j201 substitute

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Re: j201 substitute

Postby Manfred » 02 May 2019, 03:14

I bougth a bunch of 2SJ74 JFETs in China none of these works in the circuit, so I have tested all using my semiconductor test device.
The device identified the transistors as a fake these were not JFETs but darlingtons.
The printing was 2SJ74, I no longer trust the chinese semiconducter sellers.
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Re: j201 substitute

Postby Manfred » 02 May 2019, 11:29

POTL wrote:I ordered adapter cards from to-92 to sot23 and wait for them.
I looked at the digikey and mouser sites that most of the popular jfet are no longer produced, but the following are still available:
J113
MMBF4393
2SK208-R
2SK209-Y
MMBFJ270
MMBFJ177
MMBFJ309
2SK3666-2

Most likely, closer to the summer I will write which transistors work well.


I ran a simulation with following JFETs:
J113, 2SK208-R, 2SK209-Y
I read the values of the real circuit using the J201 and the J113.
The 2SK208_R and the J113 don't work as a substitute.
The 2SK209 could be a good candidate, that I need to investigate more closely.
FetSubstitute2.JPG
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Re: j201 substitute

Postby POTL » 02 May 2019, 20:04

I wondered, some transistors are listed as amplifiers, some only as switches. Could this somehow affect the sound?
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Re: j201 substitute

Postby Manfred » 02 May 2019, 22:48

POTL wrote:I wondered, some transistors are listed as amplifiers, some only as switches. Could this somehow affect the sound?


The transistors for audio application are designed in consideration of low noise figure.
The switching transistors usually have higher forward transconductances to ensure a faster switching performance.
The inherent capacitances of both types are in the same range of few Picofarads and have no effect on the audible frequency range
except for the Miller capacitance ( Cgd * gain of the stage @ source circuit).
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Re: j201 substitute

Postby lcv » 03 May 2019, 20:19

Hi,
I just received some interfet j201 from Mouser.
Quite expensive.
Their parameters sit around Idss= 0.23 - 0.30mA, Vto=0.5 - 0.6V, I would say towards the lower spec limits (I didn't test all of them)
https://www.mouser.it/ProductDetail/InterFET/J201?qs=sGAEpiMZZMv4z0HnGdrLjo0W1AxRZQdlr4Y9S0sHX3DXCATSkEoEcg%3D%3D
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Re: j201 substitute

Postby BSA Chawngthu » 03 Aug 2019, 14:46

I think that Jfet of this kind are hard to find, so why do we discover it, which have the same sounding thing, let us venture here, or else we made the manufacturer a gold mine, i am sure that we can make a sound out more like this ore even much greater, lets shot at the IC, Tranny we had here and make even bigger sound than olden days.
This old jfet luckily i have source it from a very old radio, it sounds very nasty, i have use it to all my project, it really sound nasty, but we can find another nasty one, lets say we modify the one we could find and we just do the meth, i dont know if it will work but i hate when you could not find a parts
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Re: j201 substitute

Postby SpencerPedals » 06 Aug 2019, 19:50

BSA Chawngthu wrote:we just do the meth


I was wondering to myself how The Great J201 Hunt was progressing and checked in today. Amphetamines have now been suggested. It's not the best idea, but certainly might speed the work along...

For this message the author SpencerPedals has received thanks:
Nocentelli (18 Aug 2019, 15:42)
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