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Old 9th October 2012, 05:15 PM   #181
Salas is offline Salas  Greece
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Its the spice JFET models don't care maybe. I have read many times they are not the most elaborate in conception VS BJT models for instance. Thanks for the welcome, I wish I knew how to repair a TV myself. Me just a simple audio circuits hobbyist, messing up all the time.
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Old 9th October 2012, 05:29 PM   #182
popilin is offline popilin  Argentina
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Quote:
Originally Posted by Salas View Post
Its the spice JFET models don't care maybe. I have read many times they are not the most elaborate in conception VS BJT models for instance. Thanks for the welcome, I wish I knew how to repair a TV myself. Me just a simple audio circuits hobbyist, messing up all the time.
You are very humble, typical of those who truly know.

Just seeing your designs can be seen clearly.

BTW, I am designing a 650 V PSU, I hope you don't mind if yours inspire me.
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Last edited by popilin; 9th October 2012 at 05:34 PM.
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Old 9th October 2012, 06:16 PM   #183
Salas is offline Salas  Greece
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Maybe a J309 for cascode's top? How that fairs in your sim?
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Old 9th October 2012, 07:20 PM   #184
popilin is offline popilin  Argentina
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Quote:
Originally Posted by Salas View Post
Maybe a J309 for cascode's top? How that fairs in your sim?
Thanks for your advice.
According to the datasheet, the J309 looks good, I must only find the mathematical model.

I must confess that I hate Fairchild's bureaucracy whenever I seek any model.

As I have, I will publish the results.
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Last edited by popilin; 9th October 2012 at 07:49 PM.
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Old 9th October 2012, 08:45 PM   #185
Salas is offline Salas  Greece
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.model J109 NJF(Beta=12.42m Betatce=-.5 Rd=1 Rs=1 Lambda=35m Vto=-3.002
+ Vtotc=-2.5m Is=533.7f Isr=5.174p N=1 Nr=2 Xti=3 Alpha=152.8u
+ Vk=111.9 Cgd=47.7p M=.4283 Pb=1 Fc=.5 Cgs=47.7p Kf=169.9E-18
+ Af=1)
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Old 9th October 2012, 10:55 PM   #186
popilin is offline popilin  Argentina
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Hi Salas

I found a model from Philips, thanks a lot, I will try your model soon.
J309 is a very clever choice, distortion remains the same because of +B, but now, noise is lower.
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Old 9th October 2012, 11:07 PM   #187
Salas is offline Salas  Greece
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Old 3rd May 2014, 05:24 PM   #188
disco is offline disco  Netherlands
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Johan, did you ever build this setup?
What about exchanging a 25Kohm pot for R11?
Would the extra capacitance (because of the pot) lower residual noise even more?
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Old 3rd May 2014, 07:01 PM   #189
dady is offline dady  Balearic Islands
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Dear Popilin, How are you my dearest friend?
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Old 3rd May 2014, 07:34 PM   #190
popilin is offline popilin  Argentina
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Quote:
Originally Posted by disco View Post
Johan, did you ever build this setup?
No, I didn't, because it is a thought experiment, and here is impossible to obtain good JFETs, only fakes.

However I did the normal SRPP, without JFETs, and it sounds amazingly transparent, no need sand after all.

Quote:
Originally Posted by disco View Post
What about exchanging a 25Kohm pot for R11?
Not the best place to put a pot, because of output impedance and frequency roll off, a better place should be at the input, before R5. IMHO

Quote:
Originally Posted by disco View Post
Would the extra capacitance (because of the pot) lower residual noise even more?
I don't understand what do you mean, but, the best solution I found regarding noise, frequency response and phase shift is

Low gain SRPP => 100K pot => SLCF

Same approach here

The volume pot - The hidden villain of preamp
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