Chunk Chunk

[Haberdasher]

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.





Sorry for the out of focus shots.  I was too lazy to drag out the tripod.
Thanks for looking.

[pickdropper]

Wow, that is clean.  Great etched plate for it as well.  Very nice overall, Keefe.

[Axe_34]

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. 

[electricstorm]

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

[Haberdasher]

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.

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. 

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.

[Haberdasher]

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

[pickdropper]

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.

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. 

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.

[pryde]

Super nice your Dudeness 

I may need to hit you up for a custom etched plate for my chunk build

[juansolo]

Super neat!

[jkokura]

I like that new board a lot. Well done sir!

Jacob

[Haberdasher]

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.

Super neat!

Thanks js!

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.

[njkke]

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!

[marauder]

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.

[eldanko]

Clean wiring, awesome knobs. 

[Haberdasher]

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.

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!

Clean wiring, awesome knobs. 

Thanks Dane