So I've had a maxon od-820 build giving me fits and I've narrowed it down to the jfet input buffer. I'm wondering if its worth tracking down why this jfet is clipping or if it can just be skipped completely like building a tube screamer without the buffer?
What kind of "fits", and what are you feeding into it? Is the pinout correct for the JFET you used? The schems I've seen shows the original had a Japanese SK-variety N-channel.
feeding it regular guitar signal from a les paul. I initially had another jfet in there with corrected pinout and thought maybe that might be the cause even though this is biased only as a buffer so as a last ditch on that front I spent the money to get the proper fet from byoc and its still clipping. just to quickly troubleshoot I removed the clean blend pot, wired strictly for clean, and narrowed the signal clipping to the jfet. Now I'm on the fence as to whether to run down the cause of the clipping or just skip the buffer(should that have no real negative impact)
source voltage is 9.5v, gate is 8.64v
Can you link to a schematic? Also what power source are you using? It's kinda rare to get a JFET source follower to clip with a straight guitar signal.
I mean you could bypass the buffer but my guess is there's something else going on. I'd check for continuity between pins of the JFET and also between nearby components.
The input FET is a 2SK248Y, and it's Idss, VGS(off) are in the range of a 2N5457. Try a 2N5457, which should have a slightly higher VGS(off). Also, did you try other guitars, like a Strat with its neck pickup?