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…
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 😉