Thanks for those pointers Kalee20. What I found interesting whilst experimenting was that secondary load had less effect on Pout than I'd have thought. I'd assume that the higher the reflected primary Z the higher Vout, the same as using a bigger anode resistor. This was the case to a point,that is until Imax was reached.
Another thing I noticed was how the load line for all the Class A stages I drew fell well below the knee, which for a PP OP stage is a big no no.
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In practice, most of what are called "class A single-ended" outputs [the sort of 6V6/EL84 things you find in broadcast radios or record-players] are actually working in Class-AB1
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Interesting. I found I couldn't get the full voltage swing on the grid, EG a 6AQ6A was biased at -12v, but Vg1 was only 2v ish RMS, the OP stage clipped way before the grid could swing more negative, that and the load lines I drew only reached as far as Vg1 -2 or -4v grid lines.
I also found the OP of the triode gain stage started to get distorted, as seen from g1 on the pentode/BT. Couldn't really determine whether this was down to grid current of cutoff.
I still haven't nailed all the nuances of Class SE design, there's a lot going on, it seems to me this OP stage and Class is very touchy,very tricky to get right. In comparison Class AB1 PP is a doddle.
Thanks again all for your IP, Andy.