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Old 27th August 2008, 07:35 AM   #1
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Default parallel SE 2A3

I plan to use 2 Sovtek 2A3 tubes in parallel for the power amplifier i want to build.....i am starting from ground zero...
I have found few schematics but still i am looking for more ideas ...
I would be very gratefull if somebody can suggest me some more designs that are really really good... not needed to be cheap - the only goal is to be really good design that sound good.....
thanks a lot for any help...

so parellel SE 2A3 design needed
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Old 27th August 2008, 12:43 PM   #2
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Hi Sunrise,

http://www.audiodesignguide.com/New2A3/new2A3.html

my prefered, only one penthode driver stage, schematic down the page.

or this with more iron

http://www.audiodesignguide.com/my/pse3.html.

Philippe
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Old 27th August 2008, 01:23 PM   #3
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thnx.....
nice projects....
anybody else have some other ideas - everything that is very very good is welcome..
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Old 27th August 2008, 08:44 PM   #4
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hmmmm - not a lot of responses unforunatelly.....

at least this - for parallel 2a3 SE - how many stages??.....2 or 3.... first one to be grounded cathode and the second one cathode follower ... or maybe something like SJS Arcadia amplifier

http://www.users.globalnet.co.uk/~va...es/ARCADIA.GIF

it seems to me that in Arcadia we have a lot more gain than needed for integrated amplifier - but probably i am wrong....not sure....

or maybe something like AN Neiro - there we have SRPP at the input and 5687 as a cathode follower (two 5687 triodes in parallel)....?!

one electron has an interesting project with three 2A3 in parallel....well, i need two in parallel - this might work with two of them right??!
anybody has some comments related 6BL7 tube used in this project....?
http://www.one-electron.com/SEA1_p3.pdf

maybe a loftin white with 12AT7 something like a "Baby Ongaku" from Sound Practices - but i am affraid the this will not be enough to drive 2 pieces of 2A3 in parallel.....




questions questions....
and not many answers....to bad....
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Old 28th August 2008, 11:31 AM   #5
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o.k. - i have found the sch for the parallel 2A3 SE using one D3a penthode connected as triode in front of them....
D3a is a bit problematic to find so i have searched...

I found that E280F is similar and also E180F seems to be usefull....

But there is a problem - can someone suggest me the best operating point for E180F and E280F when connected as triodes and when driving two 2A3's connected in parallel....
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Old 28th August 2008, 12:01 PM   #6
Ciu is offline Ciu  France
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Hello Sunrise !

May be here , where Ciuffolli got them :
http://search.stores.ebay.fr/classic...822955QQsofpZ0

R.C.
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Old 28th August 2008, 04:30 PM   #7
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yes yes.... thanks Ciu...
but i would rather want to use the tube that is not so rare like D3a....

so i have decided to use E180F or E280F (that is actually almost as rare as D3a).....to use them if possible naturally.....

so i am searching now for the best operating point to drive the parallel 2A3...

can somebody help me...

man, this place use to have people that actually helped.... i don't know what happened - maybe summer the vacations are still going and there is not that much people on the web....
don't know,...
but the problem stays to be solved....

so guys, please help if you know how.....thanks in advance...
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Old 28th August 2008, 04:41 PM   #8
kevinkr is offline kevinkr  United States
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Still plenty of people out there willing to help. We are a couple of days away from our end of summer holiday and a lot of people are away.

FWIW I am not a big fan of paralleling anything, particularly DHTs in the output stage of an SE amplifier.. I have heard some VERY expensive PSE amplifiers and have always preferred comparable non PSE designs. For about the same amount of money you could build a 300B based amplifier with the same output power.

The D3A in a DRD based circuit with a 300B would make a good, relatively simple amplifier project I think. (I use D3A for all sorts of purposes.) 3K opt.. 60 - 70mA cathode bias, raw supply about 500V, etc.

If you insist on going the 2A3 route you will want an output transformer with about 1.25K - 1.5K primary, tubes operating at 60mA each (120mA total) at an effective Vp of about 250V. Raw dc with cathode bias of 300V. How's that for helpful.

Jack Elliano of Electra-Print has details of the DRD design on his site:

http://www.electra-print.com/

Obviously he can also make the required chokes and transformers depending on where you are.
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Old 28th August 2008, 05:54 PM   #9
Yvesm is offline Yvesm  France
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Quote:
Originally posted by PhilippeS
Hi Sunrise,

http://www.audiodesignguide.com/New2A3/new2A3.html

my prefered, only one penthode driver stage, schematic down the page.

Yes, but triode strapped

Yves.
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Old 28th August 2008, 06:22 PM   #10
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Quote:
Originally posted by kevinkr
Still plenty of people out there willing to help. We are a couple of days away from our end of summer holiday and a lot of people are away.

FWIW I am not a big fan of paralleling anything, particularly DHTs in the output stage of an SE amplifier.. I have heard some VERY expensive PSE amplifiers and have always preferred comparable non PSE designs. For about the same amount of money you could build a 300B based amplifier with the same output power.

The D3A in a DRD based circuit with a 300B would make a good, relatively simple amplifier project I think. (I use D3A for all sorts of purposes.) 3K opt.. 60 - 70mA cathode bias, raw supply about 500V, etc.

If you insist on going the 2A3 route you will want an output transformer with about 1.25K - 1.5K primary, tubes operating at 60mA each (120mA total) at an effective Vp of about 250V. Raw dc with cathode bias of 300V. How's that for helpful.

Jack Elliano of Electra-Print has details of the DRD design on his site:

http://www.electra-print.com/

Obviously he can also make the required chokes and transformers depending on where you are.
i thought the summer holidays are the problem heheheheh.....i know that there is allways a lot of smart people that know how to help.... hehehhehe....
related the project.... yes - i would like to go with 2A3 in parallel - rather than with one 300B....
but i was asking for the good operating point for the E180F (or E280F) that can drive 2 2A3's in parallel.....or at least a good operating point for those two driver tubes mentioned.... i figure that E180F would be enough - in triode connection it would probably go with 50Vrms output for 1V (or so) input and that on 10-11mA bias current....right or not???

i am asking questions for E180F (or if it will not be enough for E280F) - hehehehehe



Quote:
Originally posted by Yvesm


Yes, but triode strapped

Yves.

of course.... triode connected
hehehehehehe
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