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.

Monday, January 12, 2015

Ripthorn FET-2B Bass Preamp

DIYStompboxes forum member Ripthorn adapted the Alembic F-2B tube preamp to a JFET preamp. It gives you 3-band EQ controls, master volume, and a bright switch. Fairly simple circuit, but might turn into a bit of a rats nest with the offboard wiring (I know, a bit out of character for me). Set the trimmers to about 4.5-5v and then adjust from there to taste.


23 comments:

  1. I've built your layout. I've only scaled down the tone stack for less noise. It works well, it sounds pretty good. The only drawback is this hiss/crackle that is always present.

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  2. I just built this too! I have no crackle, on the contrary, it's one of the cleanest pedals I've built. I ended up having different values for the "treble caps", which is probably why the pot doesn't have much effect when I turn it.
    Sounds killer!

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  3. A B500k pot is a good reemplacement for volume pot? Thanks!

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  4. I did not understand the connection of the pots... help :) thonecezar@gmail.com

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  5. I just noticed this project. I designed this a long time ago and thought it had long since gone the way of the buffalo. Great layout, so much better than the nasty thing I put together originally. I may have to build this with the updated layout, as I have always liked it.

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    1. Follow up question, do you have any Gerber or Eagle files for your layouts? I'm wanting to try my hand at milling my PCB for this instead of etching, but the only software I'm familiar with for PCB CAM requires something other than PDF. Thanks!

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    2. Oh cool! I don't have gerbers for most of the layouts as they're created in DIYLC, which doesn't have the gerber output. Most of the layouts I've done in Eagle I've uploaded to OshPark and you can download the gerbers from there I believe. Link at the top of the page.

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    3. I just did up a project page for this over at my website that has the schematic and links to board files, build documents, etc. As I stated, this was my first "design", so it's pretty basic, but hopefully you'll find everything you need there. I also have many other projects there that are pretty fun that you can check out as well. https://scientificguitarist.wixsite.com/home/fet-2b

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  6. Please keep the eye roll to a minimum with my noob question. Lol. Are the 2 blue 100k squares at the top what you are calling trimmers? I’ve built a few pedals and only seen these a handful of times and always steered away from pedals that have them because I’m in sure of what they are.

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    1. You are correct! They're there to more easily bias the transistors. Adjust them till you have 4.5v on the drains of the JFETs, and then fine tune by ear.

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  7. Hai, I'm interested to build this pre amp, can you give me tutorial how to measure bias?

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    1. With a digital multi meter measure the voltage on the drain of each JFET and adjust the trimmers till 4.5v is reached. Then adjust by ear if necessary.

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  8. i was confused were is the pin 2 of the switch goes?

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  9. Where is PCB pdf file? Thanks.

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  10. This comment has been removed by the author.

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  11. I measured it, if is interesting i can publish image.

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  12. Can u send me PDF file please.can I built it onboard preamp?

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  13. I built this and everything is working, except that their is no noticable change when I activate the bright switch. It could just be so subtle that my ears don't hear the difference, but I think there might be an issue that I am overlooking. Anyone have any ideas as to what the issue may be?

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