That's an interesting interpretation of Steve's comment CharlesI'd have said he doesn't think that Nelson fits into JCX's original comment, which had absolutely no relevance to peoples design abilities.
Tony.
So you'll sure care to elaborate what Steve Eddy really meant, don't you?
For me what Steve Eddy wants to say is clear.
John, Charles, Thorsten, all have sais that they are listening blind, but NOT some "blinded" protocols, and they have said why not.
Did you read anywhere that NP said he uses one of the "blinded" protocols that JC, CH and TL refuse to use?
That's an interesting interpretation of Steve's comment Charles
Tony.
Tony, I have no idea what you are talking about. JCX said that the "standards" on this forum (or thread) are lower than the "standards" of a peer-reviewed journal, because the only thing that apparently counts here is the result of (non-double blind) listening tests.
Then Joshua asked if the the listening tests of respected and successful designers didn't count for something, giving some specific examples of designers who have been active on this thread (at least until Thorsten was temporarily banned). Each of these designers clearly and publicly have stated their reliance on listening tests over any other method, including anything from the peer-reviewed journal (there's only one that I know of in this country that covers audio).
Next Steve Eddy said that Nelson Pass shouldn't be included on the list of designers. One way to take that would be that he thinks that Nelson Pass isn't good enough to be included on Joshua's list. Somehow I doubt that's what he meant. The other way to take it is that for some reason he believes that Nelson Pass doesn't belong on Joshua's list because he is somehow better or above the other designers Joshua listed.
But you apparently have some other interpretation of what Steve meant. Whatever that might be, it is eluding me at this moment. Perhaps you would be so kind as to clarify what you think Steve meant.
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Exactly.
Here is some very clear recent evidence, from the February 2011 Stereophile review of the Pass INT-150 integrated amplifer:
Integrated Amp Reviews
Pass Labs INT-150 integrated amplifier
By Erick Lichte • Posted: Jan 26, 2011
Ten thousand hours. According to Malcolm Gladwell, in his book Outliers: The Story of Success,
it takes 10,000 hours of practice to become truly exceptional in your field. For any endeavor,
Gladwell contends, what will get you to Carnegie Hall isn't inborn talent but practice, practice,
practice.
....Pass hit a critical mark in his own life as a listener. As he told me in an illuminating interview,
"Over the course of the last 40 years, I finally got my magical 10,000 hours of listening in, and
this has given me a more mature viewpoint on a lot of things. The ability to listen has become a
larger part of the picture for me when designing and manufacturing products." Pass
credits the development of his current X series of amplifiers, and their Super-Symmetry circuit,
not only to his constant curiosity as a designer of electronics, but to his increased powers
of listening.
If I am somehow misinterpreting this, and Nelson is actually using "peer-review journal approved" listening tests, I would say two things:
a) I am sure that he will be the first to step in and correct me.
b) He should write an article for the "peer-review journal" describing his findings, as it would be a breakthrough of the greatest magnitude.
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Hi Charles, I'm not going to try and put words into Steve's mouth, I was just pointing out that I can't see how you can extrapolate that he was saying you are a bad designer!! How does the amount of rigour used in conducting listening tests relate to how good a designer someone is??
Maybe Steve was saying that he thinks that Nelson is more rigourous in his Listening tests (I don't know the answer to that).
If you use listening tests as part of your design process then I say good for you, if that results in a product that is better received then even better! If you don't want to look further into it than it was better received and your happy with that, then that is also your prerogative!
But, I completely and utterly fail to see how Steve's comment when taken in the context of JCX's original statement can be taken as a slight on your, or anyone else's design skills.
Tony.
Sure Ed, but it's just conjecture of your part that he didn't mention the Rk as feedback because he thought it wasn't.
Here's another conjecture: he was so preoccupied with getting his head around his new invention that he didn't realise that the Rk was also a form of nfb.
OK, one more: he realised late at night that the Rk was also a form of nfb but he thought, what the heck, I just wont mention it and see if anyone catches it.
My interest is in better understanding of circuits and if you realize degeneration is a form of nfb it clarifies several things at once: the gain of an ef being 0.9xxx and asymptotically going to 1.000 with the 100% nfb and a infinite transistor beta; or the fact that an ef can oscillate, as a result of phase shifted feedback with still present loop gain.
Occam's razor and all that; but maybe I'm just lazy
jan
But
my point is that, designers can find ways to go around what seemed to be the vouge, in fashion at the moment without feeling guilty about it....
after all the whole point in the manufacture of audio gears is to come up with products that sell.....
just like in the movies, they want a blockbuster each time....so then advertising has a lot to do to make that happen.....
If the word "degeneration" has unpleasant connotations in some cultures then don't use it in advertising. Actually, I can't imagine why advertising would want to mention a perfectly normal circuit technique. Do people proclaim loudly that their circuits include both coupling and decoupling? I suppose in the hands (pen?) of an ad man even this could become a 'feature': "Our circuit uses a finely balanced set of couplers and decouplers, carefully chosen after extensive research to provide exactly the correct response at frequency extremes." Well, I should hope any designer can understand first order filters!
