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Old 23rd April 2009, 06:58 PM   #11
mlloyd1 is offline mlloyd1  United States
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indeed
could it be part of the alleged trend of the slow death of the true spirit of do it (mostly) yourself?

mlloyd1
who remembers the good old days while approaching old pharthood

Quote:
Originally posted by Nelson Pass
That's unfortunate. The simplicity of this stuff begs for
experimentation.
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Old 23rd April 2009, 07:46 PM   #12
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by mlloyd1
......... while approaching old pharthood






ZM
(who is rushing now to put new line in sig ...... "my Papa is smarter than your Nelson " )



edit:

everything is goin' in circles ..... even DIY , and even my Papa ..... using good ole 109 again and again .....

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Old 23rd April 2009, 08:10 PM   #13
Magura is offline Magura  Denmark
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Quote:
Originally posted by mlloyd1

could it be part of the alleged trend of the slow death of the true spirit of do it (mostly) yourself?

That's just the way things has become.

This weekend the Mrs. and I went to a diyaudio meeting in Sweden (Gbg).

We were among the few under 50, I tell you we felt young in that company.


A bit on topic:

2SK170 is easy to find and cheap, a fine choice.

If you wanna go all over board, 2SK369 is the ticket, hard to find, and sure expensive if you manage to find such.

The rest are on par with the 2SK170 or below.


Magura
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Old 24th April 2009, 03:58 AM   #14
EUVL is offline EUVL  Europe
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I consider BF862 on par with 2SK369, if you can live with the current. And they go as low as 12mA Idss.


Patrick
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Old 29th April 2009, 05:02 PM   #15
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Hereís some data on JFETís all recently acquired looking for substitutes in some applications. The data was taken with a QuanTech semiconductor noise analyzer. I took all data at 1mA drain current to compare the JFET ďbetaĒ parameter across the lot. My noise FOM is the flatband noise (100kHz) compared to the theoretical noise (from .66/gm). This should be ~1 but the fudge factor is computed from an ideal JFET (Shockley 1952), still they were pretty close.

Some comments - The J305 needed selection and still was not great but the J310 was surprisingly good. The 2SK222 is a great FET for microphone circuits since itís noise is excellent and the Cís are substantially lower than the 2SK170. The BF862 was a surprise and folks here have already discovered it, also low Cís. I have not found any bad ones yet datasheet aside. J177 has something wrong like excessive gate series resistance.
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Old 29th April 2009, 05:11 PM   #16
steenoe is offline steenoe  Denmark
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Quote:
Originally posted by scott wurcer

but the J310 was surprisingly good.
Indeed, they performes extremely well in the Pumpkin. Better than expected, anyway.

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Old 29th April 2009, 05:31 PM   #17
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by steenoe

..... Better than expected, anyway.




feel free to put 2SK369BL instead ....... but be prepared to fiddle with source degeneration , to suit your ears .... and ensure that OLG not ricochet to heaven ....

but dunno what result could be , sound wise

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Old 29th April 2009, 06:46 PM   #18
EUVL is offline EUVL  Europe
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Scott,

The BF862 was a great tipp. So is the 2SK222/223, especially if you need high Vds.


Many many thanks,
Patrick
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Old 29th April 2009, 06:50 PM   #19
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Yes, thanks for that, Scott.

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Old 2nd May 2009, 02:06 PM   #20
BFNY is offline BFNY  United States
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Quote:
Originally posted by scott wurcer


Some comments - The J305 needed selection and still was not great but the J310 was surprisingly good. The 2SK222 is a great FET for microphone circuits since itís noise is excellent and the Cís are substantially lower than the 2SK170. The BF862 was a surprise and folks here have already discovered it, also low Cís.
I can't find the 2SK222 for sale anywhere - tried Avnet, Allied, Digi-key, Mouser, MCM, Newark, no luck. Any hints where to buy 2SK222 in volume today?

Any preference for brand of manufacture on the J310? Mouser sells Fairchild and OnSemi. I bought some of both, but wondered if anyone has compared. What brand was used for results in the table?

Also bought some BF862. Sorting these small suckers will be somewhat sobering.
Bob
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