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Alternative N Channel JFETs for LTPs

post #1 of 10
10/16/09 at 7:38am
Thread Starter 
The 2SK170 is pretty popular these days but their price and availability is making it less attractive.

I'm wondering if there are any good/even better alternatives from vishay siliconix, on semiconductor, fairchild etc (common manufacturers) that I can substitute the 2SK170 with.

I'm using these JFETs mainly for the Input Long Tail Pair of a conventional three stage/two stage discrete amplifier, so anything low noise and decent enough transconductance is appreciated.


I've been contemplating to use PN4393/PN4392 but they have a wide spread of IDSS. FETs usually like being operated near IDSS to sound nice and with the mentioned alternative it seems a bit unpractical. The PN439x also has lesser transconductance albeit being better in terms of Ciss. I figure we degenerate these FETs and the VAS anyway why do we need more gain?


Subjective qualities are welcomed too
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post #2 of 10
10/16/09 at 7:51am
4$ the matched quad of 2sk170, 33$ for 100 unmatched pieces.

It doesn't look like expensive to me.

Toshiba 2SK170BL for sales - Page 29 - diyAudio

I ordered from this vendor 6 matched quads of sj74/sk170 for 33$ shipped. No problems to report (but the sj74 are running low).
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post #3 of 10
10/16/09 at 8:01am
Thread Starter 
Hmmm, that does not look bad at all , going to try it out asap. Thanks a lot.

But still, I'd like to know if there are any other variants. Too relying on a scarce source does not look like a good idea, especially for folks like me who lives in some other countries.
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post #4 of 10
10/16/09 at 8:10am
2N5459 is pretty close to 2sk170 spec wise. It is in the same Idss class with 2sk170 with a little bit lesser transconductance. It also has 2N5462 complementary p-channel.

I used them in my JISBOS with a little bit modification, because I couldn't source the 2sk170 locally. They work really well (sound pretty good to my ears)

I also use 2N5458 (the lesser Idss of 2N5459) in my own Amp design. since I had some leftover. It work surprisingly good with interesting sound which I enjoy listen to it.
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post #5 of 10
10/16/09 at 10:21am
Thread Starter 
Any good words on the 2N5911/22?

Specs looks good, though the usual lower transconductance and higher IDSS spread.
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post #6 of 10
10/16/09 at 2:31pm
Linear Integrated Systems - Products

monlithic duals seem to be a good idea for diff pairs

also the ~1nV noise fets have large parasitic C which is nonlinear with common mode V in diff pair inputs - smaller die 3-6 nV en parts can be a better choice at line level - particularly with a volume pot in front
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post #7 of 10
10/16/09 at 3:28pm
But where do you buy this Linear parts?
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post #8 of 10
10/16/09 at 4:19pm
I can supply some Linear Systems LSK-389s in onesies twosies.

se

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post #9 of 10
10/17/09 at 9:44am
Thread Starter 
Quote:
Originally Posted by jcx View Post
Linear Integrated Systems - Products

monlithic duals seem to be a good idea for diff pairs

also the ~1nV noise fets have large parasitic C which is nonlinear with common mode V in diff pair inputs - smaller die 3-6 nV en parts can be a better choice at line level - particularly with a volume pot in front
thanks, those seems to be very luxurious items but unfortunately they are hard to come by in my country

I'm looking for FETs from larger companies like Fairchild/On Semiconductor.

I see the 2N5911 is recommended on the list will try out the Vishay Siliconix version.

Quote:
Originally Posted by Koyaan I. Sqatsi View Post
I can supply some Linear Systems LSK-389s in onesies twosies.

se
thanks bro, but i cant spend 30 USD just for shipping a few fets
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post #10 of 10
10/17/09 at 1:29pm
Quote:
Originally Posted by TzeYang View Post
thanks bro, but i cant spend 30 USD just for shipping a few fets
Actually, I can ship to Malaysia for $12.95 via Priority Mail International, or $4.40 via First Class Mail International.

My source wants $12 each for the LSK-389s.

Let me know if you change your mind.

se

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