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A convenient way to find the actual class of operation is using a loadline calculator like this: https://www.vtadiy.com/loadline-calc...ge-calculator/
In pure class A the loadline is a straight line through the operating point. With class AB the loadline is kinked, the lower part corresponding to class A and the upper (steeper) part corresponding to class B.
Using typical AC30 conditions (adapted to 2 tubes) as B+ = 310V, Ip =47mA, Raa = 8k, one can see the typical class AB loadline kink at Ip = 2x47mA.
This crossover point corresponds to an output of 8.8W (double that for 4 tubes).
Summarizing this means that an AC30 works in class A up to an output of around 18W and shifts to class B above.
Without changing the bias, pure class A would be possible up to B+ = 226V, giving an output of 8.9W for 2 tubes.
In pure class A the loadline is a straight line through the operating point. With class AB the loadline is kinked, the lower part corresponding to class A and the upper (steeper) part corresponding to class B.
Using typical AC30 conditions (adapted to 2 tubes) as B+ = 310V, Ip =47mA, Raa = 8k, one can see the typical class AB loadline kink at Ip = 2x47mA.
This crossover point corresponds to an output of 8.8W (double that for 4 tubes).
Summarizing this means that an AC30 works in class A up to an output of around 18W and shifts to class B above.
Without changing the bias, pure class A would be possible up to B+ = 226V, giving an output of 8.9W for 2 tubes.
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