Why do audiophiles shun feedback in amplifiers?


I've owned several very highly regarded tube amps. Some of them allowed adjustment of the amount of negative feedback. I've always found some degree of feedback improved the sound...more realistic with tighter bass, dynamics, better defined imaging, etc. I have found amps with less or no feedback sound loose and diffuse with less dynamics... I know you should design am amp with excellent open loop gain before applying feedback. I can see the use of no negative feedback for low level amplification (eg, preamp and gain stage of CDP or DAC). So why this myth perpetuated by audiophiles and even many manufacturers?
dracule1
Can an amplifier with no or minimal negative feedback in play make a CD recording that might be irritating otherwise normally not irritating?

Mapman, you basically asking if it is possible to make amplifier bad other way than NFB. I'm sure it can be done 100 ways from bad power supply to wrong bias current.

NFB is producing TIM only when overused. We're talking global NFB since local ones are almost always there. Transistor amplifier output stage represent voltage source. For that it needs to be regulated = NFB.
Mapman,
In my experience the answer to your question is no. The one quality I`ve come to admire over time with my SET is honesty. What ever is the inherent sound character of the CD that`s what I`ll hear,flaws and all. Some SET amps could perhaps'pretty up' the sound but my does`nt do that. I have some recordings that are thin,brighter and in some cases edgy and that`s how they will sound.But those that are recorded well,oh my goodness.

My SET has less editorializing than all of my previous amplifiers. I reconized this aspect early on, It just seems to preserve the signal with minimal influence.The effect is heard as pure and unfiltered.
Regards,
Charles,

I'd say pretty much the same thing with the ClassD Icepower BelCanto ref1000m amps in my system, used with any of my speakers, especially the OHMs and Dynaudios.

My small Triangle Titus XS monitors, which are more efficient and known to be more tube amp friendly, are the ones where I think I could improve the sound with another better matched amp. I do not think use of negative feedback or not alone would be the main factor to determine which amps would work best with those, though I am sure some that do not use extensive NF would sound very good indeed.

I have a pair of Tube Audio Design Hibachi monoblock amps that do a very competent job with the OHMs and Dynaudios (though I prefer the Bel Cantos with those overall), but are probably a better match to the Triangles on paper.
Mapman,
I`d agree with your thoughts about appropriate amp for your Triangle monitors.My path was simplified by matching amp and speaker by the same builder. His objective was cbviously very good compatibility.
Regards,
The amp/speaker match is why I dropped this link earlier:

http://www.atma-sphere.com/Resources/Paradigms_in_Amplifier_Design.php

Mapman, if you have speakers that your class D amps are really happy with, there is the chance that those speakers may not be compatible with tubes.

Dracule1, 'tightness' in the bass is not a function of real music but is a function of an over-damped speaker. IOW its an audio system artifact.

Kijanki, I usually do not include degenerative feedback when I make my comments about the negative effects of loop feedback. This is because degenerative feedback occurs simultaneously with the signal i.e. there are no propagation delay issues.

I think it should be pointed out that the use of negative feedback to reduce IM distortion is a bad move. We get very low IM figures without using feedback- IM has a lot to do with power supply design, grounding and parts quality. I am of the opinion that is much better to design the amp to have low IM operating open loop, since IM will occur at the feedback nodes of the amplifier, resulting in a harmonic noise floor (rather than a natural hiss noise floor caused by component noise). The human ear can hear about 20 db into a natural hiss noise floor, but if there is a harmonic noise floor caused by IM (with harmonics and in-harmonc distortions extending to the 81st!), the ear will not hear below that point at all due to the way the masking principle works.

This is one way to get more detail out of an amplifier, since a harmonic noise floor will block the ear's ability to hear detail below that point.