Spice models for SK246/SJ103 anyone?

[nelsonvandal]

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.

 

[homemodder]

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.

 

[stinius]

http://www.diyaudio.com/forums/showthread.php?threadid=80546

 

[nelsonvandal]

Thank you very much. I'll try them tonight.

 

[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.

 

[syn08]

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.

 

[nelsonvandal]

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.

 

[aparatusonitus]

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/

 

[homemodder]

 

[Lumba Ogir]

Nelson,
what I meant was that you could by listening try to decide primarily optimal Ids, Vds and Rs values.

 

[homemodder]

Lumba and Nelson, sorry I should have quoted those grins to aparatusonitus comment. They were not directed at your discussion at all so I hope no offense taken. Seeing that one can listen to your ltspice circuit just brought a smile to my face.

 

[Lumba Ogir]

homemodder,

I hope no offense taken.

None at all!

 

[aparatusonitus]

Seeing that one can listen to your ltspice circuit just brought a smile to my face.

Oh, I forgot to mention that it sound pretty good for a toy if you limit output from virtual amp at 2Vpp to avoid overload in WMP that is...go figure.