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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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Wednesday, 19 March 2008

Vsex Winkle Probe: Zvex Wah Probe

Zvex: Interesting FX... The "Probe" series that he runs has been a source of mystery for many moons - until now! Thanks to the Freestompboxes forum members (~arph and others!) who disemboweled their own probe controllers and donated them to the DIY world :-)

Here's a demo video if you've never seen one in action before:

Here is the schematic of the actual "Probe" controller, you can see that it is a series of inverters driving a simple LED driver - this LED driver is used to control an optocoupler (Also called a vactrol) which is basically a LED stuck to an LDR wrapped in black tubing. The LDR section is then used to control a parameter of an FX unit...

[Note - missing capacitor value at the base of the second transistor - 22nF]

Here is the schematic of the old Colorsound Wah pedal, inductorless as you can see. Zvex uses this circuit with a few mods in his Ohh-Wah, Seek-Wah and Wah-Probe FX.

All you need to do to build a Zvex Wah-Probe work-a-like would be to build up a Probe controller using the above schematic and connect it's control vactrol LDR in the position specified in the Wah schematic below!

There you have it, a proximity controlled wah-wah pedal - absolutely useless for that "cocked-wah" sound ;-)


  1. Hi.
    I want to know value of the cap at bass of 2nd transistor.
    Please? :)

  2. Sorry, I didn't realize I'd missed that! The missing value is 22nF :-) Enjoy!

  3. thanks!!

    Change the number 8,9,10 to 13,11,12, vice-versa.

    The rest is Ok!

  4. Hey there, first of all cool project.

    I was looking on the net for somewhere to get the '4093N' IC in the probe schematic, and couldn't find it. In fact, I couldn't find much information about it at all. All I found was an italian website that said it was a quad 2x input NAND schmitt trigger. I found the 74HC132 at http://www.jaycar.com.au and was wondering is this the same sort of device?
    Much appreciated!

  5. oops, I am a silly lad, found it *shameface*.

  6. Hi,

    Thanks for posting this! I built one and it's really awesome! I was wondering what values to change in the twin T filter to change the range of the wah. The current values make the wah most pronounced on lower notes on the neck. It sounds really fat, But I'm wondering if I can get a more traditional wah sounds out of this circuit. I did try replacing the 33k resistor with a pot, but this didn't cause a big enough change to get em into the range I was looking for.

    Tanks again!

  7. Hi Everyone!
    What does it means:Change the number 8,9,10 to 13,11,12, vice-versa.
    What the difference ?
    Did someone found values of parts for making sound closer to traditional wah?
    I did my circuit, with sound like i got now - i will not change my moded CryBaby for that Hard KuaK.

  8. kinda late, but is there any reason why the circuit would get noisy as i get close to the antenna? it sounds almost like a ring modulator when close, and the noise cuts out if my hand touches it.

  9. Hi, what antenna have you used?

  10. hi, is there a vero / stripboard layout of this schematic somewhere online?

    1. I made a kind of messy layout for the proximity-control only. If you need the complete layout with the wah-circuit I can do it as well. Just let me know where you want me to send the layout-files.

    2. Did you ever get this laid out? Having an issue where the led is only acting in an "on-Off" manner when I am very close to my antenna. Tried multiple antenna sizes and can't get it to act variably. Any help would be greatly appeciated!


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