• http://www.jj-electronic.sk/pdf/2A3.pdf

I hope the new 2A3-40 can get enough power from a PP amplifier to alleviate foregoing the search for another output tube for more power.

The amplifier that Douglas was working on might be a good PP design for a set of these tubes.

Possibly the 300B SET circuit that you are perfecting could be a good candidate for utilizing the 2A3-40 if so desired?

How much power do you feel is obtainable from these new JJ 2A3-40's?

I did see the KT-77, it looks good to me. I have been trying to talk a freind of mine into trying a set in his Eastern Electric M520.
But, he is set on trying the Mullard clone EL34 from Russia first.

Let us know about these JJ 2A3 tubes if you get the chance to try any? They look like a possible high quality alternative to the Full Music 2A3's. They are priced about the same.

Norris

I tried something similar with 300B I`m experimenting. I used 760-780V ct secondary, CLCLCLC filter/AZ50 rectifier, B+ is about 440V, few V less for the driver. When I disconnected the first cap, I get L-input supply, and B+ is about 312V - exactly what we need for 2A3. We have about 12V voltage drop through the Rw of the primary (OPT), and need Uak=250V through the tube, Uk=45V.
I didn` bother to try 6B4G (I have a few, but no 2A3), I just left 300B in place - it "biased" about -51V, with 250V/56mA through the tube, Rk~900 Ohms.
E180F trioded driver gets about 310V - enough for CCS driver "work" (Ua=200V). The sound was very good, but with less "slam" - I have 89dB/W speakers :-(.
When I`ll finish this 300B amp, I`ll probably post about little changes needed to "convert" it in 2A3 amp, with "traditional" OP, 250V/45V/60mA.

What if it had a 4A filament instead, and maybe 30% more gm? Let's keep mu the same, or perhaps raise it to 5 or so. R_p would be a bit lower and it would probably have a bit more grid-anode capacitance...oh well, nothing is free.

For me, that's just too expensive a tube to play with. Sovtek 2A3 is maybe 75% of that one, at less than a third the price( and I know that they sound good ).
cheers,
Douglas

A 40W 2A3 is the 300B, but with lower voltage filament. This bigger tube should have a bigger filament, perhaps even a thoriated one...:) Imagine a 2A3-ish that glowed yellow/white like an 845, all at 2.5 V. Now that would be one HD filament, no?
cheers,
Douglas

That would be cool.

But, an 845 would probably be better over all.

Building a higher current tube on the heels of the 2A3 is more about maketing. The KR and VV varieties of the 300B comes to mind.

Obviously, the 2A3 is a highly coveted tube that has been produced for close to 70 years. Just imagine all of the 2A3 amplifiers in service over the years. Also, there is a group of the people who want the power of a 300B, but prefer the sonic flavor of the 2A3.

So, why not give it to them, build a modified 300B into a 2A3, right.

There is always a ready made market of audio enthusiast looking for something better.

I am guilty in the persuit of catching my tail. Some times I can get pretty dizzy.

Norris