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Old 20th June 2011, 02:02 AM   #101
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exactly .
ZM - Can you elaborate?
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Old 20th June 2011, 09:38 AM   #102
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Originally Posted by NYCOne View Post
ZM - Can you elaborate?
my lips are sealed

it seems , at least to me , in all Papa's projects - always is one detail (or spot ) in schematic which is sort of new or special or just different from common praxis in building electronic gadgets ......

even worse - sometimes he have wicked sense of humor - fact for M2 , written on 6moons site , by Papa :

Quote:
The bias circuits take a couple of minutes to fully charge but then they settle into high precision. The slow charge is how I avoid that precision from creating any sonic artifacts. The first ones I made took a full 2 minutes before any sound came out at all. You can imagine the messages I got. I should have put something in the manual about it. Something like that's the tubes warming up! Also, as the M2 biases up, the output stage goes from class B to class AB to class A. What you get to listen to is the character of each without feedback. Ontogeny recapitulates philogeny.
based on what I know about that circuit ( I'm not saying that I know everything ) , that's half true , half witty .

so - speaking shortly - biasing of J2 is where humor resides , besides elegance ; genius is used for laying several small puzzles in one greater than sum of puzzles

your question was rhetorical , so you are given with adequate answer ....
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Old 20th June 2011, 11:00 AM   #103
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It seems the V sources main job is to make sure the signal the two fets are seeing is balanced. Setting this value properly may be the key.

The Tube CAD Journal,SRPP Optimal Rak Value 3

This is just a guess.
It seems odd that Broskie gave the best description of the SRPP, but seems to not think about using a pentode up top.

Last edited by buzzforb; 20th June 2011 at 11:03 AM.
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Old 20th June 2011, 02:19 PM   #104
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current/voltage contribution between two "halves" of Aleph/SRPP/Mu output stage is matter of constructor's choice ......... or simply tweaking it to smallest amount of distortion vs. planned load

when you're going to pentode on top of triode , result is having more of ideal CCS as load ;

that's path away from having both halves behaving as equally contributing in voltage/current domain , for what you need both elements with finite internal impedance
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Last edited by Zen Mod; 20th June 2011 at 02:22 PM.
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Old 20th June 2011, 03:08 PM   #105
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Quote:
Originally Posted by Zen Mod View Post
my lips are sealed

it seems , at least to me , in all Papa's projects - always is one detail (or spot ) in schematic which is sort of new or special or just different from common praxis in building electronic gadgets ......

even worse - sometimes he have wicked sense of humor - fact for M2 , written on 6moons site , by Papa :



based on what I know about that circuit ( I'm not saying that I know everything ) , that's half true , half witty .

so - speaking shortly - biasing of J2 is where humor resides , besides elegance ; genius is used for laying several small puzzles in one greater than sum of puzzles

your question was rhetorical , so you are given with adequate answer ....
I wasn't rhetorical. If you're worried about NP, maybe you can explain how Broskie's article relates to NP's work in general.
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Old 20th June 2011, 07:54 PM   #106
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Quote:
Originally Posted by Zen Mod View Post
current/voltage contribution between two "halves" of Aleph/SRPP/Mu output stage is matter of constructor's choice ......... or simply tweaking it to smallest amount of distortion vs. planned load

when you're going to pentode on top of triode , result is having more of ideal CCS as load ;

that's path away from having both halves behaving as equally contributing in voltage/current domain , for what you need both elements with finite internal impedance
So for PP you need two triodes with clever Vsouce, and pentode up top gives you a nice SE design and moves away from PP.

Magic is manipulating the internal resistance?
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Old 20th June 2011, 08:40 PM   #107
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Originally Posted by buzzforb View Post
.......

Magic is manipulating the internal resistance?
internal resistance - xconductance - gain , whatever .....

it all depends for what you are looking ;

maybe gain is most comprehensive term
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Old 20th June 2011, 08:43 PM   #108
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Thank you. I believe I see what is needed. I have some reading to do.
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Old 20th June 2011, 10:04 PM   #109
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Consider the two power resistors going from the Source of the CS to the
Drain of the primary gain device. The voltage across these resistors and
their added resistance sets the DC bias of the current source. Where you
tap between them sets the gain. You could easily imagine a string of 0.1
ohm resistors, 10 in series forming 1 ohm but the output to the load is
tapped arbitrarily. Then you can adjust to your heart's content either for
low distortion or a particular ratio of 2nd to 3rd harmonic.

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Old 20th June 2011, 11:07 PM   #110
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The J2 has more gain and runs hotter (higher bias?). As I've noticed in preamps, higher gain and higher bias often correlate with greater weightiness and sweetness.

I found this before seeing the post above.

Also there is info in F3 Help thread about affect of increased bias and voltage and transconductance and how this affects capacitance.

Thank you Nelson. I do not have the fets for the J2, but hope to explore the topology for a higher power SE amp. I want to play with both mu and cascode setup from F3 perhaps combining the two. Hope to get Fets for J2 after exploration of this amp. Interesting how Broskie moves through the possibilities of the mu follower being possibly PP or SE.
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