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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:



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21 comments:

  1. electridiedMay 11, 2017 at 3:30 AM

    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. Effects LayoutsMay 11, 2017 at 5:06 PM

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

      Delete
  2. danMay 15, 2017 at 9:38 PM


    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. UnknownMay 17, 2017 at 4:37 PM

      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. danMay 17, 2017 at 4:50 PM

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

      Delete
  3. UnknownMay 17, 2017 at 5:07 PM

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

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  4. UnknownMay 18, 2017 at 9:01 AM

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

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  5. UnknownJune 10, 2017 at 6:42 PM

    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. UnknownJune 11, 2017 at 3:38 AM

      Forgot to say I also used an LF353 IC.

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    2. UnknownJanuary 6, 2018 at 1:41 AM

      This comment has been removed by the author.

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    3. UnknownJanuary 6, 2018 at 1:43 AM

      Hey Thomas? Did you ever do that Vero layout? I'd love to get my hands on a copy of that! Lol

      Delete
  6. DerPrJune 25, 2017 at 4:15 AM

    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. DerPrJune 25, 2017 at 5:07 AM

      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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    2. danJanuary 23, 2018 at 11:53 AM

      the pedal never remains completely silent, but if at a very low volume, calibrate ti trimpor of 1M

      Delete
  7. UnknownNovember 27, 2017 at 5:54 PM

    So, do you have to keep pressing the pedal to make it swell? Like with a momentary switch? It's a pretty neat schematic, I wonder if you could 'trick it out' with an envelope (maybe a BJT between the switch links) so it would do it automatically?

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  8. danJanuary 23, 2018 at 11:51 AM

    hello good day, I have done the pedal with the new layout and it works exactly like the magazine, you can put any JFEt as long as the pinout is respected, for Q2 and Q3 use 2n3904, THE UNIQUE PROBLEM THAT YOU HAVE TO DO NOT CALIBRATE THE 1M TRIMPOT !!!

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  9. DiegoceAugust 31, 2020 at 3:34 PM

    if i put a jumper instead of the switch, it'll works as well?

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    1. danAugust 12, 2022 at 2:51 AM

      obviusly not you need the switch to make it work jejeje

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  10. slammer88April 1, 2024 at 8:51 AM

    Is this envelope-based or has to be triggered by the switch everytime to get the effecT?

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