At the primary there are the wires for five connections: +B, two plates (push pull) and the two screens.
At the secondary there are wires for connections to speakers with 8ohms or 4ohms.
They were designed for 5000ohms plate-to-plate effective load resistance, 250VDC plate voltage (+B to plate) and 20Wrms.
The magnetization inductance need be sufficient to get a bandwidth from 20 to 20kHz. This inductance is parallel to the reflected load. Then, roughly, the cut-off frequency will be:
fc = R/(2*pi*L)
L = R/(2*pi*fc)
It can be seen that the size of the output transformer limits the low frequencies response. To get deep bass it is necessary high inductance:
L = 5000/(2*pi*20) = 40 H
Briefly, that is why I got big output transformers (40H!!!).
Firstly I will not use the screen grid connections. I will do some tests and get some measurements. After, I will connect the screen grids wires and compare the results.
Figures below shows the source power transformer. At the secondary there are connections to the filaments of the tubes (6.3V AC) and to the rectifier (about 200VAC).
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