Woo Audio WA6 SE Review and Measurements

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by purr1n, Sep 15, 2020.

  1. purr1n

    purr1n Finding his inner redneck

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    I've been tied up with other stuff lately so this will have to be one of those stream of conscious type reviews. Thanks to @ogodei for loaning this out.

    In short, this is the tube amp that I had wished I had started out with when I was near the beginning of my headphone audio journey many many ago. I instead went in a few other directions from all the HF buzz - all the wrong directions - but this is a solid entry level transformer coupled tube amp. (Note that this is the first version that uses 6DE7 tubes).

    IMG_20200915_153324_238.jpg

    Honestly, I don't think there can really be such a thing as a bad sounding output transformer coupled tube amp. What is comes down to to how much performance do we get for the price. At $1300, the Woo Audio WA6 SE is high value. I'm still kicking myself for going off in various random directions early in my journey. I remember reading about the WA6 SE on HF and almost pulled the trigger. (BTW, the construction of the chassis is bonkers solid.)

    First of all, I do not like warmpoo or excessively bloomy or wet tube amps. The WA6 SE is in the vein of the more solid-state sounding tube amp category. I also tend to dislike almost all OTL designs (except for one) as their higher output impedance, sometimes excessively high output impedance, wreaks havoc on Grados or even the HD650 frequency and transient response. Finally, big caps just suck no matter how much you cut it. There's always going to be a certain capacitor veil. This is why I prefer output transformer designs. Heck, I can at least use lower impedance planars of decent efficiency. On this thought, it was the Feliks amps I had reviewed in the past (https://www.superbestaudiofriends.org/index.php?threads/feliks-audio-elise-tube-amp-review-not.2260/) that made me think of the WA6 SE as an output transformer coupled alternative to cheap OTL (output transformer-less - that is a big cap). Sadly, Feliks has increased their prices massively because of HF exposure that I no longer feel they are a good value.

    One thing I should get out of way first: with some of the tubes, there may be some hum with super efficient Grados. Even in the best case scenario with quiet tubes, there may still be some barely audible hum with Grados. The tube types that can be used are super high gain. I don't think I've gone past the 0930 position on the volume knob even with the less sensitivity HD650s. (The knob starts at the 0630 position, so there is plenty of room).

    OUTPUT IMPEDANCE: https://www.superbestaudiofriends.o...-se-review-and-measurements.9897/#post-318167
    RECTIFIER TUBE ROLLING: https://www.superbestaudiofriends.o...view-and-measurements.9897/page-2#post-318318
    COMPARISON TO OTHER OPT SET AMPS: https://www.superbestaudiofriends.o...view-and-measurements.9897/page-2#post-318264
    LESSONS FROM CYRO'd TUBE: https://www.superbestaudiofriends.o...view-and-measurements.9897/page-2#post-318728
    GAIN AND NOISE (HUM): https://www.superbestaudiofriends.o...view-and-measurements.9897/page-3#post-318733
    DISTORTION MEASUREMENTS: https://www.superbestaudiofriends.o...view-and-measurements.9897/page-3#post-318742
     
    Last edited: Sep 21, 2020 at 12:53 PM
  2. purr1n

    purr1n Finding his inner redneck

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    The 6DE7 tube type is kind of funky. It's a dual triode with each triode being slightly different. One is a high gain with high plate resistance, the other is low gain with low plate resistance (suitable for coupling to an output transformer). I had originally thought it was a spud amp (single tube for driver/gain and output), but it turns out this was wasn't true. The second generation uses the 13DE7 with the 13V filament. This first generation uses the 6.3V tubes.

    The different plates of the triodes can be seen below. Wierd huh? (I guess there a reason for this: ancient TVs).
    IMG_20200915_160405.jpg

    I did not have any 6DE7s on hand. However, I did have various compatible 6DR7 and 6FD7s. The ones with the yellow lettering are Sylvania 6DR7s which I preferred. The bass is less fat and the higher less coarse. The 6FD7s came in two varieties, a fatter tube and a skinnier tube. Regardless of the glass size, these two in general sounded more similar to each other than the Sylvania 6DR7s. The bass was fatter and with the highs were coarser with a little bit of upper-mid aggressiveness that did not gel with with the HD650 and Gungnir A2 DAC. I'm not going to too much into tube rolling, but at least this might give you guys a general idea.

