Actually simple harmonic distortion can cancel under some conditions. It is a useful design technique in amplifier stages.
Morinix, that is a good website for showing what we try to do with TOPOLOGY to lower inherent distortion, SO THAT we do NOT have to use so much negative feedback or even zero global negative feedback. Why do we want this? Because there is SOME distortion that may NOT be measurable by normal test equipment that the ear DOES pick up on. I am sure that these 'distortions' exist. There is too much evidence toward their existence.
Hi John, just curious because of the rampant stream of consciousness in this thread. Just lately I come to find this thread that started in part 1 nearly SIX AND A HALF YEARS AGO
. Since I don't have the time to read every post I was just intrigued how these recent analyses related to the lamentation of the original poster not being able to find a schematic. Let me ask you this; If someone on this forum presented a correct outline of what you did on the design of the Blowtorch would you cop to it?
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> Actually simple harmonic distortion can cancel under some conditions.
> It is a useful design technique in amplifier stages.
That may be for special planned instances, but in general
distortion does not mask distortion.
This is incredibly unknown !
The (say) 1% produced by an amp can be discerned with
a speaker producing (say) 10% as easily as if the speaker
produced (say) 1% (or 0% for that matter)
(by discerned I mean recognized if switched on/off)
> It is a useful design technique in amplifier stages.
That may be for special planned instances, but in general
distortion does not mask distortion.
This is incredibly unknown !
The (say) 1% produced by an amp can be discerned with
a speaker producing (say) 10% as easily as if the speaker
produced (say) 1% (or 0% for that matter)
(by discerned I mean recognized if switched on/off)
Good to know.
Hmmm, well, enough posters to have this thread in the 1st grade if it was a person.
Never been down there, had a few amps that still worked at 130K or so. Never published the data which is too bad, it was a nice survey of GR noise across several manufacturers over extreme temp ranges.
I believe I specified that the added distortion was of substantially the same character, and a many thousands of times less in magnitude when talking feedback R vs dynamic driver voice coil heating effects
anyone want to bet they can tell 5% 2nd order nonlinearity from 5.01%, or 5% 2nd cascaded with 0.01% 2nd - that 0.0005% 4th sure must stick out like a sore thumb - right?
we might be able to construct test signals that give a IMD products from the above guestimated 4th term that clears the masking threshold - but with music I really doubt it can be heard
and I've still got a couple of orders of magnitude "in my pocket" if you really followed the Z-Foil vs voice coil numbers at all
anyone want to bet they can tell 5% 2nd order nonlinearity from 5.01%, or 5% 2nd cascaded with 0.01% 2nd - that 0.0005% 4th sure must stick out like a sore thumb - right?
we might be able to construct test signals that give a IMD products from the above guestimated 4th term that clears the masking threshold - but with music I really doubt it can be heard
and I've still got a couple of orders of magnitude "in my pocket" if you really followed the Z-Foil vs voice coil numbers at all
See my website below- last page about 2/3 rds of the way down. Martin Collums (spelling?) take on the subject from about 20 years ago.
Some laughed, and some claimed they saw the light after that one.
Morinix, you asked me a 'flip' question and I gave you a 'flip' answer.
In all actuality, 95% of anything that the CTC Blowtorch has in it, has been put up here. I just don't publish my more recent schematics of my personal designs. I still make a living giving other companies my designs, and I cannot dilute their value, by giving them away here, completely. Actually, I have been very generous with my input, and will continue to do so, when I get a serious question.
In all actuality, 95% of anything that the CTC Blowtorch has in it, has been put up here. I just don't publish my more recent schematics of my personal designs. I still make a living giving other companies my designs, and I cannot dilute their value, by giving them away here, completely. Actually, I have been very generous with my input, and will continue to do so, when I get a serious question.
If you read Samuel's thesis you would find many of these measurements with no noise or interferors to explain away, quite an excellent job. There are several ordinary caps and resistors that truely make the distortion not matter.
Thanks, lots of letters too I'll have to print it out for the next trip to the loo.
Not exactly what the article is about Scott, but if you recall what I have shown about it so far in this thread, there are some interesting issues.
As has been mentioned and a few bits of data shown, one very important issue is to be sure that when you take measurements you are measuring the right parameters.
So to evaluate feedback schemes and theory one needs to have a repeatable series of tests that correspond to skilled listeners. That brings up the issue of what is a skilled listener and can they be trained?
I have already pointed out that even finding a switch with less distortion than many components is a very difficult task. So the current comparative listening technique does not rely on a switch!
Now my current article is on power supplies. It was supposed to be a short one but it is coming up on 20,000 words. One of the feedback related issues is how noise causes errors and what kind of errors. Although I have a noise generator (Previously shown here) there is no standard on how to measure noise and it's influence on real world equipment. There are lots of tests going the other way!
So the simple article on feedback has several issues that need to be examined a bit more fully.
But just for you, in any feedback design one must be sure that under any condition such as noise, out of band signals, multiple uncorrelated signals, transients or envelope modulated signals the circuitry does not clip, slew rate limit etc. This is best realized by modest requirements for the feedback.
Clipping and slew are are all part of the design process, plenty of amplifiers with gobs of feedback work fine. I'll remind you xDSL amplifiers operate totally starved on supply current use lots of conventional feedback and have low distortion into 50 Ohm loads at 30+MHz. They also operate in horrible environments (phone cabinets at max allowed heat).
Hi Ed,
would you mind to elaborate bit the right parameters and repeatable series of tests that correspond to skilled listeners?
Thanks,
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