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You can tweak the gain of a common source amplifier (I.e. Tillman) by fiddling with the source and drain resistors. I forget the exact relationship but I think if you tweaked values from Tillmans you may have changed the gain. There’s also some magic to be had by bypassing the source resistor...

Yes I think c2 is redundant now. I don’t think it hurts anything to keep r4. But I’m no expert. I’ve just had a little experience using the ppcb mini buffer onboard and went on a deep dive of jfets, so I feel like I’ve got a little knowledge there but woefully less on other active components...

Any chance you connected the lines where they cross (but don’t connect) on Tillman’s schematic? I could see myself doing that :) Weird that you’d get a signal at the source side but not the drain. So I’m grasping at straws.

Have a look at the Toshiba 2sk208-y jfet (or the 2sk30a thru-hole variant if you can find it). Its noise figure is a fraction of the 2N5457. However I doubt most of any of what you mention will make more of an audible difference than shielding and buffering the guitar itself.

Maybe it’s just a typo but the gate is the input so it should be passing audio from the gate to the output. Might be interesting to see if you get a signal on the source side. Maybe there’s a bad capacitor somewhere.

Would love to know how you modded it for bass

Yes that’s the one. If you have other jfets I’d try them out - even other j201s. Otherwise check connections and fiddle with the source resistor. I like 2sk208-y jfet, if only because it’s part-to-part variation is a lot lower. If one gets out of spec, then tag it with a different suffix. You...

Source followers are theoretically unity gain, but in reality lose a dB or two. You could wire up a common source buffer (like a Tillman) and gain a few dB back. You could also experiment with the source follower and see if you get any change biasing the input to ground rather than mid-rail.

Yes 10uF is way bigger than it needs to be. 1uF is plenty for anything guitar or bass and even .47uF is enough for any reasonable downstream impedence. The capactitor type doesn't really matter (but watch polarity on electrolytics - i've used bipolar here). Ive built a couple of these as onboard...

I get what you're saying. For me, I practice without compression, but compression is on during the gig.

Anyone have this?

Thinking of building one or both of these. The schematic shows insanely low input impedance since the volume is a voltage divider B50k pot at the input before any buffering. I can’t imagine that working well with a passive bass. Yet the originals are pretty legendary. Is that part of the mojo...