Krazy JFET-cascoded Pass BOSOZ

[jh6you]

Krazy JFET-cascoded Pass SOBOZ

Hi

I am trying to build this.
My most concern is how to set up the gain of about 14-20dB.

Appreciate any comment, advice, or criticism . . . plz . . .

Regards
jh

 

[wuffwaff]

Hi,

gain is set through the drain resistors and the chosen fets.

gm = 2xIdss/Vp

Gain = gm x Rdrain

I don´t have any data on the J310 so you´ll have to calculate it for yourself.

What is the resistor between output and input?

William

 

[jh6you]

Thanks, William

Well noted.
Attached is a brief data about J310 I prepared.
I am thinking the Rd of 1K.

The minimum Gfs of J310 is 0.008mhos.
Min. voltage gain A = Gfs x Rd = 0.008 x 1000 = 8 (18dB)
The maximum Gfs is 0.018mhos.
Max. A = 0.018 x 1000 = 18 (25dB)

Hmmm . . . the gain would be between 18-25dB.

The resistor betweem the output and the input is my "uncertainty." I was unsure about the voltage gain of this concept so that I put my "uncertainty" there in case I need a negative feedback. I will remove it and repost the circuit.

Any other comments . . . ?

Regards
jh

 

[jh6you]

Attached is Rev.1

Help me with your comments . . . plz . . .

Regards
jh

 

[jh6you]

I read data sheet again.
And, re-estimated the voltage gain.

Min. A = 0.011 x 1000 = 11 (20dB)
Max. A = 0.013 x 1000 = 13 (22dB)

Hmm . . . 20-22dB . . .

I wonder if this way of estimation is correct.
So far, nobody seems intersted in or has no time . . .

Regards
jh

 

[Zen Mod]

I dunno....
now I'm breakin' and bangin' my head with Aleph J
besides-I'm greenhorn....

 

[jh6you]

I see . . .
Following this project, I go with JFET-cascoded F1 . . .



Regards
jh

Where is my power JFET . . .
Where are they . . .

 

[Flemming J P]

I see . . .
Following this project, I go with JFET-cascoded F1 . . .

Could you please hurry up

I was thinking about the same thing, but due my limited understanding of the world and more specificly mofsets/jfets I need a complete ciruit.

 

[jh6you]

Hurry up . . . ?
The music from F1 is already !!!
I do not have the power JFET . . .
Mmm . . . I could create a new thread with a conceptual darwing . . . if the master does not mind . . .

I donnu MOSFET/JFET either, but we are lucky with good supports here . . .

Back to the subject, I am going to try the shown Krazy, 10 days later when I return back to the exciting hell from the boring heaven I am staying now. Still have time for your positive or negative feedbacks.

Regards
jh

 

[Flemming J P]

Ok ok, I will build the F1.

I am still waiting for my heatsinks for it, but I should get them soon. All the other parts are already waiting for me on my work table.

I'm sure it will be much better than my gainclones, but I also know that I will have to change it to JFet F1 (or what ever it is goning to be called) when I can.

If one only had the time to learn, but I have so many other projects and a full time job to care of.

Good luck with the Krazy.

 

[lohk]

I cannot evalute if it works up to the expectations, but it looks quite interesting. I also do not know if NP officially did something like that already, but I thing you are quite close to the momentary developments at Passlabs. And you have introduced a new name, much better than all those acronyms and number combinations.
Go ahead!

 

[steenoe]

"The Krazy"
Catchy name Sounds like a preamp for us DIYer's
Looking forward for your results, JH

Steen

 

[Zen Mod]

"The Krazy"
Catchy name Sounds like a preamp for us DIYer's
Looking forward for your results, JH

Steen

steen-stop right now!
you have already enough preamps!

 

[steenoe]

steen-stop right now!

I guess you are right
But I want my share of fun Even if I had the worlds greatest system, I would still build stuff Cant help it

Steen

 

[jh6you]

Alohka and Steen, thanks for encouragement . . . ^^
This is limited only to pure hobbists . . . but fully open to Nelson


Regards
jh

PS.
Audiofreak, can you change SOBOZ to BOSOZ in the title? It was a misprint . . . Tks.

 

[jh6you]

I changed sizes of resistors . . .
Errr . . . Rd is 1.5K//5K//10K = 1K . . .
Soo . . . the voltage gain remains around 20-22dB, approximately . . .

My present status:
My hope at the end: and
Will see . . .

Regards
jh

---
I feel very sorry whenever I misprint the names of Nelson's children, always with BOSOZ. The title of this thread . . . SOBOZ . . .
Audiofreak, can you kindly correct it into BOSOZ?

 

[Nelson Pass]

In the cheap advice department, I have usually found it
necessary to put a hundred ohms or so in series with
the outputs to insure that no system oscillation can
occur. There are occasions where even if this circuit
doesn't oscillate, the circuits following might get unhappy.

 

[jh6you]

. . .

Even you do misspell . . . It's Chip Advice Department . . . ^^
Thank you very much . . . I do not want to make my love, F1, unhappy . . .

Regards
jH

 

[jh6you]

Including Neson's expensive advice, and asking harmonization with Krazy PSU, I will build this way and see how it works.

Regards
jh

 

[john-china]

output impedance

hello jh6you, happy chinese new year to you.


output impedance of your circut will be higher than 1.5K
will it be a problem?
i always think a pre amplifier's out impedance should be less than 1K. or you will reconsider to build a special power amplifier with higher input impedance.