DNA Stratus, V4 vs Woo WA5-LE, Gen 2 vs LTA MZ3
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Intro
While trying to hone my audio knowledge in the process of finding sonic nirvana, I occasionally purchase used amps to compare to those which I already have. I listen to them, enjoy them, and decide which fits my own preferences best. My favorite stays, and the rest move to a new home. I am very fortunate to have three amps at the moment, and hope readers can learn something from my experiences. All three are fantastic amps, and nobody could be faulted for preferring any of them.
I have also chosen a tube complement for each amp that, to the best of my ability, tweaks the amp to my sonic preferences. In my personal experience, I’ve almost never loved a tube amp with “stock” tubes. Some amps need more tweaking than others, but it is worth noting that all amps improve at least a little with the right new tubes, and some improve a lot. With the exception of the MZ3, I personally wouldn’t consider buying/keeping the other two amps if I were forced to only use the stock tubes. Some folks will care less about tube upgrades, and some will care more, but I felt it important to point out for any readers newer to the hobby.
Finally, I think it’s relevant to mention my sonic preferences. I’ll try to be objective in terms of describing the sound of these amps, but it’s worth communicating what my goals have been in terms of gear selection, from chain to headphones to tubes. I love detail, speed, holographic imaging, a deep soundstage, and excellent voice separation. These being tube amps, I want to be transparent that I have never looked for “warming up” the sound, or rolling off any part of the frequency range.
Source Chain:
- PS Audio Stellar Power Plant P3
- Custom fanless NUC mini PC running Roon ROCK
- Chord M Scaler
- Chord DAVE
- Upgraded power cables and interconnects
Headphones:
- Focal Utopia
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The Contenders
DNA Stratus, V4
MSRP, Stock: $4,300*
With Upgraded Tubes: $5,330
- Philips Miniwatt GZ34 Metal Base Rectifier: $500**
- 2x Sylvania Spring Top 2A3 Power: $530 (pair)
- 6N1P Input Tube (stock): $0 (stock - will try others in the future)
.* This pricing is not provided on the public DNA website and is subject to change. Please email Donald for the most up-to-date pricing
.* *This DNA Stratus is not optimized for use with a GZ34 tube. As per Donald, it is safe, but there is a slight sacrifice in noise floor. I use this rectifier instead of a 5U4G for it’s exceptional control.
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Woo WA5-LE, Gen 2
MSRP, Stock: $3,700
With Upgraded Tubes: $6,430
- 2x Sylvania 6SN7W: $130 (pair)
- 2x Philips Miniwatt GZ34 Metal Base Rectifier: $1,000 (pair)
- 2x Takatsuki 300B: $1,600 (pair)
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Linear Tube Audio (LTA) MZ3
MSRP, Stock: $3,700
With Upgraded Tubes: $4,040
- 2x Sylvania 6SN7W: $130 (pair)
- 2x La Radiotechnique 12AU7: $210 (pair)
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Build & Form Factor
All three amps are incredibly well built, and I have no meaningful complaints about any of them. The footprints aren’t worlds off (if separate boxes are placed together), but you do scale down a bit as you go from the WA5 to the Stratus to the MZ3. The WA5, when put together and almost touching, is roughly 19”W x 16”D. The Stratus is only one box, but it’s relatively wide and deep at 17”W x 13”D. The LTA MZ3 comes off as much smaller, but if you put the linear power supply next to it, you end up with effectively a 16”W x 12”D footprint, though you could conceivably move the power supply to another shelf (if available), and the main unit itself only takes up 10”W x 9”D of space.
The WA5 is the most tankish, and weighs in at a rack-bending 70 lbs. I doubt many will want to place it on their computer desktop, but for those with a dedicated audio rack, there’s something I find utterly awesome about the way the WA5 looks and feels. It would look just as at-home on the console of a steampunk battle tank as it does on an audio rack, and I love it. This is also the only amp of the three to accept balanced inputs, if that is important in your system; I am all single-ended, so it isn’t a factor for me. My one tiny complaint might be that the input and power-level selector knobs to the left and right of the volume knob are a bit mechanically vague, as they don’t lock in place with as satisfying a click as I’d like. However, the volume knob and power knob are weighty and feel fantastic. Turning this amp on also feels like I’m starting up that steampunk battle tank.
The Stratus’ box is thick, sturdy, and very very blue. If you don’t like the color, tough; it’s the color you get if you wish to own the work of the amp master, Donald. On the one hand, I would have probably chosen a different color if I could have, but on the other, I rather respect that stance. Frankly, I rather like the idea that ownership of Donald’s statement blue amp enters you into a sort-of blue brotherhood. The chassis won’t flex in the slightest as you handle it, the switches all have satisfying and solid mechanical clicks, and the volume knob is precise, with a well-weighted and smooth resistance.
