The Woo WA6SE and beta22/sigma22 amps face off. (Review Posted)
Apr 8, 2011 at 12:31 AM Thread Starter Post #1 of 67


Chaser of Ghosts
Sep 20, 2008
I've had the Woo WA6SE for about 10 weeks now. I've had the b22/s22 amp for about 6 months, however, I sent it out to have it redone, upgraded and had some issues dealt with. Now it's "back and better than ever". I've had the beta in it's current configuration for about a month now. I've thoroughly enjoyed listening to both of them. I'm working on a review comparing the two together. An unlikely match up pitting a transformer coupled tube amp and a discreet solid state amp? Who's to say? There are more similarities than you might think. There are key differences too. Some you might not even expect. Will a winner be declared? Wait and see. I will post it here when I have finished writing it. Thanks for reading.


Apr 8, 2011 at 12:32 AM Post #2 of 67


Chaser of Ghosts
Sep 20, 2008

I think we all get into this hobby of music and audio for many of the same reasons. At least I think we do. I believe, in one way or another, we want to feel the music more. Become more emotionally involved. Get deeper into the soul and meaning of the songs we love by becoming transported to another place and time. I don't really think genre matters. Whatever the genre, song, album or artist there is an attachment we have to music on many levels. Am I to believe the modal jazz offerings in Miles Davis' "Kind of Blue" has any more meaning to a fan than, say, Tupac Shakur's "All Eyes on Me"'s brand of hip hop might have on someone else? Both albums may hit the listener in different ways but that still doesn't mean the impact on them is any less.

Maybe I'm wrong, but I'd like to think that the obsession so many have over their headphones and the equpiment we gather is to experience more of that brunt-force influence our favorite music gives us. When I listen to a song from a bad source or poor speakers or a muffled headphone I not only cringe but can't help but wonder if this is what the artist really wanted me to hear and experience? That's how my preoccupation began with this journey into hi-fi.

I started out wanting to find better sounding music than I was getting and ended up searching for audio equpiment that extracts every last note the music has to offer. Not just the note itself but the meanings within the note. A silly notion maybe but, hey, that's what I've tried.

So I've bought, sold and listened to tons of headphones, sources and amps. This leads me to this comparison of two amps. Two dedicated headphone amplifiers that aren't necessarily where someone begins their odyssey, but is certainly possible that someone might be able to end their pilgrimage for that ghost we all chase.

The two amps I'll be comparing for this review are, in no particular order, the Woo Audio WA6SE ($1050 for the standard version). An SET Class "A" tube amplifier. The other amp is the beta22 (prices vary widely and can range from about $1100-$1800 depending on the build). It's a DIY discreet Class "A" solid state amplifier. It might be strange to directly set a tube amp up against a solid state amp. As you'll read throughout my review you'll see there are more than a few similarities as well as differences.

Although I have listened to each amp through several different headphones, including higher and lower impedance cans, for the purposes of this writeup I'm going to use only my reference pair

Here is how my system has been set up during this test:

Laptop>WinXP>iTunes>lossless>Nordost Blue Heaven USB>Cary Xciter DAC (Jellyfish power cable)>Nordost Blue Heaven interconnects>Woo WA6SE/b22/s22(Nordost power cable)>HD800

The only variable in the equpiment is the change between the two amps. All the rest of this comparison was done with the above constants.

All of the direct A/B listening was volume matched using pink noise at 84db +/- 0.5db as that's as accurate as my Krap Shak meter is. For general and extended listening the volume was variable but my impressions are based over long periods of time and I usually listen at pretty much the 84db level anyway. Sure I have times when I want to crank it up or turn it down but I'm not going to account for every single listening variable. It's not practical. Also, having listened to both amps over extended periods of time, I have gotten to know each of their own characteristics and have to taken that into account.

The beta22 I have is a three channel amp with the separate sigma22 power supply. According to the AMB site the power is rated at 18 watts@ 8Ohms. That works out to 5.6 watts@ 32Ohms and 750mW@ 300Ohms that the HD800 is. Needless to say it's one of the more powerful dedicated headphone amplifiers available. I have the amp configured to 5x gain. Which I think offers the best balance of versatility and a low noise floor. With 5x it can drive almost any headphone. Low and high impedance. At least up to the HD800. I don't remember if I had a T1 plugged into it but I do know that, as configured, it didn't do justice to the HE6. It did do quite well with the LCD2.

