The overhaul mod replaces the string used by the pedal with a magnet and hall effect sensor. A microcontroller then uses the position data and a pair of optocouplers to alter the volume of the audio signal, all while retaining a pure analogue signal path. This system detects the treadle’s movement without using any mechanical parts – meaning your pedal is likelier to last a lot longer
The mod also includes a buffer, which allows for up to 14dB of gain. Zeppelin Design Labs’ Brach Siemens, designer of the VPM-1, said “The string in my Ernie Ball once broke in the middle of a show. I promised myself that night that someday I’d develop a solid-state solution – I never want that to happen again.”
As the signal path is being controlled digitally, the mod allows for five different volume taper curves: linear, two logarithmic curves, and two reverse logarithmic curves. All of these can gave custom min and max points set to any position along the treadle point.
There are also two optional upgrades: the Expression upgrade equips your VPM-1 to act as an expression control, while the Stereo upgrade can be configured for either traditional stereo mode or panning configuration.
You can build the mod from scratch from a DIY kit ($69 and some soldering), or purchase the mod assembled and ready to install into your ($120) or send in your pedal and the folks at Zeppelin will mod it for you ($165).