Review: Woo Audio WA6 vs. WA6SE (stock units)

[Orcin]

My recent quest for a new amplifier eventually led to an exploration of tube amps under $1,000. As any experienced Head-Fi’er knows, “under $1,000” means $1,200 plus shipping. The Houston Head-Fi Meet was going to provide plenty of good amps to audition in the solid-state camp along with a few good tube amps in my price range. However, one solid company would not be represented: Woo Audio.

This absence was rectified (pun intended) with an email to Jack Wu, who promptly offered to send two demo units to the meet. I identified the WA6 as my primary target, and he also offered to send along the more expensive WA6SE. Like any good salesman, I presume he smelled blood in the water when I mentioned Head-Fi.

(I don’t want to move on without saying how pleasant and efficient it was to deal with Jack. I am confident that Woo Audio’s customer service is among the best that our hobby has to offer.)

The WA6SE improves on the WA6 design with a separate power supply enclosure and direct-coupling to the driver tubes. I am not going to expound upon this or other technical aspects of the amps further, in order to avoid exposing my ignorance. Instead, I would direct you to Woo Audio’s website or to other Head-Fi threads on this topic, such jamato8’s thread about modding the WA6 where ideas such as the parts upgrades and pseudo dual power supply mod originated.

The two units supplied were stock models. This is what Jack offered so I didn’t choose it that way, but I was happy about it. I would only have the units for a week, and that wouldn’t allow enough time to burn-in upgraded parts. In addition, I would not be able to stretch my budget to include the WA6SE plus upgrades plus tubes plus whatever else I was destined to buy after the meet. I really wanted to hear the stock WA6 against the improved power supply and other WA6SE advantages.

The system for this review was my MHDT Paradisea+ DAC with WE396A tube fed via optical from a Sony SCD595, and the headphones were my stock HD600’s. The interconnect cables were the Zu Oxyfuel and I used a Volex 17604 power cord on the amps.

I was able to convince Jack (a nice guy as I said before) to send along a $150 Sophia Princess 274B rectifier tube for the meet. Due to the overwhelming acclaim for this tube, I was determined to do this review with the stock tubes, or at least some decent NOS tubes, before rolling this rectifier in. I did not want to color the results for someone without the appetite for tubes costing 25% of the price of the WA6 amp. However, as you will see later, I couldn’t resist listening to the Princess for very long.

Woo Audio WA6
First of all, I must say that if I had not heard both amps, I would be happy with either one. The quality of construction is superb, and both amps sound wonderful. The packaging is excellent, and gave a great first impression. I love how these amps look and feel, especially that sexy, heavy volume knob. (Can you tell that I am a geek?)

I found the WA6 to be very balanced and soothing right out of the box. It was relaxing, but there was no "flushed" feeling to the tone like I was expecting from a tube amp. It was very clear and detailed, but still smooth and seductive.

All of the music that I played on the WA6 sounded realistic and much like I expected. This is a very transparent amp that would be pleasing with good sources and forgiving with lesser sources. It felt comfortable to me, even without burn-in. I didn’t know whether to be happy or unhappy about that. There is less “wow” factor with this amp, but more satisfaction if that makes any sense. There were no apparent weaknesses to the amp. I didn’t come away saying I wish it had more bass, or better mids, or more detail. I could have quit right here, but I didn’t.

Woo Audio WA6SE

I was initially unimpressed with the WA6SE for the difference in price. I got the feeling that the WA6SE tended more toward the "tubey" sound that I didn't sense in the WA6, especially on softer selections like David Gray's "White Ladder" CD. That could be because I listened first and for most of the first few days with the Sovtek rectifier that I did not like very well.

After a couple of nights of burn-in, I sat down to listen with the Sophia Princess 274B and a set of NOS Sylvania fat bottle 6EW7 driver tubes. My opinion of the WA6SE immediately changed for the better. I could hear a significant improvement in soundstage and dynamic range - whether it was the tubes or 20 hours of burn-in I can’t be sure. But I decided right there that I had to have this amp over the WA6, if for no other reason than it provided significantly more headroom.

The WA6SE packs a punch. It just screams power. It displayed excellent dynamics and a very deep and tight bass. If you like rock music, and particularly live rock music, this amp should make you very happy. It opened up Lou Reed's "Sweet Jane" and made it sound like I was in the auditorium, without losing the growling bass line and and without distorting the screaming guitar riffs.

I like Nine Inch Nails, and this amp with the aforementioned tubes made Downward Spiral sound better than I had ever heard it. It handles complex music with ease, and the bass and percussion were rendered with all the mind-numbing force that they deserve.

U2’s Achtung Baby gave me a good chance to hear how a tube amp really shines. The fine guitar work and creamy vocals on “One” was stunning, and I was equally impressed with the transients on “The Fly” and “Mysterious Ways”. This whole album just cries out to be played on a tube amp with the tonal quality being perfectly suited for the musicality of tubes.

At the meet, I tried a pair of K701’s with some jazz, and the WA6SE was also very impressive with this music and these phones. The background was black, the soundstage was wide and deep, and the instruments sounded very realistic. In fact, we tried a lot of different phones with this amp, and it drove all of them very well (including K340’s according to Shelly).