The Woo WA6SE will have the Sylvania 5U4G rectifier tube and the GE 6DR7 power tubes throughout the "contest". I have rolled over a dozen combinations and found this tube setup to suit me the best in terms of balance and my preferences. Some of the other tubes were either too sibilant or were a little too bloomy in the bottom octaves. According to Woo's site the WA6SE has 2 watts @ 32Ohms and 130mW @ 300Ohms. The power output is tube dependent and the configuration I have seems to be the most powerful. I have no way of verifying it's output though. The Woo has two jack inputs. One for low impedance and the other for high. I use the "High" jack for the Sennheiser HD800 throughout.

The WA6SE does seem to have more gain than my beta22 because the volume knob is at 09:00 compared to 10:00 on the beta amp for the same volume level. Remember that gain and power aren't directly related. The volume knob may have more initial travel on the b22 but will ultimately get louder than the WA6SE.

Before I get into the actual comparisons between the two amps I want to mention that both of these amps are among the best amps I've heard. One would hardly make a poor choice with either the WA6SE or the beta22. It's easy to imagine and if you had either amp you can take comfort in knowing both amps are giving most headphones everything they've got. With many other amps I've had or listened to there have been times that you can point to flaws that stand out or you just know there is more performance to be had.

I know that the WA6SE is in the middle of the Woo lineup and from everything I've read their higher level amps are indeed better. And yes there are other tube headamps that probably are better. There are indubitably others that are much more expensive. BUT! When you are listening to the 6SE you would hardly miss the flagship models if you didn't know. It's really that good.

It's been told that the beta22/sigma22 is among the best solid state headphone amps available. Certainly it's the best solid state amp I've had the privilege to listen to. I know there are other rivals like the Luxman. Having never heard it I cannot say if the Luxman surpasses it or not. I'd speculate that the other solid state peers are either a matter of preference or the differences between them are fairly minute.

Another one of the reasons this comparison makes some sort of sense is because the Woo WA6SE is supposed to sound more solid state than other tube amps while the beta22 is supposed to be slightly warmer than is typical for solid state. So how do both the Woo WA6SE and the beta22/sigma22 compare? Do they sound the same? Are they drastically different? Let's take a look.


I started out with how they each look as this is the most subjective part. Important as the sound is, I still want something that is pleasing to the eye. The great thing is they're both gorgeous. Both of these amps have dual chassis with a separate power supply.

I helped design my b22 with the builder (fellow Head-Fi'er fishski13) and I think it is not only great looking but unique. I tried to veer away from the DIY utilitarian look. It has a sleek and post-modern minimalist expression. The Woo is hardly a slouch. It appears to be carved out of an ingot of sold metal. It has the heft to continue that effect. Both are monochromatic silver. The Woo displays it's tubes proudly for all to see where the b22 takes a more subtle approach. They both have a stunning demeanor on my rack and should fit almost any decor. This is a toss up and both score a 9.5/10 for beauty.


It might seem out of place to mention that one full sized amp that can only live in a rack is more convenient than another full sized amp. It's worth mention though. I know many relish the ritual of a tube amp. Like the procedures of listening to a turntable seems to be a right of passage, so it is with a tube amp. While most solid state amps can be simply turned on and left on, tube amps require more care.

As a precaution, I've always had the habit of plugging and unplugging headphones from an amp with the volume knob turned to zero and the music either off or on pause. I do this with all amps. Tube amps in general and with the Woo specifically I let the amp warm up and settle down before I start listening. On the Woo website it's recommended that their amps not be left on for more than 10 hours at a time and they should never be left unattended. Also, if you're not going to be listening to music during the next half an hour or so many suggest turning the amp off. Cycling the WA6SE on and off frequently isn't the best for longevity. Let's not forget that tubes don't last forever. I'll rate the Woo an 7.5/10

The b22 (as with many solid state amps) doesn't require as much attention. For the most part they can be turned on and left on. If I leave the house I turn it off. When there is a thunderstorm looming all my equpiment gets unplugged. Other than that it's press the button and it's ready. The beta gets a 9/10.


