GRollins said:
If you don't know just say so.
I won't disagree that a little harmonic distortion sounds good. Musical instruments would be dull and lifeless if they only produced the fundamental. It would be like listening to a tone from a function generator.
Does anybody have a link to a reliable test of a high feedback amplifier having worse high order distortion products than a low feedback design? I don't care how dynamic the conditions.
fizzard said:
See the link jcx posted earlier:
http://www.diyaudio.com/forums/showthread.php?postid=920583&highlight=#post920583
GRollins said:
I think it is about time that we get away from the fallacy that our home music should be compared with, sound like, a concert. What concert? A classical concert? The ones I go to often sound muddled, with an abysmal sound stage, all kinds of reflections, and often not so good balance and lack of detail. A good classical recording is much better at letting you hear the individual instrument groups, much better balance between them and so on. You hear details on a good recording that you never hear in a live concert. But that doesn't mean that they 'shouldn't be there'. Don't condemn low distortion, high feedback amps because they let you hear fingers on a string that you don't hear in a live concert. The sound was there, the mic captured it, and the amp reproduced it.
Good recordings and a good amp give you much more about the music than any live event.
But I still go to live concerts. I enjoy the night out, the ambiance, seeing the live performers. I enjoy the music in either case. But it is a little nonsensical to want to cripple the reproduction in your home to make it sound like a live concert.
Jan Didden
If hi fi reproduction does not successfully emulate live music with GOOD source material, then it is mid fi. Feedback is really problematic, and usually compromises the sound quality as much with a good design, as it might make a poor design listenable. The ultimate approach is the best quality open loop design, then you don't need feedback to make the specifications acceptable.
At the very time I am working on an open loop phono amp second stage without feedback. It works, but it has more distortion that I would like to put on the spec sheet. However, if I want to compete with the 'big boys' like Audio Research (tubes) or Ayre (open loop), I must press on. I already know how to make feedback amps, virtually in my sleep.
I am not referring to 'one-upmanship' , or marketing, I am referring to sounding as good or better than my real competition.
At the very time I am working on an open loop phono amp second stage without feedback. It works, but it has more distortion that I would like to put on the spec sheet. However, if I want to compete with the 'big boys' like Audio Research (tubes) or Ayre (open loop), I must press on. I already know how to make feedback amps, virtually in my sleep.
I am not referring to 'one-upmanship' , or marketing, I am referring to sounding as good or better than my real competition.
fizzard said:
Why limit yourself to ad hoc standards? We're not doing mass market design, we're doing diy. We can decide, from a system point of view, what's best and not worry about what will happen when someone attaches it to a Sears rack system.
john curl said:
John,
My point was that we should stop all the time saying: 'but it doesn't sound like a real concert'. Of course it doesn't. Apart from the fact that those real concerts are amplified by amps with gobs of feedback ;-) .
Reproduced music has its own standards. Good source material, reproduced over a good system, can show more soundstage, more detail, more resolution than what you can ever hear over a distorting PA behind 50 people with absorbing clothing.
Everytime somebody looks for an excuse for a special component, low feedback, high feedback, tubes, ic's, you name it, they come up with 'I bet you never go to concerts'. BS to the nth degree.
There are excellent amps with high feedback. You know it, they are among your competitors. There are excellent amps with low feedback. You know it, you built them.
Jan Didden
GRollins said:
Would you say that negative feedback creates the "finger sound," or that lack of negative feedback destroys it? Why does not negative feedback create the "finger sound" on classical recordings?
That "finger sound" is intentional. Classical guitarists keep their nails meticulously groomed in order to do it. And real singers do have a "sheen" on their voice. The recording engineer or the guitarist is to blame if it's too exagerated.
GRollins said:
The problem with a low damping factor is not woofer control. (As long as it is not 2 or something.) It is that the feedback signal is drawn from the load side of the output impedance. This is why a low feedback amplifier that looks really clean with no load gets a whole lot dirtier with even a simple resistor for a load.
SY said:
What standard would you propose then? And what do you think the feasability of achieving that is?