The amp has both high and low impedance jacks as opposed to a switch. I drove my HD600’s and a pair of Denon D2000’s at the same time, and they both sounded just fine. I couldn’t sense any degradation in the sound quality of either phone, but we were at a meet and not a quiet setting.

I compared these two amps to several others in their respective price ranges at the meet, and I thought the Woo amps held their own very well. The WA6 sounded great next to a Stello HP100, while the WA6SE compared favorably to the Headamp GS-1 and Singlepower Extreme.

Tubes

I tried all of the tubes that I had in both amps, and I liked almost everything. The stock 5AR4 rectifier and RCA 6DE7’s were a very good selection for the WA6. I tried the Sylvania fat bottle 6EW7's with a RCA 1966 NOS 5R4GYB in the WA6SE (a combo recommended by Takezo), and it was a beautiful match with clarity, detail, and a soundstage that rivaled the Sophia tube. This combination sounded great in the WA6 also, as did the 6DE7/5AR4 in the WA6SE.

The Sophia Princess was outstanding in both amps, as you might expect. The Princess is worth the cost. It is a spectacular tube compared to the other rectifiers that I have (which is admittedly not much). The Sophia Princess with the Sylvania 6EW7’s took the WA6SE to another level. I was very impressed with the soundstage and dynamics of this tube combination in that amp. The Sophia tube also sounded great with the RCA 6DE7's, and you could use either type of drive/power tube without changing the sound for the worse - just different.

My only complaint with tubes was the stock Sovtek 5U4G, which sounded very bottom-heavy. I'm sure this is a characteristic of this tube and it might improve with burn-in, but it was not initially impressive in the WA6SE. I need to look for an older NOS 5U4G before I draw a conclusion about that tube class; it could be I just don't like the Sovtek. If you buy this amp without buying the Sophia Princess, you might want to pick up a couple of different rectifiers to be able to experiment for yourself.

I was unable to try a metal base 5AR4 in the amps because I don’t have one and I don't plan to invest $400 in one to find out. I have heard that it makes a great rectifier for rock when combined with the RCA 6DE7’s. I spent my money on the Sophia 274B, so the Princess will have to suffice. I can't envision removing this tube from the amp anyway except when I am using the amp for burn-in purposes. That's what the Sovtek is for.

Conclusion

I decided that the WA6SE was the perfect amp for me at my price range (did I say $1200, well of course I meant $1500 including tubes and the Senn cable upgrade that was made necessary by the purchase of an amp – sorry for my wallet).

However, if you have more sense than me and want 80% of the performance for 40% of the price, you could go with a stock WA6 and be quite happy. I wanted to avoid the upgrade bug for a few weeks anyway, so I went for that extra 20% improvement.

I ma not going to comment on the value of a WA6 “maxed with pdps mod” vs. the WA6SE for a similar price, because I have not heard the upgraded WA6. I will speculate that they are similar in performance, and you would probably get a great amp either way. In my case, the WA6SE was in my house and already had 30-40 hours of burn-in, as opposed to a 3-4 week wait for a WA6 maxed plus the longer burn-in for the upgraded parts, so it was a pretty easy call.

[musicmind]

Thanks for writing up your impressions Orcin, just the review I was looking for. Very useful

I can definitely recommend trying a good NOS 5u4g, it is my favourite tube with the WA6 at the moment and better than the stock Sovtek.

Did you try the 274B in the WA6 as well? Did you find the amp to improve with this recitifier as much as the WA6SE did?

Thanks again

[wfranklin]

Thanks for the fine review.

[EnOYiN]

Very nice review. Thanks.

I have the stock version of the WA6 myself and although I know there are better amps out there I think that it has tremendous value.

[Orcin]

Originally Posted by musicmind

Did you try the 274B in the WA6 as well? Did you find the amp to improve with this recitifier as much as the WA6SE did?

Yes and yes, although I admit I was pretty smitten by the Princess by that time, so maybe it was just a placebo crush.

[musicmind]

Thanks Orcin, with most of the 274B users having either the PSU modded or SE version, its great to confirm that the stock WA6 also improves comparably with the 274B.

[jamato8]

There should be no reason the stock 6 would not improve. The impact of the choice of rectifier on the power supply in the 6 would be very substantial. What I would like to see is a comparison of the 6 with the pseudo dual power supply and the SE.

Fine review.

[HeadphoneAddict]

Nice Review!

[Orcin]

Originally Posted by jamato8

There should be no reason the stock 6 would not improve. The impact of the choice of rectifier on the power supply in the 6 would be very substantial. What I would like to see is a comparison of the 6 with the pseudo dual power supply and the SE.

Fine review.

Thanks, John. And thanks to you too, Larry! It was really nice of you to send the GES to us. It was pretty great to hear that against pabbi1's Blue Hawaii and Marc's hot-rodded KGSS.


Yes John, I would love to have reviewed the pdps modded WA6 against the stock WA6SE. However, I don't think Jack really wanted me to do that.

