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DNA Stratus 2A3 amplifier - first impressions - Page 36

post #526 of 1678
Quote:

I just ordered some 6BQ7As, 6N1P-EVs, and RCA 5U4G ST from eBay. Although these tubes are claimed to be "tested good" by fine rated sellers, I am still somewhat concerned about whether it is safe to try tubes on the Stratus without testing them by myself using a tube tester. However, I don't current own a tube tester.

 

What do you guys think? Do you own a tube tester? And, is there any (rule of thumb) eyeball test that can be done? I am also wondering if the Stratus has some built in protection mechanism against malfunctioned (such as shorts in tubes) or incompatible tubes.

 

In addition, as a more specific question, is the RCA 5U4G ST compatible with the Stratus? Specification wise, are they identical to a regular 5U4G? 

 

To my knowledge, ST merely refers to the coke bottle shape of the tube.  If it's a 5U4G then it's completely drop-in. 

 

My rule of thumb on the fleabay is to only order tubes from a place I know or that have been tested and THE RESULTS POSTED.  You never know what you're going to get when it says "tested good" or even "tested 100%."  If they know what they are doing then they will post the results for each triode or section so you know that you are getting internally matching tubes as well - very important.  If they don't post that, then I figure they're amateurs or they're hiding something and preying on amateurs. 

 

In terms of safety, unless you have a tester I think there's little you can do to be 100% sure.  In the case of a driver or output tube, things wouldn't be so bad - the amp just wouldn't work.  The rectifier is the one you need to watch out for.  I blew two rip-off rectifiers in my BA and nearly blitzed one of my ears...

post #527 of 1678
Quote:
Originally Posted by fejnomit View Post

 

To my knowledge, ST merely refers to the coke bottle shape of the tube.  If it's a 5U4G then it's completely drop-in. 

 

My rule of thumb on the fleabay is to only order tubes from a place I know or that have been tested and THE RESULTS POSTED.  You never know what you're going to get when it says "tested good" or even "tested 100%."  If they know what they are doing then they will post the results for each triode or section so you know that you are getting internally matching tubes as well - very important.  If they don't post that, then I figure they're amateurs or they're hiding something and preying on amateurs. 

 

In terms of safety, unless you have a tester I think there's little you can do to be 100% sure.  In the case of a driver or output tube, things wouldn't be so bad - the amp just wouldn't work.  The rectifier is the one you need to watch out for.  I blew two rip-off rectifiers in my BA and nearly blitzed one of my ears...

Thank you, fejnomit, for the helpful input.

 

I was mainly worried about safety of the equipments, in this case the stratus and the DAC connected to it. I didn't think about personal safety...  Now I am thinking a tube tester is probably in order...

 

One of the two 5U4G tubes I bought has a brief testing result says, merely,  "RCA 5U4G ST Shape Good Used Pull. Decent Lettering Tests 56/40 And 56/40 on Calibrated TV7 So Very Nicely Balanced." Does this qualified as "the results" you talked about? Or should I look at tubes with a more detailed testing result?   

 
The other 5U4G was just advertised as "HERE IS AN RCA 5U4G RECTIFIER TUBE. THIS HAS A COKE BOTTLE SHAPED GLASS AND LARGE BLACK PLATES. THIS TUBE TESTS EXCELLENT ON BOTH SECTIONS FOR EMISSION AND SHORTS. DATE CODE IS 448." Now I'm not sure if I should even try it when I receive it, or just skip it.
 
Do you think small driver tubes like the 6QB7A and 6N1P are what we can be LESS worried about? I bought the 6N1P from a Russian seller, who listed very detailed testing results. I get several 6QB7As pretty cheap, at around $3 each plus shipping. The seller of the 6QB7As did not list any test results, but seemed to have an abundant stock of these tubes. 
 
Sorry for bringing up all these details. But I think these questions are perhaps of interest to Stratus owners like me who are not experienced with tubes, and who seek for insights from veterans like fejnomit, third_eye, Budx, and, of course, Donald himself.

Edited by econparanoia - 3/6/13 at 7:27pm
post #528 of 1678

Personally I wouldn't worry about the driver tubes, like you said.  They're cheap anyway...

 

That first 5U4G sounds great - 56 and 56 is a perfectly balanced tube.  The second sounds like it's probably good too.

 

I hope Donald will chime in about the dangers to the amp. 

 

Personally I don't have a tester - I just try what I buy and hope for the best...  WITHOUT HEADPHONES ON WHEN I FIRE UP THE AMP.  Like I said, I learned that one the hard way...

post #529 of 1678

Answering several recent questions:

1. I tried a couple 5U4GB in my Stratus and they work fine. It runs the tubes a little higher plate dissipation but still within the published limits.

2. I haven't tied yet the 274B rectifier.

3. The ST in 5U4G ST refers to the glass envelope shape. This is the classic 5U4G shape.

4. A source for tested 6N1P-EB(EV) is Tube Depot

5. A recent Stratus customer ordered a set of the Psvane 2A3-T and reports they're a nice improvement over the stock Shuguang 2A3B.