I've always felt that the predominant foundation of an amp's quality was how quiet it is. A high or low noise floor sets the stage for a good deal of an amp's personality. I know that tubes generally have a higher noise floor compared to solid state and it does have some effect. I find that the blackest backgrounds are especially important to very well recorded albums. The b22 is so extraordinarily quiet that the Woo is noticeably noisier when comparing the two together. The quieter beta22 coupled with the extra power reserve makes the HD800 sound effortless when I'm listening to music. It's like the entombed feeling of a Lexus while you're flying down the highway at excessive speeds. Quite and isolated. While driving a Honda Civic at the same speed, though, you can feel the car moving and hear all the surrounding noises.

I'm not saying that the difference between the two amps is that extreme. What I am pointing out is I can hear the distinction and it can have a repercussion on how songs will sound.

Not that the higher noise floor of the 6SE is all bad. With bop Jazz it adds to the ambiance and feeling. Sort of like being in a smoke filled 50s jazz club. Across-the-board, though, quieter is better. I'd rate the Woo an 8.5/10 and the b22 a 9.5/10.


If dynamics and dynamic range is defined by the difference or perceived difference between the quietest passages and the loudest passages within a song or music then we're on the same wavelength. If you're using a different definition then I don't know what to tell you.

I know what I'm about to say will probably will be disagreed upon by many. I know when I was talking to Skylab a while ago about it he acted like I was growing three heads. But it's what I hear out of my ears. Of course YMMV.

I think the b22 has quite a bit more dynamic range than the WA6SE. When I first listened to the Woo after I took it home it sounded compressed. Everything out of the Woo sound much closer to the same volume levels than the extremely dynamic beta22. The beta can be exceptionally delicate to quiet passages and highly robust when needed. The 6SE on the other hand is narrower in scope and can appear a little ham-fisted next to the beta amp.

As you'll read further in this review both amps have their own separate strengths and areas where one is better than the other. In my opinion this is one of the Woo amps least admirable traits. I have tried different tube combinations and it still exhibited this character. I expected, at this level, to have more. It's certainly not the least dynamic amp I've heard but I feel a bit more claustrophobic with this tube amp than I do with the solid state one.

The b22 is hugely (Yea, bad grammar, live with it) dynamic. It just seems endless. One second you hear the soft twinkles in the intro of Pink Floyd's "Shine on You Crazy Diamond" and the next you can hear the bombastic crescendos of Tchaikovsky's "1812 Overture". With the Woo the two wouldn't contrast as much but the b22 makes it seem they are world's apart. As they should.

The more closed nature of the WA6SE makes me score it's dynamics at a 7.5/10 where the beta22 comes in at a solid 9.5/10.


The audio gods giveth and they taketh. Where the Woo WA6SE wasn't as dynamic as the b22, it does seem to have greater front to back soundstaging. The HD800 inherently has vast staging. This suits my preferences very well. I enjoy the feeling of space while listening to groups like Pink Floyd or The Moody Blues. They seem to benefit from added dimension. The Woo amp certainly gives a song like "Nights in White Satin" the ethereal sensation it's trying to portray. The Rimsky-Korsakov "Russian Easter Festival Overture" is an example of how important the breadth of staging and how critical imaging is. The 6SE places you within the orchestra and if you close your eyes you can imagine where the instruments are playing with precise placement.

The b22 also does an excellent job with it's soundstage portrayal. It just doesn't have the same three-dimensionality the Woo conveys. That can work to it's advantage at times too. I always felt certain jazz should have a more intimate feel. Jazz seems more out of place in a larger venue than in a small club. What's more apt than listening to Coltrane's "I'm Old-Fashioned"? The beta22 does a better job of giving me the elemental nature of that song.

Then there are time where it's a matter of one's mood or preference. I'm listening right now to Metallica's "Enter the Sandman" through the 6SE and it's soundstage sounds great... I just switched over to the beta amp playing the same song and I'm definitely banging my head. In a good way. :D

Both amps make the song "Ride Across the River" off Dire Straits' Bothers in arms eerie good like your sitting on the edge of the river bed with the crickets chirping all around you. Between the two amps the Woo wins out over the beta. I'd give the Woo the slight edge with a 9.5/10 vs a 9/10 for the 22.


