RG Keen's JFET matcher.

mkstewartesq

mkstewartesq

Well-known member
As I mentioned in my PastFX Nick James Foot phaser wishlist thread, I'm not great (read: can't do it at all) at building from a schematic. But so many builds required matched JFETS and the RG Keen JFET matcher is touted as an easy-to-build way to match JFETs, I for one would love a utility PCB to build my own JFET matcher so I don't have to rely on the kindness of others (hey, @fig !) or purchase matched sets, especially for builds that require more than a matched quad. Any way you can make that happen, pretty please, @Robert?

Thanks,
Mike
 
Upvote 8

Why are JFETs such a Pain in the Ass?

How many times do we see post in the Troubleshooting forum where the problem turns out to be a JFET? Like Germanium transistors, JFETs are finicky beasts and buying the right part number does not guarantee success. First, a very brief primer on how JFETs work. JFETs are voltage-controlled...
forum.pedalpcb.com forum.pedalpcb.com

I made this PCB a few years ago. I could send you Gerber files if you want to build it.
 
mkstewartesq said:
As I mentioned in my PastFX Nick James Foot phaser wishlist thread, I'm not great (read: can't do it at all) at building from a schematic. But so many builds required matched JFETS and the RG Keen JFET matcher is touted as an easy-to-build way to match JFETs, I for one would love a utility PCB to build my own JFET matcher so I don't have to rely on the kindness of others (hey, @fig !) or purchase matched sets, especially for builds that require more than a matched quad. Any way you can make that happen, pretty please, @Robert?

Thanks,
Mike
Click to expand...
i know you said you want a pcb, and that would certainly be cool to have, but this could get you by until then:

Greatly Improved JFET Matcher

Collection of vero (stripboard) & tagboard layouts for 100s of popular guitar effects, with over 1000 verified designs. DIY your own boutique effects!
tagboardeffects.blogspot.com tagboardeffects.blogspot.com

there’s also one for measuring Ge pnp (or non) leakage and gain

tagboardeffects.blogspot.com

Germanium Transistor Tester

Collection of vero (stripboard) & tagboard layouts for 100s of popular guitar effects, with over 1000 verified designs. DIY your own boutique effects!
tagboardeffects.blogspot.com tagboardeffects.blogspot.com

i’ve used both these tools with great success :)
 
FWIW, I've built and used DIY JFET matchers and Ge BJT testers and have found that for all the time and effort involved, they are great for educational purposes. But for efficiently conducting the testing/measuring of those devices, I found the Peak Atlas DCA75 far more efficient and even has Windows software for running trace curve analysis on those and other active P/N & N/P devices. Sure, the DCA75 is comparatively expensive, but IMO the efficiency far outweighs the meter-method required of the DIY testers.

PeakAtlas_DCA75.jpg
 
it was easy enough for me to whip up on my Proto board (very cool project in and of itself!), but I do agree it would be cool to have a plug in module that I can hookup to the breadboard to do the same thing.

As a side note, for doing things like these, lightly clamping the probes in the pot terminal blocks works great!
 
KR Sound said:
I just put in an order for 3. If anyone wants one, let me know.
Click to expand...

First - I’ll take one. I’ll PM you so we can work out the details. Thank you.

Second – thanks to EVERYONE who has responded in this thread. I’m probably going to try all of the options here, especially the stripboard builds that match based on other characteristics like ldss and Vp. Why not have the most options open to me, and also learn something in the process? To be clear, however, no matter what I acquire or build, I’m still also going to get the version Robert ultimately releases, because I know that it will be elegant and up to his usual standards of quality.

Third - it would sure be great if anyone interested could upvote my request for a new phaser project in this forum, so that I actually have a pressing REASON to be matching all of these JFETS. 😆

Thanks again,

Mike
 
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