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DNA Stratus 2A3 amplifier - first impressions - Page 32

post #466 of 1995

I designed and optimized the Stratus to be a headphone-only amplifier. Adding preamp output would have required different output transformer windings and changes to the 2A3 filament supply, which I felt would have compromised sound quality and performance while driving headphones.

post #467 of 1995

fair enough.   beerchug.gif

post #468 of 1995

I've been enjoying my Stratus (with HD800) for about two weeks since receiving it. I am using the EML 2A3 mesh plate tubes, with all other tubes being stock ones. I'm thinking about upgrading these stock tubes, and would like to check with your guys the following questions:

 

1) Is it safe to replace the 5U4G tube with a 274B? Any impressions on 274B? I notice that Shuguang is offering their own 274B which copies the design of the very famous West Electric 274B. Do you think it is safe to try one of these Shuguang 274B on the Stratus? A product page of them  can be found via the link below: 

http://www.ebay.com/itm/Matched-Pair-Shuguang-WE274-Rectifier-Vacuum-Tube-1-1-WE274B-Brand-New-/221176983450?pt=Vintage_Electronics_R2&hash=item337f2cef9a

 

2) Are the metal based 5T4 tubes compatible with the Stratus? Any impression on them for using on the Stratus?

 

3) What would be your upgrade recommendations for the stock 6N1P tube? Some of you have had good result with the RCA 6BQ7A. Are there any other alternatives? What about tubes like 12AT7, 12AX7, 12AU7, or 12BH7? Are they safe to be used on/compatible with the Stratus?

 

Thank you!


Edited by econparanoia - 2/28/13 at 10:25pm
post #469 of 1995

Donald will have to chime in here, lest I set fire to your desktop - but I have been using various 274Bs (Sylvania, EML, Sophia) to great effect in the Stratus.  They offer a slightly more refined, silky, humid sound versus the 5U4G, which is punchier and bigger and more bass-prominent.  It's nice to change them out based on your 2A3 and/or source choices.  My double flat-plate Ken Rad 2A3s have a big bold sound and I find that they pair better with a 274B.  The RCA and Raytheon 2A3s need a little kick in the pants, which the 5U4G can provide.  I have both RCA NOS and the EML 5U4Gs plus other variants I am going to try out.  Hope that helps. Don't know about the other tubes.

post #470 of 1995
Quote:
Originally Posted by econparanoia View Post

I've been enjoying my Stratus (with HD800) for about two weeks since receiving it. I am using the EML 2A3 mesh plate tubes, with all other tubes being stock ones. I'm thinking about upgrading these stock tubes, and would like to check with your guys the following questions:

 

1) Is it safe to replace the 5U4G tube with a 274B? Any impressions on 274B? I notice that Shuguang is offering their own 274B which copies the design of the very famous West Electric 274B. Do you think it is safe to try one of these Shuguang 274B on the Stratus? A product page of them  can be found via the link below: 

http://www.ebay.com/itm/Matched-Pair-Shuguang-WE274-Rectifier-Vacuum-Tube-1-1-WE274B-Brand-New-/221176983450?pt=Vintage_Electronics_R2&hash=item337f2cef9a

 

2) Are the metal based 5T4 tubes compatible with the Stratus? Any impression on them for using on the Stratus?

 

3) What would be your upgrade recommendations for the stock 6N1P tube? Some of you have had good result with the RCA 6BQ7A. Are there any other alternatives? What about tubes like 12AT7, 12AX7, 12AU7, or 12BH7? Are they safe to be used on/compatible with the Stratus?

 

Thank you!

I'm having great results with NOS RCA 6BQ7A and 5U4G. 

post #471 of 1995

Fejnomit and third_eye, thank you both for sharing your impressions!

 

Third_eye, would you please recommend a trust worthy store where I can buy some NOS RCA 6BQ7A?

 

Fejnomit, now I am even more interested at 274Bs. I came across a thread discussing replacing 5U4G with 274, and found one of posts interest, quoted as follows:

 

Quote:
Be careful using the 274A as a direct, drop in substitute for a 5U4G. It will work just fine IF the design of your power supply will support it. Assuming you have a standard CLC filtered power supply circuit, the first cap after the 274 can be no larger than 4uF according to the published data by Western Electric.
 
If you install it with a first filter cap larger than the 4uF, it will work.....for a while, then it will self destruct likely taking out the power supply transformer and at minimum the first filter cap and likely the choke follower when (not if) it shorts out.

