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Old 14th May 2009, 12:44 PM   #1
paulb is offline paulb  Canada
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Default The Difference Engine Preamp

Grey Rollins (grollins here) has published a new preamp design but hasn't posted anything here about it. I thought I should.
http://www.enjoythemusic.com/diy/030...ce_engine1.htm
Looks like a nice differential gain stage, and Grey has pointed out a few areas for tweaking.
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Old 14th May 2009, 12:56 PM   #2
jam is offline jam  United States
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Looks like a non-cascoded version of Mr.Pass's UGS gain stage. I wonder if Mr.Pass was consulted..........he certainly was not given any credit for his patent or work on the topology.

Jam

P.S. Anyone have comments on the choice of output devices and their biasing?
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Old 15th May 2009, 11:12 PM   #3
mlloyd1 is offline mlloyd1  United States
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i'm certainly no master, but this looks a little different from my understanding at the guesses of what mr. pass does in his ugs - grey's bipolar second stage is a couple of diff amps ...

no comments on bias points yet - he is using loop feedback, so no need for a lot of heroics as far as device choices.

i'd be curious how well this scheme would work without loop feedback, using well matched devices, include source degeneration, bias some "better" output devices for peak hfe/ft, etc ...

the more i listen to charles hansen's stuff with no global feedback, the more i think he is on to something ...

mlloyd1
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Old 16th May 2009, 12:35 AM   #4
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Looks like a simplified UGS . . .


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Old 16th May 2009, 02:26 AM   #5
eLarson is offline eLarson  United States
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I thought the UGS-type circuit form UGS adventures thread involved some kind of current mirroring from one stage to the next. Am I "remembering" again?
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Old 16th May 2009, 04:02 AM   #6
mlloyd1 is offline mlloyd1  United States
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you're not alone - that's what i remember, too: the input jfets drove current mirrors.

maybe we both have that dreaded "memory" disease ...


mlloyd1

Quote:
Originally posted by eLarson
I thought the UGS-type circuit form UGS adventures thread involved some kind of current mirroring from one stage to the next. Am I "remembering" again?
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Old 16th May 2009, 08:41 AM   #7
h_a is offline h_a  Europe
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Gentlemen, let me give you a hint

The GR-25

Have fun, Hannes
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Old 16th May 2009, 09:00 AM   #8
Zen Mod is offline Zen Mod  Serbia
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core is simplest UGS , and overall - what's different - somewhat different position of tweaking pots ;
Papa's UGS schematics leaked already too many times to public , to be even remotely unknown .

anyway , UGS topology ( symmetrical in all 4 quadrants) is boiled water nowadays , and only big boyz know exactly who have more merits in that ;

what makes Papa's UGS unique is SUSY , and that's clearly evident in GR's stage .

but even SUSY is abused by many of us too many times .

one thing is certain - Papa like spoiled kids ....... confirmed numerous times ....

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Old 16th May 2009, 09:52 AM   #9
jam is offline jam  United States
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Default Duck Soup


Zen Mod is right.........it is all in the feedback arrangement and not anything to do with current mirrors (which happens to be implemented in Cheff's version).

I would have hoped that Mr.Pass would have been given credit for the topology by Grey and also let it be known that there has been a patent issued for said topology which is also happens to be Mr.Pass's intellectual property.

Mr.Pass has been kind enough to share many of his design ideas with us and we owe it to him to respect his property and request permission for it's use. Common decency and respect demands it.

Regards,
Jam
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Old 16th May 2009, 10:08 AM   #10
Zen Mod is offline Zen Mod  Serbia
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Default Re: Duck Soup

Quote:
Originally posted by jam

....
Mr.Pass has been kind enough to share many of his design ideas with us and we owe it to him to respect his property and request permission for it's use. Common decency and respect demands it.

Regards,
Jam

certainly , but I should not speculate is permission given in this case .... well, I should not even think about in this case .

besides fact that one article isn't exactly commercialization of concept/IP - GR is sort of Papa's adoptee , so we can leave that between them .....

am I wrong , as usual ....... ?
anyway - that's slippy terrain

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