A "regulated" screen voltage does not make a perfect linear amplifier.
Examine the "Ultra-Linear" (also known as the Williamson) amplifier design.
A few of these audio amplifiers were sold by Heath and others. The circuit
necessarily uses a screen dropping resistor and could not use a screen
regulator of any design.
The Ultra-Linear design is reputed to have less distortion than any other
tube amplifier. I used to own one and although I never ran any distortion
tests on it, it was simply marvelous to listen to.
Yet very few were sold commercially. Most people do not understand how they
work. Yet, they work very well. You will not see a screen voltage
regulator circuit in any Ultra-Linear design.
After looking at both the Ultra-Linear design and the G2DAF design, I now
realize it is possible to use knowledge from these designs to apply to a
grid driven rf amplifier. It will not and can not use a screen regulator.
Just like the Ultra-Linear design, it will have inverse feedback. I will
build such a circuit to test sometime in the future - which is exactly the
point of discussing and understanding the G2DAF circuitry - knowledge.
But, there are some who will stick their head in the sand and forever be
convinced that things will not work because they saw or heard a bad example.
Colin K7FM
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