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
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.

I'm working on this equation, you asked for, but it can take some time.
Dracule1:

You did read this in the article, right?

"Only by testing, working with the devices and taking careful measurements will you find out what really happens. Relying on maths formulae (regurgitated ad nauseam) or 'common wisdom' is not always the best way to get to the truth."

So what did the author use to test his theories?

"For the majority of the tests described, the effects were simulated rather than measured. There are some very good reasons for this, with the primary reason being that the simulator has access to 'ideal' amplifiers. These have infinite bandwidth, infinite input impedance, zero distortion and zero output impedance. Being perfect, they also contribute zero noise."

I know of no amplifier that has infinite bandwidth, infinite input impedance, zero distortion, zero output impedance, and contributes zero noise. If anyone has one, let me know, I would like to purchase it.

Also, you did read his qualifications, right?

"PROPERLY IMPLEMENTED, negative feedback will invariably reduce distortion to levels that are well below audibility. Not just harmonic distortion, but the much more intrusive intermodulation distortion. IF DONE INCORRECTLY the results can be awful."

I agree with this statement. But therein lies the rub. And you do realize that in the 70's NFB was used to get distortion below audibility. But most agree that, as implemented, it sounded pretty bad.
"What sound you like has nothing to do with original question. "

It does in that there is no concrete objective answer to the question possible.

It is a subjective question not an objective one to start with, so an objective/quantitative answer cannot be had.

Therefore one must practically rely on what they hear and prefer as data points towards obtaining a meaningful answer. All else is just a particular spin on the truth, and I do not mean that in a derogatory sense, only stating the facts.

Kijanki, I can think of nobody I would rather have solve that equation! Take your time! I can survive in the interim. :^)
KiJani:

I think you're talking about distinctions between local feedback and global feedback.
Mapman:
The answer to your question is to do away with reproduction altogether. Sell all your equipment and go to stadiums, concert halls, jazz clubs, auditoriums, amphitheaters, subways, bathrooms, etc. Go live!