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RE: So are you an absolutist?

I am pretty much an absolutist...none of my gear has negative feedback other than degenerative feedback (like a cathode follower would use...even then I am not sure I have any cathode follower circuits in my gear...maybe my phonostage...)

The problem with only using a little bit of feedback is that you still have relatively high distortion but you have created a whole bunch of high order distortion, which remains unmasked and is likely audible.

Empirically though I have found that amps with a little bit of feedback often still sound more dynamic and less "gray" tonally than those that use massive amounts.

As Geddes and others point out, you can tolerate a fairly high amount of low order (meaning primarily 2nd and 3rd order...although Cheever allows for more at higher SPL because of the ears own distortion generation acting as a mask) due to masking. In fact, if the harmonics are effectively masked, it sounds to the listener as if there is NO distortion at all.

Cheever posits that as long as the distortion components are falling below the ears own distortion pattern and intensity that the component will sound pure and undistorted...even if it has measurably high distortion compared to other components that don't sound as pure. The pattern has to match (and at a given SPL) or remain below the ears own harmonic distortion generation.

As the ear makes essentially nothing above 9th harmonic...even at very high SPL (at normal listening levels it makes nothing really above 5th harmonic), ANY distortion harmonics higher than that will be audible even at exceedingly low levels.

As to why high feedback amps can sound "dead", "gray" and lacking in perceived dyanmics, especially on high sensitivity speakers where all is revealed, I think it has a lot to do with the "noise" floor. Crowhurst demonstrated in the 1960s that high feedback makes a lot of distortion produts...essentially an infinite number with a complex music signal. These are mostly at every low levels and essentially generates a signal correlated "noise" floor. True noise is not correlated with the music signal and as such it is possible to hear below that noise floor which helps with space, dynamics and low level detail. A correlated noise floor acts as a wall that one cannot hear below and as its modulating with level, it probably has very detrimental effects on the perception of the music. This might be why a minimal amount of feedback is not so bad as it would not create a very strong effect on this signal correlated noise floor.

High feedback also means that a lot of the back EMF from the speaker will find it's way back into the signal path, as some of it is injected back to the input stage (for amps with global feedback). That signal of course looks nothing like what went into the speaker and besides it is signal that doesn't align with what is currently passing through the amp.

Finally, Nelson Pass also weighed in on feedback (although his conclusion was a bit wishy washy). You can read that here:

https://www.passlabs.com/technical_article/audio-distortion-and-feedback/

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