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RE: Explanation needed for 2a3-40

h2o, hi. The JJ 2A3-40 follows the success of the JJ 300B. It appears the JJ 2A3-40 shares the same anode structure and the same rugged glass envelope. The curves of each are dissimilar so by inference grid pitch and geometry (spacial relationships of cathode, grid, anode) are dissimilar. The filament V is 2.5 - standard for 2A3. One could theoretically operate the tube much harder - higher B+ and more current across the tube than an OS 2A3. If one operates the JJ 2A3 like an OS 2A3 one is essentially "loafing the tube" with implied benefits including longer life. Do some research on the operation of Class A triodes. The Radiotron Designers Handbook is excellent. One could operate the tube at higher B+ and more current but this might not (emphasis Not) yield improved sonics. There is another advantage the JJ-2A3 has over OS 2A3. The JJ-2A3-40 anode structure is one piece. Early 2A3 production was like this but required a more tedius & time consuming process to build than, say, a 45. Eventually the "mono plate" single anode structure 2A3 was reworked to resemble two Type 45 tubes, anodes back to back, operating in parallel in one envelope. Similarly the Type 50 has a large single chimney anode, was labor intensive to build, and was priced accordingly. In the late 1920's the 45 was being produced in ever increasing numbers to keep up with the exponentially growing radio receiver market. I think it was a natural to put two 45 assemblies together in one envelope to make a bi-plate 2A3. Just for grins check the price of used mono plate 2A3 in today's market. The JJ 2A3-40 is a bargain when looking at performance versus price.


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  • RE: Explanation needed for 2a3-40 - elektron 11/26/0712:12:25 11/26/07 (0)

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