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Old 6th September 2012, 02:33 PM   #1431
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even if he's having that in FW Cousine
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Old 6th September 2012, 02:55 PM   #1432
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Originally, Nelson used a different transformer from the Jensen. Could this explain the numbers?

Last edited by bobodioulasso; 6th September 2012 at 02:57 PM.
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Old 6th September 2012, 02:56 PM   #1433
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Quote:
Originally Posted by lhquam View Post
I am still stumped by Nelson Pass post #435. Both my prototype build and simulations show increased THD at both frequency extremes, but most at high frequencies. In the simulations, the interwinding capacitances are a major contributor to the high frequency 2nd order harmonic. Below are THD vs Frequency sweeps for open-loop, Gain=10 and Gain=5, and my circuit schematic.

If Nelson's results are significantly different from these, then his circuit has some tricks that I haven't figured out.
I sense emphasis on the work of Mr. Pass. Clearly you care and it is a challenge to refine Conceptual F6. Your published work is the proverbial bird at hand; while that of Mr. Pass is another bird perched on a distant tree! It'll come to feed off your hand in good time. It'll get hungry!

What do we know today about the work of Mr. Pass on F6? Mumm is the word.

Last edited by Antoinel; 6th September 2012 at 03:06 PM.
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Old 6th September 2012, 03:09 PM   #1434
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Quote:
Originally Posted by bobodioulasso View Post
Originally, Nelson used a different transformer from the Jensen. Could this explain the numbers?
Quote:
Originally Posted by Nelson Pass View Post
........ JT123-FLPCH is still available.

This is obviously one of those days where the cosmos is playing with me.
.....

I'm understanding that as talk about originally chosen type
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Old 6th September 2012, 03:39 PM   #1435
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Quote:
Originally Posted by kasey197 View Post
l. I'll check the THD at 10 and 20khz tonight and let you know ...
fwiw, in case it helps you ... at 1w, open loop, rs=0.47, 1khz=0.017%, 10khz=0.12%, 20khz=0.38% ..... Good luck ......
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Old 6th September 2012, 03:53 PM   #1436
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Quote:
Originally Posted by Zen Mod View Post
I'm understanding that as talk about originally chosen type
That was misunderstanding from me.
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Old 6th September 2012, 05:09 PM   #1437
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lhquam, kasey197,triode_al, and others. Would you consider laying the foundation and/or simulating the output stage of Conceptual F6 by using SIT devices instead of JFETs? You'll get an amp with an established triode-like soundprint [according to Pass, Rothacher and others]; albeit with an output impedance of hopefully <1 Ohm after using loop feedback. This Zo is much lower that is currently achieved and available. This is a Burning Amp candidate for the upcoming Festival. A Futterman-style SIT amp which will stand out in the crowd!

lhquam: Will your PCB [arriving tomorrow] accept a SIT [KD82] modification? You asked in a past post whether Mr. Pass has achieved a vac-tube sound with his F6. This approach is potentially the best answer.

Last edited by Antoinel; 6th September 2012 at 05:22 PM.
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Old 6th September 2012, 05:24 PM   #1438
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I do not know the circuit modifications that might be needed. Can you point me to details?

Quote:
Originally Posted by Antoinel View Post
lhquam, kasey197,triode_al, and others. Would you consider laying the foundation and/or simulating the output stage of Conceptual F6 by using SIT devices instead of JFETs? You'll get an amp with an established triode-like soundprint [according to Pass, Rothacher and others]; albeit with an output impedance of hopefully <1 Ohm after using loop feedback. This Zo is much lower that is currently achieved and available. This is a Burning Amp candidate for the upcoming Festival. A Futterman-style SIT amp!

lhquam: Will your PCB [arriving tomorrow] accept a SIT [KD82] modification? You asked in a past post whether Mr. Pass has achieved a vac-tube sound with his F6. This approach is potentially the best answer.
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Old 6th September 2012, 05:29 PM   #1439
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Finally, Nelson posted the complete and detailled article about the F6!

FIRST WATT ARTICLES

Boahhh

P.S.
You see nothing new? Maybe the cache? Just press F6 !

Last edited by Franz Gysi; 6th September 2012 at 05:43 PM.
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Old 6th September 2012, 05:51 PM   #1440
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Originally Posted by lhquam View Post
I do not know the circuit modifications that might be needed. Can you point me to details?
lhquam: I have faith in your ability and others to sim and build. I am just making connections as an observer which I hope are useful. In post#921; banat showed a vacuum tube output stage in a schematic like that of Conceptual F6. A vac tube and a SIT are depletion-style devices. Guidance forward is therein. Also, the articles by Michael Rothacher entitled L'Amp: A simple SIT Amp; Parts One and Deux. They shows the characteristic curves of KD82 [measured by Rothacher], and its proper biasing. I believe that Mr. Pass has a propriatory stash [how large?] of SIT devices which are not for sale. He may be already pursuing this approach.

You're doing great with your work with JFETs. Hopefully you and others pursue SIT in addition to JFET.

Last edited by Antoinel; 6th September 2012 at 06:00 PM.
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