Introducing: The Hard Pusher!

[petemoore]

  Not sure how that diode figures in the gate biasing...possible...that 1m could be right on the gate...Don't know, just wondering out loud here...
  Test the Jfet's bias voltages and it should amplify...whether/how much signal makes it past the 1n34...
 

[KerryF]

ok i have it all layed out on the breadboard.

*NOTE: On the Breadboard Layout, Grnd is actually one strip below what it says.  Also, Pot Lug 3 goes to this corrected grnd.

Im about to test it.  *Crosses Fingers*.

[KerryF]

Ok tested and being stupid.  I figured out that the diodes are cutting the sound from being 100% (without diodes) to like 5-10% (with diodes).  I can hear it if I turn my amp all the way up with the diodes.  I guess that idea was stupid.  So now without the diodes its nothing really special and it even works without a battery.

[slacker]

hey man theres nothing stupid about it, it's experimenting, some things work some don't.
I've just finished breadboarding it as well, without the tone control, and if you remove the 1N34 after the fet it boosts nicely.
The only thing is you get weird ghost notes on the higher frets, which I think are caused by the input diode.
If you put a second diode in parallel with the input one but the other way round, then you get a nice loud booster. The sound is much louder than simply removing the first diode, so your idea of the diodes creating boost works. Don't ask me how but it does.

[KerryF]

Slacker.  Awsome!  Did you use the schematic to breadboard or the layout?  Because like I said there was a Grnd mistake on the layout.  But I will try taking off the second diode and put two diodes in parallel to clip eachother in the first spot.

Good that it works for you!

[slacker]

I just built it from the schematic. Looking at your layout the gate and source are the wrong way round, which might explain why it didn't work. You definitely need to remove D2 otherwise all you get is splatty noise.
I also accidentally put the 1Meg resistor on the other side of the input cap I don't know if this makes any difference. I also used a 1.5k resistor from source to ground instead of the 10k as this seems to be a value thats normally used. Again I don't know what difference this makes, I'm not really up on jfet circuits.
This is what I ended up with, hope you don't mind me posting this, just thought it would explain things better. If you've got any issues I'll happily take it down.

[KerryF]

Its fine that you posted that.

What I found out is that you dont need both of those diodes clipping eachother.  The one going the original way isnt doing anything that way.  The reversed diode is all you need.  And try it as a 1N34.  Much more boost that way.  Let me try to switch the JFET around.

[KerryF]

I turned the JFET around.  Not much of a difference except that now it only works with the battery connected so thats right I guess.  I have experimented with lots of stuff and its still not really doing what I want.  Also, I dont know how yours is working with a 1k5 resistor there.  I barely get sound with that.  Try a 1m.  Maybe I should try to add a JFET stage after the original one.

[slacker]

check the datasheets for your jfet but I think most J201s are the same in which case looking from above with the curve facing right like in your layout the pinout should be.
D
S
G

All you need to do to correct the layout is change where the source resistor and input diode goes. Like this



If you've got a DMM check the voltage on the drain of the j201 you should be able to adjust it to about 4.5 - 5 volts with trimmer then you should definitely get some amplification.
The 1k5 resistor should be fine, it's what the fetzer valve uses.

[lovekraft0]

In your last schemo, the 1N34 on the FET drain will charge up the two caps until they cut off the output - you need a path to ground for the caps to discharge. Maybe something like this would work.

R7 should allow the caps to discharge without shunting too much of your signal, so you don't lose your boost - just another idea, if you'd like to fool with it. It looks like it would mangle the signal pretty badly! 

[KerryF]

THanks for that new schematic, and that layout slacker and lovekraft.  I will try both today 

[MartyMart]

If you remove D2 and turn D1 around, it looks a bit like a "Vulcan-ized" Fetzer Valve

MM

[Meanderthal]

 Hey, now that it's on the breadboard, try the filters and/or tone control- maybe the Hammer stupidly wonderful tone control mentioned earlier, play with the values of the caps and bias resistors, ya know, tweak it and tune it til it sounds really cool to ya! Go ahead, have some fun...