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Hi there, welcome to my blog - La Revolution Deux. It's an odd name - but I like it! Here you will find all the info on my various DIY Guitar effects builds, amplifiers and guitars. Everything from a humble Ibanez tubescreamer to the holiest KLON Overdrive.

You may also find a few effects builds that I am looking to move on - usually in exchange for other effects/gear/cash. You can always check my ebay account to see what I've got up for grabs.

Have fun, enjoy the blog - Fred Briggs :-)


Feel free to get in contact with me about anything you see on this blog or with any general questions about guitars, amplifiers and effects, I'll be happy to answer! Just click the button above to email me directly or alternately my email address is fredbriggs2007 [at] googlemail [dot] com

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Thursday, 26 January 2012

OKKO - Diablo Boost+

Here's another personal favourite of mine. I just love those ridiculously sized LEDs! Anyway, the OKKO Diablo Boost + was donated to the freestompboxes forum anonymously. It's a great sounding overdrive/booster that when combined with the extra "+" knob can venture into some pretty high gain territory.

Here's a description from the OKKO website:

"The Diablo is a versatile low to medium gain overdrive with an exceptionally dynamic response. It preserves the character of your instruments and is very sensitive to your playing technique. Thanks to the effective and musical controls, the Diablo works equally well with any kind of guitar,  amp or playing style. People use it for so many different sounds, you would hardly believe that they use the same pedal.
Besides the usual Gain, Tone and Level knobs, the Diablo has some more interesting controls:
FEED affects the amount of bass in the input signal. You know the problem: an overdrive sound gets muddy rapidly if the input signal is too bass heavy (that’s why the treble booster was invented). With the FEED control you can make even the fattest neck humbucker sound clear and transparent or beef up weak pickups a little.
The BODY control takes effect on mids and compression. Another important feature is the HEADROOM SWITCH. Set to the "HI" position, an internal electronic voltage doubler is activated – the Diablo runs on 18 Volts from a regular 9 V battery or power supply. The higher voltage gives more dynamic range, more headroom and tighter bass – just try it!"

And  a demo video of the Diablo in action:

Here's a PDF of the OKKO Diablo schematic file: http://www.box.com/s/qz7r3bgncl3jzgugoe3e

As you can see if you look at the PDF schematic it compares very similarly to this, an old design by Jack Orman:

There's no doubt the Microbooster formula sounds great - there are so many pedals now using them in a cascaded structure - The Catalinbread Dirty Little Secret and Formula No 5, the OKKO Dominator and so on.

Harald Sabro (www.Sabrotone.com) has produced some brilliant verified vero layouts and posted them up on the freestompboxes forums:

Now, those veros don't include the voltage doubler that the original Diablo contains, so if you need to build one of these: 

Then all you need to add is a simple switch which will allow you to go between +9v and ~+18v...

Here's a link to the freestompboxes.org forum topic for reference: http://freestompboxes.org/viewtopic.php?f=7&t=1482


  1. When using the voltage doubler, does the Uref stay the same (4.5V) or does it go to 9V?

    1. IF you double the voltage the vref will go up to 9v as it's formed from a simple voltage divider..

  2. Does the boost stage feed into the Diablo or is in between Diablo and output?

  3. I built this one and had some trouble. First it oscillated like a sirene. Looked for mistakes, nope no mistakes. Cut the wires to minimum, stil osc. Take out the j201 in the second gainstage and put MPF102 instead. Osc. stops, but the sound of the OKKO is not as nice as on youtube (Greg Hilden!!). It sounded good but not good enough. I tried several changes with no result. Than I took out Q1,4 and 7 with the resistance and caps around them (C4,R17 and so on). Replace this with trimmers of 100K and set the bias on a drain voltage of 4,8 Volts, as done in so many fet overdrives!! And voila, Great OKKO sound!! Very Happy With It!! Conclusion: as far as I can think of is that you have to use MATCHED fets in this kind of circuits. Even on the Runoffgroove web this is not said.

    1. This comment has been removed by the author.

    2. Hey, your message interests me a lot.
      I've made a PCB of it and had some problems, the sound wasn't like on the original (I've one to compare)
      According to you, the matter is mainly from matching FET or did you found something else?

  4. This comment has been removed by the author.


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