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 Post subject: What is so special about a 2A3?
PostPosted: May Mon 06, 2019 7:15 pm 
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Location: Brandon, SD
What makes these worth so much???

https://www.ebay.com/itm/PAIR-CUNNINGHA ... 2907506187


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 Post subject: Re: What is so special about a 2A3?
PostPosted: May Mon 06, 2019 7:45 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Seattle WA US
Power Triode amplifiers, without feedback, are worshiped by audiofools. There aren't many power triodes below the size of transmitting tubes. The 2A3 and its 6 volt heater cousin the 6B4 are popular for this application.

-Chuck


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 Post subject: Re: What is so special about a 2A3?
PostPosted: May Mon 06, 2019 7:50 pm 
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Location: Dayton Ohio
It is the "Single Plate" version that is so coveted.

The standard Dual Section version is worth substantially less and is a better type IMHO.
Basically two 45s in one package.

I'v never seen a single plate 6A3 or 6B4G.
Also the 6 volt versions are less sought after as the 6 volt heaters are more susceptible to introducing hum.

-Steve

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 Post subject: Re: What is so special about a 2A3?
PostPosted: May Mon 06, 2019 7:51 pm 
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We should probably design a Class A tube amp using transmitting tubes for them ......cryogenically treated ones.

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 Post subject: Re: What is so special about a 2A3?
PostPosted: May Mon 06, 2019 8:34 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 524
Location: Monte Vista, CO. USA
Has already been done. I remember seeing a design using the 833A!


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 Post subject: Re: What is so special about a 2A3?
PostPosted: May Mon 06, 2019 8:41 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Orlando, FL, USA
FYI Steve,

There is "no such thing" as a single plate 6A3 or 6B4G. There are a few TungSol and Hytron VT-52 tubes out there factory relabeled "6A3" (hence the myth of the single plate 6A3).

Jim Cross


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 Post subject: Re: What is so special about a 2A3?
PostPosted: May Mon 06, 2019 9:27 pm 
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As Steve said, it is the single plate that drives the price up nuts. The bi-plate 2A3's sell for a lot, but not nearly as much as the single plate.


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 Post subject: Re: What is so special about a 2A3?
PostPosted: May Sun 12, 2019 7:03 pm 
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Joined: Jul Sun 09, 2006 3:11 am
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Location: Aurora, CO 80013
Those will probably find their way to an SET amp on the Pacific Rim. Plenty of audiofool mythology about the mismatch of the two plate structures causing some kind of sonic issues.


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 Post subject: Re: What is so special about a 2A3?
PostPosted: May Sun 12, 2019 7:14 pm 
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If memory serves me right, single plate 2A3 tubes generally have 10 separate filament strands versus only two separate filament strands (each bent 3 times) that are in the double plate 2A3s. This 10 filament setup supposedly allows more current transfer to the plate then does the dual filament setup, therefore, making the single plate 2A3s far more desirable to the serious high end VT audiophiles. This and the fact that the single plate versions are so rare, because they were made for such a short time, that today's prices for such tubes are comprable to that of some Western Electric tubes.

When it comes to 2A3 tubes, RCA and Cunningham tend to be the most respected brand names among the VT audiophile community.

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 Post subject: Re: What is so special about a 2A3?
PostPosted: May Wed 15, 2019 4:32 pm 
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Barry H Bennett wrote:
We should probably design a Class A tube amp using transmitting tubes for them ......cryogenically treated ones.



Have you checked out the application (and price) of a WE 212D? Not frozen - -

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 Post subject: Re: What is so special about a 2A3?
PostPosted: May Wed 15, 2019 4:38 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Livermore, CA
Correct, single plate 2A3 has multiple strands of filament. The tube will still operate with several of these broken. Only problem being broken strands can easily short to grid of the tube. Dual plate variety has a much stronger structure.

Other than price I prefer having the later dual plate version.

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 Post subject: Re: What is so special about a 2A3?
PostPosted: May Wed 15, 2019 10:58 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 524
Location: Monte Vista, CO. USA
phlogiston wrote:
Barry H Bennett wrote:
We should probably design a Class A tube amp using transmitting tubes for them ......cryogenically treated ones.



Have you checked out the application (and price) of a WE 212D? Not frozen - -


I know of a mono amplifier built in Asia based on the STC 212D, driven by a pair of KT-88's. $40,000.00 a pair. They are not built until ordered, of course. :)


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