Tweed man build. More fun with Jfets

[The Gator]

Looking at the Tweedman circuit, it uses 5 MPF4393 Jfets in it. Which is an obsolete part. I assume this another one of those applications where the specs of the particular jfets should be similar to that of the rrecommendationsmade for the J201s in the chop shop.
I have some MPF4393 jfets, but the Idss of all of them is fairly high ( 1.8 to 2.0 mA)
And the vgs is 1.3 to 1.4 vdc.

Recommendations? Perhaps not even bother with them and just use some smd j201 jfets?

Opinions are appreciated.
Thank you
Gator

 

[MichaelW]

You can get SMD MMBF4393's from Mouser.

 

[eh là bas ma]

You probably already have searched the forum and found this answer ?

Changing the type of JFET or trying JFETs with different Vp & Idss values will alter the clipping tone & amount. You can try 2N5457, 2N5458, J201, or really any other N-channel JFET. You can even use multiple types of JFETs in this build (i.e. 2N5458 in Q1/Q2, 2N5457 in Q3/Q4, and J201 in Q5) . Just make sure the 2 vertically stacked JFETs in each muamp are the same type.

I did a lot of tests, spent a lot of time on this because I really like this circuit and wanted to get the best of it. Finally I used some SK117GR for a almost a year, and recently went back to 4393 because they sound a bit different and also really effective on my build. I think it is a good idea to find some good matched transistors on this circuit. I tried smd J201 with adaptors, but didn't like them. Maybe if you select them carefully you'll find a good match.

Are you sure 4393 are obsolete ? Looks like they're still in production and easy to find. Musikding currently have them available in through-hole version :

MPF4393, 1,65

MPF4393, N-channel JFET Switching Transistor

www.musikding.de

Edit : ...oh, and turning the trimmer into a Presence control on this build, is a good idea in my experience. You have some room under the toggleswitch for an other pot.

 

[The Gator]

Yeah I have some TO92 package MPF4393s, They just don't seem to have good specs for this. MichaelW is probably right, the smd version is probably the way to go.
Really. I just need to socket all five jfet positions and go from there.try what i got, then if I don't like it, get the smd versions.

Eh la bas ma you are definitely right about the presence control. Thought about using a bigger enclosure and a different layout.