For the record, in case it is not well understood, I did not stop in my education when I graduated in 1966. I took after-hours courses on servo design (Dr.Dorf), filters (Orchard and Temes) and even a course on IC design, when I was at Ampex.
Later, I took courses at UCB in both undergraduate and graduate analog engineering from R.G.Meyer, and Don Pederson. This is where I got my best insight as to how devices really work. Topology is a separate subject. (It seems to be innate in me)
Later, I took courses at UCB in both undergraduate and graduate analog engineering from R.G.Meyer, and Don Pederson. This is where I got my best insight as to how devices really work. Topology is a separate subject. (It seems to be innate in me)
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John,
It would be silly to call you on your education and practical experience in the field. That is some of what I was alluding to. Many people go to school just to take classes and never go to get that piece of paper that says I have a degree. Others never set foot on a college but are voracious readers of technical literature and I am sure there are many of those here and in other forums, but that doesn't mean they don't also have massive amounts of practical experience also. I am mostly self taught in my own field of plastics but I must say that at the time I was doing what I was there were only about 50 people in the entire country working in my particular area. I had some of the most educated chemist in my shop with PhD's in chemistry that taught me something and I them as I had the practical experience and more R&D under my belt than they would ever get. They got to theorize and I got to make it happen in a real program. I just got asked to contribute to a University program for advanced composites, not because of any educational background, but because of my actual real life application of some development that I was one of the only people to have ever done. They do not want my knowledge to just be lost, someone else would have to reinvent what I have already done. I have been a seminar speaker in my particular field and the room was full of nothing but engineers from GM, Ford, Hoover Vacuum, Whirlpool and so many others I can't remember. This was because I could talk about something that was not in any text book, it was only in my head and nowhere else. That is why I think that you have such a following here, not for your book knowledge, but for your practical applications in real life. You have been successful with your designs, you have the knowledge and the insights and that is why we are here. To pick your brain and understand what made you do what you did and why if you are willing to share that information. Technical application of data sheets will only take you so far, then the art of the design takes over. It is the little things that make the difference otherwise many designers would have made the same decisions you did, but it is more than that in circuit design, it is the end result that tells the story.
It would be silly to call you on your education and practical experience in the field. That is some of what I was alluding to. Many people go to school just to take classes and never go to get that piece of paper that says I have a degree. Others never set foot on a college but are voracious readers of technical literature and I am sure there are many of those here and in other forums, but that doesn't mean they don't also have massive amounts of practical experience also. I am mostly self taught in my own field of plastics but I must say that at the time I was doing what I was there were only about 50 people in the entire country working in my particular area. I had some of the most educated chemist in my shop with PhD's in chemistry that taught me something and I them as I had the practical experience and more R&D under my belt than they would ever get. They got to theorize and I got to make it happen in a real program. I just got asked to contribute to a University program for advanced composites, not because of any educational background, but because of my actual real life application of some development that I was one of the only people to have ever done. They do not want my knowledge to just be lost, someone else would have to reinvent what I have already done. I have been a seminar speaker in my particular field and the room was full of nothing but engineers from GM, Ford, Hoover Vacuum, Whirlpool and so many others I can't remember. This was because I could talk about something that was not in any text book, it was only in my head and nowhere else. That is why I think that you have such a following here, not for your book knowledge, but for your practical applications in real life. You have been successful with your designs, you have the knowledge and the insights and that is why we are here. To pick your brain and understand what made you do what you did and why if you are willing to share that information. Technical application of data sheets will only take you so far, then the art of the design takes over. It is the little things that make the difference otherwise many designers would have made the same decisions you did, but it is more than that in circuit design, it is the end result that tells the story.
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Thanks Kindhornman, for your insight. I think of you as highly educated and experienced, but without a great deal of knowledge of hi end audio electrical design. Let's keep our appreciation of each other's developed knowledge and understanding, in order to facilitate better information flow (serious language '-) on this thread.
