[G Georgopoulos]

Let's discuss the pros and cons of feedback and no feedback.

Please stick to solid state only!

cheers

[Speedskater]

No such thing as 'no feedback' !
Maybe 'no global feedback'. But that's just a lack of engineering skill.

From Linear Audio magazine:
 The F-Word - or, why there is no such thing as too much feedback

In Linear Audio Volume 1, Bruno Putzeys wrote  The F-word - or, why there is no such thing as too much feedback. He addresses many issues related to the use of feedback in audio, as well as several misconceptions. The section on 'slow' and 'fast' amplifiers will be an eyeopener for many. He also traces historical events that puts us in the situation we are now. A critical attitude towards negative feedback is certainly healthy, and Bruno gives us the information to base our opinion on.

http://www.linearaudio.net/index.php?option=com_content&view=category&layout=blog&id=39&Itemid=64

[G Georgopoulos]

No such thing as 'no feedback' !
Maybe 'no global feedback'. But that's just a lack of engineering skill.

You are correct!!,local feedback keeps the transistors stable from running into thermal runway.
Thanks for your nice link..

[Elizabeth]

Well the 'dislike' of feedback comes for the Japanese overuse of it to lower the distortion specs back in the 1970's. They went way overboard in the distortion wars.. And the backlash is STILL with us in our 'badvibes' towards to whole notion of negative feedback.
So a good portion of what most audiophiles think is STILL ruled by the distaste from the 1970's feedback overkill.
My own opinion is the use of feedback is at the discretion of the designer. If that person can make a great sounding product why would I care HOW he/she does it? So IMO I do not care at all about the theory of "feedback". that is the designers issue. not mine. I do not check what percentage of negative feedback they used.. I just listen to the product for it's music presentation.

[Freo-1]

No such thing as 'no feedback' !
Maybe 'no global feedback'. But that's just a lack of engineering skill.

From Linear Audio magazine:
 The F-Word - or, why there is no such thing as too much feedback

In Linear Audio Volume 1, Bruno Putzeys wrote  The F-word - or, why there is no such thing as too much feedback. He addresses many issues related to the use of feedback in audio, as well as several misconceptions. The section on 'slow' and 'fast' amplifiers will be an eyeopener for many. He also traces historical events that puts us in the situation we are now. A critical attitude towards negative feedback is certainly healthy, and Bruno gives us the information to base our opinion on.

http://www.linearaudio.net/index.php?option=com_content&view=category&layout=blog&id=39&Itemid=64

Bruno HAS to use a ton of feedback to get the class D amps not to sound nasty, and sound smooth.  My recent discovery of ATC speakers with the super linear drivers has opened up a whole new world as to the relationship between the amp and the speaker.  The speaker design can have a lot more effect on sound quality than the amp used, given good engineering principles. 
 
Having said that, here is a white paper by Papa Pass on feedback:
 
https://passlabs.com/articles/audio-distortion-and-feedback
 
There are several First Watt amps that employ NO feedback.
 
http://www.firstwatt.com/prod.html

[Davey]

Semantics I guess, but I don't think it's correct to say those First Watt amplifiers have no feedback.  They don't employ any 'global' feedback.

Even the simplest amplifier stage imaginable.....an emitter follower.....employs negative feedback.  You might not notice it immediately when looking at a schematic, but it's there. 

Cheers,

Dave.

[G Georgopoulos]

My Thanks to all you guys for posting,let's leave local feedback aside,let's concentrate on global feedback,what are the benefits of it???,the links you posted say alot about global feedback,but I want to hear from you anything the links omit...

Thanks

[Pete Schumacher]

My Thanks to all you guys for posting,let's leave local feedback aside,let's concentrate on global feedback,what are the benefits of it???,the links you posted say alot about global feedback,but I want to hear from you anything the links omit...

Thanks

Global feedback linearizes the transfer function of the amp.  Global feedback also reduces the output impedance, which makes the amplifier less susceptible to load variations. 

[G Georgopoulos]

The way I see global feedback is it regulates the gain of the amplifier much like a voltage regulator regulates the voltage of a power supply (it keeps it constant),this is very important when it comes to sound fidelity across the audio spectrum,the other thing it does is regulates the character (faithfulness) of the ac signal,this of course means that it reduces distortion,but distortion is another thing (harmonics) the character is the same as the input signal,this of course is best achieved with more feedback because it compares more with the input signal...

[Speedskater]

Today on a technical forum, Jan Didden posted:

Quote
Which, to paraphrase, says: adding feedback loops around non-linearities creates "new sounds" and "program modulated, high frequency "noise""

This was indeed often the case in that era, as the amplifiers were very nonlinear to begin with and had relatively low open loop gain, which made the available amount of feedback rather low.

I believe that people like Bruno Putzeys and Bob Codell have shown that with contemporary amplifiers this is no longer the case, and that 'there is no such thing as too much feedback' (withing the stability regime of course). Although there IS such a thing as too little feedback, leading indeed to 'new sounds'.

jan

[Davey]

Unfortunately, this is one of those topics where beliefs/understandings are so entrenched you won't get anywhere with the discussion. 
Even the thread title is missing the point and seems to assume there is a black and white answer to the question.  Different designs/topologies might work better with global feedback and some may not.

Cheers,

Dave.

[AJinFLA]

Really comes down to whether you view the role of an "amplifier" as a voltage (or current) multiplier, or a special effects box (with "magical" qualities).

cheers,

AJ