Impedance for idiots????

[eschertron]

^This is an important point (and provides the answer to pdf’s question). In audio, your not concerned with impedance matching, because maximum, efficient power transfers is not a concern (outside of a few important cases, ie.driving a speaker load). It’s the signal voltage that are the concern in interstage coupling, as mentioned above.

And this comes back 'round to the OP's inquiry. In the typical preamp interstage, we desire the load impedance to be much higher than the source impedance in order to not cause current to flow (current flows in impedance bridging); the high impedance means low loading, and the result of that is the AC load line doesn't rotate very much. It's when we unavoidably load down the plate with things like tones stacks or smallish grid leaks that loading - and AC load line rotation - matters.