    The rectifier tube is a special 596 on an adapter. I don't know if I am a big fan of the semi-exposed pins attached to the plates. I believe that Woo Audio sells this for $350. I don't know of this is necessary and will try to find a cheap 5U4G and report back. I would be curious how much of the amp's awesomeness is due to the 596. I would certainly hope that I don't like the amp because of the 596 and that a run-of-the-mill 5U4G can do a decent job. The 5U4G can be found readily for reasonable prices. The amp will also take the 274B. However, the 274B will have more voltage drop than the 5U4G (and probably the 596).

    IMG_20200915_162410.jpg

    As an aside, I have some doubts about any special-ness of rectifiers based on their brand or manufacture date. The problem is that in 2020, we have no idea of the wear and tear these rectifiers have experienced. Any comparison should be done in a way where the voltage after the drop is taken into account.
     
    Last edited: Sep 15, 2020
  3. ogodei

    ogodei Headphone Heaven Gatekeeper

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    I believe the top pins on the 596 are the anodes so they would have been for reliability / prevent arcing for Military applications. United Electronics made boatloads of these for the Air Force and I believe Woo latched on to a huge cache of "NOS" military stock a long time back. I suspect that by featuring the tube's 'cool' looks with pins\wires they created a great new profit center for themselves.

    274A or B in this amp is very nice as well.
     
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  4. purr1n

    purr1n Finding his inner redneck

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    Wondering if there is something just a little bit more relaxed or softer sounding with either rectifier or triodes. This is working very with with the Verite Closed, which I prefer with solid-state amps.

    The mids are surprisingly super clear - no OTL cap veil. The do lows get slightly congested at high volume compared to TOTL big-boy tube amps - but it's magnitudes better than something like the NBT / ZDT Jr which is murkier. There's a little of bloom, just the right amount. From a technicality POV, everything is very good: detail retrieval, slam, etc. I haven't encountered anything that it does poorly or even average. Maybe headstage could have a bit more depth, layering could be more complex, or microdynamics could be more expressive - but I'm asking too much for the price. (It's hard having heard very good tube amp references).
     
    Last edited: Sep 15, 2020
  5. ogodei

    ogodei Headphone Heaven Gatekeeper

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  6. purr1n

    purr1n Finding his inner redneck

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    Purchased.
     
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  7. YMO

    YMO it's not drinking alone if you're on Zoom

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    I had this amp a few years ago. It was the Second revision one in black. I put in the Brimar-5Z4G Rectifier when I had mine and it was a minor improvement over the stock one. My issue when I had my WA6-SE was it was kind of I dunno, slowish and fatish?

    It was great when I had my LCD2C, but I guess I got bored of the sound after awhile. Tons of power for those planars that isn't something crazy like a HE-6 or something. I never thought when I had my WA6-SE that it was very solid state sounding.

    I do have a bias here. At the time I purchased an Ayre Codex and I liked the Codex so much that I started to use the Ayre/Pono-style balanced inputs of my LCD2C and my Clear into the Codex. Clear sounded better on that Codex, but LCD2C lost some of that bass.

    I think for some people it is a very solid option. @will_f like his.
     
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  8. purr1n

    purr1n Finding his inner redneck

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    Yeah. Prior WA6 SE I've heard did sound softer and warmer/laid-back in a nice way. Could be this rectifier or maybe these specific 6DR7s.

    The other possibility is that the planars no matter what are wanting more power, thus you getting a softer sound with LCD2C.

    Will take measurements and see.
     
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  9. will_f

    will_f Leave of absence from SBAF - having fun in RL

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    IME the 2nd generation sounds better with Sylvania 13DR7s than the stock tubes, being very clean and sweet sounding. I’ve also tried a couple Philco 13FD7s which definitely make the bass fatter And take away a little sweetness from the treble but I’ve grown to like them.