Another supposed difference between tube amps and solid state amps is their perceived speed. Tubes are imagined to be polite and mellow. Some might even say slow and smeared. While others would call a tube amp organic. On the other hand solid state amps are assumed to be fast with lightning transitions. They've been known to have an etched or crystalline sound. Still others will call it punchy or snappy. I think both amps depart enough from their inherent nature to almost eliminate the suggested negative connotations.

The Woo amp, with the tubes that I've chosen, has impressive initial attack from the leading edge of notes. It has just enough tubey goodness to remind you that you are listening to tubes but doesn't shove it down your throat. Moving from note to note has nice distinctions and has an ever so slightly extended decay over the b22 but the Woo never gets sloppy.

One of the favorite songs I use to test equipment's attack and note transfer is from the intro of "Time" off Pink Floyd's DSotM. It gives a clear listen from the clock and then the song gets sped up during the rapid firing toms.

The beta22 is a faster amp over the slightly more relaxed WA6SE, however, it never sounds too sharp or creased. The leading edges are nice and clear and the decay off the initial strike is slightly shorter than the tube amp yet doesn't manage to sound unnatural or robotic. An amp like the wonderful Gilmore Lite is, to me, sharper than this beta.

Both of these amps excel at their respective speeds with the B22 being audibly the faster of the two. Nonetheless, each of them make the music flow in a natural way. I'll give both of them a 9/10 for attack and transients.


I'm a bit of a detail freak. If there were two fleas copulating in the studio or a woman's hair swaying in the audience while the music was being recorded I want to hear it. That's partly why I really like the Senn HD800. I don't want the perception of detail that a forward lower high frequencies can make you hear. I like details across the spectrum. Pink Floyd's (I'm a shameless Floyd fan sorry) "Wish You Were Here" is one of the songs I use to test some mid frequency micro detail. In the beginning of the song the man over the radio says the word "mercifully". The "ly" is not always easy to decern and sometimes can sound like "mercify" with the "L" in the "ly" obscured. Both the b22 and the WA6SE both shine at low level detail and pass that "mercifully" test.

Each of the amps are able to reveal all the subtle nuances within the music and reveal everything within the recordings. Sometimes to a fault. Neither amp is apologetic to defects in the recording. I have some Glenn Miller recordings and in many of them you can clearly hear the pops and clicks that the (authorized) CDs were taken from.

I've listened to enough amps to rate the each amp at 9.25/10 for their detail retrieval.


As I mentioned in the section above the beta22 and the Woo amp are brutal to poorly recorded albums. Rendering some music as almost unlistenable. *cough cough* Linkin Park and Lenny Kravitz.

With well recorded music though a transparent amp allows you to get a clearer picture into the music. The two of these headphone amps are quite transparent yet do it differently. The Woo is warmer and a bit richer where the beta22 is notably clearer. This should be expected. The tube amp does have a little more of a fleshed out sound while the solid state amp has additional clarity.

Tonally they both seem right even though they're not identical. I'm a fan of Mozart's Violin Sonatas. I get a realism from the two that puts me right at the performances. The b22 and 6SE seem so natural and balanced.

9/10 for the amps


Tube amps are expected to have rolled off top ends. Right? Isn't that in part what's supposed to give them its characteristic "tubey" sound? Woo's own OTL amp the WA2 is reported by many Head-Fi'ers to exhibit that. The OTL from Decware seems to display that trait. I'm here to say, to my ears, the transformer coupled 6SE isn't nearly as tubey as you'd envision the higher frequencies to be.

The presumptions of solid state are of mechanical sounding upper octaves that screech and pierce the ears to blood curdleing levels. Maybe to some small extent for other solid state amps that might be true. I think many tube lovers over exaggerate it a bit however. Both amps here seem to move a bit towards each other's stereotype of the other is supposed to sound like. To a point.

In my listening the beta22 takes the edge off of the treble peak that a good number of people have with the HD800. Of course it doesn't make the Senn sound like the LCD2 but what it does is tame the highs from being what others might think is strident. The 22's highs are quite smooth and I can only hear some sizzle with the hottest recordings. I just love the solo from Pink Floyd's "Hey You" whith the b22. It just soars.

The Woo WA6SE's upper octaves are just a bit more polite when listening than the solid state amp. The extend up well but are a little bit more laid back in comparison. It is a tube amp right? What it doesn't do is the frequency response doesn't fall sharply off a cliff. The highs are very smooth and refined. Like the b22, only with the the hottest material does the treble show any sort of strain. I use Boston's intro to "Foreplay/Long Time" as one of my treble testers.

