Davisson’s JFET Vulcan |
I happened to notice a thread on diystompboxes.com started by Aron about Joe Davisson’s JFET Vulcan. You can listen to some mp3 clips that Aron posted in that thread. I had a layout for the BJT Vulcan from several years back so I decided to update it and convert it to the JFET version. This layout has not been verified yet, but I am confident that it is correct. If you do verify it, please let me know. You should be able to fit it into a Hammond 1590B enclosure.
Note that no power supply filter is included. Depending on your power source, you may want to add one. And the output comes from the middle lug of the LEVEL pot.
You may want to breadboard your build first in order to get the bias right for the JFETs. Choose values for the three 100K resistors that give you JFET drain voltages of 4.5V to 5V. Also, check out Joe’s notes about component values for higher gain.
Kirby said:
is that a render? if so, what did you use?
Posted 12.06.2008 at 10:16 am
gaussmarkov said:
POV-Ray and Eagle3D.
Posted 12.06.2008 at 11:11 am
bobby said:
http://www.instructables.com/id/Render-3D-images-of-your-PCBs-using-Eagle3D-and-PO/
Posted 27.08.2008 at 5:35 am
gaussmarkov said:
nice!
Posted 27.08.2008 at 7:35 am
culturejam said:
Verified!
It sounds awesome. I forgot to check the 100k resistor values and just soldered everything. The result was good, but a little mis-biased sounding. So then I swapped out JFETs, and the closest I could get to “proper” bias is 4.7v, 4.2v, and 3.9v, respectively. Oh man, it sounds so damn good. Like a hot-rodded Muff crossed with a SLO.
Great layout. Thanks!
Posted 22.09.2008 at 9:03 pm
Jim’s Personal Blog » Blog Archive » JFET Vulcan said:
[…] I did a breadboard of the ‘JFET Vulcan‘ after reading about it on the Gaussmarkov site. Here lately I’ve been just whipping […]
Posted 09.10.2008 at 2:58 pm
Jim said:
That’s so weird that it automatically posted a weird link to my blog that I just did about this circuit…
Anyways; go here if you wanna check it out.
http://bandslink.com/wordpress/?p=33
Love your site man!
Posted 09.10.2008 at 3:00 pm
culturejam said:
Jim: I built the Vulcan from the PCB layout here, and it sounds much heavier than the sound clip that you posted on your blog. Mine is in Big Muff territory, but not as compressed.
I went with 100k resistors, but then I swapped out JFETs till I got some that would bias properly.
Posted 31.10.2008 at 10:33 am
drushton2002 said:
hey man i can’t wait to try this. are there any tweaks or switches to anything like that? different caps for boosts tone changes etc. i love switches LOL. cool site man thanks for having this stuff
Posted 08.11.2008 at 3:28 pm