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Tim Williams
 
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"at" wrote in message
...
What things should be considered to choose the best output transformer for

a
given tube and situation?


Maximum power, or nearby with pentodes, minimum distortion. Triodes, just
max. Po (since min. distortion comes at infinite Rl, which is rather
useless).

Reason there's one "best load impedance" is because the tube will only draw
so much current at a given voltage and signal level. Same applies to
transistors as well, because they have the same curves as pentodes, but it
isn't thought of as such because they have such a contrasting design
culture.

Output impedance has absolutely nothing to do with it; that can be corrected
with negative feedback. The "perfect voltage source/source impedance" Zo
model works great for anywhere but when either voltage or current levels are
pressed to their limits for the amplifier.

Tim

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