I suppose some people might regard "negative feedback" as being, well, negative and therefore a bad thing. What if we called it 'positive correction'? Then everyone would want it in their amp.
Note that the argument here is not primarily about what to call it, but what it is. Degeneration is feedback. Because it is only over one stage the stability issues can be simpler than for feedback over several stages. Whether a particular circuit arrangement is 'global' or 'local' feedback is just a matter of naming: the equations are the same, the stability criteria are the same etc. If you put feedback around a one-stage amp, is that local or global feedback? Silly question, which shows that there is no fundamental difference between them. The real issue is over how many stages does the feedback loop go? Or better still, over how many poles?
I suppose some people might regard "negative feedback" as being, well, negative and therefore a bad thing. What if we called it 'positive correction'? Then everyone would want it in their amp.
Note that the argument here is not primarily about what to call it, but what it is. Degeneration is feedback. Because it is only over one stage the stability issues can be simpler than for feedback over several stages. Whether a particular circuit arrangement is 'global' or 'local' feedback is just a matter of naming: the equations are the same, the stability criteria are the same etc. If you put feedback around a one-stage amp, is that local or global feedback? Silly question, which shows that there is no fundamental difference between them. The real issue is over how many stages does the feedback loop go? Or better still, over how many poles?
Yes, everyone even moderately educated in electrical engineering circuit theory knows that emitter follower has 100% voltage feedback. I do not understand why some resist to admit this fact, the only reason seems (sadly) to be a marketing reason.
http://fourier.eng.hmc.edu/e84/lectures/ch4/node9.html
http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/negfeed.html
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The argument wasnt about wheter it is feedback or not. It was about whether its the same as a even short loop around a transistor (which you can deliberately open and close) or not.
Nelson stated that it is not and I agree with him. He never said it is not a form of feedback.
Why on earth are some of you always starting arguments about such things?
Nelson stated that it is not and I agree with him. He never said it is not a form of feedback.
Why on earth are some of you always starting arguments about such things?
But he has talked in one of his articles about adding feedback (from collector/drain to base/gate - I forget which) and the effect this has, when the original circuit already had degeneration so already had (unmentioned) feedback present.sottomano said:
You can easily open and close degeneration, by using a switchable decoupler.
The argument started when someone said "I don't use feedback, but degeneration is good" or words to that effect. If someone said "I don't eat fruit, but I like apples" would you not want to point out to them that apples are fruit too? Is that being argumentative?
Ultralinear is a type of feedback. Like some other feedback methods, the feedback and the input signal actually go in at different ports (e.g. LTP, CF).
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I agree. There are many different ways to apply feedback; an emitter follower/degeneration, local around a single stage or transistor, global around all stages.
Then there's nested feedback with loops nested within each other, over progressively more stages, as advocated by Cherry.
It can be argued that Hawksford-type error correction, which uses a combination of positive and negative feedback, is, in the limiting case, a clever application of negative feedback theory.
Or, even more clever, Quad-style Current Dumping.
All subject to basic feedback and stability theory.
And sometimes it is necessary to discuss these things to make clear what one means, and learn from other people. I wouldn't want to miss that opportunity!
jan
ISTM there's a subtext here. Its about whether its an engineering (i.e. honest) use of the word 'feedback' to claim that an amplifier which includes emitter followers and emitter degeneration in general is 'zero feedback'.
They might put an explanatory note (maybe they did?) into user manual, like:
The term "Feedback" herein means global, loop negative feedback. The statement "zero feedback amplifier" means we do not use the global loop negative feedback, but we may use many kinds of feedback in more common meaning. We use non-loop negative feedbacks like followers, emitter degenerations, nested feedbacks and many other kinds of this circuit design techniques
The term "Feedback" herein means global, loop negative feedback. The statement "zero feedback amplifier" means we do not use the global loop negative feedback, but we may use many kinds of feedback in more common meaning. We use non-loop negative feedbacks like followers, emitter degenerations, nested feedbacks and many other kinds of this circuit design techniques
Degenerated or not, what is the difference anyway? Our beloved 2SK170 has a transconductance of about 22mS or 45Ohms, so even without any source resistor it is "degenerated". I think it wouldn't be a fraud if one says its a no NFB circuit. And sure applying a loop around a gain stage, whether local or not, is a different thing, as you arbitrarily are choosing an OLG value and a CLG value, with all implicit consequences. Dont tell me you can do that with pure followers, adding a resistor. Or how much loop gain @ 20kHz and at 100kHz has a 2SK170 with a 50 Ohms source resistor compared to one with 5 ohms?
Yes it was a typo, the Cf and the gbw of the op-amp and the 2000pF form a critically damped two pole signal response. The noise gain rises at high frequencies but this is easily passively post filtered and pretty benign anyway. I no longer have the plots so can make no specific claims.
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Well, I can't be bothered to do it but someone familiar with the device and feedback theory could work it out and tell you the answer, as it is a perfectly respectable engineering question which you pose. A 'pure follower' has a very well-defined OLG and CLG. You would need to know that in order to calculate the distortion it will add.sottomano said:
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