>R. Measures wrote:
>>** Indeed. ... getting back to g-g operation for a tube with a max.
>>g1 rating of 2mA, I would not try it. Even with a stripe-cathode and
>>aligned grid, typical grid currents are c. 100mA in g-g triodes. .
>
>The problem seems to lie in an over-casual use of the term "g-g".
>
>Once again: you can safely operate *any* tetrode in class AB1,
>cathode-driven. The requirement is that the control grid has the correct
>negative bias, and the screen has the correct positive voltage. These
>voltages are exactly as recommended by the manufacturer for class AB1,
>grid-driven.
>
>For cathode drive, both grids must be grounded to RF. But in order to
>apply different DC voltages, at least one grid cannot be connected
>direct to chassis - it has to be RF-grounded through a bypass capacitor.
>Because the recommended voltages are measured relative to the cathode,
>all three power supplies (anode, screen and control-grid bias) generally
>have to 'float' relative to the chassis potential.
>
>The correct DC bias voltages ensure that all the DC "grid" current goes
>to the screen, and *none* to the control grid... in other words, correct
>class-AB1 operation.
** Ian -- Is the power gain with cathode-driven and no g1 current the
same as with 'super-cathode' drive -- i.e., c. 5?
- If g1 is never to be driven more positive than the cathode potential,
why not connect it to the cathode?
>...
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