The higher the load impedance on a triode the more horizontal the load line will be. With a CCS in the plate circuit, the plate load impedance becomes the value of the grid resistor in the next stage.
As horizontal load line on a triode gives the most gain and the least harmonic distortion.
In the example above we see that the voltage swing with a 8 volt peak to peak input signal is larger with better symmetry comparing the plate voltage change from the red idle point to the green (horizontal high impedance load line) vs. blue (lower plate load impedance load line).
Tre'
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