Sunday 3 January 2021

Multivox / Big Jam SE-4 Octave Box

 A pretty cool variation of MXR Blue Box with a few extra bits and features. The only thing that is a bit unclear is the switch that selects between  one octave down, 1/2 octave down and 2 octave down. Original has a 3 position slider switch but I would like to convert to a toggle switch (3PDT on/off/on or DPDT on/on/on?) or maybe a rotary but I'm not sure how to tackle it. Layout has the switch labels per the schematic which can be found in this link:  https://music-electronics-forum.com/filedata/fetch?id=829397

*update*7mike_p found a solution for the switch. See hit comment below.



 

 



7 comments:

  1. This comment has been removed by the author.

    ReplyDelete
  2. I'm building this one - where's the ground? I'm guessing I can use W1?

    ReplyDelete
  3. Any suggestion for subbing the 3 position switch? I've got a bunch of dpdt and spdt. At least for testing purposes - if it sounds good, I'll pickup one of those 3 position.

    ReplyDelete
  4. Update - it works great. I tried it initially with 2n3904's and it just wasn't clipping well - swapped out for some 2N5088's I just got in and the distortion is nice. I dug up the schematic and my solution is to use 2 switches, it emulates the 3 modes and gives you an additional mode that still works.

    SPST: SW2 / SW3
    SPDT (ON ON): SW 5&6 / SW7 / SW8

    The 2/3 toggle feels like it adds an extra octave, I think it just connects the 2 pins on the 4013 that makes the flip flop reset to 0.

    I'll be boxing this one up. Turned out great for deciding to build it because I found a 4013 chip in the workshop at the studio and wanted to see what I could do with it.

    Thanks for the layout!

    ReplyDelete
    Replies
    1. Thanks man, great news! And I'm glad you found a solution for the switch and got an extra usable setting.
      I'll tag it.
      /
      fh

      Delete