    I also think the rectifier does make a difference. When I compared the stock rectifier to the Sophia it sounded (to me anyway) less clear and a little muffled, which I guess could also be interpreted as softer. I also tried and am currently using a 1940s RCA hanging filament 5U4G that I really like. It seems to give a touch of richness to the lower frequencies that makes the sound very engaging.

    Without the ability to A-B tubes quickly, I could be fooling myself, but It’s reassuring to see @purr1n has a similar impression with 6DR7 and 6FD7 tubes in the Gen 1 model.

    I do think my Lyr3 does a better job with my Aeon Flow Closed. IMHO less dynamic with a little roll off at the bottom when powered by the Woo. That said, the Woo creates a little magic with a decent pair of dynamic drivers that the Lyr doesn’t quite match.
     
    Last edited: Sep 15, 2020
  10. ChaChaRealSmooth

    ChaChaRealSmooth SBAF Gearmaster

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    Quick tip; don't ever compare things real quick back-to-back. Fastest way to guarantee you won't hear a difference and induce fatigue.

    ^this is 100% true. I say this as someone who owns a Euforia. Is it good? Yeah, I like it for what it's supposed to be (a warmpoo tube OTL). But I can't recommend it for the price unless you really like that kind of sound, willing to find synergistic pairings, and willing to roll some tubes.

    I'm curious about the WA6-SE since it exists in no man's land in terms of price. Wonder if it could actually belong in its price.
     
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  11. purr1n

    purr1n Finding his inner redneck

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    It's one of the few pieces of gear that I truly feel belongs here as a recommendation, even moreso than the Oblivion amp (discussed and reviewed). although their presentations are somewhat different. The WA6 SE is a SET amp. Any decent SET is going to have a quality which makes will make it hard to put the headphones down. The presentation is more Eddie Current than Woo if that makes any sense. At times, it's fooled for me for the custom 45 Studio, that is until I put on some good recordings and actually listen to the 45 Studio. The 45 Studio sucks me it and makes it so impossible for me put down the headphones so I never use it during the day. The WA6 SE SE has the same quality - not to that extent - but close.

    I think what it comes down to is most gear in no-man's land, say $1000-$2000 tend to be no better than $500 gear. This isn't the case here.

    Now I did notice something from Woo: this amp will support 6SN7 with an adapter. The 6SN7 is dual triode with same characteristics for each. Both triodes have usable plate resistance for the output transformers. The 6SN7 is a great sounding tube and spanks any 9-pin if high gain isn't needed. This could be the fantastic combination - the more robust and expansive sound I was be looking for - as well as much a needed reduction in gain for better usable range on the volume knob. I just ordered some adapters and will report back.

    Confirmed. The WA6 SE may be a little bit on the soft side with lower impedance planar / medium efficiency planars. I hope I did the numbers right below. FWIW, I did not like any headphones (dynamics, planars, or otherwie) from the high Z jack. 53-ohms is too warm, too colored, for dynamics, and too soft for planars. I actually did not care for any planars on this amp, even medium efficiency or higher ones. Too much of the power being wasted as heat and not being used to power the planar. The 18-ohms is within the sweet spot range for many dynamics though (Sennheisers, Focal, etc.)

    Output impedance measurements using 32.4-ohm resistor at 1kHz.

    Low Z jack output impedance: 18-ohms
    0.372Vrms open
    0.238Vrms with load

    High Z jack output impedance: 53-ohms
    0.744Vrms open
    0.282Vrms with load
     
    Last edited: Sep 16, 2020
  12. YMO

    YMO it's not drinking alone if you're on Zoom

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    Thanks @purr1n. I didn't do enough research on my end when I had my WA6-SE years back. Back then I was kind of on the balanced or go home bandwagon, which is why I did the Ayre Codex. From that perspective I do put my comments on my own experience of the WA6-SE to be on bias territory at the time. I did however remember when I had my Clear that it was a better match for the WA6-SE, just to get rid of that treble.
     
