Amplifier Feedback Good or Bad?

[mtrycrafts]

Never hread of this dude, thanks for posting this up going Research him right now. I’m old school out side of Dr. Harman and Dr. Tool the two that I idolize
well 3, Gene comes in a close 3rd he may move up to #2,only because Dr. Harmon passed away.

You can still idolize him. And your list can be more than 3. Just look at Albert E.

 

[mtrycrafts]

Me neither, I am not an audio electronic engineer, though I am sure if there is such a degree option. My final year options for my EE degree was in Control and power system. "Control systems" means the syllabus would include feeback, feed forward theories, and lots of Laplace, Z, Fourier transforms, infinite series kind of math. Just because someone is an EE, doesn't mean one has in depth knowledge in audio electronics, though one usually would have/or should have the basic knowledge.

I thought you were into microwave stuff. My youngest son is.

 

[Gmoney]

You can still idolize him. And your list can be more than 3. Just look at Albert E.

Thanks man!! I didn’t know there where more than 3 of them in the whole wide world. . But umm who’s Albert E by the way? ain’t he the one who said E=2 +Z? and found out them black holes in space ain’t nothing more then a blact spot on his Telescope lens and when he wiped off his scope the black hole in space was going.

 

[Pogre]

Never hread of this dude, thanks for posting this up going Research him right now. I’m old school out side of Dr. Harman and Dr. Tool the two that I idolize
well 3, Gene comes in a close 3rd he may move up to #2,only because Dr. Harmon passed away.

I dunno if you saw, but post #12 in this thread was a reply from Bruno.

Fun topic for sure tho. A whole 'nother area of audiophilia I wasn't aware of. Always learning new stuff here.

 

[AcuDefTechGuy]

Amp Negative Feedback Pros from Wiki:
1. Reduces total distortion if sufficiently applied (increases linearity).
2. Increases the bandwidth.

Just like EVERYTHING, as long as the DESIGN is good, it’s all good.

 

[Gmoney]

Amp Negative Feedback Pros from Wiki:
1. Reduces total distortion if sufficiently applied (increases linearity).
2. Increases the bandwidth.

Just like EVERYTHING, as long as the DESIGN is good, it’s all good.

So less is more right? and if that is so, it can be bad rigth? But if negative feedback is so bad why make us pay good money in the first place? Don’t we pay enough for bad specs on our gear in the first place!
Man now my head is hurting from all this Negative feedback. than you went and found the one Expert wiki links who has Knowledge straight from God!

 

[AcuDefTechGuy]

So less is more right? and if that is so, it can be bad rigth? But if negative feedback is so bad why make us pay good money in the first place? Don’t we pay enough for bad specs on our gear in the first place!
Man now my head is hurting from all this Negative feedback. than you went and found the one Expert wiki links who has Knowledge straight from God!

I think “amp neg feedback” is something only amp designers care about. The rest of us just want the final product - great sound and reliability.

 

[Gmoney]

I think “amp neg feedback” is something only amp designers care about. The rest of us just want the final product - great sound and reliability.

Dam you throwing in the Towel already? lol Very true Andrew, man I’m just happy if my AVR last more than 3 years. because if it doesn’t? Bad audio Engineer!

 

[Gmoney]

What a fascinating topic. I chose option 3 for the poll.

Pogre, That’s the Safest pick, maybe I need to change my pick. Cause if I am right than all you old timers gonna think I’ m a know it all. Oh wait everyone already does. lolo

 

[PENG]

I thought you were into microwave stuff. My youngest son is.

I might have mentioned "communication", i.e. telecommunication. No, I only took a course that helped me prepare and pass one of several examinations required for registration as an engineer in Ontario. That was a tough one as it was years after graduation, so all those Fourier transforms etc., had been forgotten. Interesting, that's when I actually understood the applications of Fourier and managed to get an "A" in that one exam. And of course realized the man was a genius who I think is the main reason why we have today's wireless technologies.

 

[PENG]

Please, tell us, don't be shy.

He's one of those amp designers who emphasized the downside of using "too much" negative feedback. He is a highly regarded amp designer and I wish I can afford one of those Passlab amps. I think you are I have been at this long enough to know that the negative feedback thing, even if not too too much, have been cited by many hearsay followers/believers as one of the reason why non audiophile class amps that have low distortions don't sound as good as audiophile and/or the so called high end amps. The problem with those hearsay followers is that they are prone to take things out of contexts. Negative feedback, TIM, the higher order odd harmonics, are the things often cited as reasons why "well designed amps" sound different, I mean audible differences that are easy to tell... Damping factor was a popular one actually (probably due to Crown Audio's talks being taken out of context) but seems to have died down in recent years.

 

[ryanosaur]

I was getting ready to reach out for help on the consideration of building some NCore or Purifi Monos...

This entire situation springs up like some serious coincidental psychic phenomena!

Does anybody else want to play?

I'm not an EE by any stretch... I just know if you stick your finger in the socket, it tingles! (OK, I AM smarter than that... but not necessarily by much. )

I see Apollon and Nord products being sold... and other companies designing "accessories"...

How can a lay person best learn about putting together some well performing Monos? I've been looking and could use some pointers, please.
Do I need Buffers?
OP Amps?
Is the Simple Amp and SMPS enough?
What does it do to a Raal vs a Dome? (I've heard that maybe Raals don't sound so good on non-buffered Class D... Is that a myth?)

