This will void your warrenty kids, although good luck getting Fulltone to respond to fixing something.
I had a v3 OCD which I found interesting as an OD. It got this darker warmer tone which I really liked and it cleans up via guitar roll off and gain down as a very good clean boost. Having lost my v3 in my various pedalboard redos. I decided to get another one. They are very resonably priced. And no doubt a quality build, quality components and box. After I got my new OCD I discovered there had been now 4 version changes to the box. The new v4 just did not float my boat. Even at lower gains in the sweet spot I used to like at 9:00 just too much dist. I wanted a true OD not another dist box.
Some guru turned me onto this easy mod which removes the fizzy high gain but keeps everything there is to love about this pedal. The FET Op-Amp design of this pedal is what gives it the touch, feel, tone and response like a tube circuit. I love that.
The v4 has a germanium diode in the putput stage which increases the gain dramatically as you turn it up. I know of few players who like its gain level and it seems the more experienced player you the less you like it.
Here is the easy mod to remove the 1N34A germanium diode:
1.) Located just above C1 and to the right of Q3 on the left edge of the board.
2.) Mine was sealed into place viz silicon goop to the surrrounding components. Clipping this free must be done w care not to damage the other circuits. DO not be concerned w sparing the germanium diode, it i sno expensive prize to cling to for "future use". I am no genius DIY tech so if I could do this anyone w basic solder experience can do it.
3.0 After locating and freeing the 1N34A diode from the goop.Take your small wire cutters and get under it clipping both pins right up next to the diode body. Leave the long oin attached to the board.
3.) After removing the diode body from the board. Bend the long oin and/or the short pin on the board to bridge the component holes on the board. Take a little quality solder and make sure the bridge is solid and contacting.
Presto a NEW OCD has been born. The 3.5 has the tone cap change of the v4 and the vol pot mod. The unit will not only have its better, and tube quality touch and feel gain even if you crank it up it will still retain a lot of gain but none of the fuzzy diode gain it used to have. At 9:00-12:00 you will find a really great sound and if you roll the gain off a great quiet clean boost. And please some have commented why not just get a Fat Boost with its FET based gain? First off the Fat Boost (which I have, v3) is NOT really an OD or a gain pedal. The 3.5 still has exponential more gain than the Fat Boost and if you A/B them, it would be hands down winner. YOu can use the Fat Boost in a stack and get some interesting tones. I have done that. I also use the ICE 9 OD w the 3.5 mod in front both set to less gain. makes for a killer Trower type darker warmer tone and they wodk very well against a tube channel or in front of other high gain boxes I have.
At any rate, the 3.5 will have you loving the OCD again. The more you evolve as a player you will find you like a less gainy drive w more tone and push to the front end of the amp. Overdrives were designed for tube amp circuits to clip them. Nothing is going to sound the same on a solid state amp. If you have a tube amp. You are going to love this mod. It keeps everything there is to love about the OCD and kills what sounds bad.
Now that being said, I am really sick of single knob "tone controls" that are not really tone controls at all but merely treble rolloff. Problem is all this began w the TS clone craze and only a few have tried to offer better and more real tone controls on the OD. The 3.5 sounds best to me gain 9-12:00 or all the way off as a clean boost. You can roll off the highs to get that warmer tone, I like mine both at 9:00 or as a clean boost you can open up the tone control to keep the high end clarity. The unit remains dead quiet even at higher voltage feeds.
Enjoy, thank me later.