Say we have an output tranny that presents a load of 10K plate to plate. When just one valve is coducting and the other one is completely cut off, does the one conducting see a load of 2K5, that is to say one quarter of the plate to plate load impedance?
A quarter of the anode load impedance would be surely 40k.
What makes you think the transformer's impedance will change.
What makes you think the transformer's impedance will change.
Yes.
That is the actual load drawn on the tube curves when you design the amplifier.
But it´s a custom (not a rule) , for convenience or simplicity, to label the transformer with the "end to end" impedance, "plate to plate", which being twice the voltage means 4 times the impedance.
Buit in principle at any given moment (supposing Class B of course), current path is from center tap to one *or* the other plate.
Also note that the hi-fi performance (ie. the low and high frequency response characteristics) of the OT changes when operated in class B compared to in a class A configuration, as the plate connects to a different mix of primary inductance, shunt capacitance and leakage inductance values.
Okay, thanks. I was trying to figure out how much extra power output would be possible if the valves were actually able to turn fully on with zero voltage drop from cathode to anode and i was initially getting some silly figures. Thanks all.