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Old 4th April 2007, 12:47 AM   #221
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Yeah... the 330/105's were not graded although 170/74BL's were. B&D E has them in BL, GR and V-F grades. Might take a bu$hel of em to get matches approaching Pass production standards. Group buy anyone?
-Mal
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Old 4th April 2007, 01:29 AM   #222
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Quote:
Originally posted by GRollins


Hint #2: Parallel lower Idss devices for the input complementary follower. Don't have BL? Use two or three GR, or whatever.

My interpretation is that f4 input jfets need no current.
I believe that Papa must be knowing what GR, BL and V mean.
Nevertheless, Papa's circuit says nothing about them.

Papa was half sleeping when he was writing down the manual?
Or, was half lost himself in a reverie?


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Old 4th April 2007, 01:35 AM   #223
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Quote:
Originally posted by Babowana




I believe that Papa must be knowing what GR, BL and V mean.


I think that's secret jfet language
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Old 4th April 2007, 01:38 AM   #224
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Quote:
Originally posted by Malotron
Yeah... the 330/105's were not graded although 170/74BL's were. B&D E has them in BL, GR and V-F grades. Might take a bu$hel of em to get matches approaching Pass production standards. Group buy anyone?
-Mal

Yes i'm interested. I'm currently working on a set of boards. Going to be a long night working with eagle tonight
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Old 4th April 2007, 01:50 AM   #225
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Quote:
Originally posted by mpmarino


I think that's secret jfet language

No secret.

After having opened the door to the maze, Papa is just watching how kids approach to the final solution . . . ^^


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Old 4th April 2007, 04:32 AM   #226
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Quote:
Originally posted by EUVL

-Post #233
> I think the j-fets has a lot to do with the fine sound of the F4.

I dare to disagree.

IMHO, I think it has more to do with the bandwidth, AND also that it has no global feedback. I have similar experience with preamps on both issues.

-Post #253
> I think that the jfets are doing just one thing--providing high input impedance.

And also a low output impedance to ensure high bandwidth for the power MOSFET follower.

Patrick



JFETs
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Old 4th April 2007, 05:02 AM   #227
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> Nevertheless, Papa's circuit says nothing about them.

He mentioned somewhere in the thread 4mA bias, so BL.

If you guys believe in JFET magics, then don't use MOSFETs for the output stage. Find yourselves some Sony power JFETs, or design a pure N-JFET follower for the output stage using cascoded LU1014s.


Patrick
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Old 4th April 2007, 05:04 AM   #228
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Quote:
Originally posted by EUVL
> Nevertheless, Papa's circuit says nothing about them.

He mentioned somewhere in the thread 4mA bias, so BL.

If you guys believe in JFET magics, then don't use MOSFETs for the output stage. Find yourselves some Sony power JFETs, or design a pure N-JFET follower for the output stage using cascoded LU1014s.


Patrick

Patrick, is there a big difference in sound with J-Fets and normal fets ? my dad always said if i wanted some good sound to try Jfet amps..

What is your thought about this comment ?

Jase
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Old 4th April 2007, 05:25 AM   #229
EUVL is offline EUVL  Europe
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I agree. But that is purely my personal opinion.
I also prefer SE amps to complementary.

So that is why I am not building the F4.
I think I have given enough hints.

A possible solution for a follower using LU1014s is the circuit I published in the MOSFET follower headamp thread. You only need to change the source resistor to values similar to ZV9, and raise the supply rails by 3V or so.

And of course you need minimum 6, probably 12x LU1014s if you are not using push-pull.


Patrick
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Old 4th April 2007, 06:11 AM   #230
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Quote:
Originally posted by EUVL


He mentioned somewhere in the thread 4mA bias, so BL.

Yes, I know.

In post #228, Papa says,
"They run 5ma, which makes them BL."


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