This is a library of perfboard and single-sided PCB effect layouts for guitar and bass. I'm not an electrical engineer by any stretch of the imagination, just a DIY'er who likes drawing layouts. It is meant for the hobbyist (so commercial use of any of these layout is not allowed without permission) and as a way to give back to the online DIY community.

Tuesday, October 20, 2015

JHS MiniBomb

Here's a simple clean boost circuit built by JHS. It's really just the Tim Escobedo Duente JFET boost with a fixed resistor instead of a trimmer. Because of that you probably want to socket that resistor (5.1k) and adjust to the J201 you use. Or you can just squeeze a 25k trimmer on there like Tim designed it. Should fit in a 1590a just fine.



20 comments:

  1. Hi,
    I need to print this pcb in reverse mod?
    best wishes!

    ReplyDelete
    Replies
    1. No need to reverse it. Just print it as is. Good luck with the build!

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  2. hi pal.
    unintentionally built this one because my mate needed a booster for his recent gig, it seems more like a treble booster for me. it also has no sound when i turn the boost control to minimum position, just like a volume control.
    i have double-checked my build and everything and found nothing was wrong.
    any idea what's going on?

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    Replies
    1. Try increasing the value of that 100n cap to get less treble. Though 100n should be pretty close to having a flat response. Maybe you used a 10n? The pot will act as a volume control, so you've built it correctly.

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    2. then I have built it correctly. thanks again bro

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  3. Hi and I built it but ... having the potentiometer to the maximum just equaled the volume of true bypass, I guess having the trimmer 25K can adjust the gain and assume that change the resistance of 5.1k would be the solution, any suggestion resistance value? thanks

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    Replies
    1. Yes, you need to adjust the value of that 5.1k resistor to bias the JFET correctly. You could wire a normal sized pot in place of that resistor to bias the JFET. Then once it's sounding good, measure the resistance of the pot and replace it with a similar value resistor.

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  4. Nice!
    What would be the sweet spot in terms of voltage for the JFET?

    Cheers from Mexico

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    Replies
    1. Typically around 4.5v. I'd socket the 5.1k resistor and see what value resistor gets you close to that.

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  5. hey bro, I have a problem, in my city havent J201, can i use a similar model? what model?
    thanks!!

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  6. it works! great pedal (for the value lol)
    can i say.. i have an JHS... haha

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  7. hello i built this pedal but it works for decrease volume. I dont use reversed pcb. Iuse pcb on the picture. Thancs for answer

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  8. In what position should the pot be at when measuring drain voltage? On my SHO the voltage changes when turning the pot. Thanks for all the layouts:)

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    Replies
    1. Where the pot is shouldn't matter in this design. All the pot does in this is control the signal going to the gate of the transistor.

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  9. Pode postar a lista de materiais ?? E que n entendo muito de eletronica

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  10. Please could you pass me the subject line?, But I do not understand much of electronics

    ReplyDelete