Orcin
1000+ Head-Fier
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- Apr 21, 2007
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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.
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.
