Class ABCD ?

[theaudiohobby]

Triodes have degeneration, not feedback. They ain;t the same --- sorry but you have no clue.

Ho Hum ...from the same thread

theaudiohobby presented me with this 1953 article and says that sets all have feedback and there is no such thing as a no-feedback amp

There is I believe indeed no..no feedback amp..that is no news..but there is such a thing a local feedback and global loop feedback

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I offer no real rebuttal other than to say that those that understand tube circuits consider this info old, self-evident news. If someone wishes to model a triode as a pentode with "built-in" feedback that is their business and it may work for their needs within that model's limitations. Many such models are used. Some may model a pair of triodes in cascode as a pentode for example.

The triode has certain inherent features. Among them is that if the anode voltage is lowered the anode current lowers, because there is less tension between cathode and anode and thus less electrons are attracted by the anode from the cathode.

Now we may call this a feedback mechanism or not.

Now for the clincher..

The method is of particular interest for control circuits and output stages utilizing low-µ triodes, since the back action from the anode on the emission-controlling field at the cathode is then appreciable. Fundamentally, this electric field action is a form of negative feedback

correlated to the transistor behaviour

Simple transistor amplifiers use emitter degeneration to achieve negative feedback, which gives a relatively predictable gain compared to the gain of the transistor itself, which varies widely.

Degeneration is fundamentally used to achieve negative feedback in analog circuits, it is as simple as that. If it looks like a duck and quacks like a duck, it is a duck. Another popped bubble.

PS: You might as well give up now....Neither your english degree nor PQ marketing blurbs have equipped you for a technical discussion. Maybe I should post your blunders for the world to see that you do not know how to read FR graphs. Worse than that, you proceeded to do some character assasination in your referenced SET thread, shame on you .