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Old 9th May 2004, 05:49 AM   #1
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Default single ended 2a3 project

i am planing to do a 2a3 project this summer.


any one have good sch related to single ended 2a3?

pls give me some info.

i want to use 12axt/ u7/t7 to drive it.


is it possible?

THANKS
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Old 9th May 2004, 06:53 AM   #2
Fuling is offline Fuling  Sweden
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I would have aimed for something more "exclusive" as input/driver.
Maybe a 6SN7, 6C45, EC86 or something.
Just my two cents.
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Old 10th May 2004, 06:30 AM   #3
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Hey,

what speakers u gonna use ? 2A gives u a Watt or 4 so u have to use some damn good speakers why not try a 300b the price is allmost the same and these gives u 12W. But the speaker choise is not that difficult.

Greetz, Lukasz
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Old 10th May 2004, 10:24 AM   #4
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Hi,

Quote:
a 300b the price is allmost the same and these gives u 12W.
That's only true for the high dissipation 2A3s, a "normal" 2A3 would cost about 1/3 the price of a 300B.

Cheers,
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Old 10th May 2004, 11:15 AM   #5
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Default Re: single ended 2a3 project

Konnichiwa,

Quote:
Originally posted by takashi
i am planing to do a 2a3 project this summer.
any one have good sch related to single ended 2a3?
Literally hunderts of schematics. You need to define what you want.

Quote:
Originally posted by takashi
i want to use 12axt/ u7/t7 to drive it.
This would not be my favourite way of doing things, but (for example) a 12AT7 SRPP could be used. Of course, you'd be better off using a 5965/12AV7/12AZ7 replacement for the 12AT7, plus it is easier to find really good quality ones of these at sensible prices....

A well documented 2A3 project that could use the 12AT7 or 12AU7 (even 12AX7) in SRPP is shown here:

http://www.positive-feedback.com/Issue1/kismet.htm

The schematic is this:

Click the image to open in full size.

The changes for the 12AT7/12AV7 or 12AU7 and even 12AX7 are nominal, simply make sure the pinning is right.

If you add a switch for the Filament connections you could even use Valves more less compatible with the 6922/6DJ8/ECC88/E88CC/E188CC/7308 et al (also ECC85/6AQ8).

Sure, non of the Valves is maximally optimised, but you can experiment a lot with valves. You could also make the SRPP Cathode resistors switchable (or use a stereo pot 1k+1k linear in series with a 330R resistor each to "dial in" the best sounding operating point.

Even better, you can use the Amplifier also with 45's if you like, so it's quite versatile and a good "learning" excercise.

Sayonara
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Old 10th May 2004, 11:35 AM   #6
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Default SRPP?

Hi,

For the first stage to work as SRPP you'll need to connect the bottom of R3 to the grid of the top triode.

Cheers,
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Old 10th May 2004, 11:53 AM   #7
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Hey,

If u check out the KR 2A3 end de XLR 300B the price is almost the same ! And thats a nice triode so the price herefore isnt 1/3 !

http://www.blackforestaudio.de/KR_Rohren/kr_rohren.html

Greetz, Lukasz
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Old 10th May 2004, 12:03 PM   #8
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Hi,

KR tubes aren't adhering to original standards so it would hardly be a 2A3 or a 300B for that matter.

Good monoplate Russian 2A3s can be had for less than 25 Euro each.

There's little point in having a 2A3 circuit designed around the original spec and than fit a 40W max. dissipation triode.
EDIT: I just noticed that the KR is rated at 18W max. diss., so it's even less of a "bargain".

Besides KR tubes are sooo overpriced and flaky that I can't think of anyone in their right mind forking out that kind of money.

Cheers,
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Old 10th May 2004, 12:10 PM   #9
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Yes IDD you can get it cheaper but I still think that a KR has something more ! I saw her once and I had to have her ;-) if u konw what I mean ! But a nice Sovtek or Svetlana is good to ! I thinkt that he should start with some cheaper triodes to get the feeling and after all u can still change

Greetz, Lukasz
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Old 10th May 2004, 01:25 PM   #10
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Default Re: SRPP?

Quote:
Originally posted by fdegrove
Hi,

For the first stage to work as SRPP you'll need to connect the bottom of R3 to the grid of the top triode.

Cheers,

Holla Paco,


That's what I thought

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