Has Anyone Seen This JFET Matching PCB Project?

T

ToneAlchemists

Member
Hey pedal PCB enthusiasts!

I stumbled across a recent YouTube video showcasing a really good project: a PCB specifically designed made in Kicad for JFET matching, which could be super handy for phaser circuits and other builds.

Here's the YouTube video, which also has the links to his GitHub JFET Project and other related resources.


The creator has generously shared the KiCad files and documentation for this "FET_Matching" project on GitHub: -> FET_Matching .

RG Keen - JFET Matching for Effects


From what I can tell, the circuit seems to be inspired by R.G. Keen's work, which is always a good sign!

Has anyone else come across this, or perhaps had a chance to check it out? I'm curious to hear your thoughts on it. Does it look like a solid solution for JFET matching?

Cheers!
 
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This is super cool. I'm building a JFET phaser for the first time at the moment, so it's serendipitous that you've posted this here. I don't see any reason why this wouldn't work, but I'm certainly no expert. I'll order some PCBs and eventually get around to building them once they arrive.
 
When i first started learning how to use eagle i did this circuit for practice. It was small, easy to test and I didnt have to worry about spending a lot of money on parts if i did it wrong, lol. i wanted to do a phaser so it checked all the boxes. I think i found the schematic on JMK way back when. I have used it a handful of times and it works great. If i can find the boards I will be happy to send you one.
 
I've got some fabricated a few weeks ago through JLC and tested with already matched Quad Jfet J113's.

Here's one of the J113 that I used it on, I also tested all the other Quad Matched J113 I had purchased from: J113-Matched-Quartett

Anyway seems to do the job, the layout could to do with a little tweaking to create more space with the tactile button and IC, Electrolytic, MLCC. Also I would swap out the MLCC for a Polyester Film Box pitch. Otherwise it seems to work fine.


20250530_093906.jpg
 
temol said:
Not necessarily...
For example - mmbf5457 from one tape, I unpacked about 20 pcs. Vp between -1.4V and -1.6V. It all depends on how small a spread you need.
Click to expand...
Same experience here. Tested a batch of MMBFJ201 from Mouser recently. VP of most was around -0.5V but there were groups of outliers at around -0.35V and -0.8V.
 
I made both of the testers from tagboardeffects.com and I could only get the greatly improved JFET tester II to comfortably work for me. The one without the opamp. The one with the opamp gives me Vp readings of ~9.5v, the same as the power voltage going in to the circuit. Idk why. I’ve checked and rechecked the board and component placement. Nothing helps! But the other one does work great! Just tested a batch of about 20 MMBF5457’s last night.

I’ve been on a JFET kick lately. Learning all about their parameters and such. Other than the building of pedals, the learning, to me, is just as much fun!!!
 
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