[MrFixr55]

Hi Folks,

Philco did the same trick on my 41-250 and, I'm sure, on a lot of other sets of the same vintage. On the 41-25o, they put a resister between the "B" Output Tube (for a lackof a better designation) Screen and the A Output Tube Screen. B+ was connected to the B Tube. This allowed for "sampling" of the output of the A Screen and that "sample" was fed to the grid of the B Output Tube. In a way, this is the same way the average Phase Invertor Tube of the time worked. The "Cathodyne" Phase Invertor came later. I would think that when everything was in spec, if the signal was applied at the same strength and 180 Deg out of phase to the B tube, then the circuit should do everything a push-pull output should do- more power, less 2nd and 4th harmonic distortion.

I can't remember what brand guitar amp I saw the same thing on, but I have seen the same technique in at last one. This technique was also in some electronic text I read. It seems it was more popularly used by Philco than in others, but I think that they used the other types on their higher end radios and/or abandoned the technique post war, or maybe it did not work well on beam power tubes? 41s (6K6) and 42s (6F6) are pentodes.