I think the beta22 handles the highs with more athority and will give it a 9.25/10 and the Woo a 8.5/10 because of it's slightly further back in the mix.


Music lives in the midrange. Right? At least that's the rumor. From what I hear it sounds very true. It's also in the mids where both amps show their character and separate from each other most.

The beta22 amp adds just enough warmth to remove what some might think of as being sterile or sucked out. Yet it maintains a balance with the rest of the music. It's robust without being a standout. Jazz, metal or classical it doesn't matter. Turn on Tool's "Third Eye" and you'll hear the mids as a total.

Although the Woo amp's midrange isn't syrupy sweet that might be expected from some tube amps it is still warmer than the b22. There's something about the more forward nature of the Woo that romanticizes jazz. Who doesn't doesn't want to be transported to a time when Miles Davis' crew was jamming to "Bitches Brew" in a smoke filled hidden place?

I'm going to give the edge to the Woo here. it deserves a 9.5/10 where I'm giving the b22 a 9.25/10.


Just turn on The Beatles song "Come Together" and you will quickly know if your equpiment has bass impact or not. For those that believe the HD800 doesn't, need only play that song with any of these two amps to know how well the HD800 can pull it off. Just to plug the HD800 a bit further I can hear tones that extnend down deep to at least my hearing threshold somewhere between 30hz and 20hz. Since the Senn doesn't have that dreaded mid bass hump it makes evaluating amps easier. If you're looking to have either amp transform the HD800 into the Denon D7000 then move along. There's nothing to see here. :)

The beta22 has vice grip control ove the bass it reproduces. I have found that detail and texture of bass is more difficult to achieve than with other parts of the audio spectrum. Too many times it just comes across as bloated and sounding one noted. Not so with the b22. It has a tad lighter impact than the 6SE. "One of These Days" (yes Pink Floyd again) has a dueling bass line throughout the song. One in the left channel and one in the right. Gilmour and Waters are each playing. With the beta22 amp you can more easily distinguish the two bass guitars drone from start to finish.

Although the Woo amp doesn't have the same iron fisted composure the beta amp does, and yes there is some slight bloom, there is ample fabric to the bass notes. Even with the HD800 the bass impact with the WA6SE is nice and can be felt. Puscifer's "Dozo (Version 2)" sound's sweet with the Woo.

I like bass that's very taut so I'm going to rate the bass response of the b22 at 9/10 and the Woo at 8.5/10.


Because the Woo is more mid centric the vocals are also more intimate. Although there is a bit less texture coming from the voices, if you prefer it's intimacy, I can see how someone would prefer listening over the beta22. "Rape Me" from Nirvana is a shining example of listening to Cobain singing right to you while listening to the Woo Audio amp.

The beta22 may not have the prominent vocals of the Woo amp but the singer's voices have more pitch and vibrato. The good part of the b22 is that the vocals are far from thin. They blend nicely within the mix without having to be a stand out. When I have had other solid state amps the b22 was a tad warmer. It can't compete with the WA6SE but does more than hold it's own. I think any of Patricia Barber's songs sound amazing with the clarity the 22 presents.

Diana Krall's "Gee Baby, Ain't I Good To You", Floyd's "Comfortably Numb" and Nirvana's "Frances Farmer Will Have Her Revenge On Seattle" are my sibilant references. The beta22 is rarely ever sibilant. I think some people confuse sibilance with being bright. It took some tube rolling but with the tube combination I use now I have all but eliminated it from the Woo. With other tubes, though, I have found the amp can fall victim. Especially with poorer recordings.

Listen to Floyd's "Careful With That Axe Eugene" and you'll know why I chose the title for this section. The Woo makes Waters' screech a little thicker than the blood curdleing effort the beta22 let's you experience.

It's a tough call but there is something intoxicating about the WA6SE's vocals. A 9.5/10 for the Woo while I'll give the B22 a 9/10


I tend to believe how an amp deals with bass, mids and treble doesn't really mean that much on their own. Individually having great soundstage and clarity doesn't mean the amp is great either. Everything has to work together. Does the dynamic and slightly warm nature of the beta22 bring it all together? How about the Woo's ability to not be as prototypicaly tube sounding? Of course they both do. Duh! LoL. These are both amp that are near the top of the amp world. I'm sure there are examples of amps that exceed these two. There probably aren't an abundance of them. Plus I would bet they're much more expensive and I would also wager that the gap in performance isn't that vast.

