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Old 8th December 2010, 10:40 AM   #1981
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The largest cap is 0.47uF. I have used aproximately the values that Burkhard Vogel uses in his BUVO. The feeback resistor under the Fets is under 1 Ohm.
I can ask Mr. Vogel if i can publish his diagram.
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Old 8th December 2010, 12:55 PM   #1982
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I had a really long phone call with Mr.Vogel and he gave me permission to publish his schematic. He also had no problems that i use some of his ideas
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File Type: jpg BUVO MC amp.jpg (292.0 KB, 326 views)
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Old 8th December 2010, 01:55 PM   #1983
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Hi Joachim,

do you also have his book? (The Sound of Silence)

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Old 8th December 2010, 01:57 PM   #1984
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Joachim

Tanks for you contributions
Audiofanatic is 100%

Is people like you that make people like me came here and push as to learn new things and better ourselves.


Al
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Old 8th December 2010, 02:24 PM   #1985
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Hi Pavel ! Yes, i have his book. It is indispensible. That guy has a sharp and clear mind.
Next year the second edition comes out and by what he told me on the phone the content is mouthwatering and it has 30% more pages.
He will even show low noise tube circuits ( he admitted that solid state does better in the noise department, but he tried hard to minimise it even with standart tubes ) and there is a chapter about pitfalls in FFT measurements and doing modern high resolution measurements in general.
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Old 8th December 2010, 02:27 PM   #1986
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Here is another early example ( i think end of 70th ) of the Fet plus Opamp theme. This time a Roberts circuit before he worked for Peavey.
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File Type: jpg roberts_preampphonomc.jpg (34.5 KB, 279 views)
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Old 8th December 2010, 02:31 PM   #1987
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Quote:
Originally Posted by Joachim Gerhard View Post
He will even show low noise tube circuits ( he admitted that solid state does better in the noise department, but he tried hard to minimise it even with standart tubes ) and there is a chapter about pitfalls in FFT measurements and doing modern high resolution measurements in general.
He is doing very well trying more with tubes also. While my JFET is 20dB better in noise and I can easily hear the more resolution and less THD, still my Valve Itch pulls a couple of suave musicality tricks in some areas that are hard to deny simply as euphonic colorations.
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Old 8th December 2010, 02:48 PM   #1988
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Transistors have other distortions that do not show up with static measurements like thermal distortion and even change of shape over current. The input capacitance of tubes is also much more benigh because you could say it is a vacuum capacitor whereas capacitance in J-Fets for example is highly unlinear even if the nominal value is small.
I do not want to open up a can of worms though. Heavy Feedback can kill a lot of this nonstatic distortion too and i an convinced that global NFB circuits can be made that sound very musical and charming. They just need the same loving attention that the open loop circuits get BUT they talk another language.
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Old 8th December 2010, 03:09 PM   #1989
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Have listened and compared phonos not only DIY but also commercial up to Boulder 2008 territory. Some things tubes do or JFETs do or BJTs do or OAs do, stamp a mark on all and each more or less is my long term impression.
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Old 8th December 2010, 03:23 PM   #1990
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Quote:
Originally Posted by Joachim Gerhard View Post
Transistors have other distortions that do not show up with static measurements like thermal distortion and even change of shape over current.
Hi Joachim,

this both is measurable. I suspect that many people like added low-order HD and IMD of several 0.01%, or a decreasing comb-shaped distortion. Some tests were made, but I would rather discuss it if I hopefully meet you once in Germany, that I visit every year.

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