Author Topic: For those who are designing with (J/MOS)FETs... (Read 3346 times)

sismofyt · « **on:** June 25, 2004, 11:47:59 AM »

This is a really good article by Erno Borbely, a well known and very good designer.

Check the FET matching (Figure 5) & the quad JFET (Figure

. I'm currently experiementing with that circuit :wink:

www.borbelyaudio.com/ae599bor.pdf

Article 2

www.borbelyaudio.com/ae699bor.pdf

All FET Line Amp:

www.borbelyaudio.com/borb502.pdf

He is also selling those really hard to get JFETs and other high quality audio transistors at very reasonable prices. For 50% more he'll do matching:

www.borbelyaudio.com/index21.htm

And his kits (10% off this month!):

www.borbelyaudio.com/index22.htm

There's a very interesting mic preamp too! Haven't tried it, but I have build several of his projetcs in the past. Very high quality :thumb:

Some cool articles (tubes too :cool: ):

www.borbelyaudio.com/index15.htm

Nelson Pass is another wellknown FET enthusiast:

www.passdiy.com & www.passlabs.com

His Bride of Zen could perhaps be used in the Forssell Opto Comp:

www.passdiy.com/pdf/brideofzen.pdf

His thoughts on DIY opamps:

www.passdiy.com/pdf/diyopamp.pdf

His forum:

www.diyaudio.com/forums/forumdisplay.php?s=&forumid=8

Maybe Fred Forssell has something to ad being a FET fan too :cool: :grin:

Svart · « **Reply #1 on:** June 25, 2004, 12:01:00 PM »

WOW :shock: they are proud of those parts... I love fets too, they are good with steak sauce..

sismofyt · « **Reply #2 on:** June 25, 2004, 12:03:58 PM »

:green:

(One Pass' great amps, btw)

chrissugar · « **Reply #3 on:** June 25, 2004, 01:39:31 PM »

The Forssell, Borbely, Pass articles about opamps and buffers are my favourites. I love FETs and their sound.
I bought tons [ok just some hundreds] of 2SK389, 2SJ74, 2SK170GR and 2SK170BL in the last few month. It cost me a fortune.
Should I buy more to prove that I love them? :green:

chrissugar

sismofyt · « **Reply #4 on:** June 25, 2004, 01:44:01 PM »

I'm listening to the Zen right now :wink: You can get free samples from www.InterFET.com They make a nice dual one.. :thumb:

sismofet

Winston O'Boogie · « **Reply #5 on:** June 25, 2004, 02:32:20 PM »

sismofyt · « **Reply #6 on:** June 25, 2004, 02:39:50 PM »

Nice info John. I tend to stick with K170/J74s also because I bought a sh*tload too :green:

What do mean putting some filtering on the lower arm? I can't picture that in my head :?

I'll bet in 25-30 years when there's isn't a decent dicreete device being made any more (but you can get a NASA space computer on a chip running @ 3,3V) those JFETs and similar BJTs are demanding good prices.

Lord knows what a NE5532 could be worth when I'm 64?

Winston O'Boogie · « **Reply #7 on:** June 25, 2004, 02:57:12 PM »

sismofyt · « **Reply #8 on:** June 25, 2004, 03:06:17 PM »

Ohh yeah, I had it sorta backwards, thanks :thumb: Ernos circuits do tend to get complex and it was very difficult for me to make his killer (hifi) preamp some ten years ago. But it did surely beat my Threshold FET 10 which did cost a fortune back then.. those were the dayz.. now I just use a passive pot :green:

Pass' circuits are the opposite, as simple as it possibly can get. I like that. Simplicity rules :cool:

chrissugar · « **Reply #9 on:** June 25, 2004, 03:26:55 PM »

Ok,I have to confess.
I built 40 jfet opamps based on Freds paper and I'm in love with them.
Since autumn 2003 most of them work as preamps [in combination with LUNDAHLs] and I have some nice sounding recordings [used them on three albums].
I had the intention to build the opamps almost three years ago and found some 2SK170 and 2SJ74s then at a good price but after that I did not find any of these FETS at a reasonable price. Since last year I started to buy them in larger quantities because I'm afraid they will disapear from the market. The waiting time for the 2SJ74 was eight weeks. :shock:

chrissugar

P.S. How much is a resonable price for the 2SJ and 2SJ , I'm just curious if I bought them at a good price or not.

Winston O'Boogie · « **Reply #10 on:** June 25, 2004, 03:57:41 PM »

dmlandrum · « **Reply #11 on:** June 25, 2004, 04:06:54 PM »

Dang, that JFET op amp on Fred's site is about as simple as you can get! I may have to try that one out sometime. :grin:

CJ · « **Reply #12 on:** June 25, 2004, 04:35:57 PM »

Where do those 170's come in as far as on current?
Is there a suffix for the three different levels, or is that another p/n?
thanks!
John, what kind of report do you want on the Kenyon's?
Complete disection or just inductance, freq plot, and return them to you?
I forgot what the deal was.
cj

Winston O'Boogie · « **Reply #13 on:** June 25, 2004, 05:07:52 PM »

CJ · « **Reply #14 on:** June 25, 2004, 05:10:05 PM »

OK. What application do those two Kenyon's fit?
Mic in? line in?
thanks!
cj

Winston O'Boogie · « **Reply #15 on:** June 25, 2004, 05:16:50 PM »

jdiamantis · « **Reply #16 on:** June 26, 2004, 04:27:42 AM »

"Lastly, I DO think you should buy more. Not to prove how much you love them, but because you can NEVER have enough. I'm down to about 600 2SK170BL's and I'm starting to get cold sweats,
Best regards,

W.O'B. aka John"

Gee. and I thought I was the only maniac hoarding these parts :oops:

The really do sound terrific. I don't want to throw anyone into a panic, but I understand that Toshiba isn't making the 2sk389 any more. I may be wrong, but this is information I've gotten second hand. :shock:

chrissugar · « **Reply #17 on:** June 27, 2004, 05:46:23 PM »

Hey John,when i said I confess, it was about the fact that I am like a drug adict. I like those jfet opamps so much that I built forty of them.
Here are some pictures I made last year.
The opamp boards:

Some half ready opamps:

an opamp instaled in the preamp:

four channels:

chrissugar

chrissugar · « **Reply #18 on:** June 27, 2004, 05:54:43 PM »

Since the pictures were made I modified the preamps.
The ouput caps are now two 22microfarads in paralel for a better low end.

Hope to upload some sound clips recorded with this preamp soon.
I have tons of sound materials [ various bands and instruments ] recorded with this pre so I have to make a selection.

chrissugar

soundguy · « **Reply #19 on:** June 27, 2004, 06:41:24 PM »

whats the main quality about the amplifier that attracts you? IE, what pops out in your criteria process for using that on a source over say an api amp or a neve flavored amp- where does that guy fit in?

dave

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Author Topic: For those who are designing with (J/MOS)FETs... (Read 3346 times)