Damping Factor and Overall Negative Feedback.

That results in what is called transient intermodulation distortion (TIM), and enhancement of particularly objectionable odd-order distortion components.

It is this last bit wherein you see so much variance in amplifier design: odd orders as stated are very objectionable, in no small part because the human ear/brain system uses them to determine how loud a sound is. It is arguable that our ears are more sensitive to this than actual frequency response errors- so electronics that distort these harmonics will have a false loudness and brightness to them. Audiophiles use terms like 'hard', 'harsh', 'brittle', 'bright' to describe this phenomena.

This is why of two amps that have flat frequency response, one might sound bright and the other might not.

@almarg  Hi, I understand this post is from over 10 years ago, but could you please elaborate further on why, in areas where feedback could be beneficial, a good design calls for minimum or no feedback? It seems like it should be the other way around until the feedback reaches a balanced level, avoiding excess or deficiency, right?

A good design will require minimal or no feedback to provide good performance in the areas that feedback can help, and thereby avoid the downsides of excessive feedback.

Unfortunately, our beloved Al (almarg) is no longer with us. If you search the archives, you might find some of his insights that may help. Al is sorely missed, that's for sure. He was one of our very finest.

@waltersalas so very well said ! Miss him and this is a good reminder to savor his memory and contributions which were many.

to the recent responder, i’m not a big fan of negative feedback as Al eloquently stated because of the temporal distortions. There are designers who favor and those who disfavor the use of it. Volumes written, endless debate, cults created, etc…..

I will say this as a long time Music reference RM-9 amplifier owner and listener, it is an easy amp to evaluate the sonic temporal impact of 3 different levels of negative FB with, just be sure to level match. Draw your own conclusions.

@waltersalas @tomic601 

I'm deeply sorry to hear that, but his words of wisdom will remain with us. I will trace the archives for that. I wish that every amplifier will come with a switch for adjusting feedback levels.  Thank you for sharing that.