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.

Wednesday, May 10, 2017

Auto Swell

Someone showed me this circuit and it's a cool addition to this library. It's an old project from Electronics & Music Makers magazine and allows you to ramp up and down your volume. It's not a true-bypass pedal, but essentially an always-on boost that increases your volume when the momentary footswitch is pushed. More info and schematic can be found in these scans:



11 comments:

  1. hello, i love your work by the way. just want to ask about the sw1 and sw2 in the layout will be connecting to the 1 and 2 at the 3pdt foot switch as according to your general layout notes? thanks

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    1. No. You use a momentary footswitch and connect the 2 pins of it to the 2 switch pads on the board.

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  2. Hi again, I have used the layout and PCB of the magazine and it works perfectly, I leave a sample video I put the switch to control the effect outside as an expression pedal and that way to be able to do the pedal truebypass,the JFEt of the magazine have wrong pinout ,https://www.youtube.com/watch?v=6OQ7NaBZTco&feature=youtu.be

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    1. Hi Dan, can you say what the right pinout of the JFet should be. I am new to building pedals and if you could give the correct pinout I would be very grateful, ... thanks in advance :-)

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    2. check the dataseet http://pdf1.alldatasheet.es/datasheet-pdf/view/50800/FAIRCHILD/BF244A.html

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  3. Thanks for your prompt reply Dan, much appreciated :-)

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  4. This stomp will no longer need a whole new field or type, how about the name of Swell.

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  5. I built this on a breadboard using a 2N5457 for the jFet and BC182L transistors and it appears to work a treat. Never used an auto swell before so the switch took me ten mins to get used to. I shall definitely try building on veroboard and hopefully get it boxed up. :-)

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    1. Forgot to say I also used an LF353 IC.

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  6. hi! it work as it shoud but i think that pots must be rotated by 180 cos them working backwards. By the way i tried different q2 and q3 and speed of boost and release is realy different - 3904 and 5088 are slow, 5089 are faster and bc550 are fastest (it's what i have on hands here) and if i understand correctly you can mix them if for example you want faster boost but slowly release. And one another opinion - it's intresting idea but realisation is so-so cos you can set basic volume level only below unity and you cant change boost volume. i think that if it had some aditional booster like lpb1 after output it were more handy cos you can tweak volume levels as you want.

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    1. and one more - just tried to swap q1 and j201 (probably fake one but working) on lowest volume setting it is not complete silent and some sound bleed thru. 5457 is almost silent in that position.

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