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, April 4, 2016

DeadAstronaut Bassman Preamp

Here's one for my fellow bassists out there. It's a transistor-ized version of the Fender Bassman preamp as modified by DeadAstronaut over on DIYSB. It's laid out for board mounted pots and switch and will fit nicely in a 1590B.


40 comments:

  1. gracias Agustin Zanardi (p0mp0) ;)

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  2. Hey, great work on those layouts!! Just a noob question, how do you adjust the bias with the trimpots, just by ear?? Greetings from México :D

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    1. Adjust them to about 4.5v and then adjust by ear.

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  3. I bought trimmoots with 25 turns (vueltas in spanish) should be fine? How will i regulate them? Sorry for my inexperience.

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    1. You'll need to use a multimeter to check the voltage going to the drains of the JFETs. Set the trimmers to give them 4.5v and then adjust by ear.

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  4. it serves guitar? i dont find bassman pedal for guitar? sugerencies? please help me

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    1. It's designed for bass, but would also work on guitar.

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  5. Thanks for this layout. I want to build this but i'm not sure about the pots. In my country (Asia) "A" for Log pots and "B" for Linear pots. is that the same with this layout?

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  6. Hi!

    I have a nerd question, do you know the frequency range? 40hz - 10khz maybe?

    Thanks!!!

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    1. No idea there, man. That might have been discussed in the DIYSB thread tho. Link is in the description.

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  7. Will there be ok 20k or 25k pots for treble and bass? - just have no source for 22k pots

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  8. it's popping. Any resitor to cap switch will remove the pop ?

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    Replies
    1. Try a 1M resistor from the input to ground.

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  9. What fet to use on this project?
    Would 2sk170 be any good?

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    1. 2N5457 are what it's laid out for. I believe the 2SK170 has a different pinout, but may work if you twist the pins around. Use sockets.

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  10. if i change transistors for tube Can i use this pcb?

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  11. if i change transistors for tube. Can i use this pcb?

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  12. I have a problem with this pedal, the sound arrive fine until the last resistor (680k) but after that resistance the signal are very low. Why can this be happening?

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    1. Try replacing the 680k with something smaller like 330k

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  13. Thank you so much for this layout! I got a question about those two 100k trimpots. How do I adjust them properly? What is the purpose of each of them? Sorry I'm not good enough to figure it out.

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    1. They're there to bias the JFETs. Not all JFETs are created equal and while one resistor value may work for one JFET, it might not with another. Trim pots help to dial in the right amount of resistance from the voltage rail. You'll need to adjust them till you get 4.5v on the drain pins of the JFETs then adjust by ear to get them sounding right.

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    2. so drain pins should be at 4.5v above ground, right?
      Thank you so much!

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    3. Correct. Then adjust till it sounds right if necessary.

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  14. This comment has been removed by the author.

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    1. The output volume is lower than by-pass! Does anyone have the electronic diagram of this project?

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    2. Schematic should be in the link in the description.

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  15. So, I ordered some 22K pots for this one, but I got 25K delivered. Will this still work with 25K's?

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  17. its verified.. sound is good but the level of effect is a bit lower than in bypass mode.. i tried lowering the output resistor but the sound is getting a bit noisy.but but still the effect level doesnt increase.. how can i fixthis

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  18. What kind of parts is 2pcs 100k is it pot?

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  19. Hi good sound but mine got a pulsing sound in background a sort of rhythmic "pop" sound. Cannot fix it. Can u help?

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  20. Greetings group, very interesting bass sound!!!, someone has the pdf layout???, thanks.

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  21. Greetings group, someone can provide me pdf layout MXR M81, MXR M80 or similar. Nice sound !!!!!
    Thanks and success👍.

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  22. The result is very good, but the output signal is very weak. Will I have to wear a booster? Is it a design flaw? How to increase the output gain of this project?

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