Ibanez Overdrive II OD855 Circuit

[bloxstompboxes]

Forgive me but I am at work and can't link any schems or see any pictures. I recently built and sold an Ibanez Overdrive II OD855 pedal that was taken from the schematic in R.G.'s book and layout that I redrew myself to fit in a 125B enclosure. I believe that is the green one commonly sold on ebay. The problem is that the buyer claims it sounds nothing like the original orange one he used to have years ago. He claims the one I sold him barely makes unity. From what I could see on my phone during my break, the 'original orange' one was not the OD855 but a pedal released not much earlier and, if I remember correctly, was trasistor based rather than opamp based and also called an Overdrive II. Can someone, or R.G. if he be so kind , confirm this and provide with a link to the any online information so that I can decide what to do from this point?

Thanks,
Eric

[bloxstompboxes]

I believe I just figured this out. The orange one was actually just called the overdrive, primarily. But was otherwise known as the OD850 and was, infact, transistor based. Its circuit was actually almost identical to that of the big muff pi with some component value differences. If this is correct, then the dude is just confused and bought the wrong pedal. However, he may be right about the unity gain since I used sockets for the opamp and diodes and it's possible one or the other may have come loose in shipping. i may have to rethink that in the future.

Can anyone confirm what I just stated?

[Mark Hammer]

Yes, the 850 is essentially a Big Muff, except with the input and output buffers added that are normal requisites for use of FET electronic switching.

The 855, on the other hand, is kind of the bastard love-child of the Tube Screamer, and the Distortion+.  

• Where the TS9 puts the tone control after the clipping stage, the 855 sticks it before.
• The 855 uses a Germanium diode pair to ground for clipping, where the TS9 uses Silicon diodes in the feedback loop.
• The 855 uses the ground leg to adjust gain (like the Dist+) where the TS9 uses the feedback loop.  The former reduce low end as gain is increased, where the latter loses high end as the gain is increased.

There is moire than enough cumulative gain in the 855 to produce noticeable clipping.  But the use of germanium diodes severely limits output level, just as it does in the Distortion+.  It's certainly more than unity gain, but NOT the substantial boost in level found in the 850.

So, while I can certainly not discount the possibility of  either an error in construction, or something coming loose during transit, neither can I discount the possibility that the buyer's expectations are miscalibrated, and based on a very different pedal.

[bloxstompboxes]

Thanks Mark for the reply. I did some more reading  messaged the buyer with links from the analogman and the kitrae site backing up the info I gave him. You would be right about the germanium diodes. I don't have an 850 to compare it to though unfortunately.