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John Curl's Blowtorch preamplifier part II
John Curl's Blowtorch preamplifier part II
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Old 10th December 2011, 02:25 AM   #18891
Wavebourn is online now Wavebourn  United States
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John Curl's Blowtorch preamplifier part II
Quote:
Originally Posted by scott wurcer View Post


BTW - That op-amp history also shows that Dick Burwen pioneered the use of inductors across input degeneration resistors, sort of the worst of both worlds in this sense. Not that that is my opinion.
Op-amp history reminds me history of Global Economy... Run for parameters that are far from real requirements. Like, eliminating assets to show better profit US companies lost future, the same with ICs for analog audio.
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Old 10th December 2011, 02:28 AM   #18892
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Kind of like American cars, back in the '50's or '60's, Wavebourn? '-)
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Old 10th December 2011, 03:35 AM   #18893
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Dick Burwen's hybrid design for ADI is one of the most brilliant innovations I have ever seen. It was the BEGINNING of fully complementary push-pull, now used by Bob Cordell, me, and others. The added inductors were new! They reduced Gm at high frequencies, yet allowed LOW NOISE at working frequencies. Today, all they can use is resistors, which increases the input noise. The late, and competent, Deane Jensen did something similar with his trademark op amp design, that is still made today. Only the change to Toshiba quality input fets allowed the removal of the inductors and retaining the same performance.
In America, at the time, quality, not frugality, was regarded as most important. It may have been different in the URSS.
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Old 10th December 2011, 05:56 AM   #18894
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John Curl's Blowtorch preamplifier part II
The latest innovations are modeling of analog processes in digital reality, John!

No need to deal with real stubborn electronics, just push the buttons on touch-screen and enjoy!
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Old 10th December 2011, 06:30 AM   #18895
john curl is offline john curl  United States
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I don't think that you understand what I am saying, Wavebourn. Of course, your experience during the 60's and 70's, when we were developing these circuit topologies would be very different.
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Old 10th December 2011, 09:27 AM   #18896
jan.didden is offline jan.didden  Europe
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A nice glimpse of the importance of measurements conditions and specifications to distinguish your product from others.
Also a nice example of why 'identical specs' can still sound different.
Of course, the piece is written to promote the company's product but still interesting to read, I feel.

http://www.benchmarkmedia.com/discus...nce-Part-1.pdf

jan
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Old 10th December 2011, 09:40 AM   #18897
Trevor White is offline Trevor White  Australia
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Quote:
Originally Posted by john curl View Post
Yes, but degeneration does NOT have a 90 degree phase shift along with it!
so what if it has 90 degree phase shift !! It is still conditionally stable and the benefits of negative feedback still apply. The maths don't lie !!

regards
Trevor
 
Old 10th December 2011, 09:51 AM   #18898
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Originally Posted by ThorstenL View Post

Measurements of my gear are published in Stereophile, HiFi Critic, HiFi News and others. Please peruse these.



Ciao T
I am very sorry but I did not find any trusted measurements in Stereophile, only this short article:

AMR CD-777 Player/Processor | Stereophile.com

Would you mind posting a link to John Atkinson's measurements?
 
Old 10th December 2011, 11:08 AM   #18899
scott wurcer is online now scott wurcer  United States
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Quote:
Originally Posted by john curl View Post
That is irrelevant as Dick's ADI module was not made for audio. Later, he used an IC with a 100 Hz open loop bandwidth.
Dick wrote this (from his website)...

"The op amps Dick designed for his own hi-fi system started semiconductor manufacturer, Analog Devices, Inc in 1965."

There weren't any IC's for a while after that, but yes he later switched to them.

Did you ever hear one of these, I would love to see the schematic...

"At Krohn-Hite Corp. Dick designed the laboratory UF101 Ultra-Low distortion Power Amplifier. Using type 6550 output tubes in a multiple-loop,
high-feedback system, this amplifier, rated at 0.005% distortion was manufactured in small quantity for 20 years. "
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Last edited by scott wurcer; 10th December 2011 at 11:16 AM.
 
Old 10th December 2011, 12:05 PM   #18900
S.A.G. is offline S.A.G.  Italy
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Scott,

the Krohn-Hite amp schematic is available on Dick's site at:

http://burwenaudio.com/Krohn-Hite_UF-101.pdf


Regards

Giorgio
 

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