need some help w/ my Vulcan JFET

[plexi12000]

i assembled joe davission's jfet vulcan on strip board.  JD recommends setting drain volatage around 4.5-5 volts.

the schemtic says 100k resistors.  i was getting about 3.8 v's.  so i dropped down to 82k r's and i got around 4.8 volts.   plugged in and it sucked.

what's up?!  kinda muddy, some 'gating', etc.

assuming the rest of the circuit is ok, which i believe it is, i checked it over several times for a day or two before i assembled...... is anything else i can do? or should i get

some other jfets to plug in?   thank you

[Kipper4]

A schematic would help.
Did you consider using trimmers for the 100ks?

[GibsonGM]

You using the specified JFET?  I've used some 'other' JFETs in circuits (MOSFETs, too), and found that unless using the one they specify, you may need to bias differently, by ear...like Kipper suggests, maybe you have to use trimmers and 'dial it in'.

[mac]

Try a bit more current through the diodes, 4M7 instead of 10M. You'll need to adjust drain resistors.
Or change diodes.

mac

[Kipper4]

This one I assume since you mention its fet

http://www.diystompboxes.com/analogalchemy/sch/jfetvulcan.html

[PRR]

> JD recommends setting drain volatage around 4.5-5 volts. ... i was getting about 3.8 v's.  ..... i got around 4.8 volts.

Nothing very wrong with that.

> plugged in and it sucked.

My guess: something else is wrong.

> some 'gating'

It almost has to "gate" with that diode affair in front of JFET Gate.

[hymenoptera]

> some 'gating'

It almost has to "gate" with that diode affair in front of JFET Gate.

I saw that too, and thought that was a curious arrangement, but then I realized there's a pile of DC on top of them so they're pretty much always conducting a little uA trickle idle at least until the signal goes positive enough to shut them down.

I've read that this is a pretty good sounding circuit and now I'm even more interested to hear it.

[287m]

my successfull jfet vulcan build is with 3 (almost) matched j201
so, 3 drain resistor have same (almost) value
maybe my brain forgot detail

[plexi12000]

thanks for the responses, gents!    it's been a crazy few days around here.  dad has been in and out of the hospital....etc., etc

so the only thing i've done is trying 4.7M instead of 10M resistors.....that pretty much cut off all 'sound'.   dang....i was hopin that would work!  lol

I'd like to try the trim pots next.   THANK YOU

[plexi12000]

This one I assume since you mention its fet

http://www.diystompboxes.com/analogalchemy/sch/jfetvulcan.html

Yes.......this is the one.     Yes......I'm using Fairchld J201's

[mac]

thanks for the responses, gents!    it's been a crazy few days around here.  dad has been in and out of the hospital....etc., etc

Sorry to read this.

so the only thing i've done is trying 4.7M instead of 10M resistors.....that pretty much cut off all 'sound'.   dang....i was hopin that would work!  lol

Did you adjust drain bias?

mac