"What I can,t figure is why one would want to run a tetrode in G-G where a
triode is the very ticket for it? To me, if one wanted to run a tetrode,
they would want to run it the way it was designed to run in the first
place."
There are some very good reasons to run a tetrode in grounded grid. Using
the 4Cx1000A as an example, running it grid driven will result in
unacceptable distortion products. To get acceptable levels you must
increase the inverse feedback. Grounded grid inherently provides feedback
and will improve the distortion products by about 6 db. Collins ran the
30S-1 with a 4CX-1000A in grounded grid, but also added negative feedback.
The result is an amplifier significantly cleaner than the tube itself.
A second reason is cost and availability. A 3-1000 is almost impossible to
find. New, they are probably $750. However, a 4-1000 run grounded grid is
available used for about $100. The only penalty is a requirment of 1,000
volts additional plate voltage. But, the proper ham can build a power
supply with an additional 1,000 volts for less than the $650 price
difference.
Not many years ago, I bought a used amp with a 3-1000 final. I then sold
the tube for more than I paid for the amp and plugged in a 4-1000.
73, Colin K7FM
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