Spice models for SK246/SJ103 anyone? - diyAudio
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Old 19th November 2008, 11:27 AM   #1
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Default Spice models for SK246/SJ103 anyone?

Does anyone have spice models for these JFETs?

I haven't given Borbely much thought before, just recently read his articles. His designs look fantastic. Now I want to explore the sound of cascoding JFETs with other JFETs.
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Old 19th November 2008, 12:12 PM   #2
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Here you go :

.model J2sj103 PJF(Beta=2.197m Rs=76.76 Rd=76.76 Betatce=-.5 Lambda=735.3u
+ Vto=-2.037 Vtotc=-2.5m Cgd=18.95p M=.5045 Pb=.3905 Fc=.5
+ Cgs=17.02p Isr=38.48f Nr=2 Is=3.848f N=1 Xti=3 Alpha=10u Vk=100
+ Kf=1E-18 Af=1)


.model J2sk246 NJF(Beta=1.07m Rs=56.76 Rd=56.76 Betatce=-.5 Lambda=2.8m
+ Vto=-2.638 Vtotc=-2.5m Cgd=10.38p M=.4373 Pb=.3905 Fc=.5
+ Cgs=6.043p Isr=112.8p Nr=2 Is=11.28p N=1 Xti=3 Alpha=10u Vk=100
+ Kf=1E-18 Af=1)


Cant guarantee accuracy though, they were from a japanese audio site.
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Old 19th November 2008, 12:39 PM   #3
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2N series Fets like 2SK246/ 2SJ103 ?
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Old 19th November 2008, 12:41 PM   #4
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Thank you very much. I'll try them tonight.
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Old 19th November 2008, 01:52 PM   #5
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Nelson,
Why do you need them? You are the right man to empirically determine the biasing points, which has not yet been done reliably.
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Old 19th November 2008, 02:18 PM   #6
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Quote:
Originally posted by Lumba Ogir
Nelson,
Why do you need them? You are the right man to empirically determine the biasing points, which has not yet been done reliably.


If you hate simulators even for bias calculations, what about a pencil and a piece of paper? But then I suppose not even pencils and paper are allowed in you empirical world.
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Old 19th November 2008, 03:40 PM   #7
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Quote:
Originally posted by Lumba Ogir
Nelson,
Why do you need them? You are the right man to empirically determine the biasing points, which has not yet been done reliably.
Before I learnt LTSpice I worked by trial and error. It's the sound that matters, not figures, so I guess you're right in a way. Some changes can be heard but not seen in simulation, eg transistors sound different from each other yet simulate exactly the same, current mirrors degrade the sound yet gives a perfect simulation, CFP input sounds very good but doesn't simulate any better etc. A lot of changes can be seen in LTSpice but not be heard.

From a DC perspective LTSpice has been very precise, and a circuit that's unstable in a simulator will most definately be unstable IRL. So simulating is quite helpful.

Pencil and paper is absolutely useless to me, since I can't calculate anything except the basics. I was about to learn electronics the proper way, but now that I've found LTSpice I'm far to lazy to do that.
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Old 19th November 2008, 04:12 PM   #8
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Quote:
Originally posted by nelsonvandal
A lot of changes can be seen in LTSpice but not be heard.
Actually you can...well sort of...I've just managed to listen 14 sec .wav sample from James Brown tune "I feel good" coming out from my virtual folded cascade headamp thru Windows Media Player
http://www.ltspicelabs.blogspot.com/
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Old 19th November 2008, 04:54 PM   #9
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Old 19th November 2008, 05:08 PM   #10
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Nelson,
what I meant was that you could by listening try to decide primarily optimal Ids, Vds and Rs values.
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