Fornicus Transistors Question

[jengo7542]

Hey guys I wanted to try a project where I make 2 builds of the fornicator pedal. One with precision parts specified in the parts list. Then one with old cheap "mojo" parts with the same values. My main question is what transistors would you guys recommend that I can interchange with the JFETs on the parts list:

Q1 J201 JFET transistor, N-channel
Q2 2N5457 JFET transistor, N-channel
Q3 J201 JFET transistor, N-channel
Q4 2N5089 BJT transistor, NPN TO-92
Q5 2N5089 BJT transistor, NPN TO-92
Q6 2N5457 JFET transistor, N-channel

I tried reaching out to Small Bear but they recommended posting here since you guys would probably know the circuit better. Any help would be greatly appreciated. Thanks!

 

[spi]

where do you plan to get the old cheap "mojo" parts?
For the jfets, I would stick to the ones listed in the BOM. If you are swapping, you can't really rely on part number, you'd probably want to measure the Vp and Idss of the parts to be sure they'd work.

For J201, try to match Idss between 0.3 to0.83mA and Vp -0.57 to -0.97 V.
For 2n5457 try to get Idss 1.9 to 4.11mA, and Vp from -1.22 to -1.80 V.

 

[jengo7542]

where do you plan to get the old cheap "mojo" parts?
For the jfets, I would stick to the ones listed in the BOM. If you are swapping, you can't really rely on part number, you'd probably want to measure the Vp and Idss of the parts to be sure they'd work.

For J201, try to match Idss between 0.3 to0.83mA and Vp -0.57 to -0.97 V.
For 2n5457 try to get Idss 1.9 to 4.11mA, and Vp from -1.22 to -1.80 V.

Luckily have a dad who was into electronics before my time and ripped and collected the resistors, caps, diodes, pretty much any small parts from older electronics. I know I've got pretty close to if not all the rest of the partslist with the specified values. I'm just a little stuck on older transistors that would work as replacements. I thought I'd ask here since im sure im not the first to try something like this with similar types of pedals. Thanks I'll keep that in mind and definitely measure before soldering anything in place with parts that old

 

[jwin615]

$5 jfets?
I would advise to stick to the BOM and take SPIs advice.
You can't just swap jfets like Si transistors. Well, you can. But no mojo-img will ensue. Likely that no audio will either.
Appologies if you very much know what you are doing here. But from the way your question reads, it seems that there may be some knowledge gap.
To somewhat answer your question, you may be able to use some of the jfets boss utilized like the 2SK184, 2SK30A, 2SK117, and 2SK369. You would need to check the datasheets and measure them.

Some comps for J201 are BFW 13, 2N4338
5089 comps: BC 169, BC 184, BC 239, BC 549, or any NPN with a beta around 600
5457- BFS 71, 2N3822, 2SK246, 2SK330, 5458, 5459, BF 244-245
No guarantee that any of the above jfets will work. They're just the closest.