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Old 3rd August 2013, 02:40 AM   #1161
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Quote:
Originally Posted by Bonsai View Post
It's a pity DS has not spent subsequent effort on mosfets and appears to show little interest in CFA.
I tried to bring his attention on what some call CFA. And had some controversy with him, on what i considered a erroneous analyze of the CFA poles and the supposed distortion cancellation with a differential stage when the inverting one is used for feedback.

When i said to him that, anyway, he cannot leave untold this subject. His response was: "Yes, i can. " !!!
I was very disappointed, as D.S. has some reputation in the audio world.

I believe all the misery about CFA is due to this stupid *C*FA name ! When i was a young engineer, there was not such a name, and it was a very common topology (yet with tubes). I don't know why VFB with differential input stage has took such a monopolistic position on the audio market even with asymmetrical input. Because it looks good on schematics ?
Because some people believe that, adding the same distortion in the feedback path that the one produced by the signal input will cancel distortion, witch is just wrong ?

Quote:
Originally Posted by Dave Zan View Post
Bob Cordell properly attributes credit and it is hard to believe Self has not read that comment.
Everything i have read from Bob Cordel is proper and simple.(clear in his mind, explained in a clear way). I'm not surprised he has too a good knowledge of men and audio history. Don't know for DS, i never bought books from him, and, after his answer, will not.
Anyway, if credits are not so important, as nothing is never totally new in the audio history, good understanding of currents, phases, poles etc. is. As well as common sense.
Like music, it is a too a question of feeling. Never authority.
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Last edited by Esperado; 3rd August 2013 at 02:48 AM.
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Old 3rd August 2013, 02:50 AM   #1162
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Quote:
Originally Posted by Dave Zan View Post
I meant did he refer to the prior Hitachi patent for TMC?........
TMC appears once only as an alias for Output Inclusive Compensation, repeated from his Linear Audio example. Here, in chapter 13, p334ff he makes reference first to Baxendall, Hitachi's Kunio Seki, Gunderson 1984, TDA7293, Rotel RB1090-3 and in combination with specified 2-pole compensated Yamaha designs and also with his Class G design. Reference is also made to comments made by Bob Widlar regarding opamp design (1981)
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Old 3rd August 2013, 03:20 AM   #1163
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Originally Posted by Ian Finch View Post
...in chapter 13, p334ff he makes reference ...Hitachi's Kunio Seki...
That's the one I meant. Thank you.

Best wishes
David
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Old 3rd August 2013, 03:38 AM   #1164
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Quote:
Originally Posted by Bonsai View Post
...little interest in CFA. I get 4 ppm at 20kHz and 350 watts out in sim, and have little doubt that in practice a very good result is achievable. What's not to like about it?
Noise?
The "so called" (as Mike would say) CFAs that I have seen all had noise performance that was inferior to a comparable VFA.
That makes them not likeable for my use (compression drivers) at least.
Is there a "CFA" without this weakness?

Best wishes
David
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Old 3rd August 2013, 06:41 AM   #1165
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Quote:
Originally Posted by Dave Zan View Post
That's the one I meant. Thank you.

Best wishes
David
Chapter 8 in his 6th ed. is about p-p Vas circuits.
It has several sections on the Hitachi circuit - there's at least 5 ToC entries with the Hitachi identifier. Followed by a few sections on the Lender circuit and several more Vas configs.

BTW There will be an extensive Book Review on Doug's book in the upcoming Linear Audio Vol 6 by JPV.

jan
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Old 3rd August 2013, 07:39 AM   #1166
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Default MOSFET Output stages

Quote:
Originally Posted by Ian Finch View Post
Chapter 21 - The FET output stage, is among the shortest with the last reference from 1995. Perhaps that answers your question, Edmond.
[...]
Hi Ian,

No, it doesn't answer my question. Maybe you could check whether the 6th edition still contains the (erroneous!) picture and text as shown below.

Cheers, E.
Attached Images
File Type: png fet1.png (36.6 KB, 142 views)
File Type: png fet2.png (35.5 KB, 142 views)
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Old 3rd August 2013, 08:02 AM   #1167
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OK then; The text and diagram remain unaltered from your posted images above.
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Old 3rd August 2013, 08:13 AM   #1168
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Thanks Ian.
Probably, post #260 explains why it is as it is
Cheers, E.
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Old 3rd August 2013, 09:08 AM   #1169
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Got mine yesterday, ordered (with some Bela Tarr films) last sunday through Amazon french services.

Esperado,

Does-he presents and analyses (with no misunderstanding) current feedback topologies and advantages ?

Drawbacks of so-called CFA are dealt in less than a full page : convincing (p213).

Don't know for DS, i never bought books from him, and, after his answer, will not.


Are you not curious ? You certainly miss something. Even if you are not in agreement with some ideas of the man, you may learn a lot from him.

Everything i have read from Bob Cordel is proper and simple.

I do not like to see Bob Cordell and Douglas Self as rivals. I think they are complementary, each with its own views and approachs, and I enjoy to have two serious authors to read. By the way, have you ever read Peter Baxandall ?
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Old 3rd August 2013, 09:19 AM   #1170
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My first was JLH followed by Self.
Two very different approaches to writing and to amplifier philosophy.
I saw and still see them as complements to each other.
I have since invested in ARRL, Horwitz&Hill, Cordell & Ott.
All are different, all teach me a lot, I do not see any conflict.
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