configuration and Setup:

    This is very straight-forward, once you have things unpacked and power cables and interconnects run.

    First, you choose what sort of power tubes you are going to use. As previously stated you can use 2A3, 300B or 45 series tubes. The unit is provided with “Tube Switching Keys”, which are short metal plugs, configured with tube-like pins, that determine which tube configuration you’re’ going to run.

    For my first outing with this amplifier I selected the 300B “Tube Switching Key” and plugged it into the “Tube” configuration socket. This is exactly like installing a tube in any “normal” tube amplifier.

    Next, you choose what output you want. There are several options, including “Speaker” and options for headphones for “Plate” or “Cathode” output at high or low Z (output impedance). I elected to take my first listen with the Focal Utopia and, accordingly, inserted the Cathode Output, Lo-Z “Output Switching Key” into the “Func” configuration socket.

    Note, you need to power-off the amplifier when switching/installing these keys.

    And THEN:

    Pressing the “on” button on each amplifier results in a roughly 20-second start-up/warm-up period. A softly glowing orange ring around each power-button will flash steadily, as some buzz/hum is briefly emitted from the headphones … which rapidly fades away … and then the rings stop flashing, there’s the click of the relays in each amplifier, and the headphones go silent.

    Absolutely silent.

    Headphones-not-plugged-in-silent.

    Black-button-lighting-up-black-on-a-black-background-levels-of-blackness.

    Utter …

    VOID.

    The first time I fired these babies up, I thought they’d shut down when the relays clicked, it was that quiet. And that’s compared not just to the WA5-LE Mk2, which I already considered to be extremely quiet, but also to the Pro iCAN. I’m used to there being some low-level noise, at full volume, with tube and/or tube-hybrid amplifiers. Residual “noise” was extremely minor with the WA5-LE Mk2, and quieter still with the Pro iCAN.

    It’s entirely absent with the WA234 MONO.

    Color me surprised.

    And quite delighted.

    This isn’t just the quietest tube amplifier I’ve had my hands on. It’s the quietest headphone amplifier I’ve heard, period. At least with full-size cans (even sensitive, low-impedance units).

    ---

    MORE TO FOLLOW ...

    ---
    *One quirk of this is that you have to adjust the volume for left and right channels independently. There are independent attenuators for each channel. Fortunately they are stepped (46 positions). Initially you'll be counting the steps as you adjust volume, but with a bit of time spent with the unit it becomes easy enough to eye-ball the positions of the volume indicators. Either way, it's not really a chore and you adapt to it within the first couple or three hours.
     
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  2. Torq

    Torq MOT: Headphone.com

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    Connecting Headphones:

    Most headphone amplifiers have very simple headphone connections. Typically, either a ¼” (6.35mm) or 1/8” (3.5mm) TRS jack. Sometimes there’s a balanced (or at least “dedicated/separate ground”) 4-pin XLR connection. Less-commonly still, but not really “rare” you’ll find dual-mono 3-pin XLR featured (WA234 MONO, original Schiit Audio “Mjolnir”, iFi Audio “Pro iCAN” and Eddie Current “Balancing Act” all offer(ed) such connections).

    The WA234 MONO sports dual-mono 3-pin XLR and 1/4” TS mono “combo” jacks.

    It ships with an adapter cable with two mono ¼” TS plugs to insert into the amps and a single conventional TRS jack into which you can plug normal ¼” TRS-terminated headphones. This is a very nicely finished setup (pictures to come) built with premium components. It allows you to get started listening via the WA234 MONO immediately.

    Mono-block construction should mean that, from an amplifier perspective at least, there’s ABSOLUTE channel separation. So, using headphone cables that keep completely separate signal and ground lines for each channel is, as far as I’m concerned, a fundamental part of the WA234 MONO experience. Both crosstalk and resolution should be improved in this situation.

    If you’ve ever looked at some of my DIY cable builds and wondered why I had dual 3-pin XLR terminations on them … well, now you’re probably getting an idea of why
     
  3. Torq

    Torq MOT: Headphone.com

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    Inputs:

    The WA234 MONO (Mk2) has three selectable inputs. Two are single-ended RCA, the third is a 3-pin XLR balanced-mono connection. You run the left-channel to one amplifier and the right to the other. This might be confusing at first as Input 1 is colored white and Input 2 is colored red on BOTH units.