If the output impedance of your amplifier is too low just put a series impedance in there. With feedback you can create virtually any output impedance you want, you can make it 10 ohms, 5 ohms, 0 ohms, -5 ohms...
My listening standard is usually directly recorded female voice. We usually have to live with electronic amplification of bands and even orchestras, today, but IF we know what the sound system sounds like, perhaps by attending a number of performances, or even working with the group, we can still hear through to the original performance, with top quality gear. The rationalization of which needs improvement first, the source or the listening equipment, has been with us since the beginning of audio reproduction.
Please don't get me wrong, I use feedback in almost all my designs, both amps and preamps. It is just that no feedback designs generally sound somewhat better, all else being equal. Why? We really don't know, for sure.
This is an old understanding, and I first heard about it through the late Richard Heyser, in 1968, who has contributed more to audio theory than most any of us. He, just for fun, listened to a zero loop feedback amp that he designed while working at JPL, to land on the Moon. He found it to sound better than expected, MUCH BETTER than expected. He even published the circuit in the AES, and a number of amps were produced by others.
Please don't get me wrong, I use feedback in almost all my designs, both amps and preamps. It is just that no feedback designs generally sound somewhat better, all else being equal. Why? We really don't know, for sure.
This is an old understanding, and I first heard about it through the late Richard Heyser, in 1968, who has contributed more to audio theory than most any of us. He, just for fun, listened to a zero loop feedback amp that he designed while working at JPL, to land on the Moon. He found it to sound better than expected, MUCH BETTER than expected. He even published the circuit in the AES, and a number of amps were produced by others.
I propose no standard. This is diy. I propose that one thinks of the speakers and amps as a system and not be artificially restricted in design, but rather be guided by what works best for a given system. Pete Millett built an amp with continuously variable source impedance for those who worry that they might be changing speakers weekly.
Using added resistance on the output sucks for efficiency and heat. Isn't it better to control source Z via feedback and/or topology?
SY, I just found some papers on current drive and negative impedance drive of loudspeakers in this year's European session of the AES. Maybe they might be useful to you.
janneman,
You either need to listen in better halls or get better seats.
Although far from the best hall, our local Koger Center sounds far better than most of the recordings I own. Charleston also has a decent hall, though the best seats are rather limited.
Sadly, Nicholas Smith, our conductor here, has fallen due to politics. The man was extraordinary. He took a third or fourth rate orchestra (under his predecessor--who shall remain nameless to protect the guilty) and single-handedly hauled them up by their bow ties to the point where--say, ten percent of the time--they were first rate. The rest of the time they were consistently second rate, which I mean as a high compliment, leaving first rate for the likes of the major, established orchestras from cities with far more money and resources than we have out here in the sticks.
I'll miss the man.
fizzard,
Unfortunately, you are completely at sea, and bereft of compass.
I happen to know a thing or two about classical guitar--used to play one. I wasn't speaking of right hand technique, but left hand. The burr of fingers sliding on wound strings is overemphasized in high feedback amplifiers, where distortion products pile up in the upper midrange and treble. This holds true for electric (which I play these days) or acoustic (regardless of string type).
You go to the trouble to say that damping factor isn't important, then imply that it is in the case of an amplifier with low feedback because the signal gets 'dirtier' when driving a speaker, by which I gather that you feel that the feedback itself is then contaminated, which then presumably pollutes the signal once it's returned to the front of the amplifier. All of which being such a logical muddle that I hesitate to even try to unravel it. Did you mean that a high feedback amp delivers 'clean' feedback to the front end? Low feedback makes things worse by not being higher? High feedback amps don't get 'dirtier' when presented with a real world load instead of a resistor? You should hook up low feedback loops somewhere other than the output--but leave high feedback loops hooked to the load?
It's all very simple. This is DIY. You are free to use triple digit levels of feedback if you want. But before you try to convince others that you've got a point, you might want to spend some time alone, clarifying in your own mind what you feel to be the case. At present it doesn't appear that you've thought your own position through.
Grey
You either need to listen in better halls or get better seats.
Although far from the best hall, our local Koger Center sounds far better than most of the recordings I own. Charleston also has a decent hall, though the best seats are rather limited.