  13. purr1n

    purr1n Finding his inner redneck

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    I prefer planars from solid-state or tube amps that can pull off low-Z output impedance (2-ohms or less). Many others don't mind planars from higher Zout amps.

    --

    History lesson on Zout. I swear, I don't get credit for a lot of stuff that hobby knows today. Stuff like this is why Jude silently banned me from HF (I can log in, my account doesn't say banned, but I can't post threads and respond to PMs): https://www.head-fi.org/threads/mer...consciousness-review-warning-not-good.652910/

    Folks were all over how "awesome" the Meridian Exploder sounded. I know why: it sounded different to most, different enough to be interesting. It seemed that I was one of the few who thought it sounded like ass from the get-go. I could imagine folks plugging in their BA IEMs and saying "oh my, this is so good" because the super high output Z screwed up the FR so much that their IEMs actually sounded different. It was strange how after this reveal, people started to say other things about the Exploder.
     
    Last edited: Sep 17, 2020
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  14. will_f

    will_f Leave of absence from SBAF - having fun in RL

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    I learn something new every day.
     
  15. Lyander

    Lyander Too sensitive for SBAF

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    Especially when it comes to DACs, trying to suss differences out that way is how DAC naysayers get their biases affirmed ;)

    Well I've had this amp on my mind for a couple years now because of your comments about it from way back in the "Best Amps for the HD800" thread, @purr1n, just that I've never been able to get ears on the thing. Besides being worth north of $1k the thing just looks absolutely gorgeous, seems like a compelling pick!

    Your comments on the voicing make me think it might be a better match for the HD600 than the HD650 but that it'd be fine for the 300R Senns altogether. How might it fare with the hyper-sensitive kids like TH-6/9/X__ or HP-3? Gain not so obscenely high for moderate listening (~80dB peaks?) that something the like of a JBL Nano Patch is needed? I don't seem to mind the HP-3 out of higher impedance outs very much, though it's not ideal.

    Wondering how this fares against more sanely-priced SETs like the DNA Starlett for stuff like low-level detail rendering and headstage placement.
     
    Last edited: Sep 16, 2020
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  16. will_f

    will_f Leave of absence from SBAF - having fun in RL

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    curious about this myself.
     
  17. ChaChaRealSmooth

    ChaChaRealSmooth SBAF Gearmaster

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    Convince @purr1n to send it my way after he's done fiddling with it and I can tell you.
     
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  18. Lyander

    Lyander Too sensitive for SBAF

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    Forgot to hit send, whoops.

    Might be better off asking @ogodei first but yeah, curious what you might think of em too since I think we have similar-ish preferences and aren't too treble sensitive, haha. I honestly forgot for a second you owned a Starlett! Thought it was a Stratus for some reason.
     
  19. Ntbm3

    Ntbm3 Friend

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    I owned a WA6-SE gen2 and sold it to buy my Starlett.

    I had a couple frustrations with the Woo.
    1- The noise... always a little bit, some tubes very loud.. some not so bad but always there.
    2- Magic... not sure how to explain it but I was not consistently drawn in to listen like other amps I have had. It had great days, but others just felt a bit flat.

    love the build quality... I think the first gen is the one to have with the tube flexibility. Gen 2 output tubes were harder to find.

    The Starlett in comparison I found:
    1- Always sounds amazing... always...
    2- more transparency/micro detail
    3- more flexibility with outputs and impedance adjustment
    4- neon blue... love the color :)

    I have never thought about my previous amp since getting the DNA Starlett. Until this thread.

    Woo goo.jpg

    edit: slight comment correction after getting a chance to read through this again.
     
    Last edited: Sep 17, 2020
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  20. Yerim

    Yerim Rando

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    Isn't this available on our local audio store? If i remember correctly they were selling woo amps. I'm interested to know how this pairs with the HD800 SDR. If this is a big leap from the woo wa3 which i'm using currently with the hd800, I might start saving up for this.
     

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