2SJ109 in Aleph J: Is Vgrade ok?

[krivium]

Hi to all.
I may have a possibility to source some 2SJ109 (but few of them...not more than 2/4) V grade.

From some search on the forum i found that for the Aleph J (i plan to buid) preferably they must be BL type, GR won't work but not so much info about the V type.

I would say it should be ok but could you confirm me this and eventually modification from the original schematic from Mr PASS in case it's needed?

Many thanks to you.

Krivium.

[h_a]

Hi,

the AlephJ biases the frontend with the aid of a constant current source at 8.3 mA; so regardless of grade anything works that has an IDSS of above 4.15 mA (the 8.3 mA is split between the 2x jfets in the package).

You can use it (without modifications), however, there might be better chances to use the V.

Hannes

[Bill Fuss]

Don't you think you would need a little room on the Idss for signal swing? If you run out the front end will clip. I generally use an Idss as high as the total front end current, which can be adjusted to match the Idss of the jfets you are using.

[krivium]

Hannes thanks for the answer.

I generally use an Idss as high as the total front end current, which can be adjusted to match the Idss of the jfets you are using.

Bill could you explain more? EG for the 2SJ109V in Aleph J it would be a modification of R8 from 1k to 500r for example?