Why do audiophiles shun feedback in amplifiers?

You might say that the use of global negative feedback causes the amplifier to violate one of the fundamental rules of human hearing/perception: how we determine how loud a sound is. We do that through analyzing the odd ordered harmonics rather than processing fundamental tones.

So if the amplifier has trace amounts of the 5th, 7th and 9th harmonics added, it will not only sound louder than real music of the same volume, but bright/less relaxed as well.

This is one reason why two amps can measure perfectly flat with the same bandwidth on the bench, but one will sound bright and the other won't.

As Kijanki pointed out, global feedback reduces 'output impedance' (I put the term in quotes because it is a definition that is only used that way in audio!). So amps without feedback will have a higher output impedance. If coupled with a speaker that demands a lower output impedance of the amp, tonal aberrations may result.

So you can see that a more ideal combination might be such an amplifier with speakers designed to work with higher output impedances. Then you get proper tonality coupled with no violation of human hearing rules.

For more information see: http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php

Well there's a couple years of intense study in electronics engineering in a nutshell! I'm looking forward to a lot more analyses geared toward practical utility. Am I asking too much? Lets keep this ball rollin guys. Nice change. Is that a lyric?

Dracule1,
I don`t agree with the myth description.It just depends on the amplifier`s chosen output devices and the particular speaker being driven.What good is it to reduce 2nd order harmonics to extreme levels and then replace it with odd high order harmonic distortion(worse),that`s a bad trade off.A tiny amount of this NFB odd order distortion is not natural to human hearing and is processed as irritating and artificial.

Some speakers do require amplifiers with NFB. I`d prefer speakers designed that don`t 'need' these types of amplifiers in the first place.Amps without NFB sound more natural and realistic in my own experience, YMMV.
Regards,

It is not only 2nd harmonic, but also Intermodulation Distortion, Bandwidth, Output Impedance - practically everything. The key to avoid TIM is to limit bandwidth at the input to one that amp had before feedback (that extended bandwidth) was applied. This will be OK if amplifier had wide bandwidth to start with, otherwise reduced bandwidth will cause phase shift at higher frequencies and wrong summing of harmonics. Also, as I mentioned before, every amplifier has some form of NFB.

I don`t agree that 'every' amplifier has NFB. There are some DHT SET amplifiers that lack NFB in their circuit.Some of these types of tubes are linear enough so that it is`nt necessary.My amp is one example(unless Israel Blume told me a fib,and I doubt that).
Regards,