"Henry Kolesnik" wrote in
message ...
I haven't tested the impedance yet, need to find a pot,
but I noticed that the two 6F6es are connected as push pull
triodes. I wonder why they didn't use a pair of 45s?
Hank

The 6F6 was a much newer tube at the time and is a
metal, octal base, tube. It has sufficient plate dissipation
and works well as a triode audio amp. The 45 also has 2.5V a
filament and is not a heater type cathode, meaning that it
needs a DC filiment source for audio use.
Triode audio amps have lower source impedance than
tetrodes when used without feedback which is an advantage in
driving variable load impedances like loudspeakers, and
generally more pleasant overload characteristics. The 6F6
was a good choice at the time and could also be used as a
driver.


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Richard Knoppow
Los Angeles, CA, USA