    In short, you need one cable to each unit for each source.

    It is worth noting that the WA234 MONO is a SINGLE-ENDED amplifier*.

    There’s a LOT of nonsense in “Head-Fi” realms about single-ended vs. balanced amplifiers (and sources). Fundamentally, balanced operation is useful for long cable runs, where common-mode noise rejection is useful, and/or where additional differential power is required.

    In most cases, for the same level of raw “quality” or “performance”, a balanced solution will require twice the number of components, twice the complexity and likely somewhere close to double the cost of an equivalent single-ended design.

    Choose wisely.

    Since the WA234 is a single-ended amplifier, the “balanced 3-pin XLR inputs” are for convenience. They won’t sound better than the single-ended RCA connections. And they go through a transformer to convert from balanced to single-ended operation (this is true, in reverse, for the headphone outputs too). In general operation I’ve not been able to make an audible distinction between RCA and XLR connections … so use whatever is most convenient for you.

    For me that’s the XLR connections on both input and output.

    --
    *Hence the name Single-Ended Triode!
     
  4. Xecuter

    Xecuter Brush and floss your amp twice a day

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    I don't understand why they don't just optimise for 300b. Since it's configurable to three different power tubes using a single pair of transformer you are always compromising on the one thing you should never compromise on in an end game tube amp.. the Transformers..
     
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  5. Torq

    Torq MOT: Headphone.com

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    I'm not so sure the optimization isn't for the 300B ... this is easily the best 300B headphone-capable amplifier I've heard. Not to mention the best headphone amplifier that's crossed my path to date in any form.

    Beyond that, electrically, it's about having the appropriate windings and taps (and core materials and configuration), and nothing stops you having multiple taps for different purposes on a single transformer. That's not to say that this is necessarily the last word in that regard, but at least personally I haven't heard better elsewhere.
     
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  6. Xecuter

    Xecuter Brush and floss your amp twice a day

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    I'll have to hear the new wa234. The wa33 (non EE) was probably the best amp I've heard from woo and was leaps and bounds better than wa234 and wa5.
    Even so the wa33 is limited by what drivers (edit) you can roll (basically none) and the EE introduces too much woo goo.
     
    Last edited: Mar 14, 2018
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  7. Torq

    Torq MOT: Headphone.com

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    I will say that I think the EC Studio edges out the WA234 if we're talking 2A3 tubes. And at half the price. But even so, I prefer the 300B to the 2A3 ... which might be a purely personal thing, but is what it is.

    WA33 seems like an efficient way to spend twice what I'd need to for equivalent 2A3 performance just to claim "balanced" operation. But, again, all things being equal I prefer 300B to 2A3.

    Don't know about the WA33 EE ... but if there's any "goo" (of any form) to the WA234 Mk2 w/ my 300Bs then I'm not hearing it. It's the cleanest, quietest, most-resolving, dynamic headphone amplifier I've heard so far. If it wasn't, I'd have spent my money elsewhere ... it's not like the alternatives are more expensive here.
     
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  8. khragon

    khragon Acquaintance

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    What are the Mk2 changes compared to Mk1?
     
  9. Torq

    Torq MOT: Headphone.com

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    The big (obvious) one is a switch from 6SN7 driver/signal tubes to 13ME7.

    Beyond that a variety of internal changes and component upgrades, the specifics of which I don't have.
     
  10. Torq

    Torq MOT: Headphone.com

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    Beyond this talk of nonsensically expensive gear (>$50K for a single headphone-centric listening station)... interestingly (or perhaps not), my "day job" rig remains an Yggdrasil Analog 2 -> Ragnarok setup.

    I find no fault with that rig, nor any lack of satisfaction.
     
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  11. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    I think I heard these at Innerfidelity Big Sound and thought they were kind of bad. Maybe tube choice. I dunno. They were at least ultra annoying to use.

    Edit: Not sure if they were mk1 or 2, but my interest is still 0.
     
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  12. Torq

    Torq MOT: Headphone.com

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    Based on when you did that, definitely would have been the Mk1.

    Not that this means you'd like the Mk2 any better.

