"John Byrns" wrote

The input voltage at the grid, and the output voltage (feedback)
at the
anode each create and electric field within the tube, the
summation of the
two opposing electric fields within the tube determines the anode
current,
it is a simple negative feedback system.

John,

How can I make it more clear?

You can call it feedback if you want. For it to be feedback in the
usual sense of the word applied to a control system, which is what
an amplifier is, there must be

**summation of input and feedback signals**

Other summations don't qualify.

Interaction of anode and grid gives rise to the miller effect, we
have dealt with that.

I estimate that Andre's 300B KISS amplifier has about 14 dB of
negative
feedback resulting from this effect.

Haven't seen it. Seems a wild claim to me. The thing is, as I have
said a few times now, the meaning of feedback is a matter of
definition. It seems a wild claim because it would not normally be
claimed. Hence it falls outside the normal definition. QED.

Neither is your definition useful. The response of a triode can be
expressed as a time-invariant function. The effects of
interelectrode capacitance and electrode inductance depend on the
circuit, but in normal triode connection with a grounded cathode
only the Miller capacitance is a path from output to input, and only
becomes feedback in the context of the particular circuit attached
to the grid.

Put a constant voltage across a perfect resistor and the current
will rise to produce a voltage equal to the input voltage. You could
contrive to say that it is a feedback control system because the
resulting current arises from a comparison of input and output
voltage. It would not be a new discovery, and you will find a
perfect resistor as an example in the introductory chapters of most
student texts on feedback control systems. You would not add
anything useful to anyone's understanding of resistors. There would
simply be no point. Ohms law is all we need. The books use the
resistor as an example of how *everything* can be considered a
feedback control system. The rest of the book will restrict itself
to examples where it is useful to do so. After all, if everything
truly is a feedback control system, the name becomes meaningless for
the purpose of identification, and so there can be none. At night,
all cows are black.

The available descriptions of valve behaviour...all the published
curves and stuff, don't require transformation. You don't need to
add any stuff about fields inside...you just need the curves.

Is a capacitor a feedback control system? Or a choke? Why not? And
if all these components are feedback control systems, perhaps you
better add a few more dB to your estimate.

cheers, Ian