DNA Stratus 2A3 amplifier - first impressions

I pre-ordered it in December, 2011, and expected delivery in February. I waited all afternoon by the front window yesterday watching for Fedex. It arrived at 7:10pm. 

The box weighed ~35 pounds - quite a bit heavier than its little brother, the Sonett. My Sonett is sort of maxxed-out now -- its SQ comes real close to that of the $10,000 Apex Pinnacle, which I had the privilege of borrowing for 10 days last December. My Sonett has all of its clarity and detail, but not the same body, juice, presence. The part that brings goose bumps and tears, EMOTION.
 
And that's why I've been so excited about the Stratus. Donald has posted several times how "juicy" he has been able to voice it, and the comments from last fall's LA meet were all about the same factor.

It was well-packaged, just like the Sonett was. Professional job. And they even look like siblings! I was very glad that Donald installed a TKD potentiometer already, because that was one of the major upgrades he walked me through on the Sonett. But there I saw the same old Switchcraft XLR connectors - I remember how difficult it was to remove my Furutech XLRs from them, and also what an improvement in clarity and volume it made when I replaced them with cryo'd Vampires. OK, I thought to myself, I have more in my parts box, and I have several other goodies that can improve the stock model, including a pair of 1940s NOS RCA blackplate 2A3s and a NOS 5AU4 rectifier, too. 
 
Those thoughts soon disappeared.
 
I set it in place on the top shelf (where the Sonett had been), and hooked up the RCA i/c's from my Bricasti M1 DAC (outstanding unit) and a p/c from my new Blue Circle power conditioner (one of the best buys ever - I began with their $200 6X Sillycone, which made a whopping improvement in clarity and bass and everthing! just by plugging it into an open power socket - amazing!). 

I almost messed up on the 2A3 pins. Two of the four are slightly larger, and I thought I had inserted them correctly - BUT when I stopped to read Donald's setup instructions, I held my breath when he said "and the large socket holes are on the LEFT" - oops. Buyer beware.
 
Alright - ready to go. The very slight glow, almost not visible, from the tops pf the 2A3s confirms immediately that Donald has implemented his conservative philosophy again - at that minimal power consumption, the tubes will last (almost) forever, and they are running in the most linear portion of their current-voltage range - well, gee whiz, here in the User's guide I see it says Power output: 1.8w into 50 Ohms. Wow. Most 2A3 amps get 3-8 w out per channel. Remember, conservative means very linear, and very likely noise-free.
 
So I plugged in my LA7000 balanced headphone and hit play for a favorite CD - Schubert's 7th and 8th Symphonies  by George Szell on Sony. For the first 10min the SQ had a sort of orange coloration, but after it warmed up I heard a stunning level of SQ. First of all, it was dead quiet - no hum whatsoever, no hiss anywhere. And the sound? Natural timbre, palpable body and deep presence, dynamic contrasts as strong as I've ever heard with that CD, and the sound was BIG. Full-bodied from top to bottom. Every voice was a large presence - the oboes, the trumpets, the plucked strings, the timpani - all had a natural presence and a BIG presence, and I just sat back and enjoyed the music!
 
Next CD was Brahms first sextet, DG Amadeus Quartet. Again, natural timbre, BIG soundstage, every instrument's voice was easy to distinguish and placed within the BIG space in my head. Compared to the former setups here (Meridian 808.2i or Berkeley DAC into the modded Sonett or a Rudistor RP010B), this was a MAJOR accomplishment with this CD. OK, I thought, HERE IS THE PRESENCE I'VE BEEN WANTING AND WAITING FOR. 
 
Next CD, a real gem, Le Chansonnier Cordiforme, Anthony Rooney and The Consorte of Musicke (no, it's not electronica, it's the top 30 from the fifteenth century). The SQ was clear, natural, and BIG again, with the gut pangs that only come from real presence. Amazing. And I hadn't even rolled out the rectifier yet.

OK, H-Fers, those are my first impressons. It is definitely more than twice the value of the Sonett. I have probably invested at least threefold the original cost in my Sonett, and it still doesn't have the presence that emerges from the Stratus stock. I'm quite certain I can wring out some improvements in clarity and micro-detail with a few small tweaks, but Donald has done one whale of a job voicing this amp straightaway. Bravo, I say - Well Done Mr DNA!

Yes!  Excellent.  I have been waiting for this thread to pop up.  Thank you.

Great work!! let's burn-in for about 100hrs and see any further improvements on it.

