Beyond the J Fringe

[Nelson Pass]

I wrote a little article.

 

[chede]

Wow ! Biasing higher than Idss !

 

[RainfallSky]

Sleep is important!

 

[PKI]

Thank you Nelson!

 

[hifiZen]

Well, thank you Nelson. My little stash of K170's and J74's just got even more interesting (as if they weren't before)...

 

[Zen Mod]

Baaad Papa!!

 

[Zen Mod]

....... And sleep well at night.

that I do extremely well

 

[coolnose]

That sounds almost heretic after all those years chasing specific Idss grades...

 

[Zen Mod]

well, it would be revelation to find a way of using lesser xconductance JFets instead of higher xconductance ones, without additional gimmicks

but, that sort of miracles are ........ well, just wishes

 

[Blk Dynamite]

Looks like ill have to buy some lower grade Jfets before the prices go up from this article haha

 

[Botte]

Here is a link to the Erno Borbely Jfet article.

https://audioxpress.com/assets/upload/files/Erno BorbelyJFETs The New Frontier Part 1and 2.pdf

 

[Zen Mod]

here too: Erno Borbely site , zip file – for benefit of DIY community – Zen Mod Blog

 

[Rodeodave]

Switched-mode power supplies in class A, GR gerade jfets, biasing past Idss...just when you think you've seen it all...

(For the record, I don't think I have seen it all, it's just a saying )

 

[MEPER]

If my memory is correct the DiyAudio Store LSK170 /LSJ74 Grade A was the most expensive grade and not the cheapest?

Before I knew anything about Idss I just purchased some JFETs together with various kits (ACA, M2X etc.) just to have some for future projects and because the A-grade was the most expensive I thought that they were probaby the best and had less noise figures. Later I understood that GR and BL grade was the ones that was used to all projects and I wondered why the A-grade was so expensive and it probably was a mistake to get those

 

[elwood625]

The good news is that between Linear Systems and purchases of some Toshibas
the supply situation is improving.


Now I understand your comment.
If the lower Idss spec JFETS' operate so well under greater stress, does this mean the V grade JFET's might make a nice power amplifier without having to use one thousand in parallel?

 

[ItsAllInMyHead]

More to read and attempt to understand. Thank you, Nelson!

 

[DougL]

If the lower Idss spec JFETS' operate so well under greater stress, does this mean the V grade JFET's might make a nice power amplifier without having to use one thousand in parallel?

The essence of the Beast is to use a lot of small signal fets biased so they do not require additional heat sync. If the additional cost of the devices is offset by the elimination of the heatsink, you have a unique solution. Once you leave the SOA in free air, the project becomes less compelling.

I'm not saying it can't be done. I'm just pointing out the chalanges.

Just 2 pence.

 

[codyt]

This was a really helpful read. Clarified a few things that hadn’t sank in for me. Thanks NP! And you can send the surplus K370’s to me - I’ll make sure to get them to OPLDF

 

[twitchie]

+1

 

[Zen Mod]

no need for bloody intermediate between PL and OPLDF