 

I'm not sure if what the post claimed was accurate, or if 274B is identical to 274A. Just want to know your opinion on the quoted post. Also, do you know if the first cap after the rectifier tube in the Stratus is no larger than 4uF?  

post #472 of 1995

The first cap after the rectifier is 33uF. However between the rectifier and 33uF input cap is a resistor which limits peak current during charging cycles.
 

post #473 of 1995

@econparanoia, I bought 2 NOS RCA 6BQ7A tubes for $7.98 from a seller on Ebay (including shipping). Lots of these around, I did buy a cryo'd Kuhltube version of the 6BQ7A for about $35 that died after about 2 months but replaced with the non-cryod version and am happy with these. How are you liking the Stratus/HD800/EML's? I'm using the Sophia Princess 2A3's.....would love the hear the EML's sometime.

post #474 of 1995

Someone posted this comparison on the new HD800 thread. The thing that stuck me was that one post there called the bass on the Stratus "muddy." This was in relation to other amps, including amps from EC. Can one of you owners comment on this? Even better, if you heard amps referred to in this thread, please post your own comparisons? I'd appreciate this very much.

 

Also, I am not trying to start anything. There is a reference in the above link that (I think) refers to Stratus thread posters as "fan boys." That is not my position. In fact, because I respect you views I would like to hear what you all have to say, lest I am influanced by possibly biased view of that poster up there. Thanks!

post #475 of 1995

Donald himself posted in that thread:

 

"Changing from the stock Shuguang 2A3B tubes to the Emission Labs 2A3 mesh plates, I found the bass improved in extension, weight, definition, and punch. I haven't tried their solid plate version yet to compare."

 

(I'm not sure what tubes the changstar posters heard it with, if stock then of course it would make sense to revisit those impressions if Donald brought better tubes to the meet.  Meet-goers can only give thoughts on the setup they hear at the meet unfortunately.)

 

I think the members on that thread are all fans of Donald's work as well, maybe some hyperbole they've come across doesn't sit well. Of course, its a different site where people express themselves differently so you'd really have to be around on a regular basis to get a feel of how they talk and how minute a "problem" that is brought up may be.

post #476 of 1995
Quote:
Originally Posted by Radio_head View Post

Donald himself posted in that thread:

 

"Changing from the stock Shuguang 2A3B tubes to the Emission Labs 2A3 mesh plates, I found the bass improved in extension, weight, definition, and punch. I haven't tried their solid plate version yet to compare."

 

(I'm not sure what tubes the changstar posters heard it with, if stock then of course it would make sense to revisit those impressions if Donald brought better tubes to the meet.  Meet-goers can only give thoughts on the setup they hear at the meet unfortunately.)

 

I think the members on that thread are all fans of Donald's work as well, maybe some hyperbole they've come across doesn't sit well. Of course, its a different site where people express themselves differently so you'd really have to be around on a regular basis to get a feel of how they talk and how minute a "problem" that is brought up may be.

Thanks on all counts!

post #477 of 1995

That's good feedback. Of course, in a dedicated thread many owners of a particular amp will generally come across as "fanboys". No different to the LF, ZDSE, or other popular amps. There is really no substitue for auditioning this level of equipment, just way too many variables in play. A few Stratus owners either own or have auditioned other TOTL amps, as I did with the EC S7 and BA. And to a lesser extent with the ZDSE (in meet conditions). Having said that, I think that prospective Stratus owners need to factor in the cost of upgrading the stock 2A3's which I wouldn't call "muddy" but can see how others might. 

post #478 of 1995
Quote:
Originally Posted by third_eye View Post

That's good feedback. Of course, in a dedicated thread many owners of a particular amp will generally come across as "fanboys". No different to the LF, ZDSE, or other popular amps. There is really no substitue for auditioning this level of equipment, just way too many variables in play. A few Stratus owners either own or have auditioned other TOTL amps, as I did with the EC S7 and BA. And to a lesser extent with the ZDSE (in meet conditions). Having said that, I think that prospective Stratus owners need to factor in the cost of upgrading the stock 2A3's which I wouldn't call "muddy" but can see how others might. 

Thanks! How long would these tubes last in the Stratus?

post #479 of 1995

With the EML 2A3s plugged in, the bass of Stratus is punchy, tight, and not muddy at all. I had the EML 2A3s pre-installed by Donald, so I don't own a pair of stock Shuguang 2A3s. I did audition Donald's demo Stratus with the Shuguang 2A3's (at a quiet hotel room, not in meet conditions). Even with the stock Shuguang 2A3s, the Stratus was anything but muddy. My only complain was that the pianos didn't sound as bright as what they should do in real life. The EML 2A3s solve this problem for me.

 

Both the 5U4G rectifier and the 2A3s have been staying at moderate temperature while my Stratus are running. The 6N1P tube can get very hot though.


Edited by econparanoia - 3/3/13 at 10:09am
post #480 of 1995

Has anyone compared WA5 to the Stratus? I have read that Woo amps tend to be kind of bloated (talk about muddy bass), but I have not heard them so I am  asking rather than telling. When I get a next tube amp, if possible, I would like it to drive my HE6 as well as my HD800. It is not a requirement but would be nice, so I also checked out WA5 -- mostly for comparisons sake. While having experience with the Sonett makes me lean toward the Stratus, I would like to read people's impressions. Anyone heard both?

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