^^^ That's exactly my thought, too. When the tubes and caps and all have 1-200 hrs, a lot more will come out. It already has so much, even in the detail - I went looking this morning with a disk that has some very fine micro-details, and yes, they're there! just not quite as clear as on my souped-up Sonnet. But as it ages smoothly it will all come out....
 
It's running 24/7 now.

Congrats on your new amp, I ordered one as well... mine is coming next month though. Looking forward to more impressions and maybe a comprehensive review after burn in.
 

At last!

That is a great review budx3385.  Donald's site implies that the Stratus can handle a range of headphones including the HD800, T1, Audeze, HifiMan, etc.  But can it handle IEMs without background noise and also without being hampered by the volume increasing too quickly when adjusting the volume control?  I have been quietly waiting for an amplifier which can handle the total spectrum of headphones and the Stratus looks like it has a lot of potential.  Looking forward to your future comments 

Quote:

budx3385 said:

 
OK, I thought to myself, I have more in my parts box, and I have several other goodies that can improve the stock model, including a pair of 1940s NOS RCA blackplate 2A3s and a NOS 5AU4 rectifier, too. 
 
Those thoughts soon disappeared.
 

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Good news!  I also await further developments.  You might also want to look at EML 2A3s, either the carbon or meshplates, depending on your preferences.  The meshplates sound sort of, well, "light" and refined, while the carbon plates have a bit more body, but it's not excessive, and better detail.  The cream of the crop are the AVVT meshplates, but they are virtually unobtainable.
 
Donald selects his parts, wisely, based on the incremental tradeoffs between balance between sonics, reliability and price.  You might be tempted to start switching parts.  However, I would urge caution as a big price leap might not improve the sonics very much.  Donald has a lot of experience.
 
Now, having said that, I am always tempted to change coupling caps.  But have you any idea how much a pair of the new V-Cap, or Audio Note, copper foils cost...a dn how long it takes before they settle in?  

Reference: my last post, where it read "incremental tradeoffs between balance between sonics, reliability and price" makes no sense.  
 
Change this to: "incremental tradeoffs between sonics, reliability and price". 

madbull, congratulations on choosing wisely! I hope after your unit arrives that you will share your impressions and maybe add enough to call it a review, and you are very welcome to add your comments in this thread and make this a community effort, like the Sonnet thread is!
 
TIMITS, thank you, I appreciate your appreciation. As for IEMs, I never got around to testing the Pinnacle with my WS5, and it has a labeled output option called "IEM". But the Stratus is not going back in the shipping box in 10 days, so I could certainly try that later. I enjoy the comfort of headphones more than iems. For the LA7000s, I have to set the volume control at 3, so it might need a larger pot for iems. But Donald installs an Alps pot as stock, and I chose the TDK upgrade option, so stock could be different.
 
Frihed, I am pretty impressed with how complete the Stratus is, just plain stock. You are very right - Donald spends a lot of time and effort deciding on each part based on how it sounds with the whole. That's a large part of why I was certain I wanted one as soon as he announced the Stratus. Donald has great ears - and when he said he was aiming for powerful and wet and "juicy", it had to be good. An audiophile friend here bought the EC Balancing Act last fall, which similarly can be a 2A3 amp, and it sounds awfully nice, but it runs hot, and it's two boxes, and I knew whatever Donald makes has to be darned good. I just had to wait. Well, the wait was worth it!
 
As for the EMLs, when I bought my Sonnet, I was happy with the basic sound, but it was obvious that better tubes would help, and I ordered new cryos immediately. I'm not so sure here - the SQ is really very good, well, excellent I have to say. Just burning it in for a couple hundred hours will make a significant difference in detail and clarity, for sure. The EML's are $500. And there are no other alternatives for the driver tube, AFAIK, so a swap to a different octal might require changing a bias resistor too. On the Sonnet, the biggest change with a tube swap actually came with the rectifier swap, so that's the first one I will try here. 
 
Any other suggestions would of course be very much appreciated. Glad you joined this discussion!!

 
oh, BTW, a friendly suggestion - after you "submit" a posting, you will see a pencil icon in the lower left corner - that is an edit button, which gives you the opportunity to revise and correct, like I am doing now. Cheers!

Congrats.  Is that EagleJo who has the BA?  I was on the Stratus pre-order list from October until February but couldn't keep waiting and ended up with a BA (which is tremendous.)  I second the EML mesh 2A3 suggestion.  I had a pair that I was going to send to Donald as he wanted to hear them but one had a leak.  

Gratz.