For one thing, I didn't give him much time to get two amps ready to send out (with no revenue attached to them), especially if he needed to mod one of them. Plus, the meet was a good chance for him to show his line of products, and as you know Woo Audio does not advertise the mod for the WA6.

So for good commercial reasons, I think he wanted the WA6 to be there, without the mod. If we had demo'ed a modded unit, then everyone would be asking the effect of the mod and how much is the mod, and what does it sound like without the mod, instead of just saying "wow this is a great amp".

I also understand you and Takezo when you say that the mod ought to be part of the product. I am not going to try to tell Jack how to run his business, but I think Jack has a price point and a margin that he wants to maintain. That's fair to me, but you have a valid point too. I'm not trying to pass judgement on that here, because that has been discussed a lot in your thread already.

I'm really trying to give people an opinion on the two stock amps. I think the fact that the mod exists and has been so well-received is making some people think that you shouldn't buy these amps without the mods and/or upgraded parts packages. And that's wrong too, because they are exceptional amps at their respective price points without the upgrades.

[jamato8]

I understand, to a degree but frankly the modification really "isn't" a modification to any extent. It is a simple power supply change that would add maybe 15 or 20 dollars in parts. It is a totally practical and logical step but I believe it puts the 6 on the same par as the SE so there may lie the problem.

It is great that people can get into a very sound and solid amp and truly "enjoy" the music. That is what I am doing right now even as I am typing! :^)

[HeadphoneAddict]

Originally Posted by Orcin

Thanks, John. And thanks to you too, Larry! It was really nice of you to send the GES to us. It was pretty great to hear that against pabbi1's Blue Hawaii and Marc's hot-rodded KGSS.

It's Cool! I would love it if you could post something somewhere (or link me to it) about the Woo GES Prototype that I sent you. As you might know, I got the GES back in July and then I bought it from Jack after demoing it, like you did with the WA6SE. But then a week after the July Head-fi meet in Colorado I decided to order a new GES maxed (with pro/normal bias jacks and RCA loop out) and Jack agreed to apply my payment to the new amp when I returned the old one (or shipped it to the next reviewer).

I got to compare the prototype with the maxed GES for the first 150 hours of burn-in, and even before full burn-in the maxed was more transparent and open. Now with 280 hours on the maxed it is even better. Even though it takes 250-500 hours to burn-in, I have stopped running it for long periods to force burn-in faster. It just sounds good enough already.

Unlike the GES, my Maxed WA6 took over 600 hours of burn-in before I thought it sounded great, and I did the PDPS mod at about that time (May). It took another 200-300 hours after that for it to settle down and really shine, but it was still lacking something with my Amperex Bugle Boy GZ34 or Philips metal base GZ34. So I added the Sophia Princess at that point, and it was just as huge of a leap or bigger as when I did the PDPS. Blutarsky agrees with me that the Sophia completely transformed the amp.

[takezo]

Originally Posted by jamato8

T...What I would like to see is a comparison of the 6 with the pseudo dual power supply and the SE.

i have both now and while i'm not ready to submit any form of review, i have
to admit the SE has much more juice... leading to a sense of larger soundstage
and deeper bass... no other amp i've had reaches as low as the SE... the
sub bass is quite impressive... deep but taut/springy and no muddying the mids
and highs. my SE is a stock, as i will, no doubt, do some of my own upgrades
later... much later. the stock is impressive enough but there's something
smoother and tonally more pleasing about the highly modded wa6 that the
SE doesn't share. i think it may be the blackgates...

i sent my SE in to jack for the recent mod and what i see is that the first cap
after the inductor is now a 10uF cap:

[atbglenn]

Was that little circuit board added as part of the mod, or was it there already. Looks like a time delay relay circuit for soft start possibly?

[takezo]

no the relay delay circuit was put in as part of this last mod by
wooaudio. it's similar to what they do with the wa5 power supply...

btw, the EML and the Princess sound exquisite on the SE... no flash
or oddities on start up. whereas my other rectifiers sound very fine,
the 274b has the best micro resolution of them all... the tiniest morsel
of sound is presented without the slightest hint of strain nor digitalis...

[jamato8]

Originally Posted by takezo

i have both now and while i'm not ready to submit any form of review, i have
to admit the SE has much more juice... leading to a sense of larger soundstage
and deeper bass... no other amp i've had reaches as low as the SE... the
sub bass is quite impressive... deep but taut/springy and no muddying the mids
and highs. my SE is a stock, as i will, no doubt, do some of my own upgrades
later... much later. the stock is impressive enough but there's something
smoother and tonally more pleasing about the highly modded wa6 that the
SE doesn't share. i think it may be the blackgates...

i sent my SE in to jack for the recent mod and what i see is that the first cap
after the inductor is now a 10uF cap:

Great! I look forward to more information. It is good to know that in certain ways you feel it is a step up. What types of caps are used in the SE? Any shots of the other chassis? A great cap to use in the power supply and very, very reasonable is the Panasonic TSED you can buy from Digikey. They are as good or better than they polar BG's and a fraction of the price.