Again , 0,43mA through a tube seems too little to me , the 500 ohm resistor is just there to give you a headache !!!

This old schematic shows again that nothing is new , it uses a capcitor to shunt the audio return path of the 2A3 from anode to cathode across

the transformer , avoiding the cathode returnpath : TODAY this is known as the ULTRAPATH connection .

 

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