When I listen to "Echoes" or "So What" or Violin Sonatas I honestly am not thinking about which amps can beat these two pretty damn terrific amps. They each have such a natural sound to them. If you don't have "Jazz at the Pawnshop" I suggest you order it. Possibly right after reading this review. :) You'll see. Well, hear...


The tube vs solid state argument is a well worn debate. The good news is there are plenty of choices available for everyone. If you're undecided or want more of the advantages that both have to give then the Woo Audio WA6SE and the three channel beta22 with a sigma22 power supply are outstanding examples of headphone amps. Both are versatile and make your favorite music come alive.
It would be a total cop out to say I like them both equally. Some days I do like one over the other. I guess audiophiles are a fickle bunch. So it comes down to which amp I listen to the most. That doesn't take any speculation on my part. It's the beta22/sigma22 solid state amp.

It's more than just it's simplicity and ease of use. I really prefer it's sweeping clarity and the amp's ability to play all the music so effortlessly. In the few areas that the Woo pushes ahead of the beta22, the margin, to me, is pretty small. With the few areas that the beta22 beats the WA6SE it does so by a slightly wider margin. The total of the beta22 is just more than the Woo WA6SE.

Of course this is a totally subjective view. Only my opinion. Since both amps are such outstanding examples it is easy to see someone choosing the Woo over the b22. I could happily live with only having the 6SE. Luckily I don't have to. The beta22 gets most of my time. In fact I'm listening to the "Zabriskie Point" soundtrack now using it and I'm completely satisfied. Well, as satisfied as any audiophile can be with other equipment looming that promises to get me closer to that ghost.

Apr 8, 2011 at 11:23 AM Post #3 of 67


Member of the Trade: SolderWorksAudio
Nov 2, 2004
parts upgrades in the Woo?
Apr 8, 2011 at 11:43 AM Post #5 of 67


100+ Head-Fier
Mar 22, 2010
Can't wait to read this.  Beta22 is on the top of my to do list.  I think it would make a nice addition to my office.  Which cans will you be using for the comparison.  I'm particularly interested in T1's and HE-6's.
Apr 8, 2011 at 12:31 PM Post #6 of 67


Chaser of Ghosts
Sep 20, 2008
Quote:Originally Posted by c12mech 

"Can't wait to read this.  Beta22 is on the top of my to do list.  I think it would make a nice addition to my office.  Which cans will you be using for the comparison.  I'm particularly interested in T1's and HE-6's."

I'll be using the HD800 for the comparison. I was hoping to have the LCD2 on loan to also ise for the comparison but my friend and fellow Head-Fi'er sold his. Sorry.

The way I have the beta22 configured wouldn't be optimal for the HE6. I also don't believe the HE6 would drive the HE6 to it's full potential.
Apr 8, 2011 at 10:52 PM Post #11 of 67


Member of the Trade: SolderWorksAudio
Nov 2, 2004

Quote:Originally Posted by fishski13 

"parts upgrades in the Woo?"

No. The b22 you rebuild. LoL

replacing the Elna electrolytics for Panasonics that sit outside of the signal path renders your pedestrian B22 totally crippled.

Apr 8, 2011 at 10:53 PM Post #12 of 67


MOT: Bellatone Audio
Caution: Incomplete customer orders
Apr 17, 2006

I also don't believe the HE6 would drive the HE6 to it's full potential.

I don't believe it's possible to drive a headphone with another headphone.  

lol @ typo
Apr 9, 2011 at 12:48 AM Post #13 of 67


Chaser of Ghosts
Sep 20, 2008
Quote:Originally Posted by IPodPJ 

"I don't believe it's possible to drive a headphone with another headphone.  
lol @ typo"

Damn! You mean I've been doing it wrong all this time? lol

My b22 is a SE three channel, two chassis build.

I've been having writer's block tonight.
Apr 14, 2011 at 12:21 PM Post #14 of 67


Headphoneus Supremus
Dec 14, 2006
Toronto, Canada
Looking forward to the review! Fishski is a great guy and his builds are always please post pics of the final product as well if you can.


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