> The tubes (3-500z`s) were from RF Parts. I replaced (Henry
> 3K repair
> job)some low hr Eimacs that one had developed a grid to
> filament short. Gain
> was compared to a nos pair of Eimac`s.Higher zsac for a
> given Ep and close
> to 10% more output for a given value of drive.Jim..
The trend is generally this:
Higher quiescent current for fixed bias and HV generally
indicates lower mu, not higher. It takes more negative bias
to reduce anode current as mu is increased.
Lower mu generally indicates higher input impedance, more
negative feedback, and less gain in a g-g amplifier. In a
g-g amp gain is mostly determine by the ratio of load
impedance to driving impedance, and higher mu tubes
generally have a lower cathode drive impedance.
It would be interesting to see what the Chinese are doing
differently when they make the tubes. Maybe the tubes are
lower mu and lower driving impedance?
73 Tom
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