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Old 14th September 2006, 05:29 AM   #1
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Default A 2a3 Amplifier

Hello everybody, as usual, I am being my indecisive self. I am now exploring using the Power Triode in my next amplifier. I have come to this possible solution for a few reaons.

1.Push-pull 2a3s should give me a little more umph than the my current El34 SET.

2.I don't need very much power (the other people on my floor agree with this more than myself), the fact is that I can't turn anything up very loud at all, so even a 2a3 SET would give me a good power.

3. A Loftin White design looks close to the difficulty level that I am looking to build

4. power triodes look bad a**, who can deny this?

5. Equiping good OPTs to a 2a3 design would be easy, just some $90/pair transcendar 300b transformers would do nicely

I am debating between SE and PP (as always) I want to build PP because its something I have never done before, and the Iron will be cheaper.

I have seen some conflicting numbers regarding the 2a3 as well. Some say that you can get a good 6-7 WPC out of one 2a3 in SE, however the plate dissapation is only 15 watts according to this site does anyone have any solution to this problem?


In addition to any thoughts anyone has, could anyone point me in the direction of a good 2a3 PP schematic? I can find plenty of SE ones, but Push-Pull is proving difficult.


-Moose
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Old 14th September 2006, 06:32 AM   #2
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have you considered fdegrove's (where is he by the way) PP 2A3 found in this forum?
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Old 14th September 2006, 11:14 AM   #3
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Hi Arnoldc

You talk about the PP 2A3 from Fdegrove. I already read about it, but have never seen it - and I am reading a lot from those threads. So, can you maybe give us the thread? Or at least a schematic?

I searched, but well, a search for PP 2A3 gives lots of results - and I am afraid it's not a thread on itself, but rather hidden somewhere.

Thank you

Erik
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Old 14th September 2006, 11:54 AM   #4
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Quote:
I have seen some conflicting numbers regarding the 2a3 as well. Some say that you can get a good 6-7 WPC out of one 2a3 in SE, however the plate dissapation is only 15 watts according to this site does anyone have any solution to this problem?
I think a SE amp with 2a3 output tube is mostly around 3 watts.

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could anyone point me in the direction of a good 2a3 PP schematic?
I'm going to build a SETH PP2A3 one of these days.
http://www.magnequest.com/diy_lessard_circuit_2a3pp.htm
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Old 14th September 2006, 12:11 PM   #5
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There are some 2A3 versions with a rated plate dissipation of 40W - probably those can put some 7W out.

TSETH PP2A3 - a very straightforwarded design, but those small iron thingies ain't cheap!

Erik
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Old 14th September 2006, 12:54 PM   #6
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Quote:
There are some 2A3 versions with a rated plate dissipation of 40W - probably those can put some 7W out.
True...but I don't consider those true 2a3. And they are only made by JJ afaik.

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TSETH PP2A3 - a very straightforwarded design, but those small iron thingies ain't cheap!
True. But then you get something that is "bomb" proof and will last for ever
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Old 14th September 2006, 12:59 PM   #7
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Hi Bas

You are right! I see people selling their diy stuff because they can't get their project to work properly, etc. They lose money, time - and maybe even get a trauma The author of the TTSETH PP2A3 did a very good job keeping the thing simple, very simple, and with a very good building manual (I looked at it).

Erik
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Old 14th September 2006, 05:06 PM   #8
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TSETH PP2A3 - a very straightforwarded design, but those small iron thingies ain't cheap!
If you push enough current, from a low enough rp, into a small mains toroidal (110+110:110) it will make an "excellent" cheap interstage transformer for peanuts.
I have one which uses a ECL82 with plate to plate feedback driving it. A slight bit more complex but very good end result.

Shoog
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Old 14th September 2006, 06:22 PM   #9
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Hi Shoog and all

I was exactly thinking about the toroidal approax while I read about your positive experiences with them (and also from other people who used toroidal either as interstage or as OPT). But your approax is using it as, you say, an interstage transformer. I am curious if a toroidal with two 110V could also be used as a center tapped choke for an application as the TSETH PP2A3: both primaries in series, and the center point grounded? I would say that if it got sufficiente inductance to work as a interstage it would also have enough inductance to act as a center tapped choke, but I am just guessing here.

Erik

Am I right thinking that welbornelabs also have a center tapped choke that can be used for a EL84 push pull? I couldn't find it at their website anymore...
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Old 14th September 2006, 06:26 PM   #10
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Am I right thinking that welbornelabs also have a center tapped choke that can be used for a EL84 push pull?
I've never seen it on their site. But I know Electraprint has got one.
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