Tuesday, 27 September 2016

Electro Harmonix Octave Multiplexer

Here is a layout for a classic pedal.
I've drawn 2 versions: Vintage and Modern.
There are 2 layouts for the Vintage: with and without output boost.
I've added a boost to the Modern layout to avoid volume loss.
You can find the original FSB thread here.


  1. WOW! Alex you are unbelievable. Thanks. Man my build list is getting big. Respect!

  2. Hi Alex. Thanks for some great layout once again. I build the modern one but I have some problem, I can't make it works. I tried to check my build but I wasn't able to find errors (it's maybe on my side but I didn't find). I also tried to change IC's and trannies in case of faulty one but nothing better. Any help would be very appreciate.

    Here is my voltage :

    5457 / D 5.44 S 4.62 G 4.66

    5459 / D 3.5 S 3.5 G 0

    4013 / 1/ 5 2/ 3 3/ 0 4/ 2,5 5/ 0 6/ 2,5 7/ 0 8/ 0 9/ 8.63 10/ 0 11/ 2 12/ 8,67 13/ ABOUT 7 14/ 8,72

    LM324 / 1/3,5 2/ 3,5 3/ 3,5 4/ 8,72 5/ 3,5 6/ 3,5 7/ 3,5 8/ 4,13 9/ 3,9 10/ 3,8 11/ 0 12/ 3,9 13/ 3,9 14/ 4,1

    4558 TOP / 1/ 7,35 2/ 3,5 3/ 3,5 4/ 0 5/ 4,17 6/ 3,5 7/ 2,3 8/ 8,73

    4558 BOTTOM / 1/ 1,5 2/ 3,5 3/ 3,5 4/ 0 5/ 3,8 6/ 3,6 7/ 2,6 8/ 8,72

    To finish, pics of my build :


    Thanks a lot for all your work

    1. Hi Thomas.
      Did you compare the layout to the schematic?
      I think it's ok but I won't be able to check again until Monday.
      I'm not able to see all the cuts from the pictures but I assume you already double checked everything.
      From your circuit picture, I think both transistors are reversed. Have you checked the pinout?

  3. Thanks for the comment. I checked cut and pinout..
    I placed the tranies by respecting letters but I tried to reverse them without success.
    I tried to look at the schematic also but I don't hAve the knowledge to understand. I just know building.

    1. Hi Thomas!
      Had a look again and there were a couple of mistakes:
      from the 2n5457 Ground there is a 1M resistor that should go to ground, one row below (it goes to Vref on the previous layout).
      The 100n cap at the bottom right corner should be removed.
      I've already changed the layout.

  4. OK, thank you I will test that and keep you updated. You were right on my pics trannies were reversed. I remove them to test them and put them back quickly (and badly to make the test).
    Not sure to have the time tonight but tomorrow it should be good.

  5. OK I made the change and.... it's working. The modern version is verified. Thanks a lot for giving us another great layout).

    1. Cool! Thanks Thomas!
      Does it sound like the original?
      Is the JFet boost helping with volume loss?

  6. It sounds very nice. I don't really know the original but from what I heard on the web it's close, maybe a bit more artefact (not on every setting).
    The boost help a lot, you can even have a volume boost so it's perfect.
    Thanks again for your work and the help you gave me.

  7. IMO it's a bit misleading to talk about "volume loss". I own the reissue and modern XO version, plus a former bandmate has a vintage specimen. None of those have volume drop issues. Like johnk says in the FSB thread: "I found that it could use a bit more output so I added a Jfet boost to the output with a volume control". Boost afterwards isn't a bad thing and adds to usability. But nevertheless, the original is an octave pedal and always performs at unity level, no matter the source instrument. Adding a JFET stage and volume control are extra features that are not essential.

    1. My bad.
      Drawn the layout a while back and forgo why the boost was there.
      Glad it work though.

    2. Damn i sound mean :) That was not the intention.

      I'll be building one soon(ish) too. And super great work man!

    3. You are a mean! :)
      Don't worry.
      At least now people know the Vintage version without the boost should still work without any problem.

  8. Verified the vintage with the boost. Sounds close to the YT vid but doesn't seem to track quite the same. Mind you those vids on YT make everything sound amazing.

    1. Thanks Gavin!
      Which video have you watched?
      The ProGuitarShop's above the layouts?

    2. PGS videos always sound perfect (different from reality).
      You should check some videos of the "Vintage" version.
      Don't know if they've been modified later for tracking issues.

  9. hi alex..im so confused about number of the switch, any switch pinout images for this...im newbee..sorry for my bad english.... thanks

    1. Hi Agus.
      "Regular" Switches are always numbered the same on this blog:


      1 4
      2 5
      3 6


      1 4 7
      2 5 8
      3 6 9

      You can check Storyboardist page here:

    2. oke,thankyou very much for suggest... i will try it....