Welcome to the Revolution

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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Saturday, 11 February 2012

Keeley - Katana Boost

The Keeley Katana has been a popular boost pedal since it was introduced. It's circuit topology is simple yet it manages to produce everything from a small boost to add a bit of life to leads right through being able to smash the front of a tube amp into submission and natural break up. Here's the description from the Keeley website:

"As far as guitar clean boosts go, the Katana is KING TONE. It's the pedal to have for the finishing touch on your tone.

Want a mirror image of your tone, only louder? This is it. The Katana is also a fat, harmonically rich boost, just pull out on the volume knob and stretch your imagination with overdriven tone! You can keep it on all the time to push your amp harder, or as an occasional boost to cut through the mix.

Obsessed or Compelled with the Fattest, Fullest Drive? Well, Before other people started using Blue LED's and non-diode clipping stages, there was the TMB and Katana.... Cascading FET stages do the tube-amp-thing like nothing else!"

And here's a video of the Katana in action:

And here's the schematic redrawn for you:

And a nice PCB Layout by RYANUK: http://www.box.com/s/zqpak9putdef8up82m51

The dual cascaded Jfet stages do sound good, the charge pump ups the voltage to 18v and gives the circuit double the gain of a similar circuit running at 9v. It does introduce it's own clipping when the 10uF cap is switched into bypass the source resistor on the first stage, I prefer the tone without the cap switched in, a possible mod would be to use a smaller cap here to introduce some treble/mid boost to the tone. I also suggest changing the 4k7 resistors for 10k trim pots to allow you to tune each jfet to it's optimal bia's point around about 1/2 V (9v in this case). Build one up, they sound pretty decent for such an easy build!

Here's the Freestompboxes.org forum topic for reference: http://freestompboxes.org/viewtopic.php?f=7&t=2946


  1. Hey, nice post. Are there any PCBs for sale anywhere?

  2. Hello many thanks for the post..I want to build this so please check out the schematics- the IN capacitor doesn't have value and also the parts are not numerated so beginners like me can not figure it out where to put what :) Please be so kind to make this corrections. Greetings from Macedonia

    1. What you read as "In" is actually a 1n capacitor. That means 1 nF or 1 nanoFarad or 1000 pF.

  3. Would using a 1N5818 instead of the 1N5817 affect this build at all?

  4. Hello, can I ask how the on-pot capacitors introduce clipping in the circuit? What's their role in clipping the signal?

  5. In order to bias the JFET where to I set my multimeter probes to test for 9V?


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