George T. Daughters, K6GTasked "i'd LOVE to know if the RF output would be
the same (close?) if you
>used the SAME screen voltage, and different CONTROL GRID bias to
>obtain equal plate current. is there any chance you could check
>this?
To which Buddy Lumpkin replied:
>Hmmmmm,
> I wouldn't think so considering the screen acts more like a
>throttle and
>the grid will actually change your class of service. Could you imagine one
>tube
>conducting about 350 degrees and the other only conductiong 340? Although
>these
>may both draw the same plate current, this is definately not a matched
>situation.
>I would think that a matched pair of tubes and lead lengths all being the
>same,
>it is probably better to allow different power levels at the plates by a small
>margin then trying to correct it with grid voltage.
>For what its worth
This is what I expect too. In class C or B it might change the waveform a
bit. I am so far into class A with my amp that the screen is the biggest
throttle knob. And drive power. I am not near cutoff. So if i play with the
bias point, I will affect idling current, IMD, and will make the gain
change a small amount. It would probably be a good way to balance plate
current, just that I had an easier knob, separate screen voltage supplies.
This worked fine, but if I ever get the change next week, I might play with
the turnon bias point. No promises though, as I have a tight startup
schedule to meet. I have 360 deg conduction here, no less, in both tubes.
John
K5PRO
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