The J201 is one of the most interesting and studied components in the pedalbuilding community. Its low Vgs(off) value makes it a great low-voltage emulator of a vacuum tube. It has been used in dozens of amp emulation circuits, notably many of the classics from Runoffgroove.com as well as the Dr. Boogey and Jack Orman’s Mini Booster.
The bad news: the J201 has been discontinued in through-hole TO-92 format for several years. There’s no other cross-reference part that works quite the same as the J201, so you’re stuck soldering microscopic parts, paying high prices, or risking buying fakes (and there are lots of fakes).
These are genuine MMBFJ201 (SMD equivalent) parts from ON Semiconductor that have been pre-soldered onto an adapter so they can be used in through-hole layouts. Nearly all of them are within the Vgs(off) range of -0.60V to -0.90V and will perform exactly the same as the through-hole J201 that most circuits are designed around. They also have a blank white screenprint on the reverse side so that you can write in the Vgs(off) value if you want.
You’ll have to solder in the legs yourself (pro tip: clipped leads from resistors or diodes work great)—but we got you most of the way there!
They are available in sets of 4 and 8. The sets are panelized, so they will need to be manually broken apart and the tabs removed before use.