The source degeneration and drain load resistor are indeed identical mechanisms, and both occur in "real time", it must because the same current flows through both resistors! (see Kirchoff's laws) Yes, they do behave differently, but this is simply because the output impedance is higher from the drain than from the source. In both cases, the bandwidth available for the negative feedback is defined by the gate capacitance of the mosfet, but when it's driven by the higher impedance of the drain, the rolloff of course starts sooner (higher impedance driving the same capacitance).
There are a couple of problems I see with this. First, we have a capacitance involved, so there is a time issue associated with the related phase issues of that capacitance. If we have a series of these circuits together, we will be able to measure a delay time to it. So- where does it come from? It probably the circuit itself, ergo it has a delay time too.
And as far as I'm concerned, if one condemns the use of negative feedback, and hasn't gone through the process of figuring out where the poles and zeros in the response fall, and analyzing the phase margin . . . they simply haven't a leg to stand on.
And if one *did* go through that exercise, and still finds the feedback to be detrimental, what then?
I think I have, several times. They are the result of circuits that have the following:
-Nonlinear open-loop transfer functions that cause both low- and high-order distortion
-Topologies (i.e. differential, push-pull) that are more effective at cancelling even-order distortion products than odd-order
-Feedback (and hence closed-loop linearity) that decreases as frequency increases.
Put the three together, and you have a system that enhances higher-order, and odd-order distortion products. But the root cause is NOT the feedback.
This **sounds** like an argument for adding feedback to an SET, although I suspect that its not. But an SET can lack the issues above, yet still be degraded by the use of feedback. I myself use fully differential circuits and have to jump through a lot of hoops to prevent odd-ordered generation (we wind up with the 3rd but none of the higher orders) but otherwise our amps don't have the issues you present above either. Yet when feedback is added, increased odd ordered harmonic distortion can be measured (although its tricky as the increase is very slight; OTOH it does not take much as the human ear uses odd orders to gauge volume so tiny amounts are instantly audible).
Frankly, this last quote seems to indicate that feedback should not be used as the circuits that have these issues would seem like something to be avoided.
Of course a complete audio system has a Chaotic behavior. But amplifiers do too. If you look at the formula for feedback, its nearly identical to the feedback formula for classic chaotic models. IOW, we have a strange attractor that models the amplifier's behavior under feedback, we have the other conditions of classic chaotic systems: if it walks like a duck, quacks like a duck... BTW, 'dense orbit' refers to the strange attractor. If you look at a simple pendulum, it is a classic example of a chaotic system and we have been using them for mechanical timing mechanisms for several hundred years. It is often the utter simplicity of chaotic systems that is what throws people off- why they initially don't want to look at things as being Chaotic. BTW its important to understand that the term 'Chaotic' is not the same as the typical dictionary meaning.