The Difference Engine Preamp

[paulb]

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.

[jam]

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?

[mlloyd1]

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

[Babowana]

Looks like a simplified UGS . . .

[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?

[mlloyd1]

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

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?

[h_a]

Gentlemen, let me give you a hint

The GR-25

Have fun, Hannes

[Zen Mod]

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 ....

[jam]

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

[Zen Mod]

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