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Old 15th November 2005, 09:42 PM   #11
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Quote:
Originally posted by Nelson Pass
There is only a positive rail and ground in the original, in
case this is a point of confusion.

Thank you, I think I have the original circuit figured out pretty well, but I was trying to make a bipolar power supply version as well.

Cheers!
Russ
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Old 15th November 2005, 10:04 PM   #12
Zen Mod is offline Zen Mod  Serbia
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gentlemans-my modest (and verry clever ) proposal is that we merge this in just one thread......not sorta Krell clone thread but.....

besides -even if NS 10 is JUST preamp ,I think that this preamp deserves clonnin' thread ........hehe

just notice- I always have strange way in making system for particular room-I choose first speakers for room,then preamp,and then amp ;
Am I weird or what -preamps are offten bigger fetish for me than amps ,mebbe just because I always have more than one good amp .....
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Old 16th November 2005, 01:12 AM   #13
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Hi, Russ,

About the schematic in post #5 :
- If you use single supply (only + and gnd), this schematic is lacking the pull up section (R5,R6,C4 in NP's sch). If the Q1's base voltage is not defined (near middlle of the rail, usually), I'm afraid the whole thing won't work.
-RBS (of Q3) is not attached to ground, but in series with the base (ordinary base stopper configuration)

For using symmetrical power supply, then your schematic in post#5 can have the input section like that (without R5,R6,C4),
-R13 is connected to GND (to define 0 point for Q1)
-R3 is connected to -rail (adjusted in value until you get 0V on output),
-The end of C3 is also connected to GND
-R9 is connected to -rail
-R11 connected to GND

I don't advise the following, but I do this : I pick up transistors with lower gain (HFE) in position of Q2 and Q3. I use MPSA42 and MPSA92 there. I don't use R3. If you trace oscilation in the whole cct, you can put pF capacitor between B-C of Q1.

PS :

Mr.Pass, is it alright to make this schematic using symmetrical power supply? I hope I'm not Hi-Jacking your NS10, it is just because I don't have the original component values
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Old 16th November 2005, 01:30 AM   #14
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Quote:
Originally posted by lumanauw
Hi, Russ,
For using symmetrical power supply, then your schematic in post#5 can have the input section like that (without R5,R6,C4),
-R13 is connected to GND (to define 0 point for Q1)
-R3 is connected to -rail (adjusted in value until you get 0V on output),
-The end of C3 is also connected to GND
-R9 is connected to -rail
-R11 connected to GND

I don't advise the following, but I do this : I pick up transistors with lower gain (HFE) in position of Q2 and Q3. I use MPSA42 and MPSA92 there. I don't use R3. If you trace oscilation in the whole cct, you can put pF capacitor between B-C of Q1.

Thanks!

My question, and that schematic is for dual supply (bipolar).

You have helped me greatly.

Cheers!
Russ
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Old 16th November 2005, 06:07 AM   #15
steenoe is offline steenoe  Denmark
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Good idea to merge the thread's, Choky
Take a look at this link, those old model numbers really get me sentimental
http://www.threshold-audio.com/discontinued.html

Steen.
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Old 16th November 2005, 01:25 PM   #16
Zen Mod is offline Zen Mod  Serbia
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slightly (?!!) off topic :
did ya see :
Otala's Silver?

and

µPA75V and µPA74V data

?

I'm pretty hopelles regarding pinouts of these lil' Upa74 and 75.....

time is what I don't have enough right now....... Googlin doesn't help - I have data,but pinout is still missing.....
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Old 16th November 2005, 02:25 PM   #17
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Default Biplolar Layout

here is an attempt at a single side bipolar layout, mostly just so I can build a prototype:
Attached Images
File Type: png pre.png (42.0 KB, 1574 views)
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Old 16th November 2005, 02:28 PM   #18
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Here is the schematic:
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File Type: png presch.png (13.7 KB, 1722 views)
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Old 16th November 2005, 02:53 PM   #19
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Hi, Russ,

What's the purpose of C4 (connected B-E)?
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Old 16th November 2005, 03:00 PM   #20
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Oops!

Thanks, that was a mistake. It was meant to be between B-C of Q1 as you earlier suggested as optional to control oscillation.

Corrected schematic:
Attached Images
File Type: png presch.png (13.7 KB, 1578 views)
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