Here's a little better illustration:
Attachments
Kind of reminds me --- Compare; How many electronic course books does one have to read in order to pass electronic courses towards a science degree? A few dozen? Several dozen? One hundred?
And, then how many more books has a practicing engineer read and studied in the 30-40 years afterwards? Several hundred? Several thousands? After basic studies are over, its what you learned and did afterwards that counts the most.
Thx-RNMarsh
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Richard is right. People might quibble that I do not always follow engineering procedures that are supposed to have been instilled in engineering school.
It has been done before.
Except for math, I learned most of my design of electronics working with people who WERE full engineers, and who showed me how to get to the 'essence' of a problem, rather than do a thesis on it.
Let me give everyone an example: About 40 years ago, or more, I was taking one of those engineering classes at UCB, and just before class started, I was with several other students, who were looking over their homework for the class.
One guy looked at this whole page of math and stated: "I understand everything, but this factor of 10" I glanced at his calculations and said: "That is gain of the jfet stage that we are analyzing, you know, GmR(load)." The student had lost the 'forest' by just looking at the 'trees'. That's the sort of insight you gain when you have spent a number of years working on designs in industry, before attending that particular class. '-)
It has been done before.
Except for math, I learned most of my design of electronics working with people who WERE full engineers, and who showed me how to get to the 'essence' of a problem, rather than do a thesis on it.
Let me give everyone an example: About 40 years ago, or more, I was taking one of those engineering classes at UCB, and just before class started, I was with several other students, who were looking over their homework for the class.
One guy looked at this whole page of math and stated: "I understand everything, but this factor of 10" I glanced at his calculations and said: "That is gain of the jfet stage that we are analyzing, you know, GmR(load)." The student had lost the 'forest' by just looking at the 'trees'. That's the sort of insight you gain when you have spent a number of years working on designs in industry, before attending that particular class. '-)
Seen ARGO ?
Actually, very little knowledge of anything and everything ever gets written down and put into publication.
And, what small percentage of people's knowledge did get put down in writing, is too much for anyone to read in a life time.
Thx-RNMarsh
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Mr. Marsh,
before reading a book, one has to master the language on the printed pages.
Merely coping with the mother tongue, is a primary limitation for the subsequent educational stage. (just a side note, no criticism intended)
Restraining the choice of books to read within narrow theme boundaries is a secondary limitation.
(we are, we are, we are the Quads)
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hmm, looks like an advertisement rather than an interview. Kodak has never been able to seriously break into digital, whether it be with cameras or printers and they stand to lose a lot of money. I dont wish film would go away, it has a soft clipping that digital still struggles with, but I do believe that digital is the way to go. he completely fails to mention that shooting on film you must pay for high end capture to work with it, because production will in 99% of all cases and all shots be digitally composed, so you have to effectively shoot it twice.
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sure, of course they have got their fingers in, but they do not have anything approaching the market share/dominance they had in film. Leica are very nice little cameras (although its the optics and build quality that make them good IMO) but hasselblad, nikon, canon, even olympus are all way ahead in camera tech and kodak dont even get a look in when it comes to the new film ie SD cards.
kodak cameras are not taken very seriously, being primarily point and shoot cameras for people who dont know any other names
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Getting back to circuit design:
It is also useful to look at the second stage of the Vendetta SCP-1, as it has the property to lower the input capacitance by removing what we call, 'Miller multiplication' of the input devices Crss (see graph) that could actually dominate the input capacitance, if we let it.
However, since we did cascode the first stage, we get much lower input capacitance.
Now let us estimate about how much input capacitance there is?
We have to add one example of the Ciss of a 2SK170 at operating voltage with one example of the Ciss of a 2SJ74, multiply that by 5, and we should get a get a pretty close approximation of the input capacitance of the circuit.
First, let's set the working voltage at 9V or so. Then the Ciss for the K170 is about 30pf, and the Ciss of the J74 is about 100pf, so the sum of the two is 130pf. Now we multiply that by 2.5 for the correction factor for actually using the 2SK147, 2SJ72 in this design, and then by 2 again, because there are 4 devices in the input stage.