6. When buying tubes through the internet, try to find sellers who use more sophisticated tube testers and publish both Ip (plate current) and Gm (transconductance) for both sections of the dual triode. This is better than a figure of merit as found on many testers.

7. The Stratus produces 9.5Vrms with 8 ohm output impedance into a 50 ohm load. Reducing the step-down turns ratio to increase output voltage also increases the output impedance based on the turns ratio squared. It's not clear to me that this will provide improved results with the HE-6. At the recent CHANGfest meet I tried the HE-6 with the Stratus and found the combo played plenty loud for me with headroom to spare. YMMV.


Edited by Donald North - 3/6/13 at 10:47pm
post #530 of 1678
Quote:
Originally Posted by Donald North View Post

Answering several recent questions:

1. I tried a couple 5U4GB in my Stratus and they work fine. It runs the tubes a little higher plate dissipation but still within the published limits.

2. I haven't tied yet the 274B rectifier.

3. The ST in 5U4G ST refers to the glass envelope shape. This is the classic 5U4G shape.

4. A source for tested 6N1P-EB(EV) is Tube Depot

5. A recent Stratus customer ordered a set of the Psvane 2A3-T and reports they're a nice improvement over the stock Shuguang 2A3B.

6. When buying tubes through the internet, try to find sellers who use more sophisticated tube testers and publish both Ip (plate current) and Gm (transconductance) for both sections of the dual triode. This is better than a figure of merit as found on many testers.

7. The Stratus produces 9.5Vrms with 8 ohm output impedance into a 50 ohm load. Reducing the step-down turns ratio to increase output voltage also increases the output impedance based on the turns ratio squared. It's not clear to me that this will provide improved results with the HE-6. At the recent CHANGfest meet I tried the HE-6 with the Stratus and found the combo played plenty loud for me with headroom to spare. YMMV.

Thanks Donald! Looks like I am gonna get to hear the Stratus at a DC meet in May. that is just a day before my b-day. if the sequester does not hurt us too much, I may ask my wife for Stratus for my b-day!

post #531 of 1678
Quote:
Originally Posted by fejnomit View Post

Personally I wouldn't worry about the driver tubes, like you said.  They're cheap anyway...

 

That first 5U4G sounds great - 56 and 56 is a perfectly balanced tube.  The second sounds like it's probably good too.

 

I hope Donald will chime in about the dangers to the amp. 

 

Personally I don't have a tester - I just try what I buy and hope for the best...  WITHOUT HEADPHONES ON WHEN I FIRE UP THE AMP.  Like I said, I learned that one the hard way...

I'll keep this in mind. Thanks for the tips!

post #532 of 1678
Quote:
Originally Posted by Donald North View Post

Answering several recent questions:

1. I tried a couple 5U4GB in my Stratus and they work fine. It runs the tubes a little higher plate dissipation but still within the published limits.

2. I haven't tied yet the 274B rectifier.

3. The ST in 5U4G ST refers to the glass envelope shape. This is the classic 5U4G shape.

4. A source for tested 6N1P-EB(EV) is Tube Depot

5. A recent Stratus customer ordered a set of the Psvane 2A3-T and reports they're a nice improvement over the stock Shuguang 2A3B.

6. When buying tubes through the internet, try to find sellers who use more sophisticated tube testers and publish both Ip (plate current) and Gm (transconductance) for both sections of the dual triode. This is better than a figure of merit as found on many testers.

7. The Stratus produces 9.5Vrms with 8 ohm output impedance into a 50 ohm load. Reducing the step-down turns ratio to increase output voltage also increases the output impedance based on the turns ratio squared. It's not clear to me that this will provide improved results with the HE-6. At the recent CHANGfest meet I tried the HE-6 with the Stratus and found the combo played plenty loud for me with headroom to spare. YMMV.

 

Thank you Donald for your input. 

post #533 of 1678

I remember Budx talked a little bit about the choice of feet for the Stratus.

 

I recently order a set of three alternative feet with wooden pads for the Stratus to replace the stock hemisphere shaped rubber feet. They are as shown in the picture.

 

 

I bought them for the look. And I have to say they look pretty nice on the Stratus. However, I was surprised when I noticed that these feet affected sound quality. After switching to these feet, I've noticed a bit better details, punchier bass, and small improvement in soundstage. They make the Stratus sound thinner though. What surprises me the most, however, is that I found noticeable microphonic after using these new feet and bad, which is very annoying. (Microphonic was never a problem with the stock rubber feet.)

