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On Wed, 15 Dec 2004 17:54:47 -0600, (John Byrns) wrote:
Hi Ian,
I have two problems with your view of "NFB".
First were is it written that in order to have "NFB" you must sum
voltages? I have seen analog "NFB" systems where the signals being summed
were represented by air pressure, so why not create "NFB" by summing
electric fields? In the triode the input and output voltages are
transduced to electric fields, and those electric fields are then combined
within the triode to create "NFB".
Second, what is wrong with doing the summing within the tube, why must the
summing be external? Taking your reasoning to the extreme, virtually no
audio amplifiers that exist today use "NFB", because the summing is done
internally to the amplifier. By your reasoning, for an amplifier to have
"NFB" the summing must be done in a circuit external to the amplifier
housing, for example by a rat's nest of resistors hanging off the input
and output terminals.
OK, can we just simplify things here?
If it's done by a triode, then it's not NFB and therefore, by divine
intervention, it sounds musical and alive. If it's done by a
transistor (boo! Hisss!) then it's by definition NFB, and makes music
harsh and unnatural. Does that sum up your position?
Basically, you just change the rules as you go along, so that triodes
come out ahead - regardless of reality.
--
Stewart Pinkerton | Music is Art - Audio is Engineering
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