Sadly, Nicholas Smith, our conductor here, has fallen due to politics. The man was extraordinary. He took a third or fourth rate orchestra (under his predecessor--who shall remain nameless to protect the guilty) and single-handedly hauled them up by their bow ties to the point where--say, ten percent of the time--they were first rate. The rest of the time they were consistently second rate, which I mean as a high compliment, leaving first rate for the likes of the major, established orchestras from cities with far more money and resources than we have out here in the sticks.
I'll miss the man.
fizzard,
Unfortunately, you are completely at sea, and bereft of compass.
I happen to know a thing or two about classical guitar--used to play one. I wasn't speaking of right hand technique, but left hand. The burr of fingers sliding on wound strings is overemphasized in high feedback amplifiers, where distortion products pile up in the upper midrange and treble. This holds true for electric (which I play these days) or acoustic (regardless of string type).
You go to the trouble to say that damping factor isn't important, then imply that it is in the case of an amplifier with low feedback because the signal gets 'dirtier' when driving a speaker, by which I gather that you feel that the feedback itself is then contaminated, which then presumably pollutes the signal once it's returned to the front of the amplifier. All of which being such a logical muddle that I hesitate to even try to unravel it. Did you mean that a high feedback amp delivers 'clean' feedback to the front end? Low feedback makes things worse by not being higher? High feedback amps don't get 'dirtier' when presented with a real world load instead of a resistor? You should hook up low feedback loops somewhere other than the output--but leave high feedback loops hooked to the load?
It's all very simple. This is DIY. You are free to use triple digit levels of feedback if you want. But before you try to convince others that you've got a point, you might want to spend some time alone, clarifying in your own mind what you feel to be the case. At present it doesn't appear that you've thought your own position through.
Grey
The best THD that you can get from a loudspeaker at low listening levels is like 0.1% and it goes easily to 3% if you crank up the volume a bit. IMD for loudspeakers is equally high and high order armonics are easily produced. It's sound reflection and diffraction in loudspeakers and rooms what damages imaging (not to mention room reverberation), and it's energy storage in loudspeaker diaphragms and other mechanical elements what destroys "definition".
This discussion is nearly pointless. Amplifiers are all just too perfect (except the funny ones with 8 ohm output impedance, of course). We are seeking the perfect solution to the wrong problem, as usual 😀
This discussion is nearly pointless. Amplifiers are all just too perfect (except the funny ones with 8 ohm output impedance, of course). We are seeking the perfect solution to the wrong problem, as usual 😀
Grey, I also used to play classical or folk guitar. I still have an electric. Fully 5 years before I got into doing hi fi design as an avocation, I concentrated on acoustical and electric guitars and amps. I think that I got my listening ability ' tuned up' at that time.
So I can expect the Halcro amplifier to sound like crap? And if I play bass notes I should hear garbage spewing from the tweeter? Don't be so silly.
John,
And in one of those "small world" kinda things, I've owned two '70s era Alembic Series One basses--still have one of them--and use an F1-X preamp in one of my amplification setups. Began building my own instruments about fifteen years ago, including winding my own pickups and designing my own active electronics. Although I've played a little guitar here and there, sung too, when circumstances warranted, I regard myself as a bassist. It's made me rather picky about how low end is reproduced on my stereo.
Playing acoustic vs. electric gives you a different perspective but it's for damned sure it's not (as the idiots used to say) that "it doesn't matter whether the stereo's any good, 'cuz the guitars are distorted anyways!" In principle you can learn to listen by training your ear on electric instruments but, regardless of how much I love to play electric bass, if push comes to shove I'll take acoustic instruments as a learning/listening reference.
My oldest daughter (the one who's out there in Berkeley for grad school in chemistry/biochemistry) plays cello pretty well and I love to listen to her play. Given that cello is used both in full orchestral settings and in smaller groups like quartets and such, it's a great reference to hear her play and to be able to choose my listening distance, then compare that to full orchestral use or cello concertos.
There's no doubt that I acquired a lot of my ability to focus exclusively on a single instrument, ignoring all else, by playing. It's an invaluable skill as a musician...and as a listener.
