What is wrong with negative feedback?

"There are no known speakers requiring a damping factor of over 20"

I am not aware of any speakers that publish damping requirement specs. What are some?

I am aware that different designs benefit differently from varios damping factors, but not that vendors specify damping requirements for their speakers in that determining which combos sound good is often a largely subjective determination?

Thanks Ralph good information.

Ralph, this is the wrong place to ask, but would you care to answer the math as proposed by:

http://www.transcendentsound.com/amplifier_output_impedance.htm

Just trying to get a grasp on the "how". The other controversial article is not related to this thread.

Fascinating relating electronics to chaos theory. Maybe we can use it to predict long term digital format forecasts.

The math is fine right up the 2nd to last paragraph where an assumption is made that is incorrect. It matters a lot what the output section topology is. An excellent example is the difference between a triode gain stage and a cathode follower using the same triode. The CF will be found to have a lower output impedance, according to Rp/1+mu where Rp is the plate resistance and mu is the 'voltage gain' of the tube.

So if we take the example given we get 17.5/3 = 5.767 (the mu of a 6AS7G is 2), which is for a simple CF circuit. For a Circlotron, which is a CF variant, the formula is similar, the 1 is replaced by a 2 as above so we get 17.5/4 = 4.375

In these cases it is assumed there is no feedback.