F5 power amplifier

[panos29]

So, which of the 2SK170/2SJ24 versions is more suited to the F5 schematic as proposed, GR, BL or V? I know this is a silly question but to tell the truth, its the first time I am dealing with Jfets and I am getting a little confused here.
I am sure that Mr. Pass specified everything (as usual) in his article in AudioXpress, but in this part of the world the May issue is not yet available and I am already gathering parts...

Thanks

[jacco vermeulen]

No GR !

[jackinnj]

I made a mistake which Ole pointed out, the schema is changed to reflect the correct S and D connections.

Here's a 3D hypothetical using some Caddock TO-220 feedback resistors which will attach to the heat sink:

[Nelson Pass]

Originally posted by panos29
So, which of the 2SK170/2SJ24 versions is more suited to the F5 schematic as proposed, GR, BL or V? I know this is a silly question but to tell the truth, its the first time I am dealing with Jfets and I am getting a little confused here.
I am sure that Mr. Pass specified everything (as usual) in his article in AudioXpress, but in this part of the world the May issue is not yet available and I am already gathering parts...

Thanks

You want to test Idss for 8+ ma current with the Gate and Source
shorted and Vds at 10V.

BL is the preferred part, but you can use GR if you raise the
Drain resistance. Currently its a 5K pot, in parallel with a thermistor
plus 2.2K in parallel with a 2.2K. You can remove the 2.2K.

Alternatively you can consider paralleling JFETs to get the current up.

[jacco vermeulen]

consider paralleling GR JFETs

There's a thought.
..........Naah.

(howcome, even in walnut veneer i see naked women?)

[Zen Mod]

Originally posted by jacco vermeulen

.....

they are sad

[DaveM]

(howcome, even in walnut veneer i see naked women?)

Because you are a man.

[plep]

Originally posted by Nelson Pass


You want to test Idss for 8+ ma current with the Gate and Source
shorted and Vds at 10V.

BL is the preferred part, but you can use GR if you raise the
Drain resistance. Currently its a 5K pot, in parallel with a thermistor
plus 2.2K in parallel with a 2.2K. You can remove the 2.2K.

Alternatively you can consider paralleling JFETs to get the current up.

Taking the risk to appear publicly too stupid…

Why V grade with a lower R wouldn’t work?
I'm afraid that it would reduce the open loop gain, but the same goes for GR the other way round (I mean increase the OLG with GR).
Best regards.
Philippe.

[Magura]

Originally posted by jacco vermeulen


There's a thought.
..........Naah.

(howcome, even in walnut veneer i see naked women?)

So you're offering a group buy od 2sk147

The answer to your question may be due to Jaccolina or the lack of

Magura

[Nelson Pass]

Originally posted by plep
Why V grade with a lower R wouldn’t work?
I'm afraid that it would reduce the open loop gain, but the same goes for GR the other way round (I mean increase the OLG with GR).
Best regards.

Good question. The amp will work fine with V. I neglect it for two
reasons.

1) try and find any, and if you do, save them for phono stages

2) I want to limit the current to about 8 ma through the circuit to
avoid too much dissipation in the JFET. Of course you can use a
greater value than the 10 ohm for the feedback, but you can
just as easily get by with a BL.