Tim Williams wrote:

"Patrick Turner" wrote in message
...
The lower Eg2 supply relaxes the load on the screen, and gives lower
thd at the first 20 watts ...

- Even though the load impedance is lower, relatively speaking?

Well if you read the operating specs for 6550 as tetrodes, 440v for Ea,
and lower V fpr Eg2, they get thd down to 0.6% at 40 watts, I have forgot
the exact figures, but the secret is the low Eg2 relative to the anode
supply,
once that supply is over +300v.

There simply isn't any need to have Eg2 so high as they so commonly do
these days,
its just that makers are lazy to make a dropped value of Eg2, which costs
them an R&C.

Most AB1 tetrode/pentode amps DON'T need to have a grid voltage which goes
anywhere
near making grid current; the peak input grid swing is usually a lot less
than the bias
voltage value, AND this bias voltage could be reduced, IF the screen
voltage was lowered,
and maximum power output would stay the same, or only be marginally lower.

Patrick Turner.




Tim

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