Author Topic: JFET Vulcan  (Read 29048 times)

petemoore

Re: JFET Vulcan
« Reply #20 on: December 09, 2011, 06:41:12 AM »
 I"m no expert on Vulcan tech, but Jfets are not the same as other Jfets, even J201's.
   ...the Fetzer Valve article [and related Jfet measuring circuit] and GEO have good info on biasing Jfets.
   
Convention creates following, following creates convention.

corcia

Re: JFET Vulcan
« Reply #21 on: December 09, 2011, 08:30:40 AM »
my question might be sillier than it seems....  ???
i'm starting from Gaussmarkov layout (and website), in his description, Gaussmarkov says "Choose values for the three 100K resistors that give you JFET drain voltages of 4.5V to 5V", my question is: where do I have to measure the drain voltage of each JFET? I don't know in which part of the circuit place the VOM probe to measure said voltage

PS: i apologize for my ignorance!!!!!!

Suicufnoc

Re: JFET Vulcan
« Reply #22 on: December 09, 2011, 08:34:15 AM »
i'm starting from Gaussmarkov layout (and website), in his description, Gaussmarkov says "Choose values for the three 100K resistors that give you JFET drain voltages of 4.5V to 5V", my question is: where do I have to measure the drain voltage of each JFET? I don't know in which part of the circuit place the VOM probe to measure said voltage

Measure from ground to the drain of each JFET(the pin connected to the 100k resistor.)
Sticks and stones may break your bones, but words can get you shot

corcia

Re: JFET Vulcan
« Reply #23 on: December 09, 2011, 09:31:07 AM »
i'm starting from Gaussmarkov layout (and website), in his description, Gaussmarkov says "Choose values for the three 100K resistors that give you JFET drain voltages of 4.5V to 5V", my question is: where do I have to measure the drain voltage of each JFET? I don't know in which part of the circuit place the VOM probe to measure said voltage

Measure from ground to the drain of each JFET(the pin connected to the 100k resistor.)

ok, so I was right...my question was sillier than it seemed!!!

thanks a lot!!!

WGTP

Re: JFET Vulcan
« Reply #24 on: December 11, 2011, 01:04:36 PM »
No, it's a good question.  Jfets are notoriously random.  ;)
Stomping Out Sparks & Flames

DDD

Re: JFET Vulcan
« Reply #25 on: December 30, 2011, 09:44:09 AM »
What will tighten the sound up and "clarify it" would be a 0.002 cap instead of 0.1 before the 1M gain control. In general - smaller caps throughout.
Well, 2.2 nF cap instead of the very first 0.1 uF cap would do the work a little bit better.
Too old to rock'n'roll, too young to die