Bill says:
>However, in push-pull class AB this non-linearity can
>be reduced at crossover (near zero-crossing).
In AB, where conduction is defined as more than 180 degrees(AB1 is conduction of
more than 180 degrees without grid current, AB2 is conduction of more than 180
degrees with grid current), the zero crossing distortion should be negligible,
if present at all. So the push-pull/parallel difference is (or should be) minor.
Where conduction angle drops to 180 degrees, then we see the difference. (Class
B). The conduction angle will be determined by the quiescent plate current, and
is going to be a variable between tubes.
So I don't believe that there will be a measurable difference. If it was that
great, why did Collins use 4 4CX5000 tubes in parallel AB2 in their 45kW rig?
Incidentally, just to really confuse the issue, can anyone explain why many of
Mullard/Philips (and I expect Amperex) have 'Class B' conditions for tubes as
AM linear amplifiers? Said Class B appearing in many cases to be AB2?
73
Peter G3RZP
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