Jahan, I have been playing music for 50 years, listening to high fi big time for 45 years, and a professional designer of audio circuits from microphones to loudspeakers during this time. I rely on my ears and those of my critics for judgement of my designs, just like a chef might rely on his own tastebuds and his critics (customers) as to how well he is preparing a good meal. IF we say that we have found negative feedback problematic, then we have found it so.
Perhaps you have never eaten poor vegetables, but I have them all the time. I just have to go to the discount grocery store. If I go a few blocks away, I can get fresher, more organic produce, BUT I would have a hard time just looking at the vegetables and telling you WHY the big grocery store vegetables don't taste as good.
It is the same with audio. Some people know how, from experience and study, to design high quality audio electronics, yet the measurements or the look of the case might not tell you much as to how they will sound.
Take Sony for example, don't they make attractive equipment? What about Bose?
Why not just buy name brands and stop worrying?
Many of the designers contributing to this thread are world famous for their individual successes in making quality products. You don't have to believe us, but it is a waste of time for us to try to convince you of what you apparently can't hear anyway.
Perhaps you have never eaten poor vegetables, but I have them all the time. I just have to go to the discount grocery store. If I go a few blocks away, I can get fresher, more organic produce, BUT I would have a hard time just looking at the vegetables and telling you WHY the big grocery store vegetables don't taste as good.
It is the same with audio. Some people know how, from experience and study, to design high quality audio electronics, yet the measurements or the look of the case might not tell you much as to how they will sound.
Take Sony for example, don't they make attractive equipment? What about Bose?
Why not just buy name brands and stop worrying?
Many of the designers contributing to this thread are world famous for their individual successes in making quality products. You don't have to believe us, but it is a waste of time for us to try to convince you of what you apparently can't hear anyway.
Nelson Pass said:
I would say that your statement is equally controversial.
Not to me it is
(Sorry, couldn't resist it)But seriously, Johan answered for me in post 1098, I largely agree with him. Although I probably would agree that it also goes for reproducing the original.
There was a time that people put loudness controls in their amps to correct for the different ear sensitivities with level (the Fletcher-Munson curve).
That was done because they were at that time, with the available louspeakers, NOT able to recreate the sound field of the original performance. But here, as in our amplifier endeavours, we try to recreate the 'original' sound as close as possible, 1:1, and then the influence of the ear characteristics play equally in both cases.
The basic error (as I remember it, I apparently lost the paper) of Cheever was that he deliberately made the reproduction deviate from the original by shaping the distortion spectrum, rather than minimizing it. I fail to see how that would give you accurate and faithful reproduction.
If, as in the example with the Fletcher-Munson curves, we were not able to sufficiently reduce distortion to make it all but inaudible, the next best thing could be to shape it to be as little intrusive as possible. But the goal (at least for me) would be to make it insignificant. And we do have the technical means to do that.
Sorry for the off-topic rant....
Jan Didden
GRollins said:
Hi Grey,
I wasn't implying that feedback was a cure-all, only to explain some of the features of that curve. I agree with you that the indiscriminating application of feedback doesn't guarantee accurate and/or enjoyable sound.
On the other hand, if I see all those people that swear by '80-ies amps and pay often more than the original price for them, maybe audio DID stop in the 80-ies, and maybe we are just going around in circles? I mean, if you would do a blind test between a very good regarded 80-ies amp and, say, a JC-2 or an Aleph, are you sure you would hear a clear advantage for the newest incarnation? Something to muse about.
Jan Didden
Johan Potgieter said:
Well stated, Johan. Often the only generalization that is valid is that it is dangerous to generalize.
Plenty of bad amplifiers were made using negative feedback by misguided engineers or cost-cutting marketeers, we all know that. By the same token, plenty of bad-sounding amplifiers have been made with no NFB for misguided reasons. There also exist very, very good amplifiers representative of both philosophies.
Cheers,
Bob
fmak said:
Mmmm, not really. It was done because the ear has a different frequency response for low level sounds than for high level sounds. So, if you would reproduce a high-level event (a live performance) on a low level system (at home), you need to correct for the different freq response to get a lifelike reproduction. As such there is little to argue about I guess.
But now we can reproduce the live event at comparable levels, or at least at levels where the F-M curve is pretty flat.
Jan Didden
PMA said:Though diamonds are girls´s best friend, feedback seems to be engineer´s worst friend. Imagine those wonderful airplanes with open-loop control, no sensors needed!
... except that in a war situation they are shot down by modern planes that have closed loop controls - 'fly by wire' .
Jan Didden
Feedback is for servos, not audio!
By the way, I use significant negative feedback in most of my audio designs. I just know its negative qualities as well. Personally, I was pulled onto this thread by the moderator, but I find most of what is discussed here, rather naive, even if well stated. Just my opinon.
Also, I used the term 'we' to include Charles Hansen, Nelson Pass, and myself. I'm sorry if our 100 years of combined audio design experience doesn't count for much around here.
Go for it, feedback forever!
By the way, I use significant negative feedback in most of my audio designs. I just know its negative qualities as well. Personally, I was pulled onto this thread by the moderator, but I find most of what is discussed here, rather naive, even if well stated. Just my opinon.
Also, I used the term 'we' to include Charles Hansen, Nelson Pass, and myself. I'm sorry if our 100 years of combined audio design experience doesn't count for much around here.
Go for it, feedback forever!
janneman said:
You have missed my point. What you say is generally understood as basic human acoustics response when tested with sine waves. Frankly those who are subjected to such waves for long periods to derive the curves should be so annoyed that they wouldn't want to know what is louder!! it would be interesting to go back and repeat the experiments with measures of subjective annoyance incorporated as a parameter.
These days, nobody integrates loudness curves into volume controls because they don't sound right or good.
john curl said:Feedback is for servos, not audio!
By the way, I use significant negative feedback in most of my audio designs. I just know its negative qualities as well. Personally, I was pulled onto this thread by the moderator, but I find most of what is discussed here, rather naive, even if well stated. Just my opinon.
And no feedback is for "musical instruments". Just the opinion of the majority.
Cheers,
john curl said:I hope that anyone in competition with me in the audio marketplace will use as much negative feedback as they can get into a design.
As most people are hearing impaired and read only specs, it's difficult to be competitive with an amp that sounds perfect, but looks on paper less attractive (in terms of THD).
Cheers,