[TA Forbes]

Depending on how you drive the plate V and bias of the 6A3, you can achieve considerable power out. I have heard of modern tube amps that use 2A3s in PP that are putting out 40 W power. I believe my Sparton 1568 puts out 20W with two 2A3s and 360V plate, 64V bias. Additionally, the Sparton has iit's own power xfrmr and 5X4 rectifier dedicated to it's 2A3 output tubes.

(The 2A3 and 6A3 are the same except for the fil V)

BUT back to the original question.... from what I have read there were some folks back in the '30s that believed that a triode produced a better, clearer sound. I believe that this resulted in the many sets made by many producers in the late 30s that featured 45 and 2A3 tubes in sets that had 6V fil V on the rest of the tubes, except perhaps the rectifier. Later 6V fil triodes like the 6A3 and 6B4 made is easier (and cheaper) to d this, as the power transformer utilized would not require a 2V fil winding.