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Old 5th May 2011, 10:26 PM   #1
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Default 2SK170BL and 2SJ74BL

Just wondering, Surely there are other devices, but most of the Pass Items require these two J-fets. Obviously, they are slowly going away. Most of the Pass projects require them.

Once gone, what will be the standard replacement, or other complemetary pairs the will accomplish the same goal? I recall one company has a 2SK170BL replacement, but no 2SJ74BL replacement.

Just wondering,

Russellc
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Old 6th May 2011, 01:09 AM   #2
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Linear Systems is making the LSK170 and we hope to see production of their
LSJ74 soon.

There are some complementary parts (usually designed as switches) which
can serve in power amplifiers, and there still is significant stock on the
originals - you just have to pay a premium for them.

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Old 6th May 2011, 01:21 AM   #3
CeeVee is offline CeeVee  Portugal
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Yes Nelson there must be somewhere genuine parts but in past weeks i bought 2sj74BL from schuro, utsource and NIKKO and they all measure between 17ma and 20ma Idss......

i would like to buy genuine ones...but where ?


PS: i did test my setup with other genuine ones i have , that i had previously tested and these confirmed the values.

Last edited by CeeVee; 6th May 2011 at 01:24 AM.
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Old 6th May 2011, 01:37 AM   #4
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Wow, sell them to me !
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Old 6th May 2011, 03:57 AM   #5
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Quote:
Originally Posted by CeeVee View Post
Yes Nelson there must be somewhere genuine parts but in past weeks i bought 2sj74BL from schuro, utsource and NIKKO and they all measure between 17ma and 20ma Idss......

i would like to buy genuine ones...but where ?


PS: i did test my setup with other genuine ones i have , that i had previously tested and these confirmed the values.
Test them for transconductance. 2SJ74BL's shouldn't have Idss anywhere near that high.

You can use the GR rated devices.
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Old 6th May 2011, 07:01 AM   #6
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If Pd and Max.Supply Voltage are a bit low, BF862 may be a good replacement for 2SK170.
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Old 6th May 2011, 08:02 AM   #7
PMA is offline PMA  Europe
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Quote:
Originally Posted by Nelson Pass View Post
we hope to see production of their
LSJ74 soon.
Would you kindly provide more specific answer? I am afraid we have been 'hoping' about 3 years or more for them to produce the LSJ74.

Regards,
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Old 6th May 2011, 08:08 AM   #8
PMA is offline PMA  Europe
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Quote:
Originally Posted by CeeVee View Post
2sj74BL from .... and they all measure between 17ma and 20ma Idss......
They would be most certainly fakes, I am afraid. I bought parts labeled as '2SJ74' from one HK supplier, as a trial. They also measured some 17 - 20 mA Idss. But have low transconductance AND noise higher about 20 - 30dB at low frequencies. I test the parts in my discrete preamps and noise spectrum + FFT distortion measurement are the best answer if the part is fake or not.

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Old 6th May 2011, 11:01 AM   #9
generg is offline generg  Germany
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I just measured my quadruples of SK170 and SJ74 I got from Spencer

Toshiba 2SK170BL for sales

Exactly 10,2 mA for all! Good work, Spencer! Keep on selling the real stuff!
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Old 6th May 2011, 11:07 AM   #10
CeeVee is offline CeeVee  Portugal
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I also have quadruples from Spencer...genuine stuff, all measure as you say.

The 2SK170BL are not a problem it seems, i have plenty, all tested and matched.

It's the 2SJ74BL that are much more scarce that are the problem.
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