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Old 23rd February 2011, 03:41 PM   #1
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Default 2A3 Amp schematic suggestions?

Thinking of constructing a 2A3 based amp.

Design aims would be:

1) Single ended topology

2) Simplicity - minimum number of components / stages with the best achievable sound quality.

3) No feedback if possible. If feedback needed, limited to local feedback.

4) Low cost - no exotic tubes or transformers.

Any suggestions by the great tube gurus out here?
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Old 23rd February 2011, 03:51 PM   #2
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by quikie22 View Post

4) Low cost - no exotic tubes or transformers.
I thought 2A3 was exotic
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Old 23rd February 2011, 03:54 PM   #3
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Quote:
Originally Posted by tinitus View Post
I thought 2A3 was exotic, being low power, and relatively high cost
LOL!! You got me there!!

I meant other tubes involved except the 2A3.
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Old 23rd February 2011, 03:57 PM   #4
tinitus is offline tinitus  Europe
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ah, driver tube, ok
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Old 23rd February 2011, 03:59 PM   #5
chrisb is offline chrisb  Canada
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Quote:
Originally Posted by quikie22 View Post
Thinking of constructing a 2A3 based amp.

Design aims would be:

1) Single ended topology

2) Simplicity - minimum number of components / stages with the best achievable sound quality.

3) No feedback if possible. If feedback needed, limited to local feedback.

4) Low cost - no exotic tubes or transformers.

Any suggestions by the great tube gurus out here?


There must be literally hundreds of schema out there (I've yet to hear a 2A3 SE or P/P that I didn't like), but it would hard to go wrong with

Angela Electronics:

Simple SE 45/2A3 Amp for First Time DIYers

Bottlehead Stereomour:

Stereomour Stereo Single Ended 2A3/45 Integrated Amplifier Kit


Electraprint's DRD:

Electra-Print.com 2A3 DRD Amplifier

(of course Jack would be happy to supply the iron)

for those with more adventurous spirit and deeper pockets:

MagneQuest DIY: Jean-Francois Lessard's 2A3 SETH SA-240 Push-Pull Monoblock



and by non-exotic, it's assumed you mean current/recent production entry level priced ( i.e. Sovtek /EH/ Valve Art etc.) as opposed to either NOS RCA/Cunningham or Shuguang Treasure series
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Last edited by chrisb; 23rd February 2011 at 04:04 PM.
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Old 23rd February 2011, 04:03 PM   #6
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by quikie22 View Post
LOL!! You got me there!!

I meant other tubes involved except the 2A3.
EL84

http://www.tubemaster.de/e-diy-EL842A3.html

looking up EL84 drive 2A3, this Aikido drive 2A3 popped up

http://singlevalve.web.fc2.com/Aikido2A3/Aikido2A3.htm
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Old 23rd February 2011, 04:24 PM   #7
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Quote:
Originally Posted by chrisb View Post
and by non-exotic, it's assumed you mean current/recent production entry level priced ( i.e. Sovtek /EH/ Valve Art etc.) as opposed to either NOS RCA/Cunningham or Shuguang Treasure series
Spot on chris :-)

Thanx for all the links. Will go through them.
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Old 23rd February 2011, 04:26 PM   #8
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Originally Posted by tinitus View Post
EL84

Tubemaster Labs Homepage

looking up EL84 drive 2A3, this Aikido drive 2A3 popped up

Aikido driven 2A3 Single Ended Amplifier
Thanx tinitus. Currently am running aikido as my line-stage, so it would definitely make sense to use another aikido :-)

EL84 is also another fave tube of mine (and I have several extras lying around), so definitely another possibility.
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Old 23rd February 2011, 04:34 PM   #9
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Hi!

You might want to have a look at the single ended amplifier concept posts on my blog. The schematics I published are with 6CB5A output tube, but it can be replaced with a 2A3 with the same driver stage. In fact I have built it with 45/2A3 already. I'd recommend the Lundahl 1663 as output transformer.

In upcoming posts I will show how to convert this concept to DHT output tubes

Best regards ... Thomas
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Old 23rd February 2011, 04:45 PM   #10
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My version of SE 2A3 is:
- 9 - 10 passive elements per channel.
- two stage ampl.
- No FB.
- pretube E180F Phillips, or 6E5P /Russian tube/
- output transf Hammond 125FSE /70$/, guarantied 20 20000 Hz. I measured with scope and signal generator /don't see that brand wrote 150-15000, ha-ha. This trani 90 ma, 10 sq. cm is for 300B, 2A3. 6L6, EL34, it was first brand's recomendations 4 years ago....Now they recommend for 2A3 trany for 200 and more $....ha, brands trick!!!!./
- 2A3 RCA /90$ each.
- chase Hammond Alu.
I can post my schematic.
This ampl. kicked 2 Mosfet Hitachi with "brushes".
https://picasaweb.google.com/azazell...34527250384578

Last edited by azazello; 23rd February 2011 at 04:57 PM.
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