Too Much Awesome (Boneyard with JFET input buffer)

[pryde]

Hello mgwhit. Re-read this post from the beginning and was curious to know what exact buffer you used in the build. I have a few on vero, including jfet and a klon buffer. If you have had good luck with your's I would like to just build it and throw it in my BY.

I have done all the mods (with your and other's help) and for the most part, the whine is tamed; however, I still get some occasional bouts with certain pickups/guitars. My P-90 equipped tele really sets off the whine in high gain mode. I think its time to end this once and for all with a buffer 

How about the attached vero, would this work out ok or maybe you could attach yours

[mgwhit]

I'm sure that would work fine.  I posted a link to the GGG buffer schematic somewhere on page 1 of this thread, which is very close to what i did and almost identical to the one you've posted.  I think I doubled the  input and output cap vales just to make sure I wasn't losing any low end, and I used a 2n5457 because I thought it had better noise specs than a j201.  (Is that even true?). Once you change the jfet, you need to change r5 to bias it properly.  I used 10K with the 2n5457. I might have done something else, but I can't remember and it honestly doesn't matter.  I'm pretty sure any high-input-impedance/low-output-impedance buffer will do the trick.  If you're unsure, breadboard it first.  Good luck!

[pryde]

Oops I did not see that post. I think I will breadboard a few options and see what fits. I hope to preserve the highs in the boneyard for my rig.

[Strider0007]

Well I tried some other things with this circuit and none completely got rid of the whine. So I put and old BOSS tubescreamer I had laying around before the boneyard and that also did not completely remove the whine, so not even a buffer in from gets rid of it on mine. I might have to do the half gain mod for this to work but I did want the high gain of the original to work   Well I'm sorry I couldn't find the real cause of the problem. I don't if I should spend any more time on this or just put the buffer and be happy with the higher range(b4 oscillation occurs) I can get out of that or spend my time on a different layout instead.

Well thank you for all the info mgwhit and all others who have tried to solve the problem.

[pryde]

 I would go ahead and do the C5/R5 mod and maybe drop the high gain pot down to 250k-500k. You won't really notice a big drop in gain but it did help the whine in mine and some others on here. I think the mod still retains all the high-gain compression and sag. socket them and give it a try.

[pryde]

I breadboarded a few buffers per mgwhit's advice and settled on a simple klon buffer as it sounded the most transparent with my setup compared to the jfet buffer. It ABSOLUTELY kills all whine, whistle, screech, howl, etc with all guitars at loud volumes.

I tested stock r5/c5 values also with perfect results although I changed them back to 100r and 1uf as I like the gain sweep better. I will post my results in the Mods section. Thanks again mgwhit and others.



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[mgwhit]

Nice!  That's a much better job than I did.

[PimpMyTone]

Hello guys,

I posted a while back I saying I was going to look into it and I just got my pedal back from my friend so I apologize for the delay and I just started looking into it earlier today.
So far it looks to be crosstalk from the high gain section being routed too close to the input (R4/R1) and that whole trace passes below all the input components all the way to pin1 of the IC(LF347). So I took out all input components(RPD,R1,R2,C1) except C2 and wired the input directly to that and it took the whine away until I set the vol to like 2-3 o'clock then it started to come back again.
Also looks like it needs shielded input wire.
So next I placed R1 soldered to one side of C2 and it still kills the whine but only until the vol reaches 2-3 o'clock position.
I'm going to experiment a lil more later and post my findings. If it's not getting anywhere after that I'll just etch my own PCB to see if that solves it. I would like to build this without the extra buffer circuit but it might not be worth the effort considering how simple it is to just add a buffer in front of it as it has been mentioned here. I'm just determined to find out why it's oscillating I guess...lol

Here s a picture of an original plexitone if it can helps , it s a buffered circuit and it looks like shielded wire for input and output jacks .