This should say "majority of papers are written for usual DiyA greedy boy and melon head, not for vane JAES members court."
If you refuse to see the difference between the feedback loop and E/S/C degeneration then there is no common ground to continue this dialogue.
The old story repeats itself and no one gets wiser again...
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I never knew that the output of a feedback loop circuit is actually outside the loop. Very interesting.
Fair enough, but keep in mind that this was not written for
an academic audience. I recall stating that the examples
of cascaded stages, distortion figures, and complex tones
are exaggerated to make a point which I don't think is
generally appreciated, which is that IM distortion is larger
and more complex than is suggested by simple distortion
numbers and better accounts for some issues that
audiophiles actually have.
When I listen to a nice little SET amplifier with a fair
amount of 2nd harmonic it often sounds quite good with
simple material. The same amplifier tends to fall apart
with orchestral music. The same is true with full range
loudspeaker drivers, and the problem in both cases is
complex non-musical IM distortion.
You have used the word sad twice now. I don't
find this sad at all. I think it's interesting.
I never knew that the output of a feedback loop circuit is actually outside the loop. Very interesting.
The output of the feedback loop isn't outside the loop. The output of the circuit (the collector) is not part of the feedback. How could it be?
The feedback is in the gate-soure/emitter circuit. There's no 'loop' in the sense that you seem to imply.
jan didden
Of course I see the difference between degeneration and and a feedback loop. Why do you think I don't? Degeneration is a form of nfb, and there are many more, like Hawksford Error Correction.
Think about regeneration, used in RF to increase the gain in a stage. A clear form of positive feedback (which, as we know, increases gain and decreases linearity).
So there's a clear correspondence between degeneration and nfb versus regeneration and pfb.
Does that make sense?
jan didden
Can't someone come up with an analogy? Like the Horowitz and Hill 'Transistor Man'?
(I don't have the book to hand)
I could imagine a system where 'the controller' in one building is required to control a valve in response to instructions and maintain a pressure in a vessel in another building at some fixed ratio of the input value. It (he) could do this by looking at the pressure in the remote tank using a transducer and gauge fed back with a wire, and turning a knob in response to the error. This would unambiguously be seen as a feedback loop, I think, with all its attendant problems of lags, distortion, instability etc.
It (he) could also respond to the pressure in the pipe leading to the tank i.e. a local transducer and gauge. This would not be such an obvious feedback loop, but would clearly still be feedback, with its own set of problems, distortion and instability. To the outside, world, however, it might be seen by some credulous people as a miraculous system which maintained a 'gain' without the need for feedback. But it would still be feedback.
Something like that?
(I don't have the book to hand)
I could imagine a system where 'the controller' in one building is required to control a valve in response to instructions and maintain a pressure in a vessel in another building at some fixed ratio of the input value. It (he) could do this by looking at the pressure in the remote tank using a transducer and gauge fed back with a wire, and turning a knob in response to the error. This would unambiguously be seen as a feedback loop, I think, with all its attendant problems of lags, distortion, instability etc.
It (he) could also respond to the pressure in the pipe leading to the tank i.e. a local transducer and gauge. This would not be such an obvious feedback loop, but would clearly still be feedback, with its own set of problems, distortion and instability. To the outside, world, however, it might be seen by some credulous people as a miraculous system which maintained a 'gain' without the need for feedback. But it would still be feedback.
Something like that?
... You have used the word sad twice now. I don't
find this sad at all. I think it's interesting.
We do have some incredible people here. Those people have no problems offending others, but aren’t able to read properly. If you read my posts with care, you will see that I do not deny a feedback action, which however I call inherent feedback. It is the action of a forward biased transistor maintaining the equilibrium.
Isn’t it split hairs to talk about whether we call it feedback or not, the question is what it does, especially in audio. Here I see big differences; those of you wanting to use classical feedback should do so. Why not? You can’t build an Aleph amplifier without using a standard feedback loop. Is it an awful amplifier though? No it isn’t, it is brilliant. Mr. Pass is wise enough not take a fixed position here as he is the only man in the audio industry which is able to promote and sell different approaches at a time. No other company gets away with this. Chapeau!
It has its reasons, why I do not post here regularly, it is nearly a waste of time and the entertainment one gets from some other posts is very limited.
Hi Ila
I wasn't referring to you, or anyone else in particular, with my attempt at an analogy, merely trying to break the log jam and summarise this discussion in an easily-accessible way. I hoped someone might take my half-baked idea and mould it into something meaningful even I could understand.
No offence intended!
I wasn't referring to you, or anyone else in particular, with my attempt at an analogy, merely trying to break the log jam and summarise this discussion in an easily-accessible way. I hoped someone might take my half-baked idea and mould it into something meaningful even I could understand.
No offence intended!
Somehow I got an impression that you consider them the same thing. If it's not the case, we have common ground for discussion.
The word and the meaning is the problem - feeding something back. I can't put it all in the same context. A child feeding on its mother's breast and a buzzard devouring a cadaver - both are form of nourishment and should be called the same name?
In causal universe such correspondences are easy to set but I think we don't need apricots to define difference between oranges and apples...
Isolated facts can be made to make sense under variety of circumstancies, but I can't force myself to use the same word for nfb loop and E/S/C degeneration.
The effect of emitter current on the emitter resistor is feeding back to the input signal destructively for its voltage amplitude. As a mechanism it is definately an AGC loop. By reflection, not by injection. That is the difference in technique from an external injection loop, and it ups output impedance in contrast.
Because e/s/c/ degeneration is not the same as a feedback loop. I thought we agreed on that already?
But a degenerative circuit and a feedback loop both are a form of feedback. That seems obvious if you look at the effects of both.
jan didden
That's what you just did - both are a form of nourishment.
What's the problem? I really would like to know, I'm not trolling.
A feedback loop causes a part of Vout to be used to modify Vin (to subtract if it is nfb).
Emitter degeneration causes part of Vout (Ve) to modify Vin (Vbe).
So, acknowledging that degeneration is not the same as a feedback loop, nevertheless both are a form of nfb - one using a loop, the other using local feedback via Re.
jan didden
Part of the problem is that many people are desirous of
being able to use the term "no feedback"
in association with their amplifier for marketing or
bragging rights.
Taking the position that "there's no such thing as no
feedback" doesn't move us forward in the real world,
so a compromise position seems to have arisen in which
no feedback is an allowed claim for amplifiers which
have degeneration only, and local feedback describes
circuits where a loop exists only around a single gain
element.
I could be wrong, but it appears that this is the consensus
among myself, Curl, Cordell, Hansen and others.
Anyone is free to chime in here....