Since I just finished an amplifier which uses this tube, I thought it is a good time to present the 2A3 as tube of the month.
The 2A3 is a directly heated output tube which enjoys continued popularity over the decades and is even still made to day by various manufacturers.
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And for comparison curves from an actual tube on the curve tracer:
The plate curves are as linear as you can expect t from a directly heated triode. Ideal for no feedback amplifiers.
RCA probably made most of the 2A3s.
Here we see the typical bi plate structure, the most common variant of 2A3.
Some details:
Another variant from RCA:
Slightly different construction as can be seen on the top:
An older RCA with engraved base:
Again different construction:
Some close ups:
A version with red printing on the base:
Similar construction as in one of the tubes shown above:
But with grey plates:
A 2A3 made for the military:
2A3 produced by Sylvania, probably the second largest maker of this tube after RCA:
Here we have a dual plate variant in which the two anodes are separate (but internally connected of course:
Here the two separate plates can be clearly seen:
Yet another Sylvania:
Here we have a special version made by Sylvania called 2A3W:
This is a ruggedised version made for the military or industrial applications.
It comes in a straight sided bottle. It had also a 4-digit industrial designation: 5930. Here in comparison to the regular 2A3:
Zenith and Philco usually sourced their tubes from Sylvania:
Next we have a bunch of 2A3s made by General Electric:
This one looks suspiciously similar to one of the Sylvanias shown above:
Cross branding was very common, manufacturers sold tubes to each other.
The next one also looks like it's been made by another company and simply rebranded:
This one has the black coating in the middle as was mainly done by Ken-Rad.
Another two GE branded tubes:
These two look like RCA made.
Next we have some rarely seen 2A3, branded Philips Miniwatt:
Both in sealed boxes, so truly NOS NIB:
I broke the seal of one of the boxes to have a look at the tube:
Seems to have been made by RCA.
Also says made in USA:
Marconi:
A Marconi with the same black coating as the GE shown above:
Two National Union 2A3:
Arcturus:
Different style Arcturus 2A3:
Raytheon:
Westinghouse:
And lastly Tung-Sol which also used black coating:
The rather dim oxide coated filaments of the 2A3 do not produce much of a glow:
A nice triode which deserves it's popularity!
Best regards
Thomas
IMHO, tube of century, not just month :-)
ReplyDeleteAny single plate in your stash?
ReplyDeleteNo - as written in the post...
DeleteAny chance of an Elorg 2A3?
ReplyDeleteNot within the next 2 years at least
DeleteI second Peter!!!
ReplyDeleteThe most user/listener friendly electube!
ReplyDeleteHave you tried any of the Japanese made 2a3? Often labeled UX-2a3 from Matsushita, Toshiba/Mazda or NEC? Not sure if there all made by one of those manufacturers or if the specs are the same with the UX prefix.
ReplyDeleteno
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