So we come out with a total input capacitance of 650 pf. (approximately)
Now that gives us the input capacitance, what is its effect on bandwidth, for example?
Let's say that we use 100 ohms as worst case MC resistance. Then the bandwidth would be about 2.5MHz, good enough for just about anybody, even in worst case. However, what about the LINEARITY of the input capacitance. Well, it isn't completely linear, that can be easily seen by the graphs. They would be straight lines across the page. Since they are not, you have to 'eyeball' the 'RATE OF CHANGE' of the curves, knowing that this shows the amount of non-linearity from a straight line, but with such a narrow range of operation, namely approximately 9V with a slight deviation on either side, you have to go to device theory to estimate it, or you just note that it is not going to effect the design much, because 100 ohms is the upper limiting value for the design. Don't try this with moving magnet cartridges, it's a different design that is needed.
In any case, IF in doubt, MEASURE WORST CASE. This is the easiest way to get results.
It is also useful to look at the second stage of the Vendetta SCP-1, as it has the property to lower the input capacitance by removing what we call, 'Miller multiplication' of the input devices Crss (see graph) that could actually dominate the input capacitance, if we let it.
However, since we did cascode the first stage, we get much lower input capacitance.
Now let us estimate about how much input capacitance there is?
We have to add one example of the Ciss of a 2SK170 at operating voltage with one example of the Ciss of a 2SJ74, multiply that by 5, and we should get a get a pretty close approximation of the input capacitance of the circuit.
First, let's set the working voltage at 9V or so. Then the Ciss for the K170 is about 30pf, and the Ciss of the J74 is about 100pf, so the sum of the two is 130pf. Now we multiply that by 2.5 for the correction factor for actually using the 2SK147, 2SJ72 in this design, and then by 2 again, because there are 4 devices in the input stage.
So we come out with a total input capacitance of 650 pf. (approximately)
Now that gives us the input capacitance, what is its effect on bandwidth, for example?
Let's say that we use 100 ohms as worst case MC resistance. Then the bandwidth would be about 2.5MHz, good enough for just about anybody, even in worst case. However, what about the LINEARITY of the input capacitance. Well, it isn't completely linear, that can be easily seen by the graphs. They would be straight lines across the page. Since they are not, you have to 'eyeball' the 'RATE OF CHANGE' of the curves, knowing that this shows the amount of non-linearity from a straight line, but with such a narrow range of operation, namely approximately 9V with a slight deviation on either side, you have to go to device theory to estimate it, or you just note that it is not going to effect the design much, because 100 ohms is the upper limiting value for the design. Don't try this with moving magnet cartridges, it's a different design that is needed.
In any case, IF in doubt, MEASURE WORST CASE. This is the easiest way to get results.
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True. Though, it would not matter. All which has been writen down is but the tip of the ice-berg of all accumulated or even existing knowledge.
JC... this is great -- your getting into a tutoring mode.
"If in doubt, measure." Measure. Measure. Measure.
Thx-RNMarsh
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John, about that non-linear capacitance, I never really grasped the consequences.
For me, non-linear capaciatnce is a capacitance changing in value with the momentary signal level. Do I get that right?
Then, what would be the effect? Intuitively I would think that a varying capacitance would lead to a varying turnover frequency (your example of 100 ohms and the cap); but since that cap would vary DURING the cycle, what would then be the effect? It would vary the gain DURING the signal cycle so would lead to plain old THD, right? And odd order at that?
jan
For me, non-linear capaciatnce is a capacitance changing in value with the momentary signal level. Do I get that right?
Then, what would be the effect? Intuitively I would think that a varying capacitance would lead to a varying turnover frequency (your example of 100 ohms and the cap); but since that cap would vary DURING the cycle, what would then be the effect? It would vary the gain DURING the signal cycle so would lead to plain old THD, right? And odd order at that?
jan
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