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Wednesday, September 2, 2015

Shin Ei OB-28 Octave Box

Here's a weird one for you–the Shin Ei Octave Box. It's apparently an all analog clean octave down effect. I'm not going to pretend to understand how it works, but there are a lot of transistors. Originals used 2SC644 and 2SC666 transistors, which I think were in the massive TO-3 package. I've drawn the layout for more modern replacements, BC547s and a BC557. Other transistors like the 2N3904/06 or 2N5088/87 would probably work as well. Socket and experiment with what you have on hand.



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21 comments:

  1. AnonymousSeptember 2, 2015 at 4:37 PM

    Can you make a layout of the switches' wiring? It will be very useful

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    1. UnknownSeptember 3, 2015 at 7:54 AM

      Check out this link: http://www.learningaboutelectronics.com/images/DPDT-toggle-switch-diagram.png

      There will be two different DPDT switches on this layout. SwA is one, SwB is the other.

      Follow the numbering as stated in that link. :)

      Delete
  2. CharlsRTSeptember 2, 2015 at 8:18 PM

    Thanks you very much my friend, i have a question, the diode 1, 2 & 3 is a germanium, silicon,?

    Thanks :)

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    1. UnknownSeptember 3, 2015 at 7:52 AM

      Hey Carlos! The schematic I found for a similar circuit is here - http://topopiccione.atspace.com/pjimages/ShinEiOctave.sch.jpg

      It calls for SH-1 diodes.

      Delete
    2. UnknownSeptember 3, 2015 at 7:53 AM

      Also read this, it has some interesting info about matching Q9 and Q10:

      http://topopiccione.atspace.com/PJ15ShinEiOctave.html

      Delete
    3. dtgehringSeptember 3, 2015 at 9:26 AM

      SH-1 will probably be pretty hard to source. They were just silicon rectifier diodes though, so 1N4001s or similar will probably work fine.

      Delete
  3. Alex VolskyAugust 27, 2016 at 7:21 AM

    Hi, I found bc547 and 557 with letters A, B and C (bc547A, bc557B and so on...). That defines different hfe. So does it matter to choose BCs with hfe close to original 2SCs or with same letters?

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    1. Effects LayoutsAugust 27, 2016 at 9:50 AM

      Those letters refer to the Hfe ranges. A is lower gain than B, B lower than C. You'll have to compare datasheets to find which is the best replacement. But I would guess B or C will work fine.

      Delete
    2. 08escxAugust 3, 2023 at 7:34 AM

      https://www.parasitstudio.se/u235.html I made this pedal, but there is distortion in the sound cut and some noise. What is the problem?

      Delete
  4. Alex VolskyOctober 21, 2016 at 12:45 PM

    Hi again, is it right wiring? https://drive.google.com/file/d/0B-yOZ9M95dxrV1ZkTnRYRXRsZTA/view?usp=sharing

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    1. Alex VolskyOctober 23, 2016 at 8:00 AM

      It just doesn't work wiring like that, and i have no idea, what is wrong

      Delete
    2. Effects LayoutsOctober 25, 2016 at 12:09 PM

      It looks like you've got it right. Here's the original schematic I laid this out from.

      http://www.tremolo.pl/Efekty/Octaver/Octave%20Box.gif

      Have you tried using an audio probe on it?

      http://www.diystompboxes.com/pedals/debug.html

      Delete
  5. Alex VolskyOctober 25, 2016 at 9:09 AM

    Need your help, really

    ReplyDelete
  6. Alex VolskyOctober 27, 2016 at 7:05 AM

    Ok, i found one my idiot mistake - I soldered the 100n capacitor intead of 2,2k resistor.
    After replacement bypass mode started to work, but when i turn on the switch A, istead of notes i hear only indistinct clicks, swB just increses hum a little and alone makes even no clicks, how with swA; turning swB off to bypass (when only B turned on) makes a not quiet click.
    Checking the cucuit with audio probe (main effect part), the blue point and all the signal way before produces any kind of fuzz, but then, after 100k resistor (red point and line), isntead of notes are heard clicks like when swA is on.
    Also capasitors marked yellou are 6,8uf, but your layout has them 6,8nf - is it a mistake?
    https://drive.google.com/file/d/0B-yOZ9M95dxrSzB1eFMydmlkNWM/view?usp=sharing

    ReplyDelete
    Replies
    1. Effects LayoutsOctober 27, 2016 at 9:26 AM

      That would probably be a mistake on my part. Try replacing those caps and see if it fires up.

      Delete
    2. Effects LayoutsOctober 27, 2016 at 9:30 AM

      I found another schematic that has all those 6.8 caps as uF, not nF. So go ahead and try replacing 3 6.8nF caps in the layout with 6.8uF caps.

      Delete
  7. Alex VolskyOctober 28, 2016 at 9:19 AM

    Replaced 6.8 caps with sockets, tried different combinations - even no clicks became heard, only q1's and q6's collectors give a voice. Most schematics, including factory, have 6,8s all in nF. I have even no idea, what's wrong...

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  8. UnknownJanuary 20, 2019 at 6:52 PM

    is this verified?

    ReplyDelete
  9. Slowpoke101April 13, 2020 at 4:51 PM

    I bread-boarded the circuit. Used 6n8 (6.8nF) capacitors - the 6u8 is a misprint. Diodes used were 1N4148. The circuit works but I have not made the PCB yet. From your google-drive I used your wiring diagram but I found one problem. There is supposed to be a wire link on SwB linking terminals 2 and 4.

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    1. Slowpoke101July 29, 2020 at 5:52 PM

      There is an error with both the perf and PCB versions. A 100K resistor that should be connected between Q9 collector and Q10 base is missing. The effect works correctly when a 100K resistor is installed and a wire link between terminals 2 and 4 of SwB is also installed.

      Delete
  10. Nicholas BosApril 3, 2024 at 11:55 PM

    I built the layout but sadly couldn't verify it. Used 2n2222 and 2N3906

    ReplyDelete