    And it wouldn't change how they worked/the usage model in either case.

    I don't know, maybe I should go through all the posts on here about different gear and say what my interest in each item is. Or not. Better still, maybe I should just stop sharing any of this stuff at all. That sounds like a much better plan, and way less effort to boot.
     
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  13. jexby

    jexby Posole Prince

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    settle. your contributions on SBAF have been appreciated, if not respected once time off the yacht permit.
    mere humans are not forced to bow at uber expensive rigs when they have heard similar/earlier revisions not to their liking.
    no big whup as SBAF is not in the game of producing clone-think. carry on as effort allows.
     
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  14. Vtory

    Vtory Illogical Spock

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    Am I the only one who are waiting for the "main" part of the stream (= sonic impression)?

    This is one of the gears I am probably never able to own for myself during whole life, therefore want to hear thoughts from honest guys. It's just pleasure to see non-commercialized and non-sponsored reviews for exotic/rare/uber audios, particularly so if such reviews come from experienced and skilled ears.

    Furthermore, I have some fantasy for this specific wa234mk2. Long time ago, 300B-based Cary integrated amp (300SEI), feeding hd600, was an eye-opening experience which led me to this hobby. Also heard WA5/5LE several times for recent years, and every time they wowed, amazed, or made me very jealousy. (I don't think Woo makes high-value products or their amps have high price-performance ratio. But I might like their sound when done it right) I am strongly guessing wa234-2 might be on the extension of this path.
     
    Last edited: Mar 14, 2018
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  15. purr1n

    purr1n Finding his inner redneck

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    There's should be an 300B EC coming out soon - sort of a AF without all the input and output options - more of a pure headamp. I haven't heard it yet. I'll ask Craig if I can go public with this. Oh wait. Oops.

    The WA33 is indeed the best Woo amp I've heard so far. Still, I was definitely NOT impressed given the price. I'd rather go DNA Super Stratus and five years worth of the finest whiskies. I'm drunk right now after karaoke night at Five Threads. You won't hear honesty from me like this these days, at least not publicly
     
    Last edited: Mar 14, 2018
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  16. purr1n

    purr1n Finding his inner redneck

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    300B and 2A3 have similar plate impedance. Filament for 300B is 5V as opposed to 2.5V for 2A3. The 300B is supposed to be doubled up 2A3. 45 has twice the plate impedance of 300B - probably the tube that the transformers aren't optimized for. Hard to say without knowing more - what the plate voltages are - or if they are slightly different for each tube.

    Curious about this too. Weren't there cap upgrade options like the V-Cap TFTF, which makes sense given the sound of the W234.

    The mk1 was a unimpressive at best, even if the price were $1750. I can easily publicly say this now that the mk1 is no longer available. The dual mono volume knobs are utterly retarded. I wouldn't have taken the mk1, even if it was offered to me for free. Seriously I'd rather use a Magni 3 or THX AAA. This is Googli gear. You guys remember Googli at HF right?
     
    Last edited: Mar 14, 2018
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  17. brencho

    brencho Friend

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    Tfw mono blocks for headphones... So uh how do they sound?
     
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  18. winders

    winders Know-it-all boomer, prob racist

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    After the mugging that has transpired here, I doubt we will ever find out.
     
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  19. brencho

    brencho Friend

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    Well we'll see I guess. If after 4000 words I don't know how these beasties sound then so be it...
     
  20. winders

    winders Know-it-all boomer, prob racist

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    Torq is not a dog. If you told me to "settle" I would be up in your face.

    Torq wasn't asking anyone to bow to anything or anyone. Someone asked him to post an evaluation of his WA234 Mono (Mk2) amps so he did. He even commented about how they were more expensive than they should be but did what he wanted them to do, specifically 300B tubes. All he did was explain why he thought it was the best headphone amp setup for him.

    And you guys crapped all over the amp as a way to thank him for taking his time to write something up.

    Well done!

    Edit: I am clearly not anywhere near the same level of enthusiast that Torq is, but the same shit happened to me when I posted about my preamp. When I get my new 2 channel tube amp, do you think I am going to risk getting shit on by posting a my views and opinions on it? Probably not.
     
    Last edited: Mar 15, 2018
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