Mind, I'm deep into learning speaker design and am working on my first model in SoundEasy. I know I've a long way to go, but my hope is to use these mainly for testing and driving a new rig. I want the amps to be solid equipment, and would love to dive in to Class D after reading the reviews recently of the ATI (AH) and Hypex/Purifi (ASR).

Please... any thoughts and suggestions would be welcome. I will start a new thread to further this, too... but as I said: this thread and my interests are interacting almost as if by magical choreography!

I gladly invite any PM Advice, unless of course this tangent-discussion will benefit this thread! @gene @PENG @Bruno P. @M Code ??? Anybody???

My humble thanks in advance.

Best,
R

 

[mtrycrafts]

Thanks man!! I didn’t know there where more than 3 of them in the whole wide world. . But umm who’s Albert E by the way? ain’t he the one who said E=2 +Z? and found out them black holes in space ain’t nothing more the a blact spot on his Telescope lens and when he wiped off his scope the black hole in space was going.

Yes, yes, that is he.

 

[AcuDefTechGuy]

Dam you throwing in the Towel already? lol Very true Andrew, man I’m just happy if my AVR last more than 3 years. because if it doesn’t? Bad audio Engineer!

3 years? Heck, my Denon AVP-A1HDCI lasted 8 years!

 

[Gmoney]

All I know is I sure wish old Bob Carver still made his TFM amps. Nothing sounded better than his amps!
who needs negative feed back amps when you can or could’ve since there no longer being made, Magnetic field amps. Sure do miss my TFM-25.

 

[Gmoney]

3 years? Heck, my Denon AVP-A1HDCI lasted 8 years!

Andrew 8 years is really good bro most Marriages don’t last that long anymore.

 

[Bruno P.]

Are there any audio AVRs available today that utilize your feedback design approach using Class A-B amplifiers?

I've been a bit too busy doing class D to spend a lot of time looking over the fence, but I suspect not. After all, the classic "nested loop" approach has a lot going for it in terms of simplicity. Theoretically it's more susceptible to TIM but that's easily enough fixed with a pair of resistors in the input stage.
Having said that I've got this itchy feeling in the back of my head that somewhere in the 90's I've seen a patent drawing for a class AB amp with saturated integrators in it. At that time I had no idea what it was about so I gave it no heed (an attitude that explains a lot about the world). It was done by someone from Austria I think? Never found it again.

I should add that Bob Cordell is the only amplifier designer I know

If you only have the opportunity to know one amplifier designer, Bob is definitely a good choice.

He published an article in Audio magazine in February 1980 at the height of the controversy surrounding Transient Intermodulation (TIM) Distortion and its relationship with negative feedback.

That article ought to be a classic, but it was probably too detailed for most. For the upcoming long post I've tried to boil it down to its barest essentials. Funnily enough it turns out that feedback doesn't even figure in the TIM distortion mechanism.

Shouldn't one also be astute or learned in the field of psychoacoustics? How would you know one way or the other absent listening test?

It's rather essential indeed. Otherwise, how would a designer decide what specs are important at the start of the process... Think of those whose amps can do MHz'es but with no particular care for the bit up to 20kHz or so.

I think “amp neg feedback” is something only amp designers care about. The rest of us just want the final product - great sound and reliability.

Amen to that sir. The problem is that somehow a lot of audiophiles seem unable to decide whether they like the sound of a box without having first verified that what goes on inside the box fits their ideology.

 

[Gmoney]

I dunno if you saw, but post #12 in this thread was a reply from Bruno.

Fun topic for sure tho. A whole 'nother area of audiophilia I wasn't aware of. Always learning new stuff here.

Pogre, everyday that II come in here on AH I learn something. Could be a tip from one who just signed up on AH or from one of the old timers who talking about something as simple as speaker placement of a center channel speaker. Case in point I cleaned up my TV rack when I moved last month well, watching a movie one night and I kept having to up the dialogue thinking which at my age is getting harder cause I seem to forget more of mandane things. Noticed the center speaker was setting in the middle of the rack shelf got up pulled it to about 1 1/2” out passed the shelf and Walla much improved dialogue. I had jacked up the level to +2 not much but moving that center speaker out just 1 inch or so passed the shelf made a world of difference. Dialogue was to much better now so put the level back to 0. Setting here right now just finished my first cup of coffee looking over my setup speaker placements, how far, how close from my walls or is my sub, could be placed for a better low end. Those are the things us Audioholics are always thinking of. It’s why I hang out in here with you guys knowing somewhere on some post or Thread I’ll learn something. That little tip of moving the center channel out some from the shelf I picked up that simple little tip from reading one of Your post Pogre! Me being Me with being thickheaded
likes to have Everything even and symmetrical when comes to setting up everything on my rack and speakers, well as you know surround doesn’t like that most of the time. Sometime you gotta movie a speaker cause it can’t be Ideally placed to look aesthetically pleasing to the eye, one surround may be the Oddball out to get the best surround sound effect.

 

[AcuDefTechGuy]

Andrew 8 years is really good bro most Marriages don’t last that long anymore.

Should only marry Yamaha’s. Might last longer.

 

[highfigh]

Well, it has lots of straight wires in it and gains. Although some may bend a bit.

Gotta be careful with those bends, or the electrons will shoot right out and hit something else. If you ever hear a slight 'ping' sound inside, that's what's happening.

True story.