The MZ3 is the most unique, and I really really like what they’ve done with it. The design language fits well with its sound signature. It doesn’t put the tubes in your face, but rather has them just poking out of that beautiful, black cube, reminding you ever so discreetly that they’re there. Turning it on brings the highly pixelated LED display to life (LOVE this look), scrolling a notice that it’s “warming up”. The volume attenuation on this amp is truly unique. I can see some folks not loving it, but I do. It’s a stepped attenuation mechanism that always starts at zero remembers your last volume level for each input when you boot it up. There is no physical start and stop to the wheel, and there’s also a very satisfying (or annoying, depending on your preferences) click for every step. The chassis itself is the thinnest of the three amps, but a far cry from flimsy. It’s solid, yet light. Access to the tubes for rolling can be had by simply undoing 6 allen bolts in the top. The amp accepts a pair of 12AT7/12AU7 tubes (but NOT 12AX7) and a pair of 6SN7 or 12SN7 tubes, switching between those with a simple dip switch on the circuit board. It’s worth noting that the MZ3 can also be used as a preamp or even an amplifier for efficient speakers, but I didn’t test those functionalities; we’re about headphones, here. 
All in all, there’s a lot to love about each amp in terms of form factor, and this is truly just a matter of personal preference and space. If I had to choose on form factor alone, I’d probably go with either the monster coolness of the WA5 or the slickness of the MZ3, but, as it turns out, sound matters. Let’s get to that…
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Blackness of Background
It’s no secret that the Utopias are very sensitive headphones (104dB SPL / 1mW @ 1kHz), and don’t have a particularly high impedance (80 Ohms). As a result, they can be finicky to pair with tube amps, which often play well/best with higher impedance headphones. The slightest background noise will come through, and even if not consciously audible, will cause fatigue over longer listening sessions. Of all five tube amps I’ve owned, these three have the blackest background. Still, I have tried to assess varying degrees of virtually nothing.
On the MZ3, I cannot perceive any noise no matter what I do. Turning the amp all the way up (with no music) gives me nothing. Most telling, however, is listening. There is simply nothing in the background, and I could listen to this amp for hours with no fatigue (though, other contributing factors to that will be discussed later). Now, I’ve experienced with other amps the cause of the ultra black background seeming to be a result of it losing super low level micro detail, and that may be in play here, but to be frank, I cannot be sure. This amp can probably be paired with virtually any headphone and not produce even the slightest hint of noise.
The Stratus is also dead silent, and I can turn the volume knob to the max (no music) and not hear anything, so long as it is fitted with the (intended) 5U4G type rectifier tube. If I switch out the 5U4G rectifier for a GZ34, which the amp can accept but is not optimized for in terms of noise, I can get a barely perceptible hum at max volume. However, that really shouldn’t count against it. I use a GZ34 because it’s more tight and controlled than the 5U4G tube I have, but my doing so shouldn’t cause me to ding the amp on noise if I’m specifically putting in a tube that is known to not mesh properly with the amp’s carefully considered noise-reducing circuitry. Those who wish to buy this amp can opt for a rectifier switch (at extra cost) that allows the amp to run optimally with a GZ34 (or 422A or GZ37) tube.
The WA5 is dead silent at anywhere near listening levels, but technically comes in behind the other two because I can get a bit of hum as I near max volume (no music). I used to be able to just barely hear the amp even at listening levels, but that is before I became familiar with how to properly use the nulling pots, and between better tubes and honing the pots, I’m at absolutely no noise anywhere below 90% on the volume knob, and my listening happens in the 5%-25% range.
In summary, all three are great on noise. The Stratus and MZ3 just edge out the WA5, but only just.
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Staging, Imaging, and Separation
Staging is where these amps start to meaningfully separate, but critically, not into “better” and “worse” - just different. I fell in love with tubes in the first place because they added depth and dimensionality to recordings that I have never heard in a solid state amp. However, in return for that staging, many tube amps sacrifice too much of the detail, speed, and black background I want to retain. These three have been excellent performers on staging with few, if any, of the sacrifices.
The MZ3 ends up as a middle ground between the other two amps in terms of soundstage shape and depth. The moderate width and depth are coupled with incredible instrument separation. However, I again suspect that the extremely clear separation may be partially due to some loss of microdetail that would otherwise fill in the “room” of the recording. I don’t hear echoes off of walls and spaces like I can with the other two amps (or out of the DAVE, by itself, which is my reference).
The WA5 stage is wider, but shallower, and set back just a bit from the listener. If you want to feel more like you’re sitting back a bit from the stage and hear the performance from in front of you, this is a great choice. Separation is very good, but again, not incredibly deep. Still, notes and sounds have exceptional dimensionality and tangibility.
The Stratus takes your head and pulls it right into the music. It has the deepest, and most surrounding stage, by far. Others have described it as a “you are there” listening experience, and they’re absolutely right. Just like the WA5, notes have this incredible texture and dimensionality, and I feel like I can hear the note and the space around it (holographic imaging).