 

Have anyone tried alternative feet on the Stratus? And what's your impression?

post #534 of 1678

There are entire schools of thought and raging debates about the right footers for equipment with some companies charging thousands for complete resonance control systems.  Of them all, I am a huge fan of Mapleshade products.  They are entirely reasonable price-wise when you consider what they do. The micropoint brass footers have an incredible effect on the sound of all components - the bigger the better, although they offer all kinds of sizes.  Most vibration control products wrongly assume the majority of the sound-killing vibrations come from outside the equipment and so they try to isolate it.  After decades of testing, MS has learned that the overwhelming majority of vibrations originate from inside the component itself and therefore any system worth its salt will focus on draining the vibration from the component first and foremost.  This is even more true of tube gear, where transformers and chokes and tubes all resonate.  Check out their website.  I can vouch for the way they work.  I will post some pictures of my set up when I get my camera back from the shop.

post #535 of 1678
Quote:
Originally Posted by fejnomit View Post

There are entire schools of thought and raging debates about the right footers for equipment with some companies charging thousands for complete resonance control systems.  Of them all, I am a huge fan of Mapleshade products.  They are entirely reasonable price-wise when you consider what they do. The micropoint brass footers have an incredible effect on the sound of all components - the bigger the better, although they offer all kinds of sizes.  Most vibration control products wrongly assume the majority of the sound-killing vibrations come from outside the equipment and so they try to isolate it.  After decades of testing, MS has learned that the overwhelming majority of vibrations originate from inside the component itself and therefore any system worth its salt will focus on draining the vibration from the component first and foremost.  This is even more true of tube gear, where transformers and chokes and tubes all resonate.  Check out their website.  I can vouch for the way they work.  I will post some pictures of my set up when I get my camera back from the shop.

Thanks, fejnomit. I'm tempted to try ... These micropoint brass footers are not inexpensive though. Which one did you get for the Stratus? They have both micropoint heavy footers and micropoint mega footers. And there are subcatogries. 

 

Look forward to the photos!

post #536 of 1678
Thread Starter 
Quote:
Originally Posted by econparanoia View Post

Have anyone tried alternative feet on the Stratus? And what's your impression?

 

You have asked the right person - fejnomit has tried almost everything, and he lots of good suggestions. In the meantime, here's a slightly different perspective.

 

When I tried the whole Mapleshade tower, with amp on Isoblocks on maple platform on brass feet, I found that it produced better quiet and imaging, but to my ears there was a filtering effect, an emphasis in the lower midrange. Now I have these under my Stratus

http://marigoaudio.com/isolation-feet/mystery-feet/

Fantastic, but expensive. Blacker, better definition both high and low, no emphasis, and extraordinary 3D effect, which to my mind means that they drain all internal vibration noise and maintain phase coherence. The maker, Ron Hedrich, has professional engineering experience in vibration isolation. I learned about them when Rdr_##  posted in this thread.

 

I found that more than half of that effect can be obtained very inexpensively by placing the Stratus on 3 Mapleshade Isoblocks

http://shop.mapleshadestore.com/prodinfo.asp?number=ISOBLOCK1-ST

with each Isoblock sitting on a Symposium Point Pod

http://www.symposiumusa.com/pointpods.html

 

That works much better than any set of cones or springs or roller spheres, to my ears.

 

Happy Listening!

smily_headphones1.gif

post #537 of 1678

Lower midrange is one of the areas that gets killed by vibration, so it would make sense that this range would be allowed to come through where previously it had been veiled...

I personally don't think the Mapleshades add anything, only take away...  I have heard good things about the Marigos too just never listened...

 

And in answer to which ones, the largest footers have the greatest effect and are the most stable, but $ and space play a role obviously. I have the largest, heaviest ones under my speakers, digital sources and PSUs.  Then I scale down.  Big ones are a little much for the desktop... When you add the height of the biggest isoblocks, platform and footers you're talking about lifting your Stratus as much as 10 inches off the desk!   I use them under external hard drives and monitors too... but I'm perhaps a bit extreme (in all things...)

post #538 of 1678
Quote:
Originally Posted by fejnomit View Post

Lower midrange is one of the areas that gets killed by vibration, so it would make sense that this range would be allowed to come through where previously it had been veiled...

I personally don't think the Mapleshades add anything, only take away...  I have heard good things about the Marigos too just never listened...

 

And in answer to which ones, the largest footers have the greatest effect and are the most stable, but $ and space play a role obviously. I have the largest, heaviest ones under my speakers, digital sources and PSUs.  Then I scale down.  Big ones are a little much for the desktop... When you add the height of the biggest isoblocks, platform and footers you're talking about lifting your Stratus as much as 10 inches off the desk!   I use them under external hard drives and monitors too... but I'm perhaps a bit extreme (in all things...)


Can you guys post some pictures to show how this all looks. Sometimes these things online are shown with nothing else in the picture to let you know their relative size. Would be even better to see them in a real system. THanks!

post #539 of 1678

One of the topics that has not come up too much in this thread is the effect of balanced vs SE and upgrading the HD800 cable in general. I've been rocking the stock cable since getting the HD800. Is it worth re-terminating the stock HD800 cable to a balanced 4 pin, for example?

post #540 of 1678
Quote:
Originally Posted by Cante Ista View Post


Can you guys post some pictures to show how this all looks. Sometimes these things online are shown with nothing else in the picture to let you know their relative size. Would be even better to see them in a real system. THanks!


Yes, pics please!

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