Here's a chunk chunk I finished yesterday. I used the biasing method outlined by cleggy. Plastic jacks on this build so I used a crimp on ring around the footswitch to ground. I twisted the output and ground wires together and this thing is silent. Sounds great! Metal licks sound legit using this, I love it.
(http://imageshack.us/a/img109/1559/topvt.jpg)
(http://imageshack.us/a/img829/6471/biass.jpg)
(http://imageshack.us/a/img37/7897/gutsu.jpg)
Sorry for the out of focus shots. I was too lazy to drag out the tripod.
Thanks for looking.
Wow, that is clean. Great etched plate for it as well. Very nice overall, Keefe.
Love the blue theme on the inside.
It seems such a shame that super clean builds like that get shut up and never see the light of day. :D
Looks great Keefe! I have a Chunk Chunk I need to finish up too. Could you point me to the biasing method Cleggy uses?
Thanks,
Jim
Quote from: pickdropper on February 09, 2013, 02:48:02 PM
Wow, that is clean. Great etched plate for it as well. Very nice overall, Keefe.
Thanks Dave. And thanks for the great 3pdt footswitch too. Those extra ground pads came in quite handy for this unit. i think I used all of them.
Quote from: Axe_34 on February 09, 2013, 02:53:46 PM
Love the blue theme on the inside.
It seems such a shame that super clean builds like that get shut up and never see the light of day. :D
Thanks Axe_34, I bought a bunch of those blue caps and had blue wire so I thought why not.
Haha, I know what you mean about the wiring; no one will ever see it. Maybe if I ever do another one I'll use a clear box. :)
Quote from: electricstorm on February 09, 2013, 02:57:54 PM
Looks great Keefe! I have a Chunk Chunk I need to finish up too. Could you point me to the biasing method Cleggy uses?
Thanks,
Jim
Hey Jim
It comes from a geofx page somewhere, and involves some cutoff voltage measuring and then a simple formula to determine the bias for each jfet. If you google fetzer valve geofx you'll probably find it.
Here is the method Cleggy and juansolo came up with for the chunk chunk/dr boogie (I hope I'm crediting the right people)
q1 and q2 are j201 and you're looking for ones that measure around -.3 or so
q3 and q4 are 2n5457 and you try to find ones that are -1 to -1.1
q5 isn't important. i used a 2n5952 so that's why it's installed backwards to the silkscreen; different pinout.
the formula used is just (0.6*supply voltage)+(0.7*positive cutoff voltage)
so if your first jfet is -.3 you would get (0.6*9v)+(0.7*0.3)= bias it to ~5.6
they also recommend changing the 1nf cap to 10n to remove high end fizziness
cheers
Quote from: Haberdasher on February 09, 2013, 03:08:41 PM
Quote from: pickdropper on February 09, 2013, 02:48:02 PM
Wow, that is clean. Great etched plate for it as well. Very nice overall, Keefe.
Thanks Dave. And thanks for the great 3pdt footswitch too. Those extra ground pads came in quite handy for this unit. i think I used all of them.
Quote from: Axe_34 on February 09, 2013, 02:53:46 PM
Love the blue theme on the inside.
It seems such a shame that super clean builds like that get shut up and never see the light of day. :D
Thanks Axe_34, I bought a bunch of those blue caps and had blue wire so I thought why not.
Haha, I know what you mean about the wiring; no one will ever see it. Maybe if I ever do another one I'll use a clear box. :)
You know, I didn't even notice that at first. I can't believe I missed it.
Super nice your Dudeness :)
I may need to hit you up for a custom etched plate for my chunk build
Super neat!
I like that new board a lot. Well done sir!
Jacob
Quote from: pryde on February 09, 2013, 03:53:48 PM
Super nice your Dudeness :)
I may need to hit you up for a custom etched plate for my chunk build
cool! just give me a shout mang. :)
Quote from: juansolo on February 09, 2013, 04:06:25 PM
Super neat!
Thanks js!
Quote from: jkokura on February 09, 2013, 04:33:21 PM
I like that new board a lot. Well done sir!
Jacob
indeed, i was impressed with the new pcb layout. I just love it when a plan comes together. 8)
Cool build!
I hear Juansolo's Demo of the Chunk Chunk with this transistor biasing method...
Mmmmm I must give it a try, mine sounds a little bit fake!
That's great Keefe, glad you like the sound of it with the alternative biasing and transistor choices.
We could probably do with an etched plate soon, it will save me a lot of painting on a huge Hurricane Sandy rebuild.
Clean wiring, awesome knobs. ;D
Quote from: njkke on February 09, 2013, 06:12:53 PM
Cool build!
I hear Juansolo's Demo of the Chunk Chunk with this transistor biasing method...
Mmmmm I must give it a try, mine sounds a little bit fake!
I never tried biasing all mine to 4.5v so I can't give a comparison but I think this one sounds pretty good. That's all I can say. :)
Quote from: marauder on February 09, 2013, 07:40:42 PM
That's great Keefe, glad you like the sound of it with the alternative biasing and transistor choices.
We could probably do with an etched plate soon, it will save me a lot of painting on a huge Hurricane Sandy rebuild.
sounds good to me!
Quote from: eldanko on February 09, 2013, 09:23:22 PM
Clean wiring, awesome knobs. ;D
Thanks Dane 8)
Nice build Hab... looking really slick with that etched faceplate :)
Thanks Haberdasher for the explanation of the biasing you used. I'll have to try it out on mine when I get it finished.
Very clean! Looks great!
Really great as always, love the two big knobs. Makes for a nice combination of oscilloscope and Mesa.
Looking good!
On the new 2013 chunk there are 2 1nf caps listed (C6 and C11). which one should be replaced with the 10n to reduce high end fizz?
Thanks
Quote from: pryde on February 13, 2013, 02:29:53 PM
On the new 2013 chunk there are 2 1nf caps listed (C6 and C11). which one should be replaced with the 10n to reduce high end fizz?
Thanks
Oh, you're right. It's c11, the one off of t3. It was c16 on the older version.
Quote from: Haberdasher on February 13, 2013, 03:06:19 PM
Quote from: pryde on February 13, 2013, 02:29:53 PM
On the new 2013 chunk there are 2 1nf caps listed (C6 and C11). which one should be replaced with the 10n to reduce high end fizz?
Thanks
Oh, you're right. It's c11, the one off of t3. It was c16 on the older version.
Muchas Gracias. Gonna whip up a fet matcher vero and get started.