A Class AB1 grid-driven linear amplifier requires a tube-type that can
utilize peak cathode emissivity when the grid-to-cathode voltage is zero
volts. Low-Mu triodes typically fall into this category. Medium-Mu and
high-Mu triodes do not. Virtually all modern tetrodes and pentodes are
suitable--provided that maximal screen and anode voltages are applied. .
A Class AB2 grid-driven linear amplifier requires a tube-type that is
designed for very low grid interception of primary electrons. Suitable
tube types are the 4cx600J/A and the 4cx1500B. However, the recommended
amount of grid current for these tube types is under 1mA.
A Class AB2 cathode-driven linear amplifier requires a tube that is
capable of utilizing emissive capability without an overly-large driving
voltage requirement. High-Mu triodes and triode-connected tetrodes and
pentodes are suitable. Low-Mu triodes are not. Medium-Mu triodes are
semi-suitable--provided that a large amount of drive power is available.
note: None of the above applies to amplifier "experts".
Rich---
R. L. Measures, 805-386-3734, AG6K
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