Negative feedback Amp=more faithful reproduction?


Negative feedback (NFB) vs zero negative feedback (ZNFB). There seems to be unsubstantiated contention that ZNFB amps sound more realistic. I know this is an age old debate favoring the ZNFB design, but I think most audiophiles have never bothered to look into this matter and believe the advertisements and proponents of zero NFB design. I have been in that camp until recently. My own experience and research into articles on this matter leads to me believe NFB is needed for faithful reproduction of music. I'm not saying NFB design is more "musical", which is a highly subjective term and usually means more euphonic or colored. I've posted a similar question awhile back, but I was hoping we can have a more evidence based discussion on this matter. Perhaps, we need clarification of descriptive terms we use to describe sound. My contention is, in general, NFB designs produces a more accurate or faithful reproduction of music than ZNFB designs. Here is a very good article on feedback and distortion:

http://sound.westhost.com/articles/distortion+fb.htm
dracule1
Edwyun, Yes, we have to realize that when they talk about zero feedback they mean global feedback. Amplifier can have many local feedbacks and they might still call it ZNFB. Why? Because ZNFB became catch phrase and sells amplifiers.

You stated the you would buy amplifier with zero output impedance, infinite bandwidth zero distortions etc. but I'm not sure everybody would. Some people would complain that it doesn't have good bass with their speakers (zero output impedance), others would call sound analytical and sterile (lack of distortion and zero noise) while some would call it bright (infinite bandwidth) since their system has tendency for it. In addition many people like warm sound (enhanced even harmonics) and would not be happy with this amplifier.

Shallow global feedback, properly used, can reduce distortions, widen bandwidth and lower output impedance WITHOUT introducing Transient Intermodulation.

As for getting rid of the equipment, I think you're right. For the money some people constantly spend on audio they could hire Symphony Orchestra to play for them.
NFB is a subtractive process, although as proved by GE long ago, it increases the perceived odd order harmonic distortion. NFB removes some of the signal, and not in real time, either,due to propagation delay within the amp. Although I prefer to trust my ears, and could not care less about the theories involved, theory does match what I hear: with NFB it sounds less "alive". Deadened. Something essential has been deleted from the signal along with the improvement in distortion specs. There does sound like slightly less distortion, but the baby is thrown out with the bathwater. I personally think those who cite the "improved" specs from NFB are missing the point, but to each his own. Not so different from those who prefer SS over tubes, who often cite the "less distortion" specs. No, I don't enjoy listening to distortion, just unwilling to sacrifice aural immediacy to lower it.
"Mapman, the question here is if NFB makes reproduction MORE faithful. Some answered that there is no faithful reproduction, which doesn't answer this question, while others stated they prefer sound of ZNFB which doesn't answer this question either. The truth is, that there is no SS amp (and very few tube amps) with zero feedback. SS amp by nature is a voltage source, and as such needs some form of negative feedback, at least for the output stage. The question is how much and that might depend on the load, your preference etc. It is undisputed fact, that even small amount of NFB widens bandwidth, lowers output impedance and reduces THD/IMD distortions. Does it make reproduction more faithful on average? I think it might. What sound you like has nothing to do with original question."

Kijanki, you seem to be the only one who understand the intent of my original post. Thank you for putting into words better than I.

I find it amusing some found my OP to be an attack on their equipment and taste in music, which was not my intent at all. If some of you were offended, sorry.
Dracule1, What I'm getting from this is that some amount of imperfection can sound to many people more natural. Difference between natural, pleasing and faithful is fluid. Article was very interesting and thank you for posting it. I would only disagree with notion that deep feedback has no negative effects if amplifier is stable and input limited to slew rates equivalent to 20kHz. In ideal world it might be true but bandwidth never ends at perfectly 20kHz (TT often go to 50kHz) while high gain amplifiers, including op-amps have, (in spite of compensation) tendency to ring when presented with capacitive loads (speaker). It is big temptation for designer when he can improve everything 10-fold just by introducing more gain. I know that top designers like Nelson Pass or Jeff Rowland don't take shortcuts and that's why I bought Rowland class D amp. I know that modules were designed and made by B&O but Jeff Rowland name is enough for me to get interested. Some amplifiers are very expensive but you get what you pay for (Brand name). My amazing Hyperion HPS-938 speakers were a bargain but company doesn't exist anymore (so it seems). Now I worry what to do if something happens to these exotic drivers since nobody else makes them. Next time I'll pay more.
The reference to Class D amps is interesting. Generally, they use a form of negative feedback for pulse width modulation type of amplification.