Pages

▼

Wednesday, November 9, 2016

Mad Professor Forest Green Compressor

Got a request for this one. It's very similar to Bjorn's Pale Green Compressor in his BearFoot Fx line, but with an extra stage for the Sustain mode. Here's the schematic for reference. From the product description:

FOREST GREEN COMPRESSOR (FGC) is designed to meet the highest standards of guitar and bass compression.  There is extremely low noise throughout the range and a high overload margin, which allows also a wide dynamic input range at minimum distortion and noise.  FGC is equipped with a special tone control to fine-tune the compressed sound for most transparent tone and effect.  The pedal has a switchable compressor and sustainer mode.  In Sustain mode you can get a very dynamic, touch sensitive tone with a long sustain. Here the attack is not lost, making the pedal suit-able even for blues players and works great with slide playing.


I've made 2 versions of the layout, one with SGD pinout for the 2SK170, and another with the more common GSD pinout for other JFETs (J201, 2N5457, etc)


at

28 comments:

  1. AcikaNovember 9, 2016 at 9:28 AM

    Bravo! Thanks a lot

    ReplyDelete
  2. UnknownNovember 9, 2016 at 11:42 AM

    substitute for ci and transistors? Thanks a lot!

    ReplyDelete
    Replies
    1. Effects LayoutsNovember 10, 2016 at 7:52 AM

      You can try some other JFETs for the 2SK170 (mind the pinout). For the other transistors, high gain NPN silicons for the BC550Cs (2N5089, MPSA18, etc) and a high gain PNP silicon for the BC560C (like 2N5087). As always, Google is your friend.

      Delete
    2. shimanekoNovember 11, 2016 at 12:11 AM

      Hello. Is pinout of 2sk170 correct?I think Gate is center in this FET.

      Delete
  3. wainer.said@gmail.comNovember 9, 2016 at 2:48 PM

    Which equivalent to the CI AD797

    ReplyDelete
    Replies
    1. Effects LayoutsNovember 10, 2016 at 7:48 AM

      Socket and experiment with any higher end single op amps you can find–NE5534 is where I'd start.

      Delete
  4. UnknownNovember 10, 2016 at 1:02 AM

    I have seen these... ( https://www.aliexpress.com/store/product/Single-OP-Amp-W-Discrete-Components-To-Replace-AD797-LME49710-OPA627-NE5534-LME49990-Free-Shipping/802369_32374567307.html ) which supposedly can replace these expensive chips... ANyone have a comment on this?

    ReplyDelete
    Replies
    1. Effects LayoutsNovember 10, 2016 at 7:46 AM

      Not sure I would use one of those contraptions. Probably just use a higher end single op amp like a NE5534. You could even try using a TL071.

      Delete
  5. shimanekoNovember 10, 2016 at 3:06 AM

    Hi! Thank you again for the great layout. Which Vactol do you suggest? VTL5C6 on Pale Green Comp?

    ReplyDelete
    Replies
    1. Effects LayoutsNovember 10, 2016 at 7:47 AM

      Originals use an LED and LDR in a heat shrink tube, so not exactly sure which VTL5 to recommend. But this circuit is similar to the Pale Green Comp, so if the VTL5C6 works there I would think it would work on this.

      Delete
  6. BoyetNovember 11, 2016 at 11:15 AM

    Is the pinout of 2sk170 correct on this layout? Gate is in the mddle of this tranny. I'd tried twisting the pinout but i only get a humming sound.

    ReplyDelete
  7. Effects LayoutsNovember 14, 2016 at 7:30 AM

    Yeah I think you're right. Guess I got stuck in 2N5457/J201 pinout mode. I'll update the layout.

    ReplyDelete
  8. f0m3November 20, 2016 at 2:47 PM

    I'm always confused by those LED/LDR couplers. What specs should i look for? I already build a tremulus lune and an easyvibe (both with LED/LDR) and they seem to work fine but that could just have been luck :). Does anybody know what to look for?

    ReplyDelete
  9. shimanekoDecember 4, 2016 at 9:07 AM

    Hi. I built this one, but have some problems. I get some compressed sound, but all the pots do not work. I will try another combo of LDR/LED, but am wondering why volume and tone do not work. As long as I traced the layout to the schematic, did not find any error.
    Does anyone have an idea for that?

    ReplyDelete
    Replies
    1. shimanekoDecember 6, 2016 at 6:25 AM

      Hello. I would think, in the schematic, output from pin6 goes to lug3 of volume via 1uFcap and 5k6 resistor, but in the layout it does not.
      And in the schematic, Vc from 78L05 goes to +side of LED, which makes LED always on.It set me wondering if a LED/LDR combo works properly.

      Delete
    2. Effects LayoutsDecember 6, 2016 at 3:24 PM

      Thanks for finding that error. The layouts have been fixed and should be correct now. Since it's an optical compressor I believe the LED needs to always be on a little. But the amount of resistance from the LED to ground varies based on signal being processed by the circuit. So I think that part of the schematic is fine.

      Delete
    3. shimanekoDecember 8, 2016 at 10:11 PM

      Thank you for a quick fix! It seems that only PCB layout is fixed.
      I also think the 1uf cap, between the opamp pin6 and comp3,should be moved to right before 5k6 on the way to Vol3. Am I correct? It's my first experience to read a schematic, and have found it is a fun and tough job!

      Delete
    4. UnknownFebruary 6, 2017 at 4:43 PM

      Вы правы! Должно быть соединено.

      Delete
  10. Ian RiderApril 28, 2018 at 9:26 AM

    Does anybody verified this circuit? I built it and it has so much distortion when COMP po is about 50% or more. What's more it starts to work about 10s. after i plug 9V into DC socket...

    ReplyDelete
  11. AnonymousSeptember 4, 2018 at 4:04 PM

    just done.
    This layouts are incorrect, watch schematic first! Mistakes after opamp pin6: have your attention at compression and tone circuits, 1 uF cap polarity issue.
    LDR was replaced to Optocoupler Silonex NSL-32 (color dot on diode side is minus). When use NE5534AP, you must downgrade input values. Thanks. From Russia with love.

    ReplyDelete
    Replies
    1. alex45June 7, 2019 at 3:21 PM

      Could you be more specific please

      Delete
    2. alex45June 7, 2019 at 3:23 PM

      When use NE5534AP, you must downgrade input values. Thanks. From Russia with love.

      Sorry could you be more specific in what are the values to change. sorry for my english

      Delete
  12. AnonymousSeptember 7, 2018 at 6:57 PM

    http://i.piccy.info/i9/e27efa092000893121a61d3b8c176c07/1536360947/911276/1268085/zzzzz.jpg

    ReplyDelete
  13. kjhMarch 17, 2021 at 11:33 AM

    Sorry about my ignorance but... Where do I connect the status LED?

    ReplyDelete
    Replies
    1. Effects LayoutsMarch 17, 2021 at 11:40 AM

      Check out the General Layout Notes tab for offboard wiring.

      Delete
    2. kjhMarch 17, 2021 at 12:23 PM

      Ahh ok, I just thought the general switch was SPST sorry, the SPST is for the sustainer.
      This is my third pedal out of your website (I did VH4 and tubescreamer808 before) and I must say thank you. Your site is super cool.

      Delete
  14. cristianmonsalve15September 30, 2022 at 1:51 PM

    Hola, cabe en una caja 1590b?

    ReplyDelete
  15. cristianmonsalve15October 1, 2022 at 4:52 AM

    Hola, cabe en 1590b?

    ReplyDelete