GEC BC506 Non electrolytic capacitor question

[Kalee20]

It's hard to imagine just looking at the schematic exactly how this works, but at nearly zero signal there is maximum gain and then there is a point where it gets non-linear on larger signals.

Well, the gm of a transistor is proportional to collector current - so if the transistor is biased back to a small collector current, then it'll have a low gm and hence low gain. If it is passing a high collector current then it'll have high gain.

This of course is valid if the input signal is relatively small (tens of millivolts).

But it relies on the transistor passing some collector current, which it can only do if the base is biased 'on' ie negative with respect to emitter (PNP transistors here!). It can't ever be reverse biased because that would well and truly cut off the transistor - except for super-large input signals, working in Class C, which as above is untenable for a linear amplifier.

So I'm still opining that the base won't ever go positive, and the voltage on the elcap won't therefore ever reverse.