Bud's write up mirrors my impressions so I won't re-hash every detail that he has already described. Here is my bit:
 
I'm a currently babysitting Donald's personal Stratus. Over the last 5 days I have been enjoying the amp with my Audeze LCD-2's and my Sennheiser HD-800's. Bottom line-the amp sounds fantastic with both headphones. The amp is fast, powerful, warm, rich, and big sounding. I've never heard my Audeze's convey such a big sense of space. I almost thought I was listening to my HD800's for a bit. Not only did the amp handle both headphones well, it seems to deal with all styles of music equally well. Operationally the amp is dead quiet, and has adjustable hum pots, just in case you have a little hum. My only issue with the operation of the unit is that the volume pot did not to seem to have a lot of range with my phones. I find that I typically have the volume knob between the 2-4 position. This might seem like a big deal, but I never found it to be a big problem in my system.
 
To address Timits concerns about IEM's, I did a little experiment today. Now I typically only use my IEM's for in bed listening, so don't have much experience using a real amp. Out came my trusty Westone ES5's and my old Ultimate Ear 10's. I used the 1/4" single ended output jack which has a low impedance output and a 120 ohm output. Using the 1/4" out I typically had the volume conrtol in the 1 position using the low impedance setting, and got up to 2 or so using the 120 ohm output. The amp was surprisingly quiet with both phones. There was however an issue with microphonics from the tubes. I have never heard microphonic issues with my full size phones so this was a big surprise. There was a small sense of ringing without music playing and if you tapped on the chassis or tubes, there was a fair amount of ringing. In my experience 2A3 tubes often have this issue, so it wasn't a big surprise. I just had never heard it with my full size phones, so it caught me off guard. As for sound-it was good with both phones, but not great. Now as I said, I don't have much experience using IEM's and real amps, so take this with a grain of salt. Control and dynamics were great, but I felt that they was a small push in the 1-3k hertz range. It wasn't bad, but definitely not as balanced as with full size headphones.
 
That's it for now, more impressions to come.

Quote:

santacore said:

Bud's write up mirrors my impressions so I won't re-hash every detail that he has already described. Here is my bit:
 
I'm a currently babysitting Donald's personal Stratus. Over the last 5 days I have been enjoying the amp with my Audeze LCD-2's and my Sennheiser HD-800's. Bottom line-the amp sounds fantastic with both headphones. The amp is fast, powerful, warm, rich, and big sounding. I've never heard my Audeze's convey such a big sense of space. I almost thought I was listening to my HD800's for a bit. Not only did the amp handle both headphones well, it seems to deal with all styles of music equally well. Operationally the amp is dead quiet, and has adjustable hum pots, just in case you have a little hum. My only issue with the operation of the unit is that the volume pot did not to seem to have a lot of range with my phones. I find that I typically have the volume knob between the 2-4 position. This might seem like a big deal, but I never found it to be a big problem in my system.
 
To address Timits concerns about IEM's, I did a little experiment today. Now I typically only use my IEM's for in bed listening, so don't have much experience using a real amp. Out came my trusty Westone ES5's and my old Ultimate Ear 10's. I used the single output jack which has a low impedance output and a 120 ohm output. The volume control has to be in the 1 position for the low impedance, and got up to 2 or so using the 120 ohm output. The amp was surprisingly quiet with both phones. There was however an issue with microphonics from the tubes. I have never heard microphonic issues with my full size phones so this was a big surprise. There was a small sense of ringing without music playing and if you tapped on the chassis or tubes, there was definitely a substantial ringing. In my experience 2A3 tubes often have this issue, so it wasn't a big surprise. I just had never heard it with my full size phones, so it caught me off guard. As for sound-it was good with both phones, but not great. Now as I said, I don't have much experience using IEM's and real amps, so take this with a grain of salt. Control and dynamics were great, but I felt that they was a small push in the 1-3k hertz range. It wasn't bad, but definitely not as balanced as with full size headphones.
 
That's it for now, more impressions to come.

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I didn't quite get what you said, aint there a switch to select low/120 Ohms Z?
 
I'd like to use Stratus with a lot of headphones, from the low Z Denons to higher Zs like HD800 and Beyer T1. No IEMs though.

Quote:

madbull said:

 
I didn't quite get what you said, aint there a switch to select low/120 Ohms Z?

 
I'd like to use Stratus with a lot of headphones, from the low Z Denons to higher Zs like HD800 and Beyer T1. No IEMs though.

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The 2 switches on the Stratus adjust the 1/4" output: One switch allows you to choose between full gain (0dB attenuation) and -6dB attenuation for more volume control range on high sensitivity headphones. The other switch allows you to choose between low (8 ohm) and IEC (120 ohm) output impedance.