Grey
EDIT: fizzard, you posted while I was still writing.
Sorry, but you still don't get it. You claimed earlier to truly want to understand, but given your behavior in this thread and in an older one that you have resurrected, you actually have no interest in understanding. Since you have no intention of accepting what's been said in this thread or in the other, and you clearly have no inclination to educate your ears and sit down to listen for the differences, then there's not really a lot more that can be done.
I was once as convinced as you are now that feedback was The Answer To All Ills. I was pretty hard-headed about it. I got over it, but it took longer than I like to admit.
They say that experience is the best teacher. I've been on both sides of this particular issue. I know that NFB seems logical--so logical and wonderful that you don't even want to look at things any other way. Been there...done that. But the thing is that NFB is like a beautiful woman who also happens to go slightly berserk when the moon is full. Your eyes see the beauty and it's easy to be seduced. You think you can control the madness and that if you succeed then that matchless beauty will be yours forever.
But it's a seduction by the Dark Side. You've unwittingly made a pact with the devil.
And in one of those "small world" kinda things, I've owned two '70s era Alembic Series One basses--still have one of them--and use an F1-X preamp in one of my amplification setups. Began building my own instruments about fifteen years ago, including winding my own pickups and designing my own active electronics. Although I've played a little guitar here and there, sung too, when circumstances warranted, I regard myself as a bassist. It's made me rather picky about how low end is reproduced on my stereo.
Playing acoustic vs. electric gives you a different perspective but it's for damned sure it's not (as the idiots used to say) that "it doesn't matter whether the stereo's any good, 'cuz the guitars are distorted anyways!" In principle you can learn to listen by training your ear on electric instruments but, regardless of how much I love to play electric bass, if push comes to shove I'll take acoustic instruments as a learning/listening reference.
My oldest daughter (the one who's out there in Berkeley for grad school in chemistry/biochemistry) plays cello pretty well and I love to listen to her play. Given that cello is used both in full orchestral settings and in smaller groups like quartets and such, it's a great reference to hear her play and to be able to choose my listening distance, then compare that to full orchestral use or cello concertos.
There's no doubt that I acquired a lot of my ability to focus exclusively on a single instrument, ignoring all else, by playing. It's an invaluable skill as a musician...and as a listener.
Grey
EDIT: fizzard, you posted while I was still writing.
Sorry, but you still don't get it. You claimed earlier to truly want to understand, but given your behavior in this thread and in an older one that you have resurrected, you actually have no interest in understanding. Since you have no intention of accepting what's been said in this thread or in the other, and you clearly have no inclination to educate your ears and sit down to listen for the differences, then there's not really a lot more that can be done.
I was once as convinced as you are now that feedback was The Answer To All Ills. I was pretty hard-headed about it. I got over it, but it took longer than I like to admit.
They say that experience is the best teacher. I've been on both sides of this particular issue. I know that NFB seems logical--so logical and wonderful that you don't even want to look at things any other way. Been there...done that. But the thing is that NFB is like a beautiful woman who also happens to go slightly berserk when the moon is full. Your eyes see the beauty and it's easy to be seduced. You think you can control the madness and that if you succeed then that matchless beauty will be yours forever.
But it's a seduction by the Dark Side. You've unwittingly made a pact with the devil.
Yeah, but why does it have to take so (mumble, grumble, mutter, mutter...) long to get there?
Grey
(George Bernard Shaw: Youth is wasted on the young.)
Grey
(George Bernard Shaw: Youth is wasted on the young.)
GRollins said:
Grey, nice story, but of course completely irrelevant to the discussion at hand.
(I snipped the rest of the post as it apparently was not aimed at me)
Jan Didden
john curl said:
Agreed. We have a small cafe around here (Cafe Classic, I have to take SY there next time he's here), which has what they call an Open Stage. People come in, grab a guitar and start to perform. Or they go around finding someone who plays the piano and sing. Sometimes when I'm there I just listen to the music and sip my beer. Other times I try to unravel the sound, to hear attacks, 'sheen', dynamics. It's a nice way to do a reality check. But mostly I sip my beer 😉
Jan Didden
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