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Op points for 750R cathode resistor?

Thanks for the info, Mike.

Now what's bugging me is the 750 ohm cathode resistor on the Mono 8's 300B tube. In order for that to work with the 60mA DC rating for the FS-030, it would need to be run at very low voltage for a 300B -- more like 2A3 voltage, actually.

If I run the 300B at 250Vak, the plate current is 63.7mA. Would that be too high for the FS-030?

If not, then either the voltage is a little lower than that (resulting in much lower output power than he claimed -- ca. 4W instead of 7W) or perhaps George had specially airgapped FS-030s for higher current?

Is it possible that he ran it in the 70+ mA range? That would allow for 300Vak and closer to 7W output power.


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