2N4339 JFET substitute?

[matthewspillman]

Hey everyone,

I'm trying to compile the parts for a clone of a Rockman x100, which I intend to put into pedal format. In its distortion circuit, it uses a 2N4339 JFET, which I've only seen available for around $12 USD. That's pretty expensive, so I was wondering if there might be a suitable cheaper alternative. I'm not too worried about it sounding exactly the same, but I still want to know what I should choose. Any thoughts?

[Betty Wont]

What is the jfet doing in the circuit? If it's just a buffer, you could likely sub any n channel jfet.

[oeslicoalfin]

I often use alltransistors.com to find substitutes for obsolete (or unaffordable) transistors. In this instance, it only returned 2N4340 and 2N4341 as equivalent. Not all of their electrical characteristics are equivalent, and I wouldn't be able to answer Betty Wont's type of question even if you posted the schematic...

The 1986 Siliconix FET Data Book (available here: http://bitsavers.informatik.uni-stuttgart.de/components/siliconix/_dataBooks/1986_Siliconix_FET_Databook.pdf) lists their equivalent SMD/SMT part as the SST201 on page 3-12. Mouser lists that part as obsolete, but they have 300 of the MMBFJ201 @ $0.43 each - less if you buy 10 or more. If you don't want to deal with soldering SMT parts, you can get presoldered ones at Lectric FX and other DIY suppliers in the community.

Socket and see if a MMBFJ201 (or one of its equivalents) gets you where you want to go...

[matthewspillman]

Thanks for the replies! To answer Betty Wont's question, it's not being used for a buffer or as a gain stage. Its use is pretty weird and beyond my limited circuit-analysis skills. Here's the schematic for anyone curious (the JFET in question is Q101 on page 2): https://pdfslide.net/documents/rockman-x100-and-soloist-schematics.html

I think I'll go with oeslicoalfin's idea of using a MMBFJ201 for now.