Between the three, my preference is for the Stratus, hands down. I enjoy the others very much, and this is purely a case of personal preference, but I find the feeling of being thrown into the middle of the music so incredibly intoxicating. Other folks would be entirely reasonable in leaning toward the other staging profiles, and it’s definitely fun to switch between them.
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Detail, Timbre, Speed, Control, and Frequency Range
Here, it’s important to note that both the WA5 and Stratus are single ended triode (SET) amps, and both perform more similarly than differently in this category. Detail and clarity are exceptional. Both amps preserve microdetail well, and the increased perception of space and depth the tubes bring allow you separate out and “peer into” more of that detail. I perceive no veiling (loss of clarity) worth noting. The timbre of sounds is more lifelike on these amps than any other I have heard - solid state or otherwise. I can feel a violin bow pull its string, a piano’s hammer striking its strings, a pick on a guitar string, drum hits, and a singer’s breath. Transients (the initial impulses of sounds), in particular, are incredibly crisp and realistic. In terms of stopping speed and control (preventing overshoot or ringing when a note stops), I’ve found SET amps to often struggle, and this is where tube upgrades make a huge difference. Both the WA5 and Stratus are frankly pretty poor performers here with their stock tubes, and come off as quite bloaty. However, good rectifiers go a very long way in cleaning that up. With my upgraded tubes, both are much more controlled, with the WA5 edging out the Stratus (though, I have more tube rolling to do on the Stratus to say for sure). For frequency range on the SET amps, the WA5 sounds a tiny bit thicker with a pinch more authority in the bass, while the Stratus is a smidge more even up and down the frequency range with a bit more air. However, I want to stress that the Status is far from thin or bass light, and the WA5 has plenty of air, too; the presentations just slightly lean in those directions.
The MZ3 is where things get really interesting. It has a truly unique topology, utilizing a push-pull circuit combined with their unique ZOTL (Zero hysteresis Output Transformer-Less) architecture. I won’t pretend to understand the ins and outs of the engineering, but I know it’s very different from other amps, and it sure sounds different. To start, you’ll immediately notice how crystal clear the MZ3 is, and it treats the whole frequency range utterly even-handedly, with gobs of space and air. It’s also incredibly well controlled, and can be considered as close to solid-state in that regard as I’ve heard. However, things get really interesting when we get to detail and transients. The best way I can describe it is via an analogy to photo editing. Imagine an image with incredibly crisp and sharp lines. Now imagine you took out the feathering tool and just barely touched up those sharp lines. That’s what the MZ3 sounds like. It is not blurry, it’s not smooth, and it’s certainly not veiled - but it’s not ultra sharp or crisp either. The “edges” of sounds which would otherwise be weighty or almost tangible are just … feathered a bit. This phenomenon is incredibly subtle, and it took lots of A/B listening before I could put my finger on it; one would be unlikely to even notice without an A/B scenario. When I finally was able to describe it to myself, my initial reaction was that this is a flaw. With more listening, I have realized that it’s actually a double-edged sword, and is desirable in some circumstances. To be sure, this amp will never be as convincing or lifelike as its SET brethren. However, oh my lord, this amp is easy to listen to - for hours. That slight “feathering” of the sound just eliminates any unpleasantness from every. single. recording. If you’re not hyper-focused and listening actively, the ultra black background, clear separation, and crystal clarity, combined with that almost intentional-seeming feathering, is so utterly relaxing. Not meaning this as a backhanded compliment at all, the MZ3 might be the best background listening amp ever made.
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Conclusion
Each of these amps ended up being quite distinctive, with more differences than strengths or weaknesses. Had I a magic audio wand, I would take at least some attributes from each amp and mash them together. Alas, this is not possible. At the end of the day, the amp that most often finds itself atop my rack is the DNA Stratus, and it’s the amp I would personally choose between the three. Again, I wouldn’t at all fault someone else for choosing either the WA5 or MZ3. As a matter of fact, even though I’d personally rank the amps as Stratus (1), WA5 (2), and MZ3 (3), if I could keep two, I’d make the MZ3 one of them. Either the Stratus or WA5 would satisfy me for that SET sound I’d want for more active evening listening sessions, and I would switch to the MZ3 all day while I work.
Rounding out the Stratus story, the unit I have on hand is a demo amp which I do not own, and it will have to move along soon. However, I liked it enough to place an order for its bigger brother, the Stellaris. I love that SET detail and realism combined with the deep, middle-of-the-music soundstage that I can hear wrapping around me. Given that the Stratus just edges out the WA5 for me, I knew that the Stellaris would be like the Stratus, but a bit more - and I cannot wait!
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That said, to be clear, I actually didn’t go full-blown Stellaris Special. I got the rectifier switch and stepped attenuator as add-ons to the “stock” Stellaris.