[sdiy] Dual Matched N JFET from Linear

[Mike Bryant]

With a 3k input impedance I can't see any advantage over using a pair of 2SA1312 or similar bipolars.

________________________________
From: Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of S Ridley via Synth-diy <synth-diy at synth-diy.org>
Sent: 21 June 2025 16:57
Cc: synth-diy at synth-diy.org <synth-diy at synth-diy.org>
Subject: Re: [sdiy] Dual Matched N JFET from Linear

I think they're used in ribbon mic preamps like the Cloudlifter.

See US Pat. 9.167,327B1


On Sat, 21 Jun 2025 at 08:51, Mike Bryant <mbryant at futurehorizons.com<mailto:mbryant at futurehorizons.com>> wrote:
The difference to most other dual JFETs is they are on the same silicon die, so are inherently better matched.
Zetex are one of the biggest suppliers of duals - bipolar, JFET and MOSFET - but they always use two die in the same package and these could come from different locations on the wafer so won't be quite as well matched, nor are they so well thermally bonded.

That said, in most applications this isn't really an issue.  I think the very low noise space probe detectors is the only application that really needs them.

________________________________
From: Synth-diy <synth-diy-bounces at synth-diy.org<mailto:synth-diy-bounces at synth-diy.org>> on behalf of Roman Sowa via Synth-diy <synth-diy at synth-diy.org<mailto:synth-diy at synth-diy.org>>
Sent: 21 June 2025 05:12
To: synth-diy at synth-diy.org<mailto:synth-diy at synth-diy.org> <synth-diy at synth-diy.org<mailto:synth-diy at synth-diy.org>>
Subject: Re: [sdiy] Dual Matched N JFET from Linear

Reading just a few lines from the site reveals this is some audiophile
mumbo jumbo, so possibly very high price, and not so much better than
other dual jFETs.
Let me check... yes, the price is about 10x higher than others. One
popular store lists 98 various dual jFETs.
I mean, this is rather destined for discrete audio amps, so why bother f
there are so many over the top opamps cheaper than those FETs. Surely
for experimenter and audiophile market.

Roman

W dniu 2025-06-20 o 22:34, Tim Parkhurst via Synth-diy pisze:
> Hey, Analog Hounds,
>
> Linear Systems is promoting a new Matched Dual JFET, and you might
> even be able to get a sample or two. Useful? Not?
>
> https://www.linearsystems.com/post/why-engineers-choose-the-lsk389-for-high-precision-analog-design?utm_campaign=d2b0395f-db24-487d-8e02-adcff714e7a8&utm_source=so&utm_medium=mail&cid=a05ef50a-a9c5-473d-950b-37f3f1a2d83d
> <https://www.linearsystems.com/post/why-engineers-choose-the-lsk389-for-high-precision-analog-design?utm_campaign=d2b0395f-db24-487d-8e02-adcff714e7a8&utm_source=so&utm_medium=mail&cid=a05ef50a-a9c5-473d-950b-37f3f1a2d83d>
>
> Tim (define "useful") Servo
> ---
> "Imagination is more important than knowledge." - Albert Einstein
>
>
>
>
> ________________________________________________________
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