DNA Stratus 2A3 amplifier - first impressions - Page 7

Quote:

Originally Posted by jc9394 


Thinking about Donald's offer? I highly recommend it, when I had the Sonnet, it kick the WA6SE's ass left and right. The WA6SE did not last a week in my house.

Yes and thanks for that jc , I am thinking about it seriously.

Quote:

Originally Posted by dannie01 

 

Yes and thanks for that jc , I am thinking about it seriously.

Oh, did I said that it with HD800?  It is a perfect match...  I only sold it to fund the WA22 purchase from someone.    Actually, I'm thinking on this too.  It takes the SE out of my DAC while beta22 takes the balanced out with loop out to WA22.  How perfect...  Only if I have the funds...

We do have the rectifier already and 2A3 tubes are cheaper than 300B.

Donald, can we use GZ34/37, EML 274B, and USAF 596?

Edit: Oops, forgot the quote.  I am referring to Donald enjoying the K1000s.

Probably safe to say he is.  So weird looking but so cool at the same time those K1000s are.  Knowing the Stratus has an output labeled specifically for them makes me want them.  I'm just that simple.  

I would guess that a 45 tube Stratus would be great for high impedance, high efficiency phones.  A more three dimensional HD 800?  

Alright, back to reality.

Quote:

Originally Posted by Eee Pee 

I was thinking about this sentence today because I recall an amp from Don Garber's of Fi to be able to use both tubes if you change the rectifier.   The Fi X.  And I'm guessing it isn't optimized for either tube?  That's too bad.  It does get nice reviews though.

The Fi X originally was a 2A3-based amplifier. I believe Don will make a custom version optimized for the 45 - you need to ask him.

Quote:

Originally Posted by budx3385 

 

and I've been thinking about your comment here, EeePee. I finally pulled the K1000 out of my closet, and it sounds amazingly realistic driven by the Stratus. (Now I really need to fix its extension cable, cuz its 6 ft original does not reach my listening chair.) If I remember correctly, driving the K1000 was one of Donald's design aims for the Stratus. I'm guessing he is enjoying that combo every day now!

Yes, around 4 years ago I heard a friends K1000 and I was immediately hooked! I tried them with an Audio Note Kit One 300B amplifier and the combo sounded good. I love the 2A3 and have them driving my speakers, so I thought it could be really cool to develop a 2A3 amp with the proper output to drive the K1000.

Quote:

Originally Posted by Eee Pee 

Edit: Oops, forgot the quote.  I am referring to Donald enjoying the K1000s.

 

Probably safe to say he is.  So weird looking but so cool at the same time those K1000s are.  Knowing the Stratus has an output labeled specifically for them makes me want them.  I'm just that simple.  

 

I would guess that a 45 tube Stratus would be great for high impedance, high efficiency phones.  A more three dimensional HD 800?  

 

Alright, back to reality.

The 45 has higher plate impedance and lower power output. In order to load it properly you need an output transformer with twice the primary inductance as you would for the 2A3. Now assuming you use the same turns ratio on the primary:secondary windings, you'll have twice the output impedance. You can use a greater step down ratio to match the output impedance of the 2A3 but then you're giving up drive voltage. I wanted to keep the output impedance reasonably low to improve the drive on lower impedance headphones (and headphones which prefer a low impedance source) while providing sufficient drive voltage for lower efficiency headphones. The balance of these factors and fondness for the 2A3's sound are what lead to the Stratus' particular configuration.

Quote:

Originally Posted by jc9394 

 

Oh, did I said that it with HD800?  It is a perfect match...  I only sold it to fund the WA22 purchase from someone.    Actually, I'm thinking on this too.  It takes the SE out of my DAC while beta22 takes the balanced out with loop out to WA22.  How perfect...  Only if I have the funds...

Your Beta22 is equip with this function? 

Quote:

Originally Posted by jc9394 

We do have the rectifier already and 2A3 tubes are cheaper than 300B.

 

Donald, can we use GZ34/37, EML 274B, and USAF 596?

X 2 

Quote:

Originally Posted by jc9394 

We do have the rectifier already and 2A3 tubes are cheaper than 300B.

 

Donald, can we use GZ34/37, EML 274B, and USAF 596?

I don't recommend the GZ34 & 37 because they are indirectly heated and I take the high voltage from the center tap on the filament winding. The Stratus needs directly heated rectifier tubes. 5R4GY can be used but will cause reduced plate voltage and current through the signal tubes. U52 can also be used. the EML 5U4G should be fine and I believe the EML 274B can work too because I use a current inrush limiting resistor immediately after the rectifier into the first capacitor. the USAF 596 has external anode pins and would require modification of the amp to accommodate, so I don't recommend it.

Revered 

Quote:

Originally Posted by Donald North 

I don't recommend the GZ34 & 37 because they are indirectly heated and I take the high voltage from the center tap on the filament winding. The Stratus needs directly heated rectifier tubes. 5R4GY can be used but will cause reduced plate voltage and current through the signal tubes. U52 can also be used. the EML 5U4G should be fine and I believe the EML 274B can work too because I use a current inrush limiting resistor immediately after the rectifier into the first capacitor. the USAF 596 has external anode pins and would require modification of the amp to accommodate, so I don't recommend it.

What if I have an external adapter for it?  

I want to know, too.

BTW, nice pic, jc. Is it taken by the D8000.

Quote:

Originally Posted by dannie01 

I want to know, too.

 

BTW, nice pic, jc. Is it taken by the D8000.

You mean D800?  I wish, still in waiting list... 

Quote:

Originally Posted by preproman 

Revered 

Intentional?

Hehe, sorry for typo.