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SIT-3
SIT-3
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Old 13th April 2018, 10:26 AM   #11
nagini262 is offline nagini262  Viet Nam
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Congratulations, Nelson!
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Old 13th April 2018, 11:21 AM   #12
VladimirK is offline VladimirK  Uzbekistan
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Very smart implemented CCS load for SIT active device. I have tested output stage, with KP801G SIT as active device, and CCS was made as paralleled KP903A jFETs. Actually, it is, from very general look, the Ciuffolli-like stage, that is good for sound from my listening impressions.
Nice to see the NoGNFB design, but the DF=30 indicated seems difficult to achieve with SIT active device. I expected, that if output impedance is around 0,25 Ohms with power MOSFET in active device position, with SIT it should be higher.
In spite of this, I congratulate with further exploration of new solutions.
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Old 13th April 2018, 11:59 AM   #13
juma is offline juma  Germany
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Vladimir, what do you mean by "CCS load for SIT active device" ?
SIT-3 schematic shows a push-pull arrangement of N-channel SIT and P-channel MOSFET in the output stage.
SIT is depletion mode device and the MOSFET is an enhancement mode device and although they get same voltage on gates they act differently - when SIT's Id increases, the Id through MOSFET decreases (and vice versa) so that's push-pull operation...
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Last edited by juma; 13th April 2018 at 12:04 PM.
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Old 13th April 2018, 12:15 PM   #14
VladimirK is offline VladimirK  Uzbekistan
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I see, my fault, Nelson says explicitely it is push-pull. I could suppose that the diagram is not complete, and there could be something additional, making the P-MOSFET as CCS. But, with push-pull, we do not get advantages of Ciuffolli-like stage, and unclear how this is achieved:
"Besides the unusual DEF / SIT output stage, you might notice the inverted power supply, which dramatically reduces supply noise
seen by the SIT."
Influence of PS rail is greatly reduced in Ciuffolli-like stage.
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Old 13th April 2018, 12:42 PM   #15
juma is offline juma  Germany
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It's achieved by GND taking the role of positive rail so low-resistant SIT's Drain gets grounded, sees no ripple and the output stays undisturbed.
MOSFET Drain's impedance is a lot higher which makes it much more impervious to ripple from -V rail.
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Old 13th April 2018, 12:49 PM   #16
VladimirK is offline VladimirK  Uzbekistan
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Thanks, this explains to some extent. However, I insist, if current consumption of the stage from PS is variable under signal, the PS capacitors are in the signal chain. At that, the stage still could be improved soundwise, by approaching to class A Ciuffolli-like stage. Of course, IMHO.
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Old 13th April 2018, 12:51 PM   #17
Michael Rothacher is offline Michael Rothacher  United States
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The proof of the pudding is in the eating.
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Old 13th April 2018, 02:03 PM   #18
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally Posted by VladimirK View Post
Thanks, this explains to some extent. However, I insist, if current consumption of the stage from PS is variable under signal, the PS capacitors are in the signal chain. At that, the stage still could be improved soundwise, by approaching to class A Ciuffolli-like stage. Of course, IMHO.
there are so many forgotten things in electronics , invented in tube era , so there is a hardly Ciuffolli like stage

except if you think on inventive orientation of parallel resistors , with gold stripes on opposite ends

mad as hatter , as I am ........... it's miracle I didn't invented something like that



anything can be improved , but it would cost much more than SIT-3 price ;

and considering how much drek is around , already costing more .........

anyway , be our guest , and improve it
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Old 13th April 2018, 02:08 PM   #19
Michael Rothacher is offline Michael Rothacher  United States
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Also, it has been written elsewhere that the current source approach was indeed tried, but ultimately did not fair as well in listening tests as the DEP-ENH stage.
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Old 13th April 2018, 02:25 PM   #20
Zen Mod is offline Zen Mod  Serbia
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btw. as I posted before (in DEFiSIT thread) , this is wakoo current distribution

green - current through 8R speaker

blue - current through Papasit

red - current through mosfet
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