Monday, 26 August 2013

Ibanez OD855 Overdrive II

Now. This is per the factory schematic, so it should (finally) be ok - don't go looking for the old defunct layout, as it is gone for good. Transistors are used for buffers, so i swapped the pinouts for your everyday devices. Tone pot is G-tapered 20K in the original, but linear should work fine in its place. Turned out pretty neat and still quite compact.

Thanks to Norwichbadger - this one is now verified.



Posted by at 20:56
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18 comments:

  1. Harold26 August 2013 at 21:20

    It says OD885 on the image ...

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  2. Travis26 August 2013 at 22:42

    That is a beautiful layout! Very impressive!

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  3. Unknown27 August 2013 at 08:48

    1N60's... Interesting... That's what I have been planning to use to build my dirt box, for which you have recently posted a layout.
    Definitely confirms my choice! :)
    Thanks

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  4. MH28 August 2013 at 09:55

    This is nice. I just finished building it and my build actually sounds like a overdrive not fuzz type pedal at all. Need to try different transistors and diodes.

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    Replies
    1. mirosol28 August 2013 at 10:21

      Well it is an overdrive.

      Transistor types won't affect the sound that much as those are only buffers (unity amplifiers, which are used to decouple the circuit parts from other effects/amps/etc).

      What diodes did you use?
      +m

      Delete
  5. MH28 August 2013 at 11:21

    I tested it with 1N60, bat41, 1N4448. 1N914 if i remember correctly. Trannies didn't do a thing just like you said.

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  6. MH28 August 2013 at 14:45

    Yep.

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  7. Unknown30 September 2013 at 17:17

    I am having problems with this build, the 1uf, is that a regular capacitor, or is it different from the other ones on the schematic? If it is different, what is the difference? And will it cause a problem? Because I get a clean sound, but when I switch to distortion there is no sound, I've checked everything and that's the only thing that is not right.

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  8. Norwichbadger13 October 2013 at 22:09

    This layout won't work as it is. I tried it and got no signal at the output. I "probed" it and lost a weak signal completely at the diodes. Without the diodes you get something - which is what MH probably heard - but its pretty horrid! The VR was about 3.5v so I looked at the schematic and I think that the problems are: Level one is attached to VR instead of Ground and the base of Q2 has no bias. It needs a 510k resistor from row 4 column 15 to row 8 column 15 (VR row). Move level 1 either to an off board earth point or say row 7 column 13 which is what I did. To facilitate this I scrapped D3 and wired the +9v to row 3 column 17 and this gave me space to put in the 510k. Incidently I took that 510k from row 3 column 5 and used it for Q2 bias because its not used on the schematic and all its doing here is acting as a low value anti-pop resistor . If you want one I'd put a 1 meg in which we all probably have more of than 510k's!
    The effect works fine now. I could not find any In60 (germanium) diodes anywhere but I guess that OA91 (what I used ) or IN270 etc will be fine. I suspect that IN60P are silicon schottky diodes which are similar in performance to germanium. Forgive me if I'm wrong about that its just that the reverse resistance of an IN60P is over the 2 meg of my meter whereas any germy I've ever measured is way lower than that. Anyway the IN60P sound ok if a bit brittle but with the germaniums it sounds really good. Not exactly BSIAB but headed in that direction if you know what I mean!
    As to the 1uf you need unpolarised ones either polycap or mulilayer ceramic. I used polys.

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  9. Norwichbadger13 October 2013 at 22:56

    Me again. I've just realised that the collectors of Q1 and Q2 should probably also both be connected to VR rather than the 9v. It may make no difference since they are both emitter folowers but since I can't figure out how to easily bodge that I will leave that decision to Miro!

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    Replies
    1. mirosol14 October 2013 at 12:12

      Fixed. The missing 510K and level 1 to virtual ground were my mistakes. However, i've never seen emitter follwer buffer been fed with vref instead of supply voltage.
      According to factory schematic, the collectors are definitely getting supply voltage...
      http://elektrotanya.com/PREVIEWS/63463243/23432455/ibanez/ibanez_od855_sch.pdf_1.png
      +m

      Delete
    2. Norwichbadger14 October 2013 at 15:43

      Crumbs that was quick! I had the same schematic. I only had second thoughts about VR for the collectors because on the schema the 510k Q1 base resistor and its collector both have the same upwards arrow rather than one with VR and the other + 9v and your layout had that base resistor go to VR so I thought I would double check with you, but it certainly works well with the collectors to +9v.
      Thanks once again. I just don't know how you get your head around these vero solutions so quickly. Switching that d3 around like that! Either you are a genius or I'm just thick; probably a bit of both....

      Delete
    3. mirosol14 October 2013 at 16:51

      Nah.. I just wish i didn't make as much mistakes as i do...

      In theory that circuit should have worked with vref acting as virtual ground, but i've seen couple of other incidents where it doesn't - so this one pretty much validates my suspicion that vref virtual ground doesn't act the same way as your standard ground.

      Did you apply the corrections to your board? Should this be (finally) tagged?

      On a side note - i would personally go with 1N60Ps for numerous reasons :)
      +m

      Delete
    4. Norwichbadger15 October 2013 at 12:27

      The best way to avoid mistakes is to do no work!
      I have applied all the corrections as per the revised layout and it works just like my bodged version. So I would say it should be tagged as verified.

      Delete
    5. mirosol15 October 2013 at 12:52

      Haha.. I always feel like "no i won't post a single layout anymore" when someone finds an error on my layout. That usually lasts a day at most.

      I'm tagging this right away.

      If you want a challenge, take a look at:
      http://tagboardeffects.blogspot.fi/2013/03/pearl-od-5-overdrive.html
      That's been unverified for a long time with one comment stating "doesn't work". So eyes on the topopiccione schematic would be a good idea... Won't build it myself as i have the original and don't think anyone would buy a clone off from me... Nice OD in general though.
      +m

      Delete
    6. Norwichbadger15 October 2013 at 21:35

      This comment has been removed by the author.

      Delete
    7. Norwichbadger15 October 2013 at 21:44

      I have not got the bits for the Pearl but when I next order some I'll give it a go. The only thing I can see first off is that with the 1n4001 in series with the +9v the 1v drop might mean with a 9v supply that the zener D4 always has a high reverse resistance that would make the VB a bit higher than half voltage - which might not be crucial but if I was Onthetundra I would jumper 1N4001 D3 or replace the zener D4 with a 3.3k